1Infectious Disease Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, Korea
2Bio-Analytical Science Division, University of Science and Technology, Daejeon, Korea
3Bionanotechnology Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, Korea
4Department of Laboratory Medicine, Gyeongsang National University Changwon Hospital, Changwon, Korea
5Department of Infectious Diseases, Gyeongsang National University Changwon Hospital, Changwon, Korea
6Gyeongnam Center for Infectious Disease Control and Prevention, Changwon, Korea
7Gyeongsang Institute of Health Sciences, Gyeongsang National University College of Medicine, Jinju, Korea
*Corresponding author: E-mail: sjkim8239@hanmail.net
ABSTRACT
Neutralizing antibodies play a critical role in blocking viral infections and in viral clearance during acute infection. The microneutralization assay and enzyme-linked immunosorbent assay (ELISA) targeting the receptor binding domain were performed for 30 patients with mild coronavirus disease (COVID)-19 infections. The elapsed number of days between sample collection and diagnosis was 115 days, and real-time polymerase chain reaction (PCR) cycle threshold (Ct) values at diagnosis were recorded. Clinical characteristics and Ct values were compared between neutralization antibody-positive and -negative patients as measured by the microneutralization assay. Neutralization antibody-positive patients (n = 9) were likely to be older, have low Ct values, have more pneumonia during admission, and have a higher optical density in ELISA than the neutralization antibody-negative patients (n = 21). Elderly people seemed to have a higher viral load causing more pneumonia and to produce more neutralization antibodies. Neutralization antibodies persisted in only 30% of patients as detected by microneutralization test after 100 days of diagnosis.