The host-directed therapeutic imatinib mesylate accelerates immune responses toMycobacterium marinuminfection and limits pathology associated with granulomas

Abstract

Mycobacterial infections, including those caused by members of the mycobacterium tuberculosis complex [MTC] and Nontuberculous mycobacteria [NTM], can induce widespread morbidity and mortality in people. Mycobacterial infections cause both a delayed immune response, which limits rate of bacterial clearance, and formation of granulomas, which contain bacterial spread, but also contribute to lung damage, fibrosis, and morbidity. Granulomas also limit access of antibiotics to bacteria, which may facilitate development of resistance. MTC members resistant to some or all antibiotics are estimated to account for a third of deaths from tuberculosis [TB], and newly developed antibiotics have already engendered resistance, pointing to the need for new therapeutic approaches. Imatinib mesylate, a cancer drug used to treat chronic myelogenous leukemia [CML] that targets Abl and related tyrosine kinases, is a possible host-directed therapeutic [HDT] for mycobacterial infections, including TB. Here, we use the murine Mycobacterium marinum [Mm] infection model, which forms quantifiable granulomas on the tails, in conjunction with transcriptomic analysis of the tail lesions. The data indicate that imatinib induces gene signatures indicative of immune activation at early time points post infection that resemble those seen at later ones, suggesting that imatinib accelerates but does not substantially alter anti-mycobacterial immune responses. Moreover, focusing on the TNFα pathway, which is induced by imatinib, we show that imatinib promotes cell survival in infected bone marrow-derived macrophages [BMDMs] in a manner that depends on caspase 8. Moreover, imatinib limits formation and growth of granulomas, an effect abrogated in mice lacking caspase 8. These data provide evidence for the utility of imatinib as an HDT for mycobacterial infections in accelerating immune responses, and limiting pathology associated with granulomas, and thus mitigating post-treatment morbidity.