CHARACTERIZING HOST TARGETED ANTIVIRALS THAT IMPAIR INFLUENZA A VIRUS PROTEIN SYNTHESIS
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The plasticity of influenza A virus (IAV) genomes enables rapid evolution of resistance to antivirals that directly target viral proteins. By contrast, host-targeted antivirals have the potential to disrupt key steps in viral replication and alert the immune system in a manner that is not so easily overcome by rapid viral evolution. Like all viruses, IAV uses host protein synthesis machinery to produce viral proteins. IAV mRNAs access this machinery by incorporating host 5’-cap structures and mimicking host 3’-polyadenylate tails. Host cap-dependent translation requires the RNA helicase eIF4A. Here, I demonstrate that treating infected cells with eIF4A inhibitors silvestrol or pateamine A inhibits IAV replication by preventing the accumulation of viral proteins required to support viral genome replication. However, these compounds were also cytotoxic, limiting their utility as host-targeted antivirals. The McCormick lab identified the thiopurines 6-thioguanine (6-TG) and 6-thioguanosine (6-TGo) as candidate molecules that stimulate host stress responses. I showed that these thiopurines inhibited IAV replication by activating the host unfolded protein response and selectively preventing the accumulation of IAV glycoproteins. Importantly, these molecules were not cytotoxic at doses required to disrupt viral replication. Finally, I directly investigated the plasticity of the IAV genome by identifying host adaptation mutations required to support viral replication in a murine infection model. I characterized novel substitutions in the viral polymerase subunits that increased polymerase activity and viral replication in cultured murine cells. Together, these studies have advanced understanding of the molecular basis of host adaptation and identified vulnerabilities that can be exploited by host-targeted antivirals.