Analysis of antibody titers in patients with COVID-19 6 months after infection

ABSTRACT

Objective To analyze the antibody against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) of recovered patients with confirmed or suspected Coronavirus Disease 2019 (COVID-19) in Dawu County, Hubei Province, China 6 months after discharge from hospital. Methods A total of 166 serum samples were collected from the recovered patients with COVID-19 6 months after discharge from hospital and determined for neutralizing antibody by plaque reduction neutralization test (PRNT), and the neutralizing antibody titer (EC50) was calculated. The specific IgG antibody against SARS-CoV-2 was determined by ELISA, of which the relationship to the neutralizing antibody titer was analyzed by Pearson method. Results The positive rates of neutralizing antibody and specific IgG in the 166 samples were 68. 7% and 77. 7%, while those in samples from patients with typical symptoms were 82. 2%, and 90. 1%, those from confirmed patients without symptoms were 66. 7% and 88. 9%, and those from suspected patients were 44. 6% and 53. 6%, respectively. The Pearson relationship between neutralizing antibody titer and IgG titer was 93. 0%. Conclusion The antibody against SARS-CoV-2 still exists in patients with confirmed or suspected COVID-19 6 months after discharge from hospital, and the titer of neutralizing antibody is significandy related to that of specific IgG against SARS-CoV-2. Copyright © 2022 Changchun Institute of Biological Products. All rights reserved.