siRNA delivery system for the treatment of herpes type-1

Herpes simplex virus (HSV-1) is a highly contagious virus, causing one of the most widespread infections. Although in most cases not lethal, immuno-compromised individuals may develop severe complications (1). Herpes viruses lay dormant inside neuronal cells, where they evade the immune system and consequently establish lifelong infections (2). We have identified siRNA (siHSV) that knocks down gene expression of the infected cell protein 0 (ICP0), which is important in the regulation of HSV infection. The selected siHSV was encapsulated in liposomes in order to overcome its poor stability, increase cell permeability, and prevent the rapid elimination of siRNA from the circulation.

We have successfully developed a PEGylated liposomal formulation (LipDOPE-siHSV) with desirable physicochemical properties including size (~130 nm), low polydispersity index (PDI, 0.2), neutral charge (2.7mV), high siHSV loading (670 µg/ml), spherical shape, and was found stable in physiologic conditions, with long-term shelf-life stability (> 1 year, 4ºC). The liposomes exhibited profound internalization by human keratinocytes, no cytotoxicity at the effective concentration range, no detrimental effect on mice liver enzymes, and a gradual endo-lysosomal escape. The therapeutic potential of siHSV liposomes was demonstrated by significant antiviral activity in the ex vivo 2D plaque assay and 3D epidermis model, and the mechanism was validated by the reduction of ICP0 expression levels. Ongoing research is focusing on formulating targeted liposomes to peripheral neurons, for effective therapy.

References:

(1) Cannon, M.J., D.S. Schmid, and T.B. Hyde. Rev Med Virol, 2010:20, 202-13.

(2) Koyuncu O, Hogue I, Enquist L. Cell Host Microbe. 2013:13, 379-393.