engleski

ESTABLISHMENT OF METHODOLOGY FOR COVID-19 CONVALESCENT PLASMA COLLECTION AND TESTING AT CROATIAN INSTITUTE of TRANSFUSION MEDICINE

BACKGROUND: Passive immunotherapy is the century- old practice of administering antibodies from an exposed convalescent or vaccinated person to a patient susceptible to the disease in question. Experience from prior outbreaks with other coronaviruses (SARS-CoV-1) shows that such convalescent sera contain neutralizing antibodies (NAb) against relevant virus and that their use was beneficial in the treated patients. Collection of COVID-19 convalescent plasma (CCP) at Croatian Institute of Transfusion Medicine (CITM) started in July 2020 and first unit for clinical use was issued in December. Clinicians in Croatia started using CCP in second wave of pandemics, mostly for patients with haematological malignancies. Such patients are not able to fight the SARS-CoV-2 infection by producing their own antibodies. CCP with individually checked levels of NAb, as an external source of antibodies, showed promising results in improving condition of these patients during SARS-CoV-2 infection. AIMS: To present the establishment of relevant methodology to properly evaluate SARS-CoV-2 neutralization capacity testing and to assess the correlation of donor disease severity and demographic characteristics with antibody titre level. METHODS: Each donor had a documented history of laboratory-confirmed SARS- CoV-2 infection. All plasma was donated by recovered and healthy COVID- 19 patients and collected by apheresis. In the beginning of the collection, titre of NAb was measured with the SARS-CoV-2 neutralization assay for quantification of SARS-CoV-2 NAb on Vero E6 cell suspensions and with home working stocks of SARS-CoV-2 virus prepared from a clinical isolate of the Laboratory working stock label SARS-CoV-2 297/20 Zagreb virus. In the meantime, the regression analysis for Vidas SARS-CoV-2 IgG test was done. This resulted in high correlation coefficient with neutralization assay and the regression equation has been used for the estimation of cut-off NAb level. High titre was determined as ED50/ml ≥ 1200. Data were collected from national transfusion IT system (e-Delphyn) and CCP donor checklist. Chi-squared, Kruskal- Wallis and Mann- Whitney tests were performed in MedCalc software for statistical analysis. RESULTS: We collected data for donations during the eight months period (28th July 2020 to 28th March 2021). 256 CCP units have been collected from 162 apheresis procedures. The donors’ age median was 36 (18-62) years. 30.4 % procedures were collected from women. The NAb median level of CCP for clinical use was 2560 (274 - 145, 218). The most common blood type was A (43%), followed by O (33%), B (12%) and AB (12%). COVID-19 symptoms in donors varied: asymptomatic (2.5%), mild (75%), medium (19.4%) and severe (3.1%). 75.4% of all donations had high NAb titre. Titre level did not statistically differ between genders (P = 0.262, Z = 1.12), severity of symptoms (P = 0.072, χ2 = 6.99) nor blood types (P = 0.842, χ2 = 0.83). Severity of disease did not statistically differ between genders (P = 0.23, χ2 = 4.26) nor blood types (P = 0.803, χ2 = 5.34). SUMMARY/CONCLUSIONS: 3/4 of collected CCP had high NAb titre. In rare cases, when the CCP supplies were scarce, physicians required issuing of CCP with lower titres. NAb titre was not dependent on gender, symptom severity nor blood type. Application of serological test performed in CITM highly correlated with the neutralization assay and allowed quicker issuing of CCP for clinical use which is very important for due time therapy of COVID-19 patients.

Covid 19 - concvaescent plasma, neutralization assay

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