FIG. 3.

Growth of selected viruses in bovine () and swine (■) keratinocytes. Representative data show replication of the indicated viruses in keratinocytes of the species indicated, expressed relative to side-by-side replication of vCRM8 (a genetically engineered virus which is highly virulent in bovine and swine [1, 21]). The bar and extended bar represent the results of two independent values obtained in the same experiment. Nomenclature and host of origin for viruses are given in Table 1; underlined viruses were isolated from bovine samples, and all other isolates were from swine (Table 1). For the replication assays, monolayer cultures of bovine or swine keratinocytes derived from lingual epithelial tissue (prepared using a modification of a method for developed for cultivating keratinocytes from human skin biopsies [2]) were incubated with virus for 1 h at 37°C with a multiplicity of infection of 10 (based on plaque assay in BHK cells). At the end of the adsorption period, the inoculum was removed and the cell layers were rinsed twice with ice-cold 145 mM NaCl, 25 mM morpholineethanesulfonic acid (pH 5.5) to remove residual virus particles; the cells were then rinsed with BME containing 1% fetal calf serum and 25 mM HEPES (pH 7.4) and incubated in 1 ml of this medium for 6 h at 37°C. The cultures were frozen at −70°C, and the titer (PFU per milliliter) was determined on BHK cells (18).