Anti-CD20 therapy is used to treat autoimmune and hematological diseases. An absent or delayed antibody response against SARS-CoV-2 puts patients at risk for a protracted and severe disease course. These patients may benefit from antibody-based therapy of which convalescent plasma (ConvP) is the most broadly available source.
ConvP from donors with SARS-CoV-2 antibody titers was used when their plaque reduction neutralization test (PRNT50) showed a PRNT50 titer of at least 1:160. When PRNT50 results were not yet available, an in-house RBD ELISA was used to select the donors with the 10% highest titers. Preceding and following transfusion, SARS-CoV-2 antibodies were measured (Wantai Ig SARS-CoV-2 RBD antibodies and PRNT50). All but 6 patients received 2 units of 300mL of ConvP. Two non-responders received a second 2x300ml transfusion while 5 patients were successfully treated with only 300ml ConvP.
22 B-cell depleted patients admitted with COVID-19 were treated with ConvP. B-cell depletion was the result of Rituximab (n=19), Obinutuzumab (n=1), XLA (n=1) or Blinatumomab (n=1) for lymphoma, auto-immune disease or ALL. Patients had been sick for a median of 26 days (IQR 18 – 34.5 days) and all were SARS-CoV-2 RBD antibody negative on the day of transfusion. The plasma units had a median PRNT50 titer of 1:640 (IQR 1:160 – 1:1280). 19 of 22 patients showed clear clinical improvement after transfusion and could be discharged from the hospital. 3 patients died of which 1 had treatment refractory extensive idiopathic pulmonary fibrosis preceding COVID-19. All patients seroconverted to a median total Wantai Ig OD ratio of 18.39 (IQR 11.245 – 18.41), Figure 1. PRNT50 titers increased from <1:20 preceding transfusion to 1:40 (IQR 1:20 – 1:80) after transfusion. One patient quickly recovered clinically after transfusion but it took 10 weeks to become PCR negative.
Prompt clinical and virological recovery after ConvP transfusion was observed in the large majority of B-cell depleted antibody negative patients admitted with COVID-19. Our observation shows that for carefully selected patients, antibody-based therapy can be effective. After transfusion of 600mL of ConvP, all patients had seroconverted to high anti-RBD antibody titers and detectable PRNT50 titers of 1:20 or higher. Based on these observations, we suggest an initial dose of 600mL of ConvP.
