Attenuation of a local Mycobacterium avium subsp paratuberculosis virulent strain by homologous recombination.

Paratuberculosis (PTB) is a disease that affects many countries around the world. One of the strategies that could contribute to its control is the development of effective vaccines that prevent the dissemination of Mycobacterium avium subsp. paratuberculosis, the causal agent. Previously, we showed the humoral and cellular immune response induced by a novel vaccine candidate against PTB based on the inactivated Map6611 virulent strain. In the present study, we independently deleted two operons, mce4 and lprG-p55, possibly associated with Map virulence. Map6611_Δmce4 and Map6611_ΔlprG-p55 virulence and immune response were evaluated in two experimental models. We observed that the deletion of mce4 does not attenuate Map6611 virulence in bovine macrophages or mice but induced significant lesions in mice and increased proinflammatory cytokines production. On the other hand, we observed that the deletion of lprG-p55 attenuates the virulence of Map6611 in both experimental models and induces a significant immune response. The results of this work demonstrated the role of both operons in Map pathogenesis and suggested that the attenuated mutant Map6611_ΔlprG-p55 could be evaluated in the future as a live vaccine candidate.