24nd International Conference on Antiviral Research location:Sofia, Bulgaria date:8-11 May 2011
We previously reported on the in vitro anti-influenza virus activity and structure-activity relationship of hydrophobic derivatives of the glycopeptide compound aglycoristocetin3. In Madin-Darby canine kidney (MDCK) cells infected with different strains of influenza A/H1N1, A/H3N2 and B viruses, the lead compound 8e displays an antivirally effective concentration of 0.4 µM. The concentration producing 50% inhibition of cell proliferation was 67 µM, yielding an antiviral selectivity index of 167. Virus yield at 72 h p.i. was reduced by 3 logs at 5 µM 8e. Inhibition of virus replication by 8e was confirmed in A549, Vero and QT-6 cells. Influenza virus fully retained its sensitivity to 8e after eleven sequential virus passages in MDCK cells in the presence of 8e (at concentrations up to 25 µM). In time-of-addition studies, 8e lost activity when added 1 hour or later p.i., showing that 8e inhibits an early step in virus replication. 8e produced no inhibitory effect on binding of virus to MDCK cells at 4°C. Inhibition of hemagglutinin (HA)-mediated membrane fusion was excluded, since 8e had no effect on virus-induced red blood cell hemolysis at low pH, nor on polykaryon formation of HA-expressing cells exposed to low pH. Besides, 8e does not inhibit the conformational change of the HA at low pH, as observed in a tryptic digestion assay. Confocal microscopy on influenza virus-infected MDCK cells stained with anti-nucleoprotein antibody at 1 h p.i., revealed that 8e causes a marked inhibition of the nuclear entry of the virus by trapping the virus in an endosomal compartment. Studies with endosomal markers are ongoing to unravel precisely how 8e interferes with the influenza virus entry process. The aglycoristocetin derivative 8e represents a new class of potent and broad-acting influenza virus inhibitors with potential therapeutic relevance.