Comparison of WI-38, MRC-5, and IMR-90 cell strains for isolation of viruses from clinical specimens

Abstract

With the diminishing supply of the human fetal lung WI-38 cell strain, a replacement for viral isolation is needed. Two candidates are the human fetal lung strains MRC-5 and IMR-90. A comparison of WI-38, MRC-5 and IMR-90 was performed to evaluate efficiency and speed of viral isolation, clarity of cytopathic effect and ease of growing the cells. The inocula were clinical specimens rather than tissue culture-adapted isolates. Frozen samples of 46 specimens that had previously yielded an isolate on WI-38 were thawed and inoculated onto WI-38, MRC-5 and IMR-90 cells. In addition, 95 freshly taken clinical specimens of undetermined infectivity were inoculated onto the cell strains. Viral recovery rates were similar on all 3 strains, as were the appearance and speed of onset of the cytopathic effect. MRC-5 and WI-38 cells remained healthy until generation 36, whereas IMR-90 cells went into crisis by generation 20. The longer life span of the MRC-5 cells makes them more suitable than IMR-90 cells to replace the WI-38 strain for routine use in viral diagnosis.