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Veterinary research2025; 56(1); 12; doi: 10.1186/s13567-024-01434-3

Genomic analysis and replication kinetics of the closely related EHV-1 neuropathogenic 21P40 and abortigenic 97P70 strains.

Abstract: Varicellovirus equidalpha 1, formerly known as Equid alphaherpesvirus 1 (EHV-1), is highly prevalent and can lead to various problems, such as respiratory problems, abortion, neonatal foal death, and neurological disorders. The latter is known as equine herpes myeloencephalopathy (EHM). Cases of EHM have significantly increased since the beginning of the twenty-first century. The genomic sequences of five isolates associated with the fatal neurological outbreak in Valencia, Spain, in 2021 were analyzed and documented. The genome and replication kinetics of the Belgian EHM isolate 21P40, associated with the Valencia outbreak, and the well-characterized abortigenic strain 97P70 were compared. Both strains exhibited a nucleotide identity of 99.96%, with only seven genetic mutations in ORFs 13, 24, 30, 32, 40, 65, and 71. Isoleucine and asparagine at loci 291 and 207 of ORF30 (DNA polymerase) and ORF65 (ICP22), respectively, were unique to isolates from the Valencia outbreak. The replication kinetics of these two genetically closely related strains were determined in rabbit kidney (RK-13), equine respiratory, and vaginal mucosal explant cells, as well as equine blood monocytes (CD172a). Both strains replicated equally well in RK-13 cells. The neuropathogenic isolate 21P40 exhibited a more extensive infection in respiratory explants and blood monocytes, as demonstrated by more plaques and single infected leukocytes, and a higher percentage of infected monocytes. In contrast, vaginal explants infected with the abortigenic strain 97P70 demonstrated more plaques and single infected leukocytes. In conclusion, 21P40 replicated significantly different compared to 97P70 but shared similarities with the Belgian well-studied neuropathogenic EHV-1 strain 03P37.
© 2025. The Author(s).
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Publication Date: 2025-01-13 PubMed ID: 39806433PubMed Central: PMC11731145DOI: 10.1186/s13567-024-01434-3Google Scholar: Lookup
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  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Overview

  • This research compares the genetic makeup and replication behavior of two closely related strains of Equid alphaherpesvirus 1 (EHV-1), one associated with neurological disease outbreaks and the other with abortion in horses.
  • The study aims to understand genetic differences and replication patterns that could explain variations in disease outcomes caused by these viral strains.

Background

  • Equid alphaherpesvirus 1 (EHV-1) is a common virus affecting horses worldwide.
  • EHV-1 infections can cause respiratory illness, abortion during pregnancy, death of newborn foals, and neurological disease known as equine herpes myeloencephalopathy (EHM).
  • There has been a notable rise in EHM cases since the early 2000s.
  • The study focuses on two strains: the neuropathogenic 21P40 strain linked to a fatal neurological outbreak in Valencia, Spain in 2021, and the abortigenic strain 97P70, known for causing abortions.

Genomic Analysis

  • Researchers sequenced the genomes of five viral isolates from the 2021 Valencia EHM outbreak.
  • The genomes of strain 21P40 (neuropathogenic) and 97P70 (abortigenic) were compared.
  • Both strains showed 99.96% nucleotide identity, indicating they are extremely similar genetically.
  • Only seven mutations were found in specific open reading frames (ORFs 13, 24, 30, 32, 40, 65, and 71).
  • Unique amino acid changes were identified in ORF30 (DNA polymerase) and ORF65 (ICP22) associated with the neuropathogenic Valencia isolates:
    • Isoleucine at position 291 in ORF30
    • Asparagine at position 207 in ORF65
  • These mutations may be linked to the neuropathogenic properties of the 21P40 strain.

Replication Kinetics Study

  • Replication of 21P40 and 97P70 was tested in various cell types relevant to infection:
    • Rabbit kidney cells (RK-13)
    • Equine respiratory mucosal explants
    • Equine vaginal mucosal explants
    • Equine blood monocytes (CD172a+)
  • Findings:
    • Both strains replicated similarly in RK-13 cells, showing equal growth in this non-equine cell line.
    • In equine respiratory explants and blood monocytes, the neuropathogenic strain 21P40 caused more infection, indicated by more plaques, more infected leukocytes, and a higher percentage of infected monocytes.
    • Conversely, the 97P70 abortigenic strain showed higher replication in vaginal mucosal explants.

Conclusions and Implications

  • Despite high genetic similarity, 21P40 and 97P70 demonstrate significant differences in how they replicate in different equine tissues.
  • The unique genetic mutations in the neuropathogenic strain may help explain its enhanced ability to infect respiratory tissue and blood immune cells, which could contribute to neurological disease development.
  • The abortigenic strain’s preference for vaginal tissue replication aligns with its role in causing abortion.
  • The neuropathogenic strain 21P40 shares replication characteristics with another known Belgian neuropathogenic strain (03P37), supporting the idea of specific viral traits linked to disease outcomes.
  • Understanding these differences at the genomic and replication levels is crucial for developing targeted prevention and treatment strategies for EHV-1 associated diseases, including EHM and abortion in horses.

Cite This Article

APA
Mohamed E, Zarak I, Vereecke N, Theuns S, Laval K, Nauwynck H. (2025). Genomic analysis and replication kinetics of the closely related EHV-1 neuropathogenic 21P40 and abortigenic 97P70 strains. Vet Res, 56(1), 12. https://doi.org/10.1186/s13567-024-01434-3

Publication

Veterinary research
ISSN: 1297-9716
NlmUniqueID: 9309551
Country: England
Language: English
Volume: 56
Issue: 1
Pages: 12
PII: 12

Researcher Affiliations

Mohamed, Eslam
  • Department of Translational Physiology, Infectiology and Public Health, Faculty of Veterinary Medicine, Ghent University, 9820, Merelbeke, Belgium. eslam.elhanafy@ugent.be.
  • Department of Animal Medicine, Faculty of Veterinary Medicine, Benha University, Moshtohor, 13736, Egypt. eslam.elhanafy@ugent.be.
Zarak, Ines
  • Department of Translational Physiology, Infectiology and Public Health, Faculty of Veterinary Medicine, Ghent University, 9820, Merelbeke, Belgium.
Vereecke, Nick
  • Department of Translational Physiology, Infectiology and Public Health, Faculty of Veterinary Medicine, Ghent University, 9820, Merelbeke, Belgium.
  • PathoSense BV, Pastoriestraat 10, 2500, Lier, Belgium.
Theuns, Sebastiaan
  • PathoSense BV, Pastoriestraat 10, 2500, Lier, Belgium.
Laval, Kathlyn
  • Department of Translational Physiology, Infectiology and Public Health, Faculty of Veterinary Medicine, Ghent University, 9820, Merelbeke, Belgium.
Nauwynck, Hans
  • Department of Translational Physiology, Infectiology and Public Health, Faculty of Veterinary Medicine, Ghent University, 9820, Merelbeke, Belgium.

MeSH Terms

  • Herpesvirus 1, Equid / physiology
  • Herpesvirus 1, Equid / genetics
  • Horses
  • Animals
  • Horse Diseases / virology
  • Horse Diseases / epidemiology
  • Virus Replication
  • Herpesviridae Infections / veterinary
  • Herpesviridae Infections / virology
  • Herpesviridae Infections / epidemiology
  • Genome, Viral
  • Spain / epidemiology
  • Rabbits
  • Kinetics
  • Female

Grant Funding

  • GOA013-17 / Universiteit Gent
  • G035920N / Fonds Wetenschappelijk Onderzoek
  • PhD Scholarship / Ministry of Higher Education
  • HBC.2020.2889 / Agentschap Innoveren en Ondernemen

Conflict of Interest Statement

Declarations. Competing interests: The authors declare that they have no competing interests.

References

This article includes 52 references
  1. Telford EAR, Watson MS, McBride K, Davison AJ. The DNA sequence of equine herpesvirus-1. Virology 189:304–316.
    pubmed: 1318606
  2. Oladunni FS, Horohov DW, Chambers TM. EHV-1: a constant threat to the horse industry. Front Microbiol 10:2668.
    pmc: PMC6901505pubmed: 31849857
  3. Caughman GB, Staczek J, O’Callaghan DJ. Equine herpesvirus type 1 infected cell polypeptides: evidence for immediate early/early/late regulation of viral gene expression. Virology 145:49–61.
    pubmed: 2990102
  4. Gray WL, Baumann RP, Robertson AT, Caughman GB, O’Callaghan DJ, Staczek J. Regulation of equine herpesvirus type 1 gene expression: characterization of immediate early, early, and late transcription. Virology 158:79–87.
    pubmed: 3033896
  5. Bowles DE, Holden VR, Zhao Y, O’Callaghan DJ. The ICP0 protein of equine herpesvirus 1 is an early protein that independently transactivates expression of all classes of viral promoters. J Virol 71:4904–4914.
    pmc: PMC191720pubmed: 9188552
  6. Bowles DE, Kim SK, O’Callaghan DJ. Characterization of the -activation properties of equine herpesvirus 1 EICP0 protein. J Virol 74:1200–1208.
    pmc: PMC111454pubmed: 10627530
  7. Buczynski KA, Kim SK, O’Callaghan DJ. Characterization of the transactivation domain of the equine herpesvirus type 1 immediate-early protein. Virus Res 65:131–140.
    pubmed: 10581386
  8. Derbigny WA, Kim SK, Jang HK, O’Callaghan DJ. EHV-1 EICP22 protein sequences that mediate its physical interaction with the immediate-early protein are not sufficient to enhance the trans-activation activity of the IE protein. Virus Res 84:1–15.
    pubmed: 11900834
  9. Ostlund EN. The equine herpesviruses. Vet Clin North Am Equine Pract 9:283–294.
    pubmed: 8395324
  10. Pusterla N, Hussey GS, Goehring LS. Equine herpesvirus-1 myeloencephalopathy. Vet Clin N Am Equine Pract 38:339–362.
    pubmed: 35811201
  11. McFadden AMJ, Hanlon D, McKenzie RK, Gibson I, Bueno IM, Pulford DJ, Orr D, Dunowska M, Stanislawek WL, Spence RP, McDonald WL, Munro G, Mayhew IG. The first reported outbreak of equine herpesvirus myeloencephalopathy in New Zealand. N Z Vet J 64:125–134.
    pubmed: 26414406
  12. Pusterla N, Barnum S, Miller J, Varnell S, Dallap-Schaer B, Aceto H, Simeone A. Investigation of an EHV-1 outbreak in the United States caused by a new H752 genotype. Pathogens 10:747.
    pmc: PMC8231618pubmed: 34199153
  13. Vereecke N, Carnet F, Pronost S, Vanschandevijl K, Theuns S, Nauwynck H. Genome sequences of equine herpesvirus 1 strains from a European outbreak of neurological disorders linked to a horse gathering in Valencia, Spain, in 2021. Microbiol Resour Announc 10:e00333-e421.
    pmc: PMC8188346pubmed: 34016681
  14. Tong P, Duan R, Palidan N, Deng H, Duan L, Ren M, Song X, Jia C, Tian S, Yang E, Kuang L, Xie J. Outbreak of neuropathogenic equid herpesvirus 1 causing abortions in Yili horses of Zhaosu, North Xinjiang, China. BMC Vet Res 18:83.
    pmc: PMC8886757pubmed: 35232435
  15. Termine C, Akerstrom G, Paixão G. Management of an EHV-1 outbreak at FEI events and its international impact. Vet Rec 189:e905.
    pubmed: 34505682
  16. Nugent J, Birch-Machin I, Smith KC, Mumford JA, Swann Z, Newton JR, Bowden RJ, Allen GP, Davis-Poynter N. Analysis of equid herpesvirus 1 strain variation reveals a point mutation of the DNA polymerase strongly associated with neuropathogenic versus nonneuropathogenic disease outbreaks.. J Virol 80:4047–4060.
    pmc: PMC1440451pubmed: 16571821
  17. Goodman LB, Wagner B, Flaminio MJBF, Sussman KH, Metzger SM, Holland R, Osterrieder N. Comparison of the efficacy of inactivated combination and modified-live virus vaccines against challenge infection with neuropathogenic equine herpesvirus type 1 (EHV-1).. Vaccine 24:3636–3645.
    pubmed: 16513225
  18. Van de Walle GR, Goupil R, Wishon C, Damiani A, Perkins GA, Osterrieder N. A single-nucleotide polymorphism in a herpesvirus DNA polymerase is sufficient to cause lethal neurological disease.. J Infect Dis 200:20–25.
    pubmed: 19456260
  19. Sutton G, Garvey M, Cullinane A, Jourdan M, Fortier C, Moreau P, Foursin M, Gryspeerdt A, Maisonnier V, Marcillaud-Pitel C, Legrand L, Paillot R, Pronost S. Molecular surveillance of EHV-1 strains circulating in France during and after the major 2009 outbreak in Normandy involving respiratory infection, neurological disorder, and abortion.. Viruses 11:916.
    pmc: PMC6832873pubmed: 31590336
  20. Smith KL, Allen GP, Branscum AJ, Frank Cook R, Vickers ML, Timoney PJ, Balasuriya UBR. The increased prevalence of neuropathogenic strains of EHV-1 in equine abortions.. Vet Microbiol 141:5–11.
    pubmed: 19733451
  21. Perkins GA, Goodman LB, Tsujimura K, Van De Walle GR, Kim SG, Dubovi EJ, Osterrieder N. Investigation of the prevalence of neurologic equine herpes virus type 1 (EHV-1) in a 23-year retrospective analysis (1984–2007).. Vet Microbiol 139:375–378.
    pubmed: 19615831
  22. van der Meulen KM, Nauwynck HJ, Buddaert W, Pensaert MB. Replication of equine herpesvirus type 1 in freshly isolated equine peripheral blood mononuclear cells and changes in susceptibility following mitogen stimulation.. J Gen Virol 81:21–25.
    pubmed: 10640538
  23. Vandekerckhove A, Glorieux S, Broeck WVD, Gryspeerdt A, van der Meulen KM, Nauwynck HJ. In vitro culture of equine respiratory mucosa explants.. Vet J 181:280–287.
    pubmed: 18539059
  24. Negussie H, Li Y, Tessema TS, Nauwynck HJ. Replication characteristics of equine herpesvirus 1 and equine herpesvirus 3: comparative analysis using ex vivo tissue cultures.. Vet Res 47:19.
    pmc: PMC4714513pubmed: 26768993
  25. van der Meulen KM, Nauwynck HJ, Pensaert MB. Absence of viral antigens on the surface of equine herpesvirus-1-infected peripheral blood mononuclear cells: a strategy to avoid complement-mediated lysis.. J Gen Virol 84:93–97.
    pubmed: 12533704
  26. Nauwynck HJ, Pensaert MB. Effect of specific antibodies on the cell-associated spread of pseudorabies virus in monolayers of different cell types.. Arch Virol 140:1137–1146.
    pubmed: 7611884
  27. Reed LJ, Muench H. A simple method of estimating fifty per cent endpoints.. Am J Hyg 27:493–497.
  28. Henninger RW, Reed SM, Saville WJ, Allen GP, Hass GF, Kohn CW, Sofaly C. Outbreak of neurologic disease caused by equine herpesvirus-1 at a University Equestrian Center.. J Vet Intern Med 21:157–165.
    pubmed: 17338164
  29. Tsujimura K, Oyama T, Katayama Y, Muranaka M, Bannai H, Nemoto M, Yamanaka T, Kondo T, Kato M, Matsumura T. Prevalence of equine herpesvirus type 1 strains of neuropathogenic genotype in a major breeding area of Japan.. J Vet Med Sci 73:1663–1667.
    pubmed: 21828961
  30. Burgess BA, Tokateloff N, Manning S, Lohmann K, Lunn DP, Hussey SB, Morley PS. Nasal shedding of equine herpesvirus-1 from horses in an outbreak of equine herpes myeloencephalopathy in Western Canada.. J Vet Intern Med 26:384–392.
    pubmed: 22332764
  31. Pronost S, Legrand L, Pitel P-H, Wegge B, Lissens J, Freymuth F, Richard E, Fortier G. Outbreak of equine herpesvirus myeloencephalopathy in France: a clinical and molecular investigation.. Transbound Emerg Dis 59:256–263.
    pubmed: 21975071
  32. Traub-Dargatz JL, Pelzel-McCluskey AM, Creekmore LH, Geiser-Novotny S, Kasari TR, Wiedenheft AM, Bush EJ, Bjork KE. Case–control study of a multistate equine herpesvirus myeloencephalopathy outbreak.. J Vet Intern Med 27:339–346.
    pubmed: 23398291
  33. Walter J, Seeh C, Fey K, Bleul U, Osterrieder N. Clinical observations and management of a severe equine herpesvirus type 1 outbreak with abortion and encephalomyelitis.. Acta Vet Scand 55:19.
    pmc: PMC3630004pubmed: 23497661
  34. Estell KE, Dawson DR, Magdesian KG, Swain E, Laing ST, Siso S, Mapes S, Pusterla N. Quantitative molecular viral loads in 7 horses with naturally occurring equine herpesvirus-1 infection.. Equine Vet J 47:689–693.
    pubmed: 25212737
  35. van Galen G, Leblond A, Tritz P, Martinelle L, Pronost S, Saegerman C. A retrospective study on equine herpesvirus type-1 associated myeloencephalopathy in France (2008–2011).. Vet Microbiol 179:304–309.
    pubmed: 26228835
  36. Negussie H, Gizaw D, Tessema TS, Nauwynck HJ. Equine herpesvirus-1 myeloencephalopathy, an emerging threat of working equids in Ethiopia.. Transbound Emerg Dis 64:389–397.
    pubmed: 26010868
  37. Allen GP, Breathnach CC. Quantification by real-time PCR of the magnitude and duration of leucocyte-associated viraemia in horses infected with neuropathogenic vs. non-neuropathogenic strains of EHV- 1.. Equine Vet J 38:252–257.
    pubmed: 16706281
  38. Bryant NA, Wilkie GS, Russell CA, Compston L, Grafham D, Clissold L, McLay K, Medcalf L, Newton R, Davison AJ, Elton DM. Genetic diversity of equine herpesvirus 1 isolated from neurological, abortigenic and respiratory disease outbreaks.. Transbound Emerg Dis 65:817–832.
    pmc: PMC5947664pubmed: 29423949
  39. Sutton G, Thieulent C, Fortier C, Hue ES, Marcillaud-Pitel C, Pléau A, Deslis A, Guitton E, Paillot R, Pronost S. Identification of a new equid herpesvirus 1 DNA polymerase (ORF30) genotype with the isolation of a C2254/H752 strain in French horses showing no major impact on the strain behaviour.. Viruses 12:1160.
    pmc: PMC7650556pubmed: 33066315
  40. Pusterla N, Barnum S, Lawton K, Wademan C, Corbin R, Hodzic E. Investigation of the EHV-1 genotype (N752, D752, and H752) in swabs collected from equids with respiratory and neurological disease and abortion from the United States (2019–2022).. J Equine Vet Sci 123:104244.
    pubmed: 36773852
  41. He Q, Wu Y, Wang M, Chen S, Jia R, Yang Q, Zhu D, Liu M, Zhao X, Zhang S, Huang J, Ou X, Mao S, Gao Q, Sun D, Tian B, Cheng A. ICP22/IE63 mediated transcriptional regulation and immune evasion: two important survival strategies for alphaherpesviruses.. Front Immunol 12:743466.
    pmc: PMC8674840pubmed: 34925320
  42. Vandekerckhove AP, Glorieux S, Gryspeerdt AC, Steukers L, Duchateau L, Osterrieder N, Van de Walle GR, Nauwynck HJ. Replication kinetics of neurovirulent versus non-neurovirulent equine herpesvirus type 1 strains in equine nasal mucosal explants.. J Gen Virol 91:2019–2028.
    pubmed: 20427565
  43. Gryspeerdt AC, Vandekerckhove AP, Garré B, Barbé F, Van de Walle GR, Nauwynck HJ. Differences in replication kinetics and cell tropism between neurovirulent and non-neurovirulent EHV1 strains during the acute phase of infection in horses.. Vet Microbiol 142:242–253.
    pubmed: 19926232
  44. Van Cleemput J, Poelaert KCK, Laval K, Maes R, Hussey GS, Van den Broeck W, Nauwynck HJ. Access to a main alphaherpesvirus receptor, located basolaterally in the respiratory epithelium, is masked by intercellular junctions.. Sci Rep 7:16656.
    pmc: PMC5709510pubmed: 29192251
  45. Laval K. Equine CD172a monocytic cells, the “Trojan horse” for equine herpesvirus type 1 (EHV-1) dissemination in the horse.. PhD Thesis, Ghent University, Faculty of Veterinary Medicine, Belgium.
  46. Zhao J, Poelaert KCK, Van Cleemput J, Nauwynck HJ. CCL2 and CCL5 driven attraction of CD172a monocytic cells during an equine herpesvirus type 1 (EHV-1) infection in equine nasal mucosa and the impact of two migration inhibitors, rosiglitazone (RSG) and quinacrine (QC).. Vet Res 48:14.
    pmc: PMC5327560pubmed: 28241864
  47. Laval K, Poelaert KCK, Van Cleemput J, Zhao J, Vandekerckhove AP, Gryspeerdt AC, Garré B, van der Muelen K, Baghi HB, Dubale HN, Zarak I, Van Crombrugge E, Nauwynck HJ. The pathogenesis and immune evasive mechanisms of equine herpesvirus type 1.. Front Microbiol 12:662686.
    pmc: PMC7970122pubmed: 33746936
  48. Laval K, Favoreel HW, Nauwynck HJ. Equine herpesvirus type 1 replication is delayed in CD172a monocytic cells and controlled by histone deacetylases.. J Gen Virol 96:118–130.
    pubmed: 25239765
  49. Laval K, Favoreel HW, Poelaert KCK, Van Cleemput J, Nauwynck HJ. Equine Herpesvirus type 1 enhances viral replication in CD172a monocytic cells upon adhesion to endothelial cells.. J Virol 89:10912–10923.
    pmc: PMC4621108pubmed: 26292328
  50. Laval K, Favoreel HW, Van Cleemput J, Poelaert KCK, Brown IK, Verhasselt B, Nauwynck HJ. Entry of equid herpesvirus 1 into CD172a monocytic cells.. J Gen Virol 97:733–746.
    pubmed: 26684016
  51. Laval K, Van Cleemput J, Poelaert KC, Brown IK, Nauwynck HJ. Replication of neurovirulent equine herpesvirus type 1 (EHV-1) in CD172a monocytic cells.. Comp Immunol Microbiol Infect Dis 50:58–62.
    pubmed: 28131380
  52. Van Cleemput J, Poelaert KCK, Laval K, Nauwynck HJ. Unravelling the first key steps in equine herpesvirus type 5 (EHV5) pathogenesis using ex vivo and in vitro equine models.. Vet Res 50:13.
    pmc: PMC6380010pubmed: 30777128

Citations

This article has been cited 3 times.
  1. Conn KL. Equine histones are mobilized within equid alphaherpesvirus 1 (EHV1) replication compartments.. J Virol 2025 Dec 23;99(12):e0158925.
    doi: 10.1128/jvi.01589-25pubmed: 41288450google scholar: lookup
  2. Mohamed E, Van Cleemput J, Şahin B, Van den Broeck W, Boyen F, Nauwynck H. Streptococcus equi subsp. zooepidemicus Supernatant Containing Streptolysin S Alters the Equine Nasal and Vaginal Mucosa, Modulating Equine Herpesvirus 1, 3 and 4 Infections.. Viruses 2025 Jul 14;17(7).
    doi: 10.3390/v17070980pubmed: 40733597google scholar: lookup
  3. Mohamed E, Zarak I, Vereecke N, Theuns S, Laval K, Nauwynck H. Correction: Genomic analysis and replication kinetics of the closely related EHV-1 neuropathogenic 21P40 and abortigenic 97P70 strains.. Vet Res 2025 Feb 7;56(1):34.
    doi: 10.1186/s13567-025-01464-5pubmed: 39920827google scholar: lookup
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