Putative glycoprotein gene of varicella-zoster virus with variable copy numbers of a 42-base-pair repeat sequence has homology to herpes simplex virus glycoprotein C

Glycoprotein C from herpes simplex viruses types 1 and 2 (gC-1 and gC-2) acts as a receptor for the C3b fragment of the third component of complement. Our goal is to identify domains on gC involved in C3b receptor activity. Here, we used in-frame linker-insertion mutagenesis of the cloned gene for gC-2 to identify regions of the protein involved in C3b binding. We constructed 41 mutants of gC-2, each having a single, double, or triple insertion of four amino acids at sites spread across the protein. A transient transfection assay was used to characterize the expressed mutant proteins. All of the proteins were expressed on the transfected cell surface, exhibited processing of N-linked oligosaccharides, and bound one or more monoclonal antibodies recognizing distinct antigenic sites on native gC-2. This suggested that each of the mutant proteins was folded into a native structure and that a loss of C3b binding by any of the mutants could be attributed to the disruption of a specific functional domain. When the panel of insertion mutants was assayed for C3b receptor activity, we identified three distinct regions that are important for C3b binding, since an insertion within those regions abolished C3b receptor activity. Region I was located between amino acids 102 and 107, region II was located between residues 222 and 279, and region III was located between residues 307 and 379. In addition, region III has some structural features similar to a conserved motif found in complement receptor 1, the human C3b receptor. Finally, blocking experiments indicated that gC-l and gC-2 bind to similar locations on the C3b molecule.

Section: Discussionmentioning

confidence: 99%

Identification of C3b-binding regions on herpes simplex virus type 2 glycoprotein C

Seidel-Dugan

Leon

Friedman

et al. 1990

“…Since this study has further demonstrated that R5 is variable among VZV strains, all direct reiterations of VZV except R3 are now known to vary among VZV Strains. Tandem direct repeats in general seem to be variable among VZV strains, whether or not they are part of coding regions, since Rl and R2 are present within open reading frames (3,8), whereas R4 and R5 are not (1,3). Although the mechanism by which they change is not known at present, tandem direct reiterations of the VZV genome are hot spots that vary much more readily than other regions of the genome.…”

Section: Discussionmentioning

confidence: 99%

Strain variation of R5 direct repeats in the right-hand portion of the long unique segment of varicella-zoster virus DNA

Hondo

Yogo

1988

We located a region of interstrain size variability in a short segment in an area at the right-hand end of the long unique sequence of the varicella-zoster viral genome. Varicella-zoster virus strains isolated in a district of Japan were classified into three groups on the basis of the size of this segment. Sequence comparison of the variable segment among strains from different groups revealed that the tandem direct repeat, R5, in the segment was variable among strains. R5, which was first discovered in a European strain (Dumas), contained a direct duplication of 88-base-pair (bp) elements separated by a 24-bp element (A

“…All probes were double-stranded DNA fragments labeled to high specific activity by using oligonucleotide-primed repair synthesis and [␣-32 P]dCTP (3,000 Ci/mmol). Each specific probe was generated from previously derived DNA clones from VZV strain Scott, a low-passage clinical isolate (25). VZV gC-specific probes were generated by using a BstN1-AhdI fragment, representing bp 19480 to 21116.…”

Section: Methodsmentioning

confidence: 99%

“…Diminished expression of glycoprotein C (gC) has been proposed as a genetic factor that may be related to the clinical attenuation of V-Oka (24). gC is one of six known VZV envelope glycoproteins and has 34% amino acid homology to herpes simplex virus type 1 (HSV-1) gC (25). HSV-1 gC binds to heparan sulfate on the cell surface and to the C3b component of complement (16,21).…”

mentioning

confidence: 99%

Attenuation of the Vaccine Oka Strain of Varicella-Zoster Virus and Role of Glycoprotein C in Alphaherpesvirus Virulence Demonstrated in the SCID-hu Mouse

Moffat

Zerboni

Kinchington

et al. 1998

212

The SCID-hu mouse implanted with human fetal tissue is a novel model for investigating human viral pathogenesis. Infection of human skin implants was used to investigate the basis for the clinical attenuation of the varicella-zoster virus (VZV) strain, V-Oka, from which the newly licensed vaccine is made. The pathogenicity of V-Oka was compared with that of its parent, P-Oka, another low-passage clinical isolate, strain Schenke (VZV-S), and VZV-Ellen, a standard laboratory strain. The role of glycoprotein C (gC) in infectivity for human skin was assessed by using gC-negative mutants of V-Oka and VZV-Ellen. Whereas all of these VZV strains replicated well in tissue culture, only low-passage clinical isolates were fully virulent in skin, as shown by infectious virus yields and analysis of implant tissues for VZV DNA and viral protein synthesis. The infectivity of V-Oka in skin was impaired compared to that of P-Oka, providing the first evidence of a virologic basis for the clinical attenuation of V-Oka. The infectivity of V-Oka was further diminished in the absence of gC expression. All strains except gC-Ellen retained some capacity to replicate in human skin, but cell-free virus was recovered only from implants infected with P-Oka or VZV-S. Although VZV is closely related to herpes simplex virus type 1 (HSV-1) genetically, experiments in the SCID-hu model revealed differences in tropism for human cells that correlated with differences in VZV and HSV-1 disease. VZV caused extensive infection of epidermal and dermal skin cells, while HSV-1 produced small, superficial lesions restricted to the epidermis. As in VZV, gC expression was a determinant for viral replication in skin. VZV infects human CD4+ and CD8+ T cells in thymus/liver implants, but HSV-1 was detected only in epithelial cells, with no evidence of lymphotropism. These SCID-hu mouse experiments show that the clinical attenuation of the varicella vaccine can be attributed to decreased replication of V-Oka in skin and that tissue culture passage alone reduces the ability of VZV to infect human skin in vivo. Furthermore, gC, which is dispensable for replication in tissue culture, plays a critical role in the virulence of the human alphaherpesviruses VZV and HSV-1 for human skin.