Small molecule inhibitors of the c-Jun N-terminal kinase (JNK) possess antiviral activity against highly pathogenic avian and human pandemic influenza A viruses.

C-Jun N-terminal kinases (JNK) are activated in course of many viral infections. Here we analyzed the activity of JNK inhibitors on influenza A virus (IAV) amplification. Human lung epithelial cells were infected with either the highly pathogenic avian virus strain A/FPV/Bratislava/79 (H7N7) or the pandemic swine-origin influenza virus A/Hamburg/4/09 (H1N1v). The application of the JNK inhibitors SP600125 and AS601245 reduced IAV amplification by suppressing viral protein and RNA synthesis. Although AS601245 appeared to generally block the transcription of newly introduced genes, SP600125 specifically affected viral RNA synthesis. Overexpression of a dominant negative mutant of SEK/MKK4 and siRNA-mediated suppression of JNK2 expression confirmed that specific manipulation of the JNK pathway attenuates virus propagation. An IAV minigenome replication assay revealed that SP600125 did not directly affect the activity of the viral RNA polymerase complex but seems to suppress an anti-influenza nonstructural protein 1-mediated virus supportive function. Finally, when H7N7- or H1N1v-infected mice were treated with SP600125, the viral load is reduced in lungs of treated compared with untreated mice. Our data suggest that this class of ATP competitive inhibitors once optimized for antiviral action potentially represent novel drugs for antiviral intervention.