With a vaccine for Covid-19 still a long way off, experts in India & USA US will now test if blood from coronavirus patients who have recovered could hold the key to treating the sick. Kerala is set to become the first state in the country to commence convalescent plasma therapy, which uses antibodies from the blood of cured patients, to treat critically ill COVID-19 cases on a trial basis. The Indian Council of Medical Research (ICMR) has given its nod to the first of its kind project. This is an important development as there is no tried and tested anti-viral drug or vaccine against the novel coronavirus yet.

A study of 10 patients in China who have undergone convalescent therapy showed a shortening of the duration of symptoms, improve oxygen levels and a drop in the “virus load” or the amount of virus in a person’s body. With a vaccine likely months to a year away, scientists hope that convalescent plasma therapy can help those sickest with the virus now.

History:

This passive-antibody therapy has been used since the 1890s to combat diseases as wide-ranging as measles, SARS, Ebola, H1N1 flu, and polio—and holds the promise of keeping the virus at bay until a vaccine can be developed. During the SARS outbreak in 2002–2003, an 80-person trial of convalescent serum in Hong Kong found that people treated with it within two weeks of showing symptoms had a higher chance of being discharged from hospital than did those who weren't treated.

What is plasma? What is its composition?

Blood plasma is a yellowish liquid component of blood that holds the blood cells in whole blood in suspension. It is the liquid part of the blood that carries cells and proteins throughout the body. It makes up about 55% of the body's total blood volume. It is the intravascular fluid part of extracellular fluid (all body fluid outside cells).

Composition: It is mostly water (up to 95% by volume), and contains important dissolved proteins (6–8%) (e.g. serum albumins, globulins, and fibrinogen), glucose, clotting factors, electrolytes (Na⁺, Ca²⁺, Mg²⁺, HCO₃⁻, Cl⁻, etc.), hormones, carbon dioxide (plasma being the main medium for excretory product transportation), and oxygen.

Role: It plays a vital role in an intravascular osmotic effect that keeps electrolyte concentration balanced and protects the body from infection and other blood disorders.

What is convalescent plasma therapy?

Convalescent plasma therapy involves transfusing certain components from the blood of people who have had the COVID-19 virus and recovered into people who are very sick with the virus or people who are at high risk of getting the virus.

How does it work?

As people fight the COVID-19 virus, they produce antibodies that attack the virus. Those antibodies, proteins that are secreted by immune cells known as B lymphocytes, are found in plasma, or the liquid part of blood that helps the blood to clot when needed and supports immunity.

Once a person has had the virus and recovered, that person has developed antibodies that will stay in their blood waiting to fight the same virus should it return. Those antibodies, when injected into another person with the disease, recognize the virus as something to attack.

In the case of the coronavirus, scientists say antibodies attack the spikes on the outside of the virus, blocking the virus from penetrating human cells.

Who would it help?

Researchers hope that convalescent plasma will be effective in treating people with the most severe symptoms of the virus. Additionally, it is hoped that it can keep those people who are not as sick from COVID-19 from getting any sicker. Convalescent plasma is also known as passive antibody therapy, meaning that while it can immediately provide a person with antibodies to fight a virus, those antibodies only last a short period of time in the recipient’s body. Doctors hope the antibodies can fight back the virus until a person develops their own defenses.