Comparison of Corynebacterium parvum and Bordetella pertussis with Freund's complete adjuvant as immunopotentiators for beta-human chorionic gonadotropin linked to an atoxic fragment of tetanus toxin.

Corynebacterium parvum and Bordetella pertussis were compared with Freund's complete adjuvant (FCA) for their abilities to potentiate the immune response to haptenic beta-human chorionic gonadotropin covalently coupled to an atoxic 54,000-molecular-weight fragment of tetanus toxin (beta-hCG-TTII). The ability of each adjuvant to enhance production of antibodies to hCG in rabbits was measured by 125I-hCG radioimmunoassay. At sera dilutions of 1:10,000, analysis of variance for the 8-week postimmunization course showed that the mean 125I-hCG binding capacities of the C. parvum group was significantly greater overall than the B. pertussis group (P = .0002) and that the FCA-treated group had the greatest binding capacity overall (P less than .018). The mean binding capacities at 1:40,000 dilution again showed the FCA-treated group to have significantly higher anti-hCG titers overall (P less than .0015), with C. parvum potentiating a greater overall antibody response than B. pertussis (P = .001). These results indicate that FCA is the most efficacious of the three tested adjuvants in potentiating antibody production to the hapten component of beta-hCG-TTII. C. parvum was also effective at promoting an anti-beta-hCG response, although not to the same degree as FCA. B. pertussis had only minimal potentiating effect compared to FCA or C. parvum.