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Distribution of ecotropic retrovirus receptor protein in rat brains detected by immunohistochemistry.

Friend murine leukaemia virus (FrMLV) FrC6 clone A8 causes spongiform degeneration in the central nervous system (CNS) of newborn but not 3-week-old rats. To assess whether expression of the ecotropic MLV receptor (CAT-1) in the CNS correlates with the pathogenicity of the A8 virus, we generated an anti-CAT-1 antibody raised against a synthetic peptide that corresponds to the carboxyl-terminal amino acid sequence of CAT-1. In the CNS of newborn and 3 to 4-week-old rats, a strong immunoreactivity against the antibody was detected in most of the endothelial cells. However, almost no expression of CAT-1 was detected in the CNS of 21-week-old rats. In newborn rats, many parenchymal cells in the brain as well as the vascular wall expressed CAT-1 antigen. These findings suggest that retrovirus receptor-bearing glial cells contribute to the neuropathogenesis of MLV, including clone A8, which induces spongiosis in rats only when inoculated into newborns.