HIV-1 replication in gut-associated lymphoid tissue (GALT) in the early stages of infection results in massive depletion of mucosal effector CD4+ T cells, in particular IL-17-producing CD4+ T cells (Th17). Depletion of Th17 cells leads to bacterial translocation from the lumen into the lamina propria (LP) and subsequently the circulation, a process associated with increased immune activation and inflammation. Thus, understanding how HIV-1 induces GALT CD4+ T cell death may be key to preventing the inflammatory sequelae of HIV- 1 infection. However, the mechanism by which HIV-1 kills CD4+ T cells remains one of the most critical unanswered questions in basic HIV/AIDS research. Despite extensive published studies on the subject, most prior CD4+ T cell killing studies utilized X4-tropic HIV-1 strains and cell types that are not directly relevant to understanding CD4+ T cell depletion in mucosal compartments. To address this issue, we recently developed a novel experimental system to model the interactions between R5-tropic HIV-1, microbial species and LP CD4+ Th cell subsets ex vivo using primary intestinal mucosal cells. Thus, our collaborative team is in a unique position to address the following critical knowledge gaps in HIV-1 mucosal immunopathogenesis: 1. How does R5-tropic HIV-1 cause GALT CD4+ T cell death? 2. How do translocating enteric bacteria influence HIV-mediated GALT CD4+ T cell killing? 3. Which viral determinants mediate GALT CD4+ T death by transmitted/founder HIV-1 strains? Using our dynamic ex vivo LP infection model, we propose three specific aims to address these important questions.
In Aim 1, we will utilize differentially-labeled HIV-1 infected and uninfected cells to investigate the role of PCD pathways in HIV-1 mediated CD4+ T cell death by counteracting caspase activity, inhibiting HIV-1 at discrete steps in its life cycle, and using non-biased gene expression profiling.
In Aim 2, we will determine the biological impact of representative gut bacterial species individually, and in combination, on HIV-1 mediated LP CD4+ T cell death and identify the immunomodulatory properties of bacteria that influence CD4+ T cell depletion.
In Aim 3, we will document the replication and killing characteristics of a panel of 40 Transmitted/Founder and chronic HIV-1 Subtype B and C infectious molecular clones, to define the viral characteristics responsible for LP CD4+ T cell death. The results of these studies may ultimately provide insight into pathways that can be targeted to preserve or restore the integrity of the mucosal immune system in HIV- infected patients and thereby limit systemic inflammation and its downstream consequences.

Public Health Relevance

HIV targets and kills lymphocytes that line the intestine, which leads to a state of chronic inflammation. The purpose of this grant is to understand how HIV kills lymphocytes in the intestine in order to find new ways to block chronic inflammation in HIV-infected persons.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
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AIDS Immunology and Pathogenesis Study Section (AIP)
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Lawrence, Diane M
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University of Colorado Denver
Internal Medicine/Medicine
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United States
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Dillon, Stephanie M; Kibbie, Jon; Lee, Eric J et al. (2017) Low abundance of colonic butyrate-producing bacteria in HIV infection is associated with microbial translocation and immune activation. AIDS 31:511-521
Dillon, S M; Lee, E J; Kotter, C V et al. (2016) Gut dendritic cell activation links an altered colonic microbiome to mucosal and systemic T-cell activation in untreated HIV-1 infection. Mucosal Immunol 9:24-37
Dillon, Stephanie M; Lee, Eric J; Donovan, Andrew M et al. (2016) Enhancement of HIV-1 infection and intestinal CD4+ T cell depletion ex vivo by gut microbes altered during chronic HIV-1 infection. Retrovirology 13:5
Dillon, Stephanie M; Frank, Daniel N; Wilson, Cara C (2016) The gut microbiome and HIV-1 pathogenesis: a two-way street. AIDS 30:2737-2751
Harper, Michael S; Guo, Kejun; Gibbert, Kathrin et al. (2015) Interferon-? Subtypes in an Ex Vivo Model of Acute HIV-1 Infection: Expression, Potency and Effector Mechanisms. PLoS Pathog 11:e1005254
Steele, Amanda K; Lee, Eric J; Manuzak, Jennifer A et al. (2014) Microbial exposure alters HIV-1-induced mucosal CD4+ T cell death pathways Ex vivo. Retrovirology 11:14
Dillon, S M; Lee, E J; Kotter, C V et al. (2014) An altered intestinal mucosal microbiome in HIV-1 infection is associated with mucosal and systemic immune activation and endotoxemia. Mucosal Immunol 7:983-94