Convalescent plasma therapy

 Convalescent plasma therapy

Tribhuvan University Teaching Hospital in Kathmandu has used plasma therapy for the treatment of a coronavirus infected person, for the first time in the country.

The hospital’s Covid-19 Management Coordinator Dr Santa Kumar Das says a blood plasma of the 26-year-old who recently got free of coronavirus has been given to a 65-year-old patient’s body to kill coronavirus in him also. Convalescent plasma therapy is commonly called plasma therapy. It is widely heard word during recent corona virus period but its use in medical treatment has a long history.

The use of convalescent plasma is not a new concept. It has been used since the 1800s. The first trial was done in 1892 for treating diphtheria (a severe infection of the nose and throat) using blood serum initially. Serum is the fluid and solute component of blood which does not play a role in clotting. It may be defined as blood plasma without fibrinogens. It was produced from animals who were infected with diphtheria, but soon whole blood or plasma recovered from donors with specific humeral immunity were identified as a possible source of specific antibodies of human origin. In the 1920s, it was used to treat scarlet fever (a bacterial illness that develops in people having strep throat). It was also used to treat pertussis (a highly contagious respiratory disease) until about 1970.

During the Spanish influenza pandemic of 1918, convalescent plasma was used as a potential therapy with mixed results. It has been used in a variety of viral infections that includes measles, mumps, Argentine hemorrhagic fever, influenza, chickenpox, infections by cytomegalovirus, parvovirus B19 and, more recently, Middle East Respiratory Syndrome coronavirus (MERS-CoV), H1N1 and H5N1 avian flu, Ebola, and Severe Acute Respiratory Infections (SARI) viruses.

We all know that human blood is red in colour. It is because of the presence of red coloured pigment called haemoglobin.  Human blood is composed of 45% blood cells which include RBC, WBC and platelets and 55% blood plasma.  Plasma is a light yellow liquid which contains water, salts and enzymes. The main role of plasma is to take nutrients, hormones, and proteins to the parts of the body that need it. Cells also put their waste products into the plasma. The plasma then helps remove this waste from the body through excretory system of our body. Blood plasma also carries all parts of the blood through your circulatory system and maintains pH of the blood.

Along with water, salt, and enzymes, plasma also contains important components. The proteins and antibodies in plasma are also used in therapies for rare chronic conditions. These include autoimmune disorders and hemophilia. People with these conditions can live long and productive lives because of the treatments. In fact, some health organizations call plasma "the gift of life."

Antibodies are the proteins that are produced against any antigen. Antigens are the parts of body of foreign invaders such virus, bacteria or protozoa. They are also called pathogens. When a person is infected by any virus or bacteria, his/her immune system is capable of generating antibodies which can kill those virus or bacteria.

Two types of antibodies are produced in the blood called IgM (immunoglobulin M) and IgG (immunoglobulin G). They are found in the blood plasma. Immunoglobulin M (IgM) is one of several isotypes of antibody (also known as immunoglobulin) that are produced by vertebrates. IgM is the largest antibody, and it is the first antibody to appear in the response to initial exposure to an antigen. In the case of humans and other mammals that have been studied, the spleen, where plasmablasts responsible for antibody production reside, is the major site of specific IgM production.

IgG is the antibody that are produced after the production of antibody IgM which are produced after few more days of infection. IgG are produced against the corona virus. These antibodies start fighting against corona virus antigen and kill them. Slowly and gradually, the patient starts feeling well and can recovered within few days. After being recovered, the body still have high concentration of IgM and IgG. The person at this stage is said to be immune to the corona virus. The body is now capable of fighting against those virus or noval coronavirus. If the same person is infected by the virus again, he/she is capable of recover within 3-4 days with very mild symptoms or without any symptoms.

In the treatment process of convalescent plasma therapy in the recovered person is used as a donor while the patient suffering from COVID-19 is used as a recipient. A donor is the person whose antibodies are used to kill corona virus in a person suffering covid-19. Recipient is a person who takes antibodies from the donor's blood.

It can be separated from whole blood by the process of centrifugation, i.e., spinning whole blood with an anticoagulant in a centrifuge. Plasma is lighter, so it forms the upper yellowish layer, while the denser blood cells fall to the bottom. The plasma collected is frozen within 24 hours to preserve the functionality of the various clotting factors and immunoglobulins; it is thawed before use and has a shelf life of 1 year.

Plasma, like whole blood, is initially tested, to ensure the safety of recipients. As per the FDA (Food and Drugs Administration) regulations, the collected plasma undergoes a battery of tests to identify transmittable diseases, mainly hepatitis A, B, and C along with syphilis and HIV. The process of fractionation separates individual plasma proteins.

How does it work:  If a patient suffering from severe COVID-19 and his immune system is not producing sufficient quantity of immunoglobulin or antibodies, it may be fatal to the patient as his/her immune system cannot battle with coronavirus. In such cases, plasma containing sufficient amount of IgM and IgG is given to the person so that these protein can combat coronavirus and may recovered. Thus, convalescent plasma therapy could be the alternative solution to cure COVID-19 patient and control spread of coronavirus. For, this process of treatment, large mass of people who have been recovered are required.