Convalescent plasma - Is it useful for treating SARS Co-V2 infection?

Abstract

The world is challenged with the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) pandemic. Although preventive measures such as social distancing, personal protective equipment and isolation would decrease the spread of the infection, a definitive treatment is still under way. Antivirals, immunisation, convalescent plasma (CP) and many more modalities are under trial, and there has been no definite answer to the management of COVID-19 infection. All patients so far have received the standard and symptomatic care. It is shown that the SARS-CoV 2 is a respiratory pathogen, and 80% of the infected patients would recover from the illness and it is the 20% of the infected patients require hospitalisation and even critical care. CP has been used to treat recent epidemic respiratory infections such as Middle East respiratory syndrome and severe acute respiratory syndrome (SARS) infections with promising results. The CP of a recovered individual contains antibodies which neutralise the virus and decrease the viral replication in the patient. It is a classic adaptive immunotherapy and has been applied in the prevention and treatment of many infectious diseases. CP is plasma taken from a person who has recovered from an infection, which contains neutralising antibodies against the said infection. Giving CP to susceptible individuals or infected patients is a form of passive antibody therapy and in the case of SARS-CoV-2, is expected to provide protection by viral neutralisation and antibody-dependent cytotoxicity and phagocytosis. The adaptive response is to a specific antigen-binding array of molecules that are foreign to the host. The human response to viruses uses both the innate and the adaptive arms in its attempt to rid the host of the invading pathogen. The humoral response is a component of the adaptive immune response that allows for antibodies to bind to foreign invading pathogens, marks the pathogens and their toxins for phagocytosis and recruits further phagocytic cells to the site via the activation of the complement system and eventually prevents the pathogen from infecting target cells. Studies from Wuhan from various institutions during the research on COVID-19 infections during December 2019 have also shown promising results. Till date, randomised controlled studies for the use of CP in SARS-CoV-2 infection are lacking, and many countries have invited institutions to participate in clinical trials. The Indian Council of Medical research and the Central Drugs Standard Control Organisation, Government of India, have allowed the use of CP as an investigational drug under a trial basis. Internationally, agencies such as the USFDA, American Association of Blood Banks, European Blood Safety and British Blood Transfusion Society have also come out with various guidelines for the use of CP in COVID-19 infection. This article will review the current guidelines for the use of CP and compare the various guidelines of different agencies.

Keywords: Convalescent plasma; SARS-CoV-2; neutralising antibodies; plasmapheresis.