Arginine vasopressin-binding peptides derived from the bovine and rat genomes differ in their abilities to block arginine vasopressin modulation of murine immune function

Abstract

Previously we reported on a nonapeptide (binding peptide) derived by reading the complementary DNA strand of the bovine arginine vasopressin (AVP) gene in the 3′5′ direction that specifically blocks the AVP helper signal for γ-interferon (IFNγ) production by helper cell-depleted mouse spleen cultures. Bovine 5′3′ AVP-binding peptide, however, did not block AVP activity. We report here on the relative abilities of 5′3′ and 3′5′ AVP-binding peptides derived from the bovine and rat AVP genes to block the AVP helper signal for IFNγ production. The sequences of the bovine and rat 5′3′ AVP-binding peptides differ by two amino acids, whereas the 3′5′ AVP-binding peptides derived from both genes are the same. In contrast to the lack of blocking activity of the bovine 5′3′ AVP-binding peptide, the rat 5′3′ AVP-binding peptide was almost as effective as the 3′5′ AVP-binding peptide in blocking AVP function. No effect was seen with a 9-amino acid control peptide consisting of a ‘scrambled’ 3′5′ AVP-binding peptide sequence. Further, polyclonal anti-rat 5′3′ AVP-binding peptide antibodies blocked AVP activity, whereas polyclonal anti-bovine 5′3′ AVP-binding peptide antibodies had no significant effect. Polyclonal antibodies generated against the 3′5′ AVP-binding peptide also blocked AVP activity. These antibodies possibly blocked AVP function by interaction with the lymphocyte AVP receptor, since AVP specifically displaced binding of the antibodies. Both polyclonal antibodies to the rat 5′3′ and 3′5′ AVP-binding peptides cross-reacted with the heterologous peptides, but not the control peptide, by enzyme-linked immunosorbent assay, indicating that the peptides share similar antigenic determinants although their amino acid sequences are different. The data indicate that binding peptides derived from the complementary DNA strand of a gene such as AVP differ in sequence and function for different species. Given the variable success that has been reported on this approach to binding peptides, we feel that this is an important observation when considering this algorithm for the synthesis of binding peptides.