Persistent infection of a nonvector mosquito cell line (TRA-171) with dengue viruses

Dengue viruses often caused an apparent, persistent infection in a cell line derived from a nonvector mosquito, Toxorhynchites amboinensis. The characteristics of the viruses were modified during the course of persistent infection, as demonstrated by the changes in neutralizing titers of hyperimmune ascitic fluids against dengue serotypes, increased ability to induce syncytia, and increased temperature sensitivity. Although neurovirulence in suckling mice was reduced for all serotypes, considerable levels of neurovirulence were detected for DEN-1, DEN-2, and DEN-4, after 1 year in culture. Replication of the original viruses was not significantly inhibited when the cell cultures were treated with virus-free supernatant fluids from persistently infected cultures.