Rapid SARS-CoV-2 T-Cell Test Reveals Full Picture of Body’s Immune Response to COVID-19

A growing body of data now demonstrates the importance of both T cells and antibodies in the coordinated immune response against SARS-CoV-2. This method is a further boost to scientists who seek to routinely monitor and assess SARS-CoV-2-specific T-cell responses in vaccinated or convalescent individuals, as well as to test and verify the effectiveness of vaccines.

For the study, the scientists took blood samples from volunteers who were vaccinated against COVID-19, or who had been infected and then recovered from the disease. They then introduced small fragments of the SARS-CoV-2 spike protein directly into the blood samples. In response to these fragments, the T cells released chemical signals called cytokines, which are much easier to detect and measure than T cells, and are already being tracked to monitor T-cell activity for the diagnosis of diseases such as tuberculosis.

Building on that, the team showed that the test, called Cytokine Release Assay (CRA), can reliably identify and quantify specific T cells present in the blood of people who have been vaccinated against COVID-19, or have recovered from SARS-CoV-2 infection. Working with different blood samples from more than 200 people, the researchers demonstrated that the CRA test was as sensitive as existing methods used to find and measure T-cell activity.

“T cells play a vital role alongside antibodies in protecting people against COVID-19, but they are much harder to detect and measure,” said Dr Anthony Tanoto Tan, Senior Research Fellow with Duke-NUS’ Emerging Infectious Diseases (EID) Program and first author of the study. “Our research offers a feasible approach that can overcome the current limitations faced in detecting spike-specific T-cell responses, and will help better evaluate the protective role played by T cells in our immune system.”

“This discovery allows a rapid and large-scale expansion of studies to track T-cell activity across the world, while not requiring specialized or expensive equipment,” said Professor Antonio Bertoletti from Duke-NUS’ EID program, the study’s corresponding author. “The study results confirm that the level of antibodies against SARS-CoV-2 in blood samples does not always correlate with the T-cell response. With this rapid test, we can help define the correlates of protection from T cells and antibodies for the development of COVID-19 vaccines.”

“This important study advances our understanding of the human body’s immune response at a critical juncture in this pandemic,” added Professor Patrick Casey, Senior Vice-Dean for Research at Duke-NUS. “As validated in this research, repurposing the well-established CRA test to fast-track the evaluation of T-cell responses in COVID-inoculated or -convalescent patients adds a new dimension to vaccine strategies as we battle the threat of new and emergent variants.”


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