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Biomedical subjects

D L Walker

Publications and source records attributed to D L Walker.

At least 73 records · Page 4Linked to original sources
PubMed1986

Construction and characterization of hybrid polyomavirus genomes.

Several studies have suggested that certain unique features of the JC virus (JCV) regulatory region are responsible for the restricted lytic and transforming activities of this virus in vitro. To pursue this possibility, we have constructed hybrid polyomavirus genomes by exchanging the regulatory sequences of JCV, BK virus (BKV), and simian virus 40 (SV40). The host range of JCV was not expanded by the substitution of the BKV or SV40 regulatory signals; such hybrids were nonviable even in primary human fetal glial cells, the sole permissive cell for JCV. However, chimeric DNAs containing JCV regulatory sequences and BKV- or SV40-coding sequences were lytically active, indicating that the BKV and SV40 T proteins were capable of effectively interacting with the JCV replication and transcription signals to yield infectious hybrid viruses. Although JCV regulatory sequences and coding sequences both contributed to the restricted lytic activity of this virus, it appears that the latter sequences, most likely hose encoding the T protein, have a greater influence on this behavior.

Antigens, Viral, Tumor↗
PubMed1984

Brain tumors of owl monkeys inoculated with JC virus contain the JC virus genome.

The DNA from astrocytomas that developed in adult owl monkeys 16 to 36 months after intracranial inoculation with JC virus (JCV) was examined for the presence of the JCV genome by hybridization to cloned JCV DNA. The JCV genome was found to be integrated into the cellular DNA in all tumors examined. There was no JCV DNA in normal, uninvolved brain tissue from the same animals. Integration of the genome occurred at a limited number of sites in the cellular DNAs, indicating a clonal origin for the tumors, but none of the tumors had integration sites in common. In all but one of the tumors, there was tandem, head-to-tail integration of two or more copies of the JC genome. In a tumor which had only one integration site and could be analyzed more extensively, there appeared to be a complete copy of the JCV genome present, although deletions of small portions of the genome would not have been detected.

Animals↗
PubMed1984

Progressive multifocal leukoencephalopathy.

PML is a progressive opportunistic infection of the CNS caused by a commonly occurring virus that may become manifest in the context of reduced host resistance in persons of any age. The authors review the disease and its causes, including a discussion of treatment attempts and differential diagnoses.

Adolescent↗
PubMed1983

Tubulo-interstitial nephritis associated with polyomavirus (BK type) infection.

We studied viral injury to the kidney in a six-year-old boy with hyperimmunoglobulin M immunodeficiency who presented with irreversible acute renal failure and eventually died after five months of dialysis. Renal biopsy at the time of his presentation revealed a predominantly tubulo-interstitial process with numerous viral inclusions that were identified as polyomavirus. Urine cultures showed a massive viruria with BK-type, polyomavirus. The kidney disease was end stage, with persistence of BK virus identified by morphologic techniques and by culture. DNA hybridization analysis showed virus in low concentration in the lymph nodes, spleen, and lungs. The marked viruria, the high concentration of BK virus, and the extensive distribution of viral antigen throughout the kidney all suggest that infection with BK virus was the basis of the severe renal parenchymal injury.

Animals↗
PubMed1983

Distribution of nonintegrated DNA from JC papovavirus in organs of patients with progressive multifocal leukoencephalopathy.

Tissues from 10 patients with progressive multifocal leukoencephalopathy (PML) and 14 patients without PML who were serologically positive for JC papovavirus were examined by molecular hybridization for human polyomavirus DNA sequences. Although viral proteins were not identified by fluorescent antibody methods, viral DNA was found in the kidneys of seven of nine patients with PML by hybridization, at 0.2-10 viral genome copies per cell genome equivalent, compared with 0.6-4 X 10(3) copies per cell in diseased areas of the brain. Examination of viral DNA from brains and kidneys of patients with PML by blot hybridization yielded no evidence of integration into the host cell genome. In three of the patients with PML, viral DNA was also found in liver, lung, lymph node, and spleen. Two of these patients, with widely disseminated JC virus, were children. In tissues from patients without PML, no evidence of JC virus infection was found, but BK papovavirus DNA was detected in two of 14 kidneys tested.

Adolescent↗
PubMed1983

Characterization of tissue culture-induced heterogeneity in DNAs of independent isolates of JC virus.

After several serial passages at low multiplicities of infection in primary human foetal glial cells at 37 degrees C, the DNA of prototype (MAD-1) JC virus and that of MAD-2 and MAD-3 are typically heterogeneous in size, but DNAs of MAD-4 and MAD-6 are relatively homogeneous. A similar dichotomy was observed in the DNAs of six isolates propagated more recently in glial cultures at 39 degrees C under similar conditions of brief passage in vitro at low multiplicities of infection: the DNAs of two (MAD-9 and -10) were heterogeneous, but the DNAs of four others (MAD-8, -11, -12 and -14) were homogeneous. Therefore, the propensity of the viral genome to sustain deletions was an intrinsic property of each isolate. However, actual induction and maintenance of the presumably defective DNAs was influenced by the relative proportions of permissive spongioblasts and semi-permissive astrocytes in the glial cultures and by the multiplicity of infection. Deletions in MAD-1 DNA were confined to the presumptive early region and spanned the BamHI cleavage site (map position 0.505). The heterogeneity was more complex in the DNAs of MAD-2 and MAD-3, but again most of the deletions, which ranged up to 12% of full-length DNA, spanned the BamHI site. We propose that the differential susceptibility to deletion among isolates is a consequence of natural genetic variation in JC virus.

Chromosome Deletion↗
PubMed1983

Comparison of infectious JC virus DNAs cloned from human brain.

We cloned JC virus DNA obtained directly from brain tissue of 10 cases of progressive multifocal leukoencephalopathy and compared DNAs by restriction endonuclease mapping. Before cloning, each DNA preparation was homogeneous with respect to restriction patterns, but with the cloned DNAs we found variability in three regions of the genome among DNAs from different cases. There was a region of hypervariability between 0.67 and 0.725 map units; no two DNAs were exactly alike in this region. We determined that the origin of DNA replication also was in this region at 0.69 +/- 0.02 map units. In 4 of the 10 DNAs examined there was a deletion of approximately 75 base pairs between 0.14 and 0.235 map units, the region presumed to contain the codons for the C-terminal ends of the structural protein Vpl and for T antigen. JC virus DNA from these same four cases had an additional HincII-HpaI site at 0.895 map units in the presumptive Vp3 and Vp2 coding regions. Overall, no two JC virus genomes were identical although all were from fatal central nervous system infections and were infectious in vitro. Our restriction patterns suggest that there are two subtypes of JC virus circulating in the population.

Base Sequence↗
PubMed1983

Virologic and serologic studies of progressive multifocal leukoencephalopathy.

The human polyomavirus JCV has been associated with diseased brain tissue from 54 cases of PML. The disease occurred in persons of all ages--the youngest being 5 years old--whose immune mechanisms were depressed for any of a variety of reasons. In six patients the disease ceased progressing and they stabilized or improved. The brains of two of these, who died months or years later, were found to be free of active PML at autopsy. Sera from 21 patients had HAI antibodies against JCV, but none had antibodies against T or the common internal antigens, and only one had IgM antibodies detectable by immunofluorescent staining. Nine CSF were devoid of JCV-related antibodies except for one which gave an HAI titer of 8. Virus has been isolated from 15 PML brains, and preliminary studies indicate that one isolate, while clearly of JCV type, is serologically distinguishable from prototype Mad 1 JCV.

Adolescent↗
PubMed1983

New world primates as a model of viral-induced astrocytomas.

Owl and squirrel monkeys are susceptible to the oncogenic effects of JCV. These species of New World monkeys can be safely inoculated intracerebrally. Care must be taken with owl monkeys since they have an inherited clotting abnormality. Incubation times for the development of tumors range from 14 to 30 months. Anorexia was the first clinical sign of tumor development. The clinical course is rapid with death within two to three days. This model provides a means for studying diagnostic, virological, immunological and therapeutic techniques which are applicable to human patients with astrocytomas.

Animals↗
PubMed1983

Viral-induced astrocytomas in squirrel monkeys.

Saimiri sciureus, the squirrel monkey, is susceptible to the oncogenic effects of JCV following intracerebral inoculation. As in owl monkeys, tumor development follows an incubation time of 14 to 30 months. Four of six virus-inoculated monkeys developed cerebral tumors, three of which were astrocytomas grade 4 and the remaining tumor was a poorly differentiated astrocytoma. All tumors showed high cellularity, mitotic figures, and cellular pleomorphism. In the astrocytoma grade 4, neovascularization was a prominent feature. The blood vessels in the poorly differentiated astrocytoma appeared normal. Multinucleated giant cells were present in all four astrocytomas. Antemortem hemorrhage was seen in one astrocytoma grade 4. Other tumor types were not seen. The occurrence of astrocytomas in a second species of New World monkeys confirms the oncogenicity of JCV for nonhuman primates.

Animals↗
PubMed1983

Glial and divergent cells in primate central nervous system tumors induced by JC virus isolated from human progressive multifocal leukoencephalopathy (PML).

Immunofluorescent stains for fibronectin (FN) and glial fibrillary acidic protein (GFAP) were used in conjunction with routine histologic stains to study tumors induced in squirrel and owl monkeys by JC virus from progressive multifocal leukoencephalopathy (PML). Three varieties of glioma were identified. The first and most common variety was a neoplasm similar to grade 4 astrocytoma in humans. The second had thin, normal-appearing FN-positive vessel walls and a vastly expanded neuroectodermal parenchyma which could not be characterized by routine histologic stains. Anti-GFAP revealed the glial nature of the parenchyma. Isolating glial parenchymal cells from divergent FN-positive cells has become important to neurooncology. This type of tumor may be of particular interest for such isolations due to its high ratio of glial cells to divergent cells. The third variety was not a homogeneous neoplasm. It occurred as focal regions within tumors of the first type, and consisted of giant cells with huge nuclei. These cells resemble the cells of a human giant cell glioblastoma and bear a slight similarity to the bizarre glial cells seen in PML. The rare human giant cell glioblastoma might have an association with JC virus or with PML.

Animals↗
PubMed1983

Neuroradiological studies of JCV-induced astrocytomas in nonhuman primates.

Astrocytomas in nonhuman primates following JC virus inoculation provides a model which can be used to evaluate diagnostic and therapeutic techniques used in humans. The CT scan appearance of astrocytomas in nonhuman primates closely resembles that seen in humans. Our studies have shown that tumors may be detected in asymptomatic monkeys. Serial scans have shown astrocytomas to grow rapidly with breakdown of the blood-brain barrier. CT scanning has demonstrated the presence of tumor which was undetectable by gross examination at necropsy but confirmed by light microscopy. Studies are in progress to further define the radiological appearance of gliomas, to evaluate contrast-tagged anti-tumor antibodies as a diagnostic tool in evaluating gliomas by computerized tomography, and to evaluate metabolic parameters of actrocytomas by positron emission tomography.

Animals↗
PubMed1983

The detection of JC viral genome in owl monkey tumors.

The JC viral genome is integrated into the cellular DNA of brain tumors from owl monkeys inoculated intracranially with JC virus 16-36 months prior to the development of the tumors. Normal brain tissue of the animals did not contain the viral genome. For at least two tumors, restriction endonuclease analysis of the tumor DNA indicates that there is a complete copy of the viral genome present. Integration of the genome in all but one of the tumors was at only one or only a limited number of sites, indicating a clonal origin for the tumors. In all but one of the tumors, there was tandem, head-to-tail integration of two or more copies of the JC genomes.

Animals↗
PubMed1983

Survey of human polyomavirus (JCV, BKV) infections in 139 patients with lung cancer, breast cancer, melanoma, or lymphoma.

In 139 patients with breast or lung carcinoma, malignant melanoma, and Hodgkin's or non-Hodgkin's lymphoma, JC and BK virus serology (hemagglutination inhibition) and urinary polyomavirus excretion (cytology and immunofluorescence microscopy) were studied. Overall, 18 of 70 patients with paired sera (26%) had titer increases against JC or BK virus, and 11 of 114 patients (10%) had evidence for urinary excretion. The infection rate was highest in patients with Hodgkin's or non-Hodgkin's lymphoma (approximately 40%). Serum HAI antibody titers against JC and BK viruses appeared similar to age-matched controls in each patient group--with the exception of decreased BK titers at diagnosis in patients with resected malignant melanoma and increased JC virus antibody titers at diagnosis in patients with poor-prognosis non-Hodgkin's lymphoma (IC-2). The biologic significance of these observations remains to be determined. Initial antibody titers against JC or BK virus were not of prognostic value for subsequent survival in any of the tested patient groups. Both nonspecific immunotherapy and aggressive, multidrug chemotherapy had surprisingly little effect on serum HAI titers to JC or BK virus. Patients with poor-prognosis non-Hodgkin's lymphoma appear especially suitable for further investigation of JC and BK virus infections. Study of nonbrain, nonurinary-tract tissues may disclose other parenchymal sites of polyomavirus replication in these patients.

Adolescent↗
PubMed1983

Naturally occurring and passage-induced variation in the genome of JC virus.

We have examined both the naturally occurring and passage-induced variation in the genome of the human polyomavirus, JCV. JCV DNA was extracted directly from diseased brain tissue of ten cases of progressive multifocal leukoencephalopathy (PML) and the DNA population from any one case was homogeneous with respect to length and restriction endonuclease cleavage patterns. However, a comparison of cloned JCV DNAs revealed that the viral DNAs derived from different cases of PML were not identical. We identified a hypervariable region near the origin of DNA replication, and we demonstrated that there are two genetically distinguishable subtypes of the virus. After growth in vitro, the DNA from certain isolates of JCV became heterogeneous in size. Deletions of up to 12% of the genome occurred after as few a three low multiplicity passages in human glial cells. Most of the deletions mapped within the region presumed to code for T antigen. In addition, we examined the physical properties of JCV from brain and, as expected, they were typical of the polyomavirus genus.

Brain↗