Potential of Antibody-Dependent Cellular Cytotoxicity in Acute and Recovery Phases of SARS-CoV-2 Infection

Background::Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has caused a global pandemic that has resulted in millions of casualties. Although researchers have reported the existence of neutralizing antibodies and viral T cell immunity against SARS-CoV-2, little is known about the presence of antibody-dependent cellular cytotoxicity (ADCC) and its role in combating SARS-CoV-2 infection.Methods::Nineteen acute COVID-19 patients at the First Affiliated Hospital of Guangzhou Medical University from January to February, 2020 and 55 recovery COVID-19 patients at the Second Peoples Hospital of Changde City from February, 2020 to February, 2021 were recruited in this study. Longitudinal plasma samples were collected. A virus-specific ADCC assay was performed to study the COVID-19 plasma samples. The correlations between ADCC and total IgG titer, including anti-RBD, anti-N, and neutralizing antibody titer were analyzed.Results::A high level of ADCC with 0.86% of IFN-γ +CD107a + NK cells induced by anti RBD antibodies and with 0.54% of IFN-γ +CD107a + NK cells induced by anti N antibodies was observed. This activity peaked at 3 weeks after disease onset with 1.16% and 0.63% of IFN-γ +CD107a + NK cells induced by anti RBD and anti N antibodies respectively, declined to 0.32% and 0.32% of IFN-γ +CD107a + NK cells respectively after more than 2 months, and persisted for 12 months after disease onset. The ADCC did not aggravate the severity of COVID-19 in terms of sequential organ failure assessment, although ADCC decreased with the age of COVID-19 patients. Interestingly, ADCC response is not correlated with neutralizing antibody titer or total IgG titers against S protein RBD and N protein in acute patients. ADCC in recovered patients showed a significant correlation with anti RBD IgG titer ( R2=0.33, P < 0.001). Conclusion::Antibodies from COVID-19 patients against the N protein and S protein RBD domains could stimulate high levels of ADCC response. Our results provide evidence that vaccination should not only focus on neutralizing antibodies but also binding antibodies that may facilitate the antiviral function of ADCC, especially in the elderly.