Non-responsiveness to a foot-and-mouth disease virus peptide overcome by addition of foreign helper T-cell determinants

Abstract

Study of the immune response to synthetic antigens has shown that uncoupled peptides can realize their potential as vaccines only if they contain domains that react with helper T-cell receptors and Ia antigens^1,2 in addition to antibody binding sites. Here we consider whether genetically restricted non-responsiveness to an uncoupled peptide could be overcome by synthesizing a peptide with an additional helper T-cell epitope from a different protein. We demonstrate that H–2^dmice, which are non-responders to the 141–160 VP1 peptide of foot-and-mouth disease virus (FMDV), can be converted into responders by immunization with peptides containing the FMDV sequence with defined 'foreign' helper T-cell determinants from ovalbumin or sperm whale myoglobin. Furthermore, the virus-neutralizing activity of the antibody raised against peptide was dependent on the determinant used. Thus, FMDV peptides with the added sequences 323–339 from ovalbumin and 132–148 from sperm-whale myoglobin elicited a high degree of neutralizing activity in B10.D2 mice. The sera from mice which received the peptide with the added sequence 105–121 from sperm whale myoglobin did not neutralize the virus, although they had high levels of anti-141–160 FMDV peptide activity. Our data indicate that the T-cell help given by the 'foreign' epitopes is B-cell clone specific. These results are likely to have important implications for the design of peptide vaccines.