Cultivation of Rabies Virus in Human Diploid Cell Strain WI-38

Summary In spite of the initial infectivity of three strains of rabies virus for the human diploid cell strain WI-38, the virus could not be serially propagated in this cell system with conventional methods of passaging infectious material. However, by following the mixing-cell transfer technique, three strains could finally be adapted so that they could propagate indefinitely. The adapted HEP virus caused a cytopathic effect in WI-38 and its infectivity, for four other tissue culture systems of different animal origins increased during the course of its propagation in WI-38. After adaptation to WI-38, the HEP strain seemed to lose its lethal properties for monkeys injected intracerebrally, while acquiring a high degree of immunizing capacity for the same species. Inactivated vaccines prepared from two other strains of fixed virus (CVS and PM) were found to be highly antigenic after adaptation to WI-38. This fact and the availability of the WI-38-adapted live HEP virus seem to indicate that production of effective and safe anti-rabies vaccine for man is now feasible. Finally, because of good antigenic properties demonstrated either by the live attenuated HEP virus or by inactivated CVS and PM viruses grown in WI-38, an ideal medium for the production of human vaccines, effective and safe immunization of man against rabies may not be too far away.