Company insight T-cell response to Covid-19
While Covid-19 testing has been critical to controlling disease spread and directing treatment during the pandemic, conventional tests suffer from several limitations. With growing evidence for a robust and long-lasting response of T-cells to infection with SARS-CoV-2, Dr Tony Allen of Oxford Immunotec explains how T-cell tests can give clinicians a complete picture of an individual’s immune response and represent an important addition to the Covid-19 test panel.
T
-cell responses are reliable and robust. Although initially reported to be highly sensitive and specific, recent research has placed the sensitivity of PCR-based tests for SARS-CoV-2 infection as low as 70%. In addition, 10–30% of people infected with SARS-CoV-2 display no antibody response – meaning these individuals are missed by serology.
While the antibody response to SARS-
CoV-2 can vary between infected individuals, there is evidence that the T-cell response is more consistent. T-cells display robust and long-lasting responses to human coronaviruses, with some individuals infected 17 years ago with SARS-CoV-1 still displaying T-cell responses today. Studies that have measured transmission between family members also indicate that newly- infected individuals are 50% more likely to develop SARS-CoV-2-specific T-cells than antibodies following exposure.
Oxford Immunotec’s
T-SPOT.COVID kit components and box.
In contrast with antibody responses that may be delayed, T-cell responses are present soon after infection, with studies showing specific SARS-CoV-2 T-cell responses as early as four days after onset of symptoms. The ability to detect SARS-CoV-2 during the
“The
T-SPOT.COVID test can deliver a comprehensive view of an individual’s Covid-19 immune response when used in conjunction with current methods of PCR testing and serology, making it an important addition to the Covid-19 testing arsenal.”
A clearer picture
Greater understanding of the important role of T-cells in the Covid-19 immunity has led diagnostics companies to develop specific T-cell tests, which include the
T-SPOT.COVID test from Oxford Immunotec. Studies that have used this test show it to be highly sensitive – identifying 51% more PCR-positive individuals than serology alone. T-cell testing has demonstrated similar encouraging results in a recent Public Health England study, which showed that in a cohort of individuals previously infected with Covid- 19, 88.9% of those with negative serology still demonstrated robust T-cell responses.
Practical Patient Care /
www.practical-patient-care.com
early acute phase of infection means healthcare providers can better control disease transmission, and also contain disease outbreaks more effectively. Antibody responses decline steadily with time, meaning serology is not always able to determine whether an individual has been previously exposed to the virus. In contrast, SARS-CoV-2-specific T-cell responses have been observed six to nine months after infection, and are thought to last even longer. The long-lasting response of T-cells to SARS-CoV-2 infection mean that T-cell testing could inform important clinical decisions, such as the need for booster vaccinations, and help administrators make
decisions on staff placement based on individual Covid-19 immunity. There is also evidence that specific T-cell responses to SARS-CoV-2 are protective, and individuals with higher T-cell responses are at a lower risk of later reinfection. This is in agreement with studies in primates, which have shown that previously infected animals with depleted T-cells were unable to fight off reinfection, while those that retained their SARS-CoV-2 specific T-cells recovered successfully. T-cells are also thought to be important for the action of Covid-19 vaccines – with several different types of vaccine causing robust T-cell responses. T-cell testing can be both a
straightforward and rapid test, requiring a single blood draw via routine phlebotomy, and taking as little as two days to generate laboratory results. By enabling earlier detection of SARS-CoV-2 infection during the acute phase, as well as detection of past infections, T-cell tests – such as the
T-SPOT.COVID test – can deliver a comprehensive view of an individual’s Covid-19 immune response when used in conjunction with current methods of PCR testing and serology, making it an important addition to the Covid-19 testing arsenal. ●
www.oxfordimmunotec.com 21
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