Comparison of two T-cell assays to evaluate T-cell responses to SARS-CoV-2 following vaccination in naïve and convalescent healthcare workers


Clinical & Experimental Immunology

Contributing to research themes:

T-cell responses to SARS-CoV-2 following infection and vaccination are less characterized than antibody responses, due to a more complex experimental pathway. We measured T-cell responses in 108 healthcare workers (HCWs) using the commercialized Oxford Immunotec T-SPOT Discovery SARS-CoV-2 assay service (OI T-SPOT) and the PITCH ELISpot protocol established for academic research settings. Both assays detected T-cell responses to SARS-CoV-2 spike, membrane, and nucleocapsid proteins. Responses were significantly lower when reported by OI T-SPOT than by PITCH ELISpot. Four weeks after two doses of either Pfizer/BioNTech BNT162b or ChAdOx1 nCoV-19 AZD1222 vaccine, the responder rate was 63% for OI T-SPOT Panels 1 + 2 (peptides representing SARS-CoV-2 spike protein excluding regions present in seasonal coronaviruses), 69% for OI T-SPOT Panel 14 (peptides representing the entire SARS-CoV-2 spike), and 94% for the PITCH ELISpot total spike. The two OI T-SPOT panels correlated strongly with each other showing that either readout quantifies spike-specific T-cell responses, although the correlation between the OI T-SPOT panels and the PITCH ELISpot total spike was moderate. The standardization, relative scalability, and longer interval between blood acquisition and processing are advantages of the commercial OI T-SPOT assay. However, the OI T-SPOT assay measures T-cell responses at a significantly lower magnitude compared to the PITCH ELISpot assay, detecting T-cell responses in a lower proportion of vaccinees. This has implications for the reporting of low-level T-cell responses that may be observed in patient populations and for the assessment of T-cell durability after vaccination.


Author list:


  1. Peter Medawar Building for Pathogen Research, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
  2. Oxford University Hospitals NHS Foundation Trust, John Radcliffe Hospital, Oxford, UK
  3. NIHR Health Protection Research Unit in Emerging and Zoonotic Infections, Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, UK
  4. Translational Gastroenterology Unit, University of Oxford, Oxford, UK
  5. Nuffield Department of Clinical Neuroscience, University of Oxford, UK
  6. Big Data Institute, University of Oxford, Oxford, UK
  7. Radcliffe Department of Medicine, University of Oxford, Oxford, UK
  8. Oxford Centre for Global Health Research, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
  9. Oxford Vaccine Group, Department of Paediatrics, University of Oxford, Oxford, UK
  10. NIHR Oxford Biomedical Research Centre, University of Oxford, Oxford, UK
  11. UK Health Security Agency, Porton Down, UK
  12. Tropical and Infectious Disease Unit, Liverpool University Hospitals NHS Foundation Trust, member of Liverpool Health Partners, Liverpool, UK
  13. Mahidol-Oxford Tropical Medicine Research Unit, Bangkok, Thailand


Eloise Phillips1, Sandra Adele1, Tom Malone1, Alexandra Deeks1,2, Lizzie Stafford2,
Susan L. Dobson3, Ali Amini2,4, Donal Skelly2,5, David Eyre2,6, Katie Jeffery2,7,
Christopher P. Conlon2,8, Christina Dold9,10, Ashley Otter11, Silvia D’Arcangelo11, Lance Turtle3,12, PITCH Consortium, Paul Klenerman1,2,4,10, Eleanor Barnes1,2,4,10, and Susanna J. Dunachie1,2,8,13