Defective viral RNAs in Aedes albopictus C6/36 cells persistently infected with Semliki Forest virus

A persistent infection of Semliki Forest virus (SFV) has been established in Aedes albopictus C6/36 cells. Only a small number of cells survived the initial infection with this RNA virus and gave rise to a persistently infected culture which produced continuously small amounts of infectious virus. To investigate whether defective viral RNA is involved in establishing and maintaining a persistent infection, the intracellular viral RNA was analyzed early and late after infection by blot hybridizations. Several defective viral RNAs were detected with a common sequence corresponding to the 3′ end of the viral genome during and after the establishment of the persistent infection. These defective viral RNAs resemble the defective interfering RNAs in vertebrate cells generated during serial undiluted passages of standard SFV. The defective viral RNAs are rarely released from cells as virions. The rapid generation of defective viral RNAs may be important for the establishment of a persistent infection in mosquito cells.