Expression of antisense RNA fails to inhibit influenza virus replication

Cell lines were constructed which permanently express influenza virus-specific RNA. Two approaches were followed. C127 cells were transformed with bovine papilloma virus (BPV) vectors and the resulting cell lines were found to inhibit the replication of influenza virus at low multiplicity of infection (MOI 0.05). However, examination of cellular RNA using single-stranded probes revealed the presence of both (+)sense and antisense RNA transcripts (45-70 copies per cell). In this BPV-based system the inhibitory activity appeared to be associated with a non-specific, interferon (IFN)-mediated effect. In the second approach, an expression system was used which involved 293 cells, a chimeric human cytomegalovirus (CMV)/human immunodeficiency virus (HIV) promoter, and methotrexate- (Mtx)-mediated gene amplification. Cells were found to express up to 7500 copies of influenza virus-specific RNA per cell at a steady state level. In this system no RNA transcripts of the opposite orientation were found. However, all cell lines permanently expressing either (-)sense or (+)sense viral RNA failed to reduce influenza virus titers in a multi-cycle replication experiment (MOI 0.01).