Immunogenicity, safety and stability of the ACPS-BOMPC conjugate of Neisseria meningitidis

Objective To evaluate the immunogenicity, safety and stability of the prepared conjugate ACPS-BOMPC of Neisseria meningitidis(Nm). Methods The immunogenicity and stability of the ACPS-BOMPC conjugate were determined by immunological experiments in mice and rabbits, ELISA and bacteriocidal test. The safety of the conjugate was confirmed in the toxic test of mice and guinea pigs. Results The antibody titers against the conjugate in 87.5% (14/16) of mice reached up to 1∶7 240-1∶20 480 and the antibody titers against capsular polysaccharide of Nm serogroup A (ACPS) in 81.25% (13/16) of mice reached up to over 1∶320. The immunogenicity of the ACPS in the conjugate was enhanced over 8 to 128 times as high as unconjugated ACPS. The high antibody titers (over 1∶25 600 against the conjugate and 1∶3 200-6 400 against ACPS) were induced by the conjugate and maintained over five months in rabbits. Seven mice in which had been immunized by the above conjugate were attacked with the strain 3407 (5×10 9 CFU), five of them survived, but only one mouse survived in the control group in which seven mice were injected normal saline instead of the conjugate. It was primarily showed by the immunological experiments that the conjugate possessed some protective effect for the infection of Nm serogroup B. The safety of the conjugate was defined to be safe in the toxicity test of mice and guinea pigs. Conclusion The ACPS-BOMPC conjugate not only possessed strong immunogenicity to Nm serogroup A and serogroup B but also enhanced the immunogencity of ACPS. It is hopeful that the above conjugate is used as a candidate of vaccine in preventing infections of Nm both serogroup A and B.