Effects of intense exercise on innate bacterial killing in close contacts of patients with TB/MDR-TB

Close contacts of patients with multidrug-resistant tuberculosis (MDR-TB) face a high infection risk due to limited chemoprophylaxis. Exercise is known to enhance the lung defense mechanisms. This study evaluated whether intense exercise can boost innate bacterial immunity in close contact by improving the in vitro killing of intracellular Mycobacterium tuberculosis.

Twelve males (20-40 years) from a tuberculosis clinic were randomly assigned to exercise or no-exercise groups. The exercise group performed high-intensity cycling at 70-80 % of heart rate reserve (HRR) for 30-60 min, three days/week for 12 weeks. The no-exercise group engaged in self-directed exercise. Blood monocytes were isolated before and after the program and differentiated into inflammatory M1 and anti-inflammatory M2 macrophages. We infected the isolated monocytes and M1 and M2 macrophages with the mCherry-expressing laboratory reference M. tuberculosis strain H37Rv and a local strain of MDR-TB with a multiplicity of infection (MOI) is 10 for 0 and 72 h, and mycobacterial survival was determined via high content imaging.

Mycobacterial survival percentages were normalized to the 0-h infection control. In the exercise group, H37Rv survival was significantly decreased in monocytes, M1, and M2 macrophages compared to that in the no-exercise group. However, the local MDR strain reduced the survival of M1 macrophages but not that of monocytes or M2 macrophages. Additionally, cytokine secretion after H37Rv infection in monocytes showed a significant reduction in IL-1β levels, whereas no significant changes were observed in M1 and M2 macrophages.

Intense exercise may enhance mycobacterial killing in individuals exposed to TB, particularly inflammatory M1 macrophages. Promoting intense exercise among close contacts of patients with TB may be beneficial.