Amino acid sequences 200-225 and 255-278 of the F protein of human respiratory syncytial virus (HRSV) are T cell epitopes (Bourgeois et al., 1991; Corvaisier et al, 1993). Peptides corresponding to these two regions were synthesized and coupled with keyhole limpet haemocyanin (KLH). The two conjugated proteins were administered intranasally to BALB/c mice alone or together with cholera toxin B (CTB). ELISAs revealed that the mixture of the conjugates with CTB increased not only the systemic response but also the mucosal immune response of the saliva. The systemic response was lower and the mucosal immune response was undetectable in mice immunized with the conjugates on their own. These results suggest that these two peptide sequences are effective epitopes for inducing systemic and mucosal immune responses in conjunction with CTB, and may provide the basis for a nasal peptide vaccine against RSV for human use. [2]