Role of Alkylhydroperoxidase Rv2159c in the Oxidative Stress Response and Virulence of Mycobacterium tuberculosis

<em>Mycobacterium tuberculosis</em>, which causes tuberculosis, is one of the leading infectious agents worldwide with a high rate of mortality. Following aerosol inhalation, <em>M. tuberculosis</em> primarily infects the alveolar macrophages, which results in a host immune response that gradually activates various antimicrobial mechanisms, including the production of reactive oxygen species (ROS), within the phagocytes to neutralize the bacteria. <em>OxyR</em> is the master regulator of oxidative stress response in several bacterial species. However, due to the absence of a functional <em>oxyR </em>locus in <em>M. tuberculosis,</em> the peroxidase stress is controlled by alkylhydroperoxidases. <em>M. tuberculosis </em>expresses alkylhydroperoxide reductase to counteract the toxic effects of ROS. In the current study, we report the functional characterization of an ortholgue of alkylhydroperoxidase family member, Rv2159c, a conserved protein with putative peroxidase activity, during stress response and virulence of <em>M. tuberculosis</em><em>. </em>We generated a gene knockout mutant of <em>M. tuberculosis </em>Rv2159c (MtbΔ2159) by specialized transduction. The MtbΔ2159 was sensitive to oxidative stress and exposure to toxic transition metals. In a human monocyte (THP-1) cell infection model, MtbΔ2159 showed reduced intracellular survival and increased expression of pro-inflammatory molecules, includingIL-1β, IP-10 and MIP-1α, compared to the wild type <em>M. tuberculosis</em> and Rv2159c-complemented MtbΔ2159 strains. Similarly, in a guinea pig model of pulmonary infection, MtbΔ2159 displayed growth attenuation in the lungs, compared to the wild type <em>M. tuberculosis</em> and Rv2159c-complemented MtbΔ2159 strains<em>. </em>Our study suggests that Rv2159c has a significant role in maintaining the cellular homeostasis during stress and virulence of <em>M. tuberculosis</em>.