Evaluation of QuantiFERON SARS-CoV-2 interferon-γ release assay following SARS-CoV-2 infection and vaccination

Background T cells are important in preventing severe disease from SARS-CoV-2, but scalable and field-adaptable alternatives to expert T cell assays are needed. The interferon-gamma release assay QuantiFERON platform was developed to detect T cell responses to SARS-CoV-2 from whole blood with relatively basic equipment and flexibility of processing timelines. Methods 48 participants with different infection and vaccination backgrounds were recruited. Whole blood samples were analysed using the QuantiFERON SARS-CoV-2 assay in parallel with the well-established ‘Protective Immunity from T Cells in Healthcare workers’ (PITCH) ELISpot, which can evaluate spike-specific T cell responses. Aims The primary aims of this cross-sectional observational cohort study were to establish if the QuantiFERON SARS-Co-V-2 assay could discern differences between specified groups and to assess the sensitivity of the assay compared to the PITCH ELISpot. Findings The QuantiFERON SARS-CoV-2 distinguished acutely infected individuals (12-21 days post positive PCR) from naïve individuals (p< 0.0001) with 100% sensitivity and specificity for SARS-CoV-2 T cells, whilst the PITCH ELISpot had reduced sensitivity (62.5%) for the acute infection group. Sensitivity with QuantiFERON for previous infection was 12.5% (172-444 days post positive test) and was inferior to the PITCH ELISpot (75%). Although the QuantiFERON assay could discern differences between unvaccinated and vaccinated individuals (55-166 days since second vaccination), the latter also had reduced sensitivity (55.5%) compared to the PITCH ELISpot (66.6%). Conclusion The QuantiFERON SARS-CoV-2 assay showed potential as a T cell evaluation tool soon after SARS-CoV-2 infection but has lower sensitivity for use in reliable evaluation of vaccination or more distant infection. Graphical abstract With the exception of acute infection group, the PITCH ELISpot S1+S2 had greater sensitivity for SARS-CoV-2 specific T cell responses compared with the QuantiFERON SARS-CoV-2 assay tube Ag3. ![Figure][1] ### Competing Interest Statement S.J.D declares fees as a Scientific Advisor to the Scottish Parliament on COVID-19. No other competing interests declared. ### Funding Statement This work was funded by the UK Department of Health and Social Care as part of the PITCH (Protective Immunity from T cells to Covid-19 in Health workers) Consortium, with contributions from the National Core Study: Immunity (NCSi4P programme, Optimal cellular assays for SARS-CoV-2 T cell, B cell and innate immunity, UKRI through the UK Coronavirus Immunology Consortium (UK-CIC), the Huo Family Foundation, The National Institute for Health Research (UKRIDHSC COVID-19 Rapid Response Rolling Call, Grant Reference Number COV19-RECPLAS) and U.S. Food and Drug Administration Medical Countermeasures Initiative contract 75F40120C00085. E.B. and P.K. are NIHR Senior Investigators and P.K. is funded by WT109965MA. S.J.D. is funded by an NIHR Global Research Professorship (NIHR300791). D.S. is supported by the NIHR Academic Clinical Lecturer programme in Oxford. The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR, the Department of Health and Social Care or UKHSA or the US Food and Drug Administration. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Informed consent was obtained under one of two studies: The GI Biobank Study 16/YH/0247, approved by the research ethics committee (REC) at Yorkshire & The Humber - Sheffield Research Ethics Committee on 29 July 2016, which had been amended for this purpose on 8 June 2020 or the Family Study R71346/RE001, approved by Oxford University Medical Sciences Inter-Divisional REC (MS-IDREC-R71346/RE00). 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