Colonization Factor A (BcfA) Elicits Protective Immunity against Bordetella bronchiseptica in the Absence of an Additional Adjuvant.

is an etiologic agent of respiratory diseases in animals and humans. Despite the widespread use of veterinary vaccines, there is limited information on their composition and relative efficacy and on the immune responses that they elicit. Furthermore, human vaccines are not available. We leveraged the dual antigenic and adjuvant functions of colonization factor A (BcfA) to develop acellular vaccines in the absence of an additional adjuvant. BALB/c mice immunized with BcfA alone or a trivalent vaccine containing BcfA and the antigens FHA and Prn were equally protected against challenge with a prototype strain. The trivalent vaccine protected mice significantly better than the canine vaccine Bronchicine and provided protection against a strain isolated from a dog with kennel cough. Th1/17-polarized immune responses correlate with long-lasting protection against bordetellae and other respiratory pathogens. Notably, BcfA strongly attenuated the Th2 responses elicited by FHA and 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 against bordetellae and other pathogens.