Monitoring of diphtheria, pertussis and tetanus toxoids by circular dichroism, fluorescence spectroscopy and size-exclusion chromatography.

A combination of spectroscopic and chromatographic methods has been used to monitor the quality and integrity of diphtheria, pertussis and tetanus toxoids (DTxd, PTxd and TTxd) which have been prepared from the toxins by formaldehyde treatment. Different processes for detoxifying all three toxins have yielded toxoids varying in their molecular size, including oligomers (associated monomers) and aggregates (high molecular weight complexes of non-specifically associated monomers). Changes in the intrinsic fluorescence spectra of the polypeptides have been observed in some sized fractions of DTxd and PTxd. Some physico-chemical changes have been observed to correlate with a loss of antigenicity. Spectroscopic and chromatographic methods are useful not only in monitoring the stability and consistency of vaccine starting materials, but can also be used to dissect heterogeneous toxoid preparations.