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Toft CJ, Stocks BB, Schaeffer PM. Comparison of the analytical sensitivity of COVID-19 rapid antigen tests in Australia and Canada. Talanta 2024; 275:126147. [PMID: 38677170 DOI: 10.1016/j.talanta.2024.126147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Revised: 04/18/2024] [Accepted: 04/22/2024] [Indexed: 04/29/2024]
Abstract
Rapid testing has become an indispensable strategy to identify the most infectious individuals and prevent the transmission of SARS-CoV-2 in vulnerable populations. As such, COVID-19 rapid antigen tests (RATs) are being manufactured faster than ever yet lack relevant comparative analyses required to inform on absolute analytical sensitivity and performance, limiting end-user ability to accurately compare brands for decision making. To date, more than 1000 different COVID-19 RATs are commercially available in the world, most of which detect the viral nucleocapsid protein (NP). Here, we examine and compare the analytical sensitivity of 26 RATs that are readily available in Canada and/or Australia using two NP reference materials (RMs) - a fluorescent NP-GFP expressed in bacterial cells and NCAP-1 produced in a mammalian expression system. Both RMs generate highly comparable results within each RAT, indicating minimal bias due to differing expression systems and final buffer compositions. However, we demonstrate orders of magnitude differences in analytical sensitivities among distinct RATs, and find little correlation with the median tissue culture infectious dose (TCID50) assay values reported by manufacturers. In addition, two COVID-19/Influenza A&B combination RATs were evaluated with influenza A NP-GFP. Finally, important logistics considerations are discussed regarding the robustness, ease of international shipping and safe use of these reference proteins. Taken together, our data highlight the need for and practicality of readily available, reliable reference proteins for end-users that will ensure that manufacturers maintain batch-to-batch quality and accuracy of RATs. They will aid international public health and government agencies, as well as health and aged care facilities to reliably benchmark and select the best RATs to curb transmission of future SARS-CoV-2 and influenza outbreaks.
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Affiliation(s)
- Casey J Toft
- College of Public Health, Medical and Veterinary Sciences, James Cook University, Douglas, Queensland, Australia
| | - Bradley B Stocks
- Metrology, National Research Council Canada, 1200 Montreal Road, Ottawa, Ontario, K1A 0R6, Canada.
| | - Patrick M Schaeffer
- College of Public Health, Medical and Veterinary Sciences, James Cook University, Douglas, Queensland, Australia.
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Stocks BB, Thibeault MP, L'Abbé D, Umer M, Liu Y, Stuible M, Durocher Y, Melanson JE. Characterization of biotinylated human ACE2 and SARS-CoV-2 Omicron BA.4/5 spike protein reference materials. Anal Bioanal Chem 2024:10.1007/s00216-024-05413-7. [PMID: 38942955 DOI: 10.1007/s00216-024-05413-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Revised: 06/14/2024] [Accepted: 06/18/2024] [Indexed: 06/30/2024]
Abstract
Accurate diagnostic and serology assays are required for the continued management of the COVID-19 pandemic yet spike protein mutations and intellectual property concerns with antigens and antibodies used in various test kits render comparability assessments difficult. As the use of common, well-characterized reagents can help address this lack of standardization, the National Research Council Canada has produced two protein reference materials (RMs) for use in SARS-CoV-2 serology assays: biotinylated human angiotensin-converting enzyme 2 RM, ACE2-1, and SARS-CoV-2 Omicron BA.4/5 spike protein RM, OMIC-1. Reference values were assigned through a combination of amino acid analysis via isotope dilution liquid chromatography tandem mass spectrometry following acid hydrolysis, and ultraviolet-visible (UV-Vis) spectrophotometry at 280 nm. Vial-to-vial homogeneity was established using UV-Vis measurements, and protein oligomeric status, monitored by size exclusion liquid chromatography (LC-SEC), was used to evaluate transportation, storage, and freeze-thaw stabilities. The molar protein concentration in ACE2-1 was 25.3 ± 1.7 µmol L-1 (k = 2, 95% CI) and consisted almost exclusively (98%) of monomeric ACE2, while OMIC-1 contained 5.4 ± 0.5 µmol L-1 (k = 2) spike protein in a mostly (82%) trimeric form. Glycoprotein molar mass determination by LC-SEC with multi-angle light scattering detection facilitated calculation of corresponding mass concentrations. To confirm protein functionality, the binding of OMIC-1 to immobilized ACE2-1 was investigated with surface plasmon resonance and the resulting dissociation constant, KD ~ 4.4 nM, was consistent with literature values.
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Affiliation(s)
- Bradley B Stocks
- Metrology, National Research Council Canada, 1200 Montreal Road, Ottawa, ON, K1A 0R6, Canada.
| | - Marie-Pier Thibeault
- Metrology, National Research Council Canada, 1200 Montreal Road, Ottawa, ON, K1A 0R6, Canada
| | - Denis L'Abbé
- Human Health Therapeutics, National Research Council Canada, 6100 Royalmount Avenue, Montreal, QC, H4P 2R2, Canada
| | - Muhammad Umer
- Metrology, National Research Council Canada, 1200 Montreal Road, Ottawa, ON, K1A 0R6, Canada
| | - Yali Liu
- Human Health Therapeutics, National Research Council Canada, 6100 Royalmount Avenue, Montreal, QC, H4P 2R2, Canada
| | - Matthew Stuible
- Human Health Therapeutics, National Research Council Canada, 6100 Royalmount Avenue, Montreal, QC, H4P 2R2, Canada
| | - Yves Durocher
- Human Health Therapeutics, National Research Council Canada, 6100 Royalmount Avenue, Montreal, QC, H4P 2R2, Canada
| | - Jeremy E Melanson
- Metrology, National Research Council Canada, 1200 Montreal Road, Ottawa, ON, K1A 0R6, Canada
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Abstract
Aggressive diagnostic testing remains an indispensable strategy for health and aged care facilities to prevent the transmission of SARS-CoV-2 in vulnerable populations. The preferred diagnostic platform has shifted towards COVID-19 rapid antigen tests (RATs) to identify the most infectious individuals. As such, RATs are being manufactured faster than at any other time in our history yet lack the relevant quantitative analytics required to inform on absolute analytical sensitivity enabling manufacturers to maintain high batch-to-batch reproducibility, and end-users to accurately compare brands for decision making. Here, we describe a novel reference standard to measure and compare the analytical sensitivity of RATs using a recombinant GFP-tagged nucleocapsid protein (NP-GFP). Importantly, we show that the GFP tag does not interfere with NP detection and provides several advantages affording streamlined protein expression and purification in high yields as well as faster, cheaper and more sensitive quality control measures for post-production assessment of protein solubility and stability. Ten commercial COVID-19 RATs were evaluated and ranked using NP-GFP as a reference standard. Analytical sensitivity data of the selected devices as determined with NP-GFP did not correlate with those reported by the manufacturers using the median tissue culture infectious dose (TCID50) assay. Of note, TCID50 discordance has been previously reported. Taken together, our results highlight an urgent need for a reliable reference standard for evaluation and benchmarking of the analytical sensitivity of RAT devices. NP-GFP is a promising candidate as a reference standard that will ensure that RAT performance is accurately communicated to healthcare providers and the public.
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Rodrigues-da-Silva RN, Conte FP, da Silva G, Carneiro-Alencar AL, Gomes PR, Kuriyama SN, Neto AAF, Lima-Junior JC. Identification of B-Cell Linear Epitopes in the Nucleocapsid (N) Protein B-Cell Linear Epitopes Conserved among the Main SARS-CoV-2 Variants. Viruses 2023; 15:v15040923. [PMID: 37112903 PMCID: PMC10145278 DOI: 10.3390/v15040923] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Revised: 03/31/2023] [Accepted: 04/01/2023] [Indexed: 04/29/2023] Open
Abstract
The Nucleocapsid (N) protein is highlighted as the main target for COVID-19 diagnosis by antigen detection due to its abundance in circulation early during infection. However, the effects of the described mutations in the N protein epitopes and the efficacy of antigen testing across SARS-CoV-2 variants remain controversial and poorly understood. Here, we used immunoinformatics to identify five epitopes in the SARS-CoV-2 N protein (N(34-48), N(89-104), N(185-197), N(277-287), and N(378-390)) and validate their reactivity against samples from COVID-19 convalescent patients. All identified epitopes are fully conserved in the main SARS-CoV-2 variants and highly conserved with SARS-CoV. Moreover, the epitopes N(185-197) and N(277-287) are highly conserved with MERS-CoV, while the epitopes N(34-48), N(89-104), N(277-287), and N(378-390) are lowly conserved with common cold coronaviruses (229E, NL63, OC43, HKU1). These data are in accordance with the observed conservation of amino acids recognized by the antibodies 7R98, 7N0R, and 7CR5, which are conserved in the SARS-CoV-2 variants, SARS-CoV and MERS-CoV but lowly conserved in common cold coronaviruses. Therefore, we support the antigen tests as a scalable solution for the population-level diagnosis of SARS-CoV-2, but we highlight the need to verify the cross-reactivity of these tests against the common cold coronaviruses.
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Affiliation(s)
- Rodrigo N Rodrigues-da-Silva
- Laboratory of Immunological Technology, Institute of Technology in Immunobiologicals, FIOCRUZ, Rio de Janeiro 21040-900, Brazil
| | - Fernando P Conte
- Eukaryotic Pilot Laboratory, Institute of Technology in Immunobiologicals, FIOCRUZ, Rio de Janeiro 21040-900, Brazil
| | - Gustavo da Silva
- Laboratory of Immunological Technology, Institute of Technology in Immunobiologicals, FIOCRUZ, Rio de Janeiro 21040-900, Brazil
| | - Ana L Carneiro-Alencar
- Laboratory of Immunological Technology, Institute of Technology in Immunobiologicals, FIOCRUZ, Rio de Janeiro 21040-900, Brazil
- Laboratory of Immunoparasitology, Oswaldo Cruz Institute, FIOCRUZ, Rio de Janeiro 21040-900, Brazil
| | - Paula R Gomes
- Getulio Vargas State Hospital, Rio de Janeiro 21070-061, Brazil
| | - Sergio N Kuriyama
- SENAI Innovation Institute for Green Chemistry, Rio de Janeiro 20271-030, Brazil
| | - Antonio A F Neto
- SENAI Innovation Institute for Green Chemistry, Rio de Janeiro 20271-030, Brazil
| | - Josué C Lima-Junior
- Laboratory of Immunoparasitology, Oswaldo Cruz Institute, FIOCRUZ, Rio de Janeiro 21040-900, Brazil
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Joubert S, Stuible M, Lord-Dufour S, Lamoureux L, Vaillancourt F, Perret S, Ouimet M, Pelletier A, Bisson L, Mahimkar R, Pham PL, L Ecuyer-Coelho H, Roy M, Voyer R, Baardsnes J, Sauvageau J, St-Michael F, Robotham A, Kelly J, Acel A, Schrag JD, El Bakkouri M, Durocher Y. A CHO stable pool production platform for rapid clinical development of trimeric SARS-CoV-2 spike subunit vaccine antigens. Biotechnol Bioeng 2023. [PMID: 36987713 DOI: 10.1002/bit.28387] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 03/02/2023] [Accepted: 03/14/2023] [Indexed: 03/30/2023]
Abstract
Protein expression from stably transfected Chinese hamster ovary (CHO) clones is an established but time-consuming method for manufacturing therapeutic recombinant proteins. The use of faster, alternative approaches, such as non-clonal stable pools, has been restricted due to lower productivity and longstanding regulatory guidelines. Recently, the performance of stable pools has improved dramatically, making them a viable option for quickly producing drug substance for GLP-toxicology and early-phase clinical trials in scenarios such as pandemics that demand rapid production timelines. Compared to stable CHO clones which can take several months to generate and characterize, stable pool development can be completed in only a few weeks. Here, we compared the productivity and product quality of trimeric SARS-CoV-2 spike protein ectodomains produced from stable CHO pools or clones. Using a set of biophysical and biochemical assays we show that product quality is very similar and that CHO pools demonstrate sufficient productivity to generate vaccine candidates for early clinical trials. Based on these data, we propose that regulatory guidelines should be updated to permit production of early clinical trial material from CHO pools to enable more rapid and cost-effective clinical evaluation of potentially life-saving vaccines.
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Affiliation(s)
- Simon Joubert
- Human Health Therapeutics Research Centre, National Research Council Canada, Montréal, Québec, Canada
| | - Matthew Stuible
- Human Health Therapeutics Research Centre, National Research Council Canada, Montréal, Québec, Canada
| | - Simon Lord-Dufour
- Human Health Therapeutics Research Centre, National Research Council Canada, Montréal, Québec, Canada
| | - Linda Lamoureux
- Human Health Therapeutics Research Centre, National Research Council Canada, Montréal, Québec, Canada
| | - François Vaillancourt
- Human Health Therapeutics Research Centre, National Research Council Canada, Montréal, Québec, Canada
| | - Sylvie Perret
- Human Health Therapeutics Research Centre, National Research Council Canada, Montréal, Québec, Canada
| | - Manon Ouimet
- Human Health Therapeutics Research Centre, National Research Council Canada, Montréal, Québec, Canada
| | - Alex Pelletier
- Human Health Therapeutics Research Centre, National Research Council Canada, Montréal, Québec, Canada
| | - Louis Bisson
- Human Health Therapeutics Research Centre, National Research Council Canada, Montréal, Québec, Canada
| | - Rohan Mahimkar
- Human Health Therapeutics Research Centre, National Research Council Canada, Montréal, Québec, Canada
| | - Phuong Lan Pham
- Human Health Therapeutics Research Centre, National Research Council Canada, Montréal, Québec, Canada
| | - Helene L Ecuyer-Coelho
- Human Health Therapeutics Research Centre, National Research Council Canada, Montréal, Québec, Canada
| | - Marjolaine Roy
- Human Health Therapeutics Research Centre, National Research Council Canada, Montréal, Québec, Canada
| | - Robert Voyer
- Human Health Therapeutics Research Centre, National Research Council Canada, Montréal, Québec, Canada
| | - Jason Baardsnes
- Human Health Therapeutics Research Centre, National Research Council Canada, Montréal, Québec, Canada
| | - Janelle Sauvageau
- Human Health Therapeutics Research Centre, National Research Council Canada, Ottawa, Ontario, Canada
| | - Frank St-Michael
- Human Health Therapeutics Research Centre, National Research Council Canada, Ottawa, Ontario, Canada
| | - Anna Robotham
- Human Health Therapeutics Research Centre, National Research Council Canada, Ottawa, Ontario, Canada
| | - John Kelly
- Human Health Therapeutics Research Centre, National Research Council Canada, Ottawa, Ontario, Canada
| | - Andrea Acel
- Human Health Therapeutics Research Centre, National Research Council Canada, Montréal, Québec, Canada
| | - Joseph D Schrag
- Human Health Therapeutics Research Centre, National Research Council Canada, Montréal, Québec, Canada
| | - Majida El Bakkouri
- Human Health Therapeutics Research Centre, National Research Council Canada, Montréal, Québec, Canada
| | - Yves Durocher
- Human Health Therapeutics Research Centre, National Research Council Canada, Montréal, Québec, Canada
- Department of Biochemistry and Molecular Medicine, Faculty of Medicine, Université de Montréal, Montréal, Québec, Canada
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