Understanding the Requirement for Host Ion Channels during Influenza A Virus Infection

Influenza A virus (IAV) results in 3-5 million cases of severe human illness and up to 650,000 deaths globally each year (WHO, 2022b), with these numbers rising drastically during deadly pandemics. Seasonal vaccination programmes cost billions of dollars each year and the high mutation rate of the virus has resulted in resistance to previously effective anti-viral drugs. New and more effective anti-IAV strategies are urgently required. Cellular ion channels are a developing area of research as virus-dependent host factors. These diverse, pore-forming proteins permit transport of ions across membranes, influencing a multitude of cellular processes from signal transduction to maintaining a normal lung surface liquid in the respiratory airway. Several cellular channels are now recognised as essential host factors across all stages of virus life cycles and can be targeted by small molecule channel blockers as a novel anti-viral therapeutic approach. Despite the immense disease burden for IAV disease, many aspects of the virus lifecycle are poorly characterised, including virus:host interactions with cellular ion channels across the lifecycle. This thesis employed a large, high throughput siRNA screen to evaluate the role of human cellular ion channels during IAV infection, utilising reverse genetics to generate a GFP-expressing H1N1 strain. Supporting this data with channel-specific pharmacological inhibitors, a critical requirement for a calcium-activated potassium channel was revealed. An investigation into the mechanisms underpinning the relationship between IAV and KCa2.3 revealed that the channel was fundamental for early stages of virus infection, specifically nuclear import through an early/late endosome or lysosome-independent mechanism. These findings not only imply an undefined molecular mechanism involving KCa2.3 but reveal it as an exciting target for future host-directed antiviral therapeutics. This data also alludes to several other potential druggable pro-viral host channels that can drive the discovery and design of new therapies to retaliate against a growing influenza resistance crisis.