Identification of influenza A nucleoprotein as an antiviral target

Abstract

Influenza A remains a significant public health challenge because of the emergence of antigenically shifted or highly virulent strains. Antiviral resistance to available drugs such as adamantanes or neuraminidase inhibitors has appeared rapidly, creating a need for new antiviral targets and new drugs for influenza virus infections. Using forward chemical genetics, we have identified influenza A nucleoprotein (NP) as a druggable target and found a small-molecule compound, nucleozin, that triggers the aggregation of NP and inhibits its nuclear accumulation. Nucleozin impeded influenza A virus replication in vitro with a nanomolar median effective concentration (EC(50)) and protected mice challenged with lethal doses of avian influenza A H5N1. Our results demonstrate that viral NP is a valid target for the development of small-molecule therapies.

Stabilization of protein–protein interactions by small molecules

“…Hence, inhibitors of NP function could be of interest as therapeutic agents. The groups of Yuen and Wong reported the identification of nucleozin as an NP inhibitor with antiviral activity [81,82]. In 2011, researchers at Bristol Myers Squibb identified related compounds via highthroughput screening [83].…”

Mycophenolic acid, an immunomodulator, has potent and broad-spectrum in vitro antiviral activity against pandemic, seasonal and avian influenza viruses affecting humans

“…Plaque reduction assay was performed as we described previously with slight modification (Kao et al, 2010). Briefly, MPA serially diluted in MEM was added to MDCK cells in 12-well plates for 2 h. Then, influenza viruses were added at 160 plaque-forming units/well and incubated for 1 h. After incubation, the virusÀMPA mixture was removed and the cells were washed by phosphate-buffered saline, twice.…”

“…For the control group, DMSO alone was used instead of MPA. At predetermined time points postinfection, the supernatants were collected for virus quantification using plaque assay as described previously (Kao et al, 2010). Each experiment was performed in duplicate, and the results were the means of two independent experiments.…”

“…To confirm the cytotoxicity results from our previous high-throughput chemical library screening (Kao et al, 2010), we have performed the cytotoxicity assay in Madin Darby canine kidney (MDCK) cells using the methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay. The 50 % cellular cytotoxicity (CC 50 ) of MPA was over 50 µM ( Fig.…”

“…We have previously used a high-throughput chemical screening platform to search for novel antivirals and discovered that nucleozin has potent antiviral activity and was able to protect mice from lethal infection (Kao et al, 2010). Using the same platform, we have also screened 1280 compounds for anti-influenza activity.…”