Expression optimization and preliminary identification of recombinant monoclonal antibody IgA against SARS-CoV-2 / 中国生物制品学杂志

ABSTRACT

@#Objective To prepare monoclonal antibody IgA against severe acute respiratory syndrome coronavirus 2(SARSCoV-2),optimize relevant expression conditions to increase the expression level,and preliminarily explore the effect of IgA antibody on anti-SARS-CoV-2.Methods The plasmid encoding IgAl-F61 antibody sequence was mixed with polyethyleneimine(PEI) transfection reagent and then transfected into EXPi293F~(TM) cells to transiently express antibody protein;The optimal culture conditions and expression levels of monomeric IgAl(mIgAl)-F61 and dimeric IgAl(dIgAl)-F61 in EXPi293F~(TM) cells were determined by optimizing the ratio of heavy chain(Hc),light chain(Lc) and joining chain(Jc),the proportion of plasmid and PEI,and the harvest time after transfection.The supernatant after transfection was purified by affinity chromatography,and then determined for the concentration by BCA,analyzed for the expression integrity and purity of antibody by SDS-PAGE and size exclusion chromatography-high performance liquid chromatography(SEC-HPLC),and detected for the neutralizing activity of antibody by pseudovirus neutralization assay.Results The optimal expression level of mIgAl-F61 was 123.45 μg/mL and the purity of purified antibody was over 95% when the ratio of Hc to Lc was 12,the ratio of plasmid to PEI was 13,and the supernatant was harvested 5 d after transfection;The highest purity of dIgAlF61 was more than 90% when the ratio of HcLcJc was 121.The results of pseudovirus neutrali-zation assay against Omicron BA.4/5 showed that dIgAl-F61 exhibited better neutralizing activity than IgG-F61,and the value of half maximum inhibitory concentration(IC_(50)) was reduced by about 4 times.Conclusion Recombinant monoclonal antibodies mIgAl-F61 and dIgAl-F61 against SARS-CoV-2 were successfully expressed with high purity and dIgAl showed better neutralizing activity than IgG in vitro.