Neutralizing activity of immunoglobulin preparations against SARS-CoV-2 in vitro
Objective To evaluate the neutralizing antibody level of the population to SARS-CoV-2 and its variants before and after vaccination.Methods A total of 37 samples of immunoglobulin preparations were collected.According to the time of plasma collection,taking the time of SARS-CoV-2 vaccine intensive inoculation(September 2021)and the time of epidemic prevention policy change(December 2022)as nodes,the immunoglobulin preparations produced in different time periods were divided into three groups:19 samples of plasma collected from February 2019 to October 2021 in group 1,8 samples of plasma collected from March 2022 to December 7,2022 in group 2,and 10 samples of plasma collected from January 2023 to February 2023 in group 3.The neutralizing antibody levels of the wild strain,Delta strain,Omicron BA.5,BQ.1 and XBB variant strains were measured by micro neutralizing antibody assay,and the geometric mean titers(GMTs)of the antibodies were calculated.Results The SARS-CoV-2 wild strain neutralizing antibody was detected in only 5 of the 19 immunoglobulin preparations prepared by plasma collected before 2021,with the titer of not more than 1∶20,and no neutralizing antibody against the other four variants was detected.From March to December 2022,the neutralizing antibody titers of eight immunoglobulin preparations against the five SARS-CoV-2 strains increased significantly,of which the wild strain(1∶2 560)and Delta strain(1∶1 810)had the highest titers,followed by the Omicron strains(GMTBA.5=1∶830;GMTXBB=1∶104;GMTBQ.1=1∶22).Among the 10 immunoglobulin preparations prepared by plasma collected in 2023,the neutralizing antibody titers of the five strains showed little change.The GMTs of the five strains of antibodies were:wild strain(1∶2 079),Delta strain(1∶1 114),Omicron BA.5(1∶970),Omicron BQ.1(1∶69),and Omicron XBB(1∶121).There was no significant difference in the GMTs of the five strains between the two groups of immunoglobulin preparations(t=1.249,1.495,0.370 2,1.160 and 0.502 8,respectively,each P＞0.05).Conclusion The neutralizing antibody level of SARS-CoV-2 has significantly increased in immunoglobulin products after the implementation of enhanced inoculation of SARS-CoV-2 vaccine in China,while compared with Omicron and its branch strains,inactivated SARS-CoV-2 vaccine has better protection effect on SARS-CoV-2 wild strain and Delta strain.
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