Are false negative direct immnufluorescence assays caused by varicella zoster virus gE mutant strains?

Molecular Genetic Insights Into Varicella Zoster Virus (VZV), the vOka Vaccine Strain, and the Pathogenesis of Latency and Reactivation

Genetic tools for molecular typing of varicella zoster virus (VZV) have been used to understand the spread of virus, to differentiate wild-type and vaccine strains, and to understand the natural history of VZV infection in its cognate host. Molecular genetics has identified 7 clades of VZV (1-6 and 9), with 2 more mooted. Differences between the vOka vaccine strain and wild-type VZVs have been used to distinguish the cause of postimmunization events and to provide insight into the natural history of VZV infections. Importantly molecular genetics has shown that reinfection with establishment of latency by the reinfecting strain is common, that dual infections with different viruses can occur, and that reactivation of the superinfecting genotype can both occur. Whole-genome sequencing of the vOka vaccine has been used to show that vesicles form from a single virion, that latency is established within a few days of inoculation, and that all vaccine strains are capable of establishing latency and reactivating. Novel molecular tools have characterized the transcripts expressed during latent infection in vitro.

Varicella zoster virus in solid organ transplantation: Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

These updated guidelines from the American Society of Transplantation Infectious Diseases Community of Practice review the diagnosis, prevention, and management of varicella zoster virus (VZV) in the pre- and post-transplant period. Primary varicella is an uncommon complication post-solid-organ transplant (SOT), except among pediatric transplant patients and those seronegative for VZV. As the majority of SOT recipients are seropositive for VZV, herpes zoster (HZ) occurs frequently following SOT, particularly among recipients who are older (≥65 years of age) and those receiving more intensive immunosuppression. Transplant providers should aware of the increased risk for HZ-related complications such as dissemination, organ-specific involvement, and post-herpetic neuralgia. Treatment for localized zoster is primarily given as oral regimens, but those with more complicated presentations or those at risk for dissemination should be treated initially with IV therapy. Available antiviral prophylaxis regimens and vaccination strategies for varicella and HZ among these immunosuppressed patients remain a mainstay for prevention in the pre-and post-transplant periods. Finally, we discuss important approaches to addressing post-exposure prophylaxis and infection control practices for those SOT patients with documented VZV infections.

Clinical utility of loop-mediated isothermal amplification assay for the diagnosis of common alpha herpesvirus skin infections

Loop-mediated isothermal amplification (LAMP) is a nucleic acid amplification method with a high specificity, efficiency and speed. No reports exist regarding the usefulness of LAMP for clinically suspected skin infections caused by herpes simplex virus (HSV) or varicella zoster virus (VZV). The aim of this study was to evaluate the clinical usefulness of LAMP in the diagnosis of common cutaneous alpha herpesvirus (HSV type 1 and 2, and VZV) infections. LAMP and real-time polymerase chain reaction (PCR) were performed using swab samples collected from 106 patients with clinically suspected alpha herpesvirus skin infections. The results of LAMP performed with DNA extraction did not differ from those performed without DNA extraction. The sensitivity of LAMP tested against real-time PCR was 96% in herpes simplex, 78% in eczema herpeticum, 93% in herpes zoster and 100% in varicella. No viral DNA was detected by LAMP in all negative real-time PCR samples. Viral DNA load was significantly lower in samples with false-negative LAMP results than in the LAMP-positive samples. LAMP enables confirmation of clinically suspected cutaneous HSV and VZV infections. However, the sensitivity of LAMP is lower than real-time PCR. The accuracy of LAMP may increase if sufficient viral DNA is obtained from lesions. LAMP performed without DNA extraction remains sensitive; thus, LAMP represents a quick and economical method for the diagnosis of common alpha herpesvirus skin infections.

Varicella zoster virus (VZV) and herpes simplex virus (HSV) in solid organ transplant patients

Varicella zoster virus (VZV) and the two herpes simplex viruses (HSV) are human α-herpesviruses that establish life-long latency in neural ganglia after initial primary infection. In the solid organ transplant (SOT) population, manifestations of VZV or HSV may be seen in up to 70% of recipients if no prophylaxis is used, some of them life and organ threatening. While there are effective vaccines to prevent VZV primary infection and reactivation in immunocompetent adults, these vaccines are contraindicated after SOT because they are live-virus vaccines. For HSV, prevention has focused primarily on antiviral strategies because the immunologic correlates of protection and control are different from VZV, making vaccine development more challenging. Current antiviral therapy remains effective for the majority of clinical VZV and HSV infections.

VZV molecular epidemiology

The molecular epidemiology of varicella zoster virus (VZV) has led to an understanding of virus evolution, spread, and pathogenesis. The availability of over 20 full length genomes has confirmed the existence of at least five virus clades and generated estimates of VZV evolution, with evidence of recombination both past and ongoing. Genotyping by restriction enzyme analysis (REA) and single nucleotide polymorphisms (SNP) has proven that the virus causing varicella is identical to that which later reactivates as zoster in an individual. Moreover, these methods have shown that reinfection, which is mostly asymptomatic, may also occur and the second virus may establish latency and reactivate. VZV is the only human herpesvirus that is spread by the respiratory route. Genotyping methods, together with epidemiological data and modeling, have provided insights into global differences in the transmission patterns of this ubiquitous virus.

A novel varicella-zoster virus gE mutation discovered in two Swedish isolates

BACKGROUND

Two VZV glycoprotein E (gE D150N) mutant strains were collected in North America in 1995 and in 1999. We now report a novel VZV gE mutant virus discovered in Europe in two VZV strains collected in Stockholm, Sweden, in 1990 and 1999.

OBJECTIVES

To characterize the two isolates identified among a total of 634 VZV isolates collected over a 15-year period at the Karolinska University Hospital.

STUDY DESIGN

VZV genes were amplified by polymerase chain reaction and their sequences were compared to the genomic sequence of VZV-Dumas prototype strain.

RESULTS

A mutation within the gE gene in an epitope recognized by the 3B3 monoclonal antibody was identified in both isolates. A different residue was changed (R152S) compared to the North American strains (D150N).

CONCLUSIONS

The occurrence of a VZV gE mutant virus is unusual, but probably a recurring event in Europe and North America. It is unknown whether widespread varicella vaccination programs will alter the rate at which these mutant viruses are isolated.

Predicting and preventing post-herpetic neuralgia: are current risk factors useful in clinical practice?

Post-herpetic neuralgia (PHN) following acute herpes zoster remains a significant cause of neuropathic pain especially in the elderly. Early treatment of the zoster rash with antiviral agents, such as aciclovir remains one of the few measures proven to reduce the incidence and duration of PHN albeit only in a subset of patients. It is therefore crucial that the physician who first sees a case of zoster identifies those patients who are most likely to develop long-term pain and treats them accordingly. In particular, prodrugs such as famciclovir and valaciclvoir may be more beneficial in reducing PHN than the shorter acting aciclovir, but can be more expensive. Measures that could be used to predict patients likely to develop PHN would also facilitate the evaluation of early use of antiepileptic, anti-inflammatory and analgesic agents in the prevention of PHN. In a prospective study of 280 herpes zoster (HZ) cases seen by the general practitioner (GP) we evaluated the predictive value of five clinical factors identified in clinical trials as associated with a higher likelihood of PHN. A visual analogue score (VAS) over 5 and/or age over 50 correctly identified all subjects with PHN at 3 and 6 months, respectively. However, the specificity of this prediction was low because as many as 81% and 85% of those aged over 50 recovered within 3 and 6 months, respectively. Better methods are needed to identify patients over 50 at most risk of PHN that enable GPs to better allocate their resources with respect to HZ treatment.