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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; 416:4861-4872. [PMID: 38942955 PMCID: PMC11330416 DOI: 10.1007/s00216-024-05413-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [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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2
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Shibayama S, Osumi Y, Takatsu A, Kato M. Identification and optimization of parameters for accurate quantification of RNA by RT-dPCR. Anal Bioanal Chem 2024:10.1007/s00216-024-05447-x. [PMID: 39046502 DOI: 10.1007/s00216-024-05447-x] [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: 05/02/2024] [Revised: 06/28/2024] [Accepted: 07/02/2024] [Indexed: 07/25/2024]
Abstract
Reverse transcription-digital PCR (RT-dPCR) is attracting attention as a method that enables SI-traceable RNA quantification without calibration, but its accuracy and bias have not been thoroughly studied. In this study, the accurate quantification of RNA by the RT-dPCR method was investigated using NMIJ CRM 6204-b, an RNA certified reference material whose certified value was assigned by orthogonal chemical measurement methods. Moreover, a two-step RT-dPCR method was adopted to examine in detail the conditions for the RT reaction process, which was expected to be the major uncertainty component in the RT-dPCR measurement. Optimization experiments revealed that the type of reverse transcriptase, the concentration of template RNA, and the type and concentration of primers in the RT reaction affected the value quantified by RT-dPCR. Under the optimal conditions, the value quantified by RT-dPCR, 76.4 ng/μL ± 6.7 ng/μL (the quantified value ± expanded uncertainty (k = 2)), was consistent with the certified value, 68.2 ng/μL ± 5.8 ng/μL, of NMIJ CRM 6204-b RNA 1000-A within the expanded uncertainty. From the results of the uncertainty evaluation, the relative combined uncertainty of the RT-dPCR method was 4.42%, and the major uncertainty components in the RT-dPCR method were the preparation of RT solution (3.68%), the inter-day difference (1.80%), and the RT reaction (1.30%). Together, the results suggested that the contribution of the RT reaction process to the total uncertainty was greater than that of the dPCR process.
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Affiliation(s)
- Sachie Shibayama
- National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan.
| | - Yukiko Osumi
- National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan
| | - Akiko Takatsu
- National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan
| | - Megumi Kato
- National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan
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3
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Lee SS, Kim AL, Park JH, Lee DH, Bae YK. Optimization of duplex digital PCR for the measurement of SARS-CoV-2 RNA. J Virol Methods 2024; 326:114911. [PMID: 38447644 DOI: 10.1016/j.jviromet.2024.114911] [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: 11/28/2023] [Revised: 01/19/2024] [Accepted: 03/02/2024] [Indexed: 03/08/2024]
Abstract
Quantitative PCR (qPCR) is the gold standard for detecting nucleic acid sequences specific to the target pathogen. For COVID-19 diagnosis, several molecular assays have been developed. In this study, we present an optimization strategy for the measurement of SARS-CoV-2 RNA via multiplex qPCR and digital PCR (dPCR). Compared to qPCR, both droplet and chip-based dPCR, which are known to be more sensitive and accurate, showed a better resilience to suboptimal assay compositions and cycling conditions following the proposed optimizations. In particular, the formation of heterodimers among assays greatly interfered with qPCR results, but only minimally with dPCR results. In dPCR, existing heterodimers lowered the PCR efficiency, producing a dampened fluorescent signal in positive partitions. This can be corrected by adjusting the PCR cycling conditions, after which dPCR shows the capability of measuring the expected copy number. In addition, we present a process to improve the existing RdRp assay by correcting the primer sequences and matching the melting temperature, ultimately producing highly sensitive and robust assays. The results of this study can reduce the cost and time of SARS-CoV-2 diagnosis while increasing accuracy. Furthermore, our results suggest that dPCR is a reliable method for the accurate measurement of nucleic acid targets.
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Affiliation(s)
- Sang-Soo Lee
- Biometrology Group, Korea Research Institute of Standards and Science, Daejeon, Republic of Korea
| | - Ah Leum Kim
- Biometrology Group, Korea Research Institute of Standards and Science, Daejeon, Republic of Korea; Graduate School of Analytical Science and Technology, Chungnam National University, Daejeon, Republic of Korea
| | - Jae-Hyung Park
- Biometrology Group, Korea Research Institute of Standards and Science, Daejeon, Republic of Korea
| | - Da-Hye Lee
- Biometrology Group, Korea Research Institute of Standards and Science, Daejeon, Republic of Korea.
| | - Young-Kyung Bae
- Biometrology Group, Korea Research Institute of Standards and Science, Daejeon, Republic of Korea; Graduate School of Analytical Science and Technology, Chungnam National University, Daejeon, Republic of Korea.
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4
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Ju DU, Park D, Kim IH, Kim S, Yoo HM. Development of Human Rhinovirus RNA Reference Material Using Digital PCR. Genes (Basel) 2023; 14:2210. [PMID: 38137032 PMCID: PMC10742479 DOI: 10.3390/genes14122210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Revised: 12/08/2023] [Accepted: 12/11/2023] [Indexed: 12/24/2023] Open
Abstract
The human rhinovirus (RV) is a positive-stranded RNA virus that causes respiratory tract diseases affecting both the upper and lower halves of the respiratory system. RV enhances its replication by concentrating RNA synthesis within a modified host membrane in an intracellular compartment. RV infections often occur alongside infections caused by other respiratory viruses, and the RV virus may remain asymptomatic for extended periods. Alongside qualitative detection, it is essential to accurately quantify RV RNA from clinical samples to explore the relationships between RV viral load, infections caused by the virus, and the resulting symptoms observed in patients. A reference material (RM) is required for quality evaluation, the performance evaluation of molecular diagnostic products, and evaluation of antiviral agents in the laboratory. The preparation process for the RM involves creating an RV RNA mixture by combining RV viral RNA with RNA storage solution and matrix. The resulting RV RNA mixture is scaled up to a volume of 25 mL, then dispensed at 100 µL per vial and stored at -80 °C. The process of measuring the stability and homogeneity of RV RMs was conducted by employing reverse transcription droplet digital polymerase chain reaction (RT-ddPCR). Digital PCR is useful for the analysis of standards and can help to improve measurement compatibility: it represents the equivalence of a series of outcomes for reference materials and samples being analyzed when a few measurement procedures are employed, enabling objective comparisons between quantitative findings obtained through various experiments. The number of copies value represents a measured result of approximately 1.6 × 105 copies/μL. The RM has about an 11% bottle-to-bottle homogeneity and shows stable results for 1 week at temperatures of 4 °C and -20 °C and for 12 months at a temperature of -80 °C. The developed RM can enhance the dependability of RV molecular tests by providing a precise reference value for the absolute copy number of a viral target gene. Additionally, it can serve as a reference for diverse studies.
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Affiliation(s)
- Dong U Ju
- Biometrology Group, Korea Research Institute of Standards and Science (KRISS), Daejeon 34113, Republic of Korea
- School of Biomedical Engineering, Korea University, Seoul 02841, Republic of Korea
| | - Dongju Park
- Biometrology Group, Korea Research Institute of Standards and Science (KRISS), Daejeon 34113, Republic of Korea
| | - Il-Hwan Kim
- Biometrology Group, Korea Research Institute of Standards and Science (KRISS), Daejeon 34113, Republic of Korea
| | - Seil Kim
- Biometrology Group, Korea Research Institute of Standards and Science (KRISS), Daejeon 34113, Republic of Korea
- Department of Precision Measurement, University of Science & Technology (UST), Daejeon 34113, Republic of Korea
| | - Hee Min Yoo
- Biometrology Group, Korea Research Institute of Standards and Science (KRISS), Daejeon 34113, Republic of Korea
- Department of Precision Measurement, University of Science & Technology (UST), Daejeon 34113, Republic of Korea
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Xu D, Zhang W, Li H, Li N, Lin JM. Advances in droplet digital polymerase chain reaction on microfluidic chips. LAB ON A CHIP 2023; 23:1258-1278. [PMID: 36752545 DOI: 10.1039/d2lc00814a] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
The PCR technique has been known to the general public since the pandemic outbreak of COVID-19. This technique has progressed through three stages: from simple PCR to real-time fluorescence PCR to digital PCR. Among them, the microfluidic-based droplet digital PCR technique has attracted much attention and has been widely applied due to its advantages of high throughput, high sensitivity, low reagent consumption, low cross-contamination, and absolute quantification ability. In this review, we introduce various designs of microfluidic-based ddPCR developed within the last decade. The microfluidic-based droplet generation methods, thermal cycle strategies, and signal counting approaches are described, and the applications in the fields of single-cell analysis, disease diagnosis, and pathogen detection are introduced. Further, the challenges and prospects of microfluidic-based ddPCR are discussed. We hope that this review can contribute to the further development of the microfluidic-based ddPCR technique.
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Affiliation(s)
- Danfeng Xu
- Key Laboratory of Chemical Metrology and Applications on Nutrition and Health for State Market Regulation, Division of Chemical Metrology and Analytical Science, National Institute of Metrology, Beijing 100029, China.
| | - Weifei Zhang
- Key Laboratory of Chemical Metrology and Applications on Nutrition and Health for State Market Regulation, Division of Chemical Metrology and Analytical Science, National Institute of Metrology, Beijing 100029, China.
| | - Hongmei Li
- Key Laboratory of Chemical Metrology and Applications on Nutrition and Health for State Market Regulation, Division of Chemical Metrology and Analytical Science, National Institute of Metrology, Beijing 100029, China.
| | - Nan Li
- Department of Chemistry, Beijing Key Laboratory of Microanalytical Methods and Instrumentation Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology (Ministry of Education), China.
| | - Jin-Ming Lin
- Department of Chemistry, Beijing Key Laboratory of Microanalytical Methods and Instrumentation Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology (Ministry of Education), China.
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6
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Wang D, Liu E, Liu H, Jin X, Niu C, Gao Y, Su X. A droplet digital PCR assay for detection and quantification of Verticillium nonalfalfae and V. albo-atrum. Front Cell Infect Microbiol 2023; 12:1110684. [PMID: 36710974 PMCID: PMC9874294 DOI: 10.3389/fcimb.2022.1110684] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Accepted: 12/20/2022] [Indexed: 01/13/2023] Open
Abstract
Verticillium nonalfalfae and V. albo-atrum are notorious pathogenic fungi that cause a destructive vascular disease called Verticillium wilt worldwide. Thus, timely and quantitative monitoring of fungal progression is highly desirable for early diagnosis and risk assessment. In this study, we developed a droplet digital polymerase chain reaction (ddPCR) assay to detect and quantify V. nonalfalfae and V. albo-atrum. The performance of this assay was validated in comparison with that of a quantitative real-time polymerase chain reaction (qPCR) assay. The standard curve analysis of the ddPCR assay showed good linearity. The ddPCR assay indicated similar detection sensitivity to that of qPCR on pure genomic DNA, while it enhanced the positive rate for low-abundance fungi, especially in alfalfa stems. Receiver operating characteristic analysis revealed that ddPCR provided superior diagnostic performance on field tissues compared to qPCR, and the area under curve values were 0.94 and 0.90 for alfalfa roots and stems, respectively. Additionally, the quantitative results of the two methods were highly concordant (roots: R2 = 0.91; stems: R2 = 0.76); however, the concentrations determined by ddPCR were generally higher than those determined by qPCR. This discrepancy was potentially caused by differing amplification efficiencies for qPCR between cultured and field samples. Furthermore, the ddPCR assays appreciably improved quantitative precision, as reflected by lower coefficients of variation. Overall, the ddPCR method enables sensitive detection and accurate quantification of V. nonalfalfae and V. albo-atrum, providing a valuable tool for evaluating disease progression and enacting effective disease control.
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Affiliation(s)
- Di Wang
- 1Center for Advanced Measurement Science, National Institute of Metrology, Beijing, China
| | - Enliang Liu
- 2Institute of Grain Crops, Xinjiang Academy of Agricultural Sciences, Urumqi, China
| | - Haiyang Liu
- 3Institute of Plant Protection, Xinjiang Academy of Agricultural Sciences, Urumqi, China
| | - Xi Jin
- 4Hebei Technology Innovation Center for Green Management of Soil-Borne Diseases, Baoding University, Hebei, China
| | - Chunyan Niu
- 1Center for Advanced Measurement Science, National Institute of Metrology, Beijing, China
| | - Yunhua Gao
- 1Center for Advanced Measurement Science, National Institute of Metrology, Beijing, China,*Correspondence: Yunhua Gao, ; Xiaofeng Su,
| | - Xiaofeng Su
- 5Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China,*Correspondence: Yunhua Gao, ; Xiaofeng Su,
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7
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Hou Y, Chen S, Zheng Y, Zheng X, Lin JM. Droplet-based digital PCR (ddPCR) and its applications. Trends Analyt Chem 2022. [DOI: 10.1016/j.trac.2022.116897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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8
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Zai Y, Min C, Wang Z, Ding Y, Zhao H, Su E, He N. A sample-to-answer, quantitative real-time PCR system with low-cost, gravity-driven microfluidic cartridge for rapid detection of SARS-CoV-2, influenza A/B, and human papillomavirus 16/18. LAB ON A CHIP 2022; 22:3436-3452. [PMID: 35972195 DOI: 10.1039/d2lc00434h] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The pandemic of coronavirus disease 2019 (COVID-19), due to the novel coronavirus (SARS-CoV-2), has created an unprecedented threat to the global health system, especially in resource-limited areas. This challenge shines a spotlight on the urgent need for a point-of-care (POC) quantitative real-time PCR (qPCR) test for sensitive and rapid diagnosis of viral infections. In a POC system, a closed, single-use, microfluidic cartridge is commonly utilized for integration of nucleic acid preparation, PCR amplification and florescence detection. But, most current cartridge systems often involve complicated nucleic acid extraction via active pumping that relies on cumbersome external hardware, causing increases in system complexity and cost. In this work, we demonstrate a gravity-driven cartridge design for an integrated viral RNA/DNA diagnostic test that does not require auxiliary hardware for fluid pumping due to adopted extraction-free amplification. This microfluidic cartridge only contains two reaction chambers for nucleic acid lysis and amplification respectively, enabling a fast qPCR test in less than 30 min. This gravity-driven pumping strategy can help simplify and minimize the microfluidic cartridge, thus enabling high-throughput (up to 12 test cartridges per test) molecular detection via a small cartridge readout system. Thus, this work addresses the scalability limitation of POC molecular testing and can be run in any settings. We verified the analytical sensitivity and specificity of the cartridge testing for respiratory pathogens and sexually transmitted diseases using SARS-CoV-2, influenza A/B RNA samples, and human papillomavirus 16/18 DNA samples. Our cartridge system exhibited a comparable detection performance to the current gold standard qPCR instrument ABI 7500. Moreover, our system showed very high diagnostic accuracy for viral RNA/DNA detection that was well validated by ROC curve analysis. The sample-to-answer molecular testing system reported in this work has the advantages of simplicity, rapidity, and low cost, making it highly promising for prevention and control of infectious diseases in poor-resource areas.
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Affiliation(s)
- Yunfeng Zai
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Si Pai Lou 2, Nanjing 210096, China.
- Getein Biotechnology Co., Ltd., Nanjing 210000, China.
| | - Chao Min
- Getein Biotechnology Co., Ltd., Nanjing 210000, China.
| | - Zunliang Wang
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Si Pai Lou 2, Nanjing 210096, China.
| | - Yongjun Ding
- Getein Biotechnology Co., Ltd., Nanjing 210000, China.
| | - Huan Zhao
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Si Pai Lou 2, Nanjing 210096, China.
- Getein Biotechnology Co., Ltd., Nanjing 210000, China.
| | - Enben Su
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Si Pai Lou 2, Nanjing 210096, China.
- Getein Biotechnology Co., Ltd., Nanjing 210000, China.
| | - Nongyue He
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Si Pai Lou 2, Nanjing 210096, China.
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Park C, Kim KW, Park D, Hassan ZU, Park EC, Lee CS, Rahman MDT, Yi H, Kim S. Rapid and sensitive amplicon-based genome sequencing of SARS-CoV-2. Front Microbiol 2022; 13:876085. [PMID: 36060750 PMCID: PMC9428490 DOI: 10.3389/fmicb.2022.876085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 07/29/2022] [Indexed: 12/02/2022] Open
Abstract
As SARS-CoV-2 variants of concern emerged, the genome sequencing of SARS-CoV-2 strains became more important. In this study, SARS-CoV-2 was sequenced using amplicon-based genome sequencing with MinION. The primer panel used in this study consisted of only 11 primer panels and the size of the amplicons was approximately 3 kb. Full genome sequences were obtained with a hundred copies of the SARS-CoV-2 genome, and 92.33% and 75.39% of the genome sequences were obtained with 10 copies of the SARS-CoV-2 genome. The few differences in nucleotide sequences originated from mutations in laboratory cultures and/or mixed nucleotide sequences. The quantification of the SARS-CoV-2 genomic RNA was done using RT-ddPCR methods, and the level of LoD indicated that this sequencing method can be used for any RT-qPCR positive clinical sample. The sequencing results of the SARS-CoV-2 variants and clinical samples showed that our methods were very reliable. The genome sequences of five individual clinical samples were almost identical, and the analysis of the sequence variance showed that most of these nucleotide substitutions were observed in the genome sequences of the other clinical samples, indicating this amplicon-based whole-genome sequencing method can be used in various clinical fields.
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Affiliation(s)
- Changwoo Park
- Microbiological Analysis Team, Group for Biometrology, Korea Research Institute of Standards and Science (KRISS), Daejeon, South Korea
- Convergent Research Center for Emerging Virus Infection, Korea Research Institute of Chemical Technology (KRICT), Daejeon, South Korea
- Department of Agricultural Biotechnology, Seoul National University, Seoul, South Korea
| | - Kwan Woo Kim
- Department of Public Health Sciences, Graduate School, Korea University, Seoul, South Korea
- Interdisciplinary Program in Precision Public Health, Korea University, Seoul, South Korea
| | - Dongju Park
- Microbiological Analysis Team, Group for Biometrology, Korea Research Institute of Standards and Science (KRISS), Daejeon, South Korea
- Convergent Research Center for Emerging Virus Infection, Korea Research Institute of Chemical Technology (KRICT), Daejeon, South Korea
- Department of Biological Science, Chungnam National University College of Bioscience and Biotechnology, Daejeon, South Korea
| | - Zohaib ul Hassan
- Microbiological Analysis Team, Group for Biometrology, Korea Research Institute of Standards and Science (KRISS), Daejeon, South Korea
- Convergent Research Center for Emerging Virus Infection, Korea Research Institute of Chemical Technology (KRICT), Daejeon, South Korea
- Department of Bio-Analysis Science, University of Science and Technology (UST), Daejeon, South Korea
| | - Edmond Changkyun Park
- Convergent Research Center for Emerging Virus Infection, Korea Research Institute of Chemical Technology (KRICT), Daejeon, South Korea
- Department of Bio-Analysis Science, University of Science and Technology (UST), Daejeon, South Korea
- Research Center for Bioconvergence Analysis, Korea Basic Science Institute, Cheongju, South Korea
| | - Chang-Seop Lee
- Department of Internal Medicine, Jeonbuk National University Medical School, Jeonju, South Korea
- Research Institute of Clinical Medicine of Jeonbuk National University – Biomedical Research Institute of Jeonbuk National University Hospital, Jeonju, South Korea
| | - MD Tazikur Rahman
- Department of Internal Medicine, Jeonbuk National University Medical School, Jeonju, South Korea
- Department of Medical Science, Jeonbuk National University Medical School, Jeonju, South Korea
| | - Hana Yi
- Department of Public Health Sciences, Graduate School, Korea University, Seoul, South Korea
- Interdisciplinary Program in Precision Public Health, Korea University, Seoul, South Korea
- School of Biosystems and Biomedical Sciences, Korea University, Seoul, South Korea
| | - Seil Kim
- Microbiological Analysis Team, Group for Biometrology, Korea Research Institute of Standards and Science (KRISS), Daejeon, South Korea
- Convergent Research Center for Emerging Virus Infection, Korea Research Institute of Chemical Technology (KRICT), Daejeon, South Korea
- Department of Bio-Analysis Science, University of Science and Technology (UST), Daejeon, South Korea
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10
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Accurate quantification of SARS-CoV-2 RNA by isotope dilution mass spectrometry and providing a correction of reverse transcription efficiency in droplet digital PCR. Anal Bioanal Chem 2022; 414:6771-6777. [PMID: 35941317 PMCID: PMC9360635 DOI: 10.1007/s00216-022-04238-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Revised: 07/13/2022] [Accepted: 07/18/2022] [Indexed: 11/01/2022]
Abstract
The novel coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has infected more than 505 million confirmed cases, including over 6 million deaths. Reference materials (RMs) of SARS-CoV-2 RNA played a crucial role in performance evaluation and quality control of testing laboratories. As the potential primary characterization method of RMs, reverse transcription digital PCR (RT-dPCR) measures the copy number of RNA, but the accuracy of reverse transcription (RT) efficiency has yet to be confirmed. This study established a method of enzymatic digestion followed by isotope dilution mass spectrometry (IDMS), which does not require an RT reaction, to quantify in vitro-transcribed SARS-CoV-2 RNA. RNA was digested to nucleotide monophosphate (NMP) within 15 min and analyzed by IDMS within 5 min. The consistency among the results of four different NMPs demonstrated the reliability of the proposed method. Compared to IDMS, the quantitative result of RT-dPCR turned out to be about 10% lower, possibly attributed to the incompleteness of the reverse transcription process. Therefore, the proposed approach could be valuable and reliable for quantifying RNA molecules and evaluating the RT efficiency of RT-based methods.
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11
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Stocks BB, Thibeault MP, Schrag JD, Melanson JE. Characterization of a SARS-CoV-2 spike protein reference material. Anal Bioanal Chem 2022; 414:3561-3569. [PMID: 35260938 PMCID: PMC8904068 DOI: 10.1007/s00216-022-04000-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Revised: 02/22/2022] [Accepted: 03/01/2022] [Indexed: 12/23/2022]
Abstract
Development of diagnostic testing capability has advanced with unprecedented pace in response to the COVID-19 pandemic. An undesirable effect of such speed is a lack of standardization, often leading to unreliable test results. To assist the research community surmount this challenge, the National Research Council Canada has prepared a SARS-CoV-2 spike protein reference material, SMT1-1, as a buffered solution. Value assignment was achieved by amino acid analysis (AAA) by double isotope dilution liquid chromatography-tandem mass spectrometry (LC-ID-MS/MS) following acid hydrolysis of the protein, in combination with ultraviolet-visible spectrophotometry (UV-Vis) based on tryptophan and tyrosine absorbance at 280 nm. Homogeneity of the material was established through spectrophotometric absorbance readings at 280 nm. Transportation and long-term storage stabilities were assessed by monitoring relative changes in oligomeric state by size-exclusion liquid chromatography (LC-SEC) with UV detection. The molar concentration of the spike protein in SMT1-1 was 5.68 ± 0.22 µmol L-1 (k = 2, 95% CI), with the native trimeric form accounting for ~ 94% of the relative abundance. Reference mass concentration and mass fraction values were calculated using the protein molecular weight and density of the SMT1-1 solution. The spike protein is highly glycosylated which leads to analyte ambiguity when reporting the more commonly used mass concentration. After glycoprotein molar mass determination by LC-SEC with multi-angle light scattering detection, we thus reported mass concentration values for both the protein-only portion and intact glycoprotein as 0.813 ± 0.030 and 1.050 ± 0.068 mg mL-1 (k = 2), respectively.
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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
| | - Joseph D Schrag
- Human Health Therapeutics, National Research Council Canada, 6100 Royalmount Ave, 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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