In vitro cytopathogenicity and in vivo virulence of two strains of canine parainfluenza virus.

In vivo and in vitro properties of two strains of canine parainfluenza virus(CPIV) were investigated. One strain, designated CPIV(+), induced syncytial giant cell formation and cytolysis in vitro, whereas the second strain, CPIV(−), caused only a mild strand-forming cytopathic effect with few, small syncytial giant cells. Vero cells infected with CPIV(+) or CPIV(−) were 100% positive for CPIV antigen as determined by immunofluorescent staining; however, 100% of CPIV(+) and less than 10% of CPIV(−) infected cells were hemadsorption positive. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis analysis revealed no differences in electrophoretic mobility of viral polypeptides between both strains; however, in CPIV(−) reduced or absent synthesis of the putative HN and F1 proteins was observed. Isopyenic separation of CPIV(+) progeny virions showed a high proportion of viral particles with a buoyant density of 1.18 g/cm3. In contrast, CPIV(−) progeny virions had a heterogeneous density profile ranging f...