Deletion or substitution of the aphthovirus 3 ' NCR abrogates infectivity and virus replication

The 3' noncoding region (NCR) of the genomic picornaviral RNA is believed t o contain major cis- acting signals required for negative-strand RNA synthe sis. The 3' NCR of foot-and-mouth disease virus (FMDV) was studied in the c ontext of a full-length infectious clone in which the genetic element was d eleted or exchanged for the equivalent region of a distantly related swine picornavirus, swine vesicular disease virus (SVDV). Deletion of the 3' NCR, while maintaining the intact poly(A) tail as well as its replacement for t he SVDV counterpart, abrogated virus replication in susceptible cells as de termined by infectivity and Northern blot assays. Nevertheless, the presenc e of the SVDV sequence allowed the synthesis of low amounts of chimeric vir al RNA at extended times post-transfection as compared to RNAs harbouring t he 3' NCR deletion. The failure to recover viable viruses or revertants aft er several passages on susceptible cells suggests that the presence of spec ific sequences contained within the FMDV 3' NCR is essential to complete a full replication cycle and that FMDV and SVDV 3' NCRs are not functionally interchangeable.