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Wen Y, Guo W, Min Y, Zhong K, Zhang X, Xing X, Tong Y, Pan Y, Hong W, Cai W, Yu L. Patient-derived monoclonal antibodies to SARS-CoV-2 nucleocapsid protein N-terminal and C-terminal domains cross-react with their counterparts of SARS-CoV, but not other human betacoronaviruses. Front Immunol 2023; 14:1093709. [PMID: 36798118 PMCID: PMC9927002 DOI: 10.3389/fimmu.2023.1093709] [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: 11/09/2022] [Accepted: 01/17/2023] [Indexed: 02/03/2023] Open
Abstract
Introduction SARS-CoV-2 nucleocapsid (N) protein plays a key role in multiple stages of the viral life cycle such as viral replication and assembly. This protein is more conserved than the Spike protein of the virus and can induce both humoral and cell-mediated immune responses, thereby becoming a target for clinical diagnosis and vaccine development. However, the immunogenic characteristics of this protein during natural infection are still not completely understood. Methods Patient-derived monoclonal antibodies (mAbs) against SARS-CoV-2 N protein were generated from memory B cells in the PBMCs using the antigen-specific B cell approach. For epitope mapping of the isolated hmAbs, a panel of series-truncated N proteins were used , which covered the N-terminal domain (NTD, aa 46-174 ) and C-terminal domain (CTD, aa 245-364 ), as well as the flanking regions of NTD and CTD. NTD- or CTD-specific Abs in the plasma from COVID-19 patients were also tested by ELISA method. Cross-binding of hmAbs or plasma Abs in COVID-19 patients to other human β-CoV N proteins was determined using the capture ELISA. Results We isolated five N-specific monoclonal antibodies (mAbs) from memory B cells in the peripheral blood of two convalescent COVID-19 patients. Epitope mapping revealed that three of the patient-derived mAbs (N3, N5 and N31) targeted the C-terminal domain (CTD), whereas two of the mAbs (N83 and 3B7) targeted the N-terminal domain (NTD) of SARS-CoV-2 N protein. All five patient-derived mAbs were cross-reactive to the N protein of SARS-CoV but showed little to no cross-reactivity to the N proteins of other human beta coronaviruses (β-CoVs). We also tested 52 plasma samples collected from convalescent COVID-19 patients for Abs against the N proteins of human β-CoVs and found that 78.8% of plasma samples showed detectable Abs against the N proteins of SARS-CoV-2 and SARS-CoV. No plasma sample had cross-reactive Abs to the N protein of MERS-CoV. Cross-reactive Abs to the N proteins of OC43 and HKU1 were detected in 36.5% (19/52) and 19.2% (10/52) of plasma samples, respectively. Discussion These results suggest that natural SARS-CoV-2 infection elicits cross-reactive Abs to the N protein of SARS-CoV and that the five patient-derived mAbs to SARS-CoV-2 N protein NTD and CTD cross-react with their counterparts of SARS-CoV, but not other human β-CoVs. Thus, these five patient-derived mAbs can potentially be used for developing the next generation of COVID-19 At-Home Test kits for rapid and specific screening of SARS-CoV-2 infection.
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Affiliation(s)
- Yingfen Wen
- Guangzhou Eighth People's Hospital, Guangzhou Medical University, Guangzhou, China
| | - Wenjing Guo
- Guangzhou Eighth People's Hospital, Guangzhou Medical University, Guangzhou, China
| | - Yuyi Min
- Guangzhou Eighth People's Hospital, Guangzhou Medical University, Guangzhou, China
| | - Kexin Zhong
- Guangzhou Eighth People's Hospital, Guangzhou Medical University, Guangzhou, China
| | - Xulei Zhang
- Guangzhou Eighth People's Hospital, Guangzhou Medical University, Guangzhou, China
| | - Xiaomin Xing
- Guangzhou Eighth People's Hospital, Guangzhou Medical University, Guangzhou, China
| | - Yuwei Tong
- Guangzhou Eighth People's Hospital, Guangzhou Medical University, Guangzhou, China
| | - Yuejun Pan
- Guangzhou Eighth People's Hospital, Guangzhou Medical University, Guangzhou, China
| | - Wenxin Hong
- Guangzhou Eighth People's Hospital, Guangzhou Medical University, Guangzhou, China
| | - Weiping Cai
- Guangzhou Eighth People's Hospital, Guangzhou Medical University, Guangzhou, China
| | - Lei Yu
- Guangzhou Eighth People's Hospital, Guangzhou Medical University, Guangzhou, China
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Tajuelo A, López-Siles M, Más V, Pérez-Romero P, Aguado JM, Briz V, McConnell MJ, Martín-Galiano AJ, López D. Cross-Recognition of SARS-CoV-2 B-Cell Epitopes with Other Betacoronavirus Nucleoproteins. Int J Mol Sci 2022; 23:ijms23062977. [PMID: 35328398 PMCID: PMC8955325 DOI: 10.3390/ijms23062977] [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: 02/08/2022] [Accepted: 02/21/2022] [Indexed: 02/01/2023] Open
Abstract
The B and T lymphocytes of the adaptive immune system are important for the control of most viral infections, including COVID-19. Identification of epitopes recognized by these cells is fundamental for understanding how the immune system detects and removes pathogens, and for antiviral vaccine design. Intriguingly, several cross-reactive T lymphocyte epitopes from SARS-CoV-2 with other betacoronaviruses responsible for the common cold have been identified. In addition, antibodies that cross-recognize the spike protein, but not the nucleoprotein (N protein), from different betacoronavirus have also been reported. Using a consensus of eight bioinformatic methods for predicting B-cell epitopes and the collection of experimentally detected epitopes for SARS-CoV and SARS-CoV-2, we identified four surface-exposed, conserved, and hypothetical antigenic regions that are exclusive of the N protein. These regions were analyzed using ELISA assays with two cohorts: SARS-CoV-2 infected patients and pre-COVID-19 samples. Here we describe four epitopes from SARS-CoV-2 N protein that are recognized by the humoral response from multiple individuals infected with COVID-19, and are conserved in other human coronaviruses. Three of these linear surface-exposed sequences and their peptide homologs in SARS-CoV-2 and HCoV-OC43 were also recognized by antibodies from pre-COVID-19 serum samples, indicating cross-reactivity of antibodies against coronavirus N proteins. Different conserved human coronaviruses (HCoVs) cross-reactive B epitopes against SARS-CoV-2 N protein are detected in a significant fraction of individuals not exposed to this pandemic virus. These results have potential clinical implications.
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Affiliation(s)
- Ana Tajuelo
- Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Madrid, Spain; (A.T.); (M.L.-S.); (V.M.); (P.P.-R.); (V.B.); (A.J.M.-G.)
| | - Mireia López-Siles
- Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Madrid, Spain; (A.T.); (M.L.-S.); (V.M.); (P.P.-R.); (V.B.); (A.J.M.-G.)
| | - Vicente Más
- Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Madrid, Spain; (A.T.); (M.L.-S.); (V.M.); (P.P.-R.); (V.B.); (A.J.M.-G.)
| | - Pilar Pérez-Romero
- Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Madrid, Spain; (A.T.); (M.L.-S.); (V.M.); (P.P.-R.); (V.B.); (A.J.M.-G.)
| | | | - Verónica Briz
- Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Madrid, Spain; (A.T.); (M.L.-S.); (V.M.); (P.P.-R.); (V.B.); (A.J.M.-G.)
| | - Michael J. McConnell
- Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Madrid, Spain; (A.T.); (M.L.-S.); (V.M.); (P.P.-R.); (V.B.); (A.J.M.-G.)
- Correspondence: (M.J.M.); (D.L.)
| | - Antonio J. Martín-Galiano
- Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Madrid, Spain; (A.T.); (M.L.-S.); (V.M.); (P.P.-R.); (V.B.); (A.J.M.-G.)
| | - Daniel López
- Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Madrid, Spain; (A.T.); (M.L.-S.); (V.M.); (P.P.-R.); (V.B.); (A.J.M.-G.)
- Correspondence: (M.J.M.); (D.L.)
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Ezhilan M, Suresh I, Nesakumar N. SARS-CoV, MERS-CoV and SARS-CoV-2: A Diagnostic Challenge. MEASUREMENT : JOURNAL OF THE INTERNATIONAL MEASUREMENT CONFEDERATION 2021; 168:108335. [PMID: 33519010 PMCID: PMC7833337 DOI: 10.1016/j.measurement.2020.108335] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 07/20/2020] [Accepted: 08/01/2020] [Indexed: 05/15/2023]
Abstract
The highly pathogenic MERS-CoV, SARS-CoV and SARS-CoV-2 cause acute respiratory syndrome and are often fatal. These new viruses pose major problems to global health in general and primarily to infection control and public health services. Accurate and selective assessment of MERS-CoV, SARS-CoV and SARS-CoV-2 would assist in the effective diagnosis of infected individual, offer clinical guidance and aid in assessing clinical outcomes. In this mini-review, we review the literature on various aspects, including the history and diversity of SARS-CoV-2, SARS-CoV and MERS-CoV, their detection methods in effective clinical diagnosis, clinical assessment of COVID-19, safety guidelines recommended by World Health Organization and legal regulations. This review article also deals with existing challenges and difficulties in the clinical diagnosis of SARS-CoV-2. Developing alternative diagnostic platforms by spotting the shortcomings of the existing point-of-care diagnostic devices would be useful in preventing future outbreaks.
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Affiliation(s)
- Madeshwari Ezhilan
- School of Electrical and Electronics Engineering, Centre for Nanotechnology & Advanced Biomaterials (CeNTAB), SASTRA Deemed University, Thanjavur 613401, Tamil Nadu, India
| | - Indhu Suresh
- School of Electrical and Electronics Engineering, Centre for Nanotechnology & Advanced Biomaterials (CeNTAB), SASTRA Deemed University, Thanjavur 613401, Tamil Nadu, India
| | - Noel Nesakumar
- School of Chemical and Biotechnology, Centre for Nanotechnology & Advanced Biomaterials (CeNTAB), SASTRA Deemed University, Thanjavur 613401, Tamil Nadu, India
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Shahrajabian MH, Sun W, Cheng Q. Product of natural evolution (SARS, MERS, and SARS-CoV-2); deadly diseases, from SARS to SARS-CoV-2. Hum Vaccin Immunother 2021; 17:62-83. [PMID: 32783700 PMCID: PMC7872062 DOI: 10.1080/21645515.2020.1797369] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 06/24/2020] [Accepted: 07/10/2020] [Indexed: 12/13/2022] Open
Abstract
SARS-CoV-2, the virus causing COVID-19, is a single-stranded RNA virus belonging to the order Nidovirales, family Coronaviridae, and subfamily Coronavirinae. SARS-CoV-2 entry to cellsis initiated by the binding of the viral spike protein (S) to its cellular receptor. The roles of S protein in receptor binding and membrane fusion makes it a prominent target for vaccine development. SARS-CoV-2 genome sequence analysis has shown that this virus belongs to the beta-coronavirus genus, which includes Bat SARS-like coronavirus, SARS-CoV and MERS-CoV. A vaccine should induce a balanced immune response to elicit protective immunity. In this review, we compare and contrast these three important CoV diseases and how they inform on vaccine development.
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Affiliation(s)
| | - Wenli Sun
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Qi Cheng
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China
- College of Life Sciences, Hebei Agricultural University, Baoding, Hebei, China
- Global Alliance of HeBAU-CLS&HeQiS for BioAl-Manufacturing, Baoding, Hebei, China
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Corral-Lugo A, López-Siles M, López D, McConnell MJ, Martin-Galiano AJ. Identification and Analysis of Unstructured, Linear B-Cell Epitopes in SARS-CoV-2 Virion Proteins for Vaccine Development. Vaccines (Basel) 2020; 8:E397. [PMID: 32698423 PMCID: PMC7564417 DOI: 10.3390/vaccines8030397] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 07/14/2020] [Accepted: 07/17/2020] [Indexed: 12/13/2022] Open
Abstract
The efficacy of SARS-CoV-2 nucleic acid-based vaccines may be limited by proteolysis of the translated product due to anomalous protein folding. This may be the case for vaccines employing linear SARS-CoV-2 B-cell epitopes identified in previous studies since most of them participate in secondary structure formation. In contrast, we have employed a consensus of predictors for epitopic zones plus a structural filter for identifying 20 unstructured B-cell epitope-containing loops (uBCELs) in S, M, and N proteins. Phylogenetic comparison suggests epitope switching with respect to SARS-CoV in some of the identified uBCELs. Such events may be associated with the reported lack of serum cross-protection between the 2003 and 2019 pandemic strains. Incipient variability within a sample of 1639 SARS-CoV-2 isolates was also detected for 10 uBCELs which could cause vaccine failure. Intermediate stages of the putative epitope switch events were observed in bat coronaviruses in which additive mutational processes possibly facilitating evasion of the bat immune system appear to have taken place prior to transfer to humans. While there was some overlap between uBCELs and previously validated SARS-CoV B-cell epitopes, multiple uBCELs had not been identified in prior studies. Overall, these uBCELs may facilitate the development of biomedical products for SARS-CoV-2.
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Affiliation(s)
- Andrés Corral-Lugo
- Intrahospital Infections Unit, National Centre for Microbiology, Instituto de Salud Carlos III (ISCIII), 28220 Madrid, Spain; (A.C.-L.); (M.L.-S.)
| | - Mireia López-Siles
- Intrahospital Infections Unit, National Centre for Microbiology, Instituto de Salud Carlos III (ISCIII), 28220 Madrid, Spain; (A.C.-L.); (M.L.-S.)
| | - Daniel López
- Immune Presentation and Regulation Unit, Instituto de Salud Carlos III, 28220 Madrid, Spain;
| | - Michael J. McConnell
- Intrahospital Infections Unit, National Centre for Microbiology, Instituto de Salud Carlos III (ISCIII), 28220 Madrid, Spain; (A.C.-L.); (M.L.-S.)
| | - Antonio J. Martin-Galiano
- Intrahospital Infections Unit, National Centre for Microbiology, Instituto de Salud Carlos III (ISCIII), 28220 Madrid, Spain; (A.C.-L.); (M.L.-S.)
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Synthesis and evaluation of artificial antigens for astragaloside IV. REVISTA BRASILEIRA DE FARMACOGNOSIA-BRAZILIAN JOURNAL OF PHARMACOGNOSY 2014. [DOI: 10.1016/j.bjp.2014.07.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Li XB, Yang W, Zhang Y, Zhang ZG, Kong T, Li DN, Tang JJ, Liu L, Liu GW, Wang Z. Preparation and identification of monoclonal antibody against abrin-a. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2011; 59:9796-9799. [PMID: 21870856 DOI: 10.1021/jf202534y] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
BALB/c mice were immunized four times with formalin-prepared abrin-a. Using the polyethylene glycol method, immunized splenocytes were isolated and fused with SP2/0 cells. An indirect ELISA was established and used to detect positive clones secreting monoclonal antibodies (mAbs) against abrin-a. After analysis, three hybridoma clones secreting IgG-subtype mAbs were obtained. The antibodies were purified from the hybridoma growth medium using protein A or G affinity chromatography. Western blot analysis was used to analyze the antigenic epitopes on abrin-a recognized by the mAbs. The mAbs were specific for abrin-a, with no detectable cross-reactivity with several homologous toxins and associated agglutinins. Sandwich ELISA was then developed using these mAbs, which had a detection limit for abrin-a of 7.8 ng/mL.
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Affiliation(s)
- Xiao-Bing Li
- College of Animal Science and Veterinary Medicine, Jilin University, 5333 Xi'an Road, Changchun 130062, People's Republic of China
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Lee HK, Lee BH, Seok SH, Baek MW, Lee HY, Kim DJ, Na YR, Noh KJ, Park SH, Kumar DN, Kariwa H, Nakauchi M, Heo SJ, Park JH. Production of specific antibodies against SARS-coronavirus nucleocapsid protein without cross reactivity with human coronaviruses 229E and OC43. J Vet Sci 2011; 11:165-7. [PMID: 20458159 PMCID: PMC2873818 DOI: 10.4142/jvs.2010.11.2.165] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Severe acute respiratory syndrome (SARS) is a life-threatening disease for which accurate diagnosis is essential. Although many tools have been developed for the diagnosis of SARS, false-positive reactions in negative sera may occur because of cross-reactivity with other coronaviruses. We have raised polyclonal and monoclonal antibodies (Abs) using a recombinant form of the SARS virus nucleocapsid protein. Cross-reactivity of these anti-SARS Abs against human coronavirus (HCoV) 229E and HCoV OC43 were determined by Western blotting. The Abs produced reacted with recombinant SARS virus nucleocapsid protein, but not with HCoV 229E or HCoV OC43.
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Affiliation(s)
- Hyun Kyoung Lee
- Department of Laboratory Animal Medicine, College of Veterinary Medicine, Seoul National University, Seoul 151-742, Korea
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Liu J, Liu B, Cao Z, Inoue S, Morita K, Tian K, Zhu Q, Gao GF. Characterization and application of monoclonal antibodies specific to West Nile virus envelope protein. J Virol Methods 2008; 154:20-6. [PMID: 18948139 PMCID: PMC7112808 DOI: 10.1016/j.jviromet.2008.09.019] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2008] [Revised: 09/05/2008] [Accepted: 09/11/2008] [Indexed: 11/28/2022]
Abstract
Recent epidemics of West Nile virus (WNV) around the world have been associated with significant rates of mortality and morbidity in humans. To develop standard WNV diagnostic tools that can differentiate WNV from Japanese encephalitis virus (JEV), four monoclonal antibodies (MAbs) specific to WNV envelope (E) protein were produced and characterized by isotyping, reactivity with denatured and native antigens, affinity assay, immunofluorescence assay (IFA), and epitope competition, as well as cross-reactivity with JEV. Two of the MAbs (6A11 and 4B3) showed stronger reactivity with E protein than the others (2F5 and 6H7) in Western blot analysis. 4B3 could bind with denatured antigen, as well as native antigens in indirect ELISA, flow cytometry analysis, and IFA; whereas 2F5 showed highest affinity with native antigen. 4B3 and 2F5 were therefore used to establish an antigen capture-ELISA (AC-ELISA) detection system. The sensitivity of this AC-ELISA was 3.95 TCID50/0.1 ml for WNV-infected cell culture supernatant. Notably, these MAbs showed no cross-reactivity with JEV, which suggests that they are useful for further development of highly sensitive, easy handling, and less time-consuming detection kits/tools in WNV surveillance in areas where JEV is epidemic.
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Affiliation(s)
- June Liu
- Center for Molecular Immunology and Center for Molecular Virology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
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Cheung YK, Cheng SCS, Sin FWY, Chan KT, Xie Y. Induction of T-cell response by a DNA vaccine encoding a novel HLA-A*0201 severe acute respiratory syndrome coronavirus epitope. Vaccine 2007; 25:6070-7. [PMID: 17629360 PMCID: PMC7115375 DOI: 10.1016/j.vaccine.2007.05.025] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2007] [Revised: 05/03/2007] [Accepted: 05/12/2007] [Indexed: 12/23/2022]
Abstract
The severe acute respiratory syndrome coronavirus nucleocapsid protein (SARS-CoV N) is one of the major targets for SARS vaccine due to its high potency in triggering immune responses. In this study, we have identified a novel HLA-A*0201 restricted epitope, N220 (LALLLLDRL), of the SARS-CoV N-protein through bioinformatics analysis. The N-protein peptide N220 shows a high binding affinity towards human MHC class I in T2-cells, and is capable of activating cytotoxic T-cells in human peripheral blood mononuclear cells (PBMCs). The application of using the N220 peptide sequence with a single-chain-trimer (SCT) approach to produce a potential DNA vaccine candidate was investigated in HLA-A2.1K(b) transgenic mice. Cytotoxicity assay clearly showed that the T-cells obtained from the vaccinated animals were able to kill the N-protein expressing cells with a cytotoxicity level of 86% in an effector cells/target cells ratio of 81:1 one week after the last vaccination, which is significantly higher than other N-protein peptides previously described. The novel immunogenic N-protein peptide revealed in the present study provides valuable information for therapeutic SARS vaccine design.
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Affiliation(s)
| | | | | | | | - Yong Xie
- Department of Biology, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR, China
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Shin GC, Chung YS, Kim IS, Cho HW, Kang C. Antigenic characterization of severe acute respiratory syndrome-coronavirus nucleocapsid protein expressed in insect cells: The effect of phosphorylation on immunoreactivity and specificity. Virus Res 2007; 127:71-80. [PMID: 17499376 PMCID: PMC7114200 DOI: 10.1016/j.virusres.2007.03.019] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2006] [Revised: 03/19/2007] [Accepted: 03/21/2007] [Indexed: 12/13/2022]
Abstract
The nucleocapsid (N) protein of severe acute respiratory syndrome-coronavirus (SARS-CoV) is involved in the pathological reaction to SARS and is a key antigen for the development of a sensitive diagnostic assay. However, the antigenic properties of this N protein are largely unknown. To facilitate the studies on the function and antigenicity of the SARS-CoV N protein, 6x histidine-tagged recombinant SARS-CoV N (rSARS-N) with a molecular mass of 46 and 48kDa was successfully produced using the recombinant baculovirus system in insect cells. The rSARS-N expressed in insect cells (BrSARS-N) showed remarkably higher specificity and immunoreactivity than rSARS-N expressed in E. coli (ErSARS-N). Most of all, BrSARS-N proteins were expressed as a highly phosphorylated form with a molecular mass of 48kDa, but ErSARS-N was a nonphosphorylated protein. In further analysis to determine the correlation between the phosphorylation and the antigenicity of SARS-N protein, dephosphorylated SARS-N protein treated with protein phosphatase 1 (PP1) remarkably enhanced the cross-reactivity against SARS negative serum and considerably reduced immunoreactivity with SARS-N mAb. These results suggest that the phosphorylation plays an important role in the immunoreactivity and specificity of SARS-N protein. Therefore, the BrSARS-N protein may be useful for the development of highly sensitive and specific assays to determine SARS infection and for further research of SARS-N pathology.
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Affiliation(s)
| | | | | | | | - Chun Kang
- Corresponding author. Tel.: +82 2 380 1501; fax: +82 2 389 2014.
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