Aurintricarboxylic Acid Is a Potent Inhibitor of Influenza A and B Virus Neuraminidases

Hashem, Anwar M.; Flaman, Anathea S.; Farnsworth, Aaron; Brown, Earl G.; Van Domselaar, Gary; He, Runtao; Li, Xuguang

We and others have reported that ATA can inhibit certain RNA viruses; therefore, we postulated that ATA may also inhibit the replication of influenza viruses. To evaluate the ability of ATA to protect MDCK cells from influenza infection, cells inoculated with different influenza A viral strains were incubated in the presence or absence of ATA (50 or 100 mg/ml) for 2 days. Microscopic examination revealed a drastic reduction of influenza-induced CPE following treatment with ATA (data not shown). The viability of MDCK cells infected with influenza A viruses and incubated in the presence or absence of ATA was then assayed by incorporation of neutral red dye. Infected cells treated with ATA had increased neutral red uptake ( Fig. 1) , confirming that ATA significantly protected MDCK cells from influenza infection (p,0.0001). ATA concentration that caused 50% cytotoxicity (CC 50 ) in MDCK cells was determined by assaying neutral red uptake and was found to be 577 mg/ml ( Fig. 2A) . As shown in Fig. 2B , ATA prevented PR8 infection of MDCK cells in a dosedependent manner with a minimum effective dose of 6.5 mg/ml required to protect 50% of cells (EC 50 ). Therefore, the therapeutic/selective index (SI) which refers to the ratio of the amount of ATA exerting its therapeutic effect to the amount that causes toxicity in MDCK cells is 88.8.