Convalescent plasma therapy (CPT) involves using antibodies from the blood of a person who has recovered from a virus and transfusing those antibodies into a person who is suffering from illness due to coronavirus in order to boost his/her immune system.
Significance of the Therapy in COVID-19 Cases
This treatment has acquired a lot of significance to check the outbreak of COVID-19 virus. Approved by the US Food and Drug Administration, it is an experimental treatment in clinical trials for severely ill COVID-19 patients. The therapy is being used in many parts of the world to treat COVID-19 patients. About 34 institutions are working in this direction. Those who suffered from the virus and are 21 days out from the onset of the first symptoms can donate plasma.
For treating COVID-19 patients, certain components from the blood of people who suffered from the COVID-19 infection and recovered are injected into people who are critically ill due to COVID-19 virus or people who belong to the high risk group of acquiring COVID-19 infection.
Mechanism of the Therapy
When a person gets infected with the COVID-19 virus, the immune system of that person responds by producing antibodies or proteins to kill the virus. Immune cells, called B lymphocytes, secrete such antibodies/proteins in plasma. Plasma is the liquid form of blood and aids in immunity and clotting of blood whenever needed. These antibodies remain in the blood of people who get infected and then recover from the virus. When these antibodies are injected into another person, infected with the virus, they recognise the virus and attack it. Same process takes place when antibodies are given to a corona virus infected person. These antibodies prohibit the virus from entering cells in the body by attacking the spikes on the outside of the coronavirus.
The process of using the antibodies of a person, who has recovered from a disease, to help another person suffering from the same disease is not a novel one. It has been in practice as far back as the 1980s. It was used for treating measles and mumps.
The convalescent serum of COVID-19, i.e., serum of individuals who have been cured of coronavirus has virus-neutralising antibodies and works as a passive antibody therapy. Plasma donated by one person can produce two doses of the required material for transfusions. According to scientists, one transfusion is sufficient for a person to acquire enough antibodies.
The donors of plasma must meet the following criteria—They must be 17 years old and weigh at least 110 lbs, must be in good health; must have undergone a prior diagnosis of COVID-19, meet specific laboratory criteria; and be symptom-free for at least 14 days.
Advantages of the Therapy
The therapy offers a convenient option in our healthcare system. It is not known to have any major side effects and can be easily transferred anywhere like a vaccine. Plasma therapy could have worked as a catalyst in speeding up recovery, but 100 per cent recovery cannot be attributed to plasma therapy due to multiple factors.
Collection of Plasma
Convalescent sera is collected in the following two ways:
(i) Using routine blood withdrawal followed by centrifuge technique. In this way, 180 ml – 200 ml of sera can be collected, which can be stored in – 60 °C up to one year.
(ii) Using cell separator machine, aphresis machine, up to 600 ml of convalescent sera can be collected at one time.
Therapeutic Plasma Exchange
Therapeutic plasma exchange involves the process of removal of abnormal substances from circulation, present either in plasma or tightly bound to plasma patients. In COVID-19 patients, the plasma will contain enormous inflamatory mediators, which cause severe lung injury.
Critical Review of the Therapy
Plasma therapy is being seen as a miracle cure for treating critically ill Covid-19 patients as the studies around the world are showing promising results. But, on the downside, the treatment is quite expensive and offers a limited scope for treating Corona patients as donation by one donor can make only two doses of the therapy.
Moreover, more research is needed in the field to ascertain the effectiveness of the therapy in an accurate way. As per the US Food and Drug Administration (USFDA), “It is not currently known if convalescent theraphy will be an effective treatment against COVID-19”. The union health ministry of India has also recommended to use the plasma therapy only as a trial and not as a regular line of treatment.