Abstract
Virus-like particles (VLP) are multimeric proteinaceous structures which resemble a naturally occurring virus, but do not possess the genetic material needed for infection and replication. VLP are an attractive choice for use in vaccination due to their potent stimulation of both the humoral and cell-mediated arms of the immune system, via the MHC-class I and class II pathways. Dense and repetitive epitopes on the surface are important determinants in VLP immunogenicity and biological activity, therefore maintaining tertiary structural integrity of the proteins are important. The continuum of processes which maintain this structural integrity and, therefore, vaccine efficacy relies on the proper handling of material, including the maintenance of vaccines between 2-8° C from the point of manufacture to administration, is known as the ‘cold- chain’. The cold-chain has become an integral and essential part of vaccination regimes, making up a significant portion of costs. Improper handling of vaccine material in the cold-chain could lead to an unrecoverable loss in funding and administration of ineffective vaccines.
This project is centred around developing a method to stabilize VLP for potential dry- storage to break away from the reliance on the cold-chain. Electrospinning provides a cheap, fast and simple way of generating a dry formulation at ambient temperature, without the temperature stresses associated with freeze-drying. In this work, we present a novel, simple, cost-effective method of combining VLP into an electrospun nanofibre based on the water-soluble polymer, polyvinylpyrrolidone (PVP). The nanofibre acts as a vehicle to store and transport the VLP without the need for stringent temperature control or freeze-drying. The nanofiber functions as a scaffold for the VLP to adhere to and can be reconstituted into an aqueous buffer at the site of administration without further purification. Electrospun nanofibres also have the added advantage of having tuneable properties for controlled drug or biologic release.
This study involved VLP derived from rabbit haemorrhagic disease virus (RHDV) as a model antigen to be stabilised by electrospinning. We have shown that VLP can be electrospun into a nanofibre mat with up to 20% efficiency and that VLP can be visualised by scanning electron microscopy on the surface of nanofibres once electrospun. Furthermore, intact particles were isolated by re-purification following nanofibre dissolution after storage at ambient temperature. To test the functionality of the stabilised VLP, reconstituted VLP nanofibers were validated in vitro and in vivo. VLP reconstituted from the nanofibre produced a cytotoxic and humoral immune response in mice that was comparable to that of free, intact VLP. This technology has shown promise to act as a stabilising technique for RHDV VLP and has the potential to be applied to currently available vaccines and pharmaceuticals.