Antibodies against outer-capsid proteins of grass carp reovirus expressed in E. coli are capable of neutralizing viral infectivity

Ling Shao,Qin Fang,Xiaoyun Sun

doi:10.1186/1743-422x-8-347

Ling Shao, Qin Fang + Show 1 more

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https://doi.org/10.1186/1743-422x-8-347

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Abstract

BackgroundGrass carp reovirus (GCRV), which causes severe infectious outbreaks of hemorrhagic disease in aquatic animals, is a highly pathogenic agent in the Aquareovirus genus of family Reoviridae. The outer capsid shell of GCRV, composed of the VP5-VP7 protein complex, is believed to be involved in cell entry. The objective of this study was to produce a major neutralization antibody for mitigating GCRV infection.ResultsRecombinant plasmids of GCRV outer capsid proteins VP5 and VP7 were constructed and expressed in prokaryotic cells in our previous work. In this study, we prepared GCRV Antibody (Ab), VP5Ab and VP7Ab generated from purified native GCRV, recombinant VP5 and VP7 respectively. Immunoblotting analysis showed that the prepared antibodies were specific to its antigens. In addition, combined plaque and cytopathic effect (CPE)-based TCID50 (50% tissue culture infective dose) assays showed that both VP5Ab and VP7Ab were capable of neutralizing viral infectivity. Particularly, the neutralizing activity of VP7Ab was 3 times higher than that of VP5Ab, suggesting that VP7 might be a dominating epitope. Moreover, the combination of VP5Ab and VP7Ab appeared to enhance GCRV neutralizing capacity.ConclusionsThe results presented in this study indicated that VP7 protein was the major epitope of GCRV. Furthermore, VP5Ab and VP7Ab in combination presented an enhanced capacity to neutralize the GCRV particle, suggesting that the VP5 and VP7 proteins may cooperate with each other during virus cell entry. The data can be used not only to further define the surface epitope domain of GCRV but may also be applicable in the designing of vaccines.

Highlights

Grass carp reovirus (GCRV), which causes severe infectious outbreaks of hemorrhagic disease in aquatic animals, is a highly pathogenic agent in the Aquareovirus genus of family Reoviridae
Grass carp reovirus (GCRV), a member of genus Aquareovirus in the family Reoviridae[1], was the first viral pathogen to be identified from aquatic animals in China; this virus was identified twenty years ago during an acute epidemic characterized by symptoms of hemorrhagic disease in fingerling and yearling grass carp [2,3]
The 11-part segmented genome of GCRV is similar in composition to members of the genus Rotavirus within the family Reoviridae, there is no genetic relationship with rotavirus based on reciprocal RNARNA dot blot hybridization [9,10]

Summary

Introduction

Grass carp reovirus (GCRV), which causes severe infectious outbreaks of hemorrhagic disease in aquatic animals, is a highly pathogenic agent in the Aquareovirus genus of family Reoviridae. Recent cryo-electron microscopy (cryo-EM) and three-dimensional (3D) structural reconstruction images indicate that the inner layer arranges with a T = 1 symmetry This layer is composed of 5 proteins (including VP1-VP4 and VP6) and possesses the enzymatic activities necessary for viral transcription [6,7,13,14]. The other outer capsid proteins, arranged on an incomplete T = 13 icosahedral lattice, are composed of VP5 and VP7; each GCRV virion contains 200 trimers formed by VP5-VP7 heterodimers, a structure homologous to the μ13s33 complex of MRV (Mammalian reovirus)[13,15]. Recent progress on the GCRV infectious subviral particle 3.3 Å atom structure revealed a priming mechanism of dsRNA virus entry into cells [17]

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