Re: Covid-19: Where are we on immunity and vaccines?
We read with great interest the recent article by Elisabeth Mahase, titled: ‘Covid-19: Where are we on immunity and vaccines?’(1) - especially as evidence on the importance of SARS-CoV-2 T cells is emerging fast.
The piece mentions a comment by Professor Maini suggesting that current commercially available interferon gamma release assay (IGRAs) that are used to assess TB infection status may be adapted to assess T-cell response to SARS-CoV-2 infection. However, Prof. Maini also stated that the use of T-cells as an additional marker for prior infection is a long way from reality. However, Oxford Immunotec Ltd have already developed a commercially available, research use only, kit, T-SPOT® Discovery™ SARS-CoV-2, to measure T cell responses in subjects previously infected with SARS-CoV-2 virus.
This kit is based on the same technological ELISPOT platform as our T-SPOT.TB test that has been approved for clinical use to detect tuberculosis infection in over 50 countries including the US, Europe, China, and Japan and of which over 20 million tests have been used in healthcare.
This test was used in a recent, as yet unpublished, cross sectional study of 2,500 frontline workers, conducted to examine the SARS-CoV-2 antibody and T cell response in those reporting previous illness compatible with the COVID-19 clinical condition (some confirmed by polymerase chain reaction and others with only the clinical syndrome) and in those with no such history of infection. Initial study results suggest that the T-SPOT® Discovery™ SARS-CoV-2 Research Use Only (RUO) kit is able to identify T cell responses in the vast majority of infected patients. Moreover, some patients who were infected, but antibody negative demonstrated robust T-cell responses as identified by the T-SPOT® Discovery™ SARS-CoV-2 Kit.
Potential Use of the T-SPOT Discovery kit:
As has been shown, antibody titres to SARS-CoV-2 may decay over time leading to a potential inability of tests to identify those previously infected (2,3). This may be important in the future with the possibility of the much vaunted ‘immune passport’. The T-cell assay may also be of benefit in identifying an appropriate humoral immune response to a vaccine candidate during at the development stage. However, perhaps a less obvious use would be to help confirm the ‘previously uninfected’ status of vaccine trial participants thus not enrolling potentially immune subjects into the placebo arm of a trial thus eliminating a potential source of selection bias.
The current commercial availability of a ‘research use only’ SARS-CoV-2 T-cell test should allow a more widespread assessment of the humoral response to this virus, especially in the situation where the antibody response may be more transient.
1. Mahase E. Covid-19: Where are we on immunity and vaccines? BMJ [Internet]. 2020 Aug 5 [cited 2020 Aug 17];370. Available from: https://www.bmj.com/content/370/bmj.m3096
2. Altmann DM, Boyton RJ. SARS-CoV-2 T cell immunity: Specificity, function, durability, and role in protection. Sci Immunol. 2020 Jul 17;5(49):eabd6160.
3. Ibarrondo FJ, Fulcher JA, Goodman-Meza D, Elliott J, Hofmann C, Hausner MA, et al. Rapid Decay of Anti–SARS-CoV-2 Antibodies in Persons with Mild Covid-19. N Engl J Med. 2020 Jul 21;0(0):null.
Competing interests: No competing interests