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bioRxiv · 10.1101/2025.01.22.634310

The hyper-attenuated RVFV 40Fp8 strain can be safely administered to pregnant ewes to protect them from a virulent challenge

Borrego, B.·Alonso, C.·Moreno, S.·Calvo-Pinilla, E.·Lorenzo, G.·Sanchez-Cordon, P. J.·Brun, A.
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Abstract

In the present study, we evaluated the immunogenicity, safety and protective efficacy of the attenuated RVFV-40Fp8 strain in natural hosts (non-pregnant ewes) and in a highly susceptible host infection model such as pregnant ewes in the first third of pregnancy. Our results confirm the immunogenicity of 40Fp8 administration in non-pregnant and pregnant ewes, as well as the absence of foetal damage even after a high-dose vaccination regime in pregnant ewes. In addition, the ewes and their foetuses were protected against a virulent RVFV-56/74 strain challenge, as shown by comparative histopathological evaluation of tissue samples from vaccinated and non-vaccinated pregnant ewes. These results confirm the potential use of 40Fp8 as a RVF live-attenuated vaccine candidate and pave the way for further clinical developments.

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Borrego, B., Alonso, C., Moreno, S., Calvo-Pinilla, E., Lorenzo, G., Sanchez-Cordon, P. J., Brun, A.. 2025-01-22. The hyper-attenuated RVFV 40Fp8 strain can be safely administered to pregnant ewes to protect them from a virulent challenge. https://doi.org/10.1101/2025.01.22.634310

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