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Identification of a monoclonal antibody recognizing a B-cell epitope within the nuclear localization signal of porcine circovirus 4 (PCV4) capsid protein.

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Title: Identification of a monoclonal antibody recognizing a B-cell epitope within the nuclear localization signal of porcine circovirus 4 (PCV4) capsid protein.
Authors: Liao JY; Institute of Pathogen Biology and Immunology, College of Biology, Hunan Provincial Key Laboratory of Medical Virology, Hunan University, Changsha 410082, China., Liu XQ; Institute of Pathogen Biology and Immunology, College of Biology, Hunan Provincial Key Laboratory of Medical Virology, Hunan University, Changsha 410082, China., Hou JY; Institute of Pathogen Biology and Immunology, College of Biology, Hunan Provincial Key Laboratory of Medical Virology, Hunan University, Changsha 410082, China., Zhang Q; Institute of Pathogen Biology and Immunology, College of Biology, Hunan Provincial Key Laboratory of Medical Virology, Hunan University, Changsha 410082, China., Zhu F; Institute of Pathogen Biology and Immunology, College of Biology, Hunan Provincial Key Laboratory of Medical Virology, Hunan University, Changsha 410082, China., Shi Y; Institute of Pathogen Biology and Immunology, College of Biology, Hunan Provincial Key Laboratory of Medical Virology, Hunan University, Changsha 410082, China., Xiao CT; Institute of Pathogen Biology and Immunology, College of Biology, Hunan Provincial Key Laboratory of Medical Virology, Hunan University, Changsha 410082, China. Electronic address: xiaocht@126.com.
Source: Veterinary microbiology [Vet Microbiol] 2026 Aug; Vol. 319, pp. 111050. Date of Electronic Publication: 2026 May 04.
Publication Type: Journal Article
Language: English
Journal Info: Publisher: Elsevier Scientific Pub. Co Country of Publication: Netherlands NLM ID: 7705469 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1873-2542 (Electronic) Linking ISSN: 03781135 NLM ISO Abbreviation: Vet Microbiol Subsets: MEDLINE
Imprint Name(s): Original Publication: Amsterdam, Elsevier Scientific Pub. Co.
MeSH Terms: Circovirus*/immunology , Circovirus*/genetics , Antibodies, Monoclonal*/immunology , Nuclear Localization Signals*/immunology , Nuclear Localization Signals*/genetics , Capsid Proteins*/immunology , Capsid Proteins*/genetics , Epitopes, B-Lymphocyte*/immunology , Antibodies, Viral*/immunology, Circoviridae Infections/veterinary ; Circoviridae Infections/virology ; Swine Diseases/virology ; Animals ; Swine ; Mice, Inbred BALB C ; Epitope Mapping ; Humans ; Mice ; HEK293 Cells
Abstract: Porcine circovirus type 4 (PCV4) is an emerging pathogen with a broad geographical distribution, having been detected in both healthy and diseased pigs across China, South Korea, Europe, and other regions. Similar to PCV2, PCV4 rescued from infectious clones has been shown to be pathogenic in pigs, posing a potential threat to the swine industry. The capsid (Cap) protein, the primary structural and immunogenic component of PCV4, contains a nuclear localization signal (NLS) critical for viral replication. However, the immunogenicity and antigenic epitopes of PCV4 Cap protein remain poorly characterized. In this study, the PCV4 Cap protein was expressed and used to immunize BALB/c mice. Four monoclonal antibodies (mAbs) specific to PCV4 Cap were generated through hybridoma technique and screened by indirect ELISA. Western blot and indirect immunofluorescence assays demonstrated that all four mAbs specifically recognized PCV4 Cap protein expressed in both HEK293T cells and Escherichia coli. Subclass typing revealed that the mAbs possessed IgG1 heavy chains and kappa light chains. Epitope mapping using truncated Cap proteins identified a common B-cell epitope recognized by all four mAbs, located within the NLS region corresponding to amino acid residues 28-43. The mAbs exhibited high specificity for PCV4 Cap, with no cross-reactivity against PCV2 or PCV3 Cap proteins. The generation of these PCV4 Cap-specific mAbs provides valuable tools for developing pathogen-specific detection methods to support epidemiological surveillance of PCV4 and for further investigating NLS-associated viral replication mechanisms, particularly those involving nuclear import and export processes.
(Copyright © 2026 Elsevier B.V. All rights reserved.)
Competing Interests: Declaration of Competing Interest The authors declare that they have no competing financial or commercial interests in this work.
Contributed Indexing: Keywords: B-cell epitope; Cap protein; Monoclonal antibodies; Nuclear localization signal (NLS); Porcine circovirus 4 (PCV4)
Substance Nomenclature: 0 (Antibodies, Monoclonal)
0 (Nuclear Localization Signals)
0 (Capsid Proteins)
0 (Epitopes, B-Lymphocyte)
0 (Antibodies, Viral)
Entry Date(s): Date Created: 20260508 Date Completed: 20260605 Latest Revision: 20260605
Update Code: 20260606
DOI: 10.1016/j.vetmic.2026.111050
PMID: 42102598
Database: MEDLINE
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  Data: Identification of a monoclonal antibody recognizing a B-cell epitope within the nuclear localization signal of porcine circovirus 4 (PCV4) capsid protein.
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  Data: <searchLink fieldCode="AU" term="%22Liao+JY%22">Liao JY</searchLink>; Institute of Pathogen Biology and Immunology, College of Biology, Hunan Provincial Key Laboratory of Medical Virology, Hunan University, Changsha 410082, China.<br /><searchLink fieldCode="AU" term="%22Liu+XQ%22">Liu XQ</searchLink>; Institute of Pathogen Biology and Immunology, College of Biology, Hunan Provincial Key Laboratory of Medical Virology, Hunan University, Changsha 410082, China.<br /><searchLink fieldCode="AU" term="%22Hou+JY%22">Hou JY</searchLink>; Institute of Pathogen Biology and Immunology, College of Biology, Hunan Provincial Key Laboratory of Medical Virology, Hunan University, Changsha 410082, China.<br /><searchLink fieldCode="AU" term="%22Zhang+Q%22">Zhang Q</searchLink>; Institute of Pathogen Biology and Immunology, College of Biology, Hunan Provincial Key Laboratory of Medical Virology, Hunan University, Changsha 410082, China.<br /><searchLink fieldCode="AU" term="%22Zhu+F%22">Zhu F</searchLink>; Institute of Pathogen Biology and Immunology, College of Biology, Hunan Provincial Key Laboratory of Medical Virology, Hunan University, Changsha 410082, China.<br /><searchLink fieldCode="AU" term="%22Shi+Y%22">Shi Y</searchLink>; Institute of Pathogen Biology and Immunology, College of Biology, Hunan Provincial Key Laboratory of Medical Virology, Hunan University, Changsha 410082, China.<br /><searchLink fieldCode="AU" term="%22Xiao+CT%22">Xiao CT</searchLink>; Institute of Pathogen Biology and Immunology, College of Biology, Hunan Provincial Key Laboratory of Medical Virology, Hunan University, Changsha 410082, China. Electronic address: xiaocht@126.com.
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  Data: <searchLink fieldCode="JN" term="%227705469%22">Veterinary microbiology</searchLink> [Vet Microbiol] 2026 Aug; Vol. 319, pp. 111050. <i>Date of Electronic Publication: </i>2026 May 04.
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  Data: <i>Publisher: </i><searchLink fieldCode="PB" term="%22Elsevier+Scientific+Pub%2E+Co%22">Elsevier Scientific Pub. Co </searchLink><i>Country of Publication: </i>Netherlands <i>NLM ID: </i>7705469 <i>Publication Model: </i>Print-Electronic <i>Cited Medium: </i>Internet <i>ISSN: </i>1873-2542 (Electronic) <i>Linking ISSN: </i><searchLink fieldCode="IS" term="%2203781135%22">03781135 </searchLink><i>NLM ISO Abbreviation: </i>Vet Microbiol <i>Subsets: </i>MEDLINE
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  Data: <i>Original Publication</i>: Amsterdam, Elsevier Scientific Pub. Co.
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  Data: <searchLink fieldCode="MM" term="%22Circovirus%22">Circovirus*</searchLink>/<searchLink fieldCode="MM" term="%22Circovirus+immunology%22">immunology</searchLink> <br /><searchLink fieldCode="MM" term="%22Circovirus%22">Circovirus*</searchLink>/<searchLink fieldCode="MM" term="%22Circovirus+genetics%22">genetics</searchLink> <br /><searchLink fieldCode="MM" term="%22Antibodies%2C+Monoclonal%22">Antibodies, Monoclonal*</searchLink>/<searchLink fieldCode="MM" term="%22Antibodies%2C+Monoclonal+immunology%22">immunology</searchLink> <br /><searchLink fieldCode="MM" term="%22Nuclear+Localization+Signals%22">Nuclear Localization Signals*</searchLink>/<searchLink fieldCode="MM" term="%22Nuclear+Localization+Signals+immunology%22">immunology</searchLink> <br /><searchLink fieldCode="MM" term="%22Nuclear+Localization+Signals%22">Nuclear Localization Signals*</searchLink>/<searchLink fieldCode="MM" term="%22Nuclear+Localization+Signals+genetics%22">genetics</searchLink> <br /><searchLink fieldCode="MM" term="%22Capsid+Proteins%22">Capsid Proteins*</searchLink>/<searchLink fieldCode="MM" term="%22Capsid+Proteins+immunology%22">immunology</searchLink> <br /><searchLink fieldCode="MM" term="%22Capsid+Proteins%22">Capsid Proteins*</searchLink>/<searchLink fieldCode="MM" term="%22Capsid+Proteins+genetics%22">genetics</searchLink> <br /><searchLink fieldCode="MM" term="%22Epitopes%2C+B-Lymphocyte%22">Epitopes, B-Lymphocyte*</searchLink>/<searchLink fieldCode="MM" term="%22Epitopes%2C+B-Lymphocyte+immunology%22">immunology</searchLink> <br /><searchLink fieldCode="MM" term="%22Antibodies%2C+Viral%22">Antibodies, Viral*</searchLink>/<searchLink fieldCode="MM" term="%22Antibodies%2C+Viral+immunology%22">immunology</searchLink><br /><searchLink fieldCode="MH" term="%22Circoviridae+Infections%22">Circoviridae Infections</searchLink>/<searchLink fieldCode="MH" term="%22Circoviridae+Infections+veterinary%22">veterinary</searchLink> ; <searchLink fieldCode="MH" term="%22Circoviridae+Infections%22">Circoviridae Infections</searchLink>/<searchLink fieldCode="MH" term="%22Circoviridae+Infections+virology%22">virology</searchLink> ; <searchLink fieldCode="MH" term="%22Swine+Diseases%22">Swine Diseases</searchLink>/<searchLink fieldCode="MH" term="%22Swine+Diseases+virology%22">virology</searchLink> ; <searchLink fieldCode="MH" term="%22Animals%22">Animals</searchLink> ; <searchLink fieldCode="MH" term="%22Swine%22">Swine</searchLink> ; <searchLink fieldCode="MH" term="%22Mice%2C+Inbred+BALB+C%22">Mice, Inbred BALB C</searchLink> ; <searchLink fieldCode="MH" term="%22Epitope+Mapping%22">Epitope Mapping</searchLink> ; <searchLink fieldCode="MH" term="%22Humans%22">Humans</searchLink> ; <searchLink fieldCode="MH" term="%22Mice%22">Mice</searchLink> ; <searchLink fieldCode="MH" term="%22HEK293+Cells%22">HEK293 Cells</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Porcine circovirus type 4 (PCV4) is an emerging pathogen with a broad geographical distribution, having been detected in both healthy and diseased pigs across China, South Korea, Europe, and other regions. Similar to PCV2, PCV4 rescued from infectious clones has been shown to be pathogenic in pigs, posing a potential threat to the swine industry. The capsid (Cap) protein, the primary structural and immunogenic component of PCV4, contains a nuclear localization signal (NLS) critical for viral replication. However, the immunogenicity and antigenic epitopes of PCV4 Cap protein remain poorly characterized. In this study, the PCV4 Cap protein was expressed and used to immunize BALB/c mice. Four monoclonal antibodies (mAbs) specific to PCV4 Cap were generated through hybridoma technique and screened by indirect ELISA. Western blot and indirect immunofluorescence assays demonstrated that all four mAbs specifically recognized PCV4 Cap protein expressed in both HEK293T cells and Escherichia coli. Subclass typing revealed that the mAbs possessed IgG1 heavy chains and kappa light chains. Epitope mapping using truncated Cap proteins identified a common B-cell epitope recognized by all four mAbs, located within the NLS region corresponding to amino acid residues 28-43. The mAbs exhibited high specificity for PCV4 Cap, with no cross-reactivity against PCV2 or PCV3 Cap proteins. The generation of these PCV4 Cap-specific mAbs provides valuable tools for developing pathogen-specific detection methods to support epidemiological surveillance of PCV4 and for further investigating NLS-associated viral replication mechanisms, particularly those involving nuclear import and export processes.<br /> (Copyright © 2026 Elsevier B.V. All rights reserved.)
– Name: Abstract
  Label: Competing Interests
  Group: Ab
  Data: Declaration of Competing Interest The authors declare that they have no competing financial or commercial interests in this work.
– Name: SubjectMinor
  Label: Contributed Indexing
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  Data: <i>Keywords: </i>B-cell epitope; Cap protein; Monoclonal antibodies; Nuclear localization signal (NLS); Porcine circovirus 4 (PCV4)
– Name: NumberCAS
  Label: Substance Nomenclature
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  Data: 0 (Antibodies, Monoclonal)<br />0 (Nuclear Localization Signals)<br />0 (Capsid Proteins)<br />0 (Epitopes, B-Lymphocyte)<br />0 (Antibodies, Viral)
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        Value: 10.1016/j.vetmic.2026.111050
    Languages:
      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        StartPage: 111050
    Subjects:
      – SubjectFull: Circoviridae Infections veterinary
        Type: general
      – SubjectFull: Circoviridae Infections virology
        Type: general
      – SubjectFull: Swine Diseases virology
        Type: general
      – SubjectFull: Animals
        Type: general
      – SubjectFull: Swine
        Type: general
      – SubjectFull: Mice, Inbred BALB C
        Type: general
      – SubjectFull: Epitope Mapping
        Type: general
      – SubjectFull: Humans
        Type: general
      – SubjectFull: Mice
        Type: general
      – SubjectFull: HEK293 Cells
        Type: general
      – SubjectFull: Circovirus immunology
        Type: general
      – SubjectFull: Circovirus genetics
        Type: general
      – SubjectFull: Antibodies, Monoclonal immunology
        Type: general
      – SubjectFull: Nuclear Localization Signals immunology
        Type: general
      – SubjectFull: Nuclear Localization Signals genetics
        Type: general
      – SubjectFull: Capsid Proteins immunology
        Type: general
      – SubjectFull: Capsid Proteins genetics
        Type: general
      – SubjectFull: Epitopes, B-Lymphocyte immunology
        Type: general
      – SubjectFull: Antibodies, Viral immunology
        Type: general
    Titles:
      – TitleFull: Identification of a monoclonal antibody recognizing a B-cell epitope within the nuclear localization signal of porcine circovirus 4 (PCV4) capsid protein.
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              Text: 2026 Aug
              Type: published
              Y: 2026
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