The Regions on the Light Chain of Botulinum Neurotoxin Type A Recognized by T Cells from Toxin-Treated Cervical...

We have recently mapped the in vitro proliferative responses of T cells from botulinum neurotoxin type A (BoNT/A)-treated cervical dystonia (CD) patients with overlapping peptides encompassing BoNT/A heavy chain (residues 449-1296). In the present study, we determined the recognition profiles, by peripheral blood lymphocytes (PBL) from the same set of patients, of BoNT/A light (L) chain (residues 1-453) by using 32 synthetic overlapping peptides that encompassed the entire L chain. Profiles of the T-cell responses (expressed in stimulation index, SI; Z score based on transformed SI) to the peptides varied among the patients. Samples from 14 patients treated solely with BoNT/A recognized 3-13 (average 7.2) peptides/sample at Z > 3.0 level. Two peptide regions representing residues 113-131 and 225-243 were recognized by around 40% of these patients. Regarding treatment parameters, treatment history with current BOTOX^® only group produced significantly lower average T-cell responses to the 32 L-chain peptides compared to treatments with mix of type A including original and current BOTOX^®. Influence of other treatment parameters on T-cell recognition of the L-chain peptides was also observed. Results of the submolecular T-cell recognition of the L chain are compared to those of the H chain and the T-cell recognition profile of the entire BoNT/A molecule is discussed. Abbreviations used: BoNT/A, botulinum neurotoxin type A; BoNT/A_i, inactivated BoNT/A; BoNT/B, botulinum neurotoxin type B; CD, cervical dystonia; L chain, the light chain (residues 1-448) of BoNT/A; LNC, lymph node cells; H chain, the heavy chain (residues 449-1296) of BoNT/A; H_C, C-terminal domain (residues 855-1296) of H chain; H_N, N-terminal domain (residues 449-859) of H chain; MPA, mouse protection assay; SI, stimulation index (SI = cpm of ³H-thymidine incorporated by antigen-stimulated T cells/cpm incorporated by unstimulated cells); TeNT, tetanus neurotoxin; TeNT_i, inactivated TeNT.