Persistence of neurotropic JC virus DNA in hamster tissues six months after intracerebral inoculation.

Immunostaining and polymerase chain reaction (PCR) methods were used to examine tissues from 18 6-month-old hamsters intracerebrally inoculated with JC virus (JCV) as newborns. JCV DNA was detected in all hamster brains and urinary bladders, as well as in most kidney, adrenal gland and pancreas samples. While results from reverse transcription PCR (RNA PCR) and immunostaining suggest that T antigen transcription and protein expression were restricted to the brain, the DNA suggests that intracerebrally inoculated JCV enters the systemic circulation and latently infects organs in a tissue specific manner.

Neurovirulent simian immunodeficiency virus replicates productively in endothelial cells of the central nervous system in vivo and in vitro.

The perivascular location of human immunodeficiency virus-infected cells suggests that the virus enters the central nervous system (CNS) by traversing the blood-brain barrier (BBB). In this study, the simian immunodeficiency virus (SIV) macaque model was used to determine whether SIV infects CNS endothelial cells. SIV RNA was detected in capillary endothelial cells in brain sections from animals parenterally inoculated with a neurovirulent strain of SIV by double immunohistochemistry and in situ hybridization and by reverse transcriptase-in situ PCR. These in vivo observations were extended by examining whether SIV replicated productively in cultured macaque brain endothelial cells (MBEC). A neurovirulent strain, SIVmac239/17E-Br, replicated productively in MBEC as determined by the presence of viral cytopathic effect (syncytia), viral DNA by PCR, viral RNA by in situ hybridization, and viral antigen by immunohistochemistry and by the production of high titers of cell-free virus. Virus replication was confirmed by electron microscopy. In contrast, a nonneurovirulent strain, SIVmac239, did not infect MBEC. Infection of the endothelial cells was not blocked by soluble CD4. Thus, endothelial cells may provide a CD4-independent pathway of virus entry to the CNS. In addition, damage to the BBB as a result of endothelial cell infection may provide a mechanism for amplification of viral load in the CNS and may contribute to the CNS dysfunction that characterizes AIDS dementia and SIV encephalitis. These data suggest that MBEC may serve a selective role in determining virus entry to the CNS.

Expression of viral T-antigen in pathological tissues from transgenic mice carrying JC-SV40 chimeric DNAs.

Immunostaining methods were used to detect viral T-antigen and the cellular protein p53 in pathological tissues obtained from transgenic mice carrying JC-SV40 hybrid viral DNAs. A transgenic mouse carrying the SV40 regulatory region and JC virus (JCV) T-antigen-coding sequences exhibited an SV40-characteristic choroid plexus papilloma that expressed JCV T-antigen and p53. JCV-associated pathology was observed in two other mice in which the JCV regulatory signals directed SV40 T-antigen-induced adrenal neuroblastomas and brain neoplastic cells. However, these mice also exhibited an SV40-characteristic osteosarcoma and abdominal lymphoma that contained SV40 T-antigen and p53-positive cells. Contrasting thymic pathology was observed in the two types of mice where the SV40 regulatory region directed a JCV T-antigen-induced thymoma in one mouse, and the JCV regulatory region directed SV40 T-antigen-induced thymic hypoplasia in two other mice.

Brain vascular endothelial cells express JC virus large tumor antigen in immunocompetent and cyclophosphamide-treated hamsters.

When injected intracerebrally into newborn hamsters, the human polyomavirus JC virus (JCV) establishes a nonproductive infection resulting in brain tumor formation. Using immunostaining methods to detect the JCV regulatory protein, large tumor antigen (T antigen), we have now demonstrated JCV infection of brain vascular endothelial cells (EC) in infected hamsters. JCV T antigen was detected in lectin-labeled EC as well as in von Willebrand factor-expressing EC in both cyclophosphamide-treated and nonimmunosuppressed hamster brains 16, 21, and 31 days after birth. Cyclophosphamide-treated hamsters exhibited a greater number of JCV-infected EC, whereas T-antigen expression in nonvascular cells was not affected. The influence of cyclophosphamide was most pronounced in the cerebellum where increased numbers of JCV-infected EC were located predominantly at the internal granular layer-white matter junction, also a prominent location for T-antigen-expressing neoplastic foci. The hamster model demonstrates in vivo infection of EC by a human polyomavirus and directs interest toward the role of these cells in human JCV infection.

Immunolabeling of JC virus large T antigen in neonatal hamster brain before tumor formation.

Using immunolabeling methods, the JC virus (JCV) early or regulatory protein, large T antigen, was demonstrated in frozen sections of neonatal hamster brains before tumor formation. Three days after intracerebral inoculation of 2500 hemagglutinating units of JCV, T antigen was expressed predominantly in nuclei of cells in the external granular layer and newly forming internal granular layer of the cerebellum and also in cell nuclei located in the hippocampus, periventricular areas, and the olfactory bulb. At 7 days postinoculation (p.i.), most cerebellar T antigen-containing cells had migrated to the internal granular layer, but by 15 days p.i., cells that expressed T antigen was greatly reduced in number or absent. However, by 30 days p.i., the internal granular layer of the cerebellum again contained T antigen-positive cells. In contrast to the scattered cells seen at 3 or 7 days p.i., these cells appeared in dense clusters thought to represent pretumor foci. Since JCV capsid proteins were not detected at any time, JCV may establish a latent or abortive infection in cells during their mitotic phase and these cells initially express T-antigen during migration or become immunoreactive later before tumor formation.