Inhibition of influenza A virus replication by antagonism of a PI3K-AKT-mTOR pathway member identified by gene-trap insertional mutagenesis.

Background: Host genes serving potential roles in virus replication may be exploited as novel antiviral targets.

Methods: Small interfering RNA (siRNA)-mediated knockdown of host gene expression was used to validate candidate genes in screens against six unrelated viruses, most importantly influenza. A mouse model of influenza A virus infection was used to evaluate the efficacy of a candidate FDA-approved drug identified in the screening effort.

Results: Several genes in the PI3K-AKT-mTOR pathway were found to support broad-spectrum viral replication in vitro by RNA interference. This led to the discovery that everolimus, an mTOR inhibitor, showed in vitro antiviral activity against cowpox, dengue type 2, influenza A, rhino- and respiratory syncytial viruses. In a lethal mouse infection model of influenza A (H1N1 and H5N1) virus infection, everolimus treatment (1 mg/kg/day) significantly delayed death but could not prevent mortality. Fourteen days of treatment was more beneficial in delaying the time to death than treatment for seven days. Pathological findings in everolimus-treated mice showed reduced lung haemorrhage and lung weights in response to infection.

Conclusions: These results provide proof of concept that cellular targets can be identified by gene knockout methods, and highlight the importance of the PI3K-AKT-mTOR pathway in supporting viral infections.