Human MAIT cells respond to and suppress HIV-1

Human MAIT cells sit at the interface between innate and adaptive immunity, are polyfunctional and are capable of killing pathogen infected cells via recognition of the Class IB molecule MR1. MAIT cells have recently been shown to possess an antiviral protective role in vivo and we therefore sought to explore this in relation to HIV-1 infection. There was marked activation of MAIT cells in vivo in HIV-1-infected individuals, which decreased following ART. Stimulation of THP1 monocytes with R5 tropic HIVBAL potently activated MAIT cells in vitro. This activation was dependent on IL-12 and IL-18 but was independent of the TCR. Upon activation, MAIT cells were able to upregulate granzyme B, IFNγ and HIV-1 restriction factors CCL3, 4, and 5. Restriction factors produced by MAIT cells inhibited HIV-1 infection of primary PBMCs and immortalized target cells in vitro. These data reveal MAIT cells to be an additional T cell population responding to HIV-1, with a potentially important role in controlling viral replication at mucosal sites

Deficiency of factor-inhibiting HIF creates a tumor-promoting immune microenvironment

Hypoxia signaling influences tumor development through both cell-intrinsic and -extrinsic pathways. Inhibiting hypoxia-inducible factor (HIF) function has recently been approved as a cancer treatment strategy. Hence, it is important to understand how regulators of HIF may affect tumor growth under physiological conditions. Here we report that in aging mice factor-inhibiting HIF (FIH), one of the most studied negative regulators of HIF, is a haploinsufficient suppressor of spontaneous B cell lymphomas, particular pulmonary B cell lymphomas. FIH deficiency alters immune composition in aged mice and creates a tumor-supportive immune environment demonstrated in syngeneic mouse tumor models. Mechanistically, FIH-defective myeloid cells acquire tumor-supportive properties in response to signals secreted by cancer cells or produced in the tumor microenvironment with enhanced arginase expression and cytokine-directed migration. Together, these data demonstrate that under physiological conditions, FIH plays a key role in maintaining immune homeostasis and can suppress tumorigenesis through a cell-extrinsic pathway

CD32-Expressing CD4 T Cells Are Phenotypically Diverse and Can Contain Proviral HIV DNA.

Efforts to both characterize and eradicate the HIV reservoir have been limited by the rarity of latently infected cells and the absence of a specific denoting biomarker. CD32a (FcγRIIa) has been proposed to be a marker for an enriched CD4 T cell HIV reservoir, but this finding remains controversial. Here, we explore the expression of CD32 on CD3+CD4+ cells in participants from two primary HIV infection studies and identify at least three distinct phenotypes (CD32low, CD32+CD14+, and CD32high). Of note, CD4 negative enrichment kits remove the majority of CD4+CD32+ T cells, potentially skewing subsequent analyses if used. CD32high CD4 T cells had higher levels of HLA-DR and HIV co-receptor expression than other subsets, compatible with their being more susceptible to infection. Surprisingly, they also expressed high levels of CD20, TCRαβ, IgD, and IgM (but not IgG), markers for both T cells and naïve B cells. Compared with other populations, CD32low cells had a more differentiated memory phenotype and high levels of immune checkpoint receptors, programmed death receptor-1 (PD-1), Tim-3, and TIGIT. Within all three CD3+CD4+CD32+ phenotypes, cells could be identified in infected participants, which contained HIV DNA. CD32 expression on CD4 T cells did not correlate with HIV DNA or cell-associated HIV RNA (both surrogate measures of overall reservoir size) or predict time to rebound viremia following treatment interruption, suggesting that it is not a dominant biomarker for HIV persistence. Our data suggest that while CD32+ T cells can be infected with HIV, CD32 is not a specific marker of the reservoir although it might identify a population of HIV enriched cells in certain situations

CD32-Expressing CD4 T Cells Are Phenotypically Diverse and Can Contain Proviral HIV DNA.

Efforts to both characterize and eradicate the HIV reservoir have been limited by the rarity of latently infected cells and the absence of a specific denoting biomarker. CD32a (FcγRIIa) has been proposed to be a marker for an enriched CD4 T cell HIV reservoir, but this finding remains controversial. Here, we explore the expression of CD32 on CD3+CD4+ cells in participants from two primary HIV infection studies and identify at least three distinct phenotypes (CD32low, CD32+CD14+, and CD32high). Of note, CD4 negative enrichment kits remove the majority of CD4+CD32+ T cells, potentially skewing subsequent analyses if used. CD32high CD4 T cells had higher levels of HLA-DR and HIV co-receptor expression than other subsets, compatible with their being more susceptible to infection. Surprisingly, they also expressed high levels of CD20, TCRαβ, IgD, and IgM (but not IgG), markers for both T cells and naïve B cells. Compared with other populations, CD32low cells had a more differentiated memory phenotype and high levels of immune checkpoint receptors, programmed death receptor-1 (PD-1), Tim-3, and TIGIT. Within all three CD3+CD4+CD32+ phenotypes, cells could be identified in infected participants, which contained HIV DNA. CD32 expression on CD4 T cells did not correlate with HIV DNA or cell-associated HIV RNA (both surrogate measures of overall reservoir size) or predict time to rebound viremia following treatment interruption, suggesting that it is not a dominant biomarker for HIV persistence. Our data suggest that while CD32+ T cells can be infected with HIV, CD32 is not a specific marker of the reservoir although it might identify a population of HIV enriched cells in certain situations

Novel approaches to the characterization of antigen-specific CD4+ T cells in HIV-1 infection

Immune reconstitution is typical in chronic HIV-1 infected individuals who aretreated with combination anti-retroviral therapy (cART). The characteristics ofthis were monitored in 20 chronically infected subjects recruited through thePrIRIS study. Changes in CD4+ T cell function were characterized in the context ofincreases in CD4+ T-cell counts and decreases in plasma viral load over the firstyear of therapy using the CD25/OX40 assay and a range of phenotypic assays.The CD25/OX40 assay was used to identify antigen-specific CD4+ T-cells in vitro.In healthy individuals the majority of CMV-specific responses were from theeffector memory (Tem) subset, with TT-specific responses arising from the centralmemory (Tcm) subset. In chronic HIV+ subjects post-therapy, the ratio of theresponding memory subsets was inverted, with a greater gag response comingfrom the Tcm subset at week 48 compared to week 4. This result was concordantwith reduced antigen load. As activation decreased, the percentage of respondingTem cells decreased, but long-term Tcm responses were maintained.A qualitative multiplex single-cell RT-PCR assay was developed to be useddownstream of the CD25/OX40 assay. This assay has high specificity and a verylow cut-off of detection (down to 10 femtograms). Lineage specific transcriptionfactor profiling, allowed delineation of Th1 (Tbet), Th2 (Gata3), Th17 (Rorc), Tregs(Foxp3) and Tfh (BCL6) cells within an antigen specific population. Resultsdemonstrated >80% of activated Ag-specific single cells expressed only 1transcription factor. CMV-specific CD4+ T-cells displayed a dominant Th1-likeresponse, while TT-specific cells displayed a Th2-like response, additionally asmall percentage of polyfunctional CMV and TT-specific cells expressed ≥2transcription factors.PKC-θ a novel protein kinase plays an important role in T cell development,proliferation, differentiation and chromatin remodelling. In Ag-specific CD4+ Tcells,PKC-θ was bound in intronic regions of genes, where it was highly associatedwith permissive histone marks and enhancer-like chromatin state. NF-κB (p65)was identified as having common binding sites to PKC-θ. p65 motifs were foundmostly within the promoter, 5UTR and exons of inducible genes. This resulthighlights the possible involvement of NF-κB and PKC-θ as potential bindingpartners.In conclusion, antigen-specific CD4+ T-cells are very important for controllingsecondary infections and maintenance of immunological control. Thecharacterization of virus-specific CD4+ T-cells at the cellular and molecular levelare likely to reveal mechanisms for the manipulation of immunological memorydevelopment and its maintenance, allowing improved design of immunotherapiesand vaccines

Single‐cell profiling of lineage determining transcription factors in antigen‐specific CD4 +

Recent studies of protein and gene expression at the single-cell level have revealed that the memory T-cell compartment is more heterogeneous than previously acknowledged. Identifying different T helper subsets involved in memory responses at the single-cell level is thus necessary to understand the level of heterogeneity within this population. Antigen-specific CD4+ T cells were measured using the CD25/OX40 assay together with a qualitative multiplex single-cell RT-PCR assay. Transcription profiles and subset proportions within the antigen-specific CD4+ T-cell population were dissected. Cytomegalovirus (CMV)-specific CD4+ T-cell responses skewed toward a Th1 response, whereas Tetanus toxoid responses skewed toward a Th2 type response. Fluctuations in CD4+ T-cell subsets were observed within the HIV-Gag-specific response during ongoing antiretroviral therapy. Strong effector responses (Th1) were observed in early treatment, however with ongoing therapy this effector response significantly decreased in combination with an increase in Tregs and circulating Tfh-like BCL-6+ memory cells. The apparent increase in Tcm in peripheral blood after a several weeks of antiretroviral therapy may be due to Tfh-like cell egress from germinal centers into the periphery