Two elderly South Korean patients recovered from severe pneumonia after being treated with plasma from coronavirus survivors. Sumi Sukanya Dutta explains what is plasma therapy, the principle that governs it and what lies ahead as the fight against the COVID-19 contagion continues
Although a specific treatment for COVID-19 is still a far cry, an experiment in plasma therapy in South Korea has offered hope. Although there is limited evidence on this line of treatment from China, the US and some other countries, scientists have pointed out the potential benefits of plasma — a blood fluid — from patients who have recovered, prompting clinical trials to assess its efficacy.
What is plasma therapy?
Convalescent plasma therapy involves transfusing specific components from the blood of people who have recovered from COVID 19 — at least 14 days after their complete recovery — into people who are severely ill with the infection or people who are at a high risk of contracting the virus.
How does the therapy work?
As a patient’s body grapples with SARS CoV 2, they produce antibodies to attack the virus. Those antibodies — proteins that are secreted by immune cells called B lymphocytes — are found in plasma or the liquid part of blood that helps in clotting when needed and supports immunity. Even after a person who has recovered from COVID-19, these antibodies or “memory cells” stay in their blood waiting to fight the same virus in case there is a recurrence of the infection. These antibodies, when injected into another person with the disease, recognise the virus as “enemies” and kills it. In the case of the novel coronavirus, scientists estimate that antibodies attack the spikes on the outside of the virus, blocking the virus from penetrating human cells and replicating.
What is an antibody?
Antibodies are proteins produced by the immune system that help defend a person against foreign invasion. When a host is challenged by foreign material (bacteria, virus, toxins, etc.) the first response of the body’s immune cells, called macrophages, is to engulf these invaders (antigens) and process them biochemically. This biochemical processing essentially creates a blueprint that is used for the development of an immune response that results in the production of antibodies. Each antibody can bind to only one specific antigen. The purpose of this binding is to help destroy the antigen. Some antibodies destroy antigens directly. Others make it easier for white blood cells to destroy the antigen.
Who can benefit from the therapy?
Scientists are estimating that convalescent plasma can be effective in treating people with the most severe symptoms of the virus. It is also being hoped that those moderately sick from the infection can be helped from deteriorating if treated with plasma therapy.
Is there a limitation to the therapy?
Convalescent plasma is also known as passive antibody therapy. It means that the injected antibodies last only for a short time in the recipient’s body even though they can immediately provide a person with the ability to fight the virus. Researchers’ hopes are pinned on the body’s own ability to develop their defence against the virus. However, in the case of the donor, the antibodies are long-term. There is no conclusive evidence yet but some virologists have said that once infected and recovered, COVID -19 patients will never get the disease again.
How many patients can be helped by one plasma donor?
So far, it has been seen that one person’s donation of plasma can produce two doses of blood component needed for transfusions. It has also been estimated that a person only needs one transfusion to get enough antibodies to fight a virus.
Has plasma therapy been tried on COVID-19 patients in India?
No. The treatment protocol is for very sick COVID-19 patients in India and includes a combination of anti-malaria drug Hydroxychloroquine and antibiotic Azithromycin as of now. The 21-member task force on managing COVID-19 outbreak, however, is considering directing the Indian Council of Medical Research to come up with a protocol for introducing the therapy in India in patients severely ill with the virus.
WATCH | Cure for COVID-19? Here's all you need to know about blood plasma therapy