Expression of protein encoded by varicella-zoster virus open reading frame 63 in latently infected human ganglionic neurons

Varicella-zoster virus latency in human ganglia

Varicella-zoster virus (VZV) is a human herpesvirus which causes varicella (chickenpox) as a primary infection, and, following a variable period during which it remains in latent form in trigeminal and dorsal root ganglia, reactivates in later life to cause herpes zoster (shingles). VZV is a significant cause of neurological disease including post-herpetic neuralgia which may be persistent and highly resistant to treatment, and small and large vessel encephalitis. VZV infections are more frequent with advancing age and in immunocompromised individuals. An understanding of the mechanisms of latency is crucial in developing effective therapies for VZV infections of the nervous system. Such studies have been hampered by the difficulties in working with the virus and also the lack of a good animal model of VZV latency. It is known that the ganglionic VZV burden during latency is low. Two of the key questions that have been addressed are the cellular site of latent VZV and the identity of the viral genes which are transcribed during latency. There is now a consensus that latent VZV resides predominantly in ganglionic neurons with less frequent infection of non-neuronal satellite cells. There is considerable evidence to show that at least five viral genes are transcribed during latency. Unlike herpes simplex virus-1 latency, viral protein expression has been demonstrated during VZV latency. A precise knowledge of which viral genes are expressed is crucial in devising novel antiviral therapy using expressed genes as therapeutic targets. Whether gene expression at both the transcriptional and translational levels is more extensive than currently reported will require much more work and probably new molecular technology.

Naturally acquired simian varicella virus infection in African green monkeys

Simian varicella virus (SVV) infection of primates shares clinical, pathological, immunological, and virological features with varicella-zoster virus infection of humans. Natural varicella infection was simulated by exposing four SVV-seronegative monkeys to monkeys inoculated intratracheally with SVV, in which viral DNA and RNA persist in multiple tissues for more than 1 year (T. M. White, R. Mahalingam, V. Traina-Dorge, and D. H. Gilden, J. Neurovirol. 8:191-205, 2002). The four naturally exposed monkeys developed mild varicella 10 to 14 days later, and skin scrapings taken at the time of the rash contained SVV DNA. Analysis of multiple ganglia, liver, and lung tissues from the four naturally exposed monkeys sacrificed 6 to 8 weeks after resolution of the rash revealed SVV DNA in ganglia at multiple levels of the neuraxis but not in the lung or liver tissue of any of the four monkeys. This animal model provides an experimental system to gain information about varicella latency with direct relevance to the human disease.

Use of an inactivated varicella vaccine in recipients of hematopoietic-cell transplants

BACKGROUND

The reactivation of varicella-zoster virus from latency causes zoster and is common among recipients of hematopoietic-cell transplants.

METHODS

We randomly assigned patients who were scheduled to undergo autologous hematopoietic-cell transplantation for non-Hodgkin's or Hodgkin's lymphoma to receive varicella vaccine or no vaccine. Heat-inactivated, live attenuated varicella vaccine was given within 30 days before transplantation and 30, 60, and 90 days after transplantation. The patients were monitored for zoster and for immunity against varicella-zoster virus for 12 months.

RESULTS

Of the 119 patients enrolled, 111 received a transplant. Zoster developed in 7 of 53 vaccinated patients (13 percent) and in 19 of 58 unvaccinated patients (33 percent) (P=0.01). After two patients in whom zoster developed before transplantation were excluded, the respective rates were 13 percent and 30 percent (P=0.02). In vitro CD4 T-cell proliferation in response to varicella-zoster virus (expressed as the mean stimulation index) was greater in patients who received the vaccine than in those who did not at 90 days, after three doses (P=0.04); at 120 days, after all four doses (P<0.001); at 6 months (P=0.004); and at 12 months (P=0.02). The risk of zoster was reduced for each unit increase in the stimulation index above 1.6; a stimulation index above 5.0 correlated with greater than 93 percent protection. Induration, erythema, or local pain at the injection site was observed in association with 10 percent of the doses.

CONCLUSIONS

Inactivated varicella vaccine given before hematopoietic-cell transplantation and during the first 90 days thereafter reduces the risk of zoster. The protection correlates with reconstitution of CD4 T-cell immunity against varicella-zoster virus.

Characterization of varicella-zoster virus gene 21 and 29 proteins in infected cells

Varicella-zoster virus (VZV) transcription is limited in latently infected human ganglia. Note that much of the transcriptional capacity of the virus genome has not been analyzed in detail; to date, only VZV genes mapping to open reading frames (ORFs) 4, 21, 29, 62, and 63 have been detected. ORF 62 encodes the major immediate-early virus transcription transactivator IE62, ORF 29 encodes the major virus DNA binding protein, and ORF 21 encodes a protein associated with the developing virus nucleocapsid. We analyzed the cellular location of proteins encoded by ORF 21 (21p) and ORF 29 (29p), their phosphorylation state during productive infection, and their ability form a protein-protein complex. The locations of both 21p and 29p within infected cells mimic those of their herpes simplex virus type 1 (HSV-1) homologues (UL37 and ICP8); however, unlike these homologues, 21p is not phosphorylated and neither 21p nor 29p exhibits a protein-protein interaction. Transient transfection assays to determine the effect of 21p and 29p on transcription from VZV gene 20, 21, 28, and 29 promoters revealed no significant activation of transcription by 21p or 29p from any of the VZV gene promoters tested, and 21p did not significantly modulate the ability of IE62 to activate gene transcription. A modest increase in IE62-induced activation of gene 28 and 29 promoters was seen in the presence of 29p; however, IE62-induced activation of gene 28 and 29 promoters was reduced in the presence of 21p. A Saccharomyces cerevisiae two-hybrid analysis of 21p indicated that the protein can activate transcription when tethered within a responsive promoter. Together, the data reveal that while VZV gene 21 and HSV-1 UL37 share homology at the nucleic acid level, these proteins differ functionally.

Phosphorylation of varicella-zoster virus IE63 protein by casein kinases influences its cellular localization and gene regulation activity

During the early phase of varicella-zoster virus (VZV) infection, Immediate Early protein 63 (IE63) is expressed rapidly and abundantly in the nucleus, while during latency, this protein is confined mostly to the cytoplasm. Because phosphorylation is known to regulate many cellular events, we investigated the importance of this modification on the cellular localization of IE63 and on its regulatory properties. We demonstrate here that cellular casein kinases I and II are implicated in the in vitro and in vivo phosphorylation of IE63. A mutational approach also indicated that phosphorylation of the protein is important for its correct cellular localization in a cell type-dependent fashion. Using an activity test, we demonstrated that IE63 was able to repress the gene expression driven by two VZV promoters and that phosphorylation of the protein was required for its full repressive properties. Finally, we showed that IE63 was capable of exerting its repressive activity in the cytoplasm, as well as in the nucleus, suggesting a regulation at the transcriptional and/or post-transcriptional level.

Simian varicella virus DNA is present and transcribed months after experimental infection of adult African green monkeys

To study the pathogenesis of simian varicella virus (SVV) infection in its natural primate host, we inoculated adult SVV-seronegative African green monkeys intratracheally with 10(3)-10(4) PFU of SVV, sacrificed them 11 days, 2, 5, 10, and 12 months postinfection (p.i.), and examined lung, liver, and ganglia for SVV DNA and RNA. PCR analysis revealed SVV DNA in ganglia and viscera at 11 days and 2, 5, and 10 months p.i. Similarly, SVV transcripts corresponding to immediate early (IE), putative early (E), and late (L) SVV open-reading frames (ORFs) were found in liver, lung, and ganglia of most monkeys at multiple intervals for the 12-month study period. SVV-specific antigens were detected in ganglia and liver during acute varicella, but not in ganglia 12 months p.i. Analysis of control tissue (ganglia, lung, and liver) from uninfected SVV-seronegative adult African green monkeys did not reveal SVV DNA, SVV RNA, SVV-specific antigen, or varicella-specific pathological changes. Overall, intratracheal inoculation of SVV in African green monkeys resulted in the presence of viral DNA and transcription of multiple viral genes in many tissues for months after experimental infection.

Spontaneous molecular reactivation of herpes simplex virus type 1 latency in mice

Infection of the mouse trigeminal ganglia (TG) is the most commonly used model for the study of herpes simplex virus type 1 (HSV-1) latency. Its popularity is caused, at least in part, by the perception that latent infection can be studied in this system in the absence of spontaneous viral reactivation. However, this perception has never been rigorously tested. To carefully study this issue, the eyes of Swiss-Webster mice were inoculated with HSV-1 (KOS), and 37-47 days later the TG were dissected, serial-sectioned, and probed for HSV-1 ICP4, thymidine kinase, glycoprotein C, and latency-associated transcript RNA by in situ hybridization. Serial sections of additional latently infected TG were probed with HSV-1-specific polyclonal antisera. Analysis of thousands of probed sections revealed abundant expression of viral transcripts, viral protein, and viral DNA replication in about 1 neuron per 10 TG tested. These same neurons were surrounded by a focal white cell infiltrate, indicating the presence of an antigenic stimulus. We conclude that productive cycle viral genes are abundantly expressed in rare neurons of latently infected murine TG and that these events are promptly recognized by an active local immune response. In the absence of detectable infectious virus in these ganglia, we propose the term "spontaneous molecular reactivation" to describe this ongoing process.

Herpes zoster infection and postherpetic neuralgia

Varicella-zoster virus (VZV), the cause of chicken pox, establishes latent infection in sensory ganglia. Reactivation results in zoster (shingles), sometimes complicated by encephalitis (myelitis). Postherpetic neuralgia (PHN) is the major morbidity of zoster. PHN typically increases in frequency with age. The VZV vaccine, which was developed for children, may be effective in enhancing VZV immune reactivity and decreasing zoster in adults. Early antiviral treatment may be effective in decreasing PHN onset. Several other medications may be useful in treating established PHN. A recent report discussed intrathecal steroid use.

Varicella-Zoster virus gene expression in latently infected rat dorsal root ganglia

Latent infection of human ganglia with Varicella-Zoster virus (VZV) is characterized by a highly restricted pattern of viral gene expression. To enhance understanding of this process we used in situ hybridization (ISH) in a rat model of VZV latency to examine expression of RNA corresponding to eight different VZV genes in rat dorsal root ganglia (DRG) at various times after footpad inoculation with wild-type VZV. PCR in situ amplification was also used to determine the cell specificity of latent VZV DNA. It was found that the pattern of viral gene expression at 1 week after infection was different from that observed at the later times of 1 and 18 months after infection. Whereas multiple genes were expressed at 1 week after infection, gene expression was restricted at the later time points when latency had been established. At the later time points after infection the RNA transcripts expressed most frequently were those for VZV genes 21, 62, and 63. Gene 63 was expressed more than any other gene studied. While VZV DNA was detected almost exclusively in 5-10% of neurons, VZV RNA was detected in both neurons and nonneuronal cells at an approximate ratio of 3:1. A newly described monoclonal antibody to VZV gene 63-encoded protein was used to detect this protein in neuronal nuclei and cytoplasm in almost half of the DRG studied. These results demonstrate that (1) this rat model of latency has close similarities in terms of viral gene expression to human VZV latency which makes it a useful tool for studying this process and its experimental modulation and (2) expression of VZV gene 63 appears to be the single most consistent feature of VZV latency.

Mutational analysis of the repeated open reading frames, ORFs 63 and 70 and ORFs 64 and 69, of varicella-zoster virus

Varicella-zoster virus (VZV) open reading frame 63 (ORF63), located between nucleotides 110581 and 111417 in the internal repeat region, encodes a nuclear phosphoprotein which is homologous to herpes simplex virus type 1 (HSV-1) ICP22 and is duplicated in the terminal repeat region as ORF70 (nucleotides 118480 to 119316). We evaluated the role of ORFs 63 and 70 in VZV replication, using recombinant VZV cosmids and PCR-based mutagenesis to make single and dual deletions of these ORFs. VZV was recovered within 8 to 10 days when cosmids with single deletions were transfected into melanoma cells along with the three intact VZV cosmids. In contrast, VZV was not detected in transfections carried out with a dual deletion cosmid. Infectious virus was recovered when ORF63 was cloned into a nonnative AvrII site in this cosmid, confirming that failure to generate virus was due to the dual ORF63/70 deletion and that replication required at least one gene copy. This requirement may be related to our observation that ORF63 interacts directly with ORF62, the major immediate-early transactivating protein of VZV. ORF64 is located within the inverted repeat region between nucleotides 111565 and 112107; it has some homology to the HSV-1 Us10 gene and is duplicated as ORF69 (nucleotides 117790 to 118332). ORF64 and ORF69 were deleted individually or simultaneously using the VZV cosmid system. Single deletions of ORF64 or ORF69 yielded viral plaques with the same kinetics and morphology as viruses generated with the parental cosmids. The dual deletion of ORF64 and ORF69 was associated with an abnormal plaque phenotype characterized by very large, multinucleated syncytia. Finally, all of the deletion mutants that yielded recombinants retained infectivity for human T cells in vitro and replicated efficiently in human skin in the SCIDhu mouse model of VZV pathogenesis.

Varicella-zoster virus ORF47 protein serine kinase: characterization of a cloned, biologically active phosphotransferase and two viral substrates, ORF62 and ORF63

Varicella-zoster virus (VZV) codes for a protein serine kinase called ORF47; the herpes simplex virus (HSV) homolog is UL13. No recombinant alphaherpesvirus serine kinase has been biologically active in vitro. We discovered that preservation of the intrinsic kinase activity of recombinant VZV ORF47 required unusually stringent in vitro conditions, including physiological concentrations of polyamines. In this assay, ORF47 phosphorylated two VZV regulatory proteins: the ORF62 protein (homolog of HSV ICP4) and the ORF63 protein (homolog of HSV ICP22). Of interest, ORF47 kinase also coprecipitated ORF63 protein from the kinase assay supernatant.

Varicella-Zoster virus infections of the nervous system: clinical and pathologic correlates

BACKGROUND

Diseases that present with protean manifestations are the diseases most likely to pose diagnostic challenges for both clinicians and pathologists. Among the most diverse disorders caused by a single known toxic, metabolic, neoplastic, or infectious agent are the central and peripheral nervous system complications of varicella-zoster virus (VZV).

METHODS

The pathologic correlates of the neurologic complications of VZV infection, as well as current methods for detecting viral infections, are discussed and presented in pictorial format for the practicing pathologist.

RESULTS

Varicella-zoster virus causes chickenpox (varicella), usually in childhood; most children manifest only mild neurologic sequelae. After chickenpox resolves, the virus becomes latent in neurons of cranial and spinal ganglia of nearly all individuals. In elderly and immunocompromised individuals, the virus may reactivate to produce shingles (zoster). After zoster resolves, many elderly patients experience postherpetic neuralgia. Uncommonly, VZV can spread to large cerebral arteries to cause a spectrum of large-vessel vascular damage, ranging from vasculopathy to vasculitis, with stroke. In immunocompromised individuals, especially those with cancer or acquired immunodeficiency syndrome, deeper tissue penetration of the virus may occur (as compared with immunocompetent individuals), with resultant myelitis, small-vessel vasculopathy, ventriculitis, and meningoencephalitis. Detection of the virus in neurons, oligodendrocytes, meningeal cells, ependymal cells, or the blood vessel wall often requires a combination of morphologic, immunohistochemical, in situ hybridization, and polymerase chain reaction (PCR) methods. The PCR analysis of cerebrospinal fluid remains the mainstay for diagnosing the neurologic complications of VZV during life.

CONCLUSIONS

Varicella-zoster virus infects a wide variety of cell types in the central and peripheral nervous system, explaining the diversity of clinical disorders associated with the virus.

The role of varicella zoster virus immediate-early proteins in latency and their potential use as components of vaccines

Varicella zoster virus immediate-early (IE) proteins are intracellular regulators of viral gene expression. Some of them (IE62 and IE63) are found in large amounts in infected cells but are also components of the virion tegument. Several IE and early genes are transcribed during latency, while late genes are not. Recently, we demonstrated the presence of protein IE 63 in dorsal root ganglia of persistently infected rats as well as in normal human ganglia; other IE proteins have been found since in human ganglia. Cell-mediated immunity (CMI) to IE 62 has been evidenced. We found both humoral immunity and CMI to IE 63 in immune adults. In elderly zoster-free individuals, CMI to IE 63 remained high. The differences in the CMI to IE 63 among young adults, elderly people and immunocompromized patients have to be analyzed according to their status relative to zoster, to determine whether the decrease in CMI, particularly to IE proteins, could be responsible for viral reactivation and for the onset of shingles. Hopefully, the waning of the CMI to VZV IE 63 and perhaps to other IE proteins could become a predictive marker for herpes zoster and reimmunization, not only with the vaccine strain, but also with purified IE proteins could help prevent zoster at old age.

Varicella-zoster virus gene expression in latently infected and explanted human ganglia

A consistent feature of varicella-zoster virus (VZV) latency is the restricted pattern of viral gene expression in human ganglionic tissues. To understand further the significance of this gene restriction, we used in situ hybridization (ISH) to detect the frequency of RNA expression for nine VZV genes in trigeminal ganglia (TG) from 35 human subjects, including 18 who were human immunodeficiency virus (HIV) positive. RNA for VZV gene 21 was detected in 7 of 11 normal and 6 of 10 HIV-positive subjects, RNA for gene 29 was detected in 5 of 14 normal and 11 of 11 HIV-positive subjects, RNA for gene 62 was detected in 4 of 10 normal and 6 of 9 HIV-positive subjects, and RNA for gene 63 was detected in 8 of 17 normal and 12 of 15 HIV-positive subjects. RNA for VZV gene 4 was detected in 2 of 13 normal and 4 of 9 HIV-positive subjects, and RNA for gene 18 was detected in 4 of 15 normal and 5 of 15 HIV-positive subjects. By contrast, RNAs for VZV genes 28, 40, and 61 were rarely or never detected. In addition, immunocytochemical analysis detected the presence of VZV gene 63-encoded protein in five normal and four HIV-positive subjects. VZV RNA was also analyzed in explanted fresh human TG and dorsal root ganglia from five normal human subjects over a period of up to 11 days in culture. We found a very different pattern of gene expression in these explants, with transcripts for VZV genes 18, 28, 29, 40, and 63 all frequently detected, presumably as a result of viral reactivation. Taken together, these data provide further support for the notion of significant and restricted viral gene expression in VZV latency.

Analysis of individual human trigeminal ganglia for latent herpes simplex virus type 1 and varicella-zoster virus nucleic acids using real-time PCR

Herpes simplex virus type 1 (HSV-1) and varicella-zoster virus (VZV) establish latent infections in the peripheral nervous system following primary infection. During latency both virus genomes exhibit limited transcription, with the HSV-1 LATs and at least four VZV transcripts consistently detected in latently infected human ganglia. In this study we used real-time PCR quantitation to determine the viral DNA copy number in individual trigeminal ganglia (TG) from 17 subjects. The number of HSV-1 genomes was not significantly different between the left and right TG from the same individual and varied per subject from 42.9 to 677.9 copies per 100 ng of DNA. The number of VZV genomes was also not significantly different between left and right TG from the same individual and varied per subject from 37.0 to 3,560.5 copies per 100 ng of DNA. HSV-1 LAT transcripts were consistently detected in ganglia containing latent HSV-1 and varied in relative expression by >500-fold. Of the three VZV transcripts analyzed, only transcripts mapping to gene 63 were consistently detected in latently infected ganglia and varied in relative expression by >2,000-fold. Thus, it appears that, similar to LAT transcription in HSV-1 latently infected ganglia, VZV gene 63 transcription is a hallmark of VZV latency.

Varicella-zoster virus proteins in skin lesions: implications for a novel role of ORF29p in chickenpox

Skin biopsy samples from varicella-zoster virus (VZV)-infected patients examined by immunohistochemistry demonstrated VZV replication in nonepithelial cell types. ORF29p, a nonstructural nuclear protein, was found in nerves of two of six patients with chickenpox. In tissue culture, ORF29p was secreted by VZV-infected fibroblasts. Extracellular ORF29p can be taken up through endocytosis by human neurons, implying a novel role for this protein in pathogenesis.

Quantitation of latent varicella-zoster virus and herpes simplex virus genomes in human trigeminal ganglia

Using real-time fluorescence PCR, we quantitated the numbers of copies of latent varicella-zoster virus (VZV) and herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) genomes in 15 human trigeminal ganglia. Eight (53%) and 1 (7%) of 15 ganglia were PCR positive for HSV-1 or -2 glycoprotein G genes, with means of 2,902 +/- 1,082 (standard error of the mean) or 109 genomes/10(5) cells, respectively. Eleven of 14 (79%) to 13 of 15 (87%) of the ganglia were PCR positive for VZV gene 29, 31, or 62. Pooling of the results for the three VZV genes yielded a mean of 258 +/- 38 genomes/10(5) ganglion cells. These levels of latent viral genome loads have implications for virus distribution in and reactivation from human sensory ganglia.

Chronic verrucous varicella zoster virus skin lesions: clinical, histological, molecular and therapeutic aspects

The outbreak of HIV infection introduced a new phenomenon in varicella zoster virus (VZV) pathology, namely the long-standing wart-like skin lesions that are frequently associated with resistance to thymidine kinase (TK)-dependent antiviral agents. This paper reviews the clinical, histological, and molecular aspects and the therapeutic management of these verrucous lesions. The majority of lesions are characterized by chronically evolving, unique or multiple wart-like cutaneous lesions. The main histopathological features include hyperkeratosis, verruciform acanthosis and VZV-induced cytopathic changes with scant or absent cytolysis of infected keratinocytes. The mechanism that establishes the chronic nature of the lesions appears to be associated with a particular pattern of VZV gene expression exhibiting reduced or nondetectable gE and gB synthesis. Drug resistance to TK-dependent antiviral agents is a result of nonfunctional or deficient viral TK. This necessitates alternative therapeutic management using antiviral agents that target the viral DNA polymerase.

Localization of varicella-zoster virus gene 21 protein in virus-infected cells in culture

Although four varicella-zoster virus (VZV) genes have been shown to be transcribed in latently infected human ganglia, their role in the development and maintenance of latency is unknown. To study these VZV transcripts, we decided first to localize their expression products in productively infected cells. We began with VZV gene 21, whose open reading frame (ORF) is 3,113 bp. We cloned the 5' and 3' ends and the predicted antigenic segments of the ORF as 1292-, 1280-, and 880-bp DNA fragments, respectively, into the prokaryotic expression vector pGEX-2T. The three VZV 21 ORFs were expressed as approximately 75-, 73-, and 59-kDa glutathione S-transferase fusion proteins in Escherichia coli. To prepare polyclonal antibodies that would recognize all potential epitopes on the VZV gene 21 protein, rabbits were inoculated with a mixture of the three fusion proteins, and antisera were obtained and affinity purified. Immunohistochemical and immunoelectron microscopic analyses using these antibodies revealed VZV ORF 21 protein in both the nucleus and cytoplasm of VZV-infected cells. When these antibodies were applied to purified VZV nucleocapsids, intense staining was seen in their central cores.

Aberrant intracellular localization of Varicella-Zoster virus regulatory proteins during latency

Varicella-Zoster virus (VZV) is a herpesvirus that becomes latent in sensory neurons after primary infection (chickenpox) and subsequently may reactivate to cause zoster. The mechanism by which this virus maintains latency, and the factors involved, are poorly understood. Here we demonstrate, by immunohistochemical analysis of ganglia obtained at autopsy from seropositive patients without clinical symptoms of VZV infection that viral regulatory proteins are present in latently infected neurons. These proteins, which localize to the nucleus of cells during lytic infection, predominantly are detected in the cytoplasm of latently infected neurons. The restriction of regulatory proteins from the nucleus of latently infected neurons might interrupt the cascade of virus gene expression that leads to a productive infection. Our findings raise the possibility that VZV has developed a novel mechanism for maintenance of latency that contrasts with the transcriptional repression that is associated with latency of herpes simplex virus, the prototypic alpha herpesvirus.

Latent varicella-zoster virus is located predominantly in neurons in human trigeminal ganglia

Varicella-zoster virus (VZV) is a human herpesvirus that causes varicella (chicken pox) as a primary infection and, after a variable period of latency in trigeminal and dorsal root ganglia, reactivates to cause herpes zoster (shingles). Both of these conditions may be followed by a variety of neurological complications, especially in immunocompromised individuals such as those with human immunodeficiency virus (HIV) infection. There have been a number of conflicting reports regarding the cellular location of latent VZV within human ganglia. To address this controversy we examined fixed wax-embedded trigeminal ganglia from 30 individuals obtained at autopsy, including 11 with HIV infection, 2 neonates, and 17 immunocompetent individuals, for the presence of latent VZV. Polymerase chain reaction (PCR), in situ hybridization, and PCR in situ amplification techniques with oligonucleotide probes and primer sequences to VZV genes 18, 21, 29, and 63 were used. VZV DNA in ganglia was detected in 15 individuals by using PCR alone, and in 12 individuals (6 normal non-HIV and 6 positive HIV individuals, but not neonatal ganglia) by using PCR in situ amplification. When in situ hybridization alone was used, 5 HIV-positive individuals and only 1 non-HIV individual showed VZV nucleic acid signals in ganglia. In all of the VZV-positive ganglia examined, VZV nucleic acid was detected in neuronal nuclei. Only occasional nonneuronal cells contained VZV DNA. We conclude from these studies that the neuron is the predominant site of latent VZV in human trigeminal ganglia.

Identification of simian varicella virus homologues of varicella zoster virus genes

Clinical, pathologic, immunologic and virologic features of simian varicella virus (SVV) infection in primates resemble human varicella-zoster virus (VZV) infection. Further, the SVV and VZV genomes are similar in size and structure, show striking homology in their configuration and DNA sequences, and encode antigenically related polypeptides. Although the entire VZV genome is present during latency in human ganglia, transcription is limited. VZV genes 21, 29, 62 and 63 are transcribed during latency, while genes 4, 10, 40, 51 and 61 are not transcribed. The entire VZV genome has been sequenced, but the SVV genome has not. Thus, to analyze SVV genes transcribed during latency, we have begun to identify SVV homologues of the above VZV genes. We used nick-translated [32p]-labeled-VZV open reading frame (ORF)-specific probes to screen Southern blots containing EcoRI-digested SVV genomic DNA and recombinant clones of SVV EcoRI and BamHI DNA fragments spanning approximately 97% of the virus genome. We showed that SVV homologues of VZV ORFs 4, 10, 29, 40, 51 and 61 mapped to SVV DNA fragments EcoRI I, A, N, BamHI E, EcoRI D and E, respectively. We also confirmed earlier reports that SVV homologues of VZV genes 21 and 63 mapped to SVV EcoRI DNA fragments H and C, respectively. Viral genes on the SVV and VZV genomes seem to be collinear.