Elimination of persistently HIV-infected cells by targeting host factors

Wallet, Mark

Abstract

A cure for HIV-1 now seems achievable and the primary objective of this study is to contribute to a cure by identifying novel strategies to eliminate persistently-infected cellsor prevent persistent/latent infection of cells. HIV persistence in host cells (CD4+ T cells and macrophages) is a major obstacle to a cure because current therapies only target viral replication, leaving a reservoir of persistently-infected cells that carry the HIV genome for as long as those cells survive. We will focus on the role of HIV-infected macrophages as a reservoir for persistent HIV infection and as a key player in causing latent infection of CD4+ T cells. To achieve our goal, we will pursue three interrelated aims.
Each aim will focus on unique strategies to either eliminate HIV-infected macrophages or prevent HIV-infected macrophages from driving HIV latency in CD4+ T cells.
Aim 1 will investigate the role of two genes/proteins, USP18 and ISG15, in HIV budding. Budding, the mechanism by which HIV leaves an infected cell, is controlled by host and viral proteins. We propose a novel role for USP18 in allowing HIV budding to occur. We predict that disruption of USP18 activity will prevent HIV budding leading to accumulation of intracellular pro-apoptotic viral proteins, which alone or in combination with other strategies will cause death of infected macrophages. We will use over-expression or gene silencing with shRNAs to determine the role of USP18 in HIV budding and survival of HIV-infected macrophages. Macrophages efficiently degrade and recycle intracellular proteins through proteasome or lysosome pathways. In conjunction with disrupted HIV budding, we will inhibit protein recycling to enhance accumulation of HIV proteins to increase cytotoxic cell death.
Aim 2 will investigate how cellular genes/proteins regulate the rate of HIV replication in macrophages. By identifying factors that inhibit or enhance HIV gene expression, protein translation or budding, we will identify additional vulnerabilities that can be exploited to kill HV-infected macrophages. When paired with a strategy to prevent HIV budding and/or HIV protein recycling, enhanced HIV replication will augment cell stress leading to death of HIV-infected macrophages.
Aim 3 will study the role of HIV-infected macrophages in driving latent infection of CD4+ T cells. We have identified unique phenotypic changes to HIV-infected macrophages that include specific outcomes likely to support latent infection of CD4+ T cells. Two pathways of latency will be studied including a mechanism to cause growth arrest of HIV-infected CD4+ T cells and a mechanism to enhance HIV infection of resting CD4+ T cells. Together these three aims provide a comprehensive strategy to identify/exploit unique properties of HIV- infected macrophages to disrupt biological pathways of persistent/latent infection.

Public Health Relevance

HIV-1 infection remains a major global health challenge with millions of deaths each year and billions of dollars in health care costs. We propose here to contribute to a cure for this deadly virus by identifying novel strategies to eliminate the cells which are persistently infected with HIV or to disrupt biological processes that lead to persistent infection. Combined with complementary strategies to prevent HIV replication with antiretroviral drugs, elimination of persistently infected cells holds the key to curing HIV infection.