Nasal delivery of <i>Lacticaseibacillus rhamnosus</i> GG modulates respiratory immune responses and attenuates <i>Mycoplasma pneumoniae</i> pneumonia in a murine model

The increasing prevalence of antibiotic-resistant <i>Mycoplasma pneumoniae</i> pneumonia (MPP), together with the absence of an effective vaccine, highlights the critical demand for alternative therapeutic approaches. This study demonstrates that intranasal delivery of <i>Lacticaseibacillus rhamnosus</i> GG (LGG) significantly mitigates pulmonary inflammation and decreases bacterial load in a mouse model of MPP, both prophylactically and therapeutically. Notably, LGG strengthens essential immune defenses by promoting alveolar macrophage recruitment, increasing secretory IgA in the airways, and stimulating systemic IgG. It also modulates cytokine production, suppressing pro-inflammatory mediators while enhancing anti-inflammatory IL-10. These findings support intranasal LGG administration as a strategy with promising translational potential for MPP.