Mycobacterium tuberculosis-Specific T-Cell Responses Are Impaired During Late Pregnancy With Elevated Biomarkers of Tuberculosis Risk Postpartum

Background. Pregnancy is a risk factor for progression from latent tuberculosis infection to symptomatic tuberculosis. However, how pregnancy influences T-cell responses to Mycobacterium tuberculosis is unknown. Methods. We measured M. tuberculosis-specific cytokines, T-cell memory markers, and overall CD4(+) and CD8(+) T-cell activation by flow cytometry from 49 women (18 with and 31 without HIV) who became pregnant while enrolled in a randomized controlled trial of preexposure prophylaxis for HIV. We analyzed data using COMPASS, an established statistical method for evaluating overall antigen-specific T-cell responses. Results. Pregnant women with latent tuberculosis infection demonstrated significantly diminished M. tuberculosis-specific CD4(+) cytokine responses in the third trimester (COMPASS polyfunctional score [PFS], 0.07) compared before (PFS, 0.15), during (PFS, 0.13 and 0.16), and after pregnancy (PFS, 0.14; P = .0084, Kruskal-Wallis test). Paradoxically, M. tuberculosis-specific CD8(+) cytokines and nonspecifically activated T-cells increased during late pregnancy. Nonspecific T-cell activation, a validated biomarker for progression from latent tuberculosis infection to tuberculosis disease, increased in latent tuberculosis infection-positive women postpartum, compared with latent tuberculosis infection-negative women. Conclusions. Pregnancy-related functional T-cell changes were most pronounced during late pregnancy. Both M. tuberculosis-specific T-cell changes during pregnancy and increases in immune activation postpartum may contribute to increased risk for tuberculosis progression.