• Angiogenin Inhibits Human Immunodeficiency Virus type 1 (HIV-1) Replication in Peripheral Blood Mononuclear Cells by a Complex Mechanism that Includes an Intracellular Component

      Lin, Ping-Hsin; Garzino-Demo, Alfredo (2012)
      Angiogenin (ANG, also known as ribonuclease 5) is a 14.1kDa polypeptide secreted by T lymphocytes and epithelial cells. Other than its well-characterized function of promoting development of vasculature, ANG also possesses anti- Human Immunodeficiency Virus-1 (HIV-1) properties. Previous findings show that ANG inhibits X4 tropic HIV-1 replication in peripheral blood mononuclear cells (PBMCs). Our studies show that ANG also inhibits R5 tropic virus, the most commonly transmitted HIV-1 strain. Inhibition was detected treating cells prior to or after infection by p24 ELISA, and is not mediated by CD4, CXCR4, or CCR5 as determined by flow cytometry assays. Furthermore, we demonstrated that ANG binds to tRNA-Lys, which serves as primer for HIV-1 reverse transcription. These results indicate that ANG inhibits HIV-1 replication by a post-entry mechanism, which might be exploited to develop new antiretroviral strategies.
    • Human T Helper 17 Cells Are Highly Permissive to Productive Human Immunodeficiency Virus Infection

      Christensen-Quick, Aaron Robert; Garzino-Demo, Alfredo (2015)
      Human Immunodeficiency Virus (HIV) infects and depletes CD4+ T cells, but subsets of CD4+ T cells vary in their susceptibility and permissiveness to infection. For example, HIV preferentially infects effector/memory T cells in the Gut Associated Lymphoid Tissue (GALT). IL-17-producing "T helper 17" (Th17) cells are enriched within the GALT, and are highly susceptible to HIV. The preferential depletion of Th17 cells during the acute phase of infection is associated with impairment of the integrity of the gut mucosal barrier, which drives chronic immune activation - a key determinant of disease progression. The preferential loss of Th17 cells has been attributed to high CD4, CCR5, and CXCR4 receptor expression, paired with low expression of HIV-inhibitory co-receptor ligands. Here we show that Th17 cells also exhibit heightened permissiveness to productive HIV infection. Primary human CD4+ T cells were sorted, activated in Th17- or Th0-polarizing conditions and infected, then analyzed by flow cytometry. Th17-polarizing cytokines increased HIV infection, and HIV infection was significantly higher among Th17 cells compared with IL-17- or IFNγ+ cells, even upon infecting with a replication-defective, envelope-pseudotyped HIV vector. Further, Th17-polarized cells produced more virus. Based on these observations, we hypothesized that the presence of positive effectors of HIV replication (such as a favorable transcriptional environment) in Th17 cells, and/or a relative lack of negative effectors (such as antiviral immune defenses) could contribute to their permissiveness to HIV. Microarray and immunoblot analyses performed on Th17- or Th0-polarized CD4+ T cells reveal that Th17-polarized cells have diminished expression of HIV-inhibitory members of the RNase A superfamily. Our findings demonstrate that human, peripheral blood Th17 cells are not only susceptible but also permissive to HIV infection. Our data link gene expression in Th17 cells to increased HIV production, suggesting that Th17 cells might be major sources of viral production during acute infection.
    • IDENTIFICATION OF AN INTRACELLULAR MECHANISM OF HIV-1 INHIBITION BY HUMAN BETA DEFENSIN 2

      Lafferty, Mark; Garzino-Demo, Alfredo (2011)
      Early during the course of HIV-1 infection there is a profound loss of CD4+ T cells which is particularly devastating within the gut associated lymphoid tissue (GALT). CD4+CCR6+ T cells are highly susceptible to infection compared to CCR6¯ cells and this subset is preferentially depleted from both GALT and the peripheral blood. CCR6+ cells are crucial for maintaining gut immune function and homeostasis. In animal models, the absence of CCR6 or either of its ligands, macrophage inflammatory protein-3α (MIP-3α) or human beta defensin 2 (hBD2), results in impaired gut immune responses and defects in lymphoid architecture. Depletion of CCR6+ T cells from the GALT may further contribute to immune dysfunction in the gut during HIV-1 infection. Decreased immune function and compromised barrier protection leaves the gut more susceptible to microbial pathogens and microbial translocation across the gut lumen which can trigger immune activation, a strong predictor of disease progression. Therefore, therapeutic strategies that target CCR6+ T cell subsets are needed. We have identified a novel CCR6-dependent mechanism of HIV-1 inhibition mediated by hBD2. The anti-HIV-1 attributes of hBD2 combined with broad antimicrobial activity against gram-negative bacteria and fungi make this endogenous peptide an attractive candidate for potential application as a microbicide. Our previous work demonstrated that treatment of HIV-1 virions with hBD2 reduces infectivity. Here, we report an additional mechanism of inhibition that is CCR6-dependent and occurs after virus entry at an early stage of infection either prior to or during reverse transcription. This post-entry inhibition requires induction of the host restriction factor, apolipoprotein B mRNA editing enzyme-catalytic polypeptide-like 3G (APOBEC3G). In our proposed model, hBD2 inhibits HIV-1 by two distinct mechanisms: inactivation of virions and post-entry mediated by CCR6. Identification of this unique CCR6-mediated post-entry inhibition contributes to our understanding of pathways that underlie intrinsic immunity to HIV-1 and may ultimately guide development of effective therapeutics to selectively target and protect CCR6+ cells.