NIV develops ELISA test to detect coronavirus antibodies

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In a first, NIV Pune has developed an ELISA test to detect IgG antibodies that are developed in response to infection by novel coronavirus. The ELISA test, to be manufactured by Zydus Cadila, will be used for testing the blood samples of 30,000 people in 75 hotspot districts.

The Pune-based National Institute of Virology has developed an immunological assay – enzyme-linked immunosorbent assay (ELISA) – to detect antibodies that the body develops in response to infection by the novel coronavirus (SARS-CoV-2), according to an official source. The test will detect IgG antibodies present in blood samples. ELISA is routinely used for detecting HIV infection.

“This kit was validated at two sites in Mumbai and has high sensitivity and accuracy. Besides, it has the advantage of testing 90 samples together in a single run of 2.5 hours,” Dr. Harsh Vardhan tweeted. He also tweeted saying that NIV has transferred the technology to Zydus Cadila for mass-scale production. The Drug Controller General has granted commercial production and marketing permission to Zydus Cadila. The Health Minister,  however, did not reveal how sensitive and specific the test is.

This is the first time India has developed an indigenous ELISA test for coronavirus. While ELISA tests for coronavirus are already available in other countries, procuring them in large numbers may be a challenge, particularly during a pandemic. In contrast, availability will be a non-issue when a locally developed test is manufactured in India.

The company that has been licensed to manufacture the ELISA test will have about a month to make the tests available as collection of blood samples from 30,000 people in 75 hotspot districts will begin by the third week of May.

Dr. Balram Bhargava, Director-General of the Indian Council of Medical Research was not reachable for comments.

The ELISA test developed by NIV gains significance as the rapid antibody tests imported from China were found to be unreliable and hence States were instructed not to use them for detecting previous coronavirus infection.

The 30,000 samples collected randomly from the general population in the 75 hotspot districts and tested using the ELISA will help understand the extent of spread of the virus in the community. India has thus far maintained that there is no community transmission despite there being nearly 67,000 cases so far from across the country.

Since the ELISA test is based on detection of antibodies, it can only help in knowing if the person has been previously infected by coronavirus. It will not be able to indicate if the person is currently infected. However, since it detects antibodies, even people who have remained symptom-free (asymptomatic) during the entire course of the infection will test positive. However, according to the Centers for Disease Control and Prevention (CDC), it takes one-three weeks for the antibodies to develop in response to infection. So, if a person who has been recently infected by the virus is tested during the window period (the time taken to develop antibodies) the result will turn out to be negative. But a repeat test after a couple of weeks will indicate the true infection status.

While the RT-PCR, which detects the RNA of the coronavirus, enables detection of current infection, it will not be useful if the testing is carried out days after the infection clears as the virus will no longer be present. However, antibodies developed in response to the coronavirus infection will be present in the blood for a longer duration and hence the ELISA test can help detect past infection. The maximum time the antibodies will be present is not known for coronavirus.

Published in The Hindu on May 10, 2020