Herpes Simplex Virus Mistyping due to HSV-1 × HSV-2 Interspecies Recombination in Viral Gene Encoding Glycoprotein B

Human herpes simplex viruses (HSV) 1 and 2 are extremely common human pathogens with overlapping disease spectra. Infections due to HSV-1 and HSV-2 are distinguished in clinical settings using sequence-based "typing" assays. Here we describe a case of HSV mistyping caused by a previously undescribed HSV-1 × HSV-2 recombination event in UL27, the HSV gene that encodes glycoprotein B. This is the first documented case of HSV mistyping caused by an HSV-1 × HSV-2 recombination event and the first description of an HSV interspecies recombination event in UL27, which is frequently used as a target for diagnostics and experimental therapeutics. We also review the primer and probe target sequences for a commonly used HSV typing assay from nearly 700 HSV-1 and HSV-2 samples and find that about 4% of HSV-1 samples have a single nucleotide change in at least one of these loci, which could impact assay performance. Our findings illustrate how knowledge of naturally occurring genomic variation in HSV-1 and HSV-2 is essential for the design and interpretation of molecular diagnostics for these viruses.

The new scope of virus taxonomy: partitioning the virosphere into 15 hierarchical ranks

Virus taxonomy emerged as a discipline in the middle of the twentieth century. Traditionally, classification by virus taxonomists has been focussed on the grouping of relatively closely related viruses. However, during the past few years, the International Committee on Taxonomy of Viruses (ICTV) has recognized that the taxonomy it develops can be usefully extended to include the basal evolutionary relationships among distantly related viruses. Consequently, the ICTV has changed its Code to allow a 15-rank classification hierarchy that closely aligns with the Linnaean taxonomic system and may accommodate the entire spectrum of genetic divergence in the virosphere. The current taxonomies of three human pathogens, Ebola virus, severe acute respiratory syndrome coronavirus and herpes simplex virus 1 are used to illustrate the impact of the expanded rank structure. This new rank hierarchy of virus taxonomy will stimulate further research on virus origins and evolution, and vice versa, and could promote crosstalk with the taxonomies of cellular organisms.

Ultrasensitive Capture of Human Herpes Simplex Virus Genomes Directly from Clinical Samples Reveals Extraordinarily Limited Evolution in Cell Culture

Herpes simplex viruses (HSVs) are difficult to sequence due to their large DNA genome, high GC content, and the presence of repeats. To date, most HSV genomes have been recovered from culture isolates, raising concern that these genomes may not accurately represent circulating clinical strains. We report the development and validation of a DNA oligonucleotide hybridization panel to recover nearly complete HSV genomes at abundances up to 50,000-fold lower than previously reported. Using copy number information on herpesvirus and host DNA background via quantitative PCR, we developed a protocol for pooling for cost-effective recovery of more than 50 HSV-1 or HSV-2 genomes per MiSeq run. We demonstrate the ability to recover >99% of the HSV genome at >100× coverage in 72 h at viral loads that allow whole-genome recovery from latently infected ganglia. We also report a new computational pipeline for rapid HSV genome assembly and annotation. Using the above tools and a series of 17 HSV-1-positive clinical swabs sent to our laboratory for viral isolation, we show limited evolution of HSV-1 during viral isolation in human fibroblast cells compared to the original clinical samples. Our data indicate that previous studies using low-passage-number clinical isolates of herpes simplex viruses are reflective of the viral sequences present in the lesion and thus can be used in phylogenetic analyses. We also detect superinfection within a single sample with unrelated HSV-1 strains recovered from separate oral lesions in an immunosuppressed patient during a 2.5-week period, illustrating the power of direct-from-specimen sequencing of HSV.IMPORTANCE Herpes simplex viruses affect more than 4 billion people across the globe, constituting a large burden of disease. Understanding the global diversity of herpes simplex viruses is important for diagnostics and therapeutics as well as cure research and tracking transmission among humans. To date, most HSV genomics has been performed on culture isolates and DNA swabs with high quantities of virus. We describe the development of wet-lab and computational tools that enable the accurate sequencing of near-complete genomes of HSV-1 and HSV-2 directly from clinical specimens at abundances >50,000-fold lower than previously sequenced and at significantly reduced cost. We use these tools to profile circulating HSV-1 strains in the community and illustrate limited changes to the viral genome during the viral isolation process. These techniques enable cost-effective, rapid sequencing of HSV-1 and HSV-2 genomes that will help enable improved detection, surveillance, and control of this human pathogen.

Novel method for genotyping clinical herpes simplex virus type 1 isolates

Up to now, three distinct genotypes, A, B and C, of herpes simplex virus type 1 (HSV-1), based on polymorphisms in the US4 and US7 genes, have been reported. Here, we propose to include an additional polymorphism of the US2 gene. The refined genotyping method was validated using 423 clinical isolates from patients with different HSV-1 diseases. The proportions of three US2 genotypes were A, 46.6%; B, 23.2%; and C, 30.2 %. Genotype A of US2 and US4/US7 showed a highly significant correlation. In addition, the frequency of genotype A was significantly higher in women than in men with herpes labialis.

[Infections caused by human alpha herpes viruses]

Varicella-zoster virus (VZV), herpes simplex virus one (HSV-1) and herpes simplex virus two (HSV-2) represent three out of the eight known human herpesviruses and belong to the subfamily of α-herpesviruses. These viruses are present worldwide and humans are their sole host and reservoir. After the primary infection, these viruses persist in the body throughout life. The period of latency may be interrupted by reactivation of infection due to various factors. Each virus can induce a wide spectrum of diseases. The primary infection is typical for children and otherwise healthy individuals are often asymptomatic. It is mainly immunocompromised patients who are at risk of developing severe disease or complications when infected by these viruses. However, even in otherwise healthy individuals an infection by a-herpesviruses can run a severe course and lead to death.

Evolutionary origins of human herpes simplex viruses 1 and 2

Herpesviruses have been infecting and codiverging with their vertebrate hosts for hundreds of millions of years. The primate simplex viruses exemplify this pattern of virus-host codivergence, at a minimum, as far back as the most recent common ancestor of New World monkeys, Old World monkeys, and apes. Humans are the only primate species known to be infected with two distinct herpes simplex viruses: HSV-1 and HSV-2. Human herpes simplex viruses are ubiquitous, with over two-thirds of the human population infected by at least one virus. Here, we investigated whether the additional human simplex virus is the result of ancient viral lineage duplication or cross-species transmission. We found that standard phylogenetic models of nucleotide substitution are inadequate for distinguishing among these competing hypotheses; the extent of synonymous substitutions causes a substantial underestimation of the lengths of some of the branches in the phylogeny, consistent with observations in other viruses (e.g., avian influenza, Ebola, and coronaviruses). To more accurately estimate ancient viral divergence times, we applied a branch-site random effects likelihood model of molecular evolution that allows the strength of natural selection to vary across both the viral phylogeny and the gene alignment. This selection-informed model favored a scenario in which HSV-1 is the result of ancient codivergence and HSV-2 arose from a cross-species transmission event from the ancestor of modern chimpanzees to an extinct Homo precursor of modern humans, around 1.6 Ma. These results provide a new framework for understanding human herpes simplex virus evolution and demonstrate the importance of using selection-informed models of sequence evolution when investigating viral origin hypotheses.

Herpesvirus entry mediator is a serotype specific determinant of pathogenesis in ocular herpes

Infection with herpes simplex virus type 1 (HSV-1) and HSV-2 is initiated by viral glycoprotein D (gD) binding to a receptor on the host cell. Two receptors, herpesvirus entry mediator (HVEM) and nectin-1, mediate entry in murine models of HSV-1 and HSV-2. HVEM is dispensable for HSV-2 infection of the vagina and brain, but is required for WT pathogenesis of HSV-1 infection of the cornea. By challenging WT and HVEM KO mice with multiple strains of HSV-1 and HSV-2, we demonstrate that without HVEM, all HSV-1 strains tested do not replicate well in the cornea and infection does not result in severe symptoms, as observed in WT mice. In contrast, all HSV-2 strains tested had no requirement for HVEM to replicate to WT levels in the cornea and still cause severe disease. These findings imply that HSV-2 does not require HVEM to cause disease regardless of route of entry, but HVEM must be present for HSV-1 to cause full pathogenesis in the eye. These findings uncover a unique role for HVEM in mediating HSV-1 infection in an area innervated by the trigeminal ganglion and may explain why the presence of HVEM can lead to severe inflammation in the cornea. Thus, the dependence on HVEM is a dividing point between HSV-1 and HSV-2 that evolved to infect areas innervated by different sensory ganglia.

[Construction of the HSV-1 strain HF amplicon and study on its unversal function between different HSV serotypes]

The study aimed to construct the amplicon vector of HSV-1 strain HF and explore its universal package function between different serotypes of HSV. OriS and pac elements were obtained by enzyme digestion from the Plasmid BAC-HSV-1 strain HF and sequenced. With red fluorescence (DsRed) as a reporter gene, the amplicon vector of HSV-1 strain HF was constructed based on pSilencer2.0-U6. The amplicon vector was transfected into Vero cells by lipofectamine 2000, then packaged by HSV-1 strain HF and HSV-2 strain HG52 as helper virus separately. The supernatant was collected after cytopathic effect. Red fluorescence was observed in Vero cells reinfected by the supernatant. In this study,the amplicon vector of HSV-1 strain HF was successfully constructed and it could be packaged by HSV-1 strain HF and HSV-2 strainHG52.

Characterization of herpes simplex virus clinical isolate Y3369 as a glycoprotein G variant and its bearing on virus typing

BACKGROUND

Herpes simplex viruses exist as two major serotypes, type 1 (HSV-1) and type 2 (HSV-2). Determination of type, either HSV-1 or HSV-2, is important in accurate diagnosis and clinical control of transmission. Several tests are available for typing HSV, including a monoclonal antibody specific for glycoprotein G and several PCR assays.

FINDINGS

A clinical isolate was identified as herpes simplex virus, but tested negative for both HSV-1 and HSV-2 antigens using type-specific monoclonal antibody assays. The isolate was determined to be HSV-1 by PCR analysis. A mutation which likely caused the monoclonal antibody non-reactivity was found in glycoprotein G. Phylogenetic analysis revealed two groups of HSV, one with the mutation and one without. Three population studies examining mutations in HSV-1 glycoprotein G were analyzed by chi-squared test. To this point, the epitope which the monoclonal antibody recognizes was only found in HSV-1 isolates from human European populations (p < 0.0001).

CONCLUSIONS

These findings suggest that the PCR-based methods for HSV typing may be more useful than the standard monoclonal antibody test in areas of the world where the variant in glycoprotein G is more prevalent.

Emergence of herpes simplex virus-1 syncytial variants with altered virulence for mice after selection with a natural carrageenan

BACKGROUND

Antiviral therapy against herpes simplex virus based on sulfated polysaccharides, like carrageenans, represents a new alternative for genital herpes infections treatment and arises the concern about the appearance of resistant viral populations.

METHODS

We characterized the F strain of herpes simplex virus-1 passaged in the presence of a natural carrageenan isolated from the red seaweed Gigartina skottbergii in view of the virulence for mice of isolated viral clones.

RESULTS

Viral clones (syn14-1 and syn17-2) showed a syncytial phenotype and a mild resistance to carrageenan, heparin, acyclovir, and brivudine. Both clones were avirulent for BALB/c mice when inoculated intravaginally, whereas F strain produced high mortality. Attenuation correlated with low levels of TNF-[alpha], interleukin-6, and IFN-[gamma] in vaginal lavages although virus titers were similar to those obtained for F strain. On the contrary, they showed a marked virulence when inoculated intranasally leading to a generalized spreading of virus.

CONCLUSIONS

Results confirm the hypothesis that selection of herpes simplex virus-1 with a carrageenan in vitro leads to the emergence of variants with a differential virulence when compared to the original virus. This finding should be addressed when an antiviral therapy against genital herpes infection employing a natural carrageenan is under consideration.

The UL31 to UL35 gene sequences of Duck enteritis virus correspond to their homologs in herpes simplex virus 1

Five ORFs in the genome of Duck enteritis virus (DEV) corresponding to UL31, UL32, UL33, UL34, and UL35 genes of Herpes simplex virus 1 (HSV-1) were amplified by a modified "targeted gene walking" PCR, cloned, and sequenced. UL33, UL34, and UL35 genes were oriented from the left to the right of genome, while UL31 and UL32 had an opposite orientation. A comparison of deduced amino acid sequences of the DEV ORFs with their alphaherpesvirus homologs showed well-conserved regions except for the UL34 and UL35 genes. Phylogenetic analysis revealed that DEV was closer to the genus Mardivirus than to any other genus of the subfamily Alphaherpesvirinae. Based on this evidence, we proposed to assign DEV to the subfamily Alphaherpesvirinae.

Unlabeled probes for the detection and typing of herpes simplex virus

BACKGROUND

Unlabeled probe detection with a double-stranded DNA (dsDNA) binding dye is one method to detect and confirm target amplification after PCR. Unlabeled probes and amplicon melting have been used to detect small deletions and single-nucleotide polymorphisms in assays where template is in abundance. Unlabeled probes have not been applied to low-level target detection, however.

METHODS

Herpes simplex virus (HSV) was chosen as a model to compare the unlabeled probe method to an in-house reference assay using dual-labeled, minor groove binding probes. A saturating dsDNA dye (LCGreen Plus) was used for real-time PCR. HSV-1, HSV-2, and an internal control were differentiated by PCR amplicon and unlabeled probe melting analysis after PCR.

RESULTS

The unlabeled probe technique displayed 98% concordance with the reference assay for the detection of HSV from a variety of archived clinical samples (n = 182). HSV typing using unlabeled probes was 99% concordant (n = 104) to sequenced clinical samples and allowed for the detection of sequence polymorphisms in the amplicon and under the probe.

CONCLUSIONS

Unlabeled probes and amplicon melting can be used to detect and genotype as few as 10 copies of target per reaction, restricted only by stochastic limitations. The use of unlabeled probes provides an attractive alternative to conventional fluorescence-labeled, probe-based assays for genotyping and detection of HSV and might be useful for other low-copy targets where typing is informative.

Detection of differences in genomic profiles between herpes simplex virus type 1 isolates sequentially separated from the saliva of the same individual

BACKGROUND

Herpes simplex virus (HSV) is assumed to cause recrudescent lesions, usually through endogenous recurrence and rarely through exogenous re-infection. The occurrence of exogenous re-infection in genital and corneal HSV infections has been previously demonstrated using genomic analysis, while exogenous re-infection in oral-facial HSV infections has not been shown.

OBJECTIVES

To confirm the occurrence of exogenous HSV re-infection in oral-facial HSV infections.

STUDY DESIGN

Seven isolates (isolates 1-7) of herpes simplex virus type 1 (HSV-1) were sequentially separated from the same individual. Genomic profiles of HSV-1 isolates were studied: (i) by analysis of 20 RFLPs (restriction fragment length polymorphisms) and (ii) by the determination of nucleotide sequences of a PCR-amplified DNA fragment encompassing reiteration VII (hypervariable region) that belongs to sequences containing short tandem repeats.

RESULTS

Isolates 1-5 were the same (F83 genotype) and isolates 6 and 7 were the same (F84 genotype), although isolates 1-5 were markedly different from isolates 6 and 7 in genomic profiles.

CONCLUSIONS

The infection associated with isolates 6 and 7 was due to exogenous re-infection with F84 genotype virus, thus indicating the occurrence of exogenous HSV re-infection in oral-facial HSV infections.

Discriminant analysis of DNA polymorphisms in herpes simplex virus type 1 strains involved in primary compared to recurrent infections

The restriction fragment length polymorphism (RFLP) was analyzed using a set of herpes simplex virus type 1 (HSV-1) strains isolated from oro-facial lesions (oro-facial site collection), which was composed of two subsets: one subset consisted of 57 strains from primary oro-facial lesions, and the other of 47 strains from recurrent oro-facial lesions of patients complicated by factors possibly triggering the recurrence (e.g. malignancy, operation, and treatment of dental caries). RFLP analysis was carried out previously on two other sets of HSV-1 strains: one set was from genital lesions (genital site collection), and the other was from non-genital lesions (non-genital site collection). Discriminant analysis was carried out on the three sets of HSV-1 strains: the criterion variable had two values of primary infection or recurrence, and the predictor variables were 20 RFLPs. The degrees of separation between primary infection and recurrence increased in the order oro-facial site collection, genital site collection, and non-genital site collection. The results of discriminant analysis in this study confirmed that reactivation of HSV-1 infection is influenced by triggering factors and the site of infection, thereby suggesting the capabilities of multivariate analysis (including discriminant analysis) with DNA polymorphisms for molecular epidemiological studies.

Contrasting geographic distribution profiles of the herpes simplex virus type 1 BgOL and BgKL variants in Japan suggest dispersion and replacement

Thelifelong latent infection-reactivation mode of infection of herpes simplex virus type 1 (HSV-1) transmitted by close contact has allowed a diversity of restriction fragment length polymorphism (RFLP) variations to accumulate in human populations. Whether and how the variants of the HSV-1 that is ubiquitous worldwide spread to different human populations is not clear. In our previous study the geographically gradient distribution of the HSV-1 BgK(L) variant, which is a good marker for the BgK(L):SaCFJ(M):SaGH(M):SaD/E(L):KpM(S) variant, suggested that BgK(L) dispersed geographically. Southern hybridization analyses showed that in BgK(L) the BglII cleavage site between the BglII K and small "Q/#13" fragments is lost, the SalI cleavage sites between the SalI J and C and between SalI F and J fragments are lost, and the SalI E fragment is abnormally large (SaE(L) variation). The RFLP and geographic distribution of one more HSV-1 RFLP variant, BgO(L), were comparatively analyzed. The BglII cleavage site between the BglII O and Q/#13 fragments is lost in BgOL. BgO(L) clinical isolates were not associated with any of the SaCFJ(M), SaE(L), SaGH(M), or KpM(S) variations, whereas one-fourth of the non-BgO(L):non-BgK(L) isolates was associated with SaCFJ(M) and SaGH(M), indicating that BgK(L) and BgO(L) are distant in terms of diversification. BgO(L) is distributed highly in the northeastern region and the southwestern island of Kyushu but is rare between the two regions in Japan, in a remarkable contrast to BgK(L). These are the first epidemiologic data to show contrasting geographic distribution profiles of two HSV-1 variants and suggest the gradual dispersion and replacement of HSV-1 variants.

Invader plus method detects herpes simplex virus in cerebrospinal fluid and simultaneously differentiates types 1 and 2

We report here on the development and validation of a prototype Invader Plus method for the qualitative detection of herpes simplex virus types 1 and 2 in cerebrospinal fluid (CSF). The method combines PCR and Invader techniques in a single, closed-tube, continuous-reaction format that gives an analytical sensitivity of approximately 10 copies per reaction. The clinical sensitivity and specificity were 100.0% and 98.6%, respectively, when the results of the method were validated against the results obtained with a PCR colorimetric microtiter plate system by use of clinical CSF specimens.

Genotyping of clinical herpes simplex virus type 1 isolates by use of restriction enzymes

Recently, three distinct genotypes of clinical herpes simplex virus type 1 (HSV-1) isolates were identified based on DNA sequence information and phylogenetic analysis of clinical isolates and laboratory strains. We utilized single-nucleotide polymorphism within the genes coding for glycoproteins G and I for rapid genotype classification by PCR and restriction enzyme cleavage. The method is suitable for high-scale genotyping of clinical HSV-1 isolates and for the detection of recombinants.

Evidence that the immediate-early gene product ICP4 is necessary for the genome of the herpes simplex virus type 1 ICP4 deletion mutant strain d120 to circularize in infected cells

Following infection, the physical state of linear herpes simplex virus (HSV) genomes may change into an "endless" or circular form. In this study, using Southern blot analysis of the HSV genome, we provide evidence that immediate-early protein ICP4 is involved in the process of converting the linear HSV-1 ICP4-deleted mutant strain d120 genome into its endless form. Under conditions where de novo viral DNA synthesis was inhibited, the genome of the ICP4 deletion mutant d120 failed to assume an endless conformation following infection of Vero cells (compared with the ability of wild-type strain KOS). This defect was reversed in the Vero-derived cell line E5, which produces the ICP4 protein, suggesting that ICP4 is necessary and sufficient to complement the d120 defect. When ICP4 protein was provided by the replication-defective DNA polymerase mutant HP66, the genomes of mutant d120 could assume an endless conformation in Vero cells. Western blot analysis using antibody specific to the ICP4 protein showed that although the d120 virions contained ICP4 protein, the majority of that ICP4 protein was in a 40-kDa truncated form, with only a small fraction present as a full-length 175-kDa protein. When expression of ICP4 protein from E5 cells was inhibited by cycloheximide, the d120 virion-associated ICP4 protein was unable to mediate endless formation after infection of E5 cells. Collectively, these data suggest that ICP4 protein has an important role in mediating the endless formation of the HSV-1 genome upon infection and that this function can be provided in trans.

Geographical distribution of the herpes simplex virus type 1 BgKL variant in Japan suggests gradual dispersion of the virus from Shikoku Island to the other Islands

Restriction endonuclease fragment length polymorphism (RFLP) is useful for the epidemiological study of herpes simplex virus type 1 (HSV-1). We report here the identification of a major BglII RFLP variant of HSV-1, designated BgKL, found in 27.0% of 636 HSV-1 clinical isolates. We have also established its geographic distribution in Japan. BgKL has an unusually large BglII K fragment. SalI cleavage analyses showed that 97% of BgKL variant isolates lack both the SalI C-J and the F-J cleavage sites and have an unusually large SalI D or E fragment, and 91% of the BgKL variants lack both SalI G and H fragments. Furthermore, 96% of BgKL isolates have an unusually small KpnI M fragment. Therefore, BgKL is a marker for these five mutations in most HSV-1 isolates and is a useful HSV-1 RFLP marker. The BgKL variant was found in 59% of HSV-1 isolates from Shikoku Island, 44% of HSV-1 isolates from the Chugoku region of Honshu Island, 31% of HSV-1 isolates from Kyushu Island, 0% of HSV-1 isolates from Okinawa Island, 49% of HSV-1 isolates from Osaka, 27% of HSV-1 isolates from Shiga, 13% of HSV-1 isolates from the Chubu Region, and 9% of HSV-1 isolates from the Tohoku Region of Honshu Island. Differences in the frequency of BgKL between the Shikoku-Chugoku-Osaka area (49%) and Kyushu, between Kyushu and Okinawa, between the Shikoku-Chugoku-Osaka area and Shiga, and between Shiga and Tohoku are all statistically significant. The BgKL frequency decreases in a geographical gradient suggest that this HSV-1 variant was dispersed from Shikoku to the surrounding regions and then to more distant regions. The BgKL frequency in Tokyo was similar to the nationwide average. These are the first data to suggest a geographic and demographic dispersion pattern of HSV-1. Implications for the epidemiology and diversification of HSV-1 are discussed.

Evaluation of the Cepheid herpes simplex virus typing real-time PCR assay using dermal and genital specimens

The Cepheid herpes simplex virus (HSV) (Cepheid, Sunnyvale, CA) typing multiplex real-time polymerase chain reaction (PCR) assay was evaluated for its ability to detect HSV in dermal and genital specimens stored in M5 media. Swab specimens (n = 114) for HSV testing were placed in M5 media and split between our laboratory and a highly experienced reference laboratory. Aliquots for testing with the Cepheid assay were processed using a simple boil-and-go procedure and then run in a SmartCycler II (Cepheid). Aliquots tested at the reference laboratory were processed using a MagNA Pure LC DNA extractor (Roche Molecular Systems, Alameda, CA) and tested by the Roche HSV real-time PCR assay. Both laboratories detected 35 positives. Of the positive specimens, the Cepheid assay typed 16 as HSV 1 and 19 as HSV 2; the reference laboratory typed 15 as HSV 1, 19 as HSV 2, and 1 as HSV indeterminate. Our results demonstrate that the Cepheid real-time PCR assay, using specimens subjected to minimal specimen processing, performed as well as the Roche real-time PCR assay, using DNA extracts, for the detection of HSV DNA in genital and dermal specimens.

Differentiation of herpes simplex virus types 1 and 2 in clinical samples by a real-time taqman PCR assay

While the clinical manifestations of HSV-1 and -2 overlap, the site of CNS infection, complications, response to antivirals, frequency of antiviral resistance, and reactivation rate on mucosal surfaces varies between HSV-1 and -2. Detection of HSV DNA by PCR has been shown to be the most sensitive method for detecting HSV in clinical samples. As such, we developed a PCR-based assay to accurately distinguish HSV-1 from HSV-2. Our initial studies indicated the assay using type specific primers was slightly less efficient for detecting HSV-1 and -2 DNA than the high throughput quantitative PCR assay we utilize that employs type common primers to gB. We subsequently evaluated the type specific assay on 3,131 specimens that had HSV DNA detected in the type common PCR assay. The typing results of these specimens were compared with the monoclonal antibody staining results of culture isolates collected from the same patients at the same time, and the HSV serologic status of the patient. The typing assay accurately identified both HSV-1 and -2 with a specificity of >99.5% and was significantly more sensitive than typing by culture and subsequent monoclonal antibody assays. Complete concordance was seen between the typing assay and HSV serologic status of the patient. Dual (HSV-1 and -2) infection in clinical samples was recognized in 2.6% of clinical samples using the new typing assay. This assay, when used in combination with the type common assay, can now accurately type almost all mucosal and visceral HSV isolates by molecular techniques.

Sensitive and rapid detection of herpes simplex virus and varicella-zoster virus DNA by loop-mediated isothermal amplification

Loop-mediated isothermal amplification (LAMP) is a novel nucleic acid amplification method in which reagents react rapidly and efficiently, with a high specificity, under isothermal conditions. We used a LAMP assay for the detection of herpes simplex virus type 1 (HSV-1), herpes simplex virus type 2 (HSV-2), and varicella-zoster virus (VZV). The virus specificities of primers were confirmed by using 50 HSV-1, 50 HSV-2, and 8 VZV strains. The assay was performed for 45 min at 65 degrees C. The LAMP assay had a 10-fold higher sensitivity than a PCR assay. An analysis of nucleotide sequence variations in the target and primer regions used for the LAMP assay indicated that 3 of 50 HSV-1 strains had single nucleotide polymorphisms. No HSV-2 or VZV strains had nucleotide polymorphisms. Regardless of the sequence variation, there were no differences in sensitivity with the HSV-1-specific LAMP assay. To evaluate the application of the LAMP assay for clinical diagnosis, we tested clinical samples from 40 genital herpes patients and 20 ocular herpes patients. With the LAMP assay, 41 samples with DNA extraction and 26 direct samples without DNA extraction were identified as positive for HSV-1 or HSV-2, although 37 samples with DNA extraction and just one without DNA extraction were positive by a PCR assay. Thus, the LAMP assay was less influenced than the PCR assay by the presence of inhibitory substances in clinical samples. These observations indicate that the LAMP assay is very useful for the diagnosis of HSV-1, HSV-2, and VZV infections.

Detection and typing of Herpes Simplex virus (HSV) in mucocutaneous samples by TaqMan PCR targeting a gB segment homologous for HSV types 1 and 2

Herpes simplex virus types 1 (HSV-1) and 2 (HSV-2) are major causes of mucocutaneous lesions and severe infections of the central nervous system. Here a new semiautomated method for detecting and typing of HSV was used to analyze 479 mucocutaneous swab samples. After DNA extraction using a Magnapure LC robot, a 118-bp segment of the gB region was amplified by real-time PCR utilizing type-specific TaqMan probes to identify HSV-1 or HSV-2. HSV detection in a single well using probes labeled with carboxyfluorescein (FAM) for HSV-1 and JOE (6-carboxy-4',5'-dichloro-2',7'-dimethoxyfluorescein) for HSV-2 had a sensitivity similar to that seen in separate reactions. All but one of 217 samples (99.5%) that had been positive by virus culture were positive by TaqMan PCR, with a correct identification of type in all cases. Out of 262 samples negative by virus culture, 48 (18.3%) were positive by TaqMan PCR, with higher Ct values compared with culture positive samples (P < 0.0001). Overall, the Ct values for HSV-1 were lower than for HSV-2 (mean, 25.5 versus 27.9), but to some extent this could be due to weaker fluorescence by JOE. Lower C(t) values for HSV-1 were seen also in the 202 genital samples (79 HSV-1, 122 HSV-2, 1 HSV-1 and HSV-2), indicating that HSV-1 replicates as well as HSV-2 in the genital area. HSV-1 constituted 40% of genital infections and was associated with lower mean age (29.2 versus 36.4 years), probably reflecting the fact that recurrent genital HSV-1 infections are rare.

Comparison of two methods of PCR followed by enzymatic restriction digestion for detection and typing of herpes simplex viruses isolated from patients with mucocutaneous or cutaneous lesions

A multitude of different polymerase chain reactions (PCRs) have been described for detection and typing of Herpes simplex virus (HSV). This paper compares two PCRs coupled to enzymatic restriction (PCR/RFLP) to detect and type HSV. A primers set was designed to amplify a HSV DNA fragment from UL30 and UL 15 genes. Typing was done by restriction of the UL30 and UL15 amplicons with Ava II and Hpa II enzymes, respectively. This strategy was tested with two reference strains (HSV-1 McIntyre, and HSV-2 G), and 47 clinical HSV isolates. Both PCRs produced the expected amplicons (a 492 bp UL30, and 305 bp UL15). The restriction of both amplicons clearly differentiated HSV- from HSV-2, and produced equal results. Thirty one (66%) of the isolates were identified as HSV-1, and the other 16 (34%), as HSV-2. Most of the HSV-1 isolates (27/31) were from orofacial and thoracic lesions; and also, one half of the HSV-2 isolates (8/16) were from the same anatomical regions. Our results showed that either of the two PCR/RFLP could be used to detect and type HSV. Furthermore, our results of the anatomical site of HSV-1 and HSV-2 infections are consistent with previous reports which have shown changes in the classical anatomical localization of herpesvirus infections.

Characterization of virus isolates by particle-associated nucleic acid PCR

Diagnostic virus isolation is still frequently used, particularly from respiratory tract secretions. Testing positive virus cultures for all possible viruses is time-consuming, and unexpected or unknown viruses may escape detection. Therefore, a novel random PCR approach was developed that allows sequence-independent amplification of viral nucleic acids from virus isolation-positive cultures. Selectivity for viral sequences is obtained by preferential isolation of nucleic acids that are particle associated and resistant to nucleases. Using primers with a degenerated 3' end, the isolated nucleic acids are amplified and the randomly amplified PCR products are cloned and sequenced. As proof of the concept, the PAN-PCR approach was applied to supernatants of coxsackievirus B3 and murine adenovirus type 1-infected cells. Enterovirus and adenovirus sequences were obtained, demonstrating that the random PCR approach allows detection of RNA and DNA viruses. As a first application of this PAN-PCR approach, we characterized a virus isolate from mouth-washing material of a patient with chronic fatigue syndrome and high antibody titers to coxsackievirus B2. The virus isolate had tested negative for enteroviruses and respiratory viruses (influenza viruses A and B, parainfluenza virus types 1 to 3, respiratory syncytial virus, and adenovirus) by immunofluorescence and PCR. Particle-associated, nuclease-resistant RNA and DNA were prepared from the supernatant of infected cells. The DNA and the reverse-transcribed RNA were randomly amplified, and PCR products were cloned and sequenced. Of 25 sequences obtained from the DNA preparation, 24 contained herpes simplex virus type 1 (HSV-1) sequences from 14 different loci spread over the HSV-1 genome. This result was confirmed by using a standard diagnostic HSV-PCR, demonstrating that the PAN-PCR correctly identified the virus isolate. Although the identification of HSV-1 in mouth-washing material is not surprising in retrospect, it clearly demonstrates the applicability of the PAN-PCR approach. This method should be particularly useful for characterizing virus isolates that have tested negative for all expected viruses and for identifying unknown viruses.

Sequencing and resolution of amplified herpes simplex virus DNA with intermediate melting curves as genotype 1 or 2 by LightCycler PCR assay

DNA from 101 specimens containing herpes simplex virus (HSV) produced atypical intermediate melting curves compared with those expected for HSV type 1 or HSV type 2 subsequent to real-time PCR. Nucleic acid sequence analysis of amplified target DNA revealed 1- or 3-bp polymorphisms in the probe region which allowed designation of these viruses as HSV genotype 1 or HSV genotype 2. These two subpopulations of HSV were also identified as HSV genotype 1 or HSV genotype 2 using another commercially available PCR method. Amplified HSV target DNA producing intermediate melting curves could be designated as HSV genotype 1 or HSV genotype 2 without performing sequencing or another PCR method with 96/101 (95%) specimens by adding known intermediate HSV DNA characteristic for the two subpopulations as controls.

Growth of herpes simplex virus in epidermal keratinocytes determines cutaneous pathogenicity in mice

Herpes simplex viruses (HSV)-1 and -2 isolated from genital lesions were examined for cutaneous pathogenicity and its correlation with cellular tropism. HSV-1 caused vesiculation, erosion/ulcer, and zosteriform lesions successively, but skin lesions of HSV-2 developed without vesiculation in some mice, and with statistically significantly less frequent vesiculation than HSV-1. Thus, the virological type of HSV was correlated with its cutaneous pathogenicity. The growth characteristics of HSV-1 and -2 were compared in cultured human embryonic lung (HEL) fibroblasts, human lung cancer A549 cells, human neonatal epidermal keratinocytes, human neonatal dermal fibroblasts, HeLa cells, and Vero cells. HSV-2 produced plaques that were 72% times the size of HSV-1 plaques in epidermal keratinocytes but 230%-500% the size in the other cells. The difference between HSV-1 and -2 in the ratio of plaque size to virus yield in epidermal keratinocytes was much larger (502 times) than the ratio of the other cells (5.57-28.8 times). Keratinocytes are the major constituent of the epidermal layer of the skin and the cells in which vesiculation and erosion/ulceration occur histologically. Therefore, the smaller spread of HSV-2 in keratinocytes of the epidermal layer and the greater spread in other cells of the dermal layer might reflect its lesser invasiveness in the epidermal layer despite larger invasiveness in the dermal layer, which is reflected in the low incidence of erosion/ulcer of the skin compared to HSV-1. Thus, the growth of HSV in epidermal keratinocytes appeared to correlate with the cutaneous pathogenicity causing vesiculation in the skin.

Phylogenetic analysis of clinical herpes simplex virus type 1 isolates identified three genetic groups and recombinant viruses

Herpes simplex virus type 1 (HSV-1) is a ubiquitous human pathogen which establishes lifelong infections. In the present study, we determined the sequence diversity of the complete genes coding for glycoproteins G (gG), I (gI), and E (gE), comprising 2.3% of the HSV-1 genome and located within the unique short (US) region, for 28 clinical HSV-1 isolates inducing oral lesions, genital lesions, or encephalitis. Laboratory strains F and KOS321 were sequenced in parallel. Phylogenetic analysis, including analysis of laboratory strain 17 (GenBank), revealed that the sequences were separated into three genetic groups. The identification of different genogroups facilitated the detection of recombinant viruses by using specific nucleotide substitutions as recombination markers. Seven of the isolates and strain 17 displayed sequences consistent with intergenic recombination, and at least four isolates were intragenic recombinants. The observed frequency of recombination based on an analysis of a short stretch of the US region suggests that most full-length HSV-1 genomes consist of a mosaic of segments from different genetic groups. Polymorphic tandem repeat regions, consisting of two to eight blocks of 21 nucleotides in the gI gene and seven to eight repeats of 3 nucleotides in the gG gene, were also detected. Laboratory strain KOS321 displayed a frameshift mutation in the gI gene with a subsequent alteration of the deduced intracellular portion of the protein. The presence of polymorphic tandem repeat regions and the different genogroup identities can be used for molecular epidemiology studies and for further detection of recombination in the HSV-1 genome.

Evaluation of the ELVIS plate method for the detection and typing of herpes simplex virus in clinical specimens

This study was conducted to assess the reliability of a commercial enzyme-linked viral inducible system (ELVIS) (Diagnostic Hybrids, Inc., Athens, OH) for rapid detection and typing of herpes simplex virus (HSV). Results using ELVIS were compared to those of shell vial culture (SVC) and HSV detection with monoclonal antibodies and an immunoperoxidase stain plus typing with MicroTrak direct fluorescent antibodies (Trinity Biotech PLC, Wicklow, Ireland). Specimens yielding discrepant HSV results were tested by polymerase chain reaction (PCR); those with discrepant typing results were stained with Simulfluor (Chemicon, Temecula, CA). Of the 206 samples tested, 144 were negative and 54 were HSV-positive by both methods (agreement, 96.1%). Five specimens were positive by ELVIS but negative by SVC; 3 of these were positive and 2 were negative by HSV PCR. Both of the latter were the result of mechanical problems early in the study. Three specimens were positive by SVC but negative by ELVIS; all 3 were positive by HSV PCR. After resolution of discrepancies, the sensitivity and specificity for detection of HSV were 95.0% and 100% for SVC, respectively, and 95.0% and 98.6% for ELVIS. Of the 46 HSV-positive samples that were typed, 26 were called type 2 and 18 were type 1 by both methods (agreement, 95.7%). The 2 specimens with discrepant results were called HSV-2 by SVC, staining with MicroTrak, and HSV-1 with ELVIS; both of these were type 2 when stained with the Simulfluor reagent. ELVIS is a reliable alternative to SVC for rapid detection and typing of HSV.

Neuropeptides (SP and CGRP) augment pro-inflammatory cytokine production in HSV-infected macrophages

Neuropeptides are able to modulate cytokine production by macrophages in response to various stimulators. In this study, the effects of neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP) on production of pro-inflammatory cytokines TNF and IL-1 beta by macrophages were considered. Mouse peritoneal macrophages were infected with herpes simplex virus type-1 (HSV-1), or remained unstimulated, and cytokine assays were performed after 12 h. IL-1 beta and TNF secretion by unstimulated macrophages have been significantly increased in the presence of SP and CGRP. Each neuropeptide, alone or in coordination with the other, caused significant increase in IL-1 beta and TNF production by HSV-infected mouse peritoneal macrophages. It was concluded that the macrophage-mediated inflammatory response to HSV-1 is enhanced in the presence of these neuropeptides.

Detection and differentiation of herpes simplex virus types 1 and 2 by a duplex LightCycler PCR that incorporates an internal control PCR reaction

BACKGROUND

In recent years polymerase chain reaction (PCR) has proven to be a highly sensitive and specific method for the diagnosis of herpes simplex virus (HSV) infections. The advent of real-time HSV PCR protocols now enables rapid result turnaround times with minimal hands-on time.

OBJECTIVES

In this study, we developed a real-time duplex PCR assay (HSVgD-dPCR) comprising of HSV and internal control PCR reactions.

STUDY DESIGN

Using the LightCycler, the HSVgD-dPCR targeted the HSV glycoprotein D gene and HSV typing was performed by melting curve analysis. The internal control PCR reaction targeted sequences of the DNA of the human endogenous retrovirus (ERV-3). In total, 300 swab specimens, from patients with suspected HSV infection, were tested by the HSVgD-dPCR assay. The results were then compared to the results obtained by another HSV LightCycler assay, which utilized published primer and probe sequences targeting the HSV DNA polymerase gene (Dpol-HSV-LCPCR).

RESULTS

Overall, 91 (30.3%) specimens were positive and 204 (68.0%) specimens were negative for HSV by both LightCycler assays. In addition, four (1.3%) specimens were positive by Dpol-HSV-LCPCR and negative by HSVgD-dPCR, whereas one (0.3%) specimen was positive by HSVgD-dPCR and negative by Dpol-HSV-LCPCR. The presence of HSV in these five specimens was confirmed by conventional PCR. Melting curve analysis by the HSVgD-dPCR assay enabled all HSV positive specimens to be typed, whereas sequence variation prevented three HSV positive specimens from being typed by the Dpol-HSV-LCPCR. Using the ERV-3 PCR, 5% specimens were found to contain inhibitory substances.

CONCLUSIONS

By developing the HSVgD-dPCR we have enhanced the diagnostic utility of real-time detection of HSV by incorporating an internal control reaction and by accurately typing a greater proportion of HSV positive specimens.

Herpes simplex virus genotyping: multiple optional PCR-based RFLP systems and a non-isotopic single-strand conformation polymorphism method

Polymerase chain reaction (PCR)-based methods for herpes simplex virus (HSV) types I/II genotyping are described. These methods are based on the single-stranded conformation properties of DNA molecules obtained by PCR (PCR-SSCP) and restriction fragment analysis of PCR products (PCR-RFLP). With the aim to analyse these two genotyping techniques, genomic DNA from the standard viral strains KOS and G, and also 79 normal cervical samples were studied for HSV I/II. Sequence analysis showed 19 different RFLP possible systems for HSV typing. Five systems were used in this study and all led to the expected fragments obtained by sequence analysis. PCR-SSCP showed distinct patterns for both viral types and had 100% of concordance with PCR-RFLP results. The prevalence of herpes simplex virus in the normal cervical samples were 21.5% (17 out of 79), the most frequent viral type was HSV-2, with a prevalence of 71% (12 out of 17). Both techniques appeared suitable for HSV I/II genotyping and are easy to perform in most clinical laboratories.

Detection of herpes simplex virus type 1, herpes simplex virus type 2 and varicella-zoster virus in skin lesions. Comparison of real-time PCR, nested PCR and virus isolation

BACKGROUND

Herpes simplex virus type 1 (HSV-1), herpes simplex virus type 2 (HSV-2) and varicella-zoster virus (VZV) cause a wide range of signs and symptoms, varying from trivial mucocutaneous lesions to life-threatening infections, especially in immuno-suppressed patients. Since antiviral drugs are available, rapid and sensitive laboratory diagnosis of these virus infections is important.

OBJECTIVE

To set up and evaluate HSV-1, HSV-2 and VZV qualitative real-time PCR on the Lightcycler system and to compare the results with those of the 'in-house' nested PCR and virus isolation.

STUDY DESIGN

110 consecutive samples from dermal or genital lesions from patients suspected of having HSV infections and another 110 samples from patients with suspected VZV infections were tested with real-time PCR, nested PCR and virus isolation.

RESULTS

24 samples (22%) were positive for HSV-1 by virus isolation and nested PCR, whereas 26 (24%) were positive by real-time PCR. HSV-2 was detected in 28 samples (25%) by virus isolation, in 41 (37%) by nested PCR and in 40 (36%) by real-time PCR. VZV was isolated in 15 samples (14%) and VZV DNA was detected in 51 samples (46%) by nested PCR as well as by real-time PCR. Nucleic acid amplification increased the detection rate of HSV-2 and VZV DNA in particular compared to virus isolation. No significant difference in sensitivity was found between real-time PCR and nested PCR.

CONCLUSION

Real-time PCR has the advantage of rapid amplification, a reduced risk for contamination and it is a suitable method for diagnosis of VZV and HSV in specimens from skin lesions.

Phenotype of a herpes simplex virus type 1 mutant that fails to express immediate-early regulatory protein ICP0

Herpes simplex virus type 1 (HSV-1) immediate-early (IE) regulatory protein ICP0 is required for efficient progression of infected cells into productive lytic infection, especially in low-multiplicity infections of limited-passage human fibroblasts. We have used single-cell-based assays that allow detailed analysis of the ICP0-null phenotype in low-multiplicity infections of restrictive cell types. The major conclusions are as follows: (i) there is a threshold input multiplicity above which the mutant virus replicates normally; (ii) individual cells infected below the threshold multiplicity have a high probability of establishing a nonproductive infection; (iii) such nonproductively infected cells have a high probability of expressing IE products at 6 h postinfection; (iv) even at 24 h postinfection, IE protein-positive nonproductively infected human fibroblast cells exceed the number of cells that lead to plaque formation by up to 2 orders of magnitude; (v) expression of individual IE proteins in a proportion of the nonproductively infected cells is incompletely coordinated; (vi) the nonproductive cells can also express early gene products at low frequencies and in a stochastic manner; and (vii) significant numbers of human fibroblast cells infected at low multiplicity by an ICP0-deficient virus are lost through cell death. We propose that in the absence of ICP0 expression, HSV-1 infected human fibroblasts can undergo a great variety of fates, including quiescence, stalled infection at a variety of different stages, cell death, and, for a minor population, initiation of formation of a plaque.

Genotypic analysis of sequential genital herpes simplex virus type 1 (HSV-1) isolates of patients with recurrent HSV-1 associated genital herpes

Clinical recurrences of Herpes simplex virus type 1 (HSV-1)-associated genital herpes are thought to be caused by reactivation of latent endogenous HSV-1. However, the possibility of reinfection with exogenous HSV-1 cannot be excluded. This study aimed to determine the incidence of genital HSV-1 superinfection in patients by investigating the genotype of sequential HSV-1 isolates obtained from the same anatomical site of patients with clinical recurrences of genital HSV-1 recurrent genital herpes. Sequential genital HSV-1 isolates were genotyped by PCR amplification of the hypervariable regions located within the HSV-1 genes US1 and US12. Whereas the sequential HSV-1 isolates in 11 of the 13 patients studied had the same genotypes, the sequential isolates of 2 patients showed a different genotype. The data suggest that HSV-1-induced recurrent genital herpes can be associated with genital reinfection with an exogenous HSV-1 strain.

Detection and typing of HSV-1, HSV-2, CMV and EBV by quadruplex PCR

The development of a multiplex polymerase chain reaction (PCR) method for rapid and accurate detection and typing of herpes simplex virus type 1 (HSV-1), and type-2 (HSV-2), cytomegalovirus (CMV) and Epstein-Barr virus (EBV) is very important for clinical diagnosis to allow the deliver of therapy as early as possible. Large scale amplifications by multiplex PCR of viral DNA can lower the cost and time for viral diagnosis. In this study, therefore sensitive quadruplex PCR was achieved by optimizing parameters such as primers, and 1.5 mM magnesium and 200 uM dNTPs concentrations. The concentrations of HSV-1, HSV-2, CMV and EBV primers were 0.5, 0.3, 0.25 and 0.25 pmoles, respectively. Optimal annealing temperature was 54 degrees C. Employing these conditions, we could detect 10 copies of reconstructed template plasmid DNA, which were cloned to vectors containing target sequences of viral DNA. PCR products of 271 bp for HSV-1, 231 bp for HSV-2, 368 bp for CMV, and 326 bp for EBV were separated on 5.0% polyacrylamide gel electrophoresis and confirmed by direct sequencing. The present study showed that the quadruplex PCR assay described herein has potential application in clinical diagnosis, when rapid, accurate detection and typing of viruses HSV-1, HSV-2, CMV or EBV are necessary.

Detection and genotyping of human herpes simplex viruses in cutaneous lesions of erythema multiforme by nested PCR

A subset of erythema multiforme (erythema multiforme) is associated with herpes simplex virus (HSV) infection; viral cultures of erythema multiforme lesions are, however, usually negative and viral antigens difficult to identify. Polymerase chain reaction (PCR) has been used to demonstrate the association, hence, is currently the only available sensitive diagnostic means for HSV-associated erythema multiforme. A nested PCR, which could simultaneously detect and genotype HSV in erythema multiforme lesions and in clinical swab specimen was developed using the DNA polymerase gene of HSV as target gene because it is the only detectable HSV gene in a high proportion of erythema multiforme lesions. The PCR has demonstrated its robust sensitivity on swab samples by being able to detect further 45.3% HSV cases in comparison with virus isolation with 100% specificity in both detection and genotyping confirmed by virus isolation and DNA sequencing. This study represents the first investigation of typing HSV virus in HSV-associated erythema multiforme patients, and the finding that 66.7% of the patients was attributed to HSV1, 27.8% to HSV2, and 5.6% to HSV1 and 2 co-infection may reflect the distribution of HSV1 and 2 in local general population.

Genotyping of herpes simplex virus type 1 strains isolated from ocular materials of patients with herpetic keratitis

Herpes simplex virus type 1 (HSV-1) is the etiological agent of herpetic keratitis. The epithelial form ("epithelial keratitis") is attributed mainly to destruction of the epithelium through active viral replication within the epithelium. The stromal form ("stromal keratitis") is associated with immune reactions within the stroma and is the common cause of human blindness. In the present study, 29 HSV-1 strains isolated from human ocular materials of herpetic keratitis were classified into 14 genotypes on the basis of DNA polymorphisms. Twenty-one of 29 (72%) strains from eyes examined in the present study were of genotypes that were shown previously to be present in strains from non-ocular lesions (including genital herpes). Five of nine (56%) strains from eyes related to stromal keratitis were of the F1 genotype, while four of twenty (20%) strains from eyes not related to stromal keratitis were of the F1 genotype. Thus, the proportion of F1 genotype was assumed to be larger in the group of strains related to stromal keratitis than in that not so related, suggesting an association of the F1 genotype with stromal keratitis. A connection of F1 genotype with recurrence was proposed previously; hence, F1 genotype seems to be associated to both stromal keratitis and the recurrence, thereby supporting the relationship between stromal keratitis and recurrence.

Isolation of the enhanced neurovirulent HSV-1 strains from Korean patients

Herpes simplex virus type 1 (HSV-1) is a neurotropic DNA virus which has latency in human. In this study, we isolated various HSV-1 strains, named KHS, from the skin lesions of Korean patients and characterized the specific features of each strain. We found that KHS strains produced small, cell associated and nonsyncycial plaques in Vero cells. We classified KHS strains into two substrains, KHS 1 which had highly condensed plaques and KHS 2 which had less condensed plaques. Since gD protein of HSV-1 plays important roles in viral plaque formation, we determined the nucleotide sequences of gD genes of KHS strains. According to deduced amino acid sequences of gD protein in KHS strains compared with prototype strains KOS and F, we found that gD of KHS strains have more putative O-glycosidic sites, serine in KHS 1 and threonine in KHS 2, respectively. To find out the establishment of viral latency, we infected each virus strain into eyes of mice and carried out trigerminal ganglia explanting experiment. We found that both KHS strains established latent infections stably just as did the prototype KOS and F strains. The eye swab experiments were carried out to check the viral replication in vivo. KHS 1 exhibited a longer shedding time in eyes of mice. We also found that KHS 1 has a higher neurotropic affinity by determining the time it took for the virus to reach the trigerminal ganglia from the eyes. Currently, we are studying the possible mechanism of high neuroinvasiveness of KHS 1 strain.

Expression of a fusogenic membrane glycoprotein by an oncolytic herpes simplex virus potentiates the viral antitumor effect

Oncolytic viruses have shown considerable promise in the treatment of solid tumors, but their potency must be improved if their full clinical potential is to be realized. We inserted the gene encoding a truncated form of the gibbon ape leukemia virus envelope fusogenic membrane glycoprotein (GALV.fus) into an oncolytic herpes simplex virus, using an enforced ligation procedure. Subsequent in vitro and in vivo studies showed that expression of GALV.fus in the context of an oncolytic virus significantly enhances the antitumor effect of the virus. Furthermore, by controlling GALV.fus expression through a strict late viral promoter, whose activity depends on the initiation of viral DNA replication, we were able to express this glycoprotein in tumor cells but not in normal nondividing cells. It will be of interest to confirm whether functional expression of a strong fusogenic gene by an oncolytic herpes simplex virus enhances viral antitumor activity without increasing its toxicity.

Failure to genotype herpes simplex virus by real-time PCR assay and melting curve analysis due to sequence variation within probe binding sites

Real-time PCR with melting curve analysis of PCR products is a rapid procedure for detecting and genotyping herpes simplex virus (HSV). When testing mucocutaneous samples for HSV by a real-time PCR assay targeting the DNA polymerase gene, we found that some PCR products had atypical melting curves that did not conform to the expected melting temperatures for HSV type 1 or 2. Sequence analysis showed that these strains had base-pair mismatches over the probe binding sites. An alternative assay is required to type such atypical isolates.

Time course of seroconversion by HerpeSelect ELISA after acquisition of genital herpes simplex virus type 1 (HSV-1) or HSV-2

BACKGROUND

HerpeSelect HSV-1 and HSV-2 ELISAs are glycoprotein G-based, type-specific antibody detection tests that are approved by the US Food and Drug Administration for diagnosis of genital herpes.

GOAL

The goal was to determine seroconversion times by means of HerpeSelect ELISAs.

STUDY DESIGN

Four-hundred thirteen sera from 113 patients with recently acquired genital herpes were tested by HerpeSelect ELISAs and Western blot (WB). Thirty-one patients had primary genital HSV-1 (group 1), 56 had primary HSV-2 (group 2), and 26 had prior HSV-1 antibodies and newly acquired HSV-2 (group 3).

RESULTS

Median interval from onset of symptoms to seroconversion was 25 days, as determined by HerpeSelect HSV-1, versus 33 days by WB for group 1; 21 days by HerpeSelect HSV-2 versus 40 days by WB (group 2; P = 0.0005); and 23 days by HerpeSelect HSV-2 ELISA versus 47 days by WB (group 3; P = 0.02). In long-term follow-up, transient reversion to HerpeSelect negativity occurred in 3 of 31 HSV-1-infected subjects (10%) and in 2 of 82 HSV-2-infected subjects (2%).

CONCLUSION

Seroconversion to HSV-2 was determined faster by HerpeSelect than by WB.

Close association of predominant genotype of herpes simplex virus type 1 with eczema herpeticum analyzed using restriction fragment length polymorphism of polymerase chain reaction

Herpes simplex virus type 1 (HSV-1) strains belonging to the same genotype can possibly share biological properties and clinical manifestations common to the genotype. We classified previously 66 HSV-1 strains into 35 genotypes (F1-F35) using restriction fragment length polymorphism (RFLP) and F1 and F35 genotypes were revealed to be predominant [Arch. Virol. 13 (1993) 29]. It was found later that the F35 genotype seemed to be closely associated with eczema herpeticum [J. Med. Virol. 49 (1996) 329]. In the present study, a convenient method was developed for classification of two predominant genotypes by RFLP of polymerase chain reaction (RFLP-PCR). Using this method, genotypes of 21 strains isolated from eczema herpeticum were analyzed; seven of 21 strains (33.3%) were of F1 and five of 21 (23.8%) were of F35. Genotypes of 19 strains isolated from facial herpes other than eczema herpeticum were as follows; six of 19 (31.6%) strains were of F1 and one of 19 (5.3%) were of F35. Thus, strains belonging to F35 were appear to have been isolated more frequently from eczema herpeticum (5/21) than from facial herpes (1/19). These ratios showed a statistically significant difference. These results support the hypothesis that F35 strains is clearly associated with eczema herpeticum, in agreement with previous study. This is the first report of PCR-based approach for classification of HSV-1 strains into genotypes seeking an association of a genotype with clinical manifestation.

Strain-dependent structural variants of herpes simplex virus type 1 ICP34.5 determine viral plaque size, efficiency of glycoprotein processing, and viral release and neuroinvasive disease potential

The ability of certain strains of herpes simplex virus type 1 (HSV-1) to cause encephalitis or neuroinvasive disease in the mouse upon peripheral infection is dependent on a combination of activities of specific forms of viral proteins. The importance of specific variants of ICP34.5 to neuroinvasive disease potential and its correlation with small-plaque production, inefficient glycoprotein processing, and virus release were suggested by comparison of ICP34.5 from the SP7 virus, originally obtained from the brain of a neonate with disseminated disease, and the tissue culture-passaged progeny of SP7 (SLP5 and SLP10) and the KOS321 virus. SLP5, SLP10, and KOS321 are attenuated and exhibit a large-plaque phenotype, including efficient glycoprotein processing and viral release. We show that expression of the KOS321 ICP34.5 protein in cells infected with SP7 or ICP34.5 deletion mutants promotes large plaque formation and efficient viral glycoprotein processing, while expression of the SP7 ICP34.5 protein decreases efficiency of viral glycoprotein processing. In addition, a recombinant virus, 4hS1, with the SP7 ICP34.5 gene replacing the KOS321-like ICP34.5 gene in the SLP10a background, rescues the small-plaque phenotype and neuroinvasive disease. The major difference in the ICP34.5 gene product is the number of Pro-Ala-Thr repeats in the middle region of the protein, with 18 for SP7 and 3 for KOS321. Strain-dependent differences in the ICP34.5 protein can therefore alter the tissue culture behavior and the virulence of HSV-1.

Phenotypic and genotypic methods for the detection of herpes simplex virus serotypes

Typing of herpes simplex virus (HSV) into its serotypes plays a major role in epidemiology and management of reactivation. To develop and evaluate a polymerase chain reaction (PCR)-based restriction fragment length polymorphism (RFLP) was employed using Hae III and Taq I against neutralization test, allele-specific PCR and DNA sequencing for the detection of HSV serotypes. Neutralization test, allele-specific PCR, DNA sequencing and PCR-based RFLP were applied simultaneously to 2 standard strains (HSV-1 and HSV-2) and 23 clinical isolates. PCR-based RFLP was applied further to 20 culture negative PCR positive clinical specimens. The 179 bp product of the clinical isolates and specimens amplified using the type-common primers of HSV was subjected to DNA sequencing and PCR-based RFLP. Allele-specific PCR was absolutely specific and highly sensitive. All the typing methods differentiated concordantly 23 clinical isolates into 12 HSV-1 and 11 HSV-2. DNA sequencing did not reveal any nucleotide variations within the serotypes among the isolates sequenced. PCR-based RFLP typed a further 20 culture negative clinical specimens into 15 HSV-1 and 5 HSV-2. PCR-based RFLP was a reliable, less laborious and cost-effective molecular biological tool for the determination of HSV serotypes both for the clinical isolates and culture negative specimens.

Multiple mechanisms for HSV-1 induction of interferon alpha production by peripheral blood mononuclear cells

UV-inactivated, infectious, and other forms of herpes simplex virus 1 (HSV-1) induced interferon (IFN) production by different routes in myeloid origin mononuclear cells (MOMC) (consisting predominantly of monocytes). GM-CSF activated the MOMC (G-MOMC) to produce greater amounts of interferon while differentiation to DC, by the addition of granulocyte macrophage colony stimulating factor (GM-CSF) and calcium ionophore (GA-MOMC), reduced the levels of interferon production upon challenge with some HSV strains. UV-inactivated virus induced more interferon than infectious virus. L-fucose, an antagonist of the mannose receptor, inhibited the induction of IFN-alpha by UV-inactivated virus and gB(-) virus (defective in penetration) in MOMC and GA-MOMC but not G-MOMC. L-fucose had little effect on interferon induction by infectious HSV-1. The insensitivity of the G-MOMC to fucose inhibition distinguishes these interferon producing cells from the pDC2 cells previously described as natural interferon producing cells. The mannose receptor appears to be involved in the response to non-infectious forms of HSV but infectious virus appears to use a different pathway. These studies suggest that non-infectious virions and HSV infected cell debris effectively stimulate monocytes and pre-dendritic cells to produce IFN-alpha to initiate host protection against HSV infection.

[Utilization of hybridization in situ and PCR in situ methods to detect latent infection by the wild strain of HSV-1 and by a mutant with reduced reactivation]

The aim of the study was to detect the number of latently infected cells with wild type virus and with mutant with reduced reactivation. Using PCR in situ method we established, that the number of cells containing genome of these viruses do not differ especially between them. The number of cells with LAT expression is significantly reduced in the ganglia infected with mutant with impaired reactivation as we showed using in situ hybridization. Based on the observations of other authors, that high expression of LATs takes place in cells with high copy number of viral DNA our results showed, that after infection of mice with mutant with reduced reactivation less cells contain high copy number of viral DNA than after infection with wild type KOS. We suggest that impaired reactivation of an ICP22 mutant occurs as a result of reduced number of cells with high copy number of viral DNA.

Glycoprotein B from strain 17 of herpes simplex virus type I contains an invariant chain homologous sequence that binds to MHC class II molecules

Major histocompatibility complex class I (MHCI) molecules are major targets of virus evasion strategies because they introduce antigens from the biosynthesis pathway into the antigen-processing and presentation pathways for immune recognition by CD8+ T cells. Little is known about viral strategies that interfere with the MHC class II (MHCII) antigen presentation pathway. We identified a six amino acid sequence from type I herpes simplex virus (HSV-1) glycoprotein B (gB) that is identical to a sequence of human leucocyte antigen D (HLA-D) -associated invariant chain (Ii). In addition, this gB sequence is adjacent to a highly conserved HLA-DR1 binding motif. Both viral sequences together resemble the class II binding site of human Ii, consisting of a MHCII groove binding segment and a promiscuous binding site. We cloned gB from HSV-1 strain 17 and demonstrate association of the virus envelope protein to three HLA-DR allotypes. With chimeric Ii/gB fusion proteins we identified gB sequences that mediate promiscuous or allotype-specific binding to the HLA-DR peptide-binding domain. Mutation of two Lys residues in the viral segment of Ii/gB abolished promiscuous binding to HLA-DR heterodimers. The result indicates promiscuous binding of the virus sequence to HLA-DR molecules and suggests a potential for HSV-1 to manipulate antigen processing and presentation.

Dichotomy of glycoprotein g gene in herpes simplex virus type 1 isolates

Herpes simplex virus type 1 (HSV-1) encodes 11 envelope glycoproteins, of which glycoprotein G-1 (gG-1) induces a type-specific antibody response. Variability of the gG-1 gene among wild-type strains may be a factor of importance for a reliable serodiagnosis and typing of HSV-1 isolates. Here, we used a gG-1 type-specific monoclonal antibody (MAb) to screen for mutations in the immunodominant region of this protein in 108 clinical HSV-1 isolates. Of these, 42 isolates showed no reactivity to the anti-gG-1 MAb. One hundred five strains were further examined by DNA sequencing of the middle part of the gG-1 gene, encompassing 106 amino acids including the immunodominant region and epitope of the anti-gG-1 MAb. By phylogenetic comparisons based on the sequence data, we observed two (main) genetic variants of the gG-1 gene among the clinical isolates corresponding to reactivity or nonreactivity to the anti-gG-1 MAb. Furthermore, four strains appeared to be recombinants of the two gG-1 variants. In addition, one strain displayed a gG-1-negative phenotype due to a frameshift mutation, in the form of insertion of a cytosine nucleotide. When immunoglobulin G reactivity to HSV-1 in sera from patients infected with either of the two variants was investigated, no significant differences were found between the two groups, either in a type-common enzyme-linked immunosorbent assay (ELISA) or in a type-specific gG-1 antigen-based ELISA. Despite the here-documented existence of two variants of the gG-1 gene affecting the immunodominant region of the protein, other circumstances, such as early phase of infection, might be sought for explaining the seronegativity to gG-1 commonly found in a proportion of the HSV-1-infected patients.

Clinical and subclinical reactivation of genital herpes virus

Reactivations of herpes simplex virus (HSV) either symptomatically (recrudescence) or without symptoms (recurrence) are well documented. As an asymptomatic reactivation may contribute to transmitting HSV to potential acceptors the frequency of reactivations should be evaluated. In order to evaluate the frequency of HSV-2 reactivation 173 genital swabs of a group of women chosen at random were analyzed by nested PCR. 34 (19.6%) showed clinical evidence of a herpes infection, 77 (44.5%) had no symptoms at all and 62 (35.8%) had other symptoms. In 26 (15%) HSV-DNA was detected. 11 (38.4%) could be characterized as asymptomatic reactivations. Typing of the HSV-positive swabs resulted in 11 HSV-2 and 10 HSV-1 strains. Additionally 18 HSV-positive swabs of the oral cavity resulted in 15 (83.2%) HSV-1 and 3 (16.4%) HSV-2 strains. The results of typing indicate a change of HSV-1 and HSV-2 epidemiology.