A Bacterially-Expressed Recombinant Envelope Protein from Usutu Virus Induces Neutralizing Antibodies in Rabbits.

Kinga Böszörményi,Gwendoline Kiemenyi Kayere,Bram Koster,Amy Van Dijke,Montserrat Barcena,Janet Hirsch,Bart Faber,Boyd Aaldijk,Nicole Heijmans,Soesjiel Dwarka,Gesine Cornellissen,Zahra Fagrouch,Ronald Limpens,Ernst Verschoor,Willy Bogers,Clemens Kocken,Roberto Rodriguez Garcia,Babs Verstrepen

doi:10.3390/vaccines9020157

Kinga Böszörményi, Gwendoline Kiemenyi Kayere + Show 16 more

Open Access

https://doi.org/10.3390/vaccines9020157

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Abstract

Background: Recently, an emerging flavivirus, Usutu virus (USUV), has caused an epidemic among birds in Europe, resulting in a massive die-off in Eurasian blackbirds. Currently found only in Europe and Africa, it can be envisioned that Usutu virus will follow the path of other flaviviruses, like West Nile virus and Zika virus, and will spread via its mosquito vectors and bird hosts to other parts of the world. Several cases of human infections by Usutu virus have already been published. Anticipating this spread, development of an efficacious vaccine would be highly desirable. Method: This study describes the production in E. coli, purification, and refolding of a partial USUV envelope protein. Prior to immunization, the protein was characterized using size exclusion chromatography, transmission electron microscopy and dynamic light scattering, showing the limited presence of virus-like structures, indicating that the protein solution is probably a mixture of mono and multimeric envelope proteins. Results: Immunizations of two rabbits with the refolded E-protein fraction, mixed with a strong adjuvant, resulted in the generation of neutralizing antibodies, as evidenced in an in vitro assay. Discussion: The way forward towards a subunit vaccine against Usutu virus infection is discussed.

Highlights

Using densitometry of the SDS-PAGE gel, it was estimated that 40% of the total bacterial protein was the USUV E expression product (Table 1), while SDS-PAGE showed that the expressed protein was close to its expected theoretical molecular mass of
A considerable number of infections in Europe first attributed to West Nile virus are, in retrospect, caused by USUV, while the intensified screening of human sera resulted in the detection of numerous new human asymptomatic USUV infections [28,32,33,34,46]
The fact that USUV follows the same route that West Nile virus (WNV) and Zika virus (ZIKV) have taken in recent history, the preparative development of a vaccine against USUV infection would be highly opportune

Summary

Introduction

Usutu virus (USUV) is a positive-stranded RNA virus belonging to the family of Flaviviridae, genus Flavivirus [1]. Since its first isolation in South Africa in 1959 from a. A widespread occurrence of USUV has been observed in several countries [2]. The first emergence of USUV in Europe was thought to be in 2001 in Austria, the virus being responsible for a high mortality among Eurasian blackbirds (Turdus merula) [3]. In a retrospective study, Weissenböck et al already confirmed the presence of the virus in Italy in 1996, where it caused a high number of deaths in wild birds [4]. USUV has spread to a large number of European countries, including

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