Recombinant adenovirus expressing pdhβ-pdhD fusion protein produces robust immune responses and partial protection against Mycoplasma Synoviae challenge in chickens

Mycoplasma synoviae (MS) stands as a pivotal pathogen, responsible for triggering arthritis and airsacculitis in both chickens and turkeys. Given the pressing need for safe and efficacious vaccine candidates, we engineered recombinant adenoviruses expressing a fusion antigen. This antigen consisted of the pyruvate dehydrogenase E1 subunit beta (pdhβ) and dihydrolipoyl dehydrogenase (pdhD) of MS. We then systematically evaluated the immune effect and protective efficacy of these recombinant adenoviruses against MS challenge in a chicken model. Our results demonstrated the successful construction of recombinant adenoviruses rAd-pdhβ, rAd-pdhD, and rAd-pdhβ-pdhD. The pdhβ, pdhD, and pdhβ-pdhD proteins were efficiently expressed in cells infected with the respective recombinant adenoviruses. Animal experiments further revealed that vaccination with recombinant adenoviruses rAd-pdhβ, rAd-pdhD, and rAd-pdhβ-pdhD elicited significant specific humoral and cellular immune responses (P < 0.05). Notably, rAd-pdhβ-pdhD exhibited superior immunogenicity compared to rAd-pdhβ and rAd-pdhD. Moreover, all three recombinant adenovirus vaccine candidates conferred partial protection to chickens against MS challenge. They effectively alleviated MS-induced footpad and joint swelling, as well as inflammation. Among them, rAd-pdhβ-pdhD demonstrated a better protective effect. In conclusion, vaccination with recombinant adenoviruses rAd-pdhβ, rAd-pdhD, and rAd-pdhβ-pdhD can evoke immune responses and provide partial protection against MS in chickens. In particular, rAd-pdhβ-pdhD holds greater potential as a vaccine candidate against MS.