Reduction of antibody response against botulinum neurotoxin A by synthetic monomethoxypolyethylene glycol-peptide conjugates.

Recently, we determined the molecular locations on BoNT/A of the antigenic regions recognized by blocking Abs of cervical dystonia patients immunoresistant to BoNT/A treatment. In the present work we tested the possibility of reducing the levels of the Ab response against immunodominant antigenic sites on the heavy chain of BoNT/A in order to diminish immunoresistance caused by blocking Abs. Four antigenic regions on BoNT/A represented by peptides N8 (residues 547-565), N25 (785-803), C15 (1051-1069) and C31 (1275-1296) were tested for suppressing Ab responses against the correlate regions. The conjugates were synthesized with monomethoxypolyethylene glycol (mPEG) attached to the peptide N-termini. Tolerization with a given mPEG-peptide reduced the Ab levels against the correlate region and the antisera became less protective than antisera of untolerized controls that were immunized only with inactive BoNT/A. On days 31 and 52 in the immunization course mPEG-N8 was most effective and the antisera of tolerized mice were weaker and less protective relative to controls. Other mPEG-peptides were also suppressed the Ab responses to various extents. Bleeds up to 5 months showed that tolerization can be made to persist for the entire period. The results indicated that the tolerization procedure might be potentially useful for clinical applications to immunoresistant patients.