Increased anti-SARS-CoV-2 antibody titers in plasma-derived intravenous immunoglobulin collected in Southern China.

Although the COVID-19 pandemic is no longer considered an emergency, the ongoing spread of the virus poses a persistent threat to public health. COVID-19 poses a challenge to the system due to the risk of saturation and the associated economic burden. To assess changes in the anti-SARS-CoV-2 antibody profile, we analyzed nine batches of intravenous immunoglobulin (IVIG) prepared from plasma samples collected between November 2020 and June 2023. Antibody changes against SARS-CoV-2 spike, nucleocapsid, and membrane proteins, and neutralizing antibodies were measured. Antibody titers against wild-type SARS-CoV-2 and the three variants consistently increased. Furthermore, different IVIG batches demonstrated that antibody-dependent cellular cytotoxicity activity was correlated with anti-spike and neutralizing antibody titers. The anti-SARS-CoV-2 antibody titers fluctuated according to the progress of the pandemic and changes in COVID-19 vaccine coverage. Our research shows that immune cell-mediated virus elimination and the neutralizing effects of anti-SARS-CoV-2 antibodies underlie the therapeutic effects of IVIG.