ABSTRACT
Thermostability and propagation in different cell cultures and interferon-producing ability of three vaccine mumps virus strains (Jeryl Lynn, Leningrad-Zagreb and PZH-17) and ten wild viruses isolated from patients suffering from mumps were investigated. Considerable differences were found after vaccinal and wild virus strains were subjected to a temperature of 50 degrees C for 30 minutes. Wild strains were significantly more thermoresistant than the vaccinal ones. Differences in the propagation ability between wild an attenuated vaccinal strains were also found when tested in the Vero cell line and in primary cell cultures of human amnion. Wild strains propagated equally well in both cultures, while the vaccine strains propagated significantly better in the Vero cell line. The quantities of interferon produced by vaccinal and wild virus strains were determined by the micromethod titration technique. The vaccinal strains produced greater quantities of interferon than the wild ones, but from these differences no conclusions concerning the degree of their attenuation could be arrived at. From the results presented, it can be concluded that there is a correlation between the temperature marker and a difference in the propagation ability in the Vero cell cultures and the primary cell cultures of human amnion, and that these differences could be used as the genetic marker.