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.