Small Molecules and Big Killers: The Challenge of Eliminating the Latent HIV Reservoir

HIV-Specific Immunity Section, Laboratory of Immunoregulation, NIAID/NIH, Bethesda, MD 20892, USA.
Immunity (Impact Factor: 21.56). 03/2012; 36(3):320-1. DOI: 10.1016/j.immuni.2012.03.006
Source: PubMed


In this issue of Immunity, Shan et al. (2012) explore the elimination of cells latently infected with HIV and the potential implications for strategies to eradicate the virus from infected patients.

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    • "The establishment of stable latent reservoirs [6] dictates lifelong ART treatment associated with financial cost and potential toxicity, thus, therapies leading to HIV eradication are urgently warranted. Recent studies have focused on using small molecules that, unlike antibodies, reactivate the latent reservoirs without inducing unrestrained T cell activation [7]. However, data from a seminal study by Shan et al [8] indicate that reactivating the viral reservoir using the FDA-approved histone deacetylase inhibitor (HDACi), suberoylanilide hydroxamic acid (SAHA) was not associated with the death of infected CD4+ T cells as was previously hypothesized. "
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    ABSTRACT: During HIV infection, IL-10/IL-10 receptor and programmed death-1 (PD-1)/programmed death-1-ligand (PD-L1) interactions have been implicated in the impairment of cytotoxic T lymphocyte (CTL) activity. Despite antiretroviral therapy (ART), attenuated anti-HIV CTL functions present a major hurdle towards curative measures requiring viral eradication. Therefore, deeper understanding of the mechanisms underlying impaired CTL is crucial before HIV viral eradication is viable. The generation of robust CTL activity necessitates interactions between antigen-presenting cells (APC), CD4+ and CD8+ T cells. We have shown that in vitro, IL-10hiPD-L1hi regulatory B cells (Bregs) directly attenuate HIV-specific CD8+-mediated CTL activity. Bregs also modulate APC and CD4+ T cell function; herein we characterize the Breg compartment in uninfected (HIVNEG), HIV-infected "elite controllers" (HIVEC), ART-treated (HIVART), and viremic (HIVvir), subjects, and in vitro, assess the impact of Bregs on anti-HIV CTL generation and activity after reactivation of HIV latent reservoirs using suberoylanilide hydroxamic acid (SAHA). We find that Bregs from HIVEC and HIVART subjects exhibit comparable IL-10 expression levels significantly higher than HIVNEG subjects, but significantly lower than HIVVIR subjects. Bregs from HIVEC and HIVART subjects exhibit comparable PD-L1 expression, significantly higher than in HIVVIR and HIVNEG subjects. SAHA-treated Breg-depleted PBMC from HIVEC and HIVART subjects, displayed enhanced CD4+ T-cell proliferation, significant upregulation of antigen-presentation molecules, increased frequency of CD107a+ and HIV-specific CD8+ T cells, associated with efficient elimination of infected CD4+ T cells, and reduction in integrated viral DNA. Finally, IL-10-R and PD-1 antibody blockade partially reversed Breg-mediated inhibition of CD4+ T-cell proliferation. Our data suggest that, possibly, via an IL-10 and PD-L1 synergistic mechanism; Bregs likely inhibit APC function and CD4+ T-cell proliferation, leading to anti-HIV CTL attenuation, hindering viral eradication.
    PLoS ONE 04/2014; 9(4):e92934. DOI:10.1371/journal.pone.0092934 · 3.23 Impact Factor
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    ABSTRACT: Latent HIV reservoirs are the greatest challenge facing an HIV cure. Here, we review recent evidence supporting an important role for the host immune response, in particular HLA class I-restricted CD8+ T lymphocytes, in modulating HIV reservoirs during natural infection. These observations indicate that factors governing immune-mediated control of HIV may also contribute to the clearance of viral reservoirs. As such, critical gaps in our understanding of HIV immunology hinder efforts to develop both an effective HIV vaccine as well as novel therapies that may lead to a cure. The importance of elucidating correlates of protective cellular immunity should be recognized during research to develop and test potential HIV elimination strategies.
    08/2012; 2(5):599-605. DOI:10.1016/j.coviro.2012.08.003
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