scholarly journals Selection and Characterization of Varicella-Zoster Virus Variants Resistant to (R)-9-[4-Hydroxy-2-(Hydroxymethy)Butyl]Guanine

2001 ◽  
Vol 45 (6) ◽  
pp. 1629-1636 ◽  
Author(s):  
Teresa I. Ng ◽  
Yan Shi ◽  
H. Janette Huffaker ◽  
Warren Kati ◽  
Yaya Liu ◽  
...  
Keyword(s):  
Varicella Zoster Virus ◽  
Dna Polymerases ◽  
Resistant Mutant ◽  
Competitive Inhibitor ◽  
Varicella Zoster ◽  
Antiviral Activities ◽  
Predominant Variant ◽  
Infected Cells

ABSTRACT (R)-9-[4-Hydroxy-2-(hydroxymethy)butyl]guanine (H2G) is a potent and selective inhibitor of herpesvirus replication. It is a nucleoside analog, and its triphosphate derivative (H2G-TP) is a competitive inhibitor of herpesvirus DNA polymerases. In this study, the antiviral activities of H2G and acyclovir (ACV) and the development of viral resistance to these agents were compared in varicella-zoster virus (VZV)-infected cells. In plaque reduction assays, the 50% effective concentration of H2G for VZV was 60- to 400-fold lower than that of ACV, depending on the virus strain and the cell line tested. The enhanced efficacy of H2G against VZV can be accounted for in part by the fact that the intaracellular H2G-TP level (>170 pmol/106 cells) is higher than the intracellular ACV-TP level (<1 pmol/106 cells). In addition, H2G-TP has extended half-lives of 3.9 and 8.6 h in VZV-infected MRC-5 and MeWo cells, respectively. To assess the emergence of H2G-resistant VZV in vitro, VZV was passaged in the presence of increasing concentrations of H2G. Earlier in the passage, when the concentration of H2G was relatively low, the predominant variant had the (A)76 deletion in the viral thymidine kinase (TK) gene. This mutant was identical to an ACV-resistant mutant generated in parallel experiments. However, higher concentrations of H2G appeared to favor a novel mutant, which had deletions of two consecutive nucleotides at positions 805 and 806 of the TK gene. All of these changes introduced frameshift mutations in the TK gene resulting in the expression of truncated polypeptides. H2G-resistant viruses were cross-resistant to ACV, and vice versa.

scholarly journals Deletion of the First Cysteine-Rich Region of the Varicella-Zoster Virus Glycoprotein E Ectodomain Abolishes the gE and gI Interaction and Differentially Affects Cell-Cell Spread and Viral Entry

2008 ◽  
Vol 83 (1) ◽  
pp. 228-240 ◽  
Author(s):  
Barbara Berarducci ◽  
Jaya Rajamani ◽  
Mike Reichelt ◽  
Marvin Sommer ◽  
Leigh Zerboni ◽  
...  
Keyword(s):  
Varicella Zoster Virus ◽  
Viral Entry ◽  
Rich Region ◽  
Glycoprotein E ◽  
Varicella Zoster ◽  
Viral Particles ◽  
Infected Cells ◽  
Cell Spread ◽  
Cell Cell

ABSTRACT Varicella-zoster virus (VZV) glycoprotein E (gE) is the most abundant glycoprotein in infected cells and, in contrast to those of other alphaherpesviruses, is essential for viral replication. The gE ectodomain contains a unique N-terminal region required for viral replication, cell-cell spread, and secondary envelopment; this region also binds to the insulin-degrading enzyme (IDE), a proposed VZV receptor. To identify new functional domains of the gE ectodomain, the effect of mutagenesis of the first cysteine-rich region of the gE ectodomain (amino acids 208 to 236) was assessed using VZV cosmids. Deletion of this region was compatible with VZV replication in vitro, but cell-cell spread of the rOka-ΔCys mutant was reduced significantly. Deletion of the cysteine-rich region abolished the binding of the mutant gE to gI but not to IDE. Preventing gE binding to gI altered the pattern of gE expression at the plasma membrane of infected cells and the posttranslational maturation of gI and its incorporation into viral particles. In contrast, deletion of the first cysteine-rich region did not affect viral entry into human tonsil T cells in vitro or into melanoma cells infected with cell-free VZV. These experiments demonstrate that gE/gI heterodimer formation is essential for efficient cell-cell spread and incorporation of gI into viral particles but that it is dispensable for infectious varicella-zoster virion formation and entry into target cells. Blocking gE binding to gI resulted in severe impairment of VZV infection of human skin xenografts in SCIDhu mice in vivo, documenting the importance of cell fusion mediated by this complex for VZV virulence in skin.

scholarly journals Varicella-Zoster Virus ORF47 Protein Serine Kinase: Characterization of a Cloned, Biologically Active Phosphotransferase and Two Viral Substrates, ORF62 and ORF63

2001 ◽  
Vol 75 (18) ◽  
pp. 8854-8858 ◽  
Author(s):  
T. K. Kenyon ◽  
J. Lynch ◽  
J. Hay ◽  
W. Ruyechan ◽  
C. Grose
Keyword(s):  
Varicella Zoster Virus ◽  
Kinase Activity ◽  
Biologically Active ◽  
Regulatory Proteins ◽  
Kinase Assay ◽  
Serine Kinase ◽  
Varicella Zoster ◽  
Simplex Virus

ABSTRACT Varicella-zoster virus (VZV) codes for a protein serine kinase called ORF47; the herpes simplex virus (HSV) homolog is UL13. No recombinant alphaherpesvirus serine kinase has been biologically active in vitro. We discovered that preservation of the intrinsic kinase activity of recombinant VZV ORF47 required unusually stringent in vitro conditions, including physiological concentrations of polyamines. In this assay, ORF47 phosphorylated two VZV regulatory proteins: the ORF62 protein (homolog of HSV ICP4) and the ORF63 protein (homolog of HSV ICP22). Of interest, ORF47 kinase also coprecipitated ORF63 protein from the kinase assay supernatant.

scholarly journals Varicella-Zoster Virus Infection of Human Fibroblast Cells Activates the c-Jun N-Terminal Kinase Pathway

2006 ◽  
Vol 81 (2) ◽  
pp. 977-990 ◽  
Author(s):  
Heidi J. Zapata ◽  
Masako Nakatsugawa ◽  
Jennifer F. Moffat
Keyword(s):  
Varicella Zoster Virus ◽  
Competitive Inhibitor ◽  
Mitogen Activated Protein Kinase ◽  
Varicella Zoster Virus Infection ◽  
Jnk Pathway ◽  
Varicella Zoster ◽  
Mitogen Activated Protein ◽  
Biochemical Fractionation ◽  
Infected Cells ◽  
Kinase Pathway

ABSTRACT The transcription factors ATF-2 and c-Jun are important for transactivation of varicella-zoster virus (VZV) genes. c-Jun is activated by the c-Jun N-terminal kinase (JNK), a member of the mitogen-activated protein kinase pathway that responds to stress and cytokines. To study the effects of VZV on this pathway, confluent human foreskin fibroblasts were infected with cell-associated VZV for 1 to 4 days. Immunoblots showed that phosphorylated JNK and c-Jun levels increased in VZV-infected cells, and kinase assays determined that phospho-JNK was active. Phospho-JNK was detected after 24 h, and levels rose steadily over 4 days in parallel with accumulation of VZV antigen. The two main activators of JNK are MKK4 and MKK7, and levels of their active, phosphorylated forms also increased. The competitive inhibitor of JNK, SP600125, caused a dose-dependent reduction in VZV yield (50% effective concentration, ≅8 μM). Specificity was verified by immunoblotting; phospho-c-Jun was eliminated by 18 μM SP600125 in VZV-infected cells. Immunofluorescent confocal microscopy showed that phospho-c-Jun and most of phospho-JNK were in the nuclei of VZV-infected cells; some phospho-JNK was in the cytoplasm. MKK4, MKK7, JNK, and phospho-JNK were detected by immunoblotting in purified preparations of VZV virions, but c-Jun was absent. JNK was located in the virion tegument, as determined by biochemical fractionation and immunogold transmission electron microscopy. Overall, these results demonstrate the importance of the JNK pathway for VZV replication and advance the idea that JNK is a useful drug target against VZV.

scholarly journals Cyclin-Dependent Kinase 1/Cyclin B1 Phosphorylates Varicella-Zoster Virus IE62 and Is Incorporated into Virions

2008 ◽  
Vol 82 (24) ◽  
pp. 12116-12125 ◽  
Author(s):  
Stacey A. Leisenfelder ◽  
Paul R. Kinchington ◽  
Jennifer F. Moffat
Keyword(s):  
Varicella Zoster Virus ◽  
Cyclin B1 ◽  
Dermal Fibroblasts ◽  
Cyclin Dependent Kinase ◽  
Varicella Zoster ◽  
Differentiated Cells ◽  
Infected Cells ◽  
Recombinant Fragments

ABSTRACT Varicella-zoster virus (VZV), an alphaherpesvirus restricted to humans, infects differentiated cells in vivo, including T lymphocytes, keratinocytes, and neurons, and spreads rapidly in confluent cultured dermal fibroblasts (HFFs). In VZV-infected HFFs, atypical expression of cyclins D3 and B1 occurs along with the induction of cyclin-dependent kinase (CDK) activity. A specific CDK1 inhibitor blocked VZV spread, indicating an important function for this cellular kinase in VZV replication. CDK activity assays of infected cells revealed a large viral phosphoprotein that was identified as being the major immediate-early transactivator, IE62. Since IE62 colocalized with CDK1/cyclin B1 by confocal microscopy, we investigated whether this cellular kinase complex interacts with IE62. Using recombinant fragments of IE62 spanning the entire amino acid sequence, we found that purified CDK1/cyclin B1 phosphorylated IE62 at residues T10, S245, and T680 in vitro. Immunoprecipitation of cyclin B1 from VZV-infected HFFs indicated that IE62 was included in the complex within infected cells. The full-length IE62 protein, obtained by immunoprecipitation from infected cells, was also phosphorylated by purified CDK1/cyclin B1. Based on IE62/CDK1/cyclin B1 colocalization near viral assembly regions, we hypothesized that these cellular proteins could be incorporated into VZV virions with IE62. Purified virions were analyzed by immunoblotting for the presence of CDK1 and cyclin B1, and active CDK1 and cyclin B1 were present in the VZV tegument with IE62 and were sensitive to detergent treatment. Thus, IE62 is a substrate for CDK1/cyclin B1, and virions could deliver the active cellular kinase to nondividing cells that normally do not express it.

Synthesis and Antiviral Activities of 3-Aralkyl-Thiomethylimidazo[1,2-b]Pyridazine Derivatives

2003 ◽  
Vol 14 (4) ◽  
pp. 177-182 ◽  
Author(s):  
Christophe Galtier ◽  
Sylvie Mavel ◽  
Robert Snoeck ◽  
Graciela Andreï ◽  
Christophe Pannecouque ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Antiviral Activity ◽  
Varicella Zoster Virus ◽  
Human Cytomegalovirus ◽  
Antiviral Agents ◽  
Varicella Zoster ◽  
Immunodeficiency Virus ◽  
Antiviral Activities ◽  
Pyridazine Derivatives

The synthesis of novel substituted 3-aralkylth-iomethylimidazo[1,2- b]pyridazines is reported. All of the synthesized compounds are devoid of antiviral activity against the replication of human immunodeficiency virus. However, compounds 6-chloro-8-methyl-3-phenethylthioimidazo[1,2- b]pyridazine and 6-chloro-2-methyl-3-phenethyl-thioimidazo[1,2- b]pyridazine are potent inhibitors of the replication of human cytomegalovirus in vitro, while compounds 6-chloro-2-methyl-3-benzylthiomethylimidazo[1,2- b]pyridazine and 6-chloro-2-methyl-3-phenethyl-thioimidazo[1,2- b]pyridazineare inhibitors of the replication of varicella-zoster virus. The results presented here suggest that compound 10 should be considered as a new lead in the development of antiviral agents.

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