[Chronic cell culture infection with the rabies virus]

Three cell cultures chronically infected with fixed rabies virus, strain MNIIVP-74, have been obtained: HEp-2/2, BHK/13S, and RK-13. In the former two cultures, the infectious virus titers were 2.0 to 5.25 Ig LD50/ml. In RK-13 cells, traces of the infectious virus were found. In the chronically infected HEp-2/2 culture the maximum amount of the antigen-containing cells determined by the fluorescent antibody procedure was 60% and in BHK/13S 80%. Chronically infected cultures had a reduced growth rate and were as sensitive as the controls of superinfection with vesicular stomatitis virus. The virus recovered from chronically infected culture produced a disease in mice at later intervals than the original virus used in the same doses.