Methods
Study population, setting, and data collection: Sixteen seronegative controls and a total of 125 in-patients individuals were recruited, following informed consent, for the study from the COVID Care Centres associated with BYL Nair hospital and T N medical college, Municipal Corporation of Greater Mumbai (MCGM), Mumbai following approval of institutional ethics committees. We obtained demographic data, clinical history at presentation, and laboratory results during admission.
Blood samples for the study were handled in accordance with ICMR guidelines for biosafety. 1-3ml of whole blood was collected in EDTA vacutainers. Aliquots of whole blood were processed for absolute cell count and immunophenotyping as described below. Plasma was separated by centrifugation at 400 g for 10 minutes. IgG and IgM antibodies against SARS-CoV-2 were detected in fresh plasma samples using Rapid test from Voxpress (Voxtur Bio LTD, India) and Chemiluminescence immunoassay (CLIA) directed against SARS -CoV-2 anti-NC IgG. Remaining plasma samples were aliquoted and stored at -800 C until batch analysis of cytokines, LPS (Lipopolysaccharide) and Soluble MAdCAM (sMAdCAM).