Differentiation of Antibodies against Selected Simbu Serogroup Viruses by a Glycoprotein Gc-Based Triplex ELISA.

Kerstin Wernike,Andrea Aebischer,Martin Beer,Franziska Sick,Kevin P Szillat

doi:10.3390/vetsci8010012

Abstract

The Simbu serogroup of orthobunyaviruses includes several pathogens of veterinary importance, among them Schmallenberg virus (SBV), Akabane virus (AKAV) and Shuni virus (SHUV). They infect predominantly ruminants and induce severe congenital malformation. In adult animals, the intra vitam diagnostics by direct virus detection is limited to only a few days due to a short-lived viremia. For surveillance purposes the testing for specific antibodies is a superior approach. However, the serological differentiation is hampered by a considerable extent of cross-reactivity, as viruses were assigned into this serogroup based on antigenic relatedness. Here, we established a glycoprotein Gc-based triplex enzyme-linked immunosorbent assay (ELISA) for the detection and differentiation of antibodies against SBV, AKAV, and SHUV. A total of 477 negative samples of various ruminant species, 238 samples positive for SBV-antibodies, 36 positive for AKAV-antibodies and 53 SHUV antibody-positive samples were tested in comparison to neutralization tests. For the newly developed ELISA, overall diagnostic specificities of 84.56%, 94.68% and 89.39% and sensitivities of 89.08%, 69.44% and 84.91% were calculated for SBV, AKAV and SHUV, respectively, with only slight effects of serological cross-reactivity on the diagnostic specificity. Thus, this test system could be used for serological screening in suspected populations or as additional tool during outbreak investigations.

Highlights

Viruses of the Simbu serogroup, which belongs to the family Peribunyaviridae, genusOrthobunyavirus, are distributed worldwide and include several pathogens of veterinary importance [1,2], e.g., members of the virus species Akabane orthobunyavirus, Schmallenberg orthobunyavirus or Shuni orthobunyavirus [3]
Sci. 2021, 8, 12 originated from cattle and sheep experimentally infected with Schmallenberg virus (SBV) [51,52], cattle infected with Shuni virus (SHUV) [25] or cattle vaccinated against Akabane virus (AKAV), the Simbu serogroup member Aino virus (AINOV) and the likewise teratogenic Chuzan virus [53]
It has been shown before, that the orthobunyavirus Gc head domain represents the major target of neutralizing antibodies produced upon virus infection [11], and the recombinant SBV, AKAV and SHUV enzyme-linked immunosorbent assay (ELISA) antigens were designed and produced based

Summary

Introduction

Viruses of the Simbu serogroup, which belongs to the family Peribunyaviridae, genusOrthobunyavirus, are distributed worldwide and include several pathogens of veterinary importance [1,2], e.g., members of the virus species Akabane orthobunyavirus, Schmallenberg orthobunyavirus or Shuni orthobunyavirus [3]. Viruses of the Simbu serogroup, which belongs to the family Peribunyaviridae, genus. Viruses were assigned into this serogroup solely based on antigenic relation determined by plaque reduction neutralization, hemagglutination inhibition, complement fixation or radial immunodiffusion tests [4,5]. The genome of simbuviruses consists of three segments of single-stranded RNA, of which the small (S) genomic segment, that encodes for the nucleocapsid protein N and the non-structural protein NSs, is the most conserved one. The large (L) segment encodes for the RNA-dependent RNA polymerase and the medium (M) segment for the glycoproteins Gn and Gc and the non-structural protein NSm [6,7]. The N-terminal variable part of the Gc-protein (Gc head (GcH)) is highly immunogenic and the major target of neutralizing antibodies [11,12]

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Discussion

Conclusion