Mycobacterium abscessus induces immune suppression in cystic fibrosis macrophages

Introduction People with cystic fibrosis (pwCF) are highly susceptible to chronic lung infections with Mycobacterium abscessus ( MAB ), a nontuberculous mycobacterium (NTM) that is intrinsically resistant to antibiotics. While macrophage dysfunction is recognized in CF, responses to MAB in primary human macrophages remain poorly defined. Methods We investigated the innate immune response to MAB using peripheral blood monocytes and monocyte-derived macrophages from pwCF and healthy donors. Macrophages were infected with opsonized smooth ( MAS ) or rough ( MAR ) isolates of MAB morphotypes at low multiplicity of infection. After removal of extracellular bacteria, intracellular burden, oxidative burst, NOX2 activation, and cytokine production were assessed at 2- and 24-hours post-infection. Results MAB uptake was comparable across all groups and non-CF macrophages showed no difference in intracellular MAR or MAS at 24h. In contrast, CF macrophages harbored significantly more intracellular MAR at 24 hours, a phenotype recapitulated by CFTR knockdown in non-CF macrophages. MAB -infected CF macrophages demonstrated a significantly reduced oxidative burst and diminished NOX2 p47phox phosphorylation. Non-CF macrophages treated with CFTR inhibitor mimicked the reduced oxidative burst. CF macrophages also exhibited an altered cytokine response with significantly elevated IL-8 but decreased IL-1β relative to healthy macrophages. Notably, MAR -infected CF macrophages secreted significantly less TNF-α compared with non-CF macrophages and exhibited markedly reduced apoptosis compared with MAR -infected non-CF and MAS -infected CF macrophages. Discussion These findings demonstrate that CF macrophages are intrinsically impaired in their ability to control the virulent rough MAB morphotype, highlighting a potential mechanism for persistent NTM infection in pwCF and underscoring the need for host-directed therapies.