Protective efficacy of a PcrV-based vaccine formulated with chitosan nanoparticles against Pseudomonas aeruginosa infection in burn and sepsis mouse models.

Abstract

Pseudomonas aeruginosa is an opportunistic Gram-negative pathogen and a major clinical concern due to its multidrug resistance and extensive virulence repertoire. In this study, recombinant PcrV protein was formulated with Alum and chitosan nanoparticles (CS-NPs) as co-adjuvants to enhance immunogenicity. CS-NPs were prepared via ionic gelation and characterized for morphology and charge. BALB/c mice were immunized with formulations containing r-PcrV + Alum + Nanochitosan, r-PcrV + Alum, r-PcrV + Nanochitosan, or Nanochitosan + Alum or PBS (control). This was followed by burn induction, after which the burn wounds were intentionally infected with Pseudomonas aeruginosa PAO1, as well as challenged in a septicemia model. Indirect ELISA was used to evaluate both humoral and cellular immune responses. Vaccine efficacy was further assessed through opsonophagocytic activity and quantification of bacterial load in internal organs and skin tissues. Mice receiving the r-PcrV + Alum + Nanochitosan formulation exhibited significantly elevated IFN-γ and IL-4 cytokine levels, higher total IgG, IgG1, and IgG2a responses, and enhanced opsonophagocytic activity compared to other experimental groups (p < 0.0001). This group also demonstrated markedly reduced bacterial loads in liver, spleen, kidney, and skin tissues, as well as superior survival rates 75% in burn and 87.5% in sepsis models, indicating strong protective immunity. The synergistic combination of Alum and Nanochitosan effectively elicited both Th1- and Th2-mediated responses, leading to improved pathogen clearance and immune balance. These findings highlight the potential of the r-PcrV + Alum + Nanochitosan formulation as a promising vaccine candidate against multidrug-resistant P. aeruginosa, a major cause of morbidity and mortality in burn patients. Future investigations should explore alternative adjuvant combinations, additional virulence-associated antigens, and clinical evaluation of this formulation to advance toward translational application.