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Could Reactive T-Cell Testing be An Alternative to Standard COVID-19 Tests?
The mainstream COVID-19 diagnosis and vaccine development in the pharmaceutical industry focuses mainly on antibodies against SAR-CoV-2. However, Oxford Immunotec approaches COVID-19 with an unorthodox regimen, a diagnostic assay for SARS-CoV-2 reactive T cells. Recently published data from the EDSAB-HOME study that used Oxford Immunotec’s T-Spot Discovery SARS-CoV-2 assay demonstrated that SARS-CoV-2 reactive T cells are associated with protection from COVID-19. Specifically, individuals with higher T cell responses show no symptoms of COVID-19, while those with lower T cell responses do. The finding also explains why the elderly are more vulnerable to the virus as reactive T cell levels decrease with age.
The role of T cells in COVID-19 infection is beginning to be understood, and T cells are more challenging to be measured than antibodies. However, recent evidence suggests that reactive T cells are linked to COVID-19 immunity. For example, Pfizer and BioNTech’s vaccine candidate vaccines that displayed 90% efficacy showed a strong T cell reactivity. If no further findings contradict the current hypothesis, Oxford Immunotec’s diagnostic assay could be used to address the uncertainties on community-based mass antibody testing to detect previous infections.
Phill Keefe, Senior Vice President Product Design, Development and Delivery at Oxford Immunotec, expressed, “not everyone with COVID-19 infection has detectable antibodies in serology tests, and this may be a bigger problem in the majority who experience only mild or no symptoms. Also, it is not yet clear whether the presence of antibodies confers immunity. T cells responses develop before antibody generation and can independently provide protection, so studying T cells could give us new insights into immunity to COVID-19.” Serology tests indicate whether an individual has been infected with COVID-19 based on the presence (seropositive) or absence (seronegative) of antibodies developed in one’s body.
T-SPOT Technology
Oxford Immunotec has been an expert in T cell measurement for over 15 years since the introduction of its proprietary T-SPOT technology in the field of tuberculosis. The technology incorporated and modified the classic ELISPOT technique to measure and standardize T cell immune responses effectively. It has currently obtained regulatory approval for clinical diagnostic use in over 50 countries, including the U.S., European Union, Japan, and China.
Oxford Immunotec’s CEO, Dr. Peter Wrighton-Smith, said, “Our T-SPOT technology platform is the only globally regulated ELISPOT [(Enzyme-Linked ImmunoSpot)] platform currently available, and we are pleased that we may be able to use it to support efforts to combat COVID-19. Our collaboration with Public Health England is a great example of the public and private sector working together. The successful outcomes of this study would not have been possible without the specialist skills and resources available within Public Health England.” ELISPOT assays provide data on cell-mediated immunity for regulated immune monitoring studies for biologics, gene therapies, and cell therapies.
EDSAB-HOME Trial
In collaboration with Public Health England (PHE), Oxford Immunotec enrolled 2826 participants working in hospitals, the fire, and police departments who have higher risks of COVID-19 exposure in England from June 2020 to mid-October with a median of 118 days. All enrollees were assessed for their SARS-CoV-2 reactive T cells by T-SPOT kit as well as their antibodies triggered by the virus using either Roche’s Elecsys anti-SARS-CoV-2 test or Euroimmun’s anti-S IgG immunoassay.
According to the data, no participants with high levels of reactive T cells to the coronavirus’s spike, nuclear and membrane proteins developed symptomatic COVID-19 infection. Still, those with low reactive T cells were confirmed infectious. Surprisingly, in all confirmed cases, a total of 20 individuals had seronegative, which corroborated Keefe’s concern over the presence of T cells as a protection against the virus.
Nevertheless, the findings still cannot substantiate that testing for reactive T cells is more accurate than antibody testing because the tests could be misleading. In other words, individuals who tested seronegative but with high reactive T cells may be exposed to other viruses that cause the common cold. Besides, a four-month-long study involving fewer than 3,000 participants in just one country is not conclusive enough that reactive T cells confer immunity to COVID-19.
By Judy Ya-Hsuan Lin
Editor: Rajaneesh K. Gopinath. Ph.D.
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