Preparation and functional evaluation of an alginate-targeted monoclonal antibody against Pseudomonas aeruginosa

Pseudomonas aeruginosa is a critical-priority pathogen responsible for life-threatening infections in immunocompromised individuals, yet its extensive antigenic heterogeneity has impeded the development of immunotherapeutics. Alginate, a structurally conserved surface polysaccharide that forms the backbone of the biofilm matrix of mucoid P. aeruginosa strains in chronic infections, represents a compelling target. Here, we report the generation and functional evaluation of mAb 546B, a murine IgG1 monoclonal antibody directed against the synthetic mannuronic acid tetrasaccharide epitope 1. This antibody bound to the surface alginate of both mucoid and nonmucoid P. aeruginosa strains and induced pronounced bacterial aggregation. Notably, 546B inhibited biofilm formation, disrupted established biofilms, and reduced the minimum inhibitory concentration of meropenem across multiple strains. In a bacterial clearance model, 546B monotherapy reduced lung bacterial burden compared to PBS controls, and its combination with meropenem achieved a marked reduction accompanied by significantly attenuated pulmonary inflammation and histopathological injury. In a lethal PAO1 pneumonia model, 546B alone improved the 7-day survival rate of mice, and combination with meropenem could further enhance the survival rate. These findings establish 546B as a promising monoclonal antibody that targets alginate-mediated biofilms, supporting its further development as a passive immunotherapeutic against P. aeruginosa infection.