Context:

The Indian Council of Medical Research (ICMR) is framing a protocol for infusing blood plasma from people who have recovered from COVID-19 into patients in a serious condition. The procedure, known as convalescent plasma therapy, is carried out in the expectation that antibodies specific to the Novel Coronavirus that are present in the blood of the patient who has recovered will help generate immune response in the other patient.

Convalescent plasma therapy

This therapy seeks to make use of the antibodies developed in the recovered patient against the coronavirus.

  • Convalescent plasma therapy banks on the age-old concept of passive immunity when antibodies for some diseases, such as diphtheria, were developed in horses and injected into humans.
  • Active immunity is what is achieved by introducing an attenuated pathogen (such as the BCG vaccine) into the body to generate an immune response. The other kind of immunity is passive immunity.
  • Temporary immunity can be achieved in a person by infusing antibodies, activated T cells or both obtained from the blood of someone else or from some other animal that has been actively immunised against these antigens.
  • These antibodies last for two-three weeks and during that time, the person is protected against the invading disease.
  • A patient who has recovered from COVID-19 carries anti-bodies that can neutralize coronavirus,
  • The whole blood or plasma from such people is taken, and the plasma is then injected in critically ill patients so that the antibodies are transferred to fortify their immune system against the disease and boost their fight against the virus.
  • COVID-19 patient usually develops primary immunity against the virus in 10-14 days. Therefore, if the plasma is injected at an early stage, it can possibly help fight the virus and prevent severe illness.
Plasma is the matrix on which the blood cells float. It also houses crucial components of immunity known as antibodies.Antibodies fight an invading pathogen.

Once that is done, some blood cells function as memory cells so that they can identify and defeat the same enemy if and when it invades again by quickly producing the same antibodies.

Antibodies

  • Antibodies are proteins that are secreted by immune cells called B lymphocytes in 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.

Procedure

Convalescent plasma therapy involves transfusion of the blood plasma of a recovered patient into another patient.

  • The process to infuse plasma in a patient requires standard blood collection practices, and extraction of plasma.
  • If whole blood is donated (350-450 ml), a blood fractionation process is used to separate the plasma.
  • Otherwise, a special machine called aphaeresis machine can be used to extract the plasma directly from the donor.
  • The aphaeresis machine separates and extracts the plasma using a plasma kit, and the remaining blood components are returned into the donor’s body.

WHO Guidelines

  1. WHO guidelines in 2014 mandate a donor’s permission before extracting plasma.
  2. Plasma from only recovered patients must be taken, and donation must be done from people not infected with HIV, hepatitis, syphilis, or any infectious disease.
  3. If whole blood is collected, the plasma is separated by sedimentation or centrifugation, then injected in the patient.
  4. If plasma needs to be collected again from the same person, it must be done after 12 weeks of the first donation for males and 16 weeks for females

Indian Plan

  • The country’s apex medical research organisation, Indian Council of Medical Research (ICMR), is framing a protocol for infusing blood plasma from people who have recovered from COVID-19 into serious patients.
  • This will only be done by way of a clinical trial, in patients who are in a severe condition, or on ventilator.
  • In Kerala, some who had recovered from COVID-19 and they are ready to be part of the plasma therapy trial.
  • India has facilities for removing 500 ml of plasma from a donor using aphaeresis.
  • For this experimental therapy to be tried out, the Drug Controller General of India will first have to grant blood banks approval for removal of plasma from recovered COVID-19 patients.

Previous applications

  • The United States used plasma of recovered patients to treat patients of Spanish flu (1918-1920).
  • Hong Kong used it to treat SARS patients in 2005.
  • In 2009, H1N1 patients were treated with plasma. A study in Oxford University’s journal Clinical Infectious Diseases found that “convalescent plasma reduced respiratory tract viral load, serum cytokine response, and mortality” in H1N1 patients.
  • In 2014, the World Health Organization released guidelines to treat Ebola patients with convalescent whole blood and plasma.
  • The WHO observed that “convalescent plasma has been used successfully for the treatment of a variety of infectious agents” for which no treatment is available.
  • In 2015, plasma was used for treating MERS patients.

Recent application in Covid-19 cases in other countries

  • Two elderly South Korean patients recovered from severe pneumonia after being treated with plasma from coronavirus survivors.
  • The United States FDA has issued guidance to provide recommendations to health care providers and investigators on the administration and study of investigational convalescent plasma collected from individuals who have recovered from COVID-19 (COVID-19 convalescent plasma) during the public health emergency
  • In a study Chinese researchers reported about a pilot convalescent plasma therapy in 10 patients. They reported: “all symptoms in the 10 patients, especially fever, cough, shortness of breath, and chest pain, disappeared or largely improved within 1 d to 3 d upon CP transfusion.

Benefits from the therapy

COVID-19 does not have a specific treatment, only supportive care— including antiviral drugs, oxygen supply in mild cases and extracorporeal membrane oxygenation.

  • 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.

Limitation

  • 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.
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