Therapeutic targets in gammaherpesvirus infection

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PROJECT SUMMARY The human gammaherpesviruses (γHVs) Kaposi's sarcoma associated herpesvirus and Epstein-Barr virus are DNA tumor viruses that establish a lifelong infection. These viruses are strongly associated with pathogenic outcomes in immune suppression, including the AIDS defining malignancies Kaposi's sarcoma and non- Hodgkin lymphoma. A major challenge of the γHVs is that these viruses present a lifelong risk for viral re- emergence and pathogenesis, especially in the context of acquired or medically-induced immunosuppression. Lifelong infection is further confounded by the limited therapeutic interventions against γHV diseases. To date, the best defense against γHV-induced disease is an intact immune system. Despite this correlation, there remain major knowledge gaps in our understanding of: 1) protective aspects of successful vaccination to γHV infection, and 2) consequence of vaccination on the composition and frequency of infected cells, either before or after established infection. In this R01 application, we seek to investigate how vaccination alters γHV infection, using murine gammaherpesvirus 68 (γHV68), a mouse model of γHV infection, that facilitates study of infection and associated responses from primary infection through lifelong latency and re-emergence of lytic infection. We recently undertook studies to characterize how latency is regulated by viral and host factors at the single-cell level, identifying that the latent pool is heterogeneous based on expression of the latency- associated nuclear antigen (LANA), and that the proportion of LANA+ latently-infected cells is subject to regulation. These studies further identified that CD8 T cells, and the cytokine interferon-gamma, limit LANA+ latently-infected B cells, and that vaccination with a live-attenuated vaccine is capable of profoundly restricting LANA+ latent B cell infection in an interferon-gamma-independent manner. We now seek to investigate the role of myeloid cells in infection and vaccination on γHV infection both in vitro and in vivo. We will make use of vaccination protocols with defined differences in efficacy to identify the critical features using single cell analysis and high dimensional methods to distinguish the features of vaccine efficacy. We hypothesize that vaccination with a live-attenuated vaccine induces: 1) local and systemic myeloid reprogramming, which 2) redirects γHV myeloid infection into an immune-susceptible myeloid target. We will test this in three aims. First, we will analyze the impact of vaccination on local and systemic myeloid cells. Second, define how vaccination affects primary γHV infection of myeloid cells. Third, dissect how viral tropism is influenced by vaccine-induced effector mechanisms. By analyzing specific viral and host processes in the context of vaccines with varying efficacy, this proposal seeks to investigate myeloid reprogramming as a necessary, and therapeutically viable, target for vaccination against γHV latency.