Theiler's virus persists in glial cells during demyelinating disease

Antigenic variants are not selected during persistent infection with Theiler's virus

In this study, we demonstrated that non-neutralizable antigenic variants of Theiler's murine encephalomyelitis virus do not predominate during the course of chronic relapsing infection.

Persistent infection of oligodendrocytes in Theiler's virus-induced encephalomyelitis

Mice infected with Theiler's murine encephalomyelitis virus (TMEV) develop a chronic relapsing demyelinating myelitis. To determine the localization of viral antigen in infected cells of the spinal cord, we studied TMEV-infected SJL/J mice using immunoelectron microscopic peroxidase-antiperoxidase techniques. Viral antigens were expressed in the cytoplasm of neurons and astrocytes 4 and 11 days postinfection. At 28 days postinfection, macrophages, astrocytes, and oligodendrocytes showed viral antigen in their cytoplasm. At 45, 83, 270, and 360 days postinfection, most infected cells were oligodendrocytes as revealed ultrastructurally by immunoperoxidase staining of prominent glial loops that connect with myelin lamellae. Some of these sheaths also showed Schmidt-Lanterman incisures that stained for viral antigen. Virus could be recovered at low titers for the duration of the illness. The findings indicate that TMEV induces persistent infection of oligodendrocytes which could then become the target of immune-mediated injury resulting in demyelination.

Characterization of a cell culture persistently infected with the DA strain of Theiler's murine encephalomyelitis virus

We established a persistent infection in L 929 cells with the DA strain of Theiler's murine encephalomyelitis virus. Our studies showed that only a small number of cells in the cultures contained infectious virus or viral antigen. A role for interferon in the maintenance of persistence was suggested. Viral isolates from the cultures were not temperature sensitive, nor did they contain viral capsid polypeptide mutations or defective interfering particles. T1 oligonucleotide maps showed evidence of mutation in two of three isolates.

Detection of tissue culture-adapted Theiler's virus RNA in spinal cord white matter cells throughout infection

The appearance of histological lesions and the localization of viral RNA in the central nervous system of mice infected with tissue culture-adapted Theiler's murine encephalomyelitis virus (WW strain) (TMEV-WW) was studied. Viral RNA was detected by autoradiography after in situ hybridization, using a (3)H-labeled DNA probe complementary to virion RNA, which was applied to deparaffinized sections of central nervous system tissues from infected mice. Subjacent histological sections of tissues were used to assess the location and extent of lesions. Lesions were first observed at 20 days post-inoculation and appeared to enlarge throughout infection. They consisted of infiltrates of mononuclear cells and lymphocytes in spinal cord white matter and leptomeninges; at 78 days post-inoculation severe necrotizing and demyelinative myelitis and gliosis were observed. In contrast to the pathogenesis of brain-derived TMEV-WW-infected mice, no lesions were found in the central nervous system gray matter of mice infected with tissue culture-adapted TMEV-WW at any time post-infection. Tissue culture-adapted viral RNA was found in the cells of spinal cord white matter throughout infection; only one neuron in close proximity to the injection site was found to contain viral RNA shortly after infection. At early times after infection, spinal cord white matter cells containing viral RNA were found before development of inflammatory lesions; at later days post-inoculation, positive cells were found within, at the periphery of, or at a distance from lesions. The number of infected cells and the amount of viral RNA per cell appeared to remain constant from 20 to 78 days post-inoculation despite the increasing intensity of the inflammatory response. The nearly exclusive spinal cord white matter tropism of tissue culture-adapted TMEV-WW appeared to directly correlate with the disease-inducing potential of this virus.