Antibody Dynamic Profiles In The First Wave Of Survivors With Severe COVID-19

The coronavirus disease 19（COVID-19）pandemic,caused by severe acute respiratory syndrome coronavirus 2（SARS-Co V-2）,has become the worst public health crisis in a century.As of May 2022,COVID-19 has infected over 500 million people and the number of cases is still increasing by more than one million a day.Antibody response plays an important role in host resistance to viral diseases and reinfections and is tightly correlated with the convalescent processes of patients.Given the public health emergency and threat caused by the COVID-19 pandemic,it is critical to better understand the host antibody responses in patients with COVID-19,particularly those with severe symptoms.Thus far,dynamic changes of antibodies against SARS-Co V-2 in patients with COVID-19 have been mainly concentrated in patients who are asymptomatic or those with mild symptoms.However,in patients with severe COVID-19 symptoms,the effectiveness and durability of serum antibody protection after experiencing severe bodily damage requires more attention.Additionally,this knowledge will be helpful for addressing the most urgent concerns,including reinfection,herd immunity,and vaccine efficacy.The dynamic characteristics of the antibodies with neutralizing activity reflect the protective immune responses in patients with COVID-19 and the vaccinated population.However,little is known about the magnitude,functionality,and longevity of neutralizing antibody responses in patients with COVID-19,especially in severe cases.Herein,we focused on 104 patients with severe COVID-19 who were among those of the first wave of COVID-19 in Wuhan and performed serological tests to measure the RBD-,N-,and S-Ig G dynamic changes in serum approximately 6–7months after disease onset.Serum samples from these patients were collected at the acute phase and the convalescent phase,respectively.The median sample-collecting time of the acute phase for these patients was 23 days（IQR,20–27 days）after the disease onset and that of the convalescent phase was 172 days（IQR,167–176 days）after the acute phase sampling.Additionally,31 healthy donors were also enrolled in the cohort as controls for comparison.Ig G antibodies against RBD,S,and N proteins were detected with anti-RBD,S,and N protein Human Ig G ELISA kit.Virusneutralizing activity of convalescent serum is examined by microneutralization assay.Through the follow-up on early patients with severe COVID-19,we found that,although Ig G levels of patients with severe COVID-19 at the convalescent phase were generally lower compared with those at the acute phase,the serum antibodies of 96.7%patients were still able to neutralize SARS-Co V-2.The correlation between RBD-Ig G levels and neutralizing antibody titers in serum of patients with severe COVID-19 was also analyzed.To further explore the antibody dynamic profiles of patients with severe COVID-19,we compared the AUC values of RBD-Ig G,S-Ig G,and N-Ig G of 104 patients with COVID-19 at the acute and the convalescent phase and examined the details of the alterations of the antibody levels in each subject.The AUC values of RBD-Ig G in 91.35%,S-Ig G in 57.69%,and N-Ig G in 93.27% of the total patients were found to decline,respectively.Moreover,there was no significant difference in these dynamic changes between different age groups or sex groups.