E3 ubiquitin ligase CBLB regulates innate immune responses and bacterial dissemination during nontuberculous mycobacteria infection

Abstract

Nontuberculous Mycobacteria (NTM) are emerging opportunistic pathogens causing pulmonary infection to fatal disseminated disease. NTM infections are steadily increasing in children and adults, and immune-compromised individuals are at a greater risk of fatal infections. The NTM disease's adverse pathology and the drug resistance to antibiotics have further worsened the therapeutic measures. Innate immune regulators are potential targets for therapeutics to NTM, especially in T cell suppressed population and many ubiquitin ligases modulate pathogenesis and innate immunity during infections, including mycobacterial infections. Here, we investigated the role of an E3 ubiquitin ligase, Casitas B-lineage lymphoma proto-oncogene B (CBLB), in immunocompromised mouse models of NTM infection. We found that CBLB is essential to prevent bacterial growth and dissemination. Cblb-deficiency debilitated NK cells, inflammatory monocytes, and macrophages in vivo. However, Cblb-deficiency in macrophages did not wane its ability to inhibit bacterial growth or production of reactive oxygen species nor the IFNγ production by NK cells in vitro. CBLB restricted the NTM growth and dissemination by promoting early granuloma formation in vivo. Our study shows that CBLB bolsters innate immune responses and helps prevent the dissemination of NTM during compromised T-cell immunity.

Keywords: NK cells; Nontuberculous mycobacteria (NTM); T-cell lymphopenia; granuloma; macrophages; monocytes.