Analysis of Neutralization Antibodies in Patients With Mild COVID-19 Infection After 100 Days Using Microneutralization Test

Abstract

Neutralizing antibodies play a critical role in blocking viral infections and in viral clearanceduring acute infection. The microneutralization assay and enzyme-linked immunosorbentassay (ELISA) targeting the receptor binding domain were performed for 30 patients withmild coronavirus disease (COVID)-19 infections. The elapsed number of days between samplecollection and diagnosis was 115 days, and real-time polymerase chain reaction (PCR) cyclethreshold (Ct) values at diagnosis were recorded. Clinical characteristics and Ct values werecompared between neutralization antibody-positive and -negative patients as measured bythe microneutralization assay. Neutralization antibody-positive patients (n = 9) were likelyto be older, have low Ct values, have more pneumonia during admission, and have a higheroptical density in ELISA than the neutralization antibody-negative patients (n = 21). Elderlypeople seemed to have a higher viral load causing more pneumonia and to produce moreneutralization antibodies. Neutralization antibodies persisted in only 30% of patients asdetected by microneutralization test after 100 days of diagnosis.