Plaque assay and propagation in rat cell line LBC cells of rat coronavirus and 5 strains of sialodacryoadenitis virus.

Various factors influencing the plaque formation of rat coronavirus (RCV) and sialodacryoadenitis virus (SDAV) in LBC cell monolayers were studied to develop the practical method for plaque assay. By this method, 4 Japanese isolates of SDAV also produced clear plaques. In one-step growth experiments of these viruses, newly formed virus was first recognized within 7.5 h postinfection and showed subsequently a rapid exponential increase. The virus was released rapidly from the infected cells. By indirect immunofluorescence virus specific antigen was detected as perinuclear granules in the cytoplasm of the cells at 5-6 h postinfection, and all the cells revealed fluorescence at 12 h postinfection.