The Effect Of Aluminum Adjuvant And Immunization Schedule On Immunogenicity Of Sabin Inactivated Poliovirus Vaccine

In the past half-century,polio vaccine has played a very important role in the action of the Global Polio Eradication.Two kinds of vaccines are commonly used in the world,one is the Oral poliovirus vaccine(OPV),the other one is the Inactivated poliovirus vaccine(IPV).OPV plays an important role in the process of Global Polio Eradication,but some shortcomings such as its unsafe feature which can cause paralysis cases gradually exposed.OPV can cause more serious consequences than the input virus and the virus leak from laboratory due to its simple structure and variability.WHO has made a policy that we should stop using OPV after the Globe Polio Eradication,so a more effective,safer,more manageable virus are inactivated polio vaccine is demanded urgely.WHO recommends to use Sabin IPV instead of OPV,in order to solve the problems which caused by OPV such as VDPV or VAPP.Sabin strains’immunogenicity decrease after inactivated by formaldehyde,so how to improve the immunogenicity of Sabin IPV become a major issue.This research studies the effect of aluminume adjuvant and immunization schedule on immunogenicity of Sabin inactivated poliovirus vaccine.According to the results of our clinical trials of Sabin IPV,the Ⅰ、Ⅱ、Ⅲ type antigen content of30、32and45(DU/dose)achieved better results,we select the antigen content30、32and45(DU/dose)and15、16and22.5(DU/dose) to study the effect of aluminume adjuvant and immunization schedule on immunogenicity of Sabin IPV.In part1of the study,we detected the serum antibody levels after3doses, compare the immunization schedules among different groups and compare different groups under the same immunization schedule. Four batches of Sabin IPV were produced by different concentrations of typel,2,and3poliovirus and administrated on three-dose schedule at0,1,2months and0,2,4months on rats.Serum samples were collected one month after each dose and neutralizing antibody titers against three types poliovirus were determined by micro-neutralization assay. The GMTs of neutralizing antibodies against three types poliovirus increased significantly and the seropositivity rates were100%in all groups after3doses.There is no significant difference between the two immunization schedules,but the0,2,4month schedule could induce higher level neutralizing antibody compared to the0,1,2month schedule.Comparing different groups under the same immunization schedule, The groups with aluminum adjuvant could induce higher level neutralizing antibody compared to the groups without adjuvant.The middle D antigen of Sabin IPV with aluminum adjuvant group induced the highest level neutralizing antibody,the low D antigen of Sabin IPV with aluminum adjuvant group indeced the same level antibody with the middle D antigen of Sabin IPV group,the low D antigen of Sabin IPV induced the lowest.What’s more,the group with aluminum adjuvant can induce neutralizing antibody quicker and early than the group without adjuvant. Aluminum adjuvant and immunization schedule could improve the immunogenicity of Sabin IPV.In part2,study on antibody titer in different time intervals after immunized by Sabin IPV.What’s more we also compare the immunization schedules among different groups and compare different groups under the same immunization schedule.After primary immunization,we collected the serum every three months to detect the neutralizing antibody level in order to study the immune persistent.Results of serum neutralization test showed that the seropositivity rates of type Ⅰ、Ⅱ and Ⅲ neutralizing antibody in Sabin IPV keep in100%.Although the antibody level dropt as time goes,the antibody stay in a high level and have a better immune effect.The0,2,4months immunization schedule can better induce neutralization antibody than the0,1,2months immunization schedule.Comparing different groups under the same immunization schedule,the groups with aluminum adjuvant have a higher level antibody as time goes than the group without adjuvant. The low D antigen of Sabin IPV with aluminum adjuvant group indeced the same level antibody with the middle D antigen of Sabin IPV group,the low D antigen of Sabin IPV induced the lowest level antibody.