Dynamic MAIT cell response with progressively enhanced innateness during acute HIV-1 infection.

Mucosa-associated invariant T (MAIT) cell loss in chronic HIV-1 infection is a significant insult to antimicrobial immune defenses. Here we investigate the response of MAIT cells during acute HIV-1 infection utilizing the RV217 cohort with paired longitudinal pre- and post-infection samples. MAIT cells are activated and expand in blood and mucosa coincident with peak HIV-1 viremia, in a manner associated with emerging microbial translocation. This is followed by a phase with elevated function as viral replication is controlled to a set-point level, and later by their functional decline at the onset of chronic infection. Interestingly, enhanced innate-like pathways and characteristics develop progressively in MAIT cells during infection, in parallel with TCR repertoire alterations. These findings delineate the dynamic MAIT cell response to acute HIV-1 infection, and show how the MAIT compartment initially responds and expands with enhanced function, followed by progressive reprogramming away from TCR-dependent antibacterial responses towards innate-like functionality

Dynamic MAIT cell response with progressively enhanced innateness during acute HIV-1 infection.

Mucosa-associated invariant T (MAIT) cell loss in chronic HIV-1 infection is a significant insult to antimicrobial immune defenses. Here we investigate the response of MAIT cells during acute HIV-1 infection utilizing the RV217 cohort with paired longitudinal pre- and post-infection samples. MAIT cells are activated and expand in blood and mucosa coincident with peak HIV-1 viremia, in a manner associated with emerging microbial translocation. This is followed by a phase with elevated function as viral replication is controlled to a set-point level, and later by their functional decline at the onset of chronic infection. Interestingly, enhanced innate-like pathways and characteristics develop progressively in MAIT cells during infection, in parallel with TCR repertoire alterations. These findings delineate the dynamic MAIT cell response to acute HIV-1 infection, and show how the MAIT compartment initially responds and expands with enhanced function, followed by progressive reprogramming away from TCR-dependent antibacterial responses towards innate-like functionality

Longitudinal Analysis of Peripheral and Colonic CD161+ CD4+ T Cell Dysfunction in Acute HIV-1 Infection and Effects of Early Treatment Initiation

CD161 expression on CD4+ T cells is associated with a Th17 functional phenotype, as well as with an innate capacity to respond to interleukin (IL)-12 and IL-18 without T cell receptor (TCR) stimulation. Chronic HIV-1 infection is associated with loss of the CD161+ CD4 T cell population, and non-human primate studies suggest that their depletion is associated with disease progression. However, the dynamics of the CD161+ CD4+ T cell population during acute HIV-1 infection remains unknown. In this study, we characterize peripheral blood CD161+ CD4+ T cells in detail, and examine how they are affected during the earliest stages of HIV-1 infection. Unbiased surface proteome screening and principal component analysis indicated that CD161+ CD4+ T cells are relatively phenotypically homogeneous between donors, and are intermediates between conventional CD4 T cells and innate-like T cells. In acute untreated HIV-1 infection, the circulating CD161+ CD4+ T cell population decreased in frequency, as did absolute cell counts starting from peak viral load, with elevated levels of activation and exhaustion markers expressed throughout acute HIV-1 infection. The capacity of these cells to respond to stimulation with IL-12 and IL-18 was also reduced. Early initiation of anti-retroviral treatment (ART) during acute HIV-1 infection restored the functionality of peripheral blood CD161+ CD4+ T cells, but not their frequency. In contrast, early ART initiation prevented the decline of colonic CD161+ CD4+ T cells that otherwise started during acute infection. Furthermore, loss of peripheral and colonic CD161+ CD4+ T cells in untreated infection was associated with levels of viral load. These results suggest that acute HIV-1 infection has profound effects on the CD161+ CD4+ T cell population that could not be completely prevented by the initiation of ART

Initiation of ART during Early Acute HIV Infection Preserves Mucosal Th17 Function and Reverses HIV-Related Immune Activation

<div><p>Mucosal Th17 cells play an important role in maintaining gut epithelium integrity and thus prevent microbial translocation. Chronic HIV infection is characterized by mucosal Th17 cell depletion, microbial translocation and subsequent immune-activation, which remain elevated despite antiretroviral therapy (ART) correlating with increased mortality. However, when Th17 depletion occurs following HIV infection is unknown. We analyzed mucosal Th17 cells in 42 acute HIV infection (AHI) subjects (Fiebig (F) stage I-V) with a median duration of infection of 16 days and the short-term impact of early initiation of ART. Th17 cells were defined as IL-17+ CD4+ T cells and their function was assessed by the co-expression of IL-22, IL-2 and IFNγ. While intact during FI/II, depletion of mucosal Th17 cell numbers and function was observed during FIII correlating with local and systemic markers of immune-activation. ART initiated at FI/II prevented loss of Th17 cell numbers and function, while initiation at FIII restored Th17 cell numbers but not their polyfunctionality. Furthermore, early initiation of ART in FI/II fully reversed the initially observed mucosal and systemic immune-activation. In contrast, patients treated later during AHI maintained elevated mucosal and systemic CD8+ T-cell activation post initiation of ART. These data support a loss of Th17 cells at early stages of acute HIV infection, and highlight that studies of ART initiation during early AHI should be further explored to assess the underlying mechanism of mucosal Th17 function preservation.</p></div

Clinical, immunological and virological baseline characteristics and demographics of study participants.

A<p>range;</p>B<p>MHAbce: Multi-region hybridization assay distinguishing between subtypes B, C and CRF01_AE. One subject was CRF01_AE/B, 8 were non typable and results for 3 subjects were not typed by the time the manuscript was written;</p>C<p>Western blot positive with p31 band; MSM: Men who have sex with men; Fiebig I - positive HIV RNA, negative p24 antigen, negative 3rd generation EIA; Fiebig II – positive HIV RNA, positive p24 antigen, negative 3rd generation EIA; Fiebig III - positive HIV RNA, positive p24 antigen, positive 3rd generation EIA, negative western blot; Fiebig IV - positive HIV RNA, positive or negative p24 antigen, positive 3rd generation EIA, indeterminate western blot; Fiebig V - positive HIV RNA, positive p24 antigen, positive 3rd generation EIA, positive western blot except p31; NA: Not Applicable; ND: Not Determined</p><p>Clinical, immunological and virological baseline characteristics and demographics of study participants.</p

Frequency of IL-17 and/or IL-22 expressing mucosal CD4+T cells decreases by progression of Fiebig stage.

<p>To quantify the expression of Il-17 and IL-22 in CD4+T cells, mucosal and peripheral mononuclear cells were stimulated for 5 hours with 40 ng/mL PMA and 1 µM Ionomycin. Gating strategy of sigmoid colon Th17 and Th22 CD4+T cells is shown for a FI subject (<b>a</b>) and representative flow cytometry plots including unstimulated controls (unstim) gated on CD4+T cells showing expression of IL-17 and/or IL-22 in FI (<b>b</b>), FIII (<b>c</b>) and FV (<b>d</b>) in the sigmoid colon. A decrease in the frequency of IL-17 (<b>e</b>), IL-22 (<b>f</b>), IL-17/IL-22 (<b>g</b>)-producing cells was seen as well as in the subpopulation of triple-cytokine producing (IL-2, IL-22, IFNγ) Th17 cells (<b>h</b>) from FI (black circle)/FII (red circle) to FIII and FIV (red square)/FV (black square). Frequency of single and double cytokine producing cells is calculated from percentage CD4+T cells, while triple-cytokine producing cells are calculated from percentage of CD4+IL17+T cells. All comparisons were made to FI/II: *p≤0.05, **p≤0.01 and ***p≤0.001.</p

Impact of early ART initiation on CD4+ and CD8+T cells as well as Th17 cells.

<p>Subjects that initiated ART during FI (black circle)/FII (red circle) for 6 months were able to maintain mucosal CD4+T cells (<b>a</b>), CD4+CCR5+ (<b>b</b>), Th17 cells (<b>c</b>), triple cytokine-producing Th17 cells (<b>d</b>), Th22 cells (<b>e</b>), and IL-17 and/or IL-22 (<b>f</b>) producing CD4+T cells with no differences when compared to HIV-. In addition their CD8 activation in the mucosa (<b>g</b>) and periphery (<b>h</b>) normalized after 6 months of ART. Frequency of single and double cytokine producing cells was calculated from percentage CD4+T cells, while triple-cytokine producing cells were calculated from percentage of CD4+IL17+T cells. *p≤0.05, **p≤0.01 and ***p≤0.001; DR: HLA-DR; blue dotted line: median of HIV- individuals; purple dotted line: median of CHI individuals.</p

Proportion and absolute number of CD4+, CD4+CCR5+ and CD8+ T cells in sigmoid colon and peripheral blood at baseline in HIV-, FI/II, FIII, FIV/V and CHI subjects.

<p>All data are median (interquartile rang); All comparisons were made to FI/II; *p≤0.05, **p≤0.01 and ***p≤0.001; CHI: Chronically HIV-infected patients; ND: Not Determined; abs numbers in the sigmoid colon are shown as 10⁶ cells per gram tissue and in the peripheral blood as cells/mm^{3; &}Percentage of CD4+ and CD8+T cells based on population of CD3+T cells.</p><p>Proportion and absolute number of CD4+, CD4+CCR5+ and CD8+ T cells in sigmoid colon and peripheral blood at baseline in HIV-, FI/II, FIII, FIV/V and CHI subjects.</p

Percentage area of lamina propria CD4+ staining (% Area LP) decreases with progression of Fiebig stage.

<p>(<b>a</b>) The percent area of the lamina propria that stained for CD4+T cells (representative images shown in e) decreases by Fiebig stage in the sigmoid colon when compared to FI/II (*p≤0.05, **p≤0.01 and ***p≤0.001). The percent area of the lamina propria that stained for CD4+T cells correlated inversely with the colonic (<b>b</b>) and plasma (<b>c</b>) HIV RNA in FI/II, FIII and FIV/V. HIV viral replication during different Fiebig stages is shown by in <i>situ hybridization</i> displaying HIV-1 vRNA+ cells within the sigmoid mucosa, indicated by blue/black stained cells in nuclear fast red counterstained tissue sections (black arrows highlighting examples of HIV vRNA+ cells) of patients in FI, FII and FIII (<b>d</b>). CD4+T cell depletion is shown by immunohistochemical staining of CD4+T cells (brown) and macrophages (red) in sigmoid mucosa of patients in FI, FII and FIII (<b>e</b>). FI (black circle)/FII (red circle) and FIV (red square)/FV (black square).</p