Immunogenicity Of Three Kind Of Haemophilus Influenzae Type B Polysaccharide-tetanus Toxoid Conjugate Vaccine In A Rat Model

Objective We assessed a rat model to evaluate the immunogenicity of three kind of Haemophilus influenzae type b (Hib) conjugate vaccines.We compared antibody concentration induced by these vaccines to understand whether there is difference among these Hib conjugate vaccines and provide a foundation for the vaccination of children.Methods 5-day-old Sprague-Dawley rats, in groups of 35, were injected subcutaneously with 20μl of different kind of Hib vaccines on age 5d, 19d and 12d. Control rats ,in groups of 23,were injected with saline. Blood was obtained before vaccination and 1week,2week and 4week after the last immunization. Then we detected the anti–PRP IgG by ELISA and compared the concentration of different group.Results The concentrations of antibody 1 week after the last immunization were significantly higher than pre-immunization in the three experimental groups(p <0.01).Then the antibody concentrations continued to increase 2 weeks after the last immunization (p <0.01) and significantly decreased 4 weeks after the last immunization (p <0.01). Compared antibody concentrations among the groups: there is no significant difference between groups before immunization (p> 0.01). 1 week after the last immunization, the experimental groups and control group were significantly different (p <0.01), HIBERIX group had the highest concentration, and was no significant difference with ACT-HIB group (p> 0.01),but significant higher than the Yunnan group (p <0.01), ACT-HIB group and Yunnan group were similar (p <0.01). 2 weeks and 4 weeks after the last immunization , HIBERIX group still had the highest antibody concentration in the groups(p <0.01), ACT-HIB group and Yunnan were still had no significant difference(p <0.01).Conclusion The immunogenicity of the three Hib conjugate vaccine was favorable and the trends of antibody concentrations were similar.2 weeks after the last immunization,their antibody concentrations increased higher than 1 weeks after the last immunization , then decreased 4 weeks after the last immunization. HIBERIX induced the highest concentration of antibody , ACT-HIB and the domestic vaccine induced similar concentration of antibody. So we recommended HIBERIX as the preferred vaccine .