The Indicine X-linked CYBBL237M Mutation Can Suppress Intracellular Infection with Tubercle Bacilli.

Indicine cattle exhibit superior resistance to Mycobacterium bovis infection compared to taurine breeds, revealing divergent genetic mechanisms underlying bovine tuberculosis (bTB) resilience. Previous research has demonstrated that Cytochrome b-245 (CYBB) gene variants are associated with Mendelian susceptibility to Mycobacterium tuberculosis complex (MTBC) infections. In this study, we analyzed the X-chromosomal sequences from 258 female cattle and identified a divergent missense variant (L237M) in the CYBB gene. This variant occurs at high frequencies in indicine populations. Functional studies using murine macrophages revealed that CYBB  L237M mitigates M. tuberculosis-induced ferroptosis by elevating glutathione synthesis and glutathione peroxidase 4 expression. Mechanistically, the L237M substitution enhances the stability of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 2 (NOX2) and p22phox complex (NOX2-p22), which is critical for the generation of phagosomal reactive oxygen species and bacterial clearance. Our findings demonstrate that CYBB  L237M promotes intracellular MTBC elimination through ferroptosis suppression, partially explaining the superior bTB resistance of indicine cattle. This study highlights X-chromosomal genetic variation as an evolutionary driver of innate immunity against mycobacterial infections, with implications for breeding strategies and host-directed tuberculosis therapies. The CYBB variant exemplifies how cattle subspecies divergence can illuminate conserved antimicrobial defense mechanisms in mammals.