Context: Recently, the National Institute of Virology (NIV) has developed an immunological assay, Enzyme-linked Immunosorbent Assay (ELISA), to detect antibodies that the body develops in response to infection by the SARS-CoV-2 novel coronavirus.
Key Points

• ELISA is routinely used for detecting HIV infection. The test will detect IgG antibodies present in blood samples.
• NIV had transferred the technology to Zydus Cadila for mass-scale production subsequent to the Drug Controller General granting commercial production and marketing permission to Zydus Cadila.
• Since the ELISA test is based on detection of antibodies, it helps detect cases in which the infected person has remained symptom-free (asymptomatic) during the entire course of the infection.
• It will also help ascertain if the person was previously infected, which is not possible with the RT-PCR (reverse transcription polymerase chain reaction) test.
• The newly developed kit can test 90 samples together in a single run of 2.5 hours enabling faster testing.
• The ELISA test will be used to screen 30,000 samples from 75 hotspot districts to understand the extent of the spread of the virus in the community. This would help ascertain whether there is community transmission in India.
• 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 in the body is not known for coronavirus.

Its Importance

• 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. With the indigenous ELISA test kit, availability will be a non-issue.
• The ELISA test developed by NIV gains significance as the rapid antibody tests imported from China were found to be unreliable. The kit has reported high sensitivity and accuracy.

About Zydus Cadila

• It is headquartered in Ahmedabad, India, and ranks 4th in the Indian pharmaceutical industry. The group has manufacturing sites and research facilities spread across five states of Gujarat, Maharashtra, Goa, Himachal Pradesh and Sikkim in India and in the US and Brazil.