Mycobacterium tuberculosis infection boosts B cell responses to unrelated pathogens

Antigens from Mycobacterium tuberculosis (M.tb), have been shown to stimulate human B cell responses to unrelated recall antigens in vitro. However, it is not known whether natural M.tb infection or whether vaccination with the related species, Mycobacterium bovis BCG, has a similar effect. This study investigated the effects of M.tb infection and BCG vaccination on B cell responses to heterologous pathogen recall antigens. Antibodies against several bacterial and viral pathogens were quantified by ELISA in 68 uninfected controls, 62 individuals with latent TB infection (LTBI) and 107 active pulmonary TB (APTB) cases, and 24 recently BCG-vaccinated adolescents and naive controls. Antibody avidity was investigated using surface plasmon resonance and B cell ELISPOT assays were used to measure plasmablast and memory B cell responses (MBC) in APTB cases and healthy donor controls. APTB was associated with higher levels of antibodies to tetanus toxoid (TT), diphtheria toxoid, respiratory syncytial virus, measles virus and Kaposi's sarcoma herpesvirus, compared to uninfected controls. Vaccination with BCG did not alter levels of antibodies against heterologous pathogens. TT-specific antibody avidity was increased in APTB and the ratio of TT-specific plasmablasts to MBCs in the APTB cases was 7:1. M.tb infection boosts serological memory to heterologous pathogens in human subjects and this process may be driven by polyclonal activation of memory B cells.