The mechanism of interference with fish viral infection in the RTG-2 cell line.

Abstract

The influence of cell density on viral infectivity titers and interferon production were studied by a plaque and end-point dilution method. The RTG-2 cell line was infected with eel virus European (EVE), infectious pancreatic necrosis virus (IPNV) and infectious hematopoietic necrosis virus (IHNV). The confluent condition of RTG-2 cells was classified into two phases according to the cell density, viz. loosely confluent (6.0 × 104 cells/cm2) and tightly confluent cell sheets (1.2 × 105 cells/cm2). Viral infectivity titers were highest in loosely confluent cell sheets. Virus titers decreased by 50-70% in a plaque method and 90-99% by end-point dilution in tightly confluent cell sheets. Conversely more interferon was produced in tightly rather than loosely confluent cell sheets. We may, therefore, conclude that interferon seems to be a factor contributing to the significant reduction of viral infectivity titers in tightly confluent cell sheets.