This is an optimal nine-amino-acid 127 to 135 peptide respiratory syncytial virus (RSV)-specific, the H-2Kd-restricted subdominant epitope in the M2 protein, which contains an H-2Kd consensus sequence with Y at position 2 and I at position 9. The M2 gene is unique to the genus Pneumovirus. It has two overlapping open reading frames, M2-1 and M2-2, both involved in the viral RNA synthesis process.