Anti-influenza virus activity of the neuraminidase inhibitor 4-guanidino-Neu5Ac2en in cell culture and in human respiratory epithelium

The anti-influenza activity of the neuraminidase inhibitor 4-guanidino-Neu5Ac2en (4-G-NAc) was determined in Madin-Darby canine kidney (MDCK) cells by yield reduction and ELISA and in explants of human respiratory epithelium by yield reduction. In MDCK cells, 50% inhibitory concentrations (EC 50) averaged 0.5 μg/ml for influenza A/Virginia/88(H3N2) and 0.04 μg/ml for A/Texas/36/91(H1N1) by ELISA, and < 0.01 μg/ml for influenza A/Virginia by yield reduction. In human adenoid explants, concentrations causing at least 1.0 log 10 TCID 50 /ml decrease in yield (EC 90) at 48 h were < 0.01 μg/ml for A(H1N1) and A(H3N2) viruses and 0.25 μg/ml for B/Hong Kong/5/72. 100 μg/ml 4-G-NAc did not inhibit outgrowth of human adenoid epithelium at 6 days, whereas ribavirin 10 μg/ml reduced outgrowth by > 50%. 4-G-NAc is a potent and selective inhibitor of clinical isolates of influenza A and B viruses in human respiratory epithelium.