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 Va7.2. 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.

Authors: 
Emily B. Wong
Ngomu Akeem Akilimali
Pamla Govender
Zuri A. Sullivan
Cormac Cosgrove
Mona Pillay
David M. Lewinsohn
William R. Bishai
Bruce D. Walker
Thumbi Ndung’u
Paul Klenerman
Victoria O. Kasprowicz
Journal: 
PLOS ONE
Volume: 
8
Issue: 
12
Publication Date: 
December, 2013
IBN number: 
e83474