A new blood test provides essential information for revaccination plans for people who are vulnerable.

Researchers at Mount Sinai have created a blood test that determines the amount and duration of an individual’s immunity against SARS-CoV-2, the virus that causes COVID-19.

According to a June study published in Nature Biotechnology, this test will enable large-scale monitoring of the population’s immunity and the efficacy of current vaccines to assist devise revaccination programs for immunocompromised persons at risk.

The test can be done in less than 24 hours and can be used with a large number of people. It assesses the activation of T cells, which are part of our adaptive immune response to SARS-CoV-2 infection or vaccination and aid in the prevention of severe disease or death.

Ernesto Guccione, PhD, Professor of Oncological Sciences and Pharmacological Sciences at The Tisch Cancer Institute at Mount Sinai, remarked, “The assay we have created has the ability to measure the population’s cellular immunity and broadly test the efficacy of novel vaccines.”

As we already know that vulnerable populations may not always mount an antibody response, thus evaluating T cell activity is crucial for determining the true level of a person’s immunity.

Also, the emergence of SARS-CoV-2 variants like Omicron, which avoid most antibodies’ ability to neutralize them, shows the need for tests that can measure T cells, which are better at fighting new variants of concern.

Antibodies and the T-cell response work together to provide long-term protection against viral infection. Many recent studies have highlighted the need of evaluating T cell function in people who have recovered from COVID-19 or have been vaccinated against it in order to better plan immunization programs. However, due to the accompanying technical constraints, measuring T cell responses were rarely done before this work.

In this study, researchers from Mount Sinai and Duke-NUS Medical School collaborated to enhance qPCR-based assays that had the potential to be globally scalable, sensitive, and accurate. The researchers concentrated their efforts on the two assays with the best scalability.

The qTACT assay was accurate and sensitive, although it took a lengthy time to process 200 blood samples (24 hours), had a moderate price, and required a medium level of technical skill.

The dqTACT test, on the other hand, was accurate, had a shorter processing time and cost, and required little lab training, making it simple to use.

The dqTACT assay has just received European CE-IVD (in vitro diagnostics) certification, and clinical validation by the US Food and Drug Administration and the European Medicines Agency is currently underway.

“The assays presented here are based on the ability of SARS-CoV-2 T cells to respond to peptides covering different proteins of the virus,” added Jordi Ochando from Mount Sinai’s Icahn School of Medicine. “With the possibility of using different peptide pools, our approach represents a flexible strategy that can be easily implemented to detect the presence of T cells responding to different viral proteins. These T cells have an important role in protection from emerging mutant strains, thus immediately gauging the impact that viral mutations might have on cellular immunity .”

“Precise measurement of cellular responses underlying virus protection represents a crucial parameter of our levels of immune defense,” Megan Schwarz, a doctoral student at Icahn Mount Sinai and the study’s first author, added.

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