LONGITUDINAL EVALUATION OF THE ANTI-NUCLEOCAPSID IGG AFTER THE CONFIRMED COVID-19 IN NORTHERN CROATIAN POPULATION

Abstract

BACKGROUND: This study longitudinally evaluated the IgG response against the N-protein after the onset of COVID19 infection. We determined the kinetics and magnitude of the antibody response against SARS-CoV-2 in con\uf001rmed\nCOVID-19 patients who were the \uf001rst infected with SARS-CoV-2 in Krapina-Zagorje county in northern Croatia.\nMATERIALS AND METHODS: We studied 177 blood specimens from 51 patients who tested positive by PCR for COVID-19 and provided\nlongitudinal blood samples over a duration of several months, allowing to evaluate the IgG response against the N-protein. SARS-CoV-2 IgG\nassay was interpreted as positive (ratio1.4 S/C) or negative (ratio<1.4 S/C).\nRESULTS: The majority of subjects (48/51) reported symptomatic disease. Among the 49 patients who underwent serological antibody testing\nat \uf001rst time point (median: 47 days), 47/49 were positive for IgG 6.02 (0.24-10.54 S/C), while at sixth time point (median: 275 days) 4/16 patients\nwere positive for IgG, 9/16 were in grey zone, and 3/16 were negative. Using Wilcoxon statistical analysis we found statistically signi\uf001cant\ndecrease of SARS-CoV-2 N-protein IgG indices between the \uf001rst and the sixth time point (median signal to cut-off ratio, S/C, 8.18 IQR 6.91, 9.51\nto 0.94 IQR 0.56, 1.18, P=0.001).\nCONCLUSIONS: We clari\uf001ed the kinetics and magnitude of the antibody response against SARS-CoV-2 in con\uf001rmed COVID-19 patients.\nOur results provide critical evidence that N-protein IgG response persists in the majority of patients for at least six to eight months after COVID19 infection.