Mechanisms of varicella virus dissemination

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SUMMARY Varicella zoster virus (VZV) is a highly contagious, neurotropic alpha herpes virus that causes varicella (chickenpox). VZV establishes latency in the sensory ganglia from which it can reactivate to cause herpes zoster (shingles), a painful disease that affects almost 1 million individuals in the United States annually. During primary infection VZV is transmitted through the inhalation of viral particles, but the mechanisms by which VZV traffics from the initial site of infection to the ganglia and skin remain unclear. Data from in vitro assays as well as in vivo studies using severe- combined immunodeficient mice implanted with human fetal tissues (SCID-hu) strongly suggest that T cells are highly susceptible to VZV infection and may play a critical role in VZV dissemination to the skin and ganglia. However, the SCID-hu mouse model has two major limitations: 1) the lack of an adaptive immune system and 2) the possibility that the strict human host specificity of VZV could have altered viral behavior in this murine model. Additionally, in vitro studies of human tonsillar T cells were carried out using the attenuated Oka vaccine strain, which may not adequately model the outcome of infection with wild type viral strains. In this application, we propose to define the mechanisms by which VZV usurps T cells to spread by using a rhesus macaque model that recapitulates the hallmarks of VZV infection. In this model, rhesus macaques are intra-bronchially infected with Simian varicella virus (SVV), a homolog of VZV. We have demonstrated that lung-resident T cells are susceptible and permissive to SVV infection. Additionally, memory T cells are detected in the ganglia as early as 3 days post-infection, at the same time as viral DNA and before the detection of a viral-specific T cell response. Although these observations establish a significant role for T cells in SVV spread to the ganglia, as has been suggested for VZV, the mechanism by which varicella viruses hijack the host’s T cells to disseminate to latency sites remain poorly defined. In this application, we will address this critical knowledge gap by first identifying transcriptional changes induced by SVV infection in T cells isolated from the lung during acute infection using high throughput single cell RNA sequencing. Then, we will assess alterations in metabolic and migratory function of SVV- infected T cells in vitro. Completion of the studies proposed in this application will yield novel insight into viral-host interactions at the single cell level and will serve as a model to investigate the pathogenesis of other T cell tropic viruses.