Interferon-γ responses to Mycobacterium tuberculosis Rpf proteins in contact investigation

Mycobacterium tuberculosis Resuscitation-promoting factor proteins (Rpf) induce stronger T-cell responses in latently infected individuals (LTBI) than in pulmonary tuberculosis patients (PTB), but there are scarce data concerning the responses to Rpf among LTBI with different contact levels. We therefore enrolled LTBI individuals infected through household contacts with PTB as well as people with community exposure who were determined to be LTBI through Interferon-γ (IFN-γ) release assays (IGRAs) and TB antibodies test, and we studied interferon-gamma responses to Rv0867c and Rv2389c which demonstrated the highest recognition of all Rpfs. The results demonstrated that LTBI infected through household contacts possessed higher interferon-gamma production and higher frequencies of CD4(+)IFN-γ(+) T-cells to Rv0867c and Rv2389c than did the community exposed individuals. These findings suggest that the interferon-gamma response to Rv0867c and Rv2389c may help to distinguish LTBI caused by different levels of exposure to M. tuberculosis.