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 SOCS-inducing 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 cell-type-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.

No description available.

[Truncated abstract] In the last ten years regulator T (Tr) cells have re-emerged as an integral part of the immune system. Research in this field has rapidly demonstrated the role of these cells in the maintenance of immune homeostasis and their involvement in disease. Tr cells are generated in the thymus as a normal part of the developing immune system. Furthermore, antigen-specific Tr cells are induced in the periphery by a mechanism which is yet to be completely elucidated, but is likely to involve dendritic cells. Tr cells play an important role in autoimmune disease, transplantation tolerance, cancer. Most recently Tr cell involvement has been demonstrated in a growing number of infectious diseases. Tr cell induction was reported in Friend Virus infection at the commencement of this study, and subsequent to publication of our findings have also been identified in FIV and HIV. Murine AIDS (MAIDS) is a fatal chronic retroviral infection induced in susceptible strains of mice by infection with BM5d, a replication defective virus, in a viral mixture which is designated LP-BM5. The manipulation of Tr cells detailed in this thesis and the related publication represent the first reported therapy utilising targeted removal of Tr cells. Chapter 1 summarises the literature relevant to this study up to November 2004. Chapter 2 details the materials and methodologies used in this work. Chapter 3 investigates whether Tr cells are involved in the development of murine AIDS, particularly in the early stages of infection. The data presented in this chapter provides evidence of a population of CD4+ Tr cells which express CD25 on their cell surface and secrete TGF-β, some IL-10 and low levels of IL-4 are induced following infection with LP-BM5. These cells were found to arise by day 12 post infection (pi) by flow cytometry and immunosuppressive cytokine expression was found to peak at day 16 pi indicating a role in the early stages of disease progression. Chapter 4 investigates the effect of therapeutically targeting these induced Tr cells using the antimitotic agent Vinblastine during their induction period. The efficacy of treatment was found to be time dependent and was shown to abrogate disease progression maximally when given at day 14 pi. Treatment with anti-CD4 monoclonal antibody was also found to be efficacious at day 14 pi and confirmed the identity of the Tr cells as being CD4+ T cells. Adoptive transfer studies demonstrated that the return of these cells to a successfully treated host results in renewed MAIDS progression, confirming their role in disease progression