Prevention of nosocomial Acinetobacter baumannii infections with a conserved immunogenic fimbrial protein

Acinetobacter baumannii, one of the most life-threatening nosocomial drug-resistant pathogens, imposes high morbidity and mortality rates, thus highlighting immunization-based treatments or prevention measures. The selection of appropriate antigens can elicit protective immunity. The gene encoding a fimbrial protein introduced via reverse vaccinology was cloned, expressed and evaluated for immunogenicity in a murine model. Mice immunized with the recombinant protein were challenged with A. baumannii ATCC 19606. Adherence to A549 cell line of specific anti-sera treated A. baumannii was also assessed. Passive immunity was evaluated in a murine pneumonia model. Indirect ELISA showed a high specific antibody titre. Adherence of A. baumannii to A549 cell line decreased by 40% after incubation with 1:250 dilution of specific anti-sera. All the actively immunized mice survived. Bacterial load in the spleen and liver of the immunized mice was 3-fold lower than those of the control. The number of bacteria in the lungs of passively immunized mice was about 6-fold lower than the control mice. The fimbrial protein could be considered as a promising protective immunogen against A. baumannii.