Scientific Report 2007

Molecular and Experimental Medicine

Division of Experimental Pathology

Reduction in the Severity of Liver Disease by Antiplatelet Therapy in a Mouse Model of Acute Viral Hepatitis

L.G. Guidotti, M. Iannacone, G. Sitia, Z.M. Ruggeri

Using mice acutely infected with RAd35, a hepatotropic, replication-deficient, lacZ-expressing adenovirus, we recently showed that platelets accumulate within the inflamed liver and that their depletion diminishes disease severity by reducing the intrahepatic number of both RAd35-specific cytotoxic T lymphocytes and RAd35-nonspecific inflammatory lymphocytes that the T cells help recruit. Transfusion of normal, but not activation-blocked, platelets into thrombocytopenic animals restored these events, indicating that platelet activation plays a crucial pathogenetic role in this model.

In other studies, aspirin and clopidogrel, 2 drugs that target the proactivating functions of the platelet agonists thromboxane A₂ and ADP, respectively, profoundly reduced both liver injury and recruitment of cytotoxic T lymphocytes and inflammatory intrahepatic lymphocytes when the drugs were administered together to RAd35-infected mice previously immunized with lacZ. Besides impairing platelet function, aspirin and clopidogrel also prevented viral clearance from the liver and caused neither bleeding nor anemia. These same drugs were somewhat less efficient at diminishing liver injury when administered separately.

Thus, antiplatelet therapy diminishes immune-mediated liver disease in a model of acute viral hepatitis. This notion may help in devising new approaches to limit excessive liver immunopathologic changes (as during fulminant hepatitis in humans) or delay viral clearance (as demanded by gene therapy–based procedures with these and other hepatotropic viral vectors).

Platelet-Mediated Viral Clearance and Protection From Lethal Hemorrhage in Mice Infected With Lymphocytic Choriomeningitis Virus

L.G. Guidotti, M. Iannacone, G. Sitia, M. Isogawa, J.K. Whitmire,* P. Marchese, F.V. Chisari, Z.M. Ruggeri

* Department of Molecular and Integrative Neurosciences, Scripps Research

We found that infection of mice with different isolates of lymphocytic choriomeningitis virus (LCMV) induced a mild hemorrhagic anemia, which became severe and eventually lethal in animals depleted of platelets or lacking integrin β₃. Lethal hemorrhagic anemia is mediated by virus-induced IFN-α/β that causes platelet dysfunction, mucocutaneous blood loss, and suppression of erythropoiesis. In addition, platelet-depleted mice did not mount an efficient cytotoxic T-lymphocyte response and did not clear LCMV from liver, spleen, and other infected organs, including the brain. Transfusion of functional platelets into these animals reduced hemorrhage, thereby preventing death, and restored viral clearance induced by cytotoxic T lymphocytes in a manner partially dependent on CD40 ligand. These results indicate that upon activation, platelets expressing integrin β₃ and CD40 ligand are required for protecting the host against the induction of an IFN-α/β–dependent lethal hemorrhagic diathesis and for clearing LCMV infection via cytotoxic T lymphocytes.

Publications

Brown, B.D., Sitia, G., Annoni, A., Hauben, E., Sergi, L.S., Zingale, A., Roncarolo, M.G., Guidotti, L.G., Naldini, L. In vivo administration of lentiviral vectors triggers a type I interferon response that restricts hepatocyte gene transfer and promotes vector clearance. Blood 109:2797, 2007.

Iannacone, M., Sitia, G., Ruggeri, Z.M., Guidotti, L.G. HBV pathogenesis in animal models: recent advances on the role of platelets. J. Hepatol. 46:719, 2007.

Pulitanò, C., Sitia, G., Aldrighetti, L., Finazzi, R., Arru, M., Catena, M., Guidotti, L.G., Ferla, G. Reduced severity of liver ischemia/reperfusion injury following hepatic resection in humans is associated with enhanced intrahepatic expression of Th2 cytokines. Hepatol. Res. 36:20, 2006.

Sitia, G., De Bona, A., Bagaglio, S., Galli, L., Paties, C., Uberti-Foppa, C., Guidotti, L.G., Lazzarin, A., Morsica, G. Naive HIV/HCV-coinfected patients have higher intrahepatic pro-inflammatory cytokines than coinfected patients treated with antiretroviral therapy. Antivir. Ther. 11:385, 2006.

Sitia, G., Iannacone, M., Müller, S., Bianchi, M.E., Guidotti, L.G. Treatment with HMGB1 inhibitors diminishes CTL-induced liver disease in HBV transgenic mice. J. Leukoc. Biol. 81:100, 2007.

Trifari, S., Sitia, G., Aiuti, A., Scaramuzza, S., Marangoni, F., Guidotti, L.G., Martino, S., Saracco, P., Notarangelo, L.D., Roncarolo, M.G., Dupré, L. Defective Th1 cytokine gene transcription in CD4⁺ and CD8⁺ T cells from Wiskott-Aldrich syndrome patients. J. Immunol. 177:7451, 2006.