ANTIBODY AND T-CELL RECOGNITION OF ALPHA-BUNGAROTOXIN AND ITS SYNTHETIC LOOP-PEPTIDES

Peptides representing the loops and surface regions of alpha-bungaroto xin (BgTX) and control peptide analogs in which these sequences were r andomized were synthesized and used to map the recognition profiles of the antibodies and T-cells obtained after BgTX immunization. Also. th e abilities of anti-peptide antibodies and T-cells to recognize the im munizing peptide and BgTX were determined. Three regions of BgTX were immunodominant by both rabbit and mouse anti-BgTX antibodies. These re gions resided within loops L1 (residues 3-16), L2 (residues 26-41) and the C-terminal tail (residues 66-74) of the toxin. The regions recogn ized by BgTX-primed T-lymphocytes were mapped in five mouse strains: C 57BL/6(H-2(b)), Balb/c (H-2(d)), CBA (H-2(k)), C3H/He (H-2(k)) and SJL (H-2(s)). The H-2(b) and H-2(d) haplotypes were high responders to Bg TX, while the H-2(k) and H-2(s) were intermediate responders. The T-ce ll recognition profile of the peptides varied with the haplotype, cons istent with Ir gene control of the responses to the individual regions . The submolecular specificities of antibodies and T-cells were compar ed in three of the mouse strains (C57BL/6, Balb/c and SJL). In a given mouse strain, there were regions that were strongly recognized by bot h antibodies and T-cells as well as regions that were predominantly re cognized either by antibodies or by T-cells. The peptides were used as immunogens in their free form (i.e. without coupling to any carrier) in two of the mouse strains, Balb/c and SJL. In both mouse strains, th e peptides gave strong antibody responses. Antibodies against peptide L2 showed the highest binding to intact BgTX. Antibodies against the o ther peptides exhibited lower binding activity to the intact toxin, an d this activity was dependent on the peptide and the mouse strain. The response of peptide-primed T-cells to a given immunizing peptide was not related to whether this region was immunodominant with BgTX-primed T-cells. The ability of peptide-primed T-cells to recognize the intac t toxin varied with the peptide and was dependent on the host strain. These results indicate that anti-peptide antibody and T-cell responses are also under genetic control and that their ability to cross-react with the parent toxin is not only dependent on the conformational expo sure of the correlate region in intact BgTX.