The peptide was also recognized by REV-A-positive chicken serum, revealing the importance of the eight amino acids of the epitope in antibody-epitope binding reactivity. Sequence alignments of REV-A strains, REV-T strain and five other REV strains demonstrated that the motif was highly conserved among REV viruses, indicating that it is a broad group-specific epitope. Since A9E8 was identified as a neutralizing mAb, the epitope identified with A9E8 in this study was a neutralizing epitope.