猪链球菌2型灭活疫苗对小鼠的免疫效果评价

Evaluation of immune efficacy of inactivated Streptococcus suis serotype 2 vaccine in mice

在前期筛选出2株毒力强、抗原性好、遗传稳定的猪链球菌2型(SS2)疫苗菌株(HF2、HF3株)并分别制成灭活疫苗(采用ISA 201 VG矿物油佐剂)的基础上,进一步与SS2商品化灭活疫苗(HA9801株,铝胶佐剂)同步免疫小鼠,利用间接ELISA、流式细胞术、免疫攻毒试验、细菌定植试验和病理组织学观察等方法测定小鼠血清中IgG抗体效价,细胞因子含量(IL-4、IL-10、IFN-γ、TNF-β、MCP-1),外周血中CD4^+/CD3^+、CD8^+/CD3^+ T细胞亚群含量,攻毒保护率,组织荷菌数和病理组织变化等指标。结果显示,二免7 d后,HF2、HF3灭活疫苗组和HA9801商品化灭活疫苗组的血清IgG抗体效价分别为1∶25 600、1∶12 800、1∶25 600;HF2灭活疫苗组的IL-4、IL-10含量显著高于HF3灭活疫苗组和HA9801商品化灭活疫苗组,IFN-γ、TNF-β含量显著高于HF3灭活疫苗组,但MCP-1含量显著低于HF3灭活疫苗组;HF2和HF3灭活疫苗组的CD4^+/CD3^+ T细胞比率均显著低于HA9801商品化灭活疫苗组,但CD8^+/CD3^+ T细胞比率差异不显著;HF2、HF3灭活疫苗和HA9801商品化灭活疫苗对小鼠的攻毒保护率均为100%;HF2灭活疫苗组小鼠的肺、脾脏组织荷菌数显著低于HF3灭活疫苗组;HF2灭活疫苗组小鼠的肺、肾、脾脏病理变化较HF3灭活疫苗组和HA9801商品化灭活疫苗组轻微。综合结果表明,由SS2(HF2株)制备的ISA 201 VG佐剂灭活疫苗免疫小鼠后不仅可产生较强的免疫应答,还可完全抵抗强毒株的攻击。

In preliminary research, 2 vaccine strains of Streptococcus suis serotype 2 HF2, HF3 were screened out through pathogenicity test, antigenicity test and stability test, and been prepared into inactivated vaccine with ISA 201 VG mineral oil adjuvant. These two inactivated vaccines were immunized in mice with commercial vaccine to evaluate their immune efficacy. The titer of IgG antibody and content of cytokines(IL-4, IL-10, IFN-γ, TNF-β, MCP-1) in serum were detected by ELISA and the subpopulation of T cells of CD4^+/CD3^+, CD8^+/CD3^+ were measured by flow cytometry. The protective rate of each immunization group after challenge test, the colonization of SS2 in mice by tissue load test and the pathological sections of lung, liver, spleen and kidney of mice were collected and observed. The results showed that the serum IgG antibody titers of the SS2 inactivated vaccine(HF2 strain, HF3 strain) and the SS2 commercial inactivated vaccine(HA9801 strain) after the second immunization of mice were 1∶25 600, 1∶12 800, 1∶25 600, respectively. The content of IL-4 and IL-10 induced by HF2 inactivated vaccine were significantly higher than HF3 inactivated vaccine and commercial vaccine. The content of IFN-γ、TNF-β were significantly higher than HF3 inactivated vaccine, and the content of MCP-1 were significantly lower than HF3 inactivated vaccine. The commercial vaccine group induced mice to produce significantly higher ratio of CD4^+/CD3^+ T cells than other groups. The protection rate of HF2, HF3 inactivated vaccine and HA9801 commercial inactivated vaccine on mice were all 100%.The bacteria colonization of lung and spleen of HF2 inactivated vaccine were significantly lower than HF3 inactivated vaccine, and the pathological changes of lung, spleen and kidney were lighter than other groups. In conclusion, HF2 inactivated vaccine can not only produce a higher level of humoral immunity and cellular immunity, but also completely resist the attack of the virulent strain.