Immunofluorescent cell-counting assay for lymphocytic choriomeningitis virus

A quantitative assay for lymphocytic choriomeningitis virus was developed and standardized. The assay is based on direct immunofluorescent staining of infected L-929 cell monolayers and enumeration of cells containing fluorescent viral antigens. Maximal adsorption of virus to cells occurred within 1 h. Observations on the sequential development of viral antigens within cells showed that specific cytoplasmic fluorescence appeared within 10 h. The optimal time for enumerating fluorescent cells was from 18 to 20 h after addition of virus. A linear relationship was demonstrated between the number of infected cells and the relative virus concentration. Fluorescent cells were distributed randomly in infected cover slip cell monolayers. The immunofluorescent cell-counting assay for lymphocytic choriomeningitis virus was highly precise and reproducible.