Effects of toxoiding agents on protective antigens of Bordetella pertussis and on other proteins.

In the preparation of acellular pertussis vaccines (usually containing pertussis toxin (PT), filamentous haemagglutinin (FHA) and agglutinogens (AGGs), inactivation of the toxic PT component is necessary. This investigation stems from the work of Christodoulides et al., who observed that toxoiding of a mixed antigen preparation from B. pertussis consisting of PT and FHA in a 1:1 ratio with a commercial conjugation reagent 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDAC), resulted in an enhanced immunogenic response to these antigens. The objectives of the present study were to determine if this effect could be confirmed and whether the enhanced response was still elicited after immunization of PT or FHA treated separately with EDAC. Also, by using other antigens namely ovalbumin (OA) and lysozyme (LZ), the possible restriction of this toxoiding/adjuvanting effect to the antigens of B. pertussis was examined. As controls, the antibody responses after immunization with formaldehyde and glutaraldehyde treatments were also explored. The work started with two model antigens, ovalbumin and lysozyme, to test the specificity of the adjuvanting effect of EDAC. These proteins were treated with EDAC under conditions described for toxin inactivation and at several other concentrations. On SDS polyacrylamide gels, an extra band (thought to be a dimer) was observed for LZ but not with OA. Immunization of mice followed by ELISA on the sera gave anti-OA and anti-LZ titres. Two independent experiments showed that whilst EDAC treatment resulted in enhanced anti-LZ titres, it actually depressed anti-OA titres. Another experiment where EDAC concentration was varied during OA treatment showed this repressive response was apparent only when OA was treated with 11 and 21 mM EDAC. The enhancing effect of EDAC does not seem to be specific to PT and FHA mixtures alone. It is variable with the antigen used and in some cases can actually depress the response. With respect to the antigens of B. pertussis adjuvanting by EDAC was obtained with PT and a PT/FHA mixture. Immunisation with FHA-E alone did not elicit an increased response. Conditions for the treatment with EDAC would have to be investigated further to ensure reliable inactivation of PT. However, with respect to antibody response, EDAC-treated PT was superior to formaldehyde or glutaraldehyde PT. (Abstract shortened by ProQuest.).