Characterization of a thymidine kinase-deficient mutant of equine herpesvirus 4 and in vitro susceptibility of the virus to antiviral agents.
Abstract: Equine herpesvirus 4 (EHV-4) is an important equine pathogen that causes respiratory tract disease among horses worldwide. A thymidine kinase (TK)-deletion mutant has been generated by using bacterial artificial chromosome (BAC) technology to investigate the role of TK in pathogenesis. Deletion of TK had virtually no effect on the growth characteristics of WA79DeltaTK in cell culture when compared to the parent virus. Also, virus titers and plaque formation were unaffected in the absence of the TK gene. The sensitivity of EHV-4 to inhibition by acyclovir (ACV) and ganciclovir (GCV) was studied by means of a plaque reduction assay. GCV proved to be more potent and showed a superior anti-EHV-4 activity. On the other hand, ACV showed very poor ability to inhibit EHV-4 replication. As predicted, WA79DeltaTK was insensitive to GCV. Although EHV-4 is normally insensitive to ACV, it showed >20-fold increase in sensitivity when the equine herpesvirus-1 (EHV-1) TK was supplied in trans. Furthermore, both ACV and GCV resulted in a significant reduction of plaque size induced by EHV-4 and 1. Taken together, these data provided direct evidence that GCV is a potent selective inhibitor of EHV-4 and that the virus-encoded TK is an important determinant of the virus susceptibility to nucleoside analogues.
Copyright 2009 Elsevier B.V. All rights reserved.
Publication Date: 2009-11-30 PubMed ID: 19931566DOI: 10.1016/j.antiviral.2009.11.007Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The researched article discusses the creation and analysis of a mutant strain of the Equine Herpesvirus 4 (EHV-4), which has the thymidine kinase (TK) gene removed. Further, the study assesses the effect of antiviral drugs, acyclovir (ACV) and ganciclovir (GCV), on the mutant and original EHV-4 virus. The results indicate the greater effectiveness of GCV, and the important role of the TK gene, in inhibiting the virus’s replication.
Understanding the study on EHV-4
In this study, the researchers sought to understand the role of thymidine kinase (TK) gene in the replication and growth characteristics of the Equine Herpesvirus 4 (EHV-4), as well as the impact of antiviral drugs on the virus.
- The tools employed in this study included the creation of a TK-deficient mutation of the EHV-4 virus labelled WA79DeltaTK. This was achieved through the use of bacterial artificial chromosome (BAC) technology.
- The researchers then compared the growth characteristics, virus titers (the concentration of the virus), and plaque formation capabilities of WA79DeltaTK with the original EHV-4 strain. They established that the removal of the TK gene had no significant impact on these aspects of the virus.
Testing the Antiviral Drug Sensitivity
The next part of the study involved the application of antiviral treatments—acyclovir (ACV) and ganciclovir (GCV)—to the mutant and original EHV-4 strains.
- The effectiveness of the antiviral treatments was evaluated using a plaque reduction assay. From their experiments, the researchers learned that GCV was noticeably more potent than ACV in inhibiting EHV-4 replication.
- The WA79DeltaTK virus proved to be insensitive to GCV, indicating the significant role the TK gene plays in the virus’s susceptibility to some antiviral drugs.
- Interestingly, even though EHV-4 is typically insensitive to ACV treatments, they found a greatly increased sensitivity when the equine herpesvirus-1 (EHV-1) TK was introduced.
Conclusion
- This research ultimately provides evidence that GCV is a powerful inhibitor of EHV-4. The experiments also demonstrate the vital role played by the virus-encoded TK gene in the susceptibility of EHV-4 to antiviral treatments.
- The findings clarify the relevance of the TK gene in the EHV-4 virus and its possible exploitation in the treatment of diseases associated with the virus.
Cite This Article
APA
Azab W, Tsujimura K, Kato K, Arii J, Morimoto T, Kawaguchi Y, Tohya Y, Matsumura T, Akashi H.
(2009).
Characterization of a thymidine kinase-deficient mutant of equine herpesvirus 4 and in vitro susceptibility of the virus to antiviral agents.
Antiviral Res, 85(2), 389-395.
https://doi.org/10.1016/j.antiviral.2009.11.007 Publication
Researcher Affiliations
- Department of Veterinary Microbiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
MeSH Terms
- Acyclovir / pharmacology
- Animals
- Antiviral Agents / pharmacology
- Cell Line
- Ganciclovir / pharmacology
- Gene Deletion
- Herpesvirus 4, Equid / drug effects
- Herpesvirus 4, Equid / genetics
- Herpesvirus 4, Equid / pathogenicity
- Humans
- Microbial Sensitivity Tests
- Thymidine Kinase / deficiency
- Viral Plaque Assay
- Viral Proteins / genetics
Citations
This article has been cited 7 times.- Maxwell LK, Bentz BG, Gilliam LL, Ritchey JW, Pusterla N, Eberle R, Holbrook TC, McFarlane D, Rezabek GB, Meinkoth J, Whitfield C, Goad CL, Allen GP. Efficacy of the early administration of valacyclovir hydrochloride for the treatment of neuropathogenic equine herpesvirus type-1 infection in horses.. Am J Vet Res 2017 Oct;78(10):1126-1139.
- Wu Y, Li Y, Wang M, Sun K, Jia R, Chen S, Zhu D, Liu M, Yang Q, Zhao X, Chen X, Cheng A. Preliminary study of the UL55 gene based on infectious Chinese virulent duck enteritis virus bacterial artificial chromosome clone.. Virol J 2017 Apr 13;14(1):78.
- Spiesschaert B, Osterrieder N, Azab W. Comparative analysis of glycoprotein B (gB) of equine herpesvirus type 1 and type 4 (EHV-1 and EHV-4) in cellular tropism and cell-to-cell transmission.. Viruses 2015 Feb 3;7(2):522-42.
- Azab W, El-Sheikh A. The role of equine herpesvirus type 4 glycoprotein k in virus replication.. Viruses 2012 Aug;4(8):1258-63.
- Azab W, Zajic L, Osterrieder N. The role of glycoprotein H of equine herpesviruses 1 and 4 (EHV-1 and EHV-4) in cellular host range and integrin binding.. Vet Res 2012 Aug 21;43(1):61.
- Said A, Azab W, Damiani A, Osterrieder N. Equine herpesvirus type 4 UL56 and UL49.5 proteins downregulate cell surface major histocompatibility complex class I expression independently of each other.. J Virol 2012 Aug;86(15):8059-71.
- Azab W, Osterrieder N. Glycoproteins D of equine herpesvirus type 1 (EHV-1) and EHV-4 determine cellular tropism independently of integrins.. J Virol 2012 Feb;86(4):2031-44.
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