Immunogenicity of dinitrocarboxyphenylated melittin: the influence of C-terminal chain shortening, N-terminal substitution and prolin insertion at positions 5 and 10.

Peptides derived from the bee-venom melittin were fitted with the haptenic group dinitrocarboxyphenyl (Dncp) and tested in out-bred guinea pigs for immunogenicity by measuring the IgG anti-Dncp antibody response by ELISA. Dncp-conjugates comprising virtually the entire melittin proved to be strong immunogens producing antibody responses comparable to those of proteins. Weak responses were obtained with considerably shortened sequences. Conjugates with N-terminal Dncp gave markedly reduced antibody responses compared to peptides with C-terminal Dncp. An N-terminal biotinyl substituent abolished the immune response whereas N-terminal lauryl and caprylyl had little effect. Insertion of L-proline into a hexadecapeptide conjugate abolishing the possibility of helix formation gave an immunogen to which individual animals clearly responded on a low level. Oligomerisation, but not the cytolytic activity of melittin peptides, may contribute to the immunogenicities observed.