Low Levels of Peripheral CD161++CD8+ Mucosal Associated Invariant T (MAIT) Cells Are Found in HIV and HIV/TB Co-Infection

Background: High expression of CD161 on CD8+ T cells is associated with a population of cells thought to play a role in mucosal immunity. We wished to investigate this subset in an HIV and Mycobacterium tuberculosis (MTB) endemic African setting. Methods: A flow cytometric approach was used to assess the frequency and phenotype of CD161++CD8+ T cells. 80 individuals were recruited for cross-sectional analysis: controls (n = 18), latent MTB infection (LTBI) only (n = 16), pulmonary tuberculosis (TB) only (n = 8), HIV only (n = 13), HIV and LTBI co-infection (n = 15) and HIV and TB co-infection (n = 10). The impact of acute HIV infection was assessed in 5 individuals recruited within 3 weeks of infection. The frequency of CD161++CD8+ T cells was assessed prior to and during antiretroviral therapy (ART) in 14 HIV-positive patients. Results: CD161++CD8+ T cells expressed high levels of the HIV co-receptor CCR5, the tissue-homing marker CCR6, and the Mucosal-Associated Invariant T (MAIT) cell TCR Vα7.2. Acute and chronic HIV were associated with lower frequencies of CD161++CD8+ T cells, which did not correlate with CD4 count or HIV viral load. ART was not associated with an increase in CD161++CD8+ T cell frequency. There was a trend towards lower levels of CD161++CD8+ T cells in HIV-negative individuals with active and latent TB. In those co-infected with HIV and TB, CD161++CD8+ T cells were found at low levels similar to those seen in HIV mono-infection. Conclusions: The frequencies and phenotype of CD161++CD8+ T cells in this South African cohort are comparable to those published in European and US cohorts. Low-levels of this population were associated with acute and chronic HIV infection. Lower levels of the tissue-trophic CD161++ CD8+ T cell population may contribute to weakened mucosal immune defense, making HIV-infected subjects more susceptible to pulmonary and gastrointestinal infections and detrimentally impacting on host defense against TB

TRAV1-2⁺ CD8⁺ T-cells including oligoconal expansions of MAIT cells are enriched in the airways in human tuberculosis

Mucosal-associated invariant T (MAIT) cells typically express a TRAV1-2+ semi-invariant TCRα that enables recognition of bacterial, mycobacterial, and fungal riboflavin metabolites presented by MR1. MAIT cells are associated with immune control of bacterial and mycobacterial infections in murine models. Here, we report that a population of pro-inflammatory TRAV1-2+ CD8+ T cells are present in the airways and lungs of healthy individuals and are enriched in bronchoalveolar fluid of patients with active pulmonary tuberculosis (TB). High-throughput T cell receptor analysis reveals oligoclonal expansions of canonical and donor-unique TRAV1-2+ MAIT-consistent TCRα sequences within this population. Some of these cells demonstrate MR1-restricted mycobacterial reactivity and phenotypes suggestive of MAIT cell identity. These findings demonstrate enrichment of TRAV1-2+ CD8+ T cells with MAIT or MAIT-like features in the airways during active TB and suggest a role for these cells in the human pulmonary immune response to Mycobacterium tuberculosis

Immunometabolism at the crossroads of obesity and cancer-a Keystone Symposia report.

peer reviewedImmunometabolism considers the relationship between metabolism and immunity. Typically, researchers focus on either the metabolic pathways within immune cells that affect their function or the impact of immune cells on systemic metabolism. A more holistic approach that considers both these viewpoints is needed. On September 5-8, 2022, experts in the field of immunometabolism met for the Keystone symposium "Immunometabolism at the Crossroads of Obesity and Cancer" to present recent research across the field of immunometabolism, with the setting of obesity and cancer as an ideal example of the complex interplay between metabolism, immunity, and cancer. Speakers highlighted new insights on the metabolic links between tumor cells and immune cells, with a focus on leveraging unique metabolic vulnerabilities of different cell types in the tumor microenvironment as therapeutic targets and demonstrated the effects of diet, the microbiome, and obesity on immune system function and cancer pathogenesis and therapy. Finally, speakers presented new technologies to interrogate the immune system and uncover novel metabolic pathways important for immunity

Latent and Active Tuberculosis Infection Increase Immune Activation in Individuals Co-Infected with HIV☆☆☆★

In recent years, chronic immune activation and systemic inflammation have emerged as hallmarks of HIV disease progression and mortality. Several studies indicate that soluble inflammatory biomarkers (sCD14, IL-6, IL-8, CRP and hyaluronic acid), as well as surface markers of T-cell activation (CD38, HLA-DR) independently predict progression to AIDS and mortality in HIV-infected individuals. While co-infections have been shown to contribute to immune activation, the impact of latent tuberculosis infection (LTBI), which is widely endemic in the areas most affected by the global AIDS epidemic, has not been evaluated. We hypothesized that both active and latent states of Mycobacterium tuberculosis co-infection contribute to elevated immune activation as measured by these markers. In HIV-infected individuals with active, but not latent TB, we found elevated levels of soluble markers associated with monocyte activation. Interestingly, T-cell activation was elevated individuals with both latent and active TB. These results suggest that in the highly TB- and HIV-endemic settings of southern Africa, latent TB-associated T-cell activation may contribute to HIV disease progression and exacerbate the HIV epidemic. In addition, our findings indicate that aggressive campaigns to treat LTBI in HIV-infected individuals in high-burden countries will not only impact TB rates, but may also slow HIV progression. Significance Latent tuberculosis, which affects an estimated 1/3 of the world's population, has long been thought to be a relatively benign, quiescent state of M. tuberculosis infection. While HIV co-infection is known to exacerbate M. tuberculosis infection and increase the risk of developing active TB, little is known about the potential effect of latent TB infection on HIV disease. This study shows that HIV-infected individuals with both active and latent TB have elevated levels of inflammation and immune activation, biomarkers of HIV disease progression and elevated risk of mortality. These results suggest that, in the context of HIV, latent TB infection may be associated with increased risk of progression to AIDS and mortality

Mycobacterial Metabolic Syndrome: LprG and Rv1410 Regulate Triacylglyceride Levels, Growth Rate and Virulence in Mycobacterium tuberculosis

Mycobacterium tuberculosis (Mtb) mutants lacking rv1411c, which encodes the lipoprotein LprG, and rv1410c, which encodes a putative efflux pump, are dramatically attenuated for growth in mice. Here we show that loss of LprG-Rv1410 in Mtb leads to intracellular triacylglyceride (TAG) accumulation, and overexpression of the locus increases the levels of TAG in the culture medium, demonstrating a role of this locus in TAG transport. LprG binds TAG within a large hydrophobic cleft and is sufficient to transfer TAG from donor to acceptor membranes. Further, LprG-Rv1410 is critical for broadly regulating bacterial growth and metabolism in vitro during carbon restriction and in vivo during infection of mice. The growth defect in mice is due to disrupted bacterial metabolism and occurs independently of key immune regulators. The in vivo essentiality of this locus suggests that this export system and other regulators of metabolism should be considered as targets for novel therapeutics

Acute HIV infection is associated with a lower frequency of CD161++ CD8+ T cells.

<p>Figure 3A: Graph displays CD161++ CD8+ T cell frequency in HIV negative and TB negative subjects (HNTN, n = 14), individuals with chronic HIV infection (HIV positive TB negative HPTN, n = 13), and individuals in the acute phase of HIV infection (n = 5, sample taken within 2–3 weeks of presumed infection date). CD161++CD8+ T cells are significantly lower in HPTN individuals and those with acute HIV. Figure 3B: Graph displays CD161+CD8+ T cell frequency in the same three groups of subjects; CD161+ CD8+ T cells do not show any differences between these three groups. Figure 3C: A representative FACS plot displaying the CD161++ CD8+ T cell population over time in an individual acutely infected with HIV and assessed at 5 timepoints. Both graphs show median and interquartile range; p-values are reported for two-sided Mann-Whitney tests with threshold for significance p = 0.025 after Bonferroni correction for 2 comparisons.</p

Impact of Antiretroviral treatment (ART) on CD161++ CD8+ T cell frequency.

<p>Figure 4A: Graph displaying CD161++CD8+ T cell frequency (median and interquartile range) from 14 HIV negative TB negative individuals (HNTN) and 14 HIV positive TB negative individuals (HPTN) prior to ART initiation (pre-ART) and on virally suppressive ART (on ART). P-value reported from two-sided Mann-Whitney tests with threshold for significance p = 0.025 after Bonferroni correction for 2 comparisons. Figure 4B: Paired CD161++CD8+ T-cell frequencies in HIV-positive individuals prior to and following virally suppressive ART (p-value reported for Wilcoxon matched pairs test). Figure 4C: FACS plots (gated on the CD8+ T cell population) displaying the lack of change in the CD161++ CD8+ population (co-stained with the MAIT cell semi-invariant TCR, Vα7.2) prior to and after 6 months of ART in a representative subject.</p

Clinical and demographic characteristics of the individuals whose samples were used to assess the frequency and phenotypic and functional profile of the CD161++ CD8+ T cell population.

<p>HNTN: HIV negative, tuberculosis (TB) negative; HNLTBI: HIV negative, latent tuberculosis infection (LTBI)); HNTP: HIV negative, TB positive; HPTN: HIV positive, TB negative; HPLTBI: HIV positive, LTBI; HPTP: HIV positive, TB positive. Except where designated, all values are expressed as median (range).</p

Impact of HIV and TB mono- and co-infection on CD161++ CD8+ T cell frequencies.

<p>Figure 2A: FACS plots (gated on the CD3+ T cell population) show CD161 and CD8 co-staining on representative individuals from 6 different clinical groups: HIV negative and TB negative (HNTN), HIV negative with latent TB infection (HNLTBI), HIV negative with active TB (HNTP), HIV positive TB negative (HPTN), HIV positive with latent TB infection (HPLTBI) and HIV positive with active TB (HPTP). Figure 2B: Aggregate data demonstrating CD161++ CD8+ T cell frequency (median and interquartile range) in 6 different groups: HNTN (n = 18), HNLTBI (n = 16), HNTP (n = 8), HPTN (n = 13), HPLTBI (n = 15) HPTP (n = 10). P-values reported for two-sided Mann-Whitney tests, with a p-value threshold for significance of 0.01 after Bonferroni correction for 5 comparisons. Figure 2C: CD161++CD8+ T cell frequency in all subjects with HIV-infection showed no significant correlation with either CD4 count (cells/µl) or HIV viral load (copies/ml).</p

Lipidomics show that loss of LprG-Rv1410 results in triacylglyceride (TAG) accumulation in <i>Mtb</i>.

<p>(A, left) Strains used in this study. (A, right) Schematic showing predicted localization of proteins encoded by genes manipulated in this study. (B) Positive mode comparative lipidomics analysis from stationary phase <i>M</i>. <i>tuberculosis</i> Mutant 2 (Mut2) and parental wild-type (WT) strains yielded 7487 total events (black and red) with 309 (red) that meet change criteria of a two-fold increase in Mut2 compared to WT at a corrected p <0.05 (student’s paired t-test, Gene Pattern, Broad Institute). Each dot represents the mean intensity over three biological replicates for a given molecular event in Mut2 compared to WT. For thirty-two of these the <i>m/z</i> values match the expected masses of TAG alkylforms (blue) detected as ammonium and hydrogen adducts. (C) Collision-induced dissociation mass spectrometry of a representative TAG (TAG 58:0, <i>m/z</i> 564.93). (D-E) Mean intensity values for molecular events mapping to TAG isoforms (ammonium adducts) with the indicated total number of carbons:unsaturations found in all alkyl chains in (D) WT, Mut1 and Mut2 and (E) WT, Mut2, and Complement (Comp2) strains. Error bars show mean +/- SD. * p<0.05, ** p<0.01, ***p<0.001, in (D) Mut1 (†) or Mut2 (*) vs. WT and (E) WT (*) or Comp2 (†) vs. Mut2; 2-way ANOVA with Bonferroni post-test correction.</p