Immune recognition of botulinum neurotoxin type A:: Regions recognized by T cells and antibodies against the protective HC fragment (residues 855-1296) of the toxin

Botulism toxicity is caused by botulinum neurotoxins (BoNTs), a group of protein neurotoxins produced by Clostridium botulinum. Recent studies have shown that immunization with a C-terminal fragment (H-C, residues 855-1296) of BoNT type A (BoNT/A) affords excellent protection against BoNT/A toxicity. The present work was carried out in order to map the molecular and cellular immunological recognition of H-C. We have previously described the synthesis of 31 overlapping peptides encompassing the entire H-C-fragment of BoNT/A. These peptides were employed in this study to localize the continuous regions recognized by T cells and by antibodies (Abs) generated in two mouse strains against H-C. T cells from SJL that had been primed with H-C gave a strong proliferative response to challenge in vitro with each of the six peptides spanning residues 897-985 and a lower response to peptide 1051-1069. While H-C-primed T cells of BALB/c recognized three regions residing within residues 939-957, 1009-1027 and 1135-1153 (strong). Recognition regions by Abs in SJL or BALB/c anti-H-C antisera essentially overlapped. However, the level of Abs bound to each region differed between the two strains. These common or similar recognition regions by the two strains were: 855-915 (SJL) or 855-901 (BALB/c); 939-957; 967-1013 (BALB/c) or 981-1013 (SJL); 1051-1069; 1079-1111 (BALB/c) or 1093-1125 (SJL); 1177-1195; and 1275-1296. In addition, BALB/c recognized region 1135-1153. Some of these regions show considerable sequence similarity in BoNT types B and E and, therefore, H-C of these two BoNTs might offer protection against the correlate clostridial toxins. (C) 1997 Elsevier Science Ltd. All rights reserved.