Standardised quantitative assays for anti-SARS-CoV-2 immune response used in vaccine clinical trials by the CEPI Centralized Laboratory Network: a qualification analysis
Authors: Mark Manak, Luc Gagnon, Steven Phay-Tran, Philipa Levesque-Damphousse, Aymeric Fabie, Matthieu Daugan, Sarwat Tahsin Khan, Pamela Proud, Bethan Hussey, Daniel Knott, Sue Charlton, Bassam Hallis, Guruprasad R Medigeshi, Neha Garg, Anbalagan Anantharaj, Rubhana Raqib, Protim Sarker, Mohammad Mamun Alam, Mustafizur Rahman, Marta Murreddu, Angela Balgobind, Rick Hofman, Silvia Grappi, Rosa Coluccio, Pierpaolo Calandro, Emanuele Montomoli, Giada Mattiuzzo, Sandra Prior, Yann Le Duff, Mark Page, Jane Mitchell, Lauren M Schwartz, Yannic C Bartsch, Ali Azizi, Valentina Bernasconi, Vijay Zala, Ana Paula De Almeida, Helen Fassoulas, Tanvi Agrawal, Janmejay Singh, Anjan Kumar Roy, Saskia Berndsen, Marina de Mooij, Hester Buitendijk, Coen Stalpers, Modou Jarju, Filippo Battistella, Rienk Jeeninga, Danny Duijsings, Ilaria Razzano, Eleonora Molesti, Livia Mazzini, Adele Boccuto, Angela Holder, Edward Mee, Matthew Hurley, Jennifer Padley, Nicola Rose, Trina Gorman, Jose Vila-Belda, Hannah James, Jerome Carless
Journal: The Lancet Microbe (2024)

BackgroundAccurate quantitation of immune markers is crucial for ensuring reliable assessment of vaccine efficacy against infectious diseases. This study was designed to confirm standardised performance of SARS-CoV-2 assays used to evaluate COVID-19 vaccine candidates at the initial seven laboratories (in North America, Europe, and Asia) of the Coalition for Epidemic Preparedness Innovations (CEPI) Centralized Laboratory Network (CLN).MethodsThree ELISAs (pre-spike protein, receptor binding domain, and nucleocapsid), a microneutralisation assay (MNA), a pseudotyped virus-based neutralisation assay (PNA), and an IFN-γ T-cell ELISpot assay were developed, validated or qualified, and transferred to participating laboratories. Immune responses were measured in ELISA laboratory units (ELU) for ELISA, 50% neuralisation dilution (ND50) for MNA, 50% neutralisation titre (NT50) for PNA, and spot-forming units for the ELISpot assay. Replicate assay results of well characterised panels and controls of blood samples from individuals with or without SARS-CoV-2 infection were evaluated by geometric mean ratios, standard deviation, linear regression, and Spearman correlation analysis for consistency, accuracy, and linearity of quantitative measurements across all laboratories.FindingsHigh reproducibility of results across all laboratories was demonstrated, with interlaboratory precision of 4·1–7·7% coefficient of variation for all three ELISAs, 3·8–19·5% for PNA, and 17·1–24·1% for MNA, over a linear range of 11–30 760 ELU per mL for the three ELISAs, 14–7876 NT50 per mL for PNA, and 21–25 587 ND50 per mL for MNA. The MNA was also adapted for detection of neutralising antibodies against the major SARS-CoV-2 variants of concern. The results of PNA and MNA (r=0·864) and of ELISA and PNA (r=0·928) were highly correlated. The IFN-γ ELISpot interlaboratory variability was 15·9–49·9% coefficient of variation. Sensitivity and specificity were close to 100% for all assays.InterpretationThe CEPI CLN provides accurate quantitation of anti-SARS-CoV-2 immune response across laboratories to allow direct comparisons of different vaccine formulations in different geographical areas. Lessons learned from this programme will serve as a model for faster responses to future pandemic threats and roll-out of effective vaccines.FundingCEPI.