Recovery of a Sendai virus variant with temperature-sensitive hemolytic activity from persistently infected cells from mouse brain.

A persistently infected cell line designated MB/Senas was established by cultivation of mouse brain cells from four-day-old C3H mice infected intracerebrally at birth with 10(6) PFU of Sendai virus, strain 52. After 5 passages, 0.16 per cent of Sendai52 antiserum (containing two 50 per cent plaque reducing doses/ml of serum) was introduced into the culture medium. The addition of antiserum was accompanied by a rise in cell-associated viral antigen from a level of 5 per cent antigen positive cells to 100 per cent demonstrable by both intracellular and membrane immunofluorescence. A variant of Sendai52 virus, designated Sendaias, was recovered from MB/Senas by inoculation of supernatant medium into chick embryos. Infection of chick embryos at 37 degrees C was abortive. Fifty per cent or less of chick embryos infected at dilutions 10(-1) to 10(-9) yielded detectable virus. Hemagglutination (HA) was weak but could be improved by trypsinization of allantoic fluids. Neuraminidase (NA) activity was barely detectable. Hemolysis (HE) was absent. Propagation of Sendaias virus at 33 degrees C showed no change from weak HA and NA activities but HE activity was now apparent which was temperature sensitive. Mortality of infected chick embryos increased to 100 per cent. HE activity and lethality for chick embryos was thermolabile at 45 degrees C.