New model cell systems (PK and XTC-2) for studying acute and persistent infections with herpes simplex and pseudorabies viruses.

Herpes simplex virus type 1 (HSV-1) showed limited replication in PK (pig kidney) and XTC-2 (Xenopus laevis frog) cell lines. Virus replication depended on the multiplicity of infection (MOI). At a high MOI, HSV-1 caused a typical cytopathic effect (CPE) in XTC-2 cells but a little marked CPE in PK cells. Pseudorabies virus (PRV) replicated intensively in PK cells (permissive system) but not in XTC-2 cells (nonpermissive system). Both viruses were adsorbed on to PK and XTC-2 cells. In infected PK cells, fluorescent HSV-1 antigen was demonstrated only in the vicinity of the nuclear membrane and in the paranuclear area of the cytoplasm but not in the nuclei. In XTC-2 cells, HSV-1 antigen was demonstrated also in the nuclei. Persistent HSV-1 infection was induced in PK but not in XTC-2 cells; it was of limited duration. PK cells which had lost HSV-1 multiplied further and proved susceptible to infection with HSV-1 or PRV.