D-MK conceived and revised the manuscript
D-MK conceived and revised the manuscript. 10 and 15 in asymptomatic and symptomatic patients, respectively. The asymptomatic group had a significantly higher neutralizing potency index than the mild-to-severe illness groups. == Conclusions == Neutralizing antibodies corresponded to earlier seroconversion but had a shorter presence in the asymptomatic group than in the symptomatic group and were still present 1 year after symptom onset in crucial/fatal cases. Keywords:severe acute respiratory syndrome coronavirus 2, COVID-19, antibody response, neutralizing antibody, neutralization potency, 1-12 months follow-up == Introduction == Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread rapidly worldwide. Neutralizing antibodies are powerful molecules that constitute a protective immune response against viral infections because they can bind to viral particles and block them from entering the host cells (1,2). Virus-neutralizing antibodies may be correlated with protection against COVID-19. Therefore, data around the kinetics of virus-neutralizing antibody responses are required (3,4). Although several studies have shown that protection against COVID-19 may be correlated with the development of high titers UTP14C of neutralizing antibodies (5,6), the role of antibodies in COVID-19 is usually controversial owing to reinfection and the occurrence of severe disease despite high antibody titers. Garcia-Beltran BNS-22 et al. explained the efficacy of the humoral immune response against COVID-19 through quantifying it using the neutralization potency index (titers that achieve 50% neutralization [NT50]/immunoglobulin [Ig] G) and showed neutralization potency as a survival predictor (7). Nonetheless, follow-up studies comparing titers of antibodies, including neutralizing antibodies, based on disease severity and the period after symptom onset have rarely been performed. Therefore, we conducted a 1-12 months follow-up investigation to examine antibody responses, including neutralizing antibodies, in patients with COVID-19. We analyzed the relationship between the antibody response and neutralizing antibody activity as a function of disease severity and period after symptom onset. == Materials and methods == BNS-22 == Clinical data and specimens == Clinical data and specimens were obtained from unvaccinated patients COVID-19 who were hospitalized or followed at Chosun University Hospital in Gwangju Metropolitan, South Korea. The individuals recruited for this study were patients with SARS-CoV-2 contamination between February 2020 and February 2021, prior to the occurrence of the SARS-CoV-2 variant(s). For diagnosis, a molecular method was used, namely, our in-house-designed reverse transcription polymerase chain reaction (RT-PCR) targeting theNgene, and a commercial kit (Kogene Biotech Seoul, South Korea) targetingEandRdRpgenes, according to the manufacturers protocol. COVID-19 was diagnosed when more than two genes were detected at a Ctvalue <38 or when the SARS-CoV-2 culture showed a positive result. For patients with a body temperature of 37.5C, the time to fever clearance was defined as the period from the initial fever onset until the body temperature decreased to 37.3C and remained below this temperature for at least 48 h without the use of an antipyretic. COVID-19 patients were divided into four groups based on disease severity: asymptomatic patients (n = 24), those who BNS-22 had no symptoms throughout the course of the infection; patients with mild-to-moderate illness (n = 36), those who were symptomatic but did not receive supplemental oxygen or supplemental oxygen via a nasal prong; severely ill patients (n = 14), those who required high-flow oxygen therapy; and crucial/fatal cases (n = 23), those who required mechanical ventilation or died. Chest radiography was performed on the day of hospitalization. X-ray scores were obtained by dividing each lung into upper, middle, and lower zones and scoring each zone from 0 to 4 points based on the degree of infiltration. The scores for each lung (with a total of six zones) were summed to yield a total score of 024 (8). The study protocol was approved by the Institutional Review Board of Chosun BNS-22 University Hospital (approval no. CHOSUN 2020-11-007-003). Written informed consent.