Duard L. Walker

Progressive multifocal leukoencephalopathy.

Progressive multifocal leukoencephalopathy (PML) is a human, virus-induced, subacute, fatal, demyelinating, neurodegenerative disease. PML reached epidemic proportions when an increasing proportion of the population was becoming immunosuppressed with the onset of the acquired immune deficiency syndrome (AIDS), which is caused by human immunodeficiency virus type 1 (HIV-1). PML is a unique demyelinating disease with distinctive pathology consisting of multiple foci of demyelination of varying size, from pinpoint lesions to areas of several centimeters. The lesions may occur anywhere but are usually in the cerebral hemispheres, less often in the cerebellum and brainstem, and rarely in the spinal cord. The significantly higher incidence of PML in AIDS is due to molecular interactions between HIV-1 and the JC virus (JCV), via the HIV-1–encoded trans-regulatory Tat protein, which are responsible for the activation of the JCV enhancer-promoter in the non-coding control region (NCCR) part of the JCV genome. PML was initially described in the context of immunosuppression caused by chemotherapy. With the development of HIV-1–induced immunosuppression, the prevalence of PML increased and further insights into the interaction between cellular transcription factors and the replication of JCV within central nervous system (CNS) and non-CNS cells were identified. PML occurring before the onset of AIDS and PML occurring in AIDS patients is similar in the lack of optic nerve involvement, together with the presence of visual field defects at presentation. Weakness and speech disturbances, especially dysarthria, were common presentations of PML in both groups of patients.

Human papovavirus (JC): induction of brain tumors in hamsters.

Eighty-three percent of hamsters inoculated at birth with JC virus, a human papovavirus isolated from brain tissue of a case of progressive multifocal leukoencephalopathy, developed malignant gliomas within 6 months. Three brain tumors have been serially transplanted as subcutaneous tumors. JC virus was isolated from five of seven tumors tested. Cells from four tumors were cultivated in vitro. These cells contained an intranuclear antigen with the characteristics of a T antigen, and this antigen was antigenically related to SV40 T antigen. Although virus was not recovered from extracts of serially cultured tumor cells, JC virus was rescued when one tumor cell line was fused with permissive cells.

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.

Progressive multifocal leukoencephalopathy (PML): In vitro cell‐mediated immune responses to mitogens and JC virus

cell-mediated immunity was studied by in vitro tests in seven patients with progressive multifocal leukoencephalopathy (PML). Lymphocyte proliferation in response to mitogenic stimulation was reduced to a variable degree in all patients, indicating a general impairment of cell-mediated immune responsiveness, although mitogen-induced production of the lymphokine leukocyte migration inhibitory factor (LIF) was normal in most cases. Cell-mediated immunity to JC virus (JCV) was assessed by LIF production in response to JCV antigen. In the six PML patients tested, LIF production with JCV antigen was absent despite the presence of antibody to JCV in serum. This contrasted with positive LIF production in seropositive normal individuals and patients with other diseases. These results provide the first in vitro evidence of a depressed cell-mediated immune response to JCV in patients with PML, and support the hypothesis that PML is accompanied by a selective marked deficiency in cellular response to this virus in association with a general depression of cell-mediated immunity of variable severity.

Site of Intracellular Antigen Production by Myxoviruses.

Summary The multiplication cycles of Sendai, mumps, and Newcastle disease viruses were compared with that of influenza A virus in regard to site of antigen production in the cell. Single-cycle infections were followed using fluorescent antibodies prepared from infection-convalescent immune sera shown to contain anti-S and anti-V antibodies. In cells infected with influenza A virus antigen was first detectable in the nucleus and became abundant there by the time antigen appeared in the cytoplasm. In cells infected with Sendai, mumps, or Newcastle disease viruses earliest detectable antigen was found as small granules scattered throughout the cytoplasm. Antigen granules increased in size and number to form large cytoplasmic aggregates and masses. Multiplication of Sendai, mumps, or Newcastle disease viruses did not include production of antigen in the nucleus detectable by fluorescent antibody at any stage of the cycle.

Age distribution of progressive multifocal leukoencephalopathy

ABSTRACT‐ The age distribution is given of 79 cases of progressive multifocal leukoencephalopathy confirmed as JC virus infection. The data are compared with a published age distribution of multiple sclerosis onset in Vestfold County, Norway, and with published data from Rochester, Minnesota of the age distribution of viral encephalitis. In contrast to viral encephalitis, 61% of which occurs in children under the age of 10, PML has been identified only once in this age group. PML, like MS, is a disease of adult onset, peaking in the sixth decade of life. The reason for this late onset of a CNS disease caused by a ubiquitous childhood infection is still uncertain, but it may be related to maturation of susceptible cells in the brain, as well as to declining immunity associated with chronic disease and age.

Factors Influencing Host-Virus Interactions. II. Alteration of Coxsackie Virus Infection in Adult Mice by Cold.

Summary 1. Exposure of adult mice infected with the Conn. 5 strain of Coxsackie virus to a cold environment resulted in an infection with a persisting viremia, high levels of virus in the liver, pathologic lesions in other organs as well as in the pancreas, and a uniformly fatal outcome. 2. A lethal infection was prevented by neutralization of the virus or passive immunization of adult mice with specific antiserum. 3. The LD50 for adult mice at 4°C was approximately ten times that for suckling mice at 25°C. 4. It was demonstrated that to initiate a fatal infection exposure to cold had to be continuous and begun within a few days after virus inoculation.

Plaque assays for myxoma and fibroma viruses and differentiation of the viruses by plaque form

Abstract It was shown that myxoma virus produced plaques on monolayers of rabbit kidney cells or rabbit heart fibroblasts and that fibroma virus produced visible foci of infection on monolayers of rabbit kidney cells. This allowed development of plaque-count assays for the two viruses. With each virus the numbers of plaques produced were linearly related to virus concentration, and plaque formation was inhibited by specific antiserum. The plaque assay for each virus was at least as sensitive as the intradermal assay in rabbits, and the plaque assay for myxoma virus was more sensitive than the pockcount assay on the CAM of the chicken embryo. The fibroma virus focus of infection on monolayers of rabbit kidney cells under agar consisted of a small pile of cells easily differentiated from the focus of damaged cells produced by myxoma virus.

Immunocytochemical search for JC papovavirus large T-antigen in multiple sclerosis brain tissue.

SummaryThe large T-antigens of papovaviruses JC (JCV) and BK share a C-terminal subsequence with myelin basic protein (MBP). Since this sequence functions as a phosphate acceptor site in MBP, expression of a competing T-antigen sequence in oligodendroglia might adversely affect their ability to post-translationally process MBP and thus to maintain myelin. We have used techniques which demonstrate JCV T-antigen in small oligodendroglial cells from progressive multifocal leukoencephalopathy tissue to search for a possible latent JCV infection expressing T-antigen in nine cases of multiple sclerosis (MS) and three normal brains. No cells expressing T-antigen were detected in plaque or periplaque regions of the MS brains or in control CNS tissue.

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.