Mycobacteriophage D29-Derived LysB Enhances Anti-Tubercular Therapy in Experimental Pulmonary Tuberculosis

Adjunctive therapies that enhance the efficacy of existing antitubercular drugs are needed for drug-resistant tuberculosis. We evaluated the efficacy of intranasally administered recombinant D29 LysB, a mycobacteriophage-derived mycolylarabinogalactan esterase, in murine and guinea pig models of pulmonary tuberculosis. BALB/c mice and guinea pigs were aerosol-infected with Mycobacterium tuberculosis H37Rv and treated for 4 weeks with LysB alone or with standard antitubercular therapy (ATT: rifampicin, isoniazid, pyrazinamide). Outcomes included pulmonary and extrapulmonary bacterial burden (CFU), lung and spleen histopathology, cytokine profiling, and humoral immune responses. LysB monotherapy produced modest pulmonary CFU reductions. When given adjunctively with ATT, LysB produced an additional 0.6-0.7 log10 reduction in lung CFU compared with ATT alone and decreased splenic dissemination in both species. Combination therapy improved tissue pathology, reducing granulomatous involvement and preserving pulmonary architecture. LysB treatment increased TNF- with a moderate rise in IL-10, a profile consistent with enhanced antibacterial immunity without excessive inflammatory damage. Repeated intranasal administration was well tolerated; no IgE-mediated hypersensitivity was detected. LysB-specific IgG developed but did not diminish therapeutic efficacy. These results show that intranasal D29 LysB augments the bactericidal and histopathological effects of standard ATT in vivo and support further development of inhaled phage-derived lysins as adjunctive therapies for drug-resistant tuberculosis. ImportanceTuberculosis remains a major cause of infectious mortality worldwide, and the increasing burden of multidrug-resistant and extensively drug-resistant disease continues to challenge effective treatment. New therapeutic approaches that complement conventional antibiotics are urgently needed. In this study, intranasally delivered recombinant mycobacteriophage-derived LysB was well tolerated and enhanced treatment efficacy in experimental pulmonary tuberculosis. Adjunctive LysB improved bacterial clearance, reduced tissue pathology, and modulated host immune responses in both murine and guinea pig models. These findings highlight phage-derived endolysins as promising inhalable adjunctive therapeutics for drug-resistant tuberculosis.