US Patent 7078218 Alphavirus particles and methods for preparation

Provided herein are methods for producing alphavirus replicon particles in high yield; replicon RNAs are electroporated into permissive cells, where the cells are at a relatively high density, together with at least one helper nucleic acid providing the necessary functions for packaging. After a growth period in appropriate medium, alphavirus replicon particles are harvested from the surfaces of the cells in which they were produced using a salt wash in which the salt concentration is from about 0.2 to about 5 M sodium chloride, calcium chloride, magnesium chloride, potassium chloride, ammonium acetate, ammonium bicarbonate, among others. After dilution, if necessary, the particles can be purified by a suitable chromatographic technique.