Suppressor of Cytokine Signaling (SOCS)1 and SOCS3 Stimulation during Experimental Cytomegalovirus Retinitis: Virologic, Immunologic, or Pathologic Mechanisms

AIDS-related human cytomegalovirus (HCMV) retinitis remains the leading cause of blindness among untreated HIV/AIDS patients worldwide. Understanding the pathogenesis of this disease is essential for developing new, safe, and effective treatments for its prevention or management, yet much remains unknown about the virologic and immunologic mechanisms contributing to its pathology. To study such mechanisms, we use a well-established, reproducible, and clinically relevant animal model with retrovirus-induced murine acquired immunodeficiency syndrome (MAIDS) that mimics in mice the symptoms and progression of AIDS in humans. Over 8 to 12 weeks, MAIDS mice become susceptible to experimental murine cytomegalovirus (MCMV) retinitis. We have found in this model that MCMV infection significantly stimulates ocular suppressor of cytokine signaling (SOCS)1 and SOCS3, host proteins which dampen immune-related signaling by cytokines, including antiviral interferons. Herein we investigated virologic and/or immunologic mechanisms involved in this stimulation and how virally-modulated SOCS1 and/or SOCS3 proteins may contribute to MCMV infection or experimental MAIDS-related MCMV retinitis. Through pursuit of two specific aims, we tested the central hypothesis that MCMV stimulates and employs SOCS1 and/or SOCS3 to induce the onset and development of MCMV retinal disease. MCMV-related SOCS1 and SOCS3 stimulation in vivo occurred with intraocular infection, was dependent on method and stage of immune suppression and severity of ocular pathology, was associated with stimulation of SOCSinducing cytokines, and SOCS1 and SOCS3 were differentially sensitive to antiviral treatment. In vitro studies further demonstrated that SOCS1 and SOCS3 stimulation during MCMV infection occurred with expected immediate early kinetics, required viral gene expression in celltype-dependent and virus origin-dependent patterns of expression, and displayed differential sensitivity to antiviral treatment. These data suggest that SOCS1 and SOCS3 are stimulated by divergent virologic, immunologic, and/or pathologic mechanisms during MCMV infection, and that they contribute to the pathogenesis of retinal disease, revealing new insights into the pathophysiology of AIDS-related HCMV retinitis. INDEX WORDS: Cytomegalovirus retinitis, human cytomegalovirus (HCMV), HIV/AIDS, suppressors of cytokine signaling (SOCS), murine cytomegalovirus (MCMV), murine AIDS (MAIDS) SUPPRESSOR OF CYTOKINE SIGNALING (SOCS)1 AND SOCS3 STIMULATION DURING EXPERIMENTAL CYTOMEGALOVIRUS RETINITIS: VIROLOGIC, IMMUNOLOGIC, OR PATHOLOGIC MECHANISMS