SPECIFIC-INHIBITION OF APHTHOVIRUS INFECTION BY RNAS TRANSCRIBED FROMBOTH THE 5' AND THE 3' NONCODING REGIONS

RNA molecules containing the 3' terminal region of foot-and-mouth dise ase virus (FMDV) RNA in both antisense and sense orientations were abl e to inhibit viral FMDV translation and infective particle formation i n BHK-21 cells following comicroinjection or cotransfection with infec tious viral RNA. Antisense, but not sense, transcripts from the 5' non coding region including the proximal element of the internal ribosome entry site and the two functional initiation AUGs were also inhibitory , both in in vitro translation and in vivo in comicroinjected or cotra nsfected BHK-21 cells. This effect was not observed with nonrelated RN A transcripts from lambda phage. The inhibitions found were permanent, sequence specific, and dose dependent; an inverse correlation between the length of the transcript and the extent of the antiviral effect w as seen. In all cases, the extent of inhibition increased when viral R NAs and transcripts were allowed to reanneal before transfection, conc omitant with a decrease in the doses required. The antiviral effect wa s specific for FMDV, since transcripts failed to inhibit infective par ticle formation by other picornavirus, such as encephalomyocarditis vi rus. These results indicate that the ability of RNA transcripts to inh ibit viral multiplication depends on their efficient hybridization wit h target regions on the viral genome. Furthermore, cells transfected w ith the 5'las transcript, which is complementary to the 5' noncoding r egion, showed a significant reduction of plaque-forming ability during the course of a natural infection. RNA 5'las was able to inhibit FMDV RNA translation in vitro, suggesting that the inhibitions observed ar e mediated by a blockage of the viral translation initiation. Converse ly, hybridization of short sequences of both sense and antisense trans cripts from the 3' end induces distortion of predicted highly ordered structural motifs, which could be required for the synthesis of negati ve-stranded viral RNA, and correlates with inhibition of viral propaga tion.