Convalescent plasma in Covid-19: Possible mechanisms of action

Abstract

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible of the coronavirus disease 2019 (COVID-19) pandemic. Therapeutic options including antimalarials, antivirals, and vaccines are under study. Meanwhile the current pandemic has called attention over old therapeutic tools to treat infectious diseases. Convalescent plasma (CP) constitutes the first option in the current situation, since it has been successfully used in other coronaviruses outbreaks. Herein, we discuss the possible mechanisms of action of CP and their repercussion in COVID-19 pathogenesis, including direct neutralization of the virus, control of an overactive immune system (i.e., cytokine storm, Th1/Th17 ratio, complement activation) and immunomodulation of a hypercoagulable state. All these benefits of CP are expected to be better achieved if used in non-critically hospitalized patients, in the hope of reducing morbidity and mortality.

Keywords: ACE-2 receptor; COVID-19; Convalescent plasma; Coronavirus; Cytokines; Intravenous immunoglobulins; Neutralizing antibodies; SARS-Cov-2.

Fig. 1

Schematic representation of convalescent plasma components and its mechanisms of action. A. Main convalescent plasma components. B. Antiviral effects of NAbs. IgG and IgM are the main isotypes, although IgA may be also important, particularly in mucosal viral infections. Other non-NAbs may exert a protective effect. The humoral immune response is mainly directed towards spike (S) protein. C. Anti-inflammatory effects of CP include network of autoantibodies and control of an overactive immune system (i.e., cytokine storm, Th1/Th17 ratio, complement activation and regulation of a hypercoagulable state) (see text for details). N: Nucleoprotein; M: Membrane; E: Envelope.