Lymphocytic Choriomeningitis virus. I. Concentration and purification of the infectious virus

Two procedures for the purification of infectious lymphocytic choriomeningitis virus from cell culture fluid have been developed. If large quantities of very pure virus are to be prepared, infected L cells are maintained with a medium supplemented with calf serum, the proteins of which have been largely removed by pretreatment with polyethylene glycol. Two days after infection of the cultures, the media are collected and the virus is concentrated by treatment with polyethylene glycol 40,000. Purification with a 10,000-fold increase of specific infectivity is achieved with steric chromatography on controlled-pore glass beads with pore sizes of 42 to 44 nm and centrifugation in density gradients prepared with amido trizoate. An alternative method begins with precipitation of the virus from infected cell cuture medium with zinc acetate, followed by controlled-pore glass chromatography and density centrifugation in a discontinuous sucrose gradient. Purification thus obtained is 200-fold in terms of specific infectivity.