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Pan X, Wang J, Zhang K, Sun P, Shi J, Zhi J, Cai Z, Li Z, Wang D, Tong B, Dong Y. Differential detection of H1N1 virus spiker proteins by two hexaphenylbutadiene isomers based on size-matching principle. Anal Chim Acta 2024; 1299:342452. [PMID: 38499411 DOI: 10.1016/j.aca.2024.342452] [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: 02/05/2024] [Accepted: 03/05/2024] [Indexed: 03/20/2024]
Abstract
As one of the high pathogenic influenza viruses, H1N1 virus easily induces to serious diseases, even leading to death. To date, all detection methods for H1N1 virus had shortcomings, including high equipment cost, time consumption, and etc. Therefore, a novel detection method should be established to achieve more convenient, rapid, and low-cost detection. In this work, an isomer of HPBmN-I with aggregation-induced emission characteristic was firstly synthesized on the basis of our previous reported HPBpN-I. The results showed that HPBmN-I only selectively binds to N1 in the presence of H1, while HPBpN-I can exhibit total fluorescence response to H1 and N1 in H1/N1 mixture. The limited of detection (LOD) of HPBmN-I to N1 was estimated to be 20.82 ng/mL in normal saline (NS) according to the IUPAC-based approach. The simulation calculations based on molecular docking revealed that four HPBmN-I molecules combine well with the hydrophobic cavity of N1 and achieve the fluorescence enhancement due to size matching with each other. The combination of HPBpN-I and HPBmN-I as probes was successfully used to quantitatively detect H1 and N1 in real H1N1 virus. Compared to enzyme-linked immunosorbent assay (ELISA) method, the established method not only showed the same detection accuracy but also had the advantages of real-time, ease of preparation, and low-cost, demonstrating potential market prospects.
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Affiliation(s)
- Xiaoling Pan
- Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications, School of Material Science & Engineering, Beijing Institute of Technology, 5 South Zhongguancun Street, Beijing, 100081, China; Department of Nanomedicine & Shanghai Key Lab of Cell Engineering, Naval Medical University, Shanghai, 200433, China
| | - Jian Wang
- Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications, School of Material Science & Engineering, Beijing Institute of Technology, 5 South Zhongguancun Street, Beijing, 100081, China
| | - Kai Zhang
- Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications, School of Material Science & Engineering, Beijing Institute of Technology, 5 South Zhongguancun Street, Beijing, 100081, China
| | - Peng Sun
- Advanced Research Institute of Multidisciplinary Science, Beijing Institute of Technology, 5 South Zhongguancun Street, Beijing, 100081, China
| | - Jianbing Shi
- Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications, School of Material Science & Engineering, Beijing Institute of Technology, 5 South Zhongguancun Street, Beijing, 100081, China
| | - Junge Zhi
- School of Chemistry, Beijing Institute of Technology, 5 South Zhongguancun Street, Beijing, 100081, China
| | - Zhengxu Cai
- Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications, School of Material Science & Engineering, Beijing Institute of Technology, 5 South Zhongguancun Street, Beijing, 100081, China
| | - Zi Li
- National Institute for Viral Disease Control and Prevention, Collaboration Innovation Center for Diagnosis and Treatment of Infectious Diseases, Chinese Center for Disease Control and Prevention, Key Laboratory for Medical Virology, National Health and Family Planning Commission, Beijing, 102206, China
| | - Dayan Wang
- National Institute for Viral Disease Control and Prevention, Collaboration Innovation Center for Diagnosis and Treatment of Infectious Diseases, Chinese Center for Disease Control and Prevention, Key Laboratory for Medical Virology, National Health and Family Planning Commission, Beijing, 102206, China
| | - Bin Tong
- Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications, School of Material Science & Engineering, Beijing Institute of Technology, 5 South Zhongguancun Street, Beijing, 100081, China.
| | - Yuping Dong
- Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications, School of Material Science & Engineering, Beijing Institute of Technology, 5 South Zhongguancun Street, Beijing, 100081, China.
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2
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Donohue MP, Cao Z, Bowen T, Dickinson R, Zhang Y, Qian J. The CombE-IDMS Alternate Potency Method for H5N1 and H5N8 Cell-Based Vaccines. Vaccines (Basel) 2023; 11:1799. [PMID: 38140203 PMCID: PMC10747648 DOI: 10.3390/vaccines11121799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Revised: 11/14/2023] [Accepted: 11/23/2023] [Indexed: 12/24/2023] Open
Abstract
Assaying the potency of inactivated viral influenza vaccines is performed using single radial immunodiffusion, which is the globally accepted release method for potency. Under conditions of a rapidly emerging pandemic, such as the 2009 H1N1 influenza pandemic, a recognized obstacle in the delivery of vaccines to the public is the time needed for the distribution of calibrated SRID reagents (antisera and antigen standards) to vaccine manufacturers. Previously, we first described a novel streamlined MS-based assay, CombE-IDMS, which does not rely on antisera/antibodies or reference antigens, as a potential rapidly deployable alternate potency method through a comparison with SRID on adjuvanted seasonal quadrivalent vaccine cell-based (aQIVc) materials. In this report, we further demonstrate that the CombE-IDMS method can also be applied to measure the potency of pre-pandemic H5N1 and H5N8 monovalent vaccine materials, each subtype both unadjuvanted and adjuvanted, through a forced degradation study. Overall, CombE-IDMS results align with those of the gold standard SRID method on both H5N1 and H5N8 materials under conditions of thermal, pH, oxidative and freeze/thaw stress, lending further evidence for the CombE-IDMS method's suitability as an alternate assay for potency of both seasonal and pandemic influenza vaccines.
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Affiliation(s)
- Matthew P. Donohue
- Biopharmaceutical Product Development, CSL Seqirus, Holly Springs, NC 27540, USA; (Z.C.); (T.B.); (Y.Z.)
| | - Zhijun Cao
- Biopharmaceutical Product Development, CSL Seqirus, Holly Springs, NC 27540, USA; (Z.C.); (T.B.); (Y.Z.)
| | - Thomas Bowen
- Biopharmaceutical Product Development, CSL Seqirus, Holly Springs, NC 27540, USA; (Z.C.); (T.B.); (Y.Z.)
| | | | - Ying Zhang
- Biopharmaceutical Product Development, CSL Seqirus, Holly Springs, NC 27540, USA; (Z.C.); (T.B.); (Y.Z.)
| | - Jiang Qian
- Biopharmaceutical Product Development, CSL Seqirus, Holly Springs, NC 27540, USA; (Z.C.); (T.B.); (Y.Z.)
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3
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Qian J, Donohue MP, Bowen T, Zhang Y. The CombE-IDMS Assay as an Alternate Potency Method for Adjuvanted Quadrivalent Influenza Vaccines. Anal Chem 2023; 95:12842-12850. [PMID: 37587402 DOI: 10.1021/acs.analchem.3c02048] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/18/2023]
Abstract
The potency of all currently licensed inactivated influenza viral vaccines is assayed by the single radial immunodiffusion (SRID) method. SRID relies upon antisera and reference antigen reagents which are produced, standardized, and distributed in the mass quantities needed for vaccine manufacturers only after a significant amount of time has elapsed from the seasonal strain recommendations issued by the WHO; this time delay is exacerbated under conditions of an emerging pandemic. Previously, the limited trypsin digestion isotope dilution mass spectrometry (LTD-IDMS) method, which does not require antisera or reference antigens, demonstrated comparable quantitation of immunologically active hemagglutinin, the primary viral antigen, to SRID in stressed vaccine materials. Here, we demonstrate a streamlined improvement to the LTD-IDMS method by eliminating the need for its precipitation and washing steps, saving time and labor in the sample preparation process while paving the way for plate-based high-throughput analysis. This is accomplished using dissimilar proteases in the pretreatment (a combination of chymotrypsin and elastase) and analytical (trypsin) digestion steps so that any pretreatment digests will not cause interference while monitoring analytical tryptic digests by IDMS. The combination of enzymes (CombE)-IDMS method is tested alongside LTD-IDMS and SRID for the first time on MF59 adjuvanted seasonal cell-based quadrivalent influenza vaccines (aQIVc) under stressed conditions of heating, oxidation, lowered and elevated pH, and freeze-thaw. Overall, a correlation in the degradation trend is observed between CombE-IDMS and SRID in the four strains of the quadrivalent formulation, highlighting the method's stability indicating capability as a rapid alternate potency assay in a highly complex formulation of aQIVc.
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Affiliation(s)
- Jiang Qian
- Biopharmaceutical Product Development, CSL Seqirus, 475 Green Oaks Parkway, Holly Springs, North Carolina 27540, United States
| | - Matthew P Donohue
- Biopharmaceutical Product Development, CSL Seqirus, 475 Green Oaks Parkway, Holly Springs, North Carolina 27540, United States
| | - Thomas Bowen
- Biopharmaceutical Product Development, CSL Seqirus, 475 Green Oaks Parkway, Holly Springs, North Carolina 27540, United States
| | - Ying Zhang
- Biopharmaceutical Product Development, CSL Seqirus, 475 Green Oaks Parkway, Holly Springs, North Carolina 27540, United States
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4
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Ekimov A, Arunachalam AB, Blake T, Bodle J, Couzens L, Dubey S, Eichelberger M, Engelhardt OG, Gubinelli F, Joshi M, Melnyk D, Palladino G, Rigsby P, Rockman S, Savina N, Smith E, Gilchrist SAN. Assessing the stability-indicating properties of alternative potency assays for inactivated influenza vaccine. Vaccine 2023:S0264-410X(23)00726-0. [PMID: 37344260 DOI: 10.1016/j.vaccine.2023.06.051] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Revised: 05/01/2023] [Accepted: 06/13/2023] [Indexed: 06/23/2023]
Abstract
Determination of the potency of a vaccine is critical to ensuring that an appropriate dose is delivered, lot-to-lot consistency is maintained, and that the formulation is stable over the life of the vaccine. The potency of inactivated influenza vaccines is determined routinely by the Single Radial Immunodiffusion (SRID) assay. A number of alternative potency assays have been proposed and have been under evaluation in recent years. The aim of this study was to compare a surface plasmon resonance-based assay and two different enzyme linked immunoassays against the current potency assay, SRID, and against mouse immunogenicity when haemagglutinin antigen of the A(H1N1)pdm09 component of an inactivated influenza vaccine is stressed by elevated temperature, low pH and freezing. This analysis demonstrated that the alternative assays had good correspondence with SRID for samples from most stress conditions and that the immunogenicity in mice corresponded with potency in SRID for all stress samples. Subject to further analysis, the assays have been shown to have the potential to possibly replace, and at least complement, SRID.
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Affiliation(s)
- Aleksei Ekimov
- Department of New Technologies, Federal State Unitary Enterprise (FSUE), Saint-Petersburg Scientific Research Institute of Vaccines and Serums (SPbSRIVS), Federal Medical-Biological Agency (FMBA) of Russia, Saint-Petersburg 198320, Russian Federation.
| | - Arun B Arunachalam
- Global Analytical Sciences, R&D Sanofi, 1 Discovery Dr, Swiftwater, PA 18370, USA.
| | - Taylor Blake
- Global Analytical Sciences, R&D Sanofi, 1 Discovery Dr, Swiftwater, PA 18370, USA.
| | - Jesse Bodle
- Technical Development and Global Process Innovation, Seqirus Ltd, 63 Poplar Rd, Parkville, Victoria 3052, Australia.
| | - Laura Couzens
- Division of Biological Standards and Quality Control (DBSQC), Office of Compliance and Biologics Quality, Center for Biologics Evaluation and Research (CBER), US Food & Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD 20993-0002, United States of America.
| | - Sitara Dubey
- Standards Lifecycle, Scientific Research & Innovation, Medicines and Healthcare Products Regulatory Agency, Blanche Lane, South Mimms, Potters Bar EN6 3QG, UK.
| | - Maryna Eichelberger
- Division of Biological Standards and Quality Control (DBSQC), Office of Compliance and Biologics Quality, Center for Biologics Evaluation and Research (CBER), US Food & Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD 20993-0002, United States of America.
| | - Othmar G Engelhardt
- Vaccines, Scientific Research & Innovation, Medicines and Healthcare products Regulatory Agency, Blanche Lane, South Mimms, Potters Bar EN6 3QG, UK.
| | - Francesco Gubinelli
- Standards Lifecycle, Scientific Research & Innovation, Medicines and Healthcare Products Regulatory Agency, Blanche Lane, South Mimms, Potters Bar EN6 3QG, UK.
| | - Manju Joshi
- Division of Biological Standards and Quality Control (DBSQC), Office of Compliance and Biologics Quality, Center for Biologics Evaluation and Research (CBER), US Food & Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD 20993-0002, United States of America.
| | - Darya Melnyk
- Division of Biological Standards and Quality Control (DBSQC), Office of Compliance and Biologics Quality, Center for Biologics Evaluation and Research (CBER), US Food & Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD 20993-0002, United States of America.
| | - Giuseppe Palladino
- Preclinical Research, Seqirus, 50 Hampshire Street, 9th Floor Cambridge, MA 02139, United States of America.
| | - Peter Rigsby
- Analytical and Biological Sciences, Scientific Research & Innovation, Medicines and Healthcare Products Regulatory Agency, Blanche Lane, South Mimms, Potters Bar EN6 3QG, UK.
| | - Steven Rockman
- Technical Development and Global Process Innovation, Seqirus Ltd, 63 Poplar Rd, Parkville, Victoria 3052, Australia.
| | - Natalya Savina
- Department of New Technologies, Federal State Unitary Enterprise (FSUE), Saint-Petersburg Scientific Research Institute of Vaccines and Serums (SPbSRIVS), Federal Medical-Biological Agency (FMBA) of Russia, Saint-Petersburg 198320, Russian Federation.
| | - Elena Smith
- Analytical CMC, Vaccine mRNA Center of Excellence, Sanofi, 200 West Street, Waltham, MA 02451, United States of America.
| | - Shawn A N Gilchrist
- S Gilchrist Consulting Services Inc, 8 Covebank Crescent, Brampton, ON L6P 2X5, Canada.
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5
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Sutton WJH, Branham PJ, Williamson YM, Cooper HC, Najjar FN, Pierce-Ruiz CL, Barr JR, Williams TL. Quantification of SARS-CoV-2 spike protein expression from mRNA vaccines using isotope dilution mass spectrometry. Vaccine 2023:S0264-410X(23)00458-9. [PMID: 37202272 DOI: 10.1016/j.vaccine.2023.04.044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 04/03/2023] [Accepted: 04/17/2023] [Indexed: 05/20/2023]
Abstract
The advent of mRNA vaccine technology has been vital in rapidly creating and manufacturing COVID-19 vaccines at an industrial scale. To continue to accelerate this leading vaccine technology, an accurate method is needed to quantify antigens produced by the transfection of cells with a mRNA vaccine product. This will allow monitoring of protein expression during mRNA vaccine development and provide information on how changes to vaccine components affects the expression of the desired antigen. Developing novel approaches that allow for high-throughput screening of vaccines to detect changes in antigen production in cell culture prior to in vivo studies could aid vaccine development. We have developed and optimized an isotope dilution mass spectrometry method to detect and quantify the spike protein expressed after transfection of baby hamster kidney cells with expired COVID-19 mRNA vaccines. Five peptides of the spike protein are simultaneously quantified and provide assurance that protein digestion in the region of the target peptides is complete since results between the five peptides had a relative standard deviation of less than 15 %. In addition, two housekeeping proteins, actin and GAPDH, are quantified in the same analytical run to account for any variation in cell growth within the experiment. IDMS allows a precise and accurate means to quantify protein expression by mammalian cells transfected with an mRNA vaccine.
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Affiliation(s)
- William J H Sutton
- Oak Ridge Institute for Science and Education, Centers for Disease Control and Prevention, Atlanta, GA 30341, USA
| | - Paul J Branham
- Oak Ridge Institute for Science and Education, Centers for Disease Control and Prevention, Atlanta, GA 30341, USA
| | - Yulanda M Williamson
- National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA 30341, USA
| | - Hans C Cooper
- National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA 30341, USA
| | - Fabio N Najjar
- Oak Ridge Institute for Science and Education, Centers for Disease Control and Prevention, Atlanta, GA 30341, USA
| | - Carrie L Pierce-Ruiz
- National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA 30341, USA
| | - John R Barr
- National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA 30341, USA
| | - Tracie L Williams
- National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA 30341, USA.
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6
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Cheung CY, Dubey S, Hadrovic M, Ball CR, Ramage W, McDonald JU, Harvey R, Hufton SE, Engelhardt OG. Development of an ELISA-Based Potency Assay for Inactivated Influenza Vaccines Using Cross-Reactive Nanobodies. Vaccines (Basel) 2022; 10:vaccines10091473. [PMID: 36146550 PMCID: PMC9503116 DOI: 10.3390/vaccines10091473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Revised: 08/22/2022] [Accepted: 08/25/2022] [Indexed: 11/16/2022] Open
Abstract
Inactivated vaccines are the main influenza vaccines used today; these are usually presented as split (detergent-disrupted) or subunit vaccines, while whole-virus-inactivated influenza vaccines are rare. The single radial immune diffusion (SRD) assay has been used as the gold standard potency assay for inactivated influenza vaccines for decades; however, more recently, various alternative potency assays have been proposed. A new potency test should be able to measure the amount of functional antigen in the vaccine, which in the case of influenza vaccines is the haemagglutinin (HA) protein. Potency tests should also be able to detect the loss of potency caused by changes to the structural and functional integrity of HA. To detect such changes, most alternative potency tests proposed to date use antibodies that react with native HA. Due to the frequent changes in influenza vaccine composition, antibodies may need to be updated in line with changes in vaccine viruses. We have developed two ELISA-based potency assays for group 1 influenza A viruses using cross-reactive nanobodies. The nanobodies detect influenza viruses of subtype H1N1 spanning more than three decades, as well as H5N1 viruses, in ELISA. We found that the new ELISA potency assays are sensitive to the nature of the reference antigen (standard) used to quantify vaccine antigens; using standards matched in their presentation to the vaccine type improved correspondence between the ELISA and SRD assays.
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Affiliation(s)
- Chung Y. Cheung
- Vaccines Division, Scientific Research & Innovation, Medicines and Healthcare Products Regulatory Agency, South Mimms, Potters Bar EN6 3QG, UK
| | - Sitara Dubey
- Vaccines Division, Scientific Research & Innovation, Medicines and Healthcare Products Regulatory Agency, South Mimms, Potters Bar EN6 3QG, UK
| | - Martina Hadrovic
- Vaccines Division, Scientific Research & Innovation, Medicines and Healthcare Products Regulatory Agency, South Mimms, Potters Bar EN6 3QG, UK
| | - Christina R. Ball
- Biotherapeutics Division, Scientific Research & Innovation, Medicines and Healthcare Products Regulatory Agency, South Mimms, Potters Bar EN6 3QG, UK
| | - Walter Ramage
- Biotherapeutics Division, Scientific Research & Innovation, Medicines and Healthcare Products Regulatory Agency, South Mimms, Potters Bar EN6 3QG, UK
| | - Jacqueline U. McDonald
- Vaccines Division, Scientific Research & Innovation, Medicines and Healthcare Products Regulatory Agency, South Mimms, Potters Bar EN6 3QG, UK
| | - Ruth Harvey
- Vaccines Division, Scientific Research & Innovation, Medicines and Healthcare Products Regulatory Agency, South Mimms, Potters Bar EN6 3QG, UK
| | - Simon E. Hufton
- Biotherapeutics Division, Scientific Research & Innovation, Medicines and Healthcare Products Regulatory Agency, South Mimms, Potters Bar EN6 3QG, UK
| | - Othmar G. Engelhardt
- Vaccines Division, Scientific Research & Innovation, Medicines and Healthcare Products Regulatory Agency, South Mimms, Potters Bar EN6 3QG, UK
- Correspondence:
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7
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Pierce-Ruiz C, Santana WI, Sutton WJH, Fischler DA, Cooper HC, Marc LR, Barr JR, Williams TL. Quantification of SARS-CoV-2 spike and nucleocapsid proteins using isotope dilution tandem mass spectrometry. Vaccine 2021; 39:5106-5115. [PMID: 34344552 PMCID: PMC8302847 DOI: 10.1016/j.vaccine.2021.07.066] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Revised: 07/20/2021] [Accepted: 07/21/2021] [Indexed: 12/21/2022]
Abstract
The emergence and subsequent global outbreak of the novel coronavirus SARS-CoV-2 prompted our laboratory to launch efforts to develop methods for SARS-CoV-2 antigen detection and quantification. We present an isotope dilution mass spectrometry method (IDMS) for rapid and accurate quantification of the primary antigens, spike and nucleocapsid proteins. This IDMS method utilizes liquid chromatography-tandem mass spectrometry (LC-MS/MS) to analyze sample tryptic digests for detection and quantification of selected conserved peptides of SARS-CoV-2 spike and nucleocapsid proteins. The IDMS method has the necessary attributes to be successfully utilized for accurate quantification in SARS-CoV-2 protein-based vaccines and as targets of rapid diagnostic tests. Absolute quantification was achieved by quantifying and averaging 5 peptides for spike protein (3 peptides in the S1 subunit and 2 peptides in the S2 subunit) and 4 peptides for nucleocapsid protein. The overall relative standard deviation of the method was 3.67% for spike protein and 5.11% for nucleocapsid protein. IDMS offers speed (5 h total analysis time), sensitivity (LOQ; 10 fmol/µL) and precision for quantification of SARS-CoV-2 spike and nucleocapsid proteins.
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Affiliation(s)
- Carrie Pierce-Ruiz
- National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA 30341, USA.
| | - Wanda I Santana
- National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA 30341, USA.
| | - William J H Sutton
- Oak Ridge Institute for Science and Education, Centers for Disease Control and Prevention, Atlanta, GA 30341, USA.
| | - David A Fischler
- Oak Ridge Institute for Science and Education, Centers for Disease Control and Prevention, Atlanta, GA 30341, USA.
| | - Hans C Cooper
- National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA 30341, USA.
| | - Lidoshka R Marc
- Oak Ridge Institute for Science and Education, Centers for Disease Control and Prevention, Atlanta, GA 30341, USA.
| | - John R Barr
- National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA 30341, USA.
| | - Tracie L Williams
- National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA 30341, USA.
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