Scrapie strain-specific interactions with endogenous murine leukaemia virus

The finding that a senescence-accelerated mouse (SAMP8) shows early brain a geing, with histopathological changes resembling those seen in scrapie, com bined with the discovery of high levels of endogenous murine leukaemia viru s (MuLV) in brains of SAMP8 mice prompted us to examine the effect of scrap ie infection on MuLV titres in this strain and in one of its progenitors, t he AKR strain. Three scrapie strains (ME7, 22L and 139A) that had a compara tively short incubation period in SAMP8 and AKR mice caused an increase in brain MuLV titres that was scrapie strain-specific: in each mouse strain, t he greatest effect was with 139A, and the least with ME7. The 22A scrapie s train, which has a long incubation period in SAMP8 mice, did not affect MuL V titres in brains of this mouse strain. Previous analyses of scrapie incub ation periods in AKR, SAMP8 and another strain derived from an AKR cross (S AMR1) showed an inverse relationship between brain MuLV titres and scrapie incubation periods. This finding, combined with the effect of scrapie on Mu LV titres, suggests an interaction between the scrapie infectious process a nd MuLV replication.