31 Non-Tuberculous Mycobacteria (NTM) are ubiquitous in nature, present in soil and water, and 32 cause primary leading to disseminated infections in immunocompromised individuals. NTM 33 infections are surging in recent years due to an increase in an immune-suppressed population, 34 medical interventions, and patients with underlying lung diseases. Host regulators of innate 35 immune responses, frontiers for controlling infections and dissemination, are poorly defined 36 during NTM infections. Here, we describe the role of CBLB, an E3-ubiquitin ligase, for innate 37 immune responses and disease progression in a mouse model of NTM infection under 38 compromised T-cell immunity. We found that CBLB thwarted NTM growth and dissemination 39 in a time-and infection route-dependent manner. Mechanistically, we uncovered defects in 40 many innate immune cells in the absence of Cblb, including poor responses of NK cells, 41 inflammatory monocytes, and conventional dendritic cells. Strikingly, Cblb-deficient 42 macrophages were competent to control NTM growth in vitro. Histopathology suggested the lack 43 of early formation of granulomatous inflammation in the absence of CBLB. Collectively, CBLB 44 is essential to mount productive innate immune responses and help prevent the dissemination 45 during an NTM infection under T-cell deficiency. 46 47 48 49 50 51 52 53 54 55 56shown to downregulate Syk kinase, and its ablation/inhibition led to enhanced production of 103 proinflammatory cytokines, the release of reactive oxygen species (ROS), and fungal killing by 104 macrophages (Wirnsberger et al., 2016;Xiao et al., 2016;Zhu et al., 2016). Further, CBLB has 105 regulatory roles in dendritic cells (DC) by modulating the functions, both positively and 106 negatively (Arron et al., 2001;Wallner et al., 2013;Tang et al., 2019). Nevertheless, CBLB 107 functions in innate immunity during mycobacterial diseases are not deciphered.
109In this study, we systematically evaluated the role of CBLB for innate immunity and 110 dissemination of bacteria in a mouse model of NTM infection with deficient T-cell responses. 111 We assessed the bacterial control and innate immune cell numbers/responses following both 112 intratracheal and intravenous infections for up to 5 months. We describe the critical role of 113 CBLB in dictating the pathogenesis of NTM infection that was associated with multiple 114 defective or altered dynamics of innate immune cell numbers or their responses. 149 150 Mice: The OT-I Tg (TCRα/TCRβ specific for OT-I epitope; Stock #: 003831) and B6.PL-151 Thy1a/Cy/Thy1.1 (Thy1.1; Stock #: 000406) were purchased from Jackson Laboratories. Cblb -/-152 mice were provided by P.S. Ohashi (University of Toronto, Ontario, Canada) with permission 153 from Josef Penninger (IMBA, Austria). OTI-Tg mice were backcrossed with Cblb -/to generate 154 OT-I Tg-Cblb -/mice at the UW-Madison facility and were transferred to the current facility with 155 the facilitation from Bruce Klein, UW-Madison. All mice were maintained under specific-15...
