Antibodies raised against divalent type b flagellin and pilin provide effective immunotherapy against Pseudomonas aeruginosa infection of mice with burn wounds.

Burn wound infections caused by multidrug-resistant Pseudomonas aeruginosa strains are a serious challenge to therapy because of the complex pathogenesis and paucity of new effective antibiotics. Therefore, there is renewed interest in developing antibody-based therapeutic strategies. Immunotherapy strategies typically target selected virulence factors that are expressed by the majority of clinical strains of P. aeruginosa, particularly because virulence factors mediate infection. Here we used a murine model of burn wound infection to evaluate the efficacy of antibodies raised against the divalent type b flagellin and PilA (flagellin b + PilA), as acute virulence factors, to prevent and treat infection. Antibodies to flagellin b + PilA exhibited superior synergistic effects that improved opsono-phagocytosis and cell invasion compared with antibodies to each monovalent flagellin b or PilA. Further, when used for prophylaxis, the antibodies against flagellin b + PilA and combined therapeutic and prophylactic regimens markedly improved the survival of mice infected with disparate P. aeruginosa strains from 91.6% to 100% compared with treatment using imipenem. Therefore, antibodies against flagellin b + PilA interfere with the activities of their respective cognate individual target antigens and enhance coverage against clinical strains of P. aeruginosa that may not express one of these two virulence factors.