The impact of maternal infection with Mycobacterium tuberculosis on the infant response to BCG immunisation
Bacille Calmette-Guérin (BCG) immunization provides variable protection against tuberculosis. Prenatal antigen exposure may have lifelong effects on responses to related antigens and pathogens. We therefore hypothesized that maternal latent Mycobacterium tuberculosis infection (LTBI) influences infant responses to BCG immunization at birth. We measured antibody (n = 53) and cellular (n = 31) responses to M. tuberculosis purified protein derivative (PPD) in infants of mothers with and without LTBI, in cord blood and at one and six weeks after BCG. The concentrations of PPD-specific antibodies declined between birth (median [interquartile range (IQR)]) 5600 ng ml(-1) [3300-11 050] in cord blood) and six weeks (0.00 ng ml(-1) [0-288]). Frequencies of PPD-specific IFN-γ-expressing CD4(+)T cells increased at one week and declined between one and six weeks (p = 0.031). Frequencies of IL-2- and TNF-α-expressing PPD-specific CD4(+)T cells increased between one and six weeks (p = 0.019, p = 0.009, respectively). At one week, the frequency of PPD-specific CD4(+)T cells expressing any of the three cytokines, combined, was lower among infants of mothers with LTBI, in crude analyses (p = 0.002) and after adjusting for confounders (mean difference, 95% CI -0.041% (-0.082, -0.001)). In conclusion, maternal LTBI was associated with lower infant anti-mycobacterial T-cell responses immediately following BCG immunization. These findings are being explored further in a larger study.