Cell-fusion assay for the detection of rubella virus in Vero cells

Abstract

Background and objectives: Rubella virus (RV) produces a subtle and slow-developing cytopathic effect in Vero cells that is difficult to recognize, especially at low multiplicities of infection. In order to facilitate the detection of RV in cell culture, we standardized a low-pH virus-mediated cell-fusion assay. Study design: The incubation periods, temperatures, pH and multiplicity of infection were established. The specificity of the method was tested by immunofluorescence assay and cell-fusion inhibition by specific sera. Results: Six days post infection, Vero cells were treated for 5 min with fusion medium. After that, monolayers were incubated with medium at neutral pH for 16 h and then stained. Gigantic cells with multiple nuclei were observed. Conclusions: The method allowed the observation of unequivocal images that are easier to recognize than the cytopathic effect caused by RV in the same cell line. At the same time, the method is simple, accessible and shown to be specific to demonstrate the replication of several strains and isolates of RV in Vero cells.