Convalescent plasma: one of the forgotten immunologically based strategies
Passive immunization has been successfully used to treat infectious diseases. A meta-analysis demonstrated a significant reduction in mortality and viral load in studies using convalescent plasma for the treatment of severe acute viral respiratory infections, including those caused by related coronaviruses (SARS-CoV and MERS-CoV) [5]. Serious adverse events were not reported. Eighty SARS patients were treated with convalescent plasma during the last major outbreak. A significantly better outcome was obtained with earlier transfusion (before day 14), and no immediate adverse events were observed.
A feasibility intervention study of convalescent plasma for MERS-CoV infection treatment failed to identify sufficient high-titer plasma from patients with confirmed/suspected MERS, their close family members, or healthcare workers exposed to MERS (n = 12 reactive ELISA/443 serum tested). Two fresh-frozen plasma units (250–350 mL/unit) would be required for each enrolled MERS patient (NCT02190799). Encouragingly, anti-MERS CoV titers measured by ELISA correlated with microneutralization (MN) assays [6].
There are currently over 30,000 recovered COVID-19 patients, who could present a valuable resource of convalescent plasma for health care providers. China National Biotec Group Co has claimed that 10 seriously ill patients receiving this immunoglobulin therapy demonstrated improved oxygenation and reduced inflammation and viral load [7]. High-titer specific antibodies should be able to bind to SARS-CoV-2 and neutralize the viral particles, block access to uninfected cells, and activate potent effector mechanisms (e.g., complement activation and phagocytosis).