Abstract
Rift Valley fever virus (RVFV) is a mosquito-borne zoonotic pathogen causing disease outbreaks in Africa and the Arabian Peninsula. The virus has great potential for transboundary spread due to the presence of competent vectors in non-endemic areas. There is currently no fully licensed vaccine suitable for use in livestock or humans outside endemic areas. Here we report the evaluation of the efficacy of a recombinant subunit vaccine based on the RVFV Gn and Gc glycoproteins. In a previous study, the vaccine elicited strong virus neutralizing antibody responses in sheep and was DIVA (differentiating naturally infected from vaccinated animals) compatible. In the current efficacy study, a group of sheep (n = 5) was vaccinated subcutaneously with the glycoprotein-based subunit vaccine candidate and then subjected to heterologous challenge with the virulent Kenya-128B-15 RVFV strain. The vaccine elicited high virus neutralizing antibody titers and conferred complete protection in all vaccinated sheep, as evidenced by prevention of viremia, fever and absence of RVFV-associated histopathological lesions. We conclude that the subunit vaccine platform represents a promising strategy for the prevention and control of RVFV infections in susceptible hosts.
Highlights
The presence of competent vectors in non-endemic areas presents significant risk of introduction and further spread of RVFV3–5
The occurrence of Rift Valley fever virus (RVFV) outbreaks outside the African continent in 2000 in the Arabian Peninsula demonstrated the potential for the virus to spread to non-endemic areas
We developed and evaluated the efficacy of a recombinant subunit vaccine candidate composed of RVFV surface glycoproteins, Gn and Gc, adjuvanted with montanide ISA25 VG, in a ruminant model
Summary
The presence of competent vectors in non-endemic areas presents significant risk of introduction and further spread of RVFV3–5. A natural attenuated isolate, Clone 13, from a benign RVF case in the Central African Republic[11], and a chemically attenuated virus, MP12, derived from ZH548, an Egyptian wild-type isolate[12], have been evaluated for efficacy[13,14,15] These attenuated vaccines have shown promising results[16], safety issues associated with their use in non-endemic regions remain a major concern[17]. Another drawback of the live-attenuated RVFV vaccines is that they do not allow for differentiation of www.nature.com/scientificreports/. The current work is a logical continuation of this work aimed at evaluating the efficacy of the recombinant Gn/Gc subunit vaccine candidate to protect against heterologous virus challenge in sheep
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