SARS-CoV-2 membrane protein is incompetent at inducing antibody-dependent enhancement though Fc receptor pathway

ABSTRACT

Objective To investigate the immune characteristics of SARS-CoV-2 membrane (M) protein, especially the possibility of inducing antibody-dependent enhancement effect (ADE) .Methods Full-length SARS-CoV-2 M protein was prepared by prokaryotic expression system and purified.BALB/ c mice were immunized subcutaneously three times (on day 1, day 14 and day 21) by purified M protein.Serum samples were collected before immunization and after each immunization.The specificity of immune sera against M protein was identified by Western blot, and the antibody titers were detected by ELISA and neutralization test.In the presence of anti-M protein serum, the proliferation of SARS-CoV-2 in dendritic cells, nature killer cells, T and B cells was detected in vitro.Results The immune sera from BALB/ c mice immunized with purified full-length M protein of SARS-CoV-2 specifically recognized viral M protein.The titer of anti-whole virus antibody in immune sera was about 1 ∶ 400, but the antibody could not neutralize live virus.Moreover, the antibody could not help the virus to infect and proliferate in the various types of immune cells with Fc receptor (FcR).Conclusions Non-neutralizing antibody induced by M protein could not cause ADE through FcR pathway.