Antibody & Other Treatments for COVID-19

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TOPIC: General Studies 2

• Global crisis – COVID-19

In News: The Israeli Defence Minister has mentioned that scientists at the country’s main biological research institute have made a “significant breakthrough” in developing an antibody to the novel coronavirus, as the researchers wrapped up the development phase and moved to patent and mass produce the potential treatment. 

A statement said that the antibody’s development had been completed and that the institute was in the process of patenting the find “and in the next stage, researchers will approach international companies to produce the antibody on a commercial scale”. 

What will an antibody test do?

It’s possible to catch SARS-CoV-2, the new coronavirus, and not know it. That’s because not everyone infected with the virus has symptoms. But there’s a fast blood test that may tell you if you’ve ever been infected. It’s called an antibody test.

Also known as serology test, it looks for certain things called antibodies in your blood. Your body makes these when it fights an infection, like COVID-19. The same thing happens when you get a vaccine, like a flu shot. That’s how you develop immunity to a virus.

Antibody is a protein produced by the immune system in response to invading organisms such as bacteria and viruses. Antibodies are able to specifically recognize foreign invaders in the body, coat them by binding to them and then allow the immune cells of the body to clear them from the blood or mucous membranes, or sites like the lung.

The antibody test isn’t checking for the virus itself. Instead, it looks to see whether your immune system — your body’s defense against illness — has responded to the infection.

What exactly do we check for in the antibody test?

Doctors test for two kinds of antibodies to SARS-CoV-2. They look for:

• Immunoglobulin M, or IgM antibodies, which develop early in an infection – its presence would mean that the person is currently infected or very recently became infected
• Immunoglobulin G, or IgG antibodies, which are more likely to show up later after you’ve recovered

It takes your body about 4 weeks to develop IgM antibodies. But scientists aren’t sure how long it’ll take for this to happen with SARS-CoV-2. How long will that immunity last? Do people who had mild or no symptoms gain the same protection? Will the virus mutate to overcome the body’s immunity?

How can a test really be usable?

For a test to be usable, the specificity should be close to 100%. If, for example, 5% of the population have had Covid-19, a test with only 90% specificity would mistakenly assess 95 people in a sample of 1000 individuals as having had the virus, ie nearly 70% of the positive results would be false.

The majority of current antibody tests target the spike protein. This is the sole protein on the viral surface responsible for entry into the host cell, and so the main part of the virus that elicits antibody responses. However, the amino acid structure of the spike protein has a 60% overlap with the four seasonal coronaviruses that circulate in humans. Targeting the wrong site on this protein means an antibody test is unable to distinguish between people who have had Covid-19 and those who have had the common cold.

How is it going to help?

Show how common COVID-19 is or how sick it makes most people. And they can study what happens if people who’ve had it are exposed to it again. When paired with other scientific information, this can help researchers understand who might be immune to the virus. The hope is that policymakers will be able to obtain accurate models of how far the epidemic has spread, and what the real infection tallies are, a topic that has become increasingly heated in recent weeks. 

These tests may also help with an experimental treatment for COVID-19 called convalescent plasma. Plasma is the liquid part of your blood. Researchers are studying how antibodies in plasma donated by people who’ve recovered from COVID-19 might help those who are ill with the virus. One theory is that this plasma may help sick people get better faster. But more research is needed.

Acquiring accurate antibody data will also be vital for vaccine developers to verify that their products are working as intended during clinical trials. Results from sero-surveys will eventually help tell us whether exposure to Covid-19 provides immunity, or if we will face seasonal waves of infections. They may assist in determining the importance of pre-existing immunity. 

Scientists have already wondered whether the differences in fatalities between various countries is due to certain populations having had greater exposure to similar viruses in the past. But to gather truly reliable information, the antibody tests used must be shown to have a high degree of accuracy, something that has so far proven to be easier said than done.

INDIA: ELISA-based Antibody Test and How it Will be Used to Check Community Spread

The Centre announced that an IgG ELISA test for detection of antibodies to Covid-19 had been developed, and released a document outlining details of surveillance to be carried out in all districts to check for the prevalence of infection using the same.

Pune-based National Institute of Virology has developed an immunological assay — enzyme-linked immunosorbent assay (ELISA) — that can detect antibodies that are developed in response to the coronavirus infection. This the first test of the kind to be developed in India and it will play a critical role in surveillance of proportion of the population exposed to the virus.

ELISA-based tests are blood-based tests, which have high sensitivity and specificity. The sensitivity of a test refers to the percentage of results that will correctly find out the presence of infection in a person and specificity refers to the percentage of results that will correctly find out whether or not a person is infected. It has a sensitivity of 92% and its specificity is 97%.

• The test involves drawing the blood of the person. 
• The sample is then placed inside the small wells of an ELISA plate. These plates are coated with the antigen or the inactivated form of the virus. 
• If the blood contains antibodies, it binds to the antigen and a substrate solution is added to the well. The reaction usually produces a colour change, thus detecting antibodies. 
• ELISA tests can be done manually or in a semi-automatic and automatic way.

It is an IgG Elisa-based test. This means that the test will be done to detect the Immunoglobulin G (IgG) antibody.

Note: ELISA-based tests and point-of-care tests are not used for confirming Covid-19 infection and are only used for surveillance purpose.

Connecting the Dots:

1. The lessons of past infectious disease outbreaks have shown us that rushing large-scale epidemiological projects is inadvisable. Discuss.
2. Essay:

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