AUTHOR=Ravlić Sanda , Hećimović Ana , Kurtović Tihana , Ivančić Jelečki Jelena , Forčić Dubravko , Slović Anamarija , Kurolt Ivan Christian , Mačak Šafranko Željka , Mušlin Tatjana , Rnjak Dina , Jakšić Ozren , Sorić Ena , Džepina Gorana , Đaković Rode Oktavija , Kujavec Šljivac Kristina , Vuk Tomislav , Jukić Irena , Markotić Alemka , Halassy Beata TITLE=Is Better Standardization of Therapeutic Antibody Quality in Emerging Diseases Epidemics Possible? JOURNAL=Frontiers in Immunology VOLUME=Volume 13 - 2022 YEAR=2022 URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2022.816159 DOI=10.3389/fimmu.2022.816159 ISSN=1664-3224 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.