Protective efficacy of bivalent anti-flagellin IgY against <i>Pseudomonas aeruginosa</i> infection in acute pneumonia and burn wound murine models

The rising emergence of antimicrobial-resistant Pseudomonas aeruginosa strains necessitates effective therapeutic strategies like antibody-based immunotherapy. Flagellin is crucial in P. aeruginosa infection development. This study evaluated the antibacterial efficacy of bivalent immunoglobulin Y (IgY) raised against both A and B flagellins. IgY's immunoreactivity and specificity were examined via ELISA and immunoblot analysis. Functional assays, including motility, biofilm formation, and opsonophagocytic tests, examined the antibody's inhibitory effects on diverse bacterial functions. Murine models of acute pneumonia and burn wounds, using both standard and nosocomial strains, were employed to assess in vivo protection. Anti-FlaAB IgY exhibited higher immunoreactivity and specificity against PAO1 (FlaB+) than PAK (FlaA+). The bivalent antibody demonstrated admissible potency compared to previously characterized monovalent IgYs under similar conditions. Passive immunotherapy provided 100% and 40% protection in burned mice infected with standard and nosocomial strains, respectively, and ensured 100% protection in an acute pneumonia model. Although both anti-FlaB and anti-FlaAB IgYs showed similar efficacy in vivo, certain in vitro assays revealed that monovalent antibodies had reduced activity against heterologous strain at the lowest examined concentrations. Considering potential fluctuations in antibody concentration and the need for broad coverage against both flagellin types, the bivalent formulation emerges as a more optimal and flexible choice for passive immunotherapy in burn wound infections.