Isolation and characterization of the maedi visna virus from sheep in Poland

This paper describes the isolation and partial characterization of maedi visna wirus (MW) from sheep in Poland. MW was isolated by a co-culture technique using monocyte-derived macrophages from the blood, colostrum and bronchoalveolar lavage of seropositive sheep as donor cells and goat synovial membrane (GSM) indicatory cells. Out of fourteen macrophage co-cultures the presence of MVV was detected by syncytia formation and detection of proviral DNA in nine and thirteen co-cultures, respectively. For further analysis, two isolates, 0300 and 3262, which were shown to induce the most prominent cytopathic effect and progressive destruction of GSM cell monolayer, were compared with the prototypic K1514 Icelandic strain of MVV. Both isolates shared antigenic determinants as determined by western blotting using anti-MVV serum and positively reacted in PCR with primers spanning the fragment of gag gene of NVV. When uninfected GSM cells were incubated with supernatants from these cultures, syncytia formation was observed, indicating the presence of infectious cytopathic viruses. The titers of these viruses estimated by day 7 of the culture were log6 and log4 TCID50 for isolates 0300 and 3262, respectively, while isolate K1514 produced a maximum titer of log7 TCID50. Both isolates are good candidates for further analysis of their nucleotide sequence and pathogenicity in experimentally inoculated sheep.