Generation and immunogenicity analysis of recombinant classical swine fever virus glycoprotein E2 and Erns expressed in baculovirus expression system

Yunchao Liu,Qiang Wei,Yaning Sun,Li Wang,Ruiguang Deng,Guangxu Xing,Yilin Bai,Yapeng Song,Wei Yu,Gaiping Zhang

doi:10.1186/s12985-021-01507-1

Abstract

Classical swine fever (CSF) caused by the classical swine fever virus (CSFV) is a highly contagious swine disease resulting in large economical losses worldwide. The viral envelope glycoprotein E2 and Erns are major targets for eliciting antibodies against CSFV in infected animals. In this report, the glycoprotein E2 and Erns were expressed using the baculovirus system and their protective immunity in rabbits were tested. Twenty CSFV seronegative rabbits were randomly divided into five groups. Each rabbit was intramuscularly immunized with CSFV-E2, CSFV-Erns, or their combination (CSFV-E2 + Erns). Besides, a commercial CSFV vaccine (C-strain) and PBS were used as positive or negative controls, respectively. Four weeks after the second immunization, all the rabbits were challenged with 100 RID50 of CSFV C-strain. High levels of CSFV E2-specific antibody, neutralizing antibody and cellular immune responses to CSFV were elicited in the rabbits inoculated with C-strain, CSFV-E2, and CSFV-E2 + Erns. And the rabbits inoculated with the three vaccines received complete protection against CSFV C-strain. However, no neutralizing antibody was detected in the Erns vaccinated rabbits and the rabbits exhibited fever typical of CSFV, suggesting the Erns alone is not able to induce a protective immune response. Taken together, while the Erns could not confer protection against CSFV, E2 and E2 + Erns could not only elicit humoral and cell-mediated immune responses but also confer complete protection against CSFV C-strain in rabbits.

Highlights

Classical swine fever (CSF) is a highly contagious and economically important viral disease of swine, that is notifiable to the World Organization for Animal Health [1]
Except for the PBS group, elicited higher IFN-γ mRNA expression than IL-4 mRNA expression (Fig. 3b, c). These results indicated that the C strain, classical swine fever virus (CSFV)-E2, CSFV-Erns, and CSFV-E2 + Erns vaccines induced Th1dominant cellular immune responses in vivo
In this study, CSFV E2 and Erns protein were successfully generated by insect cell/baculovirus expression system and the immunogenicity of the proteins was evaluated

Summary

Introduction

Classical swine fever (CSF) is a highly contagious and economically important viral disease of swine, that is notifiable to the World Organization for Animal Health [1]. The causative agent, classical swine fever virus (CSFV) is a member of the genus Pestivirus within the. There are three envelope glycoproteins in the CSFV virion, Erns, E1, and E2. Erns is loosely associated with mature virions [3] and possesses ribonuclease activity. E2 is a major determinant of CSFV virulence and is involved in virus attachment and entry into target cells [8, 9]. It is shown that glycosylation plays a major role in the immunogenicity of CSFV envelope proteins [7]. Previous studies demonstrate that both E2 and E rns are capable of inducing the production of neutralizing antibodies in the host [10,11,12]

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Discussion

Conclusion