Characteristics of a macrophage culture persistently infected with herpes simplex virus type 1

Background. Persistence of herpes simplex type 1 (HSV-1) has been reported in sensory neurons, corneal epithelium, and lymphocytes, although other cell types such as macrophages should also be considered as hosts for HSV-1 persistence. Here we report the establishment and characterization of HSV-1 persistence in an immortalized murine macrophage-like cell line (P388D1). Methods. The persistently HSV-1 infected culture (P388D1per) was obtained from surviving P388D1 macrophages infected with HSV-1 MP strain at multiplicity of 0.001. P388D1per was characterized by: extracellular production of viruses, cells expressing viral antigens, and cells releasing infectious viruses. Viral plaque size and cytophatic effect were determined in viruses (HSV(A) and HSV(B)) obtained from two different P388D1per passages. Host and viral proteins were detected in P388D1per and in P388D1 cells infected with HSV-1 by metabolic [³⁵S]-methionine labeling assays. Results. P388D1per culture was characterised by cyclic production of infectious viruses from non-detectable to 10⁶ TCID₅₀/mL; from 1.0 to 15.0% cells expressing viral antigens and macrophages released infectious viruses from 0.008 to 12.5%. Differences in viral plaque size and cytopathic effect morphology between HSV(A), HSV(B) and HSV-1 were observed. Similar patterns of viral proteins were observed in P38SD1per and in P388D1 infected with HSV-1. Nonetheless, the characteristic interference effect of HSV-1 on host protein synthesis was not observed in P388D1per culture. Conclusins. An HSV-1 persistently infected immortalized macrophage culture was es tablished and characterized. Virus produced during persistence showed phenotypic alterations with respect to the original virus. P388D1per cell protein synthesis was not affected by the presence of HSV-1.