Gene expression in visna virus infection in sheep

Abstract

Visna is a slow degenerative disease of the central nervous system (CNS) of sheep caused by a nontumorigenic retrovirus. During the course of this disease, visna virus establishes a persistent infection of the CNS, lung and haematopoietic system, despite a specific humoral and cellular immune response. We have studied visna virus life cycle at the single-cell level in choroid plexus of experimentally infected animals, using a very sensitive and quantitative in situ hybridization assay. We report here that although proviral DNA is synthesized in significant amounts, its expression is blocked at the transcriptional level. This restriction of proviral DNA transcription offers an explanation for the slowness of the disease and the persistence of the infection.

Identification and characterization of conserved and variable regions in the envelope gene of HTLV-III/LAV, the retrovirus of AIDS

“…However, the biologic relevance of these findings has been questioned by other workers who have discovered spread of virus in blood and CSF unabated by neutralizing antibodies (Petursson et al, 1976), long-term persistence of parental viral strains even after the appearance of variants (Lutley et al, 1983) and lack of antigenic variants in some animals even during advanced stages of disease (Thormar et al, 1983). Given the complexities of chronic retroviral-induced disease (Haase et al, 1977;Brahic et al, 1981;Stowring et al, 1985) it is likely that intrinsic viral characteristics as well as host-viral immune interactions play important roles in clinical outcome.…”

Persistence and Expression of Marek's Disease Virus DNA in Tumour Cells and Peripheral Nerves Studied by in situ Hybridization

“…The successful outcome of these experiments was predicated on two methodological (Brahic & Haase, 1978;Brahic et al, 1981;Haase et al, 1981). The M D V D N A fragments that we used as probes were clearly virus-specific and failed to hybridize with chick cell D N A ( Fig.…”

“…The conditions for detection and quantification of virus DNA and RNA were as previously described for visna virus (Brahic & Haase, 1978;Brahic et al, 1981) and for measles virus . The addition of dextran sulphate (10 %, w/v) to the hybridization mixtures enhanced hybridization and improved sensitivity.…”

A Transcriptional Map of Visna Virus: Definition of the Second Intron Structure Suggests a rev-like Gene Product

“…In contrast when these viruses are grown in permissive cells in tissue culture the virus multiplies in a comparatively rapid manner leading to cell death within days or weeks. In the case of visna virus it is clear that restriction of viral transcription and translation exists in vivo, but that this does not occur in vitro; cells containing small numbers of viral transcripts but expressing no detectable quantities of viral antigens are found in the animal, but such cells have not been reported in infections in vitro (Brahic et al, 1981 ;Gendelman et al, 1985).…”