Studies of human papovavirus tumor antigen in experimental and human cerebral neoplasms

Association of SV40 with human tumours

SV40 was discovered as a contaminant of poliovirus vaccines that were inadvertently administered to millions of people in Europe and the United States between 1955 and 1963. Shortly afterwards, SV40 was proven to be oncogenic in rodents and capable of transforming human and animal cells in vitro. The possibility that SV40 might cause tumours in humans thus became a subject of scientific and public interest and scrutiny. However, largely due to a lack of significant epidemiological evidence, interest in assessing SV40's potential carcinogenic role in humans diminished. Recently, many laboratories have reported the presence of SV40-like DNA in a high proportion of human mesotheliomas, ependymomas and osteosarcoma (the three main types of tumours caused by virus in hamsters), renewing the question whether SV40 might be a human tumour virus. Molecular data from these studies are reviewed to re-evaluate the potential role of SV40 as a human carcinogen.

Search for virus nucleic acid sequences in postmortem human brain tissue using in situ hybridization technology with cloned probes: some solutions and results on progressive multifocal leukoencephalopathy and subacute sclerosing panencephalitis tissue

In order to obtain a useful and readily applicable in situ hybridization (ISH) protocol for progressive central nervous system (CNS) diseases of unknown etiology that are possibly due to persistent viral infection, known and well described diseases were studied, namely, progressive multifocal leukoencephalopathy (PML) and subacute sclerosing panencephalitis (SSPE). The procedures described were validated by confirming results obtained by other investigators using histology, immunocytochemistry, electron microscopy, and ISH. A number of frequently encountered problems of tissue preparation are addressed as well as techniques to reduce autoradiography exposure times. A multi-staged specific, sensitive, reliable, and valid procedure for detection of viral genomes, mRNA and proteins is approached. Formalin-fixed and paraffin-embedded (FFPE) brain material from six patients who died with PML and one patient who died from SSPE were studied using ISH with a tritium-labeled cloned JC virus DNA probe and a measles-cloned nucleocapsid (NC) gene cDNA probe, respectively. This report constitutes a methodological framework as well as a detailed neuropathological analysis of identified brain cell populations within which in situ hybridization was detected. In early PML lesions, swollen nuclei or oligodendrocytes were the predominant cells labeled, whereas older lesions revealed increased numbers of reactive and bizarre hypertrophic astrocytes hybridized at the outer periphery of the demyelinated lesions. The hybridization varied greatly in intensity in different cells. Intense hybridization was noted very rarely in microglial cells, including rod cells and rarely in venular pericytes, intravascular mononuclear cells, or in vascular endothelial cells. These results, considered together with previous findings, indicate that in PML the viral infection runs different courses in the various cells: in astrocytes the viral genome persists for a long time inducing pathological changes in some cells. In oligodendrocytes the infection rapidly lyses the cells. There was a good correlation between chromatic changes observable in routinely stained sections and virus presence. In addition, in situ hybridization using a measles-NP-cloned probe in white matter from FFPE SSPE brain is presented confirming earlier results in SSPE cryopreserved brain.

Immunoenzymatic labelling of JC papovavirus T antigen in brains of patients with progressive multifocal leukoencephalopathy

Formalin-fixed, paraffin-embedded autopsy sections of brains from two patients with progressive multifocal leukoencephalopathy (PML) were stained by peroxidase-antiperoxidase methods for human papovavirus T antigen, a nonstructural protein expressed in cells lytically infected or transformed by JC, BK, and SV40 viruses. Adjacent sections were stained for papovavirus common structural antigen, a component of JC, BK, and SV40 virions which is synthesized in productively infected but not transformed cells. Intense immunoperoxidase labelling specific for T antigen was detected in large numbers of oligodendrocytes at the edges of demyelinated areas and in occasional oligodendrocytes within otherwise normal brain. Occasional morphologically normal astrocytic cells exhibited similar specific staining, but only rate atypical astrocytic cells contained detectable amounts of T antigen. Examination of adjacent sections stained with antisera to common structural antigen revealed an identical pattern of immunoenzymatic labelling, indicating that most of the cells expressing T antigen were also expressing viral structural proteins. The present study demonstrates that T antigen can be identified by immunoperoxidase methods in routinely processed autopsy material from cases of PML, but that detectable amounts of antigen are found almost exclusively in cells undergoing lytic infection.

Papovavirus-related RNA sequences in human neurogenic tumours

Thirty-two human brain tumours were investigated for the presence of papovavirus-related RNA sequences. Radiolabelled viral DNAs isolated from SV40, BKV, HDV, and BPV were hybridized in-situ on to tumour kryostat sections under conditions that detect complementary RNA. SV40-related RNA was detectable in 34% of all tumours tested but was not found in normal human brain tissue. SV40-positive tumours included 1/1 angiofibroma, 1/4 astrocytomas, 2/4 metastatic brain tumours, 1/1 melanoma, 3/7 meningiomas, 2/4 neurinomas, 1/2 oligodendrogliomas. Bovine papilloma virus-, BKV-, and HDV-related RNAs were absent from all tissues tested. The presence of SV40-related nucleic acids in a large number of human neurogenic tumours may reflect a viral involvement in the etiology of these tumours.

Brain tumors in owl monkeys inoculated with a human polyomavirus (JC virus)

Owl monkeys were inoculated intracerebrally, subcutaneously, and intravenously with JC, BK, or SV40 virus. Two of four adult owl monkeys inoculated with JC virus, a human polyomavirus, developed brain tumors at 16 and 25 months after inoculation, respectively. A grade 3 to grade 4 astrocytoma (resembling a human glioblastoma multiforme) was found in the left cerebral hemisphere and brainstem of one monkey. The second monkey developed a malignant tumor in the left cerebral hemisphere containing both glial and neuronal cell types. Impression smears prepared from unfixed tissue of this tumor showed cells that contained polyomavirus T antigen. Virion antigens were not detected. Tumor cells cultured in vitro also contained T antigen but were negative for virion antigen. Infectious virus was not isolated from extracts of this tumor.

Immunocytochemical evidence of SV 40-related T antigen in two human brain tumours of ependymal origin

A series of thirty-time human brain tumours has been screened for the presence or absence of SV 40-related T antigen by the direct and indirect immunoperoxidase techniques. Two tumours (an ependymoma and a choroid plexus papilloma) of ependymal origin revealed markedly positive nuclear staining for T antigen both in in vivo and in vitro. The possible viral etiology of these human brain tumours is discussed in relation to recent human papovavirus isolates.

Failure to demonstrate papovavirus tumor antigen in human cerebral neoplasms

Cell cultures derived from 80 brain tumors failed to show the intranuclear tumor (T) antigen common to cells transformed by simian virus 40 (SV40) or BK or JC viruses.

Screening of human brain tumors for SV40-related T antigen

A series of 39 human brain tumors has been screened for the presence or absence of SV40-related T antigen by the direct and indirect immunoperoxidase methods. Two tumors of ependymal origin (malignant ependymoma, choroid plexus papilloma) revealed markedly positive nuclear staining for T antigen both in vivo and in vitro. The relationship of these tumors to their experimental counterparts inducible by recent human papovavirus isolates is discussed.

Slow Infections of the Central Nervous System

This review describes the recent advances in slow infections of the nervous system emphasizing the pathogenetic aspects of these diseases. A theoretical model for the pathogenesis of subacute sclerosing panencephalitis (SSPE) is proposed, illustrating the factors that may affect host response to the measles virus and allow it to persist and produce the panencephalitis. The isolation of an oncogenic virus from progressive multifocal leukoencephalopathy (PML) has implications in the consideration of a viral etiology for some brain tumors. The agent responsible for the transmissibility of kuru and Creutzfeldt-Jakob disease (CJD) remains uncharacterized despite recent interest in viroids and abnormalities in replication of cell membranes. The epidemiological data on multiple sclerosis suggests an exposure to an infectious agent at an early age of life modified by the host response. No specific agent has been consistently associated with multiple sclerosis. Amyotrophic lateral sclerosis (ALS), Parkinson’s disease, Mollare’s meningitis and Behcet’s disease are other examples where a virus is suspect but unproven. The ability of viruses to persist in the host for months to years has linked many chronic neurologic diseases to an infectious agent, enlarging the spectrum of disease caused by viruses.