Submolecular recognition regions of the HN domain of the heavy chain of botulinum neurotoxin type A by T cells from toxin-treated cervical dystonia patients

- In patients treated with BoNT/A, regions within peptides 631-649, 659-677 and 743-761 were frequently recognized by T cells.
- T-cell responses to HN regions may tend to occur earlier than to HC regions.
- Anti-BoNT/A Abs-positive patients had greater overall T-cell responses against HN peptides than the Ab-negative cases.
- Number of HN-domain peptides recognized by T-cells was significantly smaller compared to number of recognized HC-peptides.
- Ab + CD patients mounted significantly elevated T-cell responses toward HN regions but not toward the HC region.

We have recently reported the submolecular T-cell recognition profile of the C-terminal half (HC, residues 855-1296) of the heavy (H) chain of botulinum neurotoxin type A (BoNT/A) with peripheral blood lymphocytes (PBL) from 25 BoNT-treated cervical dystonia (CD) patients. In the current study, we describe the mapping of the T-cell responses of the patients to the N-terminal half (HN, residues 449-859) of the heavy chain by using 29 synthetic overlapping peptides encompassing the entire HN domain of BoNT/A. The profiles of the T-cell responses to the peptides varied among the patients. Samples from 14 patients treated solely with BoNT/A recognized 1-9 (average 3.7) peptides/sample at Z > 3.0 level. Three peptide regions representing residues 631-649, 659-677 and 743-761 were frequently recognized by 29-64% of the patients. In patients with positive anti-BoNT/A antibody responses the overall positive T cell responses to the HN peptides were significantly increased compared to antibody-negative patients. Influence of treatment parameters on the T-cell recognition of the HN peptides was also observed. The results were compared with those of previously identified HC region.

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