DNA疫苗多次重复接种对特异性抗体滴度和亲合力影响

The effect of repeated DNA vaccination on titer and avidity of specific antibody

目的探索多次重复接种DNA疫苗对小鼠血清中特异性抗体滴度和亲合力的影响。方法利用表达鸡卵白蛋白(OVALBUMIN,OVA)的DNA疫苗接种小鼠,连续接种8次,间隔2周。每次免疫接种之前采集小鼠外周血,于最后一次免疫结束后6周对小鼠实施安乐死,并采集外周血和脾细胞标本。运用ELISA法测定血清中OVA特异性抗体的滴度和亲合力,运用IFN-ELISPOT技术检测小鼠脾细胞OVA特异性IFN-分泌量。结果经过3次DNA疫苗接种之后,小鼠体内OVA特异性IgG抗体的滴度较基线水平显著升高(P<0.0001),后续的重复接种不能继续提高血清中OVA特异性IgG抗体的滴度;而抗体亲合力检测结果显示,在前7次免疫过程中,OVA特异性抗体的亲合力指数稳定地维持在低水平,第8次免疫之后抗体亲合力指数才出现显著升高,明显滞后于抗体滴度的上升。在整个免疫过程中,OVA特异性IgG的亚类构成始终保持稳定。在免疫结束6周后,雌鼠具有显著高于雄鼠的IFN-分泌水平(P=0.0357),并且其血清OVA特异性抗体水平也比雄鼠更加稳定。结论间断性的、重复的DNA疫苗接种既可以提高抗原特异性抗体滴度,也可以改善特异性抗体的亲合力。但是,提高抗体亲合力所需的免疫次数明显多于提高抗体滴度所需的免疫次数。

To explore the effect of repeated inoculation with DNA vaccine on the titer and avidity of specific antibodies in mouse serum.Methods C57BL/6 mice were inoculated with a DNA vaccine expressing OVA for 8 times at a frequency of every two weeks.We regularly collected peripheral collected from all mice during the entire process of vaccination.Six weeks post the 8th vaccination,the mice were euthanized,peripheral blood and splenocyte were collected.The titers and avidity of OVA specific antibody in mouse sera were measured using an in-house ELISA method.The IFN-γELISPOT assay detected the OVA specific cellular immune responses.Results After three times of DNA vaccination,the average titer of OVA-specific IgG antibodies increased significantly comparing to the baseline level(P<0.0001),and subsequent vaccination failed to improve the titers of OVA-specific antibody responses further.Whereas,the results of antibody avidity test showed that the mean avidity index of OVA specific antibody stably was maintained at relatively low level during the first 7 shots.After the 8th immunization,the average avidity index of OVA specific antibodies increased significantly,which lagged the increase in antibody titer.During the whole immunization process,the subclass composition of OVA-specific IgG remained stable,which suggested that the upregulation of antibody avidity was not a consequence of IgG subclass switch.Our data showed that 6 weeks post the 8 th immunization,the average frequency of IFN-γsecreting cells in splenocyte of female mice was significantly higher than male mice.And also,female mice maintained the level of serum OVA specific antibody stable point,while male mice did not.Conclusion Intermitted,repeated DNA vaccination can improve both the titer and the avidity of antigen specific antibody responses.However,more shots are required for avidity enhancement than for titer improvement.