Phage display identifies two Caprine Arthritis Encephalitis Virus env epitopes

Abstract

Using phage display and IgG of a goat infected with Caprine Arthritis Encephalitis Virus (CAEV) we obtained families of 7 mer constrained peptides with consensus motifs LxSDPF/Y and SWN/KHWSY and mapped the epitopes mimicked by them at the Env 6-LISDPY-11 and 67-WNTYHW-72 sites of the mature gp135 amino acid sequence. The first epitope fell into the N-terminal immunogenic aa1-EDYTLISDPYGFS- aa14 site identified previously with a synthetic peptide approach; the second epitope has not been described previously. The first epitope is mostly conserved across CAEV isolates whereas the second newly described epitope is extremely conserved in Small Ruminant Lentiviruses env sequences. As being immunodominant, the epitopes are candidate targets for mimotope-mediated diagnosis and/or neutralization.

Figure 1

Sequences of peptides retrieved by infected goat IgG from the 12 mer linear (A) and 7 mer constrained (B) random peptide libraries. B1 - non-homologous peptides, B2 - homologous motif group 1 peptides, B3 - homologous motif group 2 peptides. Consensus sequences are shown in bottom of both groups. EP 1 and EP2 - CAEV Env sequences matching the motif sequences and considered the identified epitope sites (the SU mature protein amino acids numbering). Note: the clone 20 peptide shown in Figure 2 was not sequenced.

Figure 2

Reactivity of the goat IgG with clones selected from the 12 mer linear (A) and the 7 mer constrained (B) libraries. The shaded bars: PBS was added instead of the phage. Motif groups are shown.

Figure 3

Localization of epitopes on the CAEV Env N-terminal part of the mature protein.