Immunoprotectivity of an antigenic construct derived from Omp۳۴ against A. baumannii in murine pneumonia model

BACKGROUND AND ABJECTIVEAcinetobacter baumannii has emerged as one of major nosocomial pathogen that can cause various hospital infections, including pneumonia, sepsis, meningitis, post-traumatic infections and urinary tract infections. Its infections due to global emergence of multidrug-resistant even colistin strains has become a challenge for developing effective treatment options that putting the world on the brink of a post-antibiotic era. This problem leads researchers to the development of prophylactic vaccination to prevent this pathogen infections. Nasal vaccination could provide a strong mucosal and systemic immunity to combat these infections. Therefore, it is considered a promising strategy for the prevention of diseases, especially infectious diseases of the respiratory system. The development of nasal vaccines, particularly the strategies of adjuvant and antigens design and optimization enabling rapid induction of protective mucosal and systemic responses against the disease. In this context, chitosan is recognized as an established mucosal adjuvant/delivery system that has been extensively studied owing to its low toxicity, adhesion, pro-permeability, immunostimulant, ability to be absorbed in human tissues, and excellent histocompatibility with human tissues and organs. Therefore, multivalent vaccines containing different antigens are suitable candidates for providing admissible protection, and this study is focused on an outer membrane protein, Omp۳۴ and a structure derived from it, L۳X۵ as a multivalent vaccine.MATERIALS AND METHODSImmunogenic peptide Omp۳۴L۳X۵ was transferred to the E. coli BL۲۱ expression host and with recombinant protein Omp۳۴ were expressed, purified, and nasally administrated into BALB/c mice individually and in combination with chitosan. Active immunization was carried out. The mice were then challenged with a clinical isolate of A. baumannii. Then, the level of antibody in mice was measured by Indirect ELISA. The protective effect of the antibody produced against the mentioned antigens was evaluated by determining the load of bacteria in the lungs, spleen, and liver organs, as well as the animal's survival.RESULTS AND DISCUSSIONELISA analysis revealed increased antibody production in all immunized groups. However, the combined administration of the proteins with chitosan provided superior protection compared to administering each antigen individually.CONCLUSIONPolyvalent vaccines containing several antigens provide acceptable protection with the use of appropriate adjuvants.

Keywords:

Acinetobacter baumannii. , Omp۳۴. , L۳X۵. , Chitosan. , Vaccine. , Immunogenicity