QUANTIFICATION OF REPLICATION OF CLINICAL CYTOMEGALOVIRUS ISOLATES INCULTURED ENDOTHELIAL-CELLS AND FIBROBLASTS BY A FOCUS EXPANSION ASSAY

A method for quantitative analysis of the growth properties of human c ytomegalovirus (HCMV) in various cell culture systems was developed. R ecent HCMV isolates are, in most cases cell associated, causing only l imited cytopathic effect. This renders comparative analysis of the bio logical properties of such isolates difficult. The focus expansion ass ay described in this study is based on cocultivation of infected fibro blasts with a cell type of choice, relying on cell mediated infectivit y. The extent of replication of a given isolate in cell culture is qua ntified by determining the size of resulting infectious foci. Analysis of various clinical isolates and laboratory strains indicated that th is assay is a reliable and valid method to define growth properties of HCMV in cell culture. Remarkable differences in the cytopathogenicity of these isolates in fibroblasts as well as in endothelial cells were found. The assay will be useful in studies regarding cell tropism and virulence of recent HCMV isolates and for the quick and easy phenotyp ic characterization of HCMV deletion mutants. Copyright (C) 1997 Elsev ier Science B.V.