Identification, synthesis and properties of a consensus peptide recognized by a monoclonal antibody directed to various type I cytokine receptors

Biopanning of polypeptides binding to bovine ephemeral fever virus G1 protein from phage display peptide library

Background

The bovine ephemeral fever virus (BEFV) glycoprotein neutralization site 1 (also referred as G₁ protein), is a critical protein responsible for virus infectivity and eliciting immune-protection, however, binding peptides of BEFV G₁ protein are still unclear. Thus, the aim of the present study was to screen specific polypeptides, which bind BEFV G₁ protein with high-affinity and inhibit BEFV replication.

Methods

The purified BEFV G₁ was coated and then reacted with the M13-based Ph.D.-7 phage random display library. The peptides for target binding were automated sequenced after four rounds of enrichment biopanning. The amino acid sequences of polypeptide displayed on positive clones were deduced and the affinity of positive polypeptides with BEFV G₁ was assayed by ELISA. Then the roles of specific G₁-binding peptides in the context of BEFV infection were analyzed.

Results

The results showed that 27 specific peptide ligands displaying 11 different amino acid sequences were obtained, and the T18 and T25 clone had a higher affinity to G₁ protein than the other clones. Then their antiviral roles of two phage clones (T25 and T18) showed that both phage polypeptide T25 and T18 exerted inhibition on BEFV replication compared to control group. Moreover, synthetic peptide based on T18 (HSIRYDF) and T25 (YSLRSDY) alone or combined use on BEFV replication showed that the synthetic peptides could effectively inhibit the formation of cytopathic plaque and significantly inhibit BEFV RNA replication in a dose-dependent manner.

Conclusion

Two antiviral peptide ligands binding to bovine ephemeral fever virus G₁ protein from phage display peptide library were identified, which may provide a potential research tool for diagnostic reagents and novel antiviral agents.

Electronic supplementary material

The online version of this article (10.1186/s12917-017-1315-x) contains supplementary material, which is available to authorized users.

Properties of antibodies to a synthetic peptide representing an epitope shared by receptors of the type I cytokine family

Previous works from our laboratory demonstrated that the monoclonal antibody (MAb) called R7B4 is directed to an epitope shared by various receptors corresponding to the type I cytokine receptor family, containing the common motif WSXWS or the homologous F(Y)GEFS. Later a consensus peptide significantly recognized by the MAb was identified and synthesized (sequence HGYWSEWSPE). In the present work, an homologous of the consensus sequence (HHGYWSEWSPE) was conjugated to PADRE adjuvant to produce Ab that could simulate theMAb activity, that is, acting as hormone and/or cytokine antagonists. The covalently conjugated peptide-PADRE was a better immunogen than the consensus peptide alone according to the reactivity of sera from C57BL/6 immunized mice and, besides, no Ab to PADRE were detected. Furthermore, Ab to consensus peptide elicited after peptide-PADRE inoculation into mice behaved as immunomodulatory agents, since they improved the humoral response to a foreign antigen (in this case ovalbumin). In addition, the Ab inhibited the in vitro proliferation of various cell lines, mainly cells derived from human and mouse breast cancer. Thus, immunization with the conjugate peptide-PADRE prepared under the experimental conditions described herein originated immunomodulatory Ab that, in the future, could be tested in some pathological conditions.