ABSTRACT
Convalescent plasma to treat coronavirus disease 2019 (COVID-19) is currently the focus of numerous clinical trials worldwide, but the criteria of treatment efficacy remain largely unknown. Here, we describe a severely immunosuppressed patient following rituximab and chemotherapy for chronic lymphoid leukemia, who became infected by SARS-CoV-2. His prolonged viral disease was successfully cured after four cycles of convalescent plasma. Its immunomodulatory properties led to the rapid improvement of inflammation, pneumonia and blood cell counts, already after the first cycle. Importantly, the cumulative increase in anti-SARS-CoV-2 neutralizing antibodies following each plasma transfusion was associated to progressive viral clearance, resulting in clinical recovery from infection. Our data provide insight into the different modes of action of plasma components. Understanding the underlying mechanisms will help to optimize the treatment of COVID-19 patients.