Comparative Efficacy of Chimeric Porcine Circovirus (PCV) Vaccines against Experimental Heterologous PCV2d Challenges

Pichanun Wongchanapai; Panuwat Yamsakul; Jirapat Arunorat; Thunyamas Guntawang; Tidaratt Sittisak; Saralee Srivorakul; Kornravee Photichai; Roongroje Thanawongnuwech; Manakorn Sukmak; Kidsadagon Pringproa

doi:10.3390/vetsci10020080

Comparative Efficacy of Chimeric Porcine Circovirus (PCV) Vaccines against Experimental Heterologous PCV2d Challenges

Vet Sci. 2023 Jan 21;10(2):80. doi: 10.3390/vetsci10020080.

Affiliations

¹ Department of Veterinary Biosciences and Veterinary Public Health, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand.
² Swine Business Unit, Zoetis (Thailand) Limited, Bangkok 10500, Thailand.
³ Department of Food Animal Clinic, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand.
⁴ Center of Veterinary Diagnosis and Technology Transfer, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand.
⁵ Department of Pathology, Faculty of Veterinary Sciences, Chulalongkorn University, Bangkok 10330, Thailand.
⁶ Department of Farm Resources and Production Medicine, Faculty of Veterinary Medicine, Kasetsart University, Nakorn Pathom 73140, Thailand.
⁷ Center of Excellence in Elephant and Wildlife Research, Chiang Mai University, Chiang Mai 50100, Thailand.

Abstract

The objective of this study was to evaluate the efficacy of two multivalent commercial porcine circovirus (PCV) vaccines against heterologous PCV2d challenges. A total of 24 crossbred male pigs aged 26 days selected from a specific pathogen-free herd were randomly divided into four groups (six pigs per group) and assigned as follows: negative control (unvaccinated/sham-challenge), vaccinated with chimeric PCV1-2a vaccine (PCV1-2a/PCV2d-challenge), vaccinated with chimeric PCV1-2a-2b vaccine (PCV1-2a-2b/PCV2d-challenge) and positive control (unvaccinated/PCV2d-challenge). At 21 days after vaccination, the pigs were intranasally and intramuscularly inoculated with either sham or field isolates of PCV2d (PCV2d/149/TH/2020). After being challenged, blood samples were obtained weekly and analyzed for levels of PCV2d viremia, neutralizing antibodies, and IgG against PCV2. At 30 days post-challenge (DPC), the pigs were euthanized and then subjected to pathological evaluations and molecular analysis. The results indicated that pigs in the PCV1-2a-2b/PCV2d-challenge and the PCV1-2a/PCV2d-challenge groups possessed significantly greater levels of PCV2d-neutralizing antibody titer when compared with the positive control group. Moreover, pigs in the PCV1-2a-2b/PCV2d-challenge group exhibited a lower degree of severity in terms of gross lesion scores and lower levels of PCV2 viremia when compared with the positive control group. This study demonstrated that vaccinating pigs with either the PCV1-2a or PCV1-2a-2b chimeric vaccines elicits a potent immune response against PCV2d infection and reduces viremia after PCV2d inoculation in pigs.

Keywords: Porcine circovirus type 2; challenge; chimeric vaccine; heterologous PCV2.

Grants and funding

This project was partially supported by the Center of Excellence in Elephant and Wildlife Research, the Laboratory Animal Center, Chiang Mai University, Thailand, the National Research Council of Thailand (NRCT): R. Thanawongnuwech NRCT Senior scholar 2022#N42650553 and Zoetis (Thailand) Limited.