Type I Interferon is Pathogenic During Chronic Mycobacterium africanum Infection

Type I interferons (IFNs, including IFN-alpha beta) contribute to the pathogenesis of Mycobacterium tuberculosis strains that induce high IFN-alpha beta levels. In the current study we examined the role of IFN-alpha beta during infection with a Mycobacterium africanum strain that induces low IFN-beta levels. We infected wild-type and IFN-alpha beta receptor knockout mice with M. africanum and monitored bacterial growth, lung disease, and survival over 292 days. We found reduced lung bacterial burdens and less severe histopathological findings in the absence of IFN-alpha beta signaling. We conclude that IFN-alpha beta is pathogenic during chronic M. africanum infection and that the pathogenic effects may be mediated through poorer control of bacterial growth.