Stages of pregnancy and HIV affect diagnosis of tuberculosis infection and Mycobacterium tuberculosis (MTB)-induced immune response: Findings from PRACHITi, a cohort study in Pune, India

Background: Accurate tuberculosis infection (TBI) tests are critical for pregnant women, especially those with HIV, who have a high risk of TB disease. Methods: We enrolled interferon gamma release assay (IGRA)+ pregnant women with and without HIV in a longitudinal study, followed up at delivery and 6 months postpartum. Tuberculin skin test (TST) and IGRA were compared by HIV status at each timepoint. Results: Of 165 enrolled IGRA+ pregnant women: 35 (21%) had HIV and were on antiretroviral therapy with median CD4 of 476 (IQR 399-586). Compared to antepartum, significantly fewer women remained IGRA+ at delivery [HIV + n = 21/35 (62%, p = 0.009); HIV-n = 100/130 (77%, p = 0.002)] and postpartum [HIV + n = 30/35 (87%, p = 0.03); HIV- n = 116/130 (89%, p = 0.01)]. IGRA/TST discordance was high in pregnant women (HIV + : 51%; HIV-: 25%). Median IFN-gamma was lowest for all women at delivery; significantly lower in women with HIV at all timepoints compared to women without HIV. TB incidence was 50/1000 person-years and 18/1000 person-years among women with and without HIV respectively. Conclusions: Pregnancy affects TBI test results and reduces IFN-gamma response to M. tuberculosis stimulation. Despite adequate CD4 counts, women with HIV express less IFN-gamma than women without HIV, which may explain the high TB incidence in postpartum women with HIV. (C) 2021 The Author(s). Published by Elsevier Ltd on behalf of International Society for Infectious Diseases.