全球合作消灭脊髓灰质炎（以下简称“脊灰”）取得了重要进展，野毒株（WPV）仅在巴基斯坦、阿富汗两个国家流行，脊灰有望成为继全球消灭天花后第二个被消灭的病毒性传染病。全球消灭脊灰后，由于口服脊髓灰质炎减毒活疫苗（Oral Polio Vaccine, OPV)可引起疫苗相关病例（Vaccine-Associated Paralytic Poliomyelitis, VAPP）和疫苗衍生株病例（Vaccine-Derived Poliovirus, VDPV），将被停止使用，必须采用脊灰灭活疫苗（Inactivated Polio Vaccine, IPV）来维持无脊灰状态。减毒株（Sabin株）生产的脊髓灰质炎灭活疫苗（Inactivated Polio Vaccine, Sabin strain, sIPV)，因其生物安全性高，适合在全球尤其第三世界国家推广使用。

因sIPV疫苗抗原用量是OPV的100至300倍，难于生产足够疫苗供全球使用。皮内具有丰富的朗格汉斯细胞（LC）和树突状细胞（DC），皮内免疫可以增强抗原的免疫应答。本研究以我所已经上市的sIPV疫苗全剂量肌肉免疫作为对照，采用有针和无针注射器进行1/10,1/5,1/3剂量皮内免疫途径的比较研究，并观察了1剂sIPV诱导的致敏反应（priming）、皮内免疫持久性以及免疫记忆性。结果表明：1）Wistar大鼠3剂免疫后1/5及1/3剂量皮内免疫效果良好，Ⅰ、Ⅱ、Ⅲ型抗体阳转率与全剂量肌肉免疫相当（P>0.05），且均达到了100%，各型别抗体几何平均滴度（GMT）1/5剂量组均高于1:148.67，1/3剂量组均高于1:381.09，两组GMT均远高于保护滴度1:8。版纳小耳猪3剂基础免疫后， 1/5及1/3剂量无针皮内免疫效果良好，各型别抗体阳转率与全剂量肌肉免疫没有统计学上的显著差异（P>0.05），除了Ⅱ型1/5剂量组为80%外，其余各型均达到了100%，1/5剂量组各型别的GMT高于1:78.58，1/3剂量组高于1:80.36。2）豚鼠及小型猪动物模型全身过敏反应试验及刺激性试验结果表明无针注射皮内免疫途径具有良好的安全性。3）大鼠基础免疫后12个月，1/5及1/3剂量无针皮内免疫组各型别抗体阳转率维持在80%以上，抗体水平维持在11.12以上；加强免疫30天后，1/5剂量、1/3剂量无针皮内免疫组抗体阳转率均达到100%，GMT显著升高，分别高于1:509.35、1:827.43。版纳小耳猪基础免疫后6个月，1/5及1/3剂量无针皮内免疫途径各型别抗体阳转率维持在80%以上，抗体水平维持在29.20以上；加强免疫30天后，抗体阳转率均达到100%，GMT显著升高，1/5剂量高于1:1723.3，1/3剂量高于1:1536.9。4）大鼠及版纳小耳猪第2剂sIPV免疫后7天1/10、1/5、1/3剂量皮内免疫组以及全剂量肌肉免疫组抗体水平均显著增长8-40倍，即均能够诱导priming免疫应答反应。进一步研究发现大鼠及版纳小耳猪1/5、1/3剂量sIPV 无针皮内免疫能够产生免疫记忆性，辅助性T细胞（CD3+CD4+）数量较生理盐水对照组高13-15倍，活化T细胞（CD4+INF-γ+）、（CD8+INF-γ+）分别较对照组高2.9、1.9倍，记忆T细胞（CD3+CD161+）较对照组高1.6-1.7倍，记忆性B细胞（CD3-CD21+）数量较对照组高2.6-4倍，加强免疫后能够快速诱导产生较高的中和抗体水平，提示1/5及1/3剂量sIPV无针皮内免疫途径具有较好的免疫记忆性，加免后诱导的免疫效果显著。

综上所述，我们完成了sIPV皮内免疫分部剂量的安全性及免疫原性的临床前研究，表明1/5剂量sIPV皮内免疫在动物模型中具有良好的安全性及免疫原性，皮内免疫途径降低sIPV的抗原使用量是可行的。

Global cooperation in the eradication of polio has made important progress. Wild strain Poliovirus (WPV) is only epidemic in two countries now, Pakistan and Afghanistan. Polio is expected to be the 2^nd eradicated disease after smallpox in children populations in the global world. OPV may cause vaccine-associated paralytic poliomyelitis (VAPP) and vaccine-derived poliovirus (VDPV) after the global eradication of poliomyelitis. We must use the inactivated poliovirus vaccine (IPV) to replace the use of OPV to maintain polio free status. IPV derived from Sabin strains (Sabin strain, sIPV), which has high bio-security, is suitable for using especially in the third world countries around the world.

However, the preparation of sIPV vaccines also requires for large amount of antigen, which would be over 100 to 300 times the amount of OPV. It is difficult to produce enough sIPV to be used globally. Intracutaneous skin has rich Langerhans cells (LC) and Dendritic cells (DC), which could enhance the immune response. In this study, we have used our prepared sIPV vaccine as a control, and carried out the comparative research on the fractional doses (1/10, 1/5, 1/3 dose) sIPV with intradermal immune using the needle syringe or the needle free devices. We also carried out the study on the priming induced by a single dose, immune persistence and the immune memory of intradermal sIPV. The results of study show that: 1) After three dose schedule in Wistar rats, the seroconversion of 1/5 and 1/3-dose groups have no significant differences with full dose group (P> 0.05). The seroconversion of type Ⅰ, Ⅱ and Ⅲ are all up to 100%. The neutralizing antibody level of 1/5-dose group was higher than 1:148.67, and 1/3-dose group was higher than 1:381.09, which were much higher than the protective titer 1: 8. After three dose schedule in pigs, the seroconversion of 1/5 and 1/3-dose groups have no significant differences with full dose group (P> 0.05). The seroconversion of type Ⅰ and Ⅲ are both up to 100%, and type Ⅱ is 80%. The neutralizing antibody level of 1/5-dose group was higher than 1:78.58, and 1/3-dose group was higher than 1:80.36. 2) The results of the systemic allergy test and stimulation test in guinea pigs and mini pigs show that the intradermal immunization using needle free injector has good safety. 3) 12 months after the 3 dose schedule in rats, the seroconversion of 1/5 and 1/3-dose intradermal groups remained above 80%. The neutralizing antibody level remained above 11.12. A month after booster immunization, the seroconversion of 1/5 and 1/3-dose intradermal groups were up to 100%, and GMTs were higher than 1:509.35 and 1:827.43 respectively. 6 months after the 3 dose schedule in pigs, the seroconversion of 1/5 and 1/3-dose intradermal groups remained above 80%. The neutralizing antibody level remained above 29.20. A month after booster immunization, the seroconversion of 1/5 and 1/3-dose intradermal groups were up to 100%, and GMT were increased much higher than 1:1723.3 and 1:1536.9 respectively. 4) 7 days after second dose schedule in rats and banna mini pigs, the GMT level of 1/10, 1/5, 1/3-dose intradermal immunization groups and full dose group were 8-40 times increased, which could induce priming immune response. Further study has found that the 1/5 and 1/3-dose sIPV with intradermal immunization using needle free injector groups can produce immune memory. Helper T cells (CD3+CD4+) were 13-15 times higher than the number of negative control group. Functional T cells (CD4+INF-γ+) and (CD8+INF-γ+) were 2.9 and 1.9 times higher than the number of control group, respectively. And the memory B cells (CD3-CD21+) were 2.6-4 times higher than the number of negative control group. The neutralizing antibody level could be increased significantly by booster immunization. These results show that the 1/5 and 1/3 dose sIPV with intradermal immunization using needle free injector could induce immune memory. The immune effect was significantly increased after the booster immunization. 

In conclusion, we completed the preclinical study of the safety and immunogenicity of fractional dose intradermal sIPV. The results indicated that the 1/5-dose sIPV with intradermal immunization pathway have good safety and immunogenicity in animal models. Thus, it is feasible to reduce the amount of sIPV antigen with intradermal immunization.