Genetic profile of an Oka varicella vaccine virus variant isolated from an infant with zoster

Skin manifestations after immunisation with an adjuvanted recombinant zoster vaccine, Germany, 2020

BackgroundShortly after the launch of a novel adjuvanted recombinant zoster vaccine (RZV), Shingrix, cases of suspected herpes zoster (HZ) or zoster-like skin reactions following immunisation were reported.AimWe aimed to investigate if these skin manifestations after administration of RZV could be HZ.MethodsBetween April and October 2020, general practitioners (GP) reporting a suspected case of HZ or zoster-like skin manifestation after RZV vaccination to the Paul-Ehrlich-Institut, the German national competent authority, were invited to participate in the study. The GP took a sample of the skin manifestation, photographed it and collected patient information on RZV vaccination and the suspected adverse event. We analysed all samples by PCR for varicella-zoster virus (VZV) and herpes-simplex virus (HSV) and genotyped VZV-positive samples. In addition, cases were independently assessed by two dermatologists.ResultsEighty eligible cases were enrolled and 72 could be included in the analysis. Of the 72 cases, 45 were female, 33 were 60-69 years old, 32 had skin symptoms in the thoracic and 27 in the cervical dermatomes. Twenty-seven samples tested PCR positive for VZV (all genotyped as wild-type, WT), three for HSV-1 and five for HSV-2.ConclusionIt may be difficult to distinguish HZ, without a PCR result, from other zoster-like manifestations. In this study, VZV-PCR positive dermatomal eruptions occurring in the first weeks after immunisation with RZV were due to WT VZV, which is not unexpected as HZ is a common disease against which the vaccine is unlikely to provide full protection at this time.

Treatment with Brivudine in Immunocompromised Pediatric Patients with Herpes Zoster

INTRODUCTION

Herpes zoster (HZ) is caused by endogenous reactivation of latent varicella-zoster virus (VZV) that persists in sensory ganglia after primary infection. The incidence and severity of HZ increase during immunosuppression. Especially, immunocompromised patients are at high risk of developing a cutaneous rash and suffering from delayed healing of lesions. Bromovinyl deoxyuridine (brivudine), one of the most potent oral inhibitors of VZV replication, is widely used in the therapy of HZ in adult patients, particularly in Europe. In this study, we investigated the efficacy of brivudine in immunocompromised children to provide an outpatient treatment option.

METHODS

In this retrospective study, we included 64 immunocompromised pediatric patients with a median age of 14 years. Forty-seven patients received immunosuppressive therapy as part of hematopoietic stem cell transplantation and 17 patients as part of chemotherapy. Primary diagnosis was made clinically by examining the nature and the localization of the skin lesions. Laboratory confirmation was conducted based on the detection of VZV DNA in vesicle fluid and blood samples. Brivudine was administered orally at a single dose of 2 mg/kg per day. We monitored the patients' response for the full time of treatment and observed the time of full crusting of lesions, loss of crusts, and any adverse effects that occurred.

RESULTS

Patients received medication for 7-21 days (median: 14 days). All children responded promptly to antiviral treatment and recovered completely from their HZ infections without complications. Crusting of lesions was reached after 3-14 days (median: 6 days). Full healing of skin lesions was ascertained within 7-21 days (median: 12 days). Overall, brivudine therapy was well tolerated. No clinical side effects during or after the treatment were observed. High compliance was achieved due to the once-daily dosing regimen. All patients were treated in an outpatient manner.

CONCLUSION

Oral brivudine was a very effective and well-tolerated therapy in immunocompromised children with HZ infection. The oral administration offers the potential for outpatient treatment of HZ in these patients.

Meningitis without Rash after Reactivation of Varicella Vaccine Strain in a 12-Year-Old Immunocompetent Boy

Acute neurologic complications from Varicella-Zoster-Virus reactivation occur in both immunocompromised and immunocompetent patients. In this report, we describe a case of a previously healthy immunocompetent boy who had received two doses of varicella vaccine at 1 and 4 years. At the age of 12 he developed acute aseptic meningitis caused by vaccine-type varicella-zoster-virus without concomitant skin eruptions. VZV-vaccine strain DNA was detected in the cerebrospinal fluid. The patient made a full recovery after receiving intravenous acyclovir therapy. This disease course documents another case of a VZV vaccine-associated meningitis without development of a rash, i.e., a form of VZV infection manifesting as "zoster sine herpete".

Genotype analysis of ORF 62 identifies varicella-zoster virus infections caused by a vaccine strain in children

This study was performed to differentiate vaccine-type strains from wild-type strains and determine the genotype of varicella-zoster virus (VZV) in 51 Korean children. A sequencing analysis of ORF 62 identified two cases of herpes zoster caused by the vaccine-type virus, without a previous history of varicella, 22 months and 5 months after VZV vaccination. The wild-type strain was identified in the remaining children. A genotype analysis of ORF 22 amino acids revealed genotype J in all children except one. Genotype E was identified in an infant with varicella imported from Egypt.

Deep Sequencing of Distinct Preparations of the Live Attenuated Varicella-Zoster Virus Vaccine Reveals a Conserved Core of Attenuating Single-Nucleotide Polymorphisms

The continued success of the live attenuated varicella-zoster virus vaccine in preventing varicella-zoster and herpes zoster is well documented, as are many of the mutations that contribute to the attenuation of the vOka virus for replication in skin. At least three different preparations of vOka are marketed. Here, we show using deep sequencing of seven batches of vOka vaccine (including ZostaVax, VariVax, VarilRix, and the Oka/Biken working seed) from three different manufacturers (VariVax, GSK, and Biken) that 137 single-nucleotide polymorphism (SNP) mutations are present in all vaccine batches. This includes six sites at which the vaccine allele is fixed or near fixation, which we speculate are likely to be important for attenuation. We also show that despite differences in the vaccine populations between preparations, batch-to-batch variation is minimal, as is the number and frequency of mutations unique to individual batches. This suggests that the vaccine manufacturing processes are not introducing new mutations and that, notwithstanding the mixture of variants present, VZV live vaccines are extremely stable.

IMPORTANCE

The continued success of vaccinations to prevent chickenpox and shingles, combined with the extremely low incidence of adverse reactions, indicates the quality of these vaccines. The vaccine itself is comprised of a heterogeneous live attenuated virus population and thus requires deep-sequencing technologies to explore the differences and similarities in the virus populations between different preparations and batches of the vaccines. Our data demonstrate minimal variation between batches, an important safety feature, and provide new insights into the extent of the mutations present in this attenuated virus.

Analysis of single nucleotide polymorphism among Varicella-Zoster Virus and identification of vaccine-specific sites

Varicella-zoster virus (VZV) is a causative agent for chickenpox and zoster. Live attenuated vaccines have been developed based on Oka and MAV/06 strains. In order to understand the molecular mechanisms of attenuation, complete genome sequences of vaccine and wild-type strains were compared and single nucleotide polymorphism (SNP) was analyzed. ORF22 and ORF62 contained the highest number of SNPs. The detailed analysis of the SNPs suggested 24 potential vaccine-specific sites. All the mutational events found in vaccine-specific sites were transitional, and most of them were substitution of AT to GC pair. Interestingly, 18 of the vaccine-specific sites of the vaccine strains appeared to be genetically heterogeneous. The probability of a single genome of vaccine strain to contain all 24 vaccine-type sequences was calculated to be less than 4%. The average codon adaptation index (CAI) value of the vaccine strains was significantly lower than the CAI value of the clinical strains.

Autoimmune disease and vaccination: impact on infectious disease prevention and a look at future applications

Vaccines hold promise both for the prevention of infections and as potential immunologic therapy for patients with autoimmune disease (AD). These patients are at high risk for both common and opportunistic infections, but this risk can be significantly reduced and even obviated with the use of recommended available vaccines. Unfortunately, patients with ADs are not routinely offered or provided indicated vaccinations and have higher rates of complications from vaccine-preventable illnesses than patients without ADs. In addition, vaccine therapy is currently under study for the treatment of autoimmune disorders, with early studies demonstrating immunomodulatory effects that may counter undesired immune activation and alleviate disease activity.

Clinical and molecular aspects of the live attenuated Oka varicella vaccine

VZV is a ubiquitous member of the Herpesviridae family that causes varicella (chicken pox) and herpes zoster (shingles). Both manifestations can cause great morbidity and mortality and are therefore of significant economic burden. The introduction of varicella vaccination as part of childhood immunization programs has resulted in a remarkable decline in varicella incidence, and associated hospitalizations and deaths, particularly in the USA. The vaccine preparation, vOka, is a live attenuated virus produced by serial passage of a wild-type clinical isolate termed pOka in human and guinea pig cell lines. Although vOka is clinically attenuated, it can cause mild varicella, establish latency, and reactivate to cause herpes zoster. Sequence analysis has shown that vOka differs from pOka by at least 42 loci; however, not all genomes possess the novel vOka change at all positions, creating a heterogeneous population of genetically distinct haplotypes. This, together with the extreme cell-associated nature of VZV replication in cell culture and the lack of an animal model, in which the complete VZV life cycle can be replicated, has limited studies into the molecular basis for vOka attenuation. Comparative studies of vOka with pOka replication in T cells, dorsal root ganglia, and skin indicate that attenuation likely involves multiple mutations within ORF 62 and several other genes. This article presents an overview of the clinical aspects of the vaccine and current progress on understanding the molecular mechanisms that account for the clinical phenotype of reduced virulence.

Novel genetic variation identified at fixed loci in ORF62 of the Oka varicella vaccine and in a case of vaccine-associated herpes zoster

The live attenuated Oka varicella vaccine (vOka), derived from clade 2 wild-type (wt) virus pOka, is used for routine childhood immunization in several countries, including the United States, which has caused dramatic declines in the incidence of varicella. vOka can cause varicella, establish latency, and reactivate to cause herpes zoster (HZ). Three loci in varicella-zoster virus (VZV) open reading frame 62 (ORF62) (106262, 107252, and 108111) are used to distinguish vOka from wt VZV. A fourth position (105705) is also fixed for the vOka allele in nearly all vaccine batches. These 4 positions and two vOka mutations (106710 and 107599) reportedly absent from Varivax were analyzed on Varivax-derived ORF62 TOPO TA clones. The wt allele was detected at positions 105705 and 107252 on 3% and 2% of clones, respectively, but was absent at positions 106262 and 108111. Position 106710 was fixed for the wt allele, whereas the vOka allele was present on 18.4% of clones at position 107599. We also evaluated the 4 vOka markers in an isolate obtained from a case of vaccine-caused HZ. The isolate carried the vOka allele at positions 105705, 106262, and 108111. However, at position 107252, the wt allele was present. Thus, all of the ORF62 vOka markers previously regarded as fixed occur as the wt allele in a small percentage of vOka strains. Characterization of all four vOka markers in ORF62 and of the clade 2 subtype marker in ORF38 is now necessary to confirm vOka adverse events.

Molecular analysis of varicella vaccines and varicella-zoster virus from vaccine-related skin lesions

To prevent complications that might follow an infection with varicella-zoster virus (VZV), the live attenuated Oka strain (V-Oka) is administered to children in many developed countries. Three vaccine brands (Varivax from Sanofi Pasteur MSD; Varilrix and Priorix-Tetra, both from Glaxo-Smith-Kline) are licensed in Germany and have been associated with both different degrees of vaccine effectiveness and adverse effects. To identify genetic variants in the vaccines that might contribute to rash-associated syndromes, single nucleotide polymorphism (SNP) profiles of variants from the three vaccines and rash-associated vaccine-type VZV from German vaccinees were quantitatively compared by PCR-based pyrosequencing (PSQ). The Varivax vaccine contained an estimated 3-fold higher diversity of VZV variants, with 20% more wild-type (wt) SNPs than Varilrix and Priorix-Tetra. These minor VZV variants in the vaccines were identified by analyzing cloned full-length open reading frame (ORF) orf62 sequences by chain termination sequencing and PSQ. Some of these sequences amplified from vaccine VZV were very similar or identical to those of the rash-associated vaccine-type VZV from vaccinees and were almost exclusively detected in Varivax. Therefore, minorities of rash-associated VZV variants are present in varicella vaccine formulations, and it can be concluded that the analysis of a core set of four SNPs is required as a minimum for a firm diagnostic differentiation of vaccine-type VZV from wt VZV.

Varicella-zoster virus vaccine: molecular genetics

The genetic differences that potentially account for the attenuation of the Oka vaccine VZV preparation are more clearly defined than for perhaps any other vaccine in current use. This is due in large part to the small number of differences between the vaccine and the parental strain from which it was derived, and to the high level of genomic conservation that characterizes VZV. This information has been used with great success to develop methods that discriminate vaccine from wild-type strains, to begin determining which specific vaccine markers contribute to the attenuated phenotype, to improve evaluations of vaccine efficacy and safety, and to observe the behavior of the live, attenuated preparation as it becomes more prevalent through widespread immunization.

Distribution of varicella-zoster virus (VZV) wild-type genotypes in northern and southern Europe: evidence for high conservation of circulating genotypes

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.

Complete DNA sequences of two oka strain varicella-zoster virus genomes

Varicella-zoster virus (VZV) is a herpesvirus and is the causative agent of chicken pox (varicella) and shingles (herpes zoster). Active immunization against varicella became possible with the development of live attenuated varicella vaccine. The Oka vaccine strain was isolated in Japan from a child who had typical varicella, and it was then attenuated by serial passages in cell culture. Several manufacturers have obtained this attenuated Oka strain and, following additional passages, have developed their own vaccine strains. Notably, the vaccines Varilrix and Varivax are produced by GlaxoSmithKline Biologicals and Merck & Co., Inc., respectively. Both vaccines have been well studied in terms of safety and immunogenicity. In this study, we report the complete nucleotide sequence of the Varilrix (Oka-V(GSK)) and Varivax (Oka-V(Merck)) vaccine strain genomes. Their genomes are composed of 124,821 and 124,815 bp, respectively. Full genome annotations covering the features of Oka-derived vaccine genomes have been established for the first time. Sequence analysis indicates 36 nucleotide differences between the two vaccine strains throughout the entire genome, among which only 14 are involved in unique amino acid substitutions. These results demonstrate that, although Oka-V(GSK) and Oka-V(Merck) vaccine strains are not identical, they are very similar, which supports the clinical data showing that both vaccines are well tolerated and elicit strong immune responses against varicella.

Vaccine Oka variants and sequence variability in vaccine-related skin lesions

As with most live attenuated viral vaccines, varicella vaccine comprises a mixture of variant strains. Knowledge about the pathogenic potential of individual strains in the varicella vaccine is limited. Vaccination against chickenpox causes a usually modified varicella-like rash in a small percentage of healthy children, and vaccine virus reactivates on rare occasions to cause herpes zoster (HZ). In several published studies, our respective laboratories have analyzed genomic variation among specimens from cases of postvaccination rash and HZ in vaccine recipients, focusing on polymorphisms between vaccine Oka strains and the parental Oka strain. In most respects, these studies were in close agreement, identifying the set of wild-type markers among vaccine adverse event isolates, each occurring at similar frequencies. The same 3 universally present vaccine markers, at positions 106262, 107252, and 108111, were also identified by both laboratories. One notable difference has been the observation of mostly clonal vaccine virus among isolates examined by one laboratory and mostly mixed viruses in isolates examined by the other. In addition to reviewing and comparing our combined observations, we propose possible explanations for our contrasting findings and propose future studies to reconcile them.

Identification of five major and two minor genotypes of varicella-zoster virus strains: a practical two-amplicon approach used to genotype clinical isolates in Australia and New Zealand

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.

Complete-genome phylogenetic approach to varicella-zoster virus evolution: genetic divergence and evidence for recombination

Recent studies of varicella-zoster virus (VZV) DNA sequence variation, involving large numbers of globally distributed clinical isolates, suggest that this virus has diverged into at least three distinct genotypes designated European (E), Japanese (J), and mosaic (M). In the present study, we determined and analyzed the complete genomic sequences of two M VZV strains and compared them to the sequences of three E strains and two J strains retrieved from GenBank (including the Oka vaccine preparation, V-Oka). Except for a few polymorphic tandem repeat regions, the whole genome, representing approximately 125,000 nucleotides, is highly conserved, presenting a genetic similarity between the E and J genotypes of approximately 99.85%. These analyses revealed that VZV strains distinctly segregate into at least four genotypes (E, J, M1, and M2) in phylogenetic trees supported by high bootstrap values. Separate analyses of informative sites revealed that the tree topology was dependent on the region of the VZV genome used to determine the phylogeny; collectively, these results indicate the observed strain variation is likely to have resulted, at least in part, from interstrain recombination. Recombination analyses suggest that strains belonging to the M1 and M2 genotypes are mosaic recombinant strains that originated from ancestral isolates belonging to the E and J genotypes through recombination on multiple occasions. Furthermore, evidence of more recent recombination events between M1 and M2 strains is present in six segments of the VZV genome. As such, interstrain recombination in dually infected cells seems to figure prominently in the evolutionary history of VZV, a feature it has in common with other herpesviruses. In addition, we report here six novel genomic targets located in open reading frames 51 to 58 suitable for genotyping of clinical VZV isolates.

Genotyping of different varicella vaccine strains

BACKGROUND

Little is known about single nucleotide polymorphism (SNP) in different lots of varicella vaccines distributed by the manufacturers. Recently, the genetic analysis of several genomic regions revealed a polymorphism in different vaccine lots of Varilrix manufactured by GlaxoSmithKline. These findings need attention since mutations in the vaccine strain could result in changes of virulence and efficacy of the vaccine.

OBJECTIVES

To identify SNPs in three varicella vaccine lots of Varilrix and to compare the results with that of Varivax as well as the published sequences of the Oka vaccine strain (V-Oka) and its parental virus (P-Oka).

STUDY DESIGN

The open reading frames (ORF) 1, 6, 10, 21, 50, 54, and 62 were analyzed by sequencing of amplified DNA fragments.

RESULTS

Wild-type nucleotides identical to that of P-Oka and/or the European wild-type reference strain Dumas and in contrast to V-Oka could be identified in ORF 1 of a Varilrix vaccine lot distributed in 1991. In the ORF 62 probably responsible for attenuation of V-Oka, this vaccine strain contained 16 SNPs which were nearly all wild-type-like. By contrast, different lots of the Varivax vaccine revealed uniform sequencing results. The vaccine Varilrix 1999 showed a high similarity to the Varivax vaccine currently available.

CONCLUSIONS

The obvious genetic diversity of different lots of the varicella vaccine Varilrix cannot be explained with the coexistence of several strain variants in the vaccine, but most likely with different seed lot preparations used for vaccine production.

Secondary transmission of varicella vaccine virus in a chronic care facility for children

A 16-year-old varicella-seronegative resident at a chronic care facility received varicella vaccine; 15 days later he developed severe varicella. Subsequently, a 13-year-old resident and a 39-year-old health care worker developed mild varicella. We demonstrate that vaccine-strain virus was transmitted to both persons, and that transmission included at least 2 variant vaccine strains.