Varicella-zoster virus gE escape mutant VZV-MSP exhibits an accelerated cell-to-cell spread phenotype in both infected cell cultures and SCID-hu mice

Varicella-zoster virus is considered to have one of the most stable genomes of all human herpesviruses. In 1998, we reported the unanticipated discovery of a wild-type virus that had lost an immunodominant B-cell epitope on the gE ectodomain (VZV-MSP); the gE escape mutant virus exhibited an unusual pattern of egress. Further studies have now documented a markedly enhanced cell-to-cell spread by the mutant virus in cell culture. This property was investigated by laser scanning confocal microscopy combined with a software program that allows the measurement of pixel intensity of the fluorescent signal. For this new application of imaging technology, the VZV immediate early protein 62 (IE 62) was selected as the fluoresceinated marker. By 48 h postinfection, the number of IE 62-positive pixels in the VZV-MSP-infected culture was nearly fourfold greater than the number of pixels in a culture infected with a low-passage laboratory strain. Titrations by infectious center assays supported the above image analysis data. Confirmatory studies in the SCID-hu mouse documented that VZV-MSP spread more rapidly than other VZV strains in human fetal skin implants. Generally, the cytopathology and vesicle formation produced by other strains at 21 days postinfection were demonstrable with VZV-MSP at 14 days. To assess whether additional genes were contributing to the unusual VZV-MSP phenotype, approximately 20 kb of the VZV-MSP genome was sequenced, including ORFs 31 (gB), 37 (gH), 47, 60 (gL), 61, 62 (IE 62), 66, 67 (gI), and 68 (gE). Except for a few polymorphisms, as well as the previously discovered mutation within gE, the nucleotide sequences within most open reading frames were identical to the prototype VZV-Dumas strain. In short, VZV-MSP represents a novel variant virus with a distinguishable phenotype demonstrable in both infected cell cultures and SCID-hu mice.

Improved identification and differentiation of varicella-zoster virus (VZV) wild-type strains and an attenuated varicella vaccine strain using a VZV open reading frame 62-based PCR

A new method was developed to identify and differentiate varicella-zoster virus (VZV) wild-type strains from the attenuated varicella Oka vaccine strain. The PCR technique was used to amplify a VZV open reading frame (ORF) 62 region. A single specific amplicon of 268 bp was obtained from 71 VZV clinical isolates and several laboratory strains. Subsequent digestion of the VZV ORF 62 amplicons with SmaI enabled accurate strain differentiation (three SmaI sites were present in amplicons of vaccine strain VZV, compared with two enzyme cleavage sites for all other VZV strains tested). This method accurately differentiated the Oka vaccine strain from wild-type VZV strains circulating in countries representing all six populated continents. Moreover, the assay more reliably distinguished wild-type Japanese strains from the vaccine strain than did previously described methods.

Diagnosis of varicella-zoster virus infections in the clinical laboratory by LightCycler PCR

Varicella-zoster virus (VZV) causes vesicular dermal lesions which are clinically evident as varicella (primary infection) or zoster (reactivated) diseases. The LightCycler system (Roche Molecular Biochemicals) is a newly developed commercially available system designed to rapidly perform PCR with real-time detection of PCR products using a fluorescence resonance energy transfer. We compared the detection of VZV from dermal specimens by shell vial cell culture (MRC-5) and by LightCycler PCR. Of 253 specimens, VZV was detected in 23 (9.1%) by shell vial cell cultures and 44 (17.4%) by LightCycler PCR directed to a nucleic acid target sequence in gene 28. Twenty-one of 44 (47.7%) specimens were exclusively positive by LightCycler PCR; the shell vial cell culture assay was never positive when DNA amplification was negative (specificity, 100%). VZV DNA was detected in 39 of 44 (88.6%) specimens positive during cycles 10 through 30 of the LightCycler PCR. These VZV DNA-positive specimens (cycles 10 to 30) and 5 of 11 other PCR positive specimens (cycles 31 to 36) were confirmed by another LightCycler PCR directed to another (gene 29) target of the viral genome. For routine laboratory practice, all specimens yielding amplified DNA to the VZV gene 28 target can be considered positive results. The increased sensitivity (91%) of the LightCycler PCR for detection of VZV, rapid turnaround time for reporting results, virtual elimination of amplicon carryover contamination, and equivalent costs compared to shell vial cell culture for detection of VZV indicate the need for implementation of this technology for routine laboratory diagnosis of this viral infection.

Acute retinal necrosis following contralateral herpes zoster ophthalmicus

BACKGROUND

A case report of contralateral acute retinal necrosis (ARN) following herpes zoster ophthalmicus.

CASE

A 61-year-old male patient developed iridocyclitis and well-demarcated creamy-white retinal lesions at the nasal periphery in the right eye 1 month after herpes zoster ophthalmicus in the left eye. The patient had undergone surgery for primary lung cancer, and had subsequent intracranial metastasis of the tumor.

OBSERVATIONS

The clinical diagnosis of ARN was supported by polymerase chain reaction investigation of the aqueous humor resulting in positive for varicella-zoster virus. Retinal lesions disappeared after systemic treatment with acyclovir, corticosteroids, and acetylsalicylate. No retinal detachment developed.

CONCLUSIONS

We propose a careful ophthalmic follow-up for herpes zoster ophthalmicus patients because of the possibility of acute retinal necrosis developing in the contralateral eye.

Sequence analysis of the leftward end of simian varicella virus (EcoRI-I fragment) reveals the presence of an 8-bp repeat flanking the unique long segment and an 881-bp open-reading frame that is absent in the varicella zoster virus genome

Simian varicella virus (SVV) causes varicella (chickenpox) in nonhuman primates, becomes latent in cranial and dorsal root ganglia, and reactivates to produce zoster (shingles). Because the clinical and molecular features of SVV closely resemble those of varicella zoster virus (VZV) infection of humans, SVV infection of primates has served as an experimental model of VZV pathogenesis and latency. The SVV genome has been completely mapped, but attempts to clone the 3600-bp EcoRI fragment located at the leftward end of the virus genome have hitherto been unsuccessful. Herein, we report the cloning and the complete nucleotide sequence of this region. Comparison of the SVV and VZV sequences in this region revealed an 8-bp inverted repeat sequence flanking the unique long segment of the SVV genome; an 879-bp open-reading frame (ORF) A in SVV that is absent in VZV but has 42% amino acid identity to SVV ORF 4 and 49% to VZV ORF 4; a 342-bp ORF B in SVV with 35% amino acid identity to a 387-bp ORF located to the left of ORF 1 on the VZV genome; and a 303-bp ORF in SVV with 27% amino acid identity to VZV ORF 1. No homologue of VZV ORF 2 was detected. Transcripts specific for ORFs A and B were present in SVV-infected cells in culture and in acutely infected monkey ganglia. Overall, there are more than 2000 bp of DNA in the SVV genome that are absent in the VZV genome.

Varicella-zoster virus infections in pregnancy

Chickenpox is an uncommon disease in women during pregnancy. If, however, maternal varicella infects the fetus, intrauterine death or severe diseases (congenital or fetal varicella syndrome) may ensue depending on the time of maternal infection. On the basis of our own clinical observations and virological testing we report on 31 women with varicella during pregnancy and their infants. Five neonates born to mothers with varicella between the 8th and 21st week showed clinical signs of the congenital varicella syndrome. Varicella-zoster virus DNA could be detected in different tissues, including lung, liver, skin and adrenal glands. As a consequence of maternal chickenpox within 12 days before delivery, 6 newborn babies developed neonatal varicella. Measures for diagnosis, treatment and prophylaxis are discussed.

Subclinical reactivation of varicella-zoster virus in immunocompromised and immunocompetent individuals

The occurrence of subclinical reactivation of varicella-zoster virus (VZV) in peripheral blood mononuclear cells (PBMC) from immunocompetent subjects >60 years old without any signs of VZV-caused illnesses, and from immunocompromised patients was investigated. Altogether, 223 samples were tested by nested ORF 63 PCR assay. In addition, all positive samples were tested by ORF 14, ORF 29 and ORF 63 PCR assays, as well as by ORF 63 and ORF 68 nucleic acid sequence-based amplification assays. In 5 samples, VZV-specific DNA, but no transcripts, could be detected. Three of them belonged to the group of >60-year-olds, 1 was HIV positive, the other was being treated with chemotherapy. The results confirm the observation of other authors that subclinical reactivation occurs in both immunocompromised and healthy individuals. The failure to detect DNA in samples taken from 2 individuals several weeks later excludes a long-lasting infection of VZV in PBMC.

Transcription factor Sp1 is involved in the regulation of varicella-zoster virus glycoprotein E

Varicella-zoster virus glycoprotein E (ORF 68) belongs to the group of late genes. It is a major component of the virion envelope and can be found complexed with glycoprotein I on the infected host cell surface. Glycoprotein E (gE) expression is activated by IE4 and IE62. Also, cellular transcription factors, like Sp1, are able to influence the gE expression. Performing quantitative reverse transcription-polymerase chain reaction, we found no decrease in Sp1 mRNA levels at different times post-infection, indicating that Sp1 mRNA evade virion host shutoff effects. In addition, the Sp1 protein was detectable in highly infected cells. Electrophoretic mobility shift assays have shown a binding of Sp1 to both GC elements within the gE-5'untranslated region (5'UTR). Additional shift assays have notified a binding of TATA box binding protein to the TATA box of the gE promoter, which is characterized by an untypical TATACA motif. Promoter-reporter constructs have been made using mutated variants of the gE-5'UTR as promoters. In transfection studies, we found that the TATA deletion, as well as inactivations of both GC boxes, reduced the basal activity of the promoter. A complete loss of activity did not become measurable until eliminating both GC elements and the TATA box, indicating that these cis-elements substitute for each other in initiation of transcription of the gE-5'UTR.

Diagnostic utility of a multiplex herpesvirus PCR assay performed with cerebrospinal fluid from human immunodeficiency virus-infected patients with neurological disorders

We used a multiplex nested-PCR assay for the simultaneous detection in cerebrospinal fluid (CSF) of five human herpesviruses (HVs) (cytomegalovirus [CMV], Epstein-Barr virus [EBV], varicella-zoster virus [VZV], herpes simplex virus [HSV], and human herpesvirus 6 [HHV-6]) in a clinical evaluation of human immunodeficiency virus (HIV)-infected patients with neurological disorders. This method, which has the advantages of being rapid and economical, would be of particular interest for the diagnosis of neurological syndromes caused by more than one HV. We studied 251 CSF samples from 219 patients. HV DNA was demonstrated in 93 (37%) of the CSF samples (34% of the patients). CMV was the HV most frequently detected in our patients (25%), while EBV, VZV, HSV, and HHV-6 DNAs were present in significantly fewer cases (7, 4, 3, and 1%, respectively). When results were compared with the final etiological diagnoses of the patients, the multiplex HV PCR showed high specificity for the diagnosis of CMV and VZV neurological diseases and for cerebral lymphoma (0.95, 0.97, and 0.99, respectively). The sensitivity of the assay was high for CMV disease (0.87), was low for cerebral lymphoma (0.33), and was not evaluable for VZV disease due to the small number of patients with this diagnosis. Nevertheless, detection of VZV DNA had possible diagnostic value in four of the nine cases, and EBV DNA amplification always predicted the diagnosis of cerebral lymphoma in patients with cerebral masses. Detection of HSV DNA was frequently associated with CMV amplification and fatal encephalitis. HHV-6 was not considered to have a pathogenetic role in the three cases in which it was detected. This multiplex HV PCR assay is a specific and clinically useful method for the evaluation of HIV-infected patients with neurological disorders related to HV.

Comparison between of the attenuated BR-Oka and the wild type strain of Varicella Zoster Virus (VZV) on the DNA level

Oka strain VR-795 (Varicella Zoster Virus, VZV) of American Type Culture Collection (ATCC) has been used for chickenpox vaccine production. In order to use this strain for vaccine production, the strain must be identified and its stability must be confirmed. The identification of the Oka strain has been confirmed using Restriction Fragment Length Polymorphism (RFLP) and DNA sequence analysis of glycoprotein-II (gp-II). The amino acid sequences of Oka deduced from the DNA sequence of gp-II have changed at three amino acids against Ellen and at one amino acid against Webster. To prove the stability of the Oka strain during the passage, RFLP and DNA sequence analyses were also used with 11, 15 and 23 times of virus passage. We found that the Oka strain was stable at passages of up to 23 times, based on the RFLP and DNA sequence analyses. The confirmed Oka strain was renamed as BR-Oka for the purposes of chickenpox vaccine production.

[Detection of varicella-zoster virus DNA in tear fluid and saliva of patients with Ramsay Hunt syndrome]

Ramsay Hunt syndrome develops when the varicella-zoster virus (VZV) is reactivated. In the present study, we examined the secretion kinetics of VZV DNA in the tear fluid, submandibular gland saliva and parotid gland saliva of 15 patients with Ramsay Hunt syndrome. The presence of VZV DNA was detected using PCR and a microplate hybridization method. Hybridization signals were measured using the fluorescence density of an enzymatic reaction product using fluoroscan and a system involving streptavidin-conjugated beta-galactosidase. The results were converted into numerical values and used to estimate the number of virus DNA copies. VZV DNA was detected in the tear fluid, submandibular gland saliva and parotid gland saliva of the Ramsay Hunt syndrome patients. The rate of VZV DNA detection in the submandibular gland saliva was 72%, and the detection rate in the parotid gland saliva was 57%. The detection rate in the tear fluid was 27%, which is significantly lower than other two detection rates. Regarding the submandibular gland saliva and the parotid gland saliva, the VZV DNA was detected in samples collected at a comparatively early stage of onset. In the tear fluid, the detection rate increased significantly in samples collected 2 weeks after onset or later. Thus, differences in the detection rate were observed depending on the type of secretory gland and the timing of the sample collection. The VZV DNA in the tear fluid is thought to derive from the ganglion trigeminale. The increase and decrease in the number of VZV DNA copies detected in samples collected at different times is considered to substantiate VZV reactivation in Ramsay Hunt syndrome.

Oka varicella vaccine is distinguishable from its parental virus in DNA sequence of open reading frame 62 and its transactivation activity

When the nucleotide sequences of the Oka vaccine and its parental varicella-zoster virus (VZV) were compared in 6 open reading frames (ORFs), glycoprotein C (gC) and 5 transactivator genes, mutations were detected only in the immediate-early gene 62. The vaccine virus contained a mixture of different sequences that had variations at 15 nucleotide positions, but only one sequence was found for the Oka parental virus gene 62. The Oka vaccine virus gene 62 could be distinguished from the parental virus gene using a simplified restriction-enzyme fragment length polymorphism analysis, using NaeI and BssHII. This analysis was based on the sequence data obtained in this study. Studies of the regulatory activities of the ORF62 gene product (IE62) in a transient transfection assay indicated that IE62 of the parental virus had a stronger transactivational activity than that of the vaccine virus in activating immediate-early, early, and late gene promoters. These data suggest that IE62 might play an important role in the attenuation of VZV.

Physical interaction between two varicella zoster virus gene regulatory proteins, IE4 and IE62

Transfection assays demonstrate that the varicella zoster virus (VZV) immediate-early 62 (IE62) protein is a major transactivator of VZV gene expression, whereas a second immediate-early protein, IE4, can act as a major coactivator of transactivation mediated through IE62. To test whether IE62 and IE4 interact physically, we performed several protein-protein interaction assays. Coimmunoprecipitation analyses using VZV-infected cell lysates as well as purified protein mixtures demonstrate that IE62 and IE4 form stable complexes in solution under stringent salt conditions. Enzyme-linked immunosorbent assay protein-protein interaction assays and maltose-binding protein capture assays demonstrate that IE62 binds IE4 in a concentration- and dose-dependent manner. Far Western blot analyses show that IE4 binds to an undermodified form of IE62, and the use of calf intestinal phosphatase and protein kinases suggests that the interaction with IE4 is dependent on the phosphorylation state of IE62. An IE4 binding domain on IE62 has been mapped using a set of truncated IE62 fusion peptides. Collectively, these results imply a direct and specific physical interaction between IE4 and less-phosphorylated forms of IE62. These data have implications for virion assembly, as well as for the regulation of gene expression in VZV-infected cells.

Quantitation of varicella-zoster virus DNA in whole blood, plasma, and serum by PCR and electrochemiluminescence

We describe a highly sensitive assay for quantitation of varicella-zoster virus (VZV) DNA in blood, involving PCR amplification, solution hybridization with Tris-(2, 2'-bipyridine)-ruthenium(II) chelate-labeled probes, and measurement by electrochemiluminescence (ECL). Extraction and amplification efficiencies were monitored by the inclusion of internal control (IC) DNA, mimicking the VZV target, in the DNA extraction. Viral DNA load was calculated from the ratio of VZV and IC ECL signals. The lower limit of sensitivity was 20 VZV DNA copies/ml of plasma or serum and 80 copies/ml of whole blood. In reconstruction experiments, expected and calculated VZV DNA loads were in excellent accordance. Blood specimens from 42 VZV-infected patients were tested for the presence of VZV DNA and showed detection rates of 86% in patients with varicella and 81% in patients with herpes zoster. In specimens obtained during the first week after onset of the rash, detection rates were 100 and 89%, respectively. Viral DNA was detected in all immunocompromised patients with herpes zoster, emphasizing the risk of disseminated disease in this patient group. VZV DNA load was similar in patients with varicella and multidermatomal herpes zoster and lower in patients with unidermatomal zoster. Despite the cell-associated nature of the virus, VZV DNA was detected in serum and plasma at high copy numbers, and at similar frequencies compared to whole-blood specimens. Quantitation of VZV DNA in blood is of potential importance for diagnosis and clinical management of VZV-infected patients. Plasma and serum provide convenient matrices for this purpose.

Quantitation of varicella-zoster virus DNA in whole blood, plasma, and serum by PCR and electrochemiluminescence

We describe a highly sensitive assay for quantitation of varicella-zoster virus (VZV) DNA in blood, involving PCR amplification, solution hybridization with Tris-(2, 2'-bipyridine)-ruthenium(II) chelate-labeled probes, and measurement by electrochemiluminescence (ECL). Extraction and amplification efficiencies were monitored by the inclusion of internal control (IC) DNA, mimicking the VZV target, in the DNA extraction. Viral DNA load was calculated from the ratio of VZV and IC ECL signals. The lower limit of sensitivity was 20 VZV DNA copies/ml of plasma or serum and 80 copies/ml of whole blood. In reconstruction experiments, expected and calculated VZV DNA loads were in excellent accordance. Blood specimens from 42 VZV-infected patients were tested for the presence of VZV DNA and showed detection rates of 86% in patients with varicella and 81% in patients with herpes zoster. In specimens obtained during the first week after onset of the rash, detection rates were 100 and 89%, respectively. Viral DNA was detected in all immunocompromised patients with herpes zoster, emphasizing the risk of disseminated disease in this patient group. VZV DNA load was similar in patients with varicella and multidermatomal herpes zoster and lower in patients with unidermatomal zoster. Despite the cell-associated nature of the virus, VZV DNA was detected in serum and plasma at high copy numbers, and at similar frequencies compared to whole-blood specimens. Quantitation of VZV DNA in blood is of potential importance for diagnosis and clinical management of VZV-infected patients. Plasma and serum provide convenient matrices for this purpose.

Characterization of interaction of gH and gL glycoproteins of varicella-zoster virus: their processing and trafficking

Varicella-zoster virus (VZV) glycoproteins gH and gL were examined in a recombinant vaccinia virus system. Single expression of glycoprotein gL produced two molecular forms: an 18 kDa form and a 19 kDa form differing in size by one endoglycosidase H-sensitive N-linked oligosaccharide. Coexpression of gL and gH resulted in binding of the 18 kDa gL form with the mature form of gH, while the 19 kDa gL form remained uncomplexed. The glycosylation processing of gL was not dependent on gH; however, gL was required for the conversion of precursor gH (97 kDa) to mature gH (118 kDa). Subsequent analyses indicated that gL (18 kDa) was a more completely processed gL (19 kDa). Screening of the culture media revealed that gH and gL were secreted, but only if coexpressed and complexed together. The secreted form of gL was 18 kDa while that of gH was 114 kDa. The fact that secreted gH was smaller than intracytoplasmic gH suggested a proteolytic processing event prior to secretion. The 19 kDa form of gL was never secreted. These findings support a VZV gL recycling pathway between the endoplasmic reticulum and the cis-Golgi apparatus.

Zoster sine herpete with bilateral ocular involvement

PURPOSE

To report a case of zoster sine herpete with bilateral ocular involvement.

METHOD

Case report.

RESULTS

A 65-year-old man showed bilateral iridocyclitis with sectoral iris atrophy and elevated intraocular pressure unresponsive to steroid treatment. No cutaneous eruption was manifest on the forehead. A target region of varicella-zoster virus DNA sequence was amplified from the aqueous sample from the left eye by polymerase chain reaction. Bilateral iridocyclitis resolved promptly after initiation of systemic and topical acyclovir treatment. Secondary glaucoma was well controlled by bilateral trabeculectomy.

CONCLUSIONS

Zoster sine herpete should be considered and polymerase chain reaction performed on an aqueous sample to detect varicella-zoster virus DNA for rapid diagnosis whenever anterior uveitis accompanies the characteristic iris atrophy, even in the case of bilateral involvement.

Anterior uveitis with sectoral iris atrophy in the absence of keratitis: a distinct clinical entity among herpetic eye diseases

OBJECTIVE

To determine the cause and describe the clinical features of unilateral anterior uveitis with sectoral atrophy of the iris in the absence of associated keratitis.

DESIGN

Retrospective, observational case series.

PARTICIPANTS

Thirty-one patients with unilateral anterior uveitis with sectoral iris atrophy and without (previous) keratitis.

METHODS

The patients were selected from our database of 592 patients with anterior uveitis.

MAIN OUTCOME MEASURES

We reviewed the clinical data on the 31 patients and the results of diagnostic anterior chamber fluid analysis for 24 of the 31 patients. Specifically, production of local antibodies against herpes simplex virus (HSV) and varicella zoster virus (VZV) was determined and the polymerase chain reaction was performed to demonstrate the DNA of HSV, VZV, and cytomegalovirus (CMV) in the aqueous samples.

RESULTS

Main clinical characteristics of anterior uveitis with iris atrophy included unilateral involvement with a prolonged course and recurrent exacerbations in all cases. Elevated intraocular pressure during intraocular inflammation occurred in 90% of patients (28 of 31). Visual outcome was favorable because 29 of 31 patients (94%) retained a visual acuity of 20/32 or more. The causal agent was identified as HSV in 83% (20 of 24) and VZV in 13% (3 of 24) and was inconclusive in one case. The patients with HSV uveitis were younger than those with VZV uveitis (mean age at onset 34 and 65 years, respectively; P = 0.0056).

CONCLUSIONS

Unilateral anterior uveitis with sectoral atrophy of the iris without associated (previous) keratitis is a distinct entity among herpetic eye diseases. Recurrent unilateral anterior uveitis with iris atrophy and/or elevated intraocular pressure has most likely been caused by HSV.

Characterization of acyclovir susceptibility and genetic stability of varicella-zoster viruses isolated during acyclovir therapy

We have characterized the susceptibility and genetic stability of varicella-zoster viruses (VZV) isolated from skin lesions of three patients with herpes zoster and six patients with varicella treated with conventional short-term acyclovir (ACV) administration. The susceptibilities to ACV of the serial isolates from the patients were examined, and there was no significant difference in the susceptibility to ACV among the isolates before and during the ACV treatment, indicating that conventional short-term ACV treatment did not generate ACV-resistant VZV infections. Polymerase chain reaction (PCR) analyses of these as well as seven thymidine kinase-deficient VZV strains derived from in vitro ACV treatment were carried out to examine their genomic stability. Five regions containing tandem direct reiterations (R1-R5) were amplified by PCR and compared, and the region containing the Pst I-site was also examined. PCR analyses demonstrated that the R1, R5 and the Pst I-sites were stable and useful in epidemiological studies even after ACV treatment. The R2, R3 and R4 sites were far less stable in these experimental conditions. In this paper we discuss the results of the PCR analyses with regard to the dynamics of VZV population in patients with VZV infection treated with conventional short-term ACV administration.

Rapid phenotypic characterization method for herpes simplex virus and Varicella-Zoster virus thymidine kinases to screen for acyclovir-resistant viral infection

A rapid phenotypic screening method for herpes simplex virus (HSV) and varicella-zoster virus (VZV) thymidine kinase (TK) genes was developed for monitoring acyclovir-resistant viruses. This method determines the biochemical phenotype of the TK polypeptide, which is synthesized in vitro from viral DNA using a procedure as follows. The TK gene of each sample virus strain is amplified and isolated under the control of a T7 promoter by PCR. The PCR products are transcribed with T7 RNA polymerase and translated in a rabbit reticulocyte lysate. Using this method, enzymatic characteristics and the size of the TK polypeptides encoding HSV and VZV DNA were defined in less than 2 days without virus isolation. The assay should be a powerful tool in monitoring drug-resistant viruses, especially in cases in which virus isolation is difficult.

A rapid phenotypic assay for detection of acyclovir-resistant varicella-zoster virus with mutations in the thymidine kinase open reading frame

Susceptibility assays by cell culture methods are time-consuming and are particularly difficult to perform with varicella-zoster virus (VZV). To overcome this limitation, we have adapted a functional test of the viral thymidine kinase (TK) in TK-deficient (tdk mutant) bacteria to detect ACV-resistant VZV in clinical samples. After PCR amplification, the complete viral TK open reading frame (ORF) is purified from PCR primers, digested with two restriction enzymes, and ligated in an oriented fashion into a bacterial expression vector. The ligation products are then used to transform tdk mutant bacteria. After transformation, an aliquot of the bacteria is plated onto a plate with minimal medium containing (i) ampicillin to select for plasmids carrying the viral TK ORF and (ii) isopropyl beta-D-thiogalactopyranoside (IPTG) to induce its expression. An identical aliquot of bacteria is also plated onto a medium containing, in addition to the components described above, 5-fluorodeoxyuridine (FUdR). Compared to the number of transformants on FUdR-free medium, the number of colonies carrying TK derived from susceptible strains was reduced by 86%, on average, in the presence of FUdR. In contrast, the number of transformants carrying TK from resistant strains with a mutant TK were reduced by only 4%, on average, on FUdR-containing plates. We have assessed the validity of this assay with cell culture isolates and several clinical samples including two cerebrospinal fluid samples from which no virus could be isolated. This colony reduction assay allowed the correct identification of the TK phenotype of each VZV isolate tested and can be completed within 3 days of receipt of the sample.

Comparison of virus isolation and various polymerase chain reaction methods in the diagnosis of mucocutaneous herpesvirus infection

We compared two polymerase chain reaction (PCR) assays (simple and multiplex) and viral isolation to detect herpes simplex virus 1 (HSV-1) and varicella-zoster virus (VZV) in 15 clinical specimens from 13 patients with mucocutaneous herpetic infections. HSV-1 or VZV DNA was detected in 13 specimens by simple PCRs (HSV-1 or VZV PCR) and in 12 specimens by multiplex PCR. On the other hand, viral isolation was positive for 9 specimens only. The PCR protocols used in this study are not only more sensitive and faster than the traditional viral isolation and conventional PCR protocols but also can distinguish rapidly HSV-1 from VZV. We propose the PCRs described here for rapid and precise identification of etiological agents of mucocutaneous herpetic infections.

[The relationship between gene function and virulence in alpha-herpesviruses]

Virulent alpha-herpesvirus genes, though not essential for virus replication in cell culture, play important roles in virus replication in vivo. In this paper, I classify the virulent genes and discuss the relationship between gene function and virulence. The products of the virulent genes of herpes simplex virus, described in this paper, are enzymes (thymidine kinase, ribonucleotide reductase, deoxyuridine triphosphatase, DNA polymerase, and two protein kinases), glycoproteins (gC, gE), immediate early gene product (ICP47) and gamma 34.5. To identify the virulent genes of varicellazoster virus, mutation in the Oka vaccine strain was studied. The low levels of gV expression and mutation found in the immediate early gene were predicted as the cause of the attenuation of the Oka vaccine strain.

[Diagnosis of Ramsey Hunt syndrome is both simple and difficult. The viral attack is more extensive than expected earlier]

In Ramsay Hunt's syndrome (herpes zoster of the head and neck in combination with facial palsy), the vesicles often appear on the external ear (herpes zoster oticus) but they can also be found on the exterior of the neck. Serologically verified cases without vesicles occur (zoster sine herpeticum). Complications from the eighth cranial nerve (hearing loss and vertigo) are common. MR and PCR studies show a more extensive viral attack than was earlier believed to be the case. Due to the risk of remaining cranial nerve dysfunctions, as exemplified in a case report, antiviral treatment is indicated, in severe cases combined with corticosteroids. The potential value of varicella vaccination to reduce zoster complications is discussed.