Bordetella Colonization Factor A (BcfA) elicits protective immunity againstBordetella bronchisepticain the absence of an additional adjuvant

Bordetella bronchiseptica (B. bronchiseptica)is an etiologic agent of respiratory diseases in animals and humans. Despite widespread use of veterinaryB. bronchisepticavaccines, there is limited information on their composition, relative efficacy, and the immune responses they elicit. Furthermore, humanB. bronchisepticavaccines are not available. We leveraged the dual antigenic and adjuvant functions of BcfA to develop acellularB. bronchisepticavaccines in the absence of an additional adjuvant. Balb/c mice immunized with BcfA alone or a trivalent vaccine containing BcfA and theBordetellaantigens FHA and Prn were equally protected against challenge with a prototypeB. bronchisepticastrain. The trivalent vaccine protected mice significantly better than the canine vaccine Bronchicine®and provided protection against aB. bronchisepticastrain isolated from a dog with kennel cough. Th1/17-polarized immune responses correlate with long-lasting protection againstBordetellaeand other respiratory pathogens. Notably, BcfA strongly attenuated the Th2 responses elicited by FHA/Prn, resulting in Th1/17-skewed responses in inherently Th2-skewed Balb/c mice. Thus, BcfA functions as both an antigen and an adjuvant, providing protection as a single component vaccine. BcfA-adjuvanted vaccines may improve the efficacy and durability of vaccines againstBordetellaeand other pathogens.