Whole genome phylogenetic analysis in this study resolved a total of five major genotypes among the 22 varicella-zoster virus (VZV) strains or isolates for which complete genomic sequences are available. Consistent with earlier publications we have designated these genotypes European 1 (E1), European 2 (E2), Japanese (J), mosaic 1 (M1), and mosaic 2 (M2). Single nucleotide polymorphism (SNP) analysis performed in a whole-genome alignment revealed that VZV isolates of all five genotypes can be accurately genotyped using SNPs from two amplicons: open reading frame 22 (ORF22) and either ORF21 or ORF50. This modified approach identifies all of the genotypes observed using any of the published genotyping protocols. Of 165 clinical varicella and zoster isolates from Australia and New Zealand typed using this approach, 67 of 127 eastern Australian isolates were E1, 30 were E2, 16 were J, 10 were M1, and 4 were M2; 25 of 38 New Zealand isolates were E1, 8 were E2, and 5 were M1. VZV strain diversity in eastern Australia is thus broader than has been described for any other region, including Europe, Africa, and North America. J strains were far more prevalent than previously observed in countries other than Japan. Two-amplicon typing was in complete accord with genotypes derived using SNP in multiple ORFs (ORFs 1, 21, 22, 38, 50, 54, and 62). Two additional minor genotypes, M3 and M4, could also be resolved using two-amplicon typing.Varicella (chickenpox) results from primary infection with varicella-zoster virus (VZV), which characteristically occurs early in life and usually follows a benign course (1). A lifelong latent infection is established on first exposure and can reactivate, typically after age 50, to cause zoster (shingles). VZV can be transmitted to susceptible persons from either disease condition, although zoster carries a significantly lower risk of transmission. Transmission from zoster can reintroduce strains that were circulating decades earlier and, as such, likely contributes to the genetic stability of VZV. The epidemiology of VZV infection varies geographically. Varicella displays a marked seasonality (peaking in late winter or spring) in temperate climates, and infection is nearly ubiquitous by age 20. For reasons that remain unclear, seasonality does not occur in tropical countries, and a larger proportion of people enter adulthood uninfected by VZV (14, 15). In addition, several studies have demonstrated a distinctive geographic distribution of the major VZV genotypes aligning with cool versus warm global climates (2,18,28). It is unclear whether the strain distribution is actually driven primarily by climate or by other factors, such as immigration patterns.A number of methods have been reported for identifying and genotyping VZV strains (4,18,21). Early VZV typing efforts relied on DNA restriction fragment length polymorphism (RFLP) analysis, an approach that first demonstrated the high degree of sequence conservation among VZV strains. Nevertheless, some intrastrain variation among wild-type i...

Phylogenetic analysis of 19 complete VZV genomic sequences resolves wild-type strains into 5 genotypes (E1, E2, J, M1, and M2). Complete sequences for M3 and M4 strains are unavailable, but targeted analyses of representative strains suggest they are stable, circulating VZV genotypes. Sequence analysis of VZV isolates identified both shared and specific markers for every genotype and validated a unified VZV genotyping strategy. Despite high genotype diversity no evidence for intra-genotypic recombination was observed. Five of seven VZV genotypes were reliably discriminated using only four single nucleotide polymorphisms (SNP) present in ORF22, and the E1 and E2 genotypes were resolved using SNP located in ORF21, ORF22 or ORF50. Sequence analysis of 342 clinical varicella and zoster specimens from 18 European countries identified the following distribution of VZV genotypes: E1, 221 (65%); E2, 87 (25%); M1, 20 (6%); M2, 3 (1%); M4, 11 (3%). No M3 or J strains were observed.

Thirty-one isolates from France and Spain were genotyped using a published method analyzing DNA sequence variation in open reading frame (ORF) 22, together with an evaluation of three well-characterized single nucleotide polymorphisms (SNP) in ORF 38, 54, and 62. Nineteen were allocated to the European (E) genotype, six were mosaic-1 (M1), and two were mosaic-2 (M2). Four strains were assigned to a new genotype, mosaic-4 (M4). All isolates were wild type, with no Oka vaccine-associated markers. No isolates of the mosaic-3 (M3) or Japanese (J) genotype were observed. We also evaluated 13 selected isolates of E, J, M1, and M2 strains (9 of the 31 described above) using an alternative genotyping method based on the assessment of multiple SNP located in ORF 1, 9, 10, 21, 31, 50, 54, 62, and 68. This method assigns wild-type varicella-zoster virus (VZV) strains to seven genotypes: A1, A2, J1, B1, B2, C, and C1. VZV isolates identified as E (ORF22 method) had the genetic signature of genotype C VZV strains, M1 strains were A1, and M2 were A2. No J strains were detected, but parental Oka and vaccine Oka (genotype J) corresponded to genotype J1. M4 isolates (B) share the SNP array observed for M1 and E viruses, and probably represent recombinants between African-Asian (M1) and European (E) viruses. The two genotyping methods, using entirely different genomic targets, produced identical clusters for the strains examined, suggesting robust phylogenetic linkages among VZV strains circulating in Europe.

Little is known about the pathogenic potential of individual strains in the varicella vaccine. We analyzed genomic variation among specimens obtained from vaccine recipients with postvaccination rash or herpes zoster (HZ), focusing on polymorphisms between live attenuated varicella vaccine virus and wild-type varicella-zoster virus. Eleven of 18 postvaccination HZ specimens contained >1 strain, and 7 of 18 appeared to be clonal. All 21 postvaccination rash specimens contained mixtures of vaccine strains. Four single-nucleotide polymorphisms (SNPs) consistently occurred in every isolate; all were polymorphisms in open-reading frame (ORF) 62, and 2 confer amino acid substitutions in the immediate-early protein 62. Four wild-type SNPs occurred in every isolate: one each occurred in ORF 10, ORF 21, ORF 62, and a noncoding region upstream of ORF 64. The frequencies of the remaining wild-type SNPs were variable, with the SNPs uniformly expressed (even in mixtures) in 20.5%-97.4% of isolates (mean frequency, 67.7%). No 2 clinical isolates had identical SNP profiles; as such, vaccine latency usually involves >1 strain.

No abstract

Varicella (chickenpox) is a widespread, highly contagious disease caused by varicella-zoster virus (VZV). Serious complications of varicella include secondary bacterial infection, pneumonia, encephalitis, congenital infection, and, rarely, death (4, 21). Following the acute infection, VZV establishes a lifelong latent infection in neurosensory ganglia that commonly reactivates to cause zoster, typically in elderly or immunocompromised patients (24). A safe and effective live-attenuated varicella vaccine was developed in 1968 and has been licensed and recommended in the United States since 1995 (25). Commercial varicella vaccines (all of which are derived from the Japanese Oka strain) have never been cloned, and complete genomic sequencing of the V-Oka-Biken vaccine revealed that it contained several strains that could be separated in tissue culture (9, 10). Three manufacturers (Merck & Co Inc., Pasteur Merieux Connaught, and Biken Inc.) accepted the original V-Oka vaccine preparations, and each has the vaccine in production, with some variation in manufacturing processes. GlaxoSmithKline (Uxbridge, United Kingdom) reported the use of a selected, plaque-purified variant of V-Oka vaccine (2, 7). V-Oka has been used successfully for vaccination in the United States, Canada, Australia, Japan, and South Korea. In some European countries, varicella vaccination is recommended for persons at risk of severe chickenpox and/or for seronegative health care workers. Germany also recommends varicella vaccination for adolescents with no history of chickenpox (23). The vaccine provides 90% protection from any disease and over 95% protection from moderate to severe disease (8).V-Oka is known to establish latent infection in the dorsal root ganglia, and zoster has been demonstrated as a rare adverse consequence among vaccinees (8,13,14,22,26). However, in all of these cases, the status of vaccine-specific mutations was not documented. In addition, the primary DNA sequence was not compared to that of the material used for vaccination. Until recently, laboratories evaluated only three single nucleotide polymorphism (SNP) mutations in open reading frames (ORFs) 38, 54, and 62 to differentiate V-Oka from wild-type strains, but only the ORF 62 SNP reliably differentiates Japanese genotype wild-type strains from vaccine (15,20). Conceivably, genomic mutations or reversions to wild type, particularly those that confer amino acid substitutions, could affect virulence and restore wild-type pathogenicity. Furthermore, VZV strains with unique pathogenic qualities could emerge. The comparison of DNA sequences between V-Oka and P-Oka revealed 42 base substitutions associated with 20 amino acid changes (11). Specific amino acid substitutions in ORF 62 have been associated with enhanced virus growth and spread in cell culture, and substrains purified from the vaccine mixture display variable properties in cell culture (11).This study sought to compare vaccine mutations associated with amino acid changes in V-Oka-GSK to published V-OkaBiken and ...

No abstract

We evaluated the seroprevalence of varicella-zoster virus (VZV) in the Finnish population among various age groups and genetically characterized VZV strains from documented cases of varicella and zoster. VZV-specific immunoglobulin G was measured in 2,842 serum samples that had been submitted for virological studies to the Department of Virology, University of Helsinki, from 1995 to 1996. Specimens for VZV genotyping were obtained from vesicular lesions from two pediatric patients and 26 adult patients. Seroprevalence to VZV varied markedly by age: 45% in children aged <2 months, 12.5% in children aged 6 to 8 months, and >90% in children near 10 years of age, plateauing thereafter into advanced age. The seroprevalence rates indicate that in Finland, as in other countries with temperate climates, primary VZV infection usually occurs during the first decade of life. Twenty-eight VZV DNA-positive specimens were analyzed to identify VZV vaccine and wild-type genotypes. All analyzed specimens were wild type and the European (E) genotype.Varicella zoster virus (VZV) is a common, globally distributed virus that causes chickenpox upon primary infection; it is normally associated with a generalized vesicular rash but may rarely occur without obvious dermal lesions. VZV establishes lifelong latency upon first infection and can reactivate, usually in the elderly, to cause shingles (herpes zoster) (2,12,13,15,34). Patient age is often related to disease severity, with the greatest risk occurring among the very young and very old; immunocompromised persons are also at elevated risk for severe disease (7,11,14). Varicella vaccine use in Finland is currently limited to children with recognized immunosuppression due to leukemia, bone marrow transplant, et cetera. The seroprevalence rate for VZV varies among different populations, and lower prevalence rates have generally been observed in tropical versus temperate climates (9,21,26,27). Over the past 25 years, there has been an evident increase in VZV seroprevalence among children 1 to 4 years of age in the United Kingdom (21). In Finland, VZV has become the agent most frequently associated with central nervous system infections, particularly encephalitis, for all age groups (18,22). Currently, several methods are being used to identify and genotype VZV strains. A variety of methods have been explored for genotyping VZV both to discern strain variation and to discriminate vaccine strains from wild-type isolates (3,4,6,8,10,16,18,23,24,31,36).We developed a novel strategy for VZV genotyping based on the complete sequencing of a short region in open reading frame 22 (ORF22) using material obtained directly from clinical samples (29). By sequencing a collection of 321 contemporary VZV isolates representing multiple countries and six continents, we sorted strains into three discrete geographically associated genotypes: E (European), J (Japanese), and M (mosaic). M strains were dominant in tropical latitudes, and J and E VZV isolates prevail in temperate climate latitudes (29). Genot...