Targeting host cell ion channels to treat herpesvirus infections

The Herpesviridae are associated with life-long persistent infections. The nine human herpesviruses cause a range of acute and chronic diseases, ranging from cold sores to cancer. There is an urgent need for the development of novel anti-herpesvirus drugs; targeting host ion channels, which are manipulated during various viral replication cycles, present a novel avenue for pan-herpes antiviral treatments. Investigation utilising potassium channel inhibitors led to identification of Kv1.3 as essential during lytic KSHV replication. Both RNA and protein levels of Kv1.3 during KSHV reactivation were increased; overexpression causes increased channel activity and membrane hyperpolarisation in cells hosting lytic replication, this was measured through patch clamping techniques and flow cytometry. Experiments into the cause of Kv1.3 upregulation found a virally mediated mechanism, requiring both viral Rta and host Sp1 transcription factor activity. As channel blockade is sufficient to prevent this hyperpolarisation mechanism; Kv1.3 knockdown cell lines were generated using a lentiviral system, thus reducing levels of lytic replication. However, reactivation can be rescued with the use of a calcium ionophore, bypassing the membrane hyperpolarisation which leads to calcium influx. To confirm this influx, a ratiometric dye was used to detect calcium levels throughout the first 24 hours of reactivation from latency. This influx activates the calcium signalling pathway via NFAT1 nuclear localisation, and various NFAT-mediated genes are upregulated 24 hours post-reactivation. Additional research into the effects of K+ channel blockers on HSV-1 infection has shown a conservation of cell membrane hyperpolarisation, followed by calcium influx in cells infected with HSV-1. Given the abundance of ion channel inhibitors currently in clinical trials; this viral driven, hyperpolarisation mediated, calcium influx mechanism presents a novel avenue for pan-herpes antiviral treatments.