A newly-developed test can measure both the T-cell and antibody response to SARS-CoV-2 in a single blood sample.

The unique approach developed by scientists at Cardiff University (Cardiff, UK) in collaboration with biotechnology company ImmunoServ Ltd. (Wales, UK), can also be used to measure the immune response brought about by vaccination and previous infection. Antibody testing was seen as crucial to easing lockdown during the pandemic – but antibodies are just one arm of the body’s immune response and in some individuals this response is weak and short-lived. Scientists believe T-cell immunity plays a much greater role in protecting people from future infection, however large-scale testing has proven more challenging.

In their study, the researchers took a small sample of blood from individuals of all ages, 68 with underlying cancer and 231 healthy donors. They stimulated T-cells with small pieces of the virus called peptides; the T-cells recognize these peptides if the individual has been previously infected (or vaccinated) and produce chemicals named cytokines which can be easily measured. The study also monitored the size of the T-cell and antibody responses in a group of individuals tested before, during and after the UK’s COVID-19 vaccination campaign. While both vaccine doses were required to maximize the T-cell response against the virus, the study found previously infected individuals required only one dose to achieve comparable immune responses.

The test proved most useful in monitoring immune responses in patients considered more at risk from COVID-19, even after vaccination. The study found the second vaccine dose was essential for cancer patients. Among cancer patients recruited for the study, two doses induced T-cell and antibody responses to equivalent levels as healthy donors. However, it is clear that in some cancer patients there is a dramatic fall of in immune responses at three months, not seen in healthy controls, and highlights the importance of monitoring these responses. The research team will now also monitor whether T-cell and antibody responses induced by vaccination can protect against SARS-CoV-2 mutant variants, including the Delta variant.

“COVID-19 infection rates remain alarmingly high – and it is clear infection even after vaccination is an issue. To help control future outbreaks and identify at-risk individuals, it is important to understand the exact make-up of the immune response to COVID. Our test accurately detects both the T-cell and antibody response to the virus in one blood sample. Together these indicators represent a powerful measure of immunity from COVID-19,” said Dr. Martin Scurr, a research associate at Cardiff University’s School of Medicine and lead author on the study. “The test can be made widely available, is easy to employ and cost effective, and should play a very useful role in monitoring this pandemic, for instance by identifying individuals at greater need of booster jabs.” 

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