Rift Valley fever vaccine found to be safe in pregnant animals

Researchers have shown that a simian adenovirus vectored vaccine, ChAdOx1 RVF, is effective at protecting pregnant sheep and goats from Rift Valley fever (RVF). They report their findings in npj Vaccines.

Infection of livestock with Rift Valley fever virus (RVFV) results in high mortality and poor outcomes during pregnancy, including stillbirths, fetal malformations and abortions. It also poses a severe threat to human health but there is currently no licenced human vaccine available. People can contract the disease through contact with contaminated tissues and fluids of livestock, as well as being bitten by infected mosquitoes.

ChAdOx1 RVF was developed by The Jenner Institute at the University of Oxford and was previously shown to be safe and effective at protecting animals. The vaccine has since been scheduled for human trials, but its effects on pregnant animals still required examination. Scientists at The Pirbright Institute worked with The Jenner Institute, Wageningen University Research, BioVacc Consulting Ltd and the KEMRI-Wellcome Trust Research Programme to demonstrate the vaccine’s safety in pregnant goats and sheep at the Institute’s specialist high containment facilities.

The study has shown that animals immunised with a single dose of ChAdOx1 RVF remain healthy and suffer no pregnancy losses after challenge with a virulent strain of RVF virus. The protection was more robust in sheep than goats, despite the similar levels of immune response induced, which suggests that protection mechanisms against RVF could differ between livestock species.

The research demonstrates that ChAdOx1 RVF overcomes drawbacks that current veterinary RVF vaccines experience, such as causing pregnancy complications or requiring multiple booster vaccinations. ChAdOx1 RVF also generates a rapid immune response and allows diagnostic tests to differentiate between infected and vaccinated animals (DIVA). These properties make this vaccine well suited for tackling outbreak situations and could limit the circulation of RVF amongst animals and people.

“This research will aid the development of ChAdOx1 RVF for human use, and for the first time we may see a vaccine that can be deployed against the same virus in both animals and humans”, said Professor Bryan Charleston, Director of The Pirbright Institute.

Article: Stedman, A., Wright, D., Wichgers Schreur, P. J., Clark, M. H. A., Hill, A. V. S., Gilbert, S. C., Francis, M. J., van Keulen, L., Kortekaas, J., Charleston, B., Warimwe, G. M. (2019). Safety and efficacy of ChAdOx1 RVF vaccine against Rift Valley fever in pregnant sheep and goats. npj Vaccines, vol. 4, Article number: 44, doi: 10.1038/s41541-019-0138-0

[SOURCE: The Pirbright Institute]