Varicella-zoster virus: isolation and propagation in human melanoma cells at 36 and 32°C

Abstract

Cell lines derived from human malignant melanoma tumors are susceptible to infection with varicella-zoster virus (VZV). Within 5 days after inoculation of vesicular fluid, cytopathic changes appeared in melanoma cell monolayer cultures that were incubated at either 36 or 32°C. The VZV isolates at the two temperatures were serially propagated by passage of trypsin-dispersed infected cells. A plaque assay was developed utilizing melanoma cell monolayers overlaid with nutrient medium containing carboxymethylcellulose. By this assay method, the growth cycle of a VZV isolate propagated at 36°C was studied and compared with that of another VZV isolate grown at 32°C. With equivalent infected-cell inocula at a ratio of one inoculum cell to eight uninfected cells, the yield of cell-free virus at an incubation temperature of 32°C was slightly higher than at 36°C, although the peak occurred 60 hr, rather than 36 hr, postinfection. It was also found that the titer of low-passage VZV propagated at 36°C was 0.5 to 1 log higher when assayed at 32°C rather than at 36°C.