Evolutionary comparisons of the S segments in the genomes of herpes simplex virus type 1 and varicella-zoster virus

The genomes of herpes simplex virus type 1 (HSV-1) and varicella-zoster virus (VZV) consist of two covalently joined segments, L and S. Each segment comprises an unique sequence flanked by inverted repeats. We have reported previously the DNA sequences of the S segments in these two genomes, and have identified protein-coding regions therein. In HSV-1, the unique sequence of S contains ten entire genes plus the major parts of two more, and each inverted repeat contains one entire gene; in VZV, the unique sequence of S contains two entire genes plus the major parts of two more, and each inverted repeat contains three entire genes. In this report, an examination of polypeptide sequence homology has shown that each VZV gene has an HSV-1 counterpart, but that six of the HSV-1 genes have no VZV homologues. Thus, although these regions of the two genomes differ in gene layout, they are related to a significant degree. The analysis indicates that the inverted repeats are evidently capable of large-scale expansion or contraction during evolution. The differences in gene layout can be understood as resulting from a small number of recombinational events during the descent of HSV-1 and VZV from a common ancestor.

Susceptibilities of phosphonoacetic acid and acyclovir resistant varicella-zoster virus mutants to 9-beta-arabinofuranosyladenine and 1-beta-arabinofuranosylcytosine

The DNA polymerase activity, and susceptibilities to 9-beta-D-arabinofuranosyladenine(ara-A) and 1-beta-arabinofuranosylcytosine(ara-C) of a phosphonoacetic acid resistant mutant (PAA-R) of varicella-zoster virus (VZV) selected in the presence of PAA were examined. The DNA polymerase activity of PAA-R was inhibited less than that of the parent strain by PAA in vitro. PAA-R was resistant to acyclovir and also to both ara-A and ara-C. The susceptibilities to ara-A and ara-C of four acyclovir resistant mutants selected in the presence of acyclovir, and also resistant to PAA, were examined. Two variants were resistant, one was slightly resistant, and one was sensitive to both drugs. These cross-resistances and susceptibilities of VZV variants to PAA, ACV, ara-A and ara-C should be considered in chemotherapy of VZV infections.

Thymidine kinase with altered substrate specificity of acyclovir resistant varicella-zoster virus

The acyclovir resistant mutant of varicella-zoster virus ACV-R (A 8) induced the same level of thymidine kinase activity in infected cells as the parent Kawaguchi strain. However, it induced less deoxycytidine kinase activity and did not induce phosphorylating activity for the nucleotide analogue, 9-(2 hydroxy-ethoxymethyl)-guanine-(acyclovir). Another acyclovir resistant mutant, ACV-R (A 4), which is cross-resistant to phosphonoacetate and is thought to be a viral DNA polymerase mutant, induced the same level of phosphorylating activities for thymidine, deoxycytidine and acyclovir as the parent strain. The altered substrate specificity of thymidine kinase induced by ACV-R (A 8) is concluded to confer resistance to acyclovir on ACV-R (A 8).

New common nomenclature for glycoprotein genes of varicella-zoster virus and their glycosylated products

The accumulation of recent data concerning the reactivity of monoclonal antibodies with particular varicella-zoster virus (VZV) glycoproteins and the mapping of several of their respective genes on the VZV genome has led to a unified nomenclature for the glycoprotein genes of VZV and their mature glycosylated products. Homologs to herpes simplex virus glycoprotein genes are noted.

Alphaherpesviruses possess a gene homologous to the protein kinase gene family of eukaryotes and retroviruses

The US3 genes of herpes simplex virus serotypes 1 and 2, and the corresponding gene of varicella-zoster virus, encode proteins whose sequences are clearly homologous to members of the protein kinase family of eukaryotes and retroviruses. Similarity is most characteristic, and strongest, in an 80 residue region comprising part of the catalytic structure of the kinases. In this region the herpesvirus proteins are most like a yeast cell division control protein, and least like the retrovirus protein-tyrosine kinases. We consider that the herpesvirus proteins are probably involved in modulation of cellular processes during lytic infection, although other roles are also possible, for example in latent infection.

Mapping of the varicella zoster virus deoxypyrimidine kinase gene and preliminary identification of its transcript

The varicella-zoster virus (VZV) deoxypyrimidine kinase (dPK) gene was mapped by transfection of cloned viral DNA fragments into thymidine kinase-deficient mouse L (LTK-) cells and subsequent biochemical transformation of these cells to the LTK+ phenotype. Such transforming activity was limited to the BamHI-H and EcoRI-D fragments of the VZV genome, which overlap by 2.2 kb between map units 0.50 and 0.52. Biochemically transformed cells were shown to contain a high copy number of viral DNA sequences that had integrated into the cellular DNA. Extracts of these cells showed a higher level of dPK activity than did extracts of parental LTK- cells. With the use of Northern hybridization analysis of transformed and VZV-infected cell RNAs, it was possible to tentatively assign a 1.8-kb transcript to the VZV dPK.

Polyadenylated, cytoplasmic transcripts of varicella-zoster virus

Cytoplasmic RNA was isolated from varicella-zoster virus (VZV)-infected cells. By oligo(dT)-cellulose chromatography, the RNA was separated into polyadenylated, poly (A)+, and nonpolyadenylated, poly (A)-, fractions. RNA blot hybridization was employed to detect and map VZV transcripts. As VZV infection cannot be coordinated, cytoplasmic RNA was isolated from VZV-infected cells when the cells showed extensive cytopathology. Therefore, while the VZV transcripts represented heterogeneous temporal classes, it may be assumed that late VZV RNA predominated. At least 41, and as many as 67 (depending on DNA probe overlap), VZV polyadenylated transcripts have been identified. Preliminary evidence for the presence of two VZV-specific nonpolyadenylated, cytoplasmic transcripts was observed.

Transcription mapping of the varicella-zoster virus genome

RNA was isolated from varicella-zoster virus-infected Flow 5000 cells (diploid fibroblasts) at late times after infection. With the use of overlapping DNA probes representing all regions of the varicella-zoster genome, an extensive Northern blot analysis of the RNA was carried out. The analysis revealed at least 58 discrete transcripts ranging in size from approximately 0.8 to 6.5 kilobases. RNAs were found to be homologous to all probes used except for those mapping at approximately map unit 0.3, where no RNA transcripts could be detected. Comparison of the sizes and locations of RNA transcripts mapping in the right-hand ends of the varicella-zoster virus and the herpes simplex virus DNAs shows a number of striking analogies, suggesting their similar genomic organization.

Identification of the products of a varicella-zoster virus glycoprotein gene

Two of the genes identified from the previously published DNA sequence of the Us component of the varicella-zoster virus (VZV) genome were predicted to encode membrane proteins with polypeptide molecular weights of 39000 (39K) and 70K. A rabbit antiserum directed against a unique peptide containing the seven amino acid residues at the carboxy terminus of the 39K gene product specifically precipitated glycoproteins with apparent molecular weights of 55K and 45K from VZV-infected cells labelled with [3H]mannose. The complete inhibition of precipitation of gp55 by free peptide and the partial inhibition of precipitation of gp45 support the conclusion that the 39K gene encodes gp55 and perhaps gp45. The number of VZV genes currently thought to encode glycoproteins is discussed in view of this finding.

Processing of virus-specific glycoproteins of varicella zoster virus

Monoclonal antibodies to varicella zoster virus (VZV) glycoproteins were used to study the processing of three glycoproteins with molecular weights of 83K-94K (gp 2), 64K (gp 3), and 55K (gp 5). Immunoprecipitation experiments performed with VZV-infected cells, pulse labeled with [3H]glucosamine in the presence of tunicamycin, suggest that O-linked oligosaccharide is present on the glycoprotein of gp 2. Use of the enzyme endo-beta-N-acetylglucosaminidase H revealed that the fully processed form of gp 3 had high-mannose type and that of gp 5 had only complex type of N-linked oligosaccharides. Experiments with monensin suggest that the precursor form (116K) of gp 3 is cleaved during the processing from Golgi apparatus to cell surface membrane. The extension of O-linked oligosaccharide chain and the complex type of N-linked oligosaccharide chains also occurs during this processing.

DNA sequence of the major inverted repeat in the varicella-zoster virus genome

The major inverted repeat of 7319.5 base pairs is present at an internal site in the varicella-zoster virus genome and at one terminus. A DNA sequence of 7747 base pairs containing the repeat was determined and analysed. The G + C content of the repeat is not uniform, and is significantly higher than that of adjacent unique regions. The repeat contains a G + C-rich reiterated sequence, an A + T-rich sequence with the potential of forming a hairpin structure which may form part of an origin of DNA replication, and three open reading frames predicted to encode primary translation products with approximate molecular weights of 140 000, 30 000 and 20 000. The possibility is discussed that the expression of other open reading frames near the genome termini may depend upon genome conformation.

Distribution of G + C-rich regions in varicella-zoster virus DNA

The distribution of G + C-rich sequences in the genome of varicella-zoster virus (VZV) was investigated by partial denaturation, equilibrium sedimentation and Southern blot analyses. Portions of the IRS and TRS repeat sequences bounding the US region of the DNA were found to have a G + C content 10 to 20% greater than the overall 47% G + C content of the VZV genome. A stretch of DNA (approx. 1500 base pairs) at the UL-IRS junction and repeated at the terminus of the TRS sequences was found to be about 64% G + C, based on sedimentation equilibrium measurements. We also report the cloning of a novel fragment containing sequences from both the UL and TRS termini of the VZV genome. Our ability to clone this fragment suggests that unusual forms of VZV DNA including closed circular molecules and molecules with an inverted UL region can be packaged into nucleocapsids.

Structure of the genome termini of varicella-zoster virus

The DNA molecule of varicella-zoster virus (VZV) is represented structurally as L-S, where L is a unique sequence and S is a unique sequence flanked by an inverted repeat. S may be present in either orientation in virion DNA molecules, but, to date, L has been found in only one orientation. DNA sequences were determined at the L-S joint and genome termini, which were cloned using methods designed to conserve either the 3' or 5' terminal nucleotide. Molecular hybridization experiments and analysis of the sequences showed that: the genome is not terminally redundant; the unique sequence in L is flanked by an inverted repeat of 88.5 base pairs; a single unpaired nucleotide is located at each 3' terminus of the genome, such that fusion of the termini would produce a sequence identical to that at the L-S joint; approx. 5% of virions contain genomes with L inverted. The implications of these results in possible mechanisms for VZV DNA replication are discussed.

Three major glycoprotein genes of varicella-zoster virus whose products have neutralization epitopes

Varicella-zoster virus (VZV) codes for approximately eight glycosylated polypeptides in infected cell cultures and in virions. To determine the number of serologically distinct glycoprotein gene products encoded by VZV, we have developed murine monoclonal antibodies to purified virions. Of 10 monoclonal antibodies which can immunoprecipitate intracellular VZV antigens and virion glycoproteins, 1 (termed gA) reacted with gp105, 1 (termed gB) reacted with gp115 (intracellular only), gp62, and gp57, and 8 (termed gC) reacted with gp92, gp83, gp52, and gp45. The anti-gA monoclonal antibody neutralized VZV infectivity in the absence of complement. All eight anti-gC monoclonal antibodies neutralized only in the presence of complement. An anti-gB monoclonal antibody obtained from another laboratory also neutralizes in the absence of complement. Since the above reactivities account for all major detectable VZV glycoprotein species, the data strongly suggest that VZV has three major glycoprotein genes which encode glycosylated polypeptides with neutralization epitopes.

Dose-related effect of acetylsalicylic acid on replication of varicella zoster virus in vitro

Cultivation of human embryonic lung (HEL) cells in media containing acetylsalicylic acid (ASA) at 100 micrograms/ml and maintenance at this level after inoculation with either cell-free varicella zoster virus (VZV) or virus-infected cells resulted in a 2- to 4-fold increase in yields of cell-free virus released by sonication. The degree of enhancement was dependent upon multiplicity of infection and time of harvest. Enhanced viral yields were not consistently accompanied by an increase in the number of infected cells, nor was VZV plaque formation in HEL indicator cells significantly increased in the presence of ASA at 100 micrograms/ml. In the presence of ASA at 500-1000 micrograms/ml, VZV plaque formation was inhibited; this inhibition was partially reversible, depending on concentration and period of exposure to ASA. These findings may bear on the apparent association between ASA ingestion and the development of Reye syndrome after infection with varicella virus.

Simian varicella virus DNA shares homology with human varicella-zoster virus DNA

Delta herpesvirus (DHV) and Medical Lake Macaque (MLM) virus are cell-associated simian herpesviruses that cause varicella-like disease in nonhuman primates, and are antigenically related to human varicella-zoster virus (VZV). The results of studies designed to determine if homology exists between the DNA of DHV and MLM and the DNA of VZV are reported here. Southern blot hybridizations conducted at Tm-20 degrees did not detect DNA homology between the VZV and simian varicella virus genomes. However, under conditions of lower stringency (Tm-36 degrees and Tm-43 degrees), VZV DNA probes hybridized to specific HindIII fragments within DNA isolated from simian varicella virus-infected cells. Under similar hybridization conditions, DNA homology was not detected between VZV DNA and herpes simplex virus DNA. Further studies using cloned VZV DNA HindIII fragments as probes suggested that the homology between VZV DNA and DHV DNA is distributed across the viral genomes. These results demonstrate that the genomes of VZV and simian varicella virus share regions of conserved nucleotide sequences, and indicate a close evolutionary relationship between VZV and simian varicella viruses. In addition, the studies show that the DHV and MLM strains of simian varicella virus are more closely related to each other than to human VZV.

Structural organization of human herpesvirus DNA molecules

The herpesviruses are among the largest and most complex of all DNA viruses, and their genomes display an astonishing diversity in size, structure, and organization. In 1974, the features of large inverted repeats and structural isomerization were first discovered, and these proved to be characteristic properties of many herpesvirus genomes. Since then, research using the powerful techniques of modern molecular biology has revealed a great deal of comparative structural information about the arrangement of repetitive sequences and the location, structure, and primary nucleotide sequences of the genes for several easily assayed or abundantly expressed gene products. Extensive restriction enzyme cleavage maps and complete sets of cloned DNA fragments have been constructed for each of the five human herpesviruses, HSV-1, HSV-2, CMV, EBV, and VZV, and the entire 175,000-bp nucleotide sequence of EBV DNA has been determined. Based on these maps and reagents, the procedures of "DNA fingerprinting" and "dot hybridization" are proving useful at a clinical level for characterization of isolates and studying herpesvirus epidemiology. Strain differences, localized heterogeneity, tandem-repeat-defective genomes, and sites of cell-virus DNA homology have been described in some detail. The attention of basic researchers is now turning to equating structure with function, and rapid progress is expected in studies aimed at a better understanding of the mechanisms of viral DNA replication, maintenance of the latent state, reactivation, transformation, packaging, and regulation of the lytic cycle, etc using cloned functionally active DNA fragments, isolated intact genes and promoters, and DNA transfection and in vitro expression systems.

Varicella-zoster virus-induced transformation of mammalian cells in vitro

A mixture of varicella-zoster virus-infected human embryonic lung fibroblasts and hamster embryo cells produced foci of morphologically transformed cells after several weeks of incubation. These transformed cells exhibited virus-specific antigens by immunofluorescence and developed surface Fc receptors. They induced aggressive fibrosarcomas when injected back into inbred hamsters. Cells derived from hamster tumor tissue exhibited similar properties. The tumor-bearing hamsters develop antibodies specific for varicella-zoster virus (VZV) antigens. Cell lines derived from both the original transformants and explanted hamster tumor tissue have varying growth properties. All maintain indefinite growth. All eventually lose varicella-zoster virus-specific immunofluorescence. None retain VZV-specific DNA sequences as determined by dot blot and Southern blot hybridization using radiolabeled whole VZV DNA and cloned VZV DNA fragments as a probe. A few transformed and tumor cell lines frozen relatively soon after isolation and stored in liquid nitrogen were also thawed, replicated to mass culture, and analyzed for VZV-specific DNA sequences. Hybridization with radiolabeled whole VZV DNA initially suggested that some of these cell lines did contain virus-specific DNA sequences. However, hybridization with cloned VZV DNA fragments radiolabeled in vitro and representing greater than 95% of the virus genome was negative. Karyotyping of these "positive" transformed cells indicated that they are of human and not hamster origin. The positive hybridization with whole VZV DNA therefore most likely represented contamination of the probe by host DNA sequences. The cells that survived freezing then were predominantly transformants of human origin. Attempts to repeat the transformation of hamster embryo and baby hamster kidney cells with laboratory-passaged VZV strains have been unsuccessful. Similarly, we have been unable to transform cells with whole VZV DNA or cloned VZV DNA fragments, although whole VZV DNA is demonstrably infectious. Apparently, transformation of cells by the varicella-zoster virus is a very rare event and one that may require a recent clinical isolate. Fresh clinical isolates of varicella-zoster virus are seemingly able to transform mammalian cells in vitro. The transformed cells have malignant properties and are capable of indefinite growth. Although VZV gene function can be detected early after transformation, there is no evidence that a VZV-specific protein product is required. Transformation of mammalian cells by varicella-zoster virus apparently occurs through a "hit-and-run" mechanism.

Physical maps of varicella-zoster virus DNA derived with 11 restriction enzymes

Varicella-zoster virus DNA was digested with 11 restriction endonucleases, and the resulting fragments were separated on agarose gels. Terminal fragments were identified by lambda exonuclease digestion. Physical maps were then constructed using a combination of double restriction enzyme digestion and hybridization to cloned BamHI fragments to place the remaining fragments in order.

Variation in the structure of varicella-zoster virus DNA

By analyzing the fine structure of varicella-zoster virus (VZV) DNA, a naturally occurring heterogeneity was found on the right end of VZV DNA, but no evidence of a true terminal repetition was uncovered. We were unable to confirm the report of Straus and co-workers (1981) that there is a relatively high frequency of circular VZV DNA in low-passage virus. On long-term cell passage, extensive heterogeneity appeared concomitant with the accumulation of apparently defective VZV DNA.

Varicella-zoster virus DNA in human sensory ganglia

Varicella-zoster virus (VZV) causes chickenpox and shingles. Clinical and epidemiological evidence indicates that following an episode of childhood chickenpox (varicella), VZV becomes latent, presumably in dorsal root ganglia, and is reactivated many years later to produce shingles (zoster) in adults. VZV has been demonstrated in ganglia by electron microscopy and by indirect immunofluorescence, and infectious viral particles have been isolated from acutely infected ganglia of patients who died of disseminated VZV infection. However, VZV has not been detected in the ganglia of humans without recent exposure to VZV. Tissue culture explant methods that have been successful in the isolation of herpes simplex virus from ganglia have so far failed in the isolation or reactivation of VZV from trigeminal and other dorsal root ganglia. We describe here the detection of VZV DNA sequences in an acutely infected human sacral ganglion and in normal trigeminal ganglia. These findings support the hypothesis that VZV is latent in normal human ganglia.

DNA sequence of the US component of the varicella-zoster virus genome

The linear duplex DNA molecule of varicella-zoster virus is 120 000 bp in size and has the sequence arrangement UL-IRS-US-TRS, where UL and US are unique sequences and IRS and TRS are inverted repeats flanking US. The primary structure of the cloned SstI g DNA fragment containing US (5232 bp) and adjacent portions of IRS and TRS (426 bp of each) was determined, and the following model for genetic expression was derived from an analysis of the sequence. The region specifies four mRNAs encoding primary translation products with mol. wts. of 11, 44, 39 and either 74 or 70 kd. The 39-and 70-kd proteins have primary structures characteristic of membrane proteins. The mRNAs encoding the 11- and 74/70-kd proteins extend from opposite sides of US into IRS/TRS, thus sharing a common 3' terminus. These proteins do not share a common carboxy terminus because the coding region for the 11-kd protein terminates at the junction between US and IRS, whereas that for the 74/70-kd protein extends into TRS. The analysis affirms the hypothesis that the extent of inverted repeats in herpesvirus genomes is primarily a result of constraints imposed by adjacent protein coding sequences.

DNA mapping of paired varicella-zoster virus isolates from patients with shingles

Varicella-zoster virus (VZV) was isolated from two separate sites in each of three patients with shingles (herpes zoster). The DNAs of the six VZV isolates were compared by high-resolution restriction endonuclease analysis with HindIII, KpnI, and HpaI. DNA cleavage patterns for each pair of VZV isolates were indistinguishable. These studies suggest that clinical shingles is the manifestation of a single VZV strain that becomes reactivated and causes both a viraemia and a dermatomal exanthem.

Molecular cloning of the varicella-zoster virus genome and derivation of six restriction endonuclease maps

KpnI and SstI fragments representing 96% of the varicella-zoster virus genome, including the termini, were cloned in plasmid vector pAT153. The clones were used to derive maps of virion DNA for SstI, KpnI, XhoI, PvuII, EcoRI and SalI by molecular hybridization and restriction endonuclease digestion.