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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


Morag Livingstone

Sean Ranjan Wattegedera

Javier Palarea-Albaladejo

Kevin Aitchison

Cecilia Corbett

Michelle Sait

Kim Wilson

Francesca Chianini

Mara Silvia Rocchi

Gary Entrican

David Longbottom


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
Keywords Chlamydia abortus; enzootic abortion of ewes; vaccine development; vaccine efficacy; quantitative real-time polymerase chain reaction (PCR); serological analysis; cytokine analysis
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Efficacy Of Two Chlamydia Abortus Subcellular Vaccines In A Pregnant Ewe Challenge Model For Ovine Enzootic Abortion (1.2 Mb)

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Copyright Statement
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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