RESUMO
OBJECTIVE: To investigate the effect of M. tuberculosis infection on actin in host-cells. METHODS: The form and distribution of fibrous actin and changes of actin expression were observed by confocal microscopy and Western blot analysis in macrophages infected with either M. tuberculosis H(37)R(a) or H(37)R(v) at 6 h, 12 h and 24 h after infection. Non-infected macrophages or macrophages treated with dead M. tuberculosis H(37)R(v) served as controls. RESULTS: F-actin aggregated and the actin expression was suppressed in macrophages infected with H(37)R(a) or H(37)R(v), and the effect appeared earlier in cells infected by the virulent H(37)R(v) strain than in cells infected by the avirulent H(37)R(a) strain. In macrophages treated with the dead H(37)R(v), actin was not affected. CONCLUSION: The results suggest that in the process of infection, M. tuberculosis evades the bactericidal mechanisms possibly by secretion of certain proteins or factors which affect the host-cell actin.
