Efficacy of two Chlamydia abortus subcellular vaccines in a pregnant ewe challenge model for ovine enzootic abortion

Livingstone, Morag; Ranjan Wattegedera, Sean; Palarea-Albaladejo, Javier; Aitchison, Kevin; Corbett, Cecilia; Sait, Michelle; Wilson, Kim; Chianini, Francesca; Silvia Rocchi, Mara; Wheelhouse, Nicholas; Entrican, Gary; Longbottom, David

Abstract

Chlamydia abortus, the aetiological agent of enzootic abortion of ewes, is a major cause of reproductive loss in small ruminants worldwide, accounting for significant economic losses to the farming industry. Disease can be managed through the use of commercial inactivated or live whole organism-based vaccines, although both have limitations particularly in terms of efficacy, safety and disease-associated outbreaks. Here we report a comparison of two experimental vaccines (chlamydial outer membrane complex (COMC) and octyl glucoside (OG)-COMC) based on detergent extracted outer membrane preparations of C. abortus and delivered as prime-boost immunisations, with the commercial live vaccine Cevac® Chlamydia in a pregnant sheep challenge model. No abortions occurred in either experimental vaccine group, while a single abortion occurred in the commercial vaccine group. Bacterial shedding, as a measure of potential risk of transmission of infection to naïve animals, was lowest in the COMC vaccinated group, with reductions of 87.5%, 86.4% and 74% observed for the COMC, OG-COMC and live commercial vaccine groups, respectively, compared to the unvaccinated challenge control group. The results show that the COMC vaccine performed the best and is a safer efficacious alternative to the commercial vaccines. However, to improve commercial viability, future studies should optimise the antigen dose and number of inoculations required.

• Journal Article Type: Article
• Acceptance Date: Aug 11, 2021
• Online Publication Date: Aug 13, 2021
• Publication Date: 2021
• Deposit Date: Aug 12, 2021
• Publicly Available Date: Aug 17, 2021
• Journal: Vaccines
• Publisher: MDPI
• Peer Reviewed: Peer Reviewed
• Volume: 9
• Issue: 8
• Article Number: 898
• DOI: https://doi.org/10.3390/vaccines9080898
• Keywords: Chlamydia abortus; enzootic abortion of ewes; vaccine development; vaccine efficacy; quantitative real-time polymerase chain reaction (PCR); serological analysis; cytokine analysis
• Public URL: http://researchrepository.napier.ac.uk/Output/2793210