WO2015124570A1

WO2015124570A1 - Methods and pharmaceutical composition for the treatment of influenza a virus infection

Info

Publication number: WO2015124570A1
Application number: PCT/EP2015/053318
Authority: WO
Inventors: Béatrice Riteau; Martine Jandrot-Perrus; Ba Vuong LE
Original assignee: INSERM (Institut National de la Santé et de la Recherche Médicale); Institut National De La Recherche Agronomique (Inra); Université Claude Bernard - Lyon 1; Université Paris Xiii Paris-Nord; Université Paris Diderot - Paris 7
Priority date: 2014-02-18
Filing date: 2015-02-17
Publication date: 2015-08-27

Abstract

The present invention relates to methods and pharmaceutical compositions for the treatment of influenza A virus infection. In particular, the present invention relates to a method for the treatment of influenza A virus (IAV) infection in a subject in need thereof comprising administering the subject with a therapeutically effective amount of at least one anti-platelet agent.

Description

METHODS AND PHARMACEUTICAL COMPOSITION FOR THE TREATMENT

OF INFLUENZA A VIRUS INFECTION

FIELD OF THE INVENTION:

The present invention relates to methods and pharmaceutical compositions for the treatment of influenza A virus infection.

BACKGROUND OF THE INVENTION:

Influenza is one of the most common infectious diseases in humans, occurring as seasonal epidemic and sporadic pandemic outbreaks. Annually, influenza A viruses (IAV) cause 3-5 million clinical infections and 200,000-500,000 fatal cases. Thus, those viruses are of great concern to human health. The continuous sporadic infections of humans with highly pathogenic avian H5N1 strains and the recent infections caused by newly emerged H7N9 viruses highlight the permanent threat caused by these viruses (Chen et al, 2013; Watanabe et al, 2013; Webby and Webster, 2003).

The pathogenesis of influenza is a complex process involving both viral determinants and the immune system (Foucault et al, 201 1; Fukuyama and Kawaoka, 2011; Kuiken et al, 2012). During severe influenza, dysregulation of cytokine production contributes to collateral damages of the lungs, possibly leading to organ failure and death (Cheung et al, 2002; La Gruta et al, 2007). A deleterious pulmonary inflammation is typically observed during infection with highly pathogenic IAV subtypes (de Jong et al, 2006; Kobasa et al, 2007). In these circumstances, the endothelium, which line the interior surface of blood vessels is proposed as to orchestrate the crescendo in cytokine accumulation, although all the actors playing this piece are not identified (Teijaro et al., 2011).

Upon endothelium injury, platelets are immediately recruited by inflamed endothelial cells in the absence of denudation via the release from Weibel Palade bodies of P-selectin and high molecular weight von Willebrand factor and platelet glycoprotein lb. When injury is more severe, platelets adhere and are activated by subendothelial proteins (Rumbaut and Thiagarajan, 2010). Simultaneously, Protease- Activated Receptor (PARs) mediates activation of platelets by thrombin. These events lead to the conformational change of the platelet glycoprotein Ilb/IIIa (GPIIb/IIIa) receptor for fibrinogen that bridges platelets leading to their aggregation and reinforcement of activation. Importantly, platelet activation is strongly associated with enhanced inflammatory responses. Activated platelets release potent inflammatory molecules and play a key role in leukocyte recruitment (Duerschmied et al, 2013). Platelet activation is finely tuned but its dysfunction is pathogenic and contributes to inflammatory disorders (Cohen, 2002; Degen et al, 2007; Medcalf, 2007). Thus, uncontrolled platelet activation could contribute to the pathogenesis of IAV infections by feeding a harmful inflammatory response in the respiratory tract. However, at present the role of platelets in the context of IAV infection has never been investigated.

SUMMARY OF THE INVENTION:

The present invention relates to methods and pharmaceutical compositions for the treatment of influenza A virus infection. In particular, the present invention is defined by the claims.

DETAILED DESCRIPTION OF THE INVENTION:

The hallmark of severe influenza virus infections is excessive inflammation of the lungs. Platelets are activated during influenza, but their role in influenza virus pathogenesis and inflammatory responses is unknown. The inventors used targeted gene deletion approaches and pharmacological interventions to investigate the role of platelets during influenza virus infection in mice. Lungs of infected mice were massively infiltrated by aggregates of activated platelets. Platelet activation promoted IAV pathogenesis. Activating protease-activated receptor 4 (PAR4), a platelet receptor for thrombin that is crucial for platelet activation, exacerbated influenza-induced acute lung injury and death. In contrast, deficiency in the major platelet receptor glycoprotein Ilia (GPIIIa) protected mice from death caused by influenza viruses, and treating the mice with a specific GPIIbllla antagonist, eptifibatide, had the same effect. Interestingly, mice treated with other anti-platelet compounds (antagonists of PAR4, MRS 2179, and clopidogrel) were also protected from severe lung injury and lethal infections induced by several influenza strains. The intricate relationship between hemostasis and inflammation has major consequences in influenza virus pathogenesis, and anti-platelet drugs might be explored to develop new anti-inflammatory treatment against influenza virus infections.

Accordingly an object of the present invention relates to a method for the treatment of influenza A virus (IAV) infection in a subject in need thereof comprising administering the subject with a therapeutically effective amount of at least one anti-platelet agent. As used herein, the term "influenza A virus infection" or "IAV infection" has its general meaning in the art and refers to the disease caused by an infection with an influenza A virus. In some embodiments of the invention, IAV infection is caused by influenza virus A that is HIM, H2N2, H3N2 or H5N1.

The subject can be human or any other animal (e.g., birds and mammals) susceptible to influenza infection (e.g. domestic animals such as cats and dogs; livestock and farm animals such as horses, cows, pigs, chickens, etc.). Typically said subject is a mammal including a non-primate (e.g., a camel, donkey, zebra, cow, pig, horse, goat, sheep, cat, dog, rat, and mouse) and a primate (e.g., a monkey, chimpanzee, and a human). In some embodiments, a subject is a non-human animal. In some embodiments, a subject is a farm animal or pet. In some embodiments, a subject is a human. In some embodiments, a subject is a human infant. In some embodiments, a subject is a human child. In some embodiments, a subject is a human adult. In some embodiments, a subject is an elderly human.

For example, therapeutic treatments include the reduction or amelioration of the progression, the reduction or amelioration of the severity and/or duration of influenza infections, and more particularly the reduction or amelioration of the inflammatory burden of the lungs (e.g. blockade of the IAV-induced inflammation), resulting from the administration of at least one anti-platelet agent of the present invention. In some embodiments, the antiplatelet agents of the present invention are used in the community setting to treat people who already have influenza so as to reduce the severity of the infection (i.e. by reduction the inflammatory burden of the lungs (e.g. blockade of the IAV-induced inflammation), reduce the number of days that they are sick and prevent fatal outcome.

In some embodiments, the anti-platelet agents of the present invention are used in a prophylactic treatment. The terms "prophylaxis" or "prophylactic use" and "prophylactic treatment" as used herein, refer to any medical or public health procedure whose purpose is to prevent, rather than treat or cure a disease. As used herein, the terms "prevent", "prevention" and "preventing" refer to the reduction in the risk of acquiring or developing a given condition, or the reduction or inhibition of the recurrence or said condition in a subject who is not ill, but who has been or may be near a subject with the disease. In particular, the antiplatelet agents of the present invention are used to prevent the inflammatory burden of the lungs (e.g. blockade of the IAV-induced inflammation). As used herein, an "anti-platelet agent" refers to members of a class of pharmaceuticals that inhibit platelet function, for example, by inhibiting the activation, aggregation, adhesion or granular secretion of platelets. One important feature of the present invention the anti-platelet agent is not a PAR-1 antagonist, nor aspirin.

In some embodiments, the anti-platelet agent is selected from the group consisting of GPIIb/IIIa antagonists (e.g., tirofiban, eptifibatide, and abciximab), thromboxane-A2 -receptor antagonists (e.g., ifetroban), thromboxane-A2-synthetase inhibitors, phosphodiesterase-III (PDE-III) inhibitors (e.g., dipyridamole, cilostazol), and PDE V inhibitors (such as sildenafil), and pharmaceutically acceptable salts or prodrugs thereof. In some embodiments, the GPIIb/IIIa antagonist is not tirofiban.

In some embodiments, the anti-platelet agent of the present invention is selected from the group consisting of ADP (adenosine diphosphate) receptor antagonists, in particular antagonists of the purinergic receptors P2Y1 and P2Y12. Typically P2Y12 receptor antagonists include ticlopidine, clopidogrel, Prasugrel, AR-C69931MX, Cangrelor, MRS2179 1 including pharmaceutically acceptable salts or prodrugs thereof. In some embodiments, the anti-platelet agent of the present invention is a PAR-4 antagonist.

As used herein the term "PAR4" has its general meaning in the art and refers to protease-activated receptor ' which is a low-affinity receptor that mediates thrombin signaling at high concentrations (C-C. Wu et a/, Eur. J. Pharmacol, 2006, 546, 142-147).

PAR-4 antagonists are well known in the art (Giuseppe Cirino, Beatrice Severino Thrombin receptors and their antagonists: an update on the patent literature. Expert Opinion on Therapeutic Patents Jul 2010, Vol. 20, No. 7, Pages 875-884). Compounds that function as PAR-4 antagonists are disclosed, for example, in EP667345B1, EP1166785A1, JP 2002080367, EP1331233, and US2006106032, all incorporated by reference.

In some embodiments, thePAR-4 antagonist is a small organic molecule. In some embodiments, the PAR4 antagonists is the indazole derivative YD-3 (ethyl 4- (1- benzyl-lH-indazol-3-yl)benzoate) (Wu CC, Huang SW, Hwang TL, YD-3, a novel inhibitor of protease-induced platelet activation. Br J Pharmacol 2000;130: 1289-96) which has the general formula of:

In some embodiments, the PAR4 antagonist is selected from the group consisting of :

ll-b

or a pharmaceutically acceptable salt thereof. These compounds are described in EP 667345 Bl . US 5,574,168 or US2006106032 Al . all herein incorporated by reference.

In some embodiments, the PAR4 antagonist is selected from the group consisting of imidazothiadiazole and imidazopyridazine derivatives as described in WO2013163241. In some embodiments, the PAR4 antagonist is selected from the group consisting of:

In some embodiments, the PAR4 antagonist is selected from the group consisting of pepducins. In some embodiments the PAR4 antagonist is P4pall0, whose sequence is pal- S GRRYGH ALR-NH2 (SEQ ID NO: l) (Kuliopulos A, Covic L. G protein coupled receptor (GPCR) agonists and antagonists and methods of activating and inhibiting GPCR using the same. US6864229; 2005, Covic L, Gresser AL, Talavera J, Activation and inhibition of G protein-coupled receptors by cell-penetrating membrane tethered peptides. PNAS 2002;99:643-8 Covic L, Misra M, Badar J, Pepducin-based intervention of thrombin- receptor signaling and systemic platelet activation. Nat Med 2002;8(10);1161-5) or a structurally unrelated PAR-4 antagonist, trans-cinnamoyl-YPGKF-NH2 (SEQ ID NO:2).

In one embodiment, the anti-platelet agent of the present invention is an antibody which acts as a GPIIb/IIIa antagonist, a thromboxane- A2 -receptor antagonist, an ADP (adenosine diphosphate) receptor antagonist (in particular a antagonist of the purinergic receptors P2Y1 and P2Y12), or a PAR4 antagonist.

As used herein, "antibody" includes both naturally occurring and non-naturally occurring antibodies. Specifically, "antibody" includes polyclonal and monoclonal antibodies, and monovalent and divalent fragments thereof. Furthermore, "antibody" includes chimeric antibodies, wholly synthetic antibodies, single chain antibodies, and fragments thereof. The antibody may be a human or non human antibody. A non human antibody may be humanized by recombinant methods to reduce its immunogenicity in man.

In one embodiment of the antibodies or portions thereof described herein, the antibody is a monoclonal antibody. In one embodiment of the antibodies or portions thereof described herein, the antibody is a polyclonal antibody. In one embodiment of the antibodies or portions thereof described herein, the antibody is a humanized antibody. In one embodiment of the antibodies or portions thereof described herein, the antibody is a chimeric antibody. In one embodiment of the antibodies or portions thereof described herein, the portion of the antibody comprises a light chain of the antibody. In one embodiment of the antibodies or portions thereof described herein, the portion of the antibody comprises a heavy chain of the antibody. In one embodiment of the antibodies or portions thereof described herein, the portion of the antibody comprises a Fab portion of the antibody. In one embodiment of the antibodies or portions thereof described herein, the portion of the antibody comprises a F(ab')2 portion of the antibody. In one embodiment of the antibodies or portions thereof described herein, the portion of the antibody comprises a Fc portion of the antibody. In one embodiment of the antibodies or portions thereof described herein, the portion of the antibody comprises a Fv portion of the antibody. In one embodiment of the antibodies or portions thereof described herein, the portion of the antibody comprises a variable domain of the antibody. In one embodiment of the antibodies or portions thereof described herein, the portion of the antibody comprises one or more CDR domains of the antibody.

Typically, monoclonal antibodies are prepared according to conventional methodology. Monoclonal antibodies may be generated using the method of Kohler and Milstein (Nature, 256:495, 1975). To prepare monoclonal antibodies useful in the invention, a mouse or other appropriate host animal is immunized at suitable intervals (e.g., twice-weekly, weekly, twice-monthly or monthly) with the relevant antigenic forms (e.g. PAR4 polypeptides). The animal may be administered a final "boost" of antigen within one week of sacrifice. It is often desirable to use an immunologic adjuvant during immunization. Suitable immunologic adjuvants include Freund's complete adjuvant, Freund's incomplete adjuvant, alum, Ribi adjuvant, Hunter's Titermax, saponin adjuvants such as QS21 or Quil A, or CpG- containing immunostimulatory oligonucleotides. Other suitable adjuvants are well-known in the field. The animals may be immunized by subcutaneous, intraperitoneal, intramuscular, intravenous, intranasal or other routes. A given animal may be immunized with multiple forms of the antigen by multiple routes. Briefly, the recombinant protein may be provided by expression with recombinant cell lines, in particular in the form of human cells expressing the receptor (e.g. PAR4) at their surface. Following the immunization regimen, lymphocytes are isolated from the spleen, lymph node or other organ of the animal and fused with a suitable myeloma cell line using an agent such as polyethylene glycol to form a hydridoma. Following fusion, cells are placed in media permissive for growth of hybridomas but not the fusion partners using standard methods, as described (Coding, Monoclonal Antibodies: Principles and Practice: Production and Application of Monoclonal Antibodies in Cell Biology, Biochemistry and Immunology, 3rd edition, Academic Press, New York, 1996). Following culture of the hybridomas, cell supernatants are analyzed for the presence of antibodies of the desired specificity, i.e., that selectively bind the antigen. Suitable analytical techniques include ELISA, flow cytometry, immunoprecipitation, and western blotting. Other screening techniques are well-known in the field. Preferred techniques are those that confirm binding of antibodies to conformationally intact, natively folded antigen, such as non-denaturing ELISA, flow cytometry, and immunoprecipitation.

Significantly, as is well-known in the art, only a small portion of an antibody molecule, the paratope, is involved in the binding of the antibody to its epitope (see, in general, Clark, W. R. (1986) The Experimental Foundations of Modern Immunology Wiley & Sons, Inc., New York; Roitt, I. (1991) Essential Immunology, 7th Ed., Blackwell Scientific Publications, Oxford). The Fc' and Fc regions, for example, are effectors of the complement cascade but are not involved in antigen binding. An antibody from which the pFc' region has been enzymatically cleaved, or which has been produced without the pFc' region, designated an F(ab')2 fragment, retains both of the antigen binding sites of an intact antibody. Similarly, an antibody from which the Fc region has been enzymatically cleaved, or which has been produced without the Fc region, designated an Fab fragment, retains one of the antigen binding sites of an intact antibody molecule. Proceeding further, Fab fragments consist of a covalently bound antibody light chain and a portion of the antibody heavy chain denoted Fd. The Fd fragments are the major determinant of antibody specificity (a single Fd fragment may be associated with up to ten different light chains without altering antibody specificity) and Fd fragments retain epitope-binding ability in isolation. Within the antigen-binding portion of an antibody, as is well-known in the art, there are complementarity determining regions (CDRs), which directly interact with the epitope of the antigen, and framework regions (FRs), which maintain the tertiary structure of the paratope (see, in general, Clark, 1986; Roitt, 1991). In both the heavy chain Fd fragment and the light chain of IgG immunoglobulins, there are four framework regions (FR1 through FR4) separated respectively by three complementarity determining regions (CDR1 through CDRS). The CDRs, and in particular the CDRS regions, and more particularly the heavy chain CDRS, are largely responsible for antibody specificity.

It is now well-established in the art that the non CDR regions of a mammalian antibody may be replaced with similar regions of conspecific or heterospecific antibodies while retaining the epitopic specificity of the original antibody. This is most clearly manifested in the development and use of "humanized" antibodies in which non-human CDRs are covalently joined to human FR and/or Fc/pFc' regions to produce a functional antibody. This invention provides in certain embodiments compositions and methods that include humanized forms of antibodies. As used herein, "humanized" describes antibodies wherein some, most or all of the amino acids outside the CDR regions are replaced with corresponding amino acids derived from human immunoglobulin molecules. Methods of humanization include, but are not limited to, those described in U.S. Pat. Nos. 4,816,567,5,225,539,5,585,089, 5,693,761, 5,693,762 and 5,859,205, which are hereby incorporated by reference. The above U.S. Pat. Nos. 5,585,089 and 5,693,761, and WO 90/07861 also propose four possible criteria which may used in designing the humanized antibodies. The first proposal was that for an acceptor, use a framework from a particular human immunoglobulin that is unusually homologous to the donor immunoglobulin to be humanized, or use a consensus framework from many human antibodies. The second proposal was that if an amino acid in the framework of the human immunoglobulin is unusual and the donor amino acid at that position is typical for human sequences, then the donor amino acid rather than the acceptor may be selected. The third proposal was that in the positions immediately adjacent to the 3 CDRs in the humanized immunoglobulin chain, the donor amino acid rather than the acceptor amino acid may be selected. The fourth proposal was to use the donor amino acid reside at the framework positions at which the amino acid is predicted to have a side chain atom within 3 A of the CDRs in a three dimensional model of the antibody and is predicted to be capable of interacting with the CDRs. The above methods are merely illustrative of some of the methods that one skilled in the art could employ to make humanized antibodies. One of ordinary skill in the art will be familiar with other methods for antibody humanization.

In one embodiment of the humanized forms of the antibodies, some, most or all of the amino acids outside the CDR regions have been replaced with amino acids from human immunoglobulin molecules but where some, most or all amino acids within one or more CDR regions are unchanged. Small additions, deletions, insertions, substitutions or modifications of amino acids are permissible as long as they would not abrogate the ability of the antibody to bind a given antigen. Suitable human immunoglobulin molecules would include IgGl, IgG2, IgG3, IgG4, IgA and IgM molecules. A "humanized" antibody retains a similar antigenic specificity as the original antibody. However, using certain methods of humanization, the affinity and/or specificity of binding of the antibody may be increased using methods of "directed evolution", as described by Wu et al, /. Mol. Biol. 294: 151, 1999, the contents of which are incorporated herein by reference. Fully human monoclonal antibodies also can be prepared by immunizing mice transgenic for large portions of human immunoglobulin heavy and light chain loci. See, e.g., U.S. Pat. Nos. 5,591,669, 5,598,369, 5,545,806, 5,545,807, 6,150,584, and references cited therein, the contents of which are incorporated herein by reference. These animals have been genetically modified such that there is a functional deletion in the production of endogenous (e.g., murine) antibodies. The animals are further modified to contain all or a portion of the human germ-line immunoglobulin gene locus such that immunization of these animals will result in the production of fully human antibodies to the antigen of interest. Following immunization of these mice (e.g., XenoMouse (Abgenix), HuMAb mice (Medarex/GenPharm)), monoclonal antibodies can be prepared according to standard hybridoma technology. These monoclonal antibodies will have human immunoglobulin amino acid sequences and therefore will not provoke human anti-mouse antibody (KAMA) responses when administered to humans.

In vitro methods also exist for producing human antibodies. These include phage display technology (U.S. Pat. Nos. 5,565,332 and 5,573,905) and in vitro stimulation of human B cells (U.S. Pat. Nos. 5,229,275 and 5,567,610). The contents of these patents are incorporated herein by reference.

Thus, as will be apparent to one of ordinary skill in the art, the present invention also provides for F(ab') 2 Fab, Fv and Fd fragments; chimeric antibodies in which the Fc and/or FR and/or CDRl and/or CDR2 and/or light chain CDR3 regions have been replaced by homologous human or non-human sequences; chimeric F(ab')2 fragment antibodies in which the FR and/or CDRl and/or CDR2 and/or light chain CDR3 regions have been replaced by homologous human or non-human sequences; chimeric Fab fragment antibodies in which the FR and/or CDRl and/or CDR2 and/or light chain CDR3 regions have been replaced by homologous human or non-human sequences; and chimeric Fd fragment antibodies in which the FR and/or CDRl and/or CDR2 regions have been replaced by homologous human or non- human sequences. The present invention also includes so-called single chain antibodies.

The various antibody molecules and fragments may derive from any of the commonly known immunoglobulin classes, including but not limited to IgA, secretory IgA, IgE, IgG and IgM. IgG subclasses are also well known to those in the art and include but are not limited to human IgGl, IgG2, IgG3 and IgG4.

In some embodiments, the antibody according to the invention is a single domain antibody. The term "single domain antibody" (sdAb) or "VHH" refers to the single heavy chain variable domain of antibodies of the type that can be found in Camelid mammals which are naturally devoid of light chains. Such VHH are also called "nanobody®". According to the invention, sdAb can particularly be llama sdAb. In some embodiments, the agent is an aptamer which acts as a GPIIb/IIIa antagonist, a thromboxane- A2 -receptor antagonist, an ADP (adenosine diphosphate) receptor antagonist (in particular a antagonist of the purinergic receptors P2Y1 and P2Y12), or a PAR4 antagonist. Aptamers are a class of molecule that represents an alternative to antibodies in term of molecular recognition. Aptamers are oligonucleotide or oligopeptide sequences with the capacity to recognize virtually any class of target molecules with high affinity and specificity. Such ligands may be isolated through Systematic Evolution of Ligands by Exponential enrichment (SELEX) of a random sequence library. The random sequence library is obtainable by combinatorial chemical synthesis of DNA. In this library, each member is a linear oligomer, eventually chemically modified, of a unique sequence.

In some embodiments, the anti-platelet agent of the present invention is an inhibitor of gene expression wherein the gene is typically selected from the group of genes encoding for GPIIb/IIIa receptort, a thromboxane-A2 -receptor, an ADP (adenosine diphosphate) receptor (in particular the purinergic receptors P2Y1 and P2Y12), or PAR4. An "inhibitor of gene expression" refers to a natural or synthetic compound that has a biological effect to inhibit the expression of a gene. In a preferred embodiment of the invention, said inhibitor of gene expression is a siRNA, an antisense oligonucleotide or a ribozyme. For example, anti-sense oligonucleotides, including anti-sense RNA molecules and anti-sense DNA molecules, would act to directly block the translation of mineralocorticoid receptor mRNA by binding thereto and thus preventing protein translation or increasing mRNA degradation, thus decreasing the level of mineralocorticoid receptor, and thus activity, in a cell. For example, antisense oligonucleotides of at least about 15 bases and complementary to unique regions of the mRNA transcript sequence encoding mineralocorticoid receptor can be synthesized, e.g., by conventional phosphodiester techniques. Methods for using antisense techniques for specifically inhibiting gene expression of genes whose sequence is known are well known in the art (e.g. see U.S. Pat. Nos. 6,566,135; 6,566,131; 6,365,354; 6,410,323; 6,107,091; 6,046,321; and 5,981,732). Small inhibitory RNAs (siRNAs) can also function as inhibitors of expression for use in the present invention, mineralocorticoid receptor gene expression can be reduced by contacting a subject or cell with a small double stranded RNA (dsRNA), or a vector or construct causing the production of a small double stranded RNA, such that mineralocorticoid receptor gene expression is specifically inhibited (i.e. RNA interference or RNAi). Antisense oligonucleotides, siRNAs, shRNAs and ribozymes of the invention may be delivered in vivo alone or in association with a vector. In its broadest sense, a "vector" is any vehicle capable of facilitating the transfer of the antisense oligonucleotide, siRNA, shRNA or ribozyme nucleic acid to the cells and typically cells expressing mineralocorticoid receptor. Typically, the vector transports the nucleic acid to cells with reduced degradation relative to the extent of degradation that would result in the absence of the vector. In general, the vectors useful in the invention include, but are not limited to, plasmids, phagemids, viruses, other vehicles derived from viral or bacterial sources that have been manipulated by the insertion or incorporation of the antisense oligonucleotide, siRNA, shRNA or ribozyme nucleic acid sequences. Viral vectors are a preferred type of vector and include, but are not limited to nucleic acid sequences from the following viruses: retrovirus, such as moloney murine leukemia virus, harvey murine sarcoma virus, murine mammary tumor virus, and rous sarcoma virus; adenovirus, adeno-associated virus; SV40-type viruses; polyoma viruses; Epstein-Barr viruses; papilloma viruses; herpes virus; vaccinia virus; polio virus; and RNA virus such as a retrovirus. One can readily employ other vectors not named but known to the art. The anti-platelet agents of the present invention are administered to the subject in a therapeutically effective amount. As used herein, a "therapeutically effective amount" refers to an amount sufficient to elicit the desired biological response. In the present invention the desired biological response is to reduce or ameliorate the severity, duration, progression, of the infection, and more particular to reduce or ameliorate the inflammatory burden of the lungs. The precise amount of the anti-platelet agent administered to a subject will depend on the mode of administration, the type and severity of the infection and on the characteristics of the subject, such as general health, age, sex, body weight and tolerance to drugs. The skilled artisan will be able to determine appropriate dosages depending on these and other factors. When co-administered with anti viral agents, e.g., when coadministered with an anti-influenza medication, an "effective amount" of the second agent will depend on the type of drug used. Suitable dosages are known for approved agents and can be adjusted by the skilled artisan according to the condition of the subject, the type of conditio n(s) being treated and the amount of a compound described herein being used. In cases where no amount is expressly noted, an effective amount should be assumed. For example, anti-platelet agents described herein can be administered to a subject in a dosage range from between approximately 0.01 to 100 mg/kg body weight/day for therapeutic or prophylactic treatment. Dosages of the antiplatelet agents described herein can range from between about 0.01 to about 100 mg/kg body weight/day, about 0.01 to about 50 mg/kg body weight/day, about 0.1 to about 50 mg/kg body weight/day, or about 1 to about 25 mg/kg body weight/day. It is understood that the total amount per day can be administered in a single dose or can be administered in multiple dosing, such as twice a day (e.g., every 12 hours), tree times a day (e.g., every 8 hours), or four times a day (e.g., every 6 hours). For a therapeutic treatment, the anti-platelet agents of the present invention can be administered to a subject within, for example, 48 hours (or within 40 hours, or less than 2 days, or less than 1.5 days, or within 24 hours) of onset of symptoms (e.g., nasal congestion, sore throat, cough, aches, fatigue, headaches, and chills/sweats). The therapeutic treatment can last for any suitable duration, for example, for 5 days, 7 days, 10 days, 14 days, etc.

In some embodiments the anti-platelet agents of the present invention are use in combination with an additional suitable therapeutic agent, for example, an antiviral agent or a vaccine. When "combination therapy" is employed, an effective amount can be achieved using a first amount of a anti-platelet agent and a second amount of an additional suitable therapeutic agent (e.g. an antiviral agent or vaccine).

Specific examples that can be co-administered with an anti-platelet agent of the present invention include neuraminidase inhibitors. Examples of neuraminidase inhibitors include oseltamivir, oseltamivir carboxylate (GS4071; see e.g. Eisenberg et al., Antimicrob Agents Chemother. (1997) 41 : 1949-52), zanamivir, peramivir (RWJ-27021; BXC-1812, BioCryst), 2,3-didehydro-2-deoxy-N-acetylneuraminic acid (DANA), 2-deoxy-2,3-dehydro- N-trifluoroacetylneuraminic acid (FANA), A-322278, and A-315675 (see US Pat. No. 6,455, 571 to Maring et al, and Kati et al, Antimicrob Agents Chemother. (2002) 46: 1014-21). Specific examples that can be co-administered with an anti-platelet agent include M2 inhibitors. Examples of M2 inhibitors include include amino adamantane compounds such as amantadine (1-amino-adamantane), rimantadine (l-(l-aminoethyl)adamantane), spiro[cyclopropane-l,2'-adamantan]-2-amine, spiro[pyrrolidine-2,2'-adamantane], spiro[piperidine-2,2'-adamantane], 2-(2-adamantyl)piperidine, 3-(2-adamantyl)pyrrolidine, 2- (1-adamantyl) piperidine, 2-(l-adamantyl)pyrrolidine, and 2-(ladamantyl)-2-methyl- pyrrolidine; and M2-specific monoclonal antibodies (see e.g. US 20050170334; and Zebedee and Lamb, J. Virol. (1988) 62:2762-72). Specific examples that can be co-administered with an anti-platelet agent include RNA polymerase inhibitors. As used herein, the term RNA polymerase inhibitor refers to an antiviral agent that inhibits the polymerase, protease, and/or endonuclease activity of the viral RNA polymerase complex or one of its subunits (i.e. PB1, PB2andPA). Exemplary RNA polymerase inhibitors include antiviral nucleoside analogs such as ribavirin, viramidine, 6- fluoro-3-hydroxy-2pyrazinecarboxamide (T-705), 2'-deoxy-2'-fluoroguanosine, pyrazofurin, 3-deazaguanine, carbodine (see e.g. Shannon et al, Antimicrob Agents Chemother. (1981) 20:769-76), and cyclopenenyl cytosine (see e.g. Shigeta et al, Antimicrob Agents Chemother. (1988) 32:906-11); and the endonuclease inhibitor flutimide (see e.g. Tomassini et al, Antimicrob Agents Chemother. (1996) 40: 1189-93).

Specific examples that can be co-administered with an anti-platelet agent include influenza- specific interfering oligonucleotides Examples of influenza- specific interfering oligonucleotides include siRNAs (see e.g. Zhou et al, Antiviral Res. (2007) 76: 186-93), antisense oligonucleotides, phosphorothioate oligonucleotides, ribozymes (see e.g. U.S. Pat. No. 6,258,585 to Draper), morpholino oligomers and peptide nucleic acids (see e.g. Schubert and Kurreck, Handb Exp Pharmacol. (2006) 173:261-87).

Specific examples that can be co-administered with an anti-platelet agent include interferons. An "interferon" or "IFN", as used herein, is intended to include any molecule defined as such in the literature, comprising for example any types of IFNs (type I and type II) and in particular, IFN-alpha, IFN-beta, INF-omega and IFN-gamma. The term interferon, as used herein, is also intended to encompass salts, functional derivatives, variants, muteins, fused proteins, analogs and active fragments thereof. In a preferred embodiment the interferon is interferon-alpha. Interferon-alpha includes, but is not limited to, recombinant interferon-a2a (such as ROFERON® interferon available from Hoffman-LaRoche, Nutley, N.J.), interferon- a2b (such as Intron-A interferon available from Schering Corp., Kenilworth, N.J., USA), a consensus interferon, and a purified interferon-a product. In some embodiments, a combination therapy comprises active immunization with an influenza antigenic polypeptide (e.g. influenza hemagglutinin and the matrix 2 ectodomain polypeptides) or passive immunization with one or more neutralizing antibodies directed to an influenza antigenic polypeptide (e.g. antibodies raised against the influenza hemagglutinin and the matrix 2 ectodomain polypeptides).

The anti-platelet agents of the present invention are typically formulated into pharmaceutical compositions that further comprise a pharmaceutically acceptable carrier, diluent, adjuvant or vehicle. In one embodiment, the present invention relates to a pharmaceutical composition comprising a anti-platelet agent described above, and a pharmaceutically acceptable carrier, diluent, adjuvant or vehicle. In one embodiment, the present invention is a pharmaceutical composition comprising an effective amount of a compound of the present invention or a pharmaceutically acceptable salt thereof and a pharmaceutically acceptable carrier, diluent, adjuvant or vehicle. Pharmaceutically acceptable carriers include, for example, pharmaceutical diluents, excipients or carriers suitably selected with respect to the intended form of administration, and consistent with conventional pharmaceutical practices.

A pharmaceutically acceptable carrier may contain inert ingredients which do not unduly inhibit the biological activity of the compounds. The pharmaceutically acceptable carriers should be biocompatible, e.g., non-toxic, non-inflammatory, non-immunogenic or devoid of other undesired reactions or side-effects upon the administration to a subject. Standard pharmaceutical formulation techniques can be employed.

The pharmaceutically acceptable carrier, adjuvant, or vehicle, as used herein, includes any and all solvents, diluents, or other liquid vehicle, dispersion or suspension aids, surface active agents, isotonic agents, thickening or emulsifying agents, preservatives, solid binders, lubricants and the like, as suited to the particular dosage form desired. Remington's Pharmaceutical Sciences, Sixteenth Edition, E. W. Martin (Mack Publishing Co., Easton, Pa., 1980) discloses various carriers used in formulating pharmaceutically acceptable compositions and known techniques for the preparation thereof. Except insofar as any conventional carrier medium is incompatible with the anti-platelet agents of the present invention, such as by producing any undesirable biological effect or otherwise interacting in a deleterious manner with any other component(s) of the pharmaceutically acceptable composition, its use is contemplated to be within the scope of this invention.

Some examples of materials which can serve as pharmaceutically acceptable carriers include, but are not limited to, ion exchangers, alumina, aluminum stearate, lecithin, serum proteins (such as human serum albumin), buffer substances (such as twin 80, phosphates, glycine, sorbic acid, or potassium sorbate), partial glyceride mixtures of saturated vegetable fatty acids, water, salts or electrolytes (such as protamine sulfate, disodium hydrogen phosphate, potassium hydrogen phosphate, sodium chloride, or zinc salts), colloidal silica, magnesium trisilicate, polyvinyl pyrrolidone, polyacrylates, waxes, polyethylene- polyoxypropylene-block polymers, methylcellulose, hydroxypropyl methylcellulose, wool fat, sugars such as lactose, glucose and sucrose; starches such as corn starch and potato starch; cellulose and its derivatives such as sodium carboxymethyl cellulose, ethyl cellulose and cellulose acetate; powdered tragacanth; malt; gelatin; talc; excipients such as cocoa butter and suppository waxes; oils such as peanut oil, cottonseed oil; safflower oil; sesame oil; olive oil; corn oil and soybean oil; glycols; such a propylene glycol or polyethylene glycol; esters such as ethyl oleate and ethyl laurate; agar; buffering agents such as magnesium hydroxide and aluminum hydroxide; alginic acid; pyrogen-free water; isotonic saline; Ringer's solution; ethyl alcohol, and phosphate buffer solutions, as well as other non-toxic compatible lubricants such as sodium lauryl sulfate and magnesium stearate, as well as coloring agents, releasing agents, coating agents, sweetening, flavoring and perfuming agents, preservatives and antioxidants can also be present in the composition, according to the judgment of the formulator.

The compositions described herein may be administered orally, parenterally, by inhalation spray, rectally, nasally, buccally, or r via an implanted reservoir depending on the severity of the infection being treated.. The term "parenteral" as used herein includes, but is not limited to, subcutaneous, intravenous, intramuscular, intra-articular, intra- synovial, intrasternal, intrathecal, intrahepatic, intralesional and intracranial injection or infusion techniques. Specifically, the compositions are administered orally, intraperitoneally or intravenously. Sterile injectable forms of the compositions described herein may be aqueous or oleaginous suspension. These suspensions may be formulated according to techniques known in the art using suitable dispersing or wetting agents and suspending agents. The sterile injectable preparation may also be a sterile injectable solution or suspension in a nontoxic parenterally-acceptable diluent or solvent, for example as a solution in 1,3-butanediol. Among the acceptable vehicles and solvents that may be employed are water, Ringer's solution and isotonic sodium chloride solution. In addition, sterile, fixed oils are conventionally employed as a solvent or suspending medium. For this purpose, any bland fixed oil may be employed including synthetic mono- or di-glycerides. Fatty acids, such as oleic acid and its glyceride derivatives are useful in the preparation of injectables, as are natural pharmaceutically- acceptable oils, such as olive oil or castor oil, especially in their polyoxyethylated versions. These oil solutions or suspensions may also contain a long-chain alcohol diluent or dispersant, such as carboxymethyl cellulose or similar dispersing agents which are commonly used in the formulation of pharmaceutically acceptable dosage forms including emulsions and suspensions. Other commonly used surfactants, such as Tweens, Spans and other emulsifying agents or bioavailability enhancers which are commonly used in the manufacture of pharmaceutically acceptable solid, liquid, or other dosage forms may also be used for the purposes of formulation. The pharmaceutical compositions described herein may be orally administered in any orally acceptable dosage form including, but not limited to, capsules, tablets, aqueous suspensions or solutions. In the case of tablets for oral use, carriers commonly used include, but are not limited to, lactose and corn starch. Lubricating agents, such as magnesium stearate, are also typically added. For oral administration in a capsule form, useful diluents include lactose and dried cornstarch. When aqueous suspensions are required for oral use, the active ingredient is combined with emulsifying and suspending agents. If desired, certain sweetening, flavoring or coloring agents may also be added.

Alternatively, the pharmaceutical compositions described herein may be administered in the form of suppositories for rectal administration. These can be prepared by mixing the agent with a suitable non-irritating excipient which is solid at room temperature but liquid at rectal temperature and therefore will melt in the rectum to release the drug. Such materials include, but are not limited to, cocoa butter, beeswax and polyethylene glycols. The pharmaceutical compositions may also be administered to the respiratory tract. The respiratory tract includes the upper airways, including the oropharynx and larynx, followed by the lower airways, which include the trachea followed by bifurcations into the bronchi and bronchioli. Pulmonary delivery compositions can be delivered by inhalation by the patient of a dispersion so that the active ingredient within the dispersion can reach the lung where it can, for example, be readily absorbed through the alveolar region directly into blood circulation. Pulmonary delivery can be achieved by different approaches, including the use of nebulized, aerosolized, micellular and dry powder-based formulations; administration by inhalation may be oral and/or nasal. Delivery can be achieved with liquid nebulizers, aerosol-based inhalers, and dry powder dispersion devices. Metered-dose devices are preferred. One of the benefits of using an atomizer or inhaler is that the potential for contamination is minimized because the devices are self contained. Dry powder dispersion devices, for example, deliver drugs that may be readily formulated as dry powders. A pharmaceutical composition of the invention may be stably stored as lyophilized or spray- dried powders by itself or in combination with suitable powder carriers. The delivery of a pharmaceutical composition of the invention for inhalation can be mediated by a dosing timing element which can include a timer, a dose counter, time measuring device, or a time indicator which when incorporated into the device enables dose tracking, compliance monitoring, and/or dose triggering to a patient during administration of the aerosol medicament. Examples of pharmaceutical devices for aerosol delivery include metered dose inhalers (MDIs), dry powder inhalers (DPIs), and air-jet nebulizers.

The compounds for use in the methods of the invention can be formulated in unit dosage form. The term "unit dosage form" refers to physically discrete units suitable as unitary dosage for subjects undergoing treatment, with each unit containing a predetermined quantity of active material calculated to produce the desired therapeutic effect, optionally in association with a suitable pharmaceutical carrier. The unit dosage form can be for a single daily dose or one of multiple daily doses (e.g., about 1 to 4 or more times per day). When multiple daily doses are used, the unit dosage form can be the same or different for each dose.

The invention will be further illustrated by the following figures and examples. However, these examples and figures should not be interpreted in any way as limiting the scope of the present invention. FIGURES:

Figure 1: Upon IAV infection, platelets infiltrate the lungs, and IAV particles are observed in platelets. (A) Immunohistochemistry analysis of lungs from uninfected (NI) or infected mice inoculated with A/PR/8/34 virus, at a sublethal dose (75 pfu/mouse) or LDso (250 pfu/mouse; day 6 post-infection). Antibodies against the IAV nucleoprotein (NP) and CD41 were used to detect virus infected cells and platelets, respectively. The results are representative of three mice per group. (B) Platelet numbers in BAL were assessed using a Vet ABCTM Hematology Analyzer on day 6 post-inoculation of mock or IAV-infected mice. Data are presented as the means ± SEM of 4 mice per group, ** p<0.01 for LD₅₀ vs. NI. (C) Immunofluorescence staining of viral particles in platelets from BAL was performed with anti- influenza HA antibody. Platelets were detected with anti-CD41 antibody, and nuclei were counterstained with DAPI. The merged images are shown on the right panel. CD41 -negative cells from BAL were used as a negative control. (D) Immunogold labeling of ultrathin cryosections of lungs of uninfected (NI) or A/PR/8/34 virus-infected mice (LD₅₀, 250 pfu/mouse, day 6 post-infection) was performed using a specific anti-HA antibody. Black arrows indicate viral particles. Staining of a platelet-like granule is shown on the upper right panel. As a control for HA staining, electron microscopic immunogold labeling was performed on purified A/PR/8/34 viruses using the anti-HA antibody (lower right panel).

Figure 2: Upon IAV infection, platelets are stimulated and contribute to influenza pathogenesis. (A) Serotonin and sP-selectin were measured by ELISA in the BAL and plasma of Mock (NI) or A/PR 8/34 virus-infected mice, respectively, on day 6 post- inoculation (75 pfu/mouse, sublethal dose or 250 pfu/mouse, LDso). Data represent the means ± SEM of 4 mice per group, * p<0.05 for LD₅₀ vs. NI; ** p<0.01 for LD₅₀ vs. NI. (B) Blood samples from uninfected (NI) or infected mice were double-stained with anti-P-selectin and anti-CD41 antibody as a platelet identifier. The mean percentage ± SEM of activated platelets (CD41 and P-selectin-positive) from five mice per group is shown in the right panel, * p<0.05 for LD₅₀ vs. NI. (C) Ultrastructure analysis of platelets in the lungs of uninfected and infected mice (A/PR/8/34, 250 pfu/mouse, LDso). Note the aggregation of platelets in the lungs of infected mice along with their morphological changes (arrows) and the absence of granules in some of them, which reflects their degranulation (asterisks). Sections show platelet aggregates with an interstitial localization. (D) Survival of platelet GPIIIa^{" "} mice and WT littermates after infection with A/PR/8/34 virus at a LDso (250 pfu/mouse, n=9-10 mice per group) or lethal dose (350 pfu/mouse n=6 mice per group); * p<0.05 and ** p<0.01, respectively.

Figure 3: Platelet activation and inflammation. (A) Platelet numbers in BAL of A/PR/8/34 virus infected mice (250 pfu/mouse, LDso) were assessed using a Vet ABCTM Hematology Analyzer, at the indicated time post-inoculation. The results are represented as the means ± SEM of 4 mice per group. On days 0 and 6, additional results from Figure IB are included. (B-D) sP-selectin in the plasma (B), ILl-β in the BAL (C) and ILl-β in the plasma (D) of infected mice (A/PR/8/34, 250 pfu/mouse, LDso) were determined by ELISA at the indicated times. The results from panels B-D represent the means ± SEM of 4 mice per group. From A-D: * p<0.05, ** p<0.01 , *** p<0.001 for the indicated time vs. 0. (E) Ultrastructural analysis of platelets associated with leukocytes in the lungs of infected mice (A/PR/8/34, 250 pfu/mouse, LDso). The star shows platelet aggregates that are not adherent to leukocytes. Figure 4: Effects of PAR4 activation on IAV pathogenicity, virus replication and inflammation. (A) Serotonin and sP-selectin were measured by ELISA in the BAL and plasma, respectively, of infected mice (A/PR 8/34, 75 pfu/mouse, sublethal dose) after treatment with PAR4-AP or control peptide (Control-P) on day 6 post-inoculation. Columns represent the means ± SEM (n=4-5). ** p<0.01; * p<0.05. (B) Time course of IAV-induced death in mice in response to PAR4 stimulation. Mice were mock-infected or inoculated with A/PR/8/34 virus (75 pfu/mouse, sublethal dose, n=18-19 mice per group; or 250 pfu/mouse, LDso, n=6-12 mice per group) and treated with either control peptide or PAR4-AP. * p<0.05; ** p<0.01. (C) Time course of IAV-induced death in mice (A/PR/8/34virus) in response to PAR4 stimulation and after treatment or no treatment with eptifibatide (n=6-18 mice per group). * p<0.05 for PAR4-AP vs. control-P. A significant difference (p<0.01) was also found between groups treated with PAR-AP ± eptifibatide (not shown) (D) Time course of IAV- induced death in WT (n=10 mice per group) and GPIIIa^{" "} mice (n=7-9 mice per group) in response to PAR4 stimulation (A/PR/8/34virus). The same mice were used in Figure 2D (250 pfu/mouse, dose LDso). *** p<0.001 for PAR4-AP vs. control-P in WT mice. (E) Lung virus titers after infection of mice with A/PR/8/34 virus (sublethal dose) stimulated or not with PAR4-AP. (F) Total protein quantification in BAL of infected mice in response to PAR4 stimulation. For E and F, the results represent the means ± SEM (n=3-5). ** p<0.01 for PAR4-AP vs. control-P. Figure 5: PAR4-AP increases lung inflammation upon A/PR/8/34 virus infection.

(A) Cytokines in the BAL of infected mice (75 pfu/mouse, sublethal dose), treated with PAR4-AP or control peptide, were measured by ELISA 3 and 6 days after inoculation. Uninfected mice (NI) were used as control. The results represent the means ± SEM (n=3-5). * p<0.05, ** p<0.01 for PAR4-AP vs. control-P. (B) Histopathological analysis of lungs from uninfected mice or mice infected with a sublethal dose (75 pfu/mouse) of A/PR/8/34 virus after treatment with PAR4-AP or control peptide, on day 6 post-infection. Thin sections of lungs were stained with hematoxylin and eosin (HE). Note the marked infiltration of cells in the lungs of infected mice stimulated with PAR4-AP. Immunohistochemistry used antibodies against Ly6G. Viral NP was used to detect neutrophils and virus-infected cells. Data are representative of three mice per group.

Figure 6: PAR4 antagonist protects mice against IAV infection and deleterious lung inflammation. (A) IAV-induced pathogenesis in mice treated or not with the PAR4 antagonist pepducin p4pal-10 (pepducin). Mice were inoculated with A/PR/8/34 virus (250 pfu/mouse, LDso, n=13 mice per group) or A/HK/1/68 (100 pfu/mouse, LD₅₀, n=12 mice per group) and treated with pepducin or saline. Survival was then monitored for 2 weeks. * p<0.05. (B) Thromboxane B2 (TXB2) was measured by ELISA in the BAL of infected mice (A/PR/8/34, 250 pfu/mouse, LDso) after treatment with pepducin or vehicle, on day 6 post- inoculation. Data represent the mean ± SEM of 4-6 mice per group. (C) Lung virus titers after infection of mice with A/PR/8/34 virus (250 pfu/mouse, LDso) treated with pepducin or vehicle. The results represent the means ± SEM from 3 individual animals per group. (D) Relative leukocyte and neutrophil numbers in BAL from mice treated with pepducin or vehicle, determined by May-Grunwald-Giemsa staining 6 days after inoculation. Data represent the means ± SEM from 6 individual mice per group. (E, F) Total proteins and levels of cytokines were determined by ELISA in the BAL of infected mice (A/PR/8/34, 250 pfu/mouse, LDso) after treatment with pepducin or vehicle, on day 6 post-inoculation. The results represent the means ± SEM of 6 mice per group. (G) Histopathological analysis of lungs from mice infected with A/PR/8/34 virus (250 pfu/mouse, LDso) after treatment with pepducin or vehicle, on day 6 post-infection. Lung sections were stained with hematoxylin and eosin (HE). Immunohistochemistry using antibodies against Ly6G, viral NP was used to detect neutrophils and virus-infected cells. Data are representative of three mice per group. (B-F). * p<0.05, ** p<0.01 for pepducin vs. saline. Figure 7: Eptifibatide protects mice against IAV infection, independently of the strain. (A) Ultrastructural analysis of platelets in the lungs of infected mice (A/PR/8/34, 250 pfu/mouse, LDso), treated or not with eptifibatide, was performed by transmission electron microscopy. Note the aggregation of platelets in the lungs of infected mice, and their disaggregation after treatment of mice with eptifibatide. Sections show platelet aggregates with an interstitial localization. (B) Thromboxane B2 (TXB2) was measured by ELISA in the BAL of infected mice (A/NL/602/09, 30,000 pfu/mouse LDso) after treatment with eptifibatide or vehicle. The results represent the means ± SEM of 3-5 mice per group. sP- selectin was measured by ELISA in the plasma of A/PR/8/34 virus-infected mice (250 pfu/mouse, LDso) that were treated or not with eptifibatide, on day 6 post-inoculation. Data represent the means ± SEM of 4 mice per group. * p<0.05 for pepducin vs. saline. (C) Survival of mice treated with eptifibatide or vehicle after infection with IAV A/PR/8/34 (n=13 mice per group, 250 pfu/mouse), A/NL/602/09 (n=9-12 mice per group, 30,000 pfu/mouse) or A/HK/1/68 (n=12 mice per group, 100 pfu/mouse) at their respective LDso values. A/FPV/Bratislava/79 was used at 5 Pfu/mouse (n=6-7 mice per group). * p<0.05, ** p<0.01 for pepducin vs. saline.

Figure 8: Eptifibatide treatment prevents severe inflammation during influenza virus infections. (A) Survival of GPIIIa^{" "} (n=5 mice/group) and WT mice (n=12 mice/group) after infection with IAV A/PR 8/34 (300 pfu/mouse) and treatment or no treatment with eptifibatide. * p<0.05 for eptifibatide vs. saline. (B) Lung virus titers after infection of mice with the A/NL/602/09 virus (30,000 pfu/mouse, LDso) treated with eptifibatide or vehicle. Data represent the means ± SEM from 3 individual animals per group. (C) IFN-a was measured by ELISA in the BAL of infected mice (A/PR 8/34, 250 pfu/mice) after treatment with eptifibatide or vehicle. The results represent the means ± SEM of 4 mice per group. (D, E) Total proteins and levels of cytokines were determined by ELISA in the BAL of infected mice (30 000 pfu/mouse, A/NL/602/09, LDso) after treatment with eptifibatide or vehicle. The results represent the means ± SEM of 3-5 mice per group. * p<0.05, ** p<0.01 for eptifibatide vs. saline. (F) Histopathological analysis of lungs from mice infected with A/NL/602/09 virus (30 000 pfu/mouse, LDso) after treatment with eptifibatide or vehicle, on day 6 post-infection. Lung sections were stained with hematoxylin and eosin (HE). Immunohistochemistry using antibodies against Ly6G and viral NP was used to detect neutrophils and virus-infected cells. Data are representative of three mice per group. (G) Survival of mice treated with MRS 2179, clopidogrel or vehicle after infection with IAV A/PR/8/34 (250 pfu/mouse; n=12 mice per group). ** p<0.01 for MRS 2179 vs. saline; * p<0.05 for clopidogrel vs. saline.

Figure 9: Histopathological analysis of lungs from infected mice after treatment with eptiflbatide. (A) Histopathological analysis of lungs obtained from mice inoculated with A/PR/8/34 virus (250 PFU/mouse) and treated or not with eptiflbatide. In the infected group, note the extended areas with interstitial and peribronchial inflammation and interstitial and alveolar hemorrhage. In the infected group treated with eptiflbatide, note the limited areas with slight peribronchial inflammation but no major hemorrhage. (B) Blinded semiquantitative scoring of inflammatory infiltration, vascular congestion, hemorrhage, fibrin deposits and epithelial cell apoptosis in the lungs of infected mice treated or not with eptiflbatide. All lung fields were examined (50x) for each sample. The scoring was performed as follows: 0=no lesion, x=mild, xx=moderate, xxx=severe. EXAMPLE:

Reagents

A549 cells and MDCK cells were purchased from ATCC. IAV A/PR 8/34 virus (H1N1), A/HK 1/68 (H3N2) and A/NL/602/2009 (H1N1) (ATCC) were gifts from G.F. Rimmelzwaan (Erasmus, Netherlands). The highly pathogenic avian A FPV/Bratislava/79 (H7N7) strain was from the Institute of Molecular Virology, Munster, Germany. The following reagents were used: DAPI (Life Technologies, Paris, France), Alexa Fluor® secondary antibodies (Life Technologies), eptiflbatide (Integrilin^®, GlaxoSmithKline, Marly- le-Roi, France), Clopidogrel (Santa Cruz Biotechnology, Heidelberg, Germany), MRS 2179 (Tocris Bioscience, Bristol, United Kingdom), PAR4 antagonist pepducin p4pal-10 (Polypeptide Laboratories, Strasbourg, France), PAR4 agonist peptide (AYPGKF-NH₂, Bachem, Weil-am-Rhein, Germany), PAR4 control peptide (YAPGKF-NH2, Bachem) monoclonal anti-neutrophil Ly6G (Cedarlane, Tebu-bio, Le Perray en Yvelines, France), polyclonal anti-platelet CD41 (Bioss, Woburn, USA), monoclonal anti- viral HA (Santa Cruz Biotechnology, Heidelberg, Germany), monoclonal anti-IAV NP (gift from GF. Rimmelzwaan), monoclonal anti-p-Selectin FITC-conjugated (Emfret, Eibelstadt, Germany), monoclonal anti-CD41/61 PE-conjugated (Emfret); Vectastain^® ABC kit (Vector Laboratories, Burlingame, USA), 3,3'-diaminobenzidine (DAB) peroxidase substrate (Vector Laboratories), ketamine/xylazine anesthesia (Virbac, Bayer HealthCare, Carros, France), May-Grunwald and Giemsa solutions (Merck, Darmstadt, Germany), hematoxylin and eosin solutions (Diapath, Martinengo, Italy), and enzyme-linked immunosorbent assay (ELISA) kits for mouse IL-6, IL-Ιβ, MIP-2 (PromoCell GmbH, Heidelberg, Germany), IFN-a, IFN-γ, RANTES (R&D Systems, Lille, France), serotonin (BlueGene, Shanghai, China), thromboxane B2 (TXB2; Elabscience, Wuhan, China) and sP-selectin (Qayee-Bio, Shanghai, China). Total protein was evaluated by using the Coomassie Bradford Protein assay kit (Thermo Scientific, Massachusetts, USA).

Mice

Experiments were performed in accordance with the Guide for the Care and Use of

Laboratory Animals of la Direction des Services Veterinaires (DSV), the French regulations to which our animal care and protocol adhered. The license authority was issued by the DSV and Lyon University (accreditation 78-114). Protocols were approved by the Committee on Ethics of Animal Experiments of Lyon University (Permit BH2008-13).

Female, 7-week-old BALB/c mice were used for H7N7 virus infections. Otherwise, 6- week-old C57BL/6 female mice (Charles River Laboratories, Arbresle, France) and GPIIIa^{" '} mice or wild-type littermates on a C57BL/6 background were used in this study. For the latter, heterozygous mice were crossed, and WT and KO offspring (males and females) were used. Polymerase chain reaction of tail-tip genomic DNA was performed (12) to determine the absence or presence of the GPIIIa gene. Infection experiments were performed as previously described (13). Mice were anesthetized with ketamine/xylazine (42.5/5 mg/kg) and inoculated intranasally with IAV, in a volume of 20 μΐ. Eptifibatide was injected intraperitoneally (500 μg/kg or 10 μg/200 μΐ per mouse of -20 g body weight) every 3 days until the end of the experiment. MRS 2179 was dissolved in saline buffer and administered once intravenously (50 mg/kg) on day 0. Clopidogrel dissolved in saline buffer was injected intraperitoneally (30 mg/kg) every day until the end of the experiment. For PAR4 stimulation experiments, mice were anesthetized every day for 3 days. On the first day, the anesthetized mice were infected intranasally in the presence or absence of PAR4-AP or control peptide (100 μg/mouse, in a volume of 20 μΐ). Intranasal peptide treatments were also repeated on days 2 and 3 after infection. For PAR4 antagonist treatment, pepducin p4pal-10 was given intraperitoneally (0.5 mg/kg) two days post-infection, and treatments were repeated on the next two days.

Upon inoculation, the survival rates were followed. Alternatively, mice were sacrificed at prefixed time points to perform BAL or harvest lungs. ELISA was performed according to the manufacturers' instructions. Virus titers were assessed as previously described (14). Lungs were also harvested for histology and immunohistochemistry as previously described (15). Evaluation of hemorrhagic foci by histopathological analysis

Lungs from mice inoculated with A/PR/8/34 virus (250 PFU/mouse) with or without eptifibatide treatment were fixed in 10% neutral buffered formalin and embedded in paraffin. Then, 4-6 μιη sections were cut and stained with hematoxylin and eosin (H&E) to evaluate histopathological changes. Staining was performed by incubation of the lung sections with Harris hematoxylin for 6 min, running tap water for 1 min, eosin Y for 10 min, 70% ethanol for 1 min, 95% ethanol for 1 min, 100% ethanol for 1 min and two rinses in 100% xylene for 1 min. Histology and injury scoring were performed by a blinded investigator who analyzed the samples and determined the levels of injury according to a semiquantitative scoring system (counting inflammatory infiltration, vascular congestion, hemorrhage, fibrin deposits and epithelial cell apoptosis).

Microscopy

For ultrastructural analysis, lung tissues were cut into 1-mm³ pieces, fixed in 2% glutaraldehyde at 4°C, washed in 0.2 M cacodylate-HCl buffer containing 0.4 M saccharose and post-fixed in 0.3 M cacodylate-HCl buffer containing 2% osmium tetroxide for 1 hour. After dehydration in a graded alcohol series, tissue samples were impregnated with a 75% Epon A/25% Epon B/1.7% DMP30 mixture. Tissue embedding entailed polymerization at 60°C for 72 hours. Then, 70-nm sections were cut using a ultramicrotome (Leica Microsystems), mounted on 200-mesh copper grids coated with 1 : 1,000 polylysine, stabilized for 24 hours and contrasted with uranyl acetate/citrate. Sections were examined using a transmission electron microscope (JEOL 1400, Japan) at 80 kV equipped with an Orius SC600 camera (Gatan, France). Immunogold staining was performed using the anti-HA antibody followed by 10 nm gold-conjugated secondary antibody, as previously described (16). As a control of HA labelling, we used IAV particles that we recently purified (17).

Fluorescence microscopy experiments

Cells from the BAL were centrifuged at 1,800 rpm for 5 minutes at room temperature and suspended in phosphate buffer saline (PBS) at a concentration of 5xl0⁵/ml. Then, 100 μΐ of the solution was then used to centrifuge the cells onto coverslips (1,000 rpm for 5 minutes), using a Shandon Cytospin 4 centrifuge. The slides were then dipped in a box containing methanol and kept at -20°C for fixation and permeabilization. After 10 minutes, cells were extensively washed with PBS to remove the fixative. Cells were then incubated with primary antibodies to CD41 and viral HA for 1 hour at room temperature. Revelation was performed using Alexa Fluo® (Life Technologies) secondary antibodies for 1 hour at room temperature. Cells were also counterstained with DAPI for 15 minutes at room temperature. Images were analyzed using a Leica TCS SP5 confocal system (Leica Microsystems).

Evaluation of platelet and leukocyte numbers

Platelets were counted using the Vet ABC™ Hematology Analyzer (SCIL) using the mouse smart card 7030. The automated cell counter differentiates mouse platelets based on their size in multiple sample fluids. Leukocytes and neutrophils in the BAL were visualized by May-Grunwald Giemsa stained cytospin preparations, as previously performed (13). Flow cytometry of blood platelets

Blood was collected in ACD buffer by cardiac puncture. CD41 -positive cells and platelet activation in whole blood were evaluated using FITC-conjugated P-selectin and PE- conjugated CD41/CD61 antibodies, as previously described (18, 19). Statistical analysis

The Kaplan-Meier test was used for survival rates. The Mann- Whitney test was used for two-group comparisons of mean percentages in the flow cytometry experiments, lung virus titers, ELISA and total protein quantifications. One-way ANOVA for non-parametric measures (Kruskal-Wallis) was used for multiple-group comparisons in dose-responses or kinetics experiments. Dunn's multiple comparison test was employed as a post hoc test using NI as a control. Probabilities *p< 0.05, ** p< 0.01 , *** p< 0.001 were considered statistically significant.

Results:

Platelet recruitment to the lungs upon IAV infection

Platelet recruitment to the lungs was first examined after infection of mice with a sublethal or a 50% lethal dose (LD₅₀) of IAV A/PR/8/34. Immunohistochemistry of the lungs, using monoclonal antibodies for IAV nucleoprotein (NP) and CD41, was used to detect virus- infected cells and platelets, respectively (Figure 1A). At both doses, many IAV-infected cells and marked platelet infiltrates were detected in the lungs of infected mice compared to uninfected mice. To confirm these results, platelet counts in the BAL of infected versus uninfected mice (sublethal dose or LD₅₀) were assessed using a blood cell counter (Figure IB). In the BAL of infected mice, the platelet levels increased in a dose-dependent manner and were significantly higher than in those of uninfected mice, reaching 50^χ 10⁹ cells/L on day 6 post-inoculation (LD₅₀). Differences were not significant upon infection with IAV at the sublethal dose. Viral proteins are present within platelets

The presence of viral particles was next determined in platelets from the BAL of infected mice by immunofluorescence staining using the platelet-specific anti-CD41 and viral anti-hemagglutinin (HA) antibodies. Nuclei were counterstained with DAPI. In contrast to uninfected mice (NI), upon infection (LD₅₀), CD41 -positive DAPI-negative platelets stained positively for viral HA, demonstrating that platelets engulfed IAV particles, fragments of IAV or viral proteins in vivo (Figure 1C). CD41-negative/D API-positive cells were used as controls for antibody specificity. To confirm these results, immunogold labeling of ultrathin cryosections of lungs from uninfected or infected mice was performed using a specific anti- HA antibody. Examination of platelets clearly showed a positive and specific staining of viral HA proteins, which were located predominantly within platelet granule-like structures (Figure ID, middle and upper right panels). The sparse staining could have been due to the procedure. Indeed, as a control, we used immunogold labelling of HA on highly purified A/PR/8/34 virus particles (17). Although virions of IAV contain approximatively 500 molecules of HA per virion, few gold particles were observed (Figure ID, lower right panel).

Platelet activation and aggregation

Upon activation, platelets become immobilized, secrete their granule content, and aggregate. Thus, we next analyzed these responses in the lungs of infected mice (sublethal or LD₅₀). Upon activation, serotonin is released from platelet dense granules, and P-selectin is rapidly translocated from the alpha granules to the plasma membrane and shed. Serotonin and soluble P-selectin (sP-selectin) were measured in BAL and plasma, respectively, by ELISA (Figure 2A). Serotonin and sP-selectin were significantly higher in the fluid of infected mice compared to uninfected mice. Significant differences were only observed upon infection with IAV at LD₅₀. Furthermore, exposure of P-selectin on the surface of platelets isolated from IAV-infected mice was increased compared to uninfected mice (Figure 2B, left panel). The average percentage of P-selectin-positive platelets reached 23% upon infection, versus 5% in uninfected mice (Figure 2B, right panel). Moreover, transmission electron microscopy showed that platelets in the lungs of influenza virus-infected mice were tightly packed, forming large extravascular aggregates with signs of shape change. And some platelets were devoid of granules (Figure 2C). In contrast, in the lungs of uninfected mice, only a few isolated platelets were detected.

Platelets contribute to influenza pathogenesis

Platelet GPIIIa^+/" mice were intercrossed to generate wild-type (WT) and platelet

GPIIIa^{" '} mice, which were then infected with IAV A/PR/8/34, and the survival rates were monitored. As shown in Figure 2D, compared to WT mice, GPIIIa ^{~ ~} mice were significantly more resistant to IAV-induced death. Time course of platelet activation, ILl-beta release and platelet binding to leukocytes

Platelets were counted in the BAL of infected mice (LD₅₀) at various times post- inoculation. Upon infection, platelet counts increased in a time-dependent manner (Figure 3 A), peaked on day 3 and stayed elevated until day 8. Plasmatic sP-selectin significantly increased during the course of infection and plateaued on days 3-8 (Figure 3B). Increased ILl-beta was also detected in the BAL and blood of infected mice but with different lags (Figure 3C-D). ILl-beta was released in the BAL paralleled platelet activation, whereas ILl- beta peaked in the blood on day 2 post-inoculation and then rapidly decreased. Ultrastructural analysis of the lungs of A/PR/8/34-infected mice showed that platelet-leukocyte complexes formed in vivo. Neutrophils and monocytes were associated with platelet aggregates, although not all platelet adhered to leukocytes (Figure 3E).

PAR4 promotes pathogenesis of IAV infection in a platelet-dependent pathway

Mice were inoculated with a sublethal dose of IAV A/PR/8/34 and stimulated with 100 μg/mouse of the PAR4 agonist peptide AYPGKF-NH₂ (PAR4-AP) or the inactive control peptide YAPGKF-NH₂ (Control-P). As expected, treatment with PAR4-AP increased platelet activation, as observed by increased serotonin and soluble P-selectin in the BAL and plasma of infected mice (Figure 4A). More interestingly, upon infection, mice treated with PAR4-AP displayed significantly higher mortality rates compared with mice treated with Control-P (Figure 4B). In contrast, treatment with PA 4-AP did not affect the survival of uninfected mice. The effect was platelet dependent, as treatment of mice with eptifibatide abrogated the deleterious effect of PA 4-AP (Figure 4C), as did the platelet GPIIIa deficiency (Figure 4D). No significant differences in lung virus titer were observed 3 or 6 days post-inoculation between mice treated with PAR4-AP and those treated with Control-P (Figure 4E). However, on day 6, treatment with PAR4-AP significantly increased total proteins in the BAL (Figure 4F). The response levels of IL-6, IL-Ιβ and MIP-2 were also enhanced, while those of interferon (IFN)-y, RANTES and KC were unaffected (Figure 5A). On day 3, no difference was observed. Thus, PAR4 activation promoted IAV-induced inflammation of the lungs at later time points post-infection. Similarly, staining of lung sections on day 6 revealed marked cellular infiltrates of leukocytes (HE) and neutrophils (Ly6G) in the lungs of PAR4-AP- treated mice compared to controls (Figure 5B). Similar numbers of IAV-infected cells were detected by immunohistochemistry using an anti-NP antibody. No staining was observed in the lungs of uninfected control mice.

PAR4 antagonism protects against influenza virus pathogenicity

When mice were infected with IAV A/PR/8/34 (LD₅₀), treatment with pepducin p4pal- 10 protected them from death (Figure 6A). Substantial protection was also observed against infection with an H3N2 virus, A/HK/1/68. The protection conferred by PAR4 antagonism correlated with the degree of inhibition of platelet activation. In the BAL of pepducin p4pal- 10-treated mice, decreased thromboxane B2 (TXB2), a specific marker of platelet activation, was observed (Figure 6B). In contrast, no difference in the mean lung virus titers was detected on day 3 or 6 after inoculation with IAV A/PR/8/34 (Figure 6C). However, treatment with pepducin p4pal-10 significantly reduced the recruitment of leukocytes (Figure 6D), including neutrophils, in BAL on day 6. Total proteins (Figure 6E) and IL-6, IL-Ιβ and MIP-2 (Figure 6F) were also decreased. Consistent with those results, histopathology revealed that treatment with pepducin p4pal-10 reduced infiltration of inflammatory cells (HE), including neutrophils (Ly6G), in the lungs of infected mice (Figure 6G), while similar numbers of IAV-infected cells (NP) were detected by immunohistochemistry.

The anti-platelet drug eptifibatide protects mice from lethal influenza infection

Mice were inoculated with IAV A/PR/8/34 (LD₅₀) and were treated or not with 500 μg/kg of eptifibatide every 3 days. This dosage is comparable to the lowest doses used clinically in humans (20-22). Eptifibatide treatment had a dramatic effect on lung infiltration by platelets: platelet aggregation was totally prevented, and only isolated platelets were observed (Figure 7A). Furthermore, this effect was accompanied by decreases in TXB2 and sP-selectin in the fluid of infected mice compared to controls (Figure 7B), showing that inhibition of platelet aggregation also limited the extent of platelet activation. More importantly, treatment with eptifibatide improved the outcome of infection with A/PR/8/34 virus and prevented mortality of the mice (Figure 7C). Protection was also observed with other influenza strains. No effect of eptifibatide was observed in GPIIIa^{" '} mice (Figure 8A), showing the specificity of the drug.

The protective effect of eptifibatide was independent of virus replication in lungs (Figure 8B) and IFN-g release in the BAL (Figure 8C). In contrast, it was correlated with decreased total proteins and levels of certain cytokines in the BAL of eptifibatide-treated mice compared to controls (Figure 8D-E). Immunohistochemistry confirmed that treatment by eptifibatide prevented IAV-induced lung alveolar damage (HE) and neutrophil infiltration (Ly6G) but not viral replication (NP) on day 6 post-infection (Figure 8F). This effect was not observed on day 2 (data not shown). Treatment of infected mice with MRS 2179 and clopidogrel, which inhibits the ADP receptors P2Y1 and P2Y12, improved the outcome of IAV infection (Figure 8G).

Eptifibatide treatment protects mice from hemorrhage induced by influenza

Histopathological analyses of lung tissues were performed to evaluate the extent of hemorrhage after eptifibatide treatment. Mice were infected with A/PR/8/34 virus and treated with eptifibatide or vehicle, and lungs were then harvested 6 days post-inoculation for histopathology. In the infected group, lungs presented signs of congestion with infiltration of neutrophils and monocytes, interstitial and alveolar hemorrhages, as well as thrombosis (Figure 9A). Fibrin and erythrocyte-rich thrombi were observed in small vessels. Figure 9B summarizes the blinded semi-quantitative scoring of the different parameters. Eptifibatide markedly reduced the severity of pulmonary injury induced by influenza virus infections, and a marked reduction in neutrophil infiltration was observed. (Figure 9A-B). More importantly, almost no hemorrhage was detected in the lungs of infected mice treated with eptifibatide.

Disccusion:

The present study shows that platelets play an active role in fueling the dysregulation of inflammation and promoting pathogenesis of influenza virus infections. Histological analysis of lungs provided evidence that platelets massively infiltrate the lungs of infected mice. Additionally, infiltrated platelets stained positive for viral HA, based on immunofluorescence staining of BAL and immunogold labeling of ultrathin cryosections of lungs. The technical limitation of the staining did not allow us to determine whether platelets engulfed the entire virions, only IAV fragments or antigens. However, because platelets incorporate influenza viruses in vitro (23), our results suggest that platelets recruited to the lungs most likely take up IAV particles in vivo as well. This could consist of a passive passage of particles through the open canalicular system, the tortuous invaginations of platelet surface membranes tunneling through the cytoplasm, in a manner similar to bacterial ingestion (24). Alternatively, uptake of IAVs may be compared to phagocytosis by macrophages and neutrophils, as previously observed for human immunodeficiency viruses (25).

Ultrastructural analysis showed that features of platelets in the lungs of infected mice are those of aggregates of activated platelets: platelets were tightly stacked without interplatelet spaces, and some platelets were devoid of granules, suggesting that they had degranulated. Consistent with those observations, markers of platelet activation were detected in the BAL and plasma of infected mice. Thus, upon lethal IAV infection, platelets are activated in the lung and in the peripheral circulation. Our observations are consistent with the recent findings that influenza virus activates platelets through FcyRIIA signaling or thrombin generation (26). Thrombin triggers the release of serotonin and TXA2 from platelets, promotes P-selectin translocation to the platelet plasma membrane and activates the GPIIb/IIIa complex (27).

Platelets contribute to the host defense against bacterial infectious agents by limiting vascular lesions and inducing injury repair (28, 29). However, unbalanced platelet activation may have pathological consequences. In our influenza model, platelet activation and aggregation were deleterious. PAR4 and GPIIIa are both key molecules in platelet function. PAR4 is strictly required for platelet activation in mice, while GPIIIa is required for platelet aggregation. First, mice deficient in GPIIIa were protected from lung injury and death. Furthermore, stimulation of PAR4 increased lung inflammation and the severity of IAV infection. In contrast, PAR4 antagonists protected mice from death. Our results indicate that PAR4 acts through platelet activation because the effect of PAR4-AP was abrogated when infected mice were treated with the platelet specific inhibitor eptifibatide (30), or when mice were deficient in platelet GPIIIa protein. Altogether, the data indicate that platelets regulate IAV pathogenesis. Interestingly, the observation by others that influenza virus activates platelets through thrombin generation (26) suggests that thrombin may also act in a deleterious manner against IAV infection. Thrombin mediates signal transduction mainly by activating PA 4 and PARI (31, 32). Because mouse platelets do not express PARI, thrombin-mediated platelet activation most likely occurs through PAR4 activation, but thrombin activation of PARI may also be involved in the pathogenesis of IAV infection. Indeed, we recently found that PARI signaling contributes to IAV pathogenicity in mice (33). In this context, PARI cooperates with plasminogen, which controls pathogenesis, via fibrinolysis (34). Thus, investigations into the role of hemostasis dysregulation may help better understand IAV pathogenesis (35-37).

In several models of injury, uncontrolled platelet activation drives deleterious inflammation (38). Activated platelets release an arsenal of potent pro -inflammatory molecules (39), which exacerbate neutrophil rolling, adhesion and recruitment (40-42). In addition, the physical interaction between platelets and neutrophils further contributes to neutrophil retention and activation (42). Because dysregulation of inflammation is a hallmark of severe influenza virus infections, it is likely that platelets have a pro -inflammatory effect with a key role in IAV pathogenesis. In our study, electron microscopy demonstrated the presence of neutrophil-platelet complexes in IAV infected mice. The anti-platelet molecule eptifibatide inhibited neutrophil recruitment into inflamed lungs (Figure 9). Thus, platelet interaction with neutrophils is likely to play a role during severe inflammation induced by influenza.

Interestingly, the exacerbation of cytokine production induced by platelet activation was only observed at later time points after infection. Upon infection, the virus is recognized as foreign by highly conserved receptors known as pattern recognition receptors. Activation of these receptors results in the secretion of cytokines and chemokines, which corresponds to the early inflammatory response against IAV infection (35). Thus, the amplification and intensity of inflammation depends on the replicative capacity of the virus. When the response is tightly controlled, a resolution phase of inflammation is engaged at later time points postinfection, and this partly determines the duration of inflammation. Resolution of inflammation is largely influenced by the vascular endothelium (43). Upon injury of the latter, platelets are activated. Our data show coordinated platelet activation/aggregation and inflammatory responses at late time points post-infection, indicating that platelets may affect the recovery phase after infection and wound healing. In this scenario, extravasation of large numbers of platelets and leukocytes would be the basis of the defect in the resolution phase of the inflammation. Most likely, this further promotes hemostasis dysregulation, such as fibrinolysis (18, 44) or PARI activation (33, 45), fueling the vicious circle of inflammation (34, 35).

Recurrent outbreaks of IAV that cause severe infections in humans have raised serious concerns about therapeutic strategies available for these pathogens. Current treatments that target viral proteins have a number of disadvantages, including the rapid development of resistant virus variants as a result of selective pressure (46, 47). Because targeting the host rather than the virus would not easily lead to resistance, drugs regulating inflammation are appealing as potential new therapeutics for IAV symptoms (13, 33, 34, 48). Here, we found that available anti-platelet drugs efficiently protected mice from IAV pathogenesis induced by several influenza strains. These results are consistent with other studies showing that aspirin, known to inhibit platelet activation, blocks IAV propagation via NF-kB inhibition (49). Altogether, these results suggest that anti-platelet drugs might be explored as new antiinflammatory treatments against severe influenza. REFERENCES:

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Claims

CLAIMS:

1. A method for the treatment of influenza A virus (IAV) infection in a subject in need thereof comprising administering the subject with a therapeutically effective amount of at least one anti-platelet agent, provided that the anti-platelet agent is not a PAR-1 antagonist, no aspirin.

2. The method of claim 1 wherein the IAV infection is caused by influenza virus A that is H1N1, H2N2, H3N2 or H5N1.

3. The method of claim 1 wherein the subject is a human such as a human infant, a human child, a human adult or an elderly human.

4. The method of claim 1 wherein the anti-platelet agent is selected from the group consisting of GPIIb/IIIa antagonists, thromboxane- A2 -receptor antagonists, thromboxane- A2-synthetase inhibitors, phosphodiesterase-III (PDE-III) inhibitors, and PDE V inhibitors), and pharmaceutically acceptable salts or prodrugs thereof.

5. The method of claim 1 wherein the anti-platelet agent is eptifibatide.

6. The method of claim 1 wherein the anti-platelet agent is selected from the group consisting of ADP (adenosine diphosphate) receptor antagonists, such as antagonists of the purinergic receptors P2Y1 and P2Y12.

7. The method of claim 6 wherein the P2Y12 receptor antagonists include ticlopidine, clopidogrel, Prasugrel, AR-C69931MX, Cangrelor, MRS2179 1 and pharmaceutically acceptable salts or prodrugs thereof.

8. The method of claim 1 wherein the anti-platelet agent is a PAR-4 antagonist.

9. The method of claim 8 wherein the PAR-4 antagonist is a small organic molecule.

10. The method of claim 9 wherein the PAR4 antagonists is ethyl 4-(l- benzyl- lH-indazol- 3-yl)benzoate.

11. The method of claim 8 wherein the PAR4 antagonist is selected from the group consisting of pepducins.

12. The method of claim 1 wherein the anti-platelet agent is an antibody which acts as a GPIIb/IIIa antagonist, a thromboxane-A2 -receptor antagonist, an ADP receptor antagonist, or a PAR4 antagonist.

13. The method of claim 1 wherein the anti-platelet agent is an inhibitor of gene expression wherein the gene is selected from the group of genes encoding for GPIIb/IIIa receptort, a thromboxane-A2 -receptor, an ADP (adenosine diphosphate) receptor, or PAR4.

14. The method of claim 1 wherein the anti-platelet agent is administered to the subject in combination with a least one further agent selected from the group consisting of neuraminidase inhibitor, M2 inhibitors, RNA polymerase inhibitors and interferons.