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Research Project: Rift Valley Fever Pathogenesis, Epidemiology, and Control Measures

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Title: Immunogenicity and efficacy of Schmallenberg virus envelope glycoprotein subunit vaccines

item ENDALEW, ABAINEH - Kansas State University
item FABURAY, BONTO - Kansas State University
item TRUJILLO, JESSIE - Kansas State University
item GAUDREAULT, NATASHA - Kansas State University
item DAVIS, ANNE SALLY - Kansas State University
item SHIVANNA, VINJAY - Kansas State University
item SUNWOO, SUN-YOUNG - Kansas State University
item MA, WENJUN - Kansas State University
item Drolet, Barbara
item McVey, David
item MOROZOV, IGOR - Kansas State University
item Wilson, William
item RICHT, JUERGEN - Kansas State University

Submitted to: Journal of Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/10/2019
Publication Date: 10/8/2019
Citation: Endalew, A., Faburay, B., Trujillo, J.D., Gaudreault, N.N., Davis, A., Shivanna, V., Sunwoo, S., Ma, W., Drolet, B.S., McVey, D.S., Morozov, I., Wilson, W.C., Richt, J. 2019. Immunogenicity and efficacy of Schmallenberg virus envelope glycoprotein subunit vaccines. Journal of Veterinary Science. 20(6):e58.

Interpretive Summary: Schmallenberg virus (SBV) is an Orthobunyavirus of the Simbu serogroup that causes abortions, stillbirths and congenital defects in naïve pregnant sheep and cattle. Inactivated or live attenuated vaccines have been developed in endemic countries. There is interest in development of SBV vaccines that would allow differentiation of infected from vaccinated animals (DIVA strategy). Development of subunit candidate vaccines has been reported recently. The objective of this study was to develop novel DIVA-compatible SBV vaccines using viral glycoproteins expressed in baculovirus and evaluate their immunogenicity and efficacy in cattle. Two separate trials in six-month old dairy cattle were conducted using two different formulations. Neither of the SBV candidate vaccines prevented viremia nor conferred protection against SBV infection. Hence, future studies should focus on better understanding the role of different SBV proteins in inducing sustainable, protective immunity against SBV infection in ruminants.

Technical Abstract: Schmallenberg virus (SBV) is an orthobunyavirus in the Simbu serogroup that emerged in Germany in late 2011 and was mostly associated with a mild transient disease of sheep and cattle. SBV is transmitted by biting midges (Culicoides species) and causes abortions, stillbirths, and congenital defects in nai¨ve pregnant ruminants. Two separate studies were conducted with a primary objective of better understanding the virological and serological responses of sheep and cattle to different SBV isolates after experimental infection. The second objective was to produce immunoreagents and challenge materials for use in future vaccine and diagnostics research. These studies were carried out using the following infectious inocula: (i) infectious serum (IS) (ii) cell culture-grown virus, and (iii) infectious lamb brain homogenate. The responses were assessed in both species throughout the course of the experiment. SBV RNA in serum (RNAemia) was detected as early as 2 (in sheep) and 3 (in cattle) days postinfection (dpi) and peaked on 3 and 4 dpi in cattle and sheep, respectively. Cattle had higher levels of RNAemia compared with sheep. Experimental infection with IS resulted in the highest level of RNAemia in both species followed by cell culture-grown virus. A delayed, low level RNAemia was detected in cattle inoculated with infectious sheep brain. Isolation of SBV was only possible from 4 dpi sera from all cattle inoculated with IS and one sheep inoculated with cell culture-derived virus. SBV neutralizing antibodies were first detected on 14 dpi in both species. No specific gross and microscopic lesions were observed in either study. In conclusion, these studies highlight not only the difference in viremia and anti-SBV antibody level against the different SBV isolates, but also the extent of the response in the two host species.