T-SPOT.COVID test uses ELISpot interferon-gamma

Long-term protection from infectious agents, such as the SARS-CoV-2 virus, is mediated by T cells and antibody-mediated immunity of the adaptive immune system (

). The T-SPOT.COVID test was developed to identify the presence of SARS-CoV-2-responsive T cells.

T cells contribute to the understanding of SARS-CoV-2 infections in many ways. T cells can identify past SARS-CoV-2 infections at a time when PCR tests would be negative and antibodies levels may be waning (

;

;

). T cells can provide immune memory lasting for months (

) and perhaps years, as suggested by the discovery of T cells to the SARS-CoV-1 coronavirus 17 years after infection (

). T cells may act independently of antibodies to control a SARS-CoV-2 infection, as shown by the recovery of COVID-19 patients who lack detectable antibodies but have SARS-CoV-2-responsive T cells (

;

). T cells also show reactivity to numerous SARS-CoV-2 epitopes, so have the potential to protect against many SARS-CoV-2 variants (

;

). T cell-based assays can probe the longevity of an immune response following a SARS-CoV-2 infection or vaccination (

;

;

). These various roles suggest that a T cell assay can be a key contributor to SARS-CoV-2 investigations.

The T-SPOT.COVID test, an enzyme-linked immunospot (ELISpot) assay, identifies T cells in peripheral blood that release interferon-gamma (IFN-γ) in response to stimulation with SARS-CoV-2 peptides. The T-SPOT.COVID test builds on the T-SPOT platform (Oxford Immunotec) used worldwide for tuberculosis and cytomegalovirus testing and the research version, the T-SPOT Discovery SARS-CoV-2 test (

• •
  TSPOT.COVID is an ELISpot interferon gamma-release assay for SARS-CoV-2
• •
  TSPOT.COVID identifies a T cell response to SARS-CoV-2 spike S1 and N peptides
• •
  2–8 weeks post SARS-CoV-2 diagnosis TSPOT.COVID detected 98% of infections
• •
  In comparison, immunoglobulin G (IgG) serology detected 83% of infections in the same period
• •
  Cellular immune response activated sooner and lasted longer than antibodies

Objective

Methods

Results

Conclusion

). The T-SPOT.COVID ELISpot methodology is performed in many laboratories and offers a standardized comparison of T cell immunity among participants. In addition, ELISpot assays normalize the number of peripheral blood mononuclear cells (PBMCs), thus maintaining test effectiveness in participants with lymphopenia, a commonly reported condition in many COVID-19 patients (

) and immunosuppressed people.