Is Better Standardization of Therapeutic Antibody Quality in Emerging Diseases Epidemics Possible?

Abstract

During the ongoing COVID-19 epidemics many efforts have gone into the investigation of the SARS-CoV-2–specific antibodies as possible therapeutics. Currently, conclusions cannot be drawn due to lack of standardization in antibody assessments. Here we describe an approach of establishing antibody characterisation in emergent times, which enables, if followed, comparison of results from different studies. The key component is the reliable and reproducible assay of wild-type SARS-CoV-2 neutralisation, based on a banking system of its biological components - a challenge virus, cells and an anti-SARS-CoV-2 antibody in-house standard, which was calibrated to the First WHO International Standard immediately upon its availability, so all collected serological data were retrospectively expressed in internationally comparable way. Neutralising antibodies (NAbs) among convalescents ranged from 4 to 2869 IUmL-1 in significant positive correlation to the disease severity. Their decline in convalescents was on average 1.4-fold in one-month period. Heat-inactivation resulted in 2.3-fold decrease of NAb titres in comparison to native sera, implying significant complement activating properties of SARS-CoV-2 specific antibodies. Monitoring of NAb titres in sera of immunocompromised COVID-19 patients lacking their own antibodies, evidenced the successful transfusion of antibodies by COVID-19 convalescent plasma units, with NAb titres of 35 IUmL-1 or more.