Date of Award
Master of Science
Veterinary Microbiology and Preventive Medicine
Campylobacter jejuni clone SA has recently emerged as the prevalent cause of Campylobacter-associated sheep abortion in the United States. To develop effective vaccines against C. jejuni clone SA in sheep, it is necessary to identify the antigens that elicit protective immune responses. Recently, by using immunoproteomic approaches we successfully identified a number of clone SA proteins that were consistently immunoreactive with multiple convalescent sheep and guinea pig sera. In this study, as a first step towards developing an efficacious subunit vaccine against sheep abortion, we began to further characterize these proteins. Accordingly, 7 clone SA proteins were selected, which included HtrA, CgpA, CJSA_0852, Peb4, FabG, MetK and FlgL. Recombinant proteins for each of these antigens were produced in an E. coli expression system, and their reactivity with a panel of convalescent sera obtained from C. jejuni-infected ewes and guinea pigs were tested using immunoblotting. The results showed that CgpA, MetK, FabG had the strongest antigenicity, while HtrA, FlgL and Peb4 were less antigenic, and CJSA_0852 had little reactivity with the sera tested. CgpA, HtrA and FlgL were chosen to further evaluate the induction of protective immunity against bacterial challenge in the mouse model of systemic infection and bacteremia. Immunization of mice with recombinant CgpA, HtrA and FlgL induced high level of specific antibodies, but only CgpA-immunized mice showed a significant decrease in the level of bacteremia compared with the control mice. Analysis of different cellular fractions demonstrated that CgpA is a periplasmic protein. These results indicate that CgpA may be a potential subunit vaccine candidate against sheep abortion caused by C. jejuni.
Wang, Fei, "Immunogenic and protective properties of recombinant proteins from a highly pathogenic Campylobacter jejuni clone associated with sheep abortion" (2014). Graduate Theses and Dissertations. 13791.