engleski

Establishing of prerequisites for the COVID-19 convalescent plasma usage in Croatia

In 2020, a worldwide spread of SARS-CoV-2 caused the global COVID-19 pandemic. Experience from previous outbreaks with other coronaviruses showed that convalescent sera contained neutralizing antibodies (NAbs) against the virus and that their use was beneficial to the treated patients. Although convalescent plasma therapy was considered generally beneficial, the scientific medical community lacks definitive proof of its efficacy coming from carefully designed clinical trials. The reasons for this can be found in its short-term usage only during epidemics caused by a new and insufficiently know pathogen, in a period when pathogen specific therapy and vaccines are lacking. During this period, methods for plasma neutralization potency determination are usually lacking or if they exist, they are neither standardized nor validated. All this results in the variability within different individual trials. Here we describe an approach of establishing antibody characterisation in emergent times which would, if followed, enable comparison of results from different studies. We established an assay of wild-type SARS-CoV-2 neutralisation, as the most relevant for antibody protectivity. To ensure the maximal reproducibility, we used a banking system of its biological components - a challenge virus, cells and an anti-SARS-CoV-2 antibody in-house standard, calibrated to the First WHO International Standard immediately upon its availability. Consequently, all collected serological data were retrospectively expressed in an internationally comparable way. The neutralising antibodies (NAbs) among convalescents ranged from 4 to 2869 IUmL-1, being in significant positive correlation to the disease severity. NAbs decline in convalescents was on average 1.4-fold in a one-month period. Heat-inactivation of sera samples resulted in a 2.3-fold decrease of NAb titres in comparison to the native sera, implying significant complement activating properties of SARS-CoV-2 specific antibodies. The monitoring of NAb titres in the sera of immunocompromised COVID-19 patients that lacked their own antibodies evidenced the successful transfusion of antibodies by the COVID-19 convalescent plasma units with NAb titres of 35 IUmL-1 or higher.

Covid19 ; Sars-CoV-2 Neutralization assay ; wild type virus

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