ABSTRACT
IntroductionA cohort of COVID-19 convalescent volunteers allowed the study of neutralizing (nAb) and ligand antibodies kinetics by providing sequential samples during a median of 100 days after onset of disease. Material and MethodsA cohort of previously RT-PCR+ve (detected by nasopharyngeal swab during the acute phase), male convalescent patients, all with mild symptoms, were enrolled on serial blood sample collection for evaluation of longitudinal nAb titers and anti-nucleocapsid (NP) antibodies (IgM, IgG and IgA). Nabs were detected by a cytopathic effect-based virus neutralization test (CPE-based VNT), carried out with SARS-CoV-2 (GenBank: MT350282) ResultsA total of 78 male volunteers provided 316 samples, spanning a total of 4820 days of study. Although only 25% of donors kept nAb titers [≥]160, after a median of 100 days after the onset of disease, there was a high probability of sustaining nAB titers [≥]160 in volunteers whose initial nAb titer was [≥]1280, weight [≥] 90kg or BMI classified as overweight or obese, evidenced by Kaplan-Meier estimates and Cox hazard regression. There was no correlation between ABO group, ABO antibody titers and persistent high nAb titers. High IgG anti-NP (S/CO [≥]5.0) is a good surrogate for detecting nAB [≥]160, defined by ROC curve (sensitivity = 90.5%; CI95% 84.5-94.7%) ConclusionSelection of CCP donors for multiple collections based on initial high nAb titers ([≥]1280) or overweight/obese (BMI) provides a simple strategy to achieve higher quality in CCP programs. High IgG anti-NP levels can also be used as surrogate markers for high nAb screening.
Subject(s)
COVID-19ABSTRACT
Scalable, cost-effective screening methods are an essential tool to control SARS-CoV-2 spread. We have developed a straight saliva-based, RNA extraction-free, RT-LAMP test that is comparable to current nasopharyngeal swab RT-PCR tests in both sensitivity and specificity. Using a 2-step readout of fluorescence and melting-point curve analysis, the test is scalable to more than 30,000 tests per day with average turnaround time of less than 3 hours. The test was validated using samples from 244 symptomatic patients, and showed sensitivity of 78.9% (vs. 85.5% for nasopharyngeal swabs RT-PCR) and specificity of 100% (vs. 100% for nasopharyngeal swabs RT-PCR). Our method is therefore accurate, robust, time and cost effective and therefore can be used for screening of SARS-CoV-2.