Inhibition of Multiple Subtypes of Influenza A Virus in Cell Cultures with Morpholino Oligomers

Peptide conjugated phosphorodiamidate morpholino oligomers (P-PMO) are single-stranded-nucleic-acid-like antisense agents that can reduce gene expression by sterically blocking complementary RNA sequence. P-PMO are water soluble, nuclease resistant, and readily achieve uptake into cells in culture under standard conditions. Eight P-PMO, each 20-22 bases in length, were evaluated for their ability to inhibit Influenza A virus (FLUAV) A/PR/8/34 (H1N1) replication in cell culture. The P-PMO were designed to basepair with FLUAV RNA sequences that are highly conserved across viral subtypes, and considered critical to the FLUAV biological-cycle, such as gene segment termini and mRNA translation start site regions. Several P-PMO were highly efficacious, each reducing viral titer in a dose-responsive and sequence-specific manner in A/PR/8/34 infected cells. Two P-PMO, one designed to target the AUG translation start-site region of PB1 mRNA and the other the 3' terminal region of NP vRNA, also proved to be potent against several other FLUAV strains, including A/WSN/33 (H1N1), A/Memphis/8/88 (H3N2), A/Eq/Miami/63 (H3N8), A/Eq/Prague/56 (H7N7), and the highly pathogenic A/Thailand/1(KAN-1)/04 (H5N1). The P-PMO exhibited minimal cytotoxicity in cell viability assays. High efficacy by two of the P-PMO against multiple FLUAV subtypes suggests that these oligomers represent a broad-spectrum therapeutic approach against a high percentage of known FLUAV strains.