This study investigates the influence of M. tuberculosis infection on immune-activation biomarkers, both in HIV-infected and -uninfected subjects.
Forty-eight treatment naïve HIV-infected patients and 74 HIV-uninfected subjects were recruited and divided into groups according to their M. tuberculosis-infection status: latent tuberculosis infection (LTBI), active tuberculosis (TB) and no evidence of M. tuberculosis infection. The expression of cellular markers CD38 and HLA-DR on circulating CD8 T-lymphocytes and the plasmatic levels of soluble markers IL-6, sCD14 and D-Dimer were measured and compared between groups. The HIV-infected patients with no evidence of M. tuberculosis or with LTBI who initiated antiretroviral treatment were tested again for these biomarkers once viral suppression was reached.
In both HIV-infected and -uninfected groups, patients with TB had higher levels of immune-activation markers than subjects with LTBI and with no evidence of M. tuberculosis. Among the HIV-uninfected subjects, no significant difference in biomarker level was found between those presenting LTBI and those with no evidence of M. tuberculosis. The effect of LTBI on activation biomarkers in the HIV-infected groups was inconclusive because of the small number of individuals in the HIV+/LTBI group. sCD14 and D-Dimer levels were significantly higher in the TB-only group than in the HIV-only group.
While TB is associated with an increase in biomarkers of immune-activation, the effect of LTBI is less evident. Further investigation is warranted and according to our results, soluble markers may offer greater sensitivity for the evaluation of M. tuberculosis-associated immune-activation than cellular markers.