Infecção por Cardiovirus (virus da encefalomielite murina de Theiler - TMEV) em colonias convencionais de ratos

AUTOR(ES)
DATA DE PUBLICAÇÃO

2004

RESUMO

Theiler s murine encephalomyelitis virus (TMEV) is an enteric pathogen of mice and belongs to the Cardiovirus genus in the family Picornaviridae. TMEV is a non-enveloped, icosaedric virus with 20 - 30 nm size and it has an RNAss positive sense genome. TMEV has been divided in two subgroups on the basis of their biological activities after intracerebral inoculation. Neurovirulent strains (GDVII and FA) causes an acute and fatal encephalitis in mice and in contrast, low neurovirulent strains (DA, BeAn 8386, WW and TO) causes a persistent infection in the central nervous system and produce a chronic disease characterized by demyelination. TMEV infection with low neurovirulent strains has been used as an experimental model to help the studies on demyelination process induced by virus infection and to study diseases as Multiple Sclerosis. The natural infection by TMEV has been related in conventional colonies of mice and it s frequently asymptomatic. Although TMEV has been described as a pathogen of mice, antibodies against TMEV-GDVII has been detected in serum of rats reared in non-barrier colonies. Facing this, the purpose of the present study was to demonstrate the natural infection of TMEV in rat colonies through serological and molecular methods (RT-PCR). The rat serum were analysed by indirect immunofluorescence assay and antibodies against TMEV-GDVII were detected in 86,3% of the serum analysed. In the neutralization assay, 77,2% of the same serum showed neutralizing antibodies anti TMEVGDVII. To further isolate this rat virus, "in vitro" and "in vivo" systems were used. Nine blinded passages of the intestinal suspension were realized in BHK-21 cells, but no citopathic effect was identified. Clinical signs of TMEV infection in mice were characterized by flaccid paralisis of hind legs and tremor when newborn rats and mice were inoculated with intestinal suspension of seropositive rats and with the prototype strain of TMEV-GDVII. The RT-PCR results showed the RNA genome in the brain samples of rats and mice inoculated both with the intestinal suspension and the prototype strain. In the fecal samples, the RNA genome was also detected. In summary, rats can be naturally infected by TMEV and although there are a few examples in the literature of TMEV infection interference with biomedical researches, a health monitoring program for TMEV should be included in the rat colonies.

ASSUNTO(S)

infection rats rato microbiologia microbiology infecção

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