The precipitating effect of polyethylene glycol 6000 (PEG) on arboviruses propagated in Vero cell cultures was studied. Efficiency of precipitation depended on the concentration of the polymer, of hydrogen ions, and of sodium chloride. Optimum recovery of Venezuelan equine encephalomyelitis virus infectivity was found at a PEG concentration of 10% at pH 7.6 and 0.25 m NaCl, the mixture having stood at 4°C for 1 hour. Concentration of four serologically unrelated arboviruses with this method showed that recoveries compared well with those obtained after ultracentrifugation. The method is recommended as an initial step in the concentration of arboviruses propagated in tissue culture, as it is simple, rapid, and inexpensive.
Present address: Bundesforschungsanstalt für Viruskrankheiten der Tiere, 74 Tübingen, West Germany.