原型株及变异株SARS-CoV-2灭活疫苗在大鼠体内的免疫原性评价

Immunogenicity evaluation of prototype and variant inactivated SARS-CoV-2 vaccines in rats

目的评价原型株、Beta株、Gamma株和Delta株SARS-CoV-2灭活疫苗在大鼠体内的免疫原性。方法分别将原型株、Beta株、Gamma株和Delta株SARS-CoV-2灭活疫苗经大腿肌内免疫5只雌性Wistar大鼠2次,间隔14 d,免疫剂量均为3μg病毒蛋白/(0.5 mL·只),初次免疫后14、28和42 d,经静脉采集血,分离血清。间接ELISA法检测血清IgG抗体水平;微量中和试验检测血清中和抗体效价;计算血清中和抗体效价的抗原比,以评价2株病毒间的抗原性差异。结果初次免疫后14 d,全部免疫血清中均可检测到针对4株病毒的IgG抗体,28 d的IgG抗体水平较14 d提高10倍以上,42 d时效价略有下降。首次免疫后14 d,免疫原型株或Delta株疫苗的大鼠血清中,针对4株病毒的中和抗体全部阳转;免疫Beta株和Gamma株疫苗的大鼠血清中,针对Beta株和Gamma株病毒的中和抗体全部阳转,针对原型株或Delta株病毒的中和抗体部分阳转。初次免疫后28 d,4种病毒免疫血清中和抗体均阳转,中和抗体效价较14 d大幅升高;初次免疫42 d时中和抗体效价较28 d总体略有下降。Beta株与Gamma株间、原型株与Gamma株间抗原性差异较小,原型株与Beta株间抗原性差异较大。结论原型株、Beta株、Gamma株和Delta株SARSCoV-2灭活疫苗均能刺激大鼠产生较高效价的中和抗体,但免疫原性有差异。

Objective To evaluate the immunogenicity of prototype strain,Beta strain,Gamma strain and Delta strain of SARS-CoV-2 inactivated vaccines in rats.Methods Five female Wistar rats were immunized with SARS-CoV-2 inactivated vaccines of prototype,Beta,Gamma and Delta strains through thigh muscle twice at an interval of 14 d,with an immunization dose of 3μg virus protein/(0.5 mL per rat).Serum samples were collected and isolated by vein 14,28 and 42 d after the first immunization.The serum IgG antibody levels were detected by indirect ELISA,the titers of serum neutralizing antibody were measured by microneutralization,and the antigenic ratios of the serum neutralizing antibody titers were calculated to evaluate the antigenicity difference between different strains.Results at 14 d after the first immunization,IgG antibodies against four strains of virus were detected in all immunized serum samples.The levels of IgG antibodies increased by more than 10 times at 28 d compared with those at 14 d,and decreased slightly at 42 d.At 14 d after the first immunization,all the neutralizing antibodies against the four strains were positive in the serum of rats immunized with prototype strain or Delta strain vaccine;In the serum samples of rats immunized with Beta and Gamma strains,all the neutralizing antibodies against Beta and Gamma strains were positive,while some neutralizing antibodies against prototype or Delta strains were positive.At 28 d after the first immunization,the neutralizing antibodies in the immune serum of the four strains were positive,and the titers of neutralizing antibodies were significantly higher than those at 14 d;The neutralizing antibody titers were slightly lower at 42 d after the first immunization than 28 d.There was small difference in the antigenicity between Beta and Gamma,prototype and Gamma,but significant difference in the antigenicity between prototype and Beta strains.Conclusion The prototype strain,Beta strain,Gamma strain and Delta strain of SARS-CoV-2 inactivated vaccines can stimulate rats to produce neutralizing antibodies with high titer,while the immunogenicity has difference.