Variation in murine cytomegalovirus replication in fibroblasts from different mouse strains in vitro: correlation with in vivo resistance.

The in vitro growth of murine cytomegalovirus (MCMV) in mouse embryo fibroblasts (MEF) from Balb/c, C57BL, C3H and CBA mouse strains has been shown to correlate with the genetically determined in vivo susceptibility of these strains to MCMV infection. MEF from Balb/c and C57BL mice were more susceptible to MCMV than those from C3H and CBA mice. This was evident regardless of whether replication was measured by cytopathic effect (c.p.e.) score, virus yield, plaque count, plaque size or time of onset of c.p.e. The growth of MCMV in tracheal organ cultures from different mouse strains was similar to that observed in MEF from these strains. The replication in MEF when measured by c.p.e. score and virus yield was affected by the density of the cell cultures. The strain of mouse used to produce MCMV also affected the comparative sensitivity of MEF to the virus. This appeared to be due to reduced growth of MCMV in its homologous MEF type, an unexpected result. In contrast, cell density had little effect on the replication of herpes simplex virus type 1 (HSV-1), but again the in vitro susceptibility of MEF reflected the in vivo susceptibility of mouse strains to infection with this virus.