HMOX1 and tuberculosis: To further examine the utility of HO-1 as an accurate biomarker of active Mtb infection in humans and to assess the impact of HIV coinfection on enzyme expression, we performed a prospective analysis of HO-1 levels in a South African cohort of TB and HIV-TB patients prior to and at an early time point (8 weeks) as well as at 20 weeks post-ATT.