Fluorescent cell counting as an assay method for respiratory syncytial virus.
The fluorescent cell-counting technique was applied to the enumeration of cell-infecting units of respiratory syncytial (RS) virus in human fetal diploid (HFD) cover-slip cell cultures; it was a sensitive, precise, and rapid assay method. Approximately 2 hr was required for maximal adsorption of RS virus to HFD cell monolayers. However, about 15% of the infectious virus in the inoculum remained unadsorbed; this percentage was not significantly reduced even when the adsorption period was extended to 5 hr. A linear relationship between virus concentration and the number of fluorescent cells existed over a range of 1.2 log(10) units. Variation of the mean of replicate determinations in a single experiment was approximately 7.5%. The distribution of single infected HFD cells on cover-slip cell cultures corresponded with the calculated frequencies of the Poisson distribution. The Chi square test for the extent of fit was calculated for several experiments, and the value of P was never less than 0.5. The addition of immune serum after virus adsorption effectively inhibited the development of detectable levels of viral antigen in secondarily infected cells.
D000327:Adsorption; D002460:Cell Line; D046508:Culture Techniques; D003588:Cytopathogenic Effect, Viral; D004622:Embryo, Mammalian; D005455:Fluorescent Antibody Technique; D006801:Humans; D008168:Lung; D012136:Respiratory Syncytial Viruses / Q000276:immunology*