Tu15 - Elevated anti-PEG Antibody Levels Amongst Covid-19 Vaccinated Donors

Beginning in early 2021, without any change to our flow cytometry antibody products, we observed an increase in the number of donors showing unusual non-specific staining of lymphocytes and granulocytes.  This unusual staining pattern was limited to workflows where antibody staining was performed in whole blood, using Pegylated (PEG) fluorophore antibody conjugates.  Not all the donors tested showed this staining pattern and some of them had been previously tested and did not exhibit this aberrant staining pattern.  The only difference we could identify was most if not all of our donors recently received the COVID-19 vaccine.  Since PEG is a component of some COVID-19 vaccine, we assayed the Plasma samples from 70 donors for the presence of anti-PEG antibody using a commercially available ELISA kit assay. Comparing with normal-staining donors, we observed elevated anti-PEG antibodies in the plasma of those donors with aberrant staining. All the donors who had elevated anti-PEG antibodies had received a Covid-19 vaccine.   All non-specific staining can be corrected by pre-washing blood or adding PEG in blood. Further study should be conducted to address this finding.