Oncolytic Viruses as a Potential Approach to Eliminate Cells That Constitute the Latent HIV Reservoir

Abstract

HIV infection represents a major health and socioeconomic challenge worldwide. Despite significant advances in therapy, a cure for HIV continues to be elusive. The design of novel curative strategies will require targeting and elimination of cells that constitute the latent HIV-1 reservoir. However, such an approach is impeded by the inability to distinguish latently HIV-infected cells from uninfected cells. The type-I interferon (IFN-I) response is an integral antiviral defense mechanism, but is impaired at multiple levels during productive HIV infection. Interestingly, similar global impairments in IFN-I signaling have been observed in various human cancers. This led to the development of IFN-sensitive oncolytic viruses, including the recombinant Vesicular Stomatitis Virus (VSV 51) and Maraba virus (MG1), as virotherapy designed to treat various cancers. Based on this, it was hypothesized that IFN-I signaling is impaired in latently HIV-infected cells (as observed in productively infected cells) and that VSV 51 and MG1 may be able to exploit such intracellular defects to target and eliminate latently HIV-infected cells, while sparing healthy cells. First, using cell line models of HIV-1 latency, intracellular defects in IFN-I responses, including impaired IFN / production and expression of IFNAR1, MHC-I, ISG15, and PKR, were demonstrated to represent an important feature of latently HIV-infected cells. Consistent with this, the latently HIV-infected cell lines were observed to have a greater sensitivity to VSV 51 and MG1 infection, and MG1-mediated killing, than the HIV-uninfected parental cells. Next, the ability of oncolytic viruses to kill latently HIV-infected human primary cells was demonstrated using an in vitro resting CD4+ T cell model of latency. Interestingly, while both VSV 51 and MG1 infection resulted in a significant reduction in inducible p24 expression, a dose-dependent decrease in integrated HIV-1 DNA was only observed following MG1 infection. In keeping with this, MG1 infection of memory CD4+ T cells from HIV-1 infected individuals on HAART also resulted in a significant decrease in inducible HIV-1 gag RNA expression. By targeting an intracellular pathway that is impaired in latently HIV-infected cells, the findings presented in this dissertation highlight a novel, proof-of-concept approach to eliminate the latent HIV-1 reservoir. Given that VSV 51 and MG1 are currently being studied in cancer clinical trials, there is significant potential to translate this work to in vivo studies.