一种新型日本血吸虫疫苗(童虫活细胞)诱导小鼠产生有效保护性免疫力的研究

Study on the protective immunity in mouse induced by a new type of vaccine,living cells of Schistosoma japonicum schistosomulum

目的观察日本血吸虫童虫活细胞诱导小鼠产生的保护性免疫效果。方法采用日本血吸虫肝期童虫的活细胞和虫体组织碎片,在未加佐剂条件下分别接种昆明小鼠,每组10只,每2周接种1次,共4次,末次接种后第7天攻击感染血吸虫尾蚴30条/鼠,感染后第42天解剖小鼠,与对照组比较检测和分析虫体发育数、虫体大小、鼠肝病变及其组织内虫卵肉芽肿大小、血清中特异性抗体水平和IgG2a/IgG1亚类比值。结果细胞接种组和虫体碎片接种组分别与PBS注射组比,虫体发育数分别下降67.6%%和46.3%;肝组织中虫卵数(LEPG)在细胞接种组和虫体碎片接种组中分别减少95.4%和64.8%;在细胞接种鼠组肝表面卵结节和虫卵肉芽肿及雄虫长度均显著小于其他两组者;特异性IgG2a/IgG1比值≥2,但总抗体水平低于虫体接种组。结论该研究首次建立了一种血吸虫细胞型疫苗研究模型,初步结果表明,在不加佐剂条件用血吸虫童虫活细胞可诱导小鼠产生显著的抗攻击感染免疫力,其机制可能主要为Th1介导的细胞免疫应答。

Objective:To observe the protective immunity induced by the schistosomulum living cells a-gainst the Schistosoma japonicum challenge infection.Methods:The liver-stage S.j schistosomula were collect-ed and the worm body tissues were cut into small fractions with scissors.A portion of worm fractions was fur-therly digested with tryposin to resolve individual cells.Kun-ming mice were vaccinated schistosomulum living cells(1.6×10each mouse)or tissue fractions(30worms each mouse)without adjuvant by subcutaneous injection for4times,one time at interval of two weeks.On the7th day after the last vaccination,each mouse was challenged with30S.j cercariae.Fourty-two days after infection,all mice were sacrificed to examine the pro-tective effect.The mean worm burden,the length of S.j worms and mean size of egg granuloma in the livers of the experimental groups were compared with those of control group.Specific antibodies and the ratio of IgG2aand IgG1were also measured.Results:Compared with the control group,reduction rate of67.6%and46.3%in the worms burden and95.4%and64.8%in the liver egg load were achieved in mouse groups immunized with schistosomulum cells or worm fractions,respectively.Mean size of egg granuloma and the length of male worm were also significantly smaller in the cell-vaccinated group than the other2groups(P<0.01).Specific an-tibody level was lower and the ratio of IgG2a/IgG1was>2in the cell-vaccinated group.Conclusions:It is the first step to develop a living cell type vaccine in the S.j immunization.The preliminary result showed that living cells of S.j schistosomulum without adjuvant condition could induce significant protective immunity against S.j challenge and the Th1-cell-mediated immune response probably played a major role.