Latency and reactivation of varicella zoster virus infections.

Varicella zoster virus (VZV) is the causative agent of chickenpox (varicella) and shingles (zoster). The study of latency and reactivation has been hampered by the fact that the virus is strictly human and grows to low titres in tissue culture. Molecular biology techniques have opened a new era of VZV research. The site of VZV latency was determined to be sensory ganglia by Southern blotting and later by PCR technology. It was also demonstrated that the entire virus genome is present in the latently infected ganglia and that VZV is latent in multiple ganglia along the entire human neuraxis. Since the amount of latent VZV per cell is very low, the question of which cell type is involved in VZV latency could not be conclusively settled by the use of traditional in situ hybridization studies. However, we have now demonstrated the presence of latent VZV DNA in neurons only, by using a more sensitive method which employs a combination of in situ PCR and in situ hybridization. The transcriptional activity of VZV during latency is still not completely clear. Ganglia are small and the total amount of latent VZV is low, therefore conventional methods to detect latent VZV have proved limited. Nevertheless, the detection of a latent transcript from the SalI C region of the virus was demonstrated by Southern hybridization of cDNA synthesized from RNA isolated from latently-infected ganglia. Further studies have localized this transcript to the open reading frame of VZV gene 21. The study of VZV latency and reactivation has, until now, been dependent on the investigation of post mortem human tissue. However, simian varicella virus seems to be the simian counterpart to human VZV. The 2 viruses exhibit DNA homology as well as similarities in clinical, virological, and immunological features. Further studies of VZV infections may open new and possibly unpredictable opportunities in varicella virus research.

Detection of latent varicella zoster virus DNA and human gene sequences in human trigeminal ganglia by in situ amplification combined with in situ hybridization.

Varicella zoster virus (VZV) establishes latency in sensory ganglia following primary infection (chickenpox) and may reactivate decades later to produce zoster (shingles). The presence of VZV DNA in latently infected ganglia has been demonstrated by Southern blot hybridization as well as by polymerase chain reaction of DNA extracted from latently infected ganglia. Conflicting results have been obtained by in situ hybridization studies to determine the cell type in the ganglia harboring the latent VZV. To address this controversy we have utilized a more sensitive method than the previous studies. We have applied the technique of polymerase chain reaction to sections of ganglia from latently infected individuals and combined this with in situ hybridization to detect the amplified product. Primers specific for VZV were used to amplify VZV DNA in latently infected human trigeminal ganglia and demonstrated the presence of VZV DNA in neurons only. Sections from human kidney and ganglia from neonates as well as monkey ganglia served as controls and did not show amplification of VZV sequences. Amplification using primers for human genes, alpha tubulin and the oncogene Bcl-2, demonstrated the presence of these sequences in nearly all cells in the human tissues while only weak signals were seen in the monkey tissue. This is the first report where in situ amplification has been utilized to detect latent VZV in human ganglia.

Restricted transcription of varicella-zoster virus in latently infected human trigeminal and thoracic ganglia.

Normal human trigeminal and thoracic ganglia latently infected with varicella-zoster virus (VZV) were identified by polymerase chain reaction (PCR). Total RNA was extracted from these ganglia and treated with DNase until ganglionic RNA was free of VZV DNA as determined by PCR. Radiolabeled cDNA synthesized by priming with random oligonucleotides was hybridized to Southern blots containing recombinant clones that spanned greater than 95% of the VZV genome. The single region of the VZV genome detected was the 12.5-kb SalI C fragment located in the unique long segment of the viral genome. Two additional regions of the VZV genome, EcoRI G and SalI B, were detected in RNA from adult dorsal root ganglia and infant nervous system tissue.

Varicella-zoster virus reactivation without rash.

Reactivation of varicella-zoster virus (VZV) leads to localized zoster (shingles), a syndrome characterized by pain and a vesicular rash. Rarely, patients experience radicular pain without zosteriform rash, cases that have been regarded as zoster sine herpete (zoster without rash). Virologic evidence for zoster sine herpete is sparse. However, VZV can produce other neurologic and visceral diseases in the absence of rash or radicular pain. The clinical and virologic features of zoster sine herpete and other disorders produced by VZV without rash are reviewed. Evidence is also presented for the detection of VZV DNA in human blood mononuclear cells of elderly individuals in the absence of skin lesions or other VZV-associated neurologic or systemic disease.

Acute simian varicella infection. Clinical, laboratory, pathologic, and virologic features.

Five African green monkeys inoculated intratracheally with 7.5 x 10(3) to 1.4 x 10(5) plaque-forming units of simian varicella virus (SVV) were subjected to clinical, laboratory, pathologic, and virologic analyses to study the pathogenesis of acute varicella. All animals developed viremia and rash and were sacrificed 8 to 11 days post-infection. No serum was available for postmortem serologic studies. Examination of multiple organs for pathologic changes and for SVV-specific antigen and nucleic acid revealed inflammation, hemorrhagic necrosis, and intranuclear Cowdry A inclusions in liver, lung, lymph node, and spleen; mild inflammation without necrosis in adrenal gland, kidney, and bone marrow, and SVV-specific antigen and nucleic acids in all viscera examined. No pathologic changes, SVV antigen or nucleic acids were detected in the spinal cord or in the brain from any of the monkeys. Ganglia revealed mild inflammation but no necrosis, and intranuclear inclusion bodies in non-neuronal cells of one trigeminal ganglion; SVV antigen and nucleic acids were detected in both non-neuronal and neuronal cells in ganglia. The pathologic and virologic findings in viscera are consistent with those described in viscera of humans with disseminated zoster, but the mild inflammatory changes in ganglia during acute simian varicella infection contrast with the extensive hemorrhagic necrosis and intranuclear inclusion bodies seen in human ganglia after disseminated varicella or zoster. Nevertheless, these studies show that ganglia become infected with varicella virus during primary infection, although the route of primary ganglionic infection remains to be determined, and indicate the possible usefulness of the SVV model to study varicella pathogenesis in humans.

Prevalence and distribution of latent simian varicella virus DNA in monkey ganglia.

We used polymerase chain reaction to analyze the prevalence and distribution of latent simian varicella virus (SVV) in ganglionic and nonganglionic tissues from nine African green monkeys experimentally infected with SVV. Primers specific for three different regions of the SVV genome were used for amplification. SVV DNA sequences were detected in trigeminal ganglia from seven of nine monkeys and in thoracic ganglia from seven of nine monkeys. Analysis of DNA from nonneuronal tissues of three monkeys and from adrenal glands of nine monkeys revealed the presence of SVV-specific sequences in the adrenal gland of one monkey. The results indicate that, like human varicella, SVV becomes latent primarily in ganglia at multiple levels of the neuraxis, and more than one region of the SVV genome is present in latently infected ganglia. SVV latency in primates may be a useful model for varicella latency in humans.

Localization of herpes simplex virus and varicella zoster virus DNA in human ganglia.

Human dorsal root ganglia from 14 randomly autopsied adults and 1 infant (all seropositive for both herpes simplex virus [HSV] and varicella zoster virus [VZV]) were examined for latent HSV-1 and VZV DNA by polymerase chain reaction. Thoracic ganglionic DNA from all subjects and trigeminal ganglionic DNA from 11 adults were analyzed. HSV-1 DNA was detected in trigeminal ganglia from 8 of 11 (73%) adults and in thoracic ganglia from 2 of 14 (14%) adults. VZV DNA was detected in trigeminal ganglia from 10 of 11 (91%) adults and in thoracic ganglia from 12 of 14 (86%) adults. None of the DNA samples were positive with primers specific for HSV-2. These findings indicate the presence of latent HSV-1 and VZV DNA in trigeminal ganglia and latent VZV DNA in thoracic ganglia of most seropositive adults. Furthermore, although HSV-1 latency most commonly develops in trigeminal ganglia, we also show for the first time the presence of HSV-1 latency in thoracic ganglia. Finally, both viruses can become latent in the same trigeminal ganglion.

Peripheral blood mononuclear cells of the elderly contain varicella-zoster virus DNA.

Peripheral blood mononuclear cells (PBMC) from humans of different ages were analyzed for DNA sequences specific for varicella-zoster virus (VZV) genes 29 and 62 by polymerase chain reaction (PCR). Neither VZV gene was detected in DNA from umbilical cord blood PBMC of 10 infants or from blood PBMC of two 3-year-old children. In 22 humans less than 60 years old, gene 29 was not detected, and gene 62 was detected in only one subject. In 33 humans greater than 60 years old, including patients with postherpetic neuralgia, PBMC from 4 subjects contained gene 29, 4 contained gene 62, and 1 contained both genes. The presence of VZV DNA correlated significantly with age (P less than .05, chi 2 and logistic regression analysis), but not with gender or postherpetic neuralgia.

Increased plasma hypoxanthine values in humans during exposure to simulated altitude of 7,620 meters (25,000 feet).

In this study we have determined the effect of severe and moderate hypoxemia on plasma hypoxanthine and lactate values. Hypoxemia was induced in healthy humans in a low pressure chamber. The test subjects breathed atmospheric air at barometric pressures of 279 mm Hg and 385 mm Hg, representing a simulated altitude of about 7,620 and 5,334 m (25,000 and 17,500 ft), respectively. Exposure to 279 mm Hg represents a severe hypoxemia and all subjects exposed to this simulated altitude for 2 min showed symptoms related to hypoxia. After this exposure, plasma hypoxanthine increased by an average of 2.4 times compared to preexposure values. Exposure to 385 mm Hg represents a moderate hypoxemia and the persons tested at this simulated altitude for 45 min showed no or minor symptoms related to hypoxia and there was no change in plasma hypoxanthine values. In contrast to the unchanged plasma hypoxanthine values there was a 50% increase in plasma lactate values after 30 min exposure. We conclude that plasma hypoxanthine is a reliable marker for severe cellular hypoxia in humans and that enhanced plasma hypoxanthine levels are a rapid response to cellular hypoxia.

Preherpetic neuralgia.

We have encountered six zoster patients whose pain preceded rash by 7 to more than 100 days. Pain was severe, burning, and radicular, and located both in dermatomes different from, as well as in, the area of eventual rash. Two patients ultimately developed disseminated zoster with neurologic complications, one of zoster paresis, and the other, a fatal zoster encephalitis; both had been taking long-term, low-dose steroids. A third case of preherpetic neuralgia developed in a patient with prior metastatic carcinoma, and another case in a patient with an earlier episode of brachial neuritis. The final two cases of preherpetic neuralgia developed in individuals with no underlying disease. An extended period of pain before the onset of zoster rash has gone largely unrecognized.

Fatal varicella-zoster virus meningoradiculitis without skin involvement.

A 77-year-old man with T-cell lymphoma developed an acute fatal meningoradiculitis of cranial nerve roots and cauda equina, pathologically and virologically confirmed to be caused by varicella-zoster virus. This is the first report of fatal varicella-zoster virus-induced neurological disease in the absence of skin lesions. Varicella-zoster virus should be included in the differential diagnosis of acute radiculoneuropathy in the immunocompromised patient, particularly because antiviral treatment for varicella-zoster virus exists.

Simian varicella virus DNA in dorsal root ganglia.

Clinical, pathological, immunological, and virological evidence suggests that simian varicella virus (SVV) infection of primates is the counterpart of varicella-zoster virus infection of humans. To determine whether these two viruses share similarities in their properties during latency, we analyzed ganglia and brain of an African green monkey experimentally infected with SVV for the presence of viral nucleic acid using the polymerase chain reaction technique. We detected SVV DNA in dorsal root ganglia but not in brain of this monkey, which demonstrated no apparent clinical signs of SVV infection. Our results suggest that SVV becomes latent in monkey ganglia and that latency can develop in the absence of clinical varicella (chickenpox). These studies provide an animal model system to study varicella virus latency.

Latent varicella-zoster viral DNA in human trigeminal and thoracic ganglia.

BACKGROUND: Some human herpesviruses become latent in dorsal-root ganglia. Primary infection with the varicella-zoster virus causes chickenpox, followed by latency, and subsequent reactivation leading to shingles (zoster), but the frequency and distribution of latent virus have not been established. METHODS: Using the polymerase chain reaction, we performed postmortem examinations of trigeminal and thoracic ganglia of 23 subjects 33 to 88 years old who had not recently had chickenpox or shingles to identify the presence of latent varicella-zoster viral DNA. Oligonucleotide primers representing the origin of replication of the varicella-zoster virus and varicella-zoster virus gene 29 were used for amplification. RESULTS: Among the 22 subjects seropositive for the antibody to the virus, both the viral origin-of-replication and gene-29 sequences were detected in 13 of 15 subjects (87 percent) in whom trigeminal ganglia were examined and in 9 of 17 (53 percent) in whom thoracic ganglia were examined. Viral DNA was not detected in brain or mononuclear cells from the seropositive subjects. None of three thoracic ganglia from the one seronegative subject contained varicella-zoster viral DNA. CONCLUSIONS: These findings indicate that after primary infection with varicella-zoster virus (varicella), the virus becomes latent in many ganglia--more often in the trigeminal ganglia than in any thoracic ganglion--and that more than one region of the viral genome is present during latency.