The novel test aims to assess cellular immunity, which can complement serosurveys, help to better triage patients and set a framework for a sensible vaccination program

Bengaluru-based doctors Dr Sonal Asthana, Hepatobiliary and Transplant Surgeon, Aster CMI Hospital and Dr Vishnu Kurpad, Consultant Surgical Oncologist, Sri Shankara Cancer Hospital have jointly developed India’s first-ever test to examine specific T Cell immunity for Covid-19.

CoVID affects people in different ways. Most of the affected patients develop mild symptoms, while a relatively small number patients require intensive medical care. Immunity plays important role in the body’s response to SARS CoV-2 infection. It is now understood that apart from antibody response, a strong T cell response can help in conferring protective immunity to CoVID infection. Most tests focus on serology, which relies on antibody production after CoVID infection. However, some affected people do not develop antibodies, while antibody levels can reduce significantly after 6-8 weeks of infection. There is no simple ready-to-use test for cellular immunity that can complement diagnostic and prognostic tools in clinical use.

Dr Asthana & Dr Kurpad, said “We have devised a novel, simple, in-tube assay for the assessment of specific T cell immune responses to stimulation by SARS CoV-2 proteins. Traditional tests for T cell immunity require complex processing to separate different cells from blood samples and use technology that is not readily available. This test can be done with a small sample of whole blood.   Our solution simplifies the testing process which can be done at smaller labs without specialised equipment. The blood doesn’t require any special treatment. The results can be obtained in 24 hours, by measuring chemical called cytokines. A positive reading indicates good specific cellular immunity.”

They further added, “The blood samples from 3 patterns of people- recovered, moderate and severe individuals with Covid 19 infection were analysed at Anand Labs as an initial pilot study by a team that included Dr. Ananth Vikas and Dr Samrat Bordoloi. The outcome showed that recovered individuals have high levels of cellular immunity as compared to hospitalised patients. Our robust, easily deployable assay for cellular immunity strengthens our understanding of COVID-19 immune responses.  We are in the process of applying for a patent for this assay. Further development of this test would include testing virus sequences specific to India and matched to Indian populations, along with Dr Nagasuma Chandra from Indian Institute of Science, Bengaluru, who has been part of the group.”

The use areas of the test include:

• To complement serological surveys– Antibody responses are not produced by all patients who develop CoVID, and do not persist beyond 8 weeks in most people. The use of serological tests for screening will underestimate the number of people who have specific viral immunity. This test could complement serological surveys and provide a better picture of the prevalence of the disease and residual immunity.

• To triage CoVID positive patients based on prognosis: Strong cytotoxic T cell responses are linked with a milder clinical course. Patients who test CoVID positive can be assessed for and triaged based on cellular immunity- strong elicited responses are linked to better recovery.

• A companion test to a vaccine program:Vaccines need to be prioritised to a vulnerable group of people initially. Patients who are antibody negative and have low cellular immunity could be triaged to receive the vaccine early on.