Differential localization and limited cytotoxic potential of duodenal CD8+ T cells.

The duodenum is a major site of HIV persistence during suppressive antiretroviral therapy despite harboring abundant tissue-resident memory (Trm) CD8+ T cells. The role of duodenal Trm CD8+ T cells in viral control is still not well defined. We examined the spatial localization, phenotype, and function of CD8+ T cells in the human duodenal tissue from people living with HIV (PLHIV) and healthy controls. We found that Trm (CD69+CD103hi) cells were the predominant CD8+ T cell population in the duodenum. Immunofluorescence imaging of the duodenal tissue revealed that CD103+CD8+ T cells were localized in the intraepithelial region, while CD103-CD8+ T cells and CD4+ T cells were mostly localized in the lamina propria (LP). Furthermore, HIV-specific CD8+ T cells were enriched in the CD69+CD103-/lo population. However, the duodenal HIV-specific CD8+ Trm cells rarely expressed canonical molecules for potent cytolytic function (perforin and granzyme B) but were more polyfunctional than those from peripheral blood. Taken together, our results show that duodenal CD8+ Trm cells possess limited perforin-mediated cytolytic potential and are spatially separated from HIV-susceptible LP CD4+ T cells. This could contribute to HIV persistence in the duodenum and provides critical information for the design of cure therapies.

Airway CD8+CD161++TCRvα7.2+ T Cell Depletion During Untreated HIV Infection Targets CD103 Expressing Cells.

HIV-infected adults are at an increased risk to lower respiratory tract infections (LRTIs). CD8+CD161++TCRvα7.2+ T cells are an innate-like T cell subset that are thought to play an important role in early defense against pathogens in the respiratory tract. HIV infection leads to irreversible depletion of these cells in peripheral blood, however, its impact on this subset in the human airway is still unclear. Here, we show presence of CD103 expressing CD8+CD161++TCRvα7.2+ T cells in the airway that exhibited a distinct cytokine functional profile compared to their CD103- airway counterparts and those from peripheral blood. These CD103 expressing airway CD8+CD161++TCRvα7.2+ T cells were selectively depleted in untreated HIV-infected adults compared to healthy controls. Their frequency was positively correlated with frequency of airway CD4+ T cells. Furthermore, the frequency of airway CD8+CD161++TCRvα7.2+ T cells was also inversely correlated with HIV plasma viral load, while suppressive antiretroviral therapy (ART) resulted in restoration of airway CD8+CD161++TCRvα7.2+ T cells. Our findings show that CD103 expressing airway CD8+CD161++TCRvα7.2+ T cells are functionally distinct and are preferentially depleted during untreated asymptomatic HIV infection. Depletion of CD103 expressing airway CD8+CD161++TCRvα7.2+ T cells, at a major portal of pathogen entry, could partly contribute to the increased propensity for opportunistic LRTIs observed in untreated HIV-infected adults.

Inhibition of the lncRNA SAF drives activation of apoptotic effector caspases in HIV-1-infected human macrophages.

Long noncoding RNAs (lncRNAs) impart significant regulatory functions in a diverse array of biological pathways and manipulation of these RNAs provides an important avenue to modulate such pathways, particularly in disease. Our knowledge about lncRNAs' role in determination of cellular fate during HIV-1 infection remains sparse. Here, we have identified the impact of the lncRNA SAF in regulating apoptotic effector caspases in macrophages, a long-lived cellular reservoir of HIV-1, that are largely immune to virus-induced cell death. Expression of SAF is significantly up-regulated in HIV-1-infected human monocyte-derived macrophages (MDM) compared with bystander and virus-nonexposed cells. A similar enhancement in SAF RNA expression is also detected in the HIV-1-infected airway macrophages obtained by bronchoalveolar lavage of HIV-1-infected individuals. Down-regulation of SAF with siRNA treatment increases caspase-3/7 activity levels in virus-infected MDMs. This induction of apoptotic caspases occurs exclusively in HIV-1-infected macrophages and not in bystander cells, leading to a significant reduction in HIV-1 replication and overall viral burden in the macrophage culture. This study identifies targeting of the lncRNA SAF as a potential means to specifically induce cell death in HIV-1-infected macrophages.

Functional Analysis of Phagocyte Activity in Whole Blood from HIV/Tuberculosis-Infected Individuals Using a Novel Flow Cytometry-Based Assay.

The accurate assessment of immune competence through ex vivo analysis is paramount to our understanding of those immune mechanisms that lead to protection or susceptibility against a broad range of human pathogens. We have developed a flow cytometry-based, whole blood phagocyte functional assay that utilizes the inflammatory inducer zymosan, coupled to OxyBURST-SE, a fluorescent reporter of phagosomal oxidase activity. The assay measures both phagocytic uptake and the superoxide burst in the phagocyte populations in whole blood. We utilized this assay to demonstrate impaired superoxide burst activity in the phagocytes of hospitalized HIV-positive patients with laboratory-confirmed tuberculosis. These data validate the use of the assay to assess the immune competence of patients in a clinical setting. The method is highly reproducible with minimal intraindividual variation and opens opportunities for the rapid assessment of cellular immune competence in peripheral blood in a disease setting.

B cell, CD8 + T cell and gamma delta T cell infiltration alters alveolar immune cell homeostasis in HIV-infected Malawian adults.

Background: HIV infection is associated with increased risk to lower respiratory tract infections (LRTI). However, the impact of HIV infection on immune cell populations in the lung is not well defined. We sought to comprehensively characterise the impact of HIV infection on immune cell populations in the lung. Methods: Twenty HIV-uninfected controls and 17 HIV-1 infected ART-naïve adults were recruited from Queen Elizabeth Central Hospital, Malawi. Immunophenotyping of lymphocyte and myeloid cell populations was done on bronchoalveolar lavage fluid and peripheral blood cells. Results: We found that the numbers of CD8 + T cells, B cells and gamma delta T cells were higher in BAL fluid of HIV-infected adults compared to HIV-uninfected controls (all p<0.05). In contrast, there was no difference in the numbers of alveolar CD4 + T cells in HIV-infected adults compared to HIV-uninfected controls (p=0.7065). Intermediate monocytes were the predominant monocyte subset in BAL fluid (HIV-, 63%; HIV+ 81%), while the numbers of classical monocytes was lower in HIV-infected individuals compared to HIV-uninfected adults (1 × 10 5 vs. 2.8 × 10 5 cells/100ml of BAL fluid, p=0.0001). The proportions of alveolar macrophages and myeloid dendritic cells was lower in HIV-infected adults compared to HIV-uninfected controls (all p<0.05). Conclusions: Chronic HIV infection is associated with broad alteration of immune cell populations in the lung, but does not lead to massive depletion of alveolar CD4 + T cells. Disruption of alveolar immune cell homeostasis likely explains in part the susceptibility for LRTIs in HIV-infected adults.