Abstract
Rift Valley fever virus (RVFV) is a mosquito-borne zoonotic pathogen that causes periodic outbreaks of abortion in ruminant species and hemorrhagic disease in humans in sub-Saharan Africa. These outbreaks have a significant impact on veterinary and public health. Its introduction to the Arabian Peninsula in 2003 raised concerns of further spread of this transboundary pathogen to non-endemic areas. These concerns are supported by the presence of competent vectors in many non-endemic countries. There is no licensed RVF vaccine available for humans and only a conditionally licensed veterinary vaccine available in the United States. Currently employed modified live attenuated virus vaccines in endemic countries lack the ability for differentiating infected from vaccinated animals (DIVA). Previously, the efficacy of a recombinant subunit vaccine based on the RVFV Gn and Gc glycoproteins, derived from the 1977 human RVFV isolate ZH548, was demonstrated in sheep. In the current study, cattle were vaccinated subcutaneously with the Gn only, or Gn and Gc combined, with either one or two doses of the vaccine and then subjected to heterologous virus challenge with the virulent Kenya-128B-15 RVFV strain, isolated from Aedes mosquitoes in 2006. The elicited immune responses by some vaccine formulations (one or two vaccinations) conferred complete protection from RVF within 35 days after the first vaccination. Vaccines given 35 days prior to RVFV challenge prevented viremia, fever and RVFV-associated histopathological lesions. This study indicates that a recombinant RVFV glycoprotein-based subunit vaccine platform is able to prevent and control RVFV infections in target animals.
Highlights
The emergence or re-emergence of vector-borne diseases is of increasing global concern [1,2]
We have described the development of a recombinant Rift Valley fever virus (RVFV) Gn/Gc subunit vaccine and demonstrated its efficacy in a target animal species, sheep [21]
Niger and Uganda were free of reported human RVFV cases for many years, but the disease has re-occurred were free of reported human RVFV cases for many years, but the disease has re-occurred there in 2016 [32,33]
Summary
The emergence or re-emergence of vector-borne diseases is of increasing global concern [1,2]. Rift Valley fever (RVF) is one of these vector-borne diseases raising serious concerns for its potential introduction into Europe and the United States (US), since competent mosquito vectors exist on both continents [3,4,5]. The RVF virus (RVFV) is classified as an overlap select agent and risk group-3 pathogen by the Centers for Disease Control and Prevention (CDC) and the United States Department of Agriculture (USDA), because of its potential veterinary and public health impacts. There is a modified live attenuated RVF vaccine candidate in Phase II clinical evaluation [7,8]; neither of the human vaccines are readily available or licensed. There are veterinary RVF vaccines available for RVF endemic countries but only one veterinary vaccine is conditionally licensed in the U.S
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