B-072 Analysis of Anti-SARS-Cov-2 S1-RBD and N IgG in Saliva and Serum

Abstract

Abstract Background Mucosal antibody testing may be a significant and more practical tool for measuring humoral immunity since it is non-invasive. The aim of this study was to evaluate the SARS-CoV-2-specific antibody prevalence in saliva compared to serum in 2022. Methods From February to December 2022, the paired serum and saliva specimens were collected twice over a period. The saliva specimens were collected using a Salivette Cortisol (Sarstedt AG & Co. KG, Germany) device according to manufacturers’ instructions. Antibody tests were performed using nucleocapsid protein-based Elecsys anti-SARS-CoV-2 (anti-N IgG) and spike protein targeted SARS-CoV-2 IgG II Quant (anti-S1-RBD IgG). Results 162 (97.6%) of 166 had anti-S1-RBD IgG in their serum. At the 1st visit and 2nd visit, 79 (47.5%) and 97 (58.4%) patients, respectively, had anti-N IgG in their serum. At 1st visit and 2nd visit, respectively, 14 (8.4%) and 13 (7.8%) patients had anti-S1-RBD IgG in their saliva. Four (2.4%) and five (3.0%) patients had anti-N IgG in their saliva during the 1st visit and 2nd visit, respectively. The correlation coefficient of the results of anti-S1-RBD IgG and anti-N IgG quantitative results between at 1st visit and 2nd visit were low (r = 0.1721 to 0.6448). All patients in the anti-S1-RBD IgG seronegative group (N = 4) had anti-N IgG in their serum, but neither anti-S1-RBD IgG nor anti-N IgG were detected in their saliva. All anti-N IgG seronegative patients (N = 68) had anti-S1-RBD IgG in serum, while 3 patients had anti-S1-RBD IgG and 7 patients had anti-N IgG in saliva. Conclusion Mucosal antibodies were detected in certain seronegative patients. The assessment of SARS-CoV-2-specific saliva antibodies should be regarded as a supplemental non-invasive diagnostic to serum to evaluate the prevalence and transmission of COVID-19.