Abstract
The Amicon TCIR recycle system with Diaflo PM30 filters provided a rapid, simple and inexpensive method for the concentration of baboon endogenous virus from a large quantity of culture medium from chronically infected cells. The recovery of infectivity and virion RNA-dependent DNA polymerase activity was substantially better than after the conventional concentration methods of ultra-centrifugation or precipitation with ammonium sulphate or polyethylene glycol 6000. The combination of ultrafiltration and Ficoll gradient centrifugation is recommended as a general procedure for the purification of fragile C-type viruses.