Preparation of a diphtheria toxin-pullulan conjugate that elicits good IgG antibody production with poor IgE synthesis.
Diphtheria toxin is detoxified through conjugation with pullulan. The toxin-pullulan conjugate is easily purified by DEAE-Sephacel chromatography. The conjugate forms a transparent 'clear line' with anti-toxin antibodies on agarose plate, which offers a good indicator of conjugate formation. The toxin-pullulan conjugate induces both IgG1 and IgG2b antibody production with diminished IgE response, while the alum-precipitated conventional toxoid causes mainly increases in IgE as well as IgG1 antibody formation. The anti-toxin HA titre (IgG antibody) induced by the toxin-pullulan conjugate parallels the neutralizing activity of the immune-sera. These results suggest that the conjugation of toxin to pullulan is a very powerful method by which to develop a vaccine that induces neutralizing antibody with diminished IgE antibody synthesis.