Passive immunization with chitosan-loaded biofilm-associated protein against Acinetobacter baumannii murine infection model

Vaccination of at-risk people against Acinetobacter baumannii is a promising method to inhibit infections. Mucociliary clearance in the nasal cavity and hard transportation of protein agents over the epithelial barrier are justifying the development of encapsulated vaccines. In this study, we used chitosan as an adjuvant and antigen delivery system. Mucosal immunity brought about by the conserved region of A. baumannii biofilm-associated Protein (Bap) loaded on chitosan was assessed following intranasal (i.n) inoculation of mice. Mucosal and systemic immune responses were evaluated. Passive immunization was studied both in vivo and in vitro. Antigen-specific IgG and IgA antibodies were raised in serum and fecal and lung extractions in mice administered intranasally with Bap-chitosan particles. Passive immunization with serum obtained from chitosan-Bap immunized mice conferred higher survival compared to immunization with subcutaneously immunized mice serum. Conclusions: Passive immunization with antibodies triggered with chitosan-Bap could be an additional immunization strategy for preventing A. baumannii pneumonia. •Drug resistance calls for alternate strategies to fight A. baumannii infections.•A predicted Bap706–1076 region of 371 residues was selected as a vaccine candidate.•Bap706–1076 was loaded on chitosan as an adjuvant and antigen delivery system.•Specific IgG and IgA antibodies raised in mice serum, fecal and lung.•Chitosan-Bap derived passive immunization conferred higher survival rate.