Identification of a Conserved B-cell Epitope on Reticuloendotheliosis Virus Envelope Protein by Screening a Phage-displayed Random Peptide Library

Mei Xue,Hongbo Gao,Xingming Shi,Xianlan Cui,Yan Zhao,Shunlei Hu,Yun-Feng Wang,Jing Zhang,Hongyu Cui,Qianjun Li

doi:10.1371/journal.pone.0049842

Abstract

BackgroundThe gp90 protein of avian reticuloendotheliosis-associated virus (REV-A) is an important envelope glycoprotein, which is responsible for inducing protective antibody immune responses in animals. B-cell epitopes on the gp90 protein of REV have not been well studied and reported.Methods and ResultsThis study describes the identification of a linear B-cell epitope on the gp90 protein by screening a phage-displayed 12-mer random peptide library with the neutralizing monoclonal antibody (mAb) A9E8 directed against the gp90. The mAb A9E8 recognized phages displaying peptides with the consensus motif SVQYHPL. Amino acid sequence of the motif exactly matched 213SVQYHPL219 of the gp90. Further identification of the displayed B cell epitope was conducted using a set of truncated peptides expressed as GST fusion proteins and the Western blot results indicated that 213SVQYHPL219 was the minimal determinant of the linear B cell epitope recognized by the mAb A9E8. Moreover, an eight amino acid peptide SVQYHPLA was proven to be the minimal unit of the epitope with the maximal binding activity to mAb A9E8. The REV-A-positive chicken serum reacted with the minimal linear epitopes in Western blot, revealing the importance of the eight amino acids of the epitope in antibody-epitope binding activity. Furthermore, we found that the epitope is a common motif shared among REV-A and other members of REV group.Conclusions and SignificanceWe identified 213SVQYHPL219 as a gp90-specific linear B-cell epitope recognized by the neutralizing mAb A9E8. The results in this study may have potential applications in development of diagnostic techniques and epitope-based marker vaccines against REV-A and other viruses of the REV group.

Highlights

Reticuloendotheliosis viruses (REVs) are a group of viruses in the family Retroviridae, gammaretroviruses in the same genus as mammalian C-type retroviruses [1]
We identified 213SVQYHPL219 as a gp90-specific linear B-cell epitope recognized by the neutralizing monoclonal antibody (mAb) A9E8
One monoclonal antibody produced by the line designated as A9E8 was selected for strong reactivity with recombinant gp90 protein in Western blot (Figure 1A) and in an indirect enzyme-linked immunosorbent assay (ELISA)

Summary

Introduction

Reticuloendotheliosis viruses (REVs) are a group of viruses in the family Retroviridae, gammaretroviruses in the same genus as mammalian C-type retroviruses [1]. The major mature env gene products of REVs are the surface glycoprotein (gp90) and the transmembrane protein (gp20) [11,12]. Previous studies indicated that the Cterminal epitope of gp was exposed on the outer surface of the REV-A-infected cell [12]. The epitope identified in REV gp protein has not been finely mapped, and the core sequence of the epitope needs to be determined. The gp protein of avian reticuloendotheliosis-associated virus (REV-A) is an important envelope glycoprotein, which is responsible for inducing protective antibody immune responses in animals. B-cell epitopes on the gp protein of REV have not been well studied and reported

Methods

Results

Discussion

Conclusion