Virus-like Particle Vaccines and Platforms for Vaccine Development

Abstract

Virus-like particles (VLPs) have gained a lot of interest within the past two decades. The use of VLP-based vaccines to protect against three infectious agents-hepatitis B virus, human papillomavirus, and hepatitis E virus-has been approved; they are very efficacious and offer long-lasting immune responses. Besides these, VLPs from other viral infectious agents (that infect humans, animals, plants, and bacteria) are under development. These VLPs, especially those from human and animal viruses, serve as stand-alone vaccines to protect against viruses from which the VLPs were derived. Additionally, VLPs, including those derived from plant and bacterial viruses, serve as platforms upon which to display foreign peptide antigens from other infectious agents or metabolic diseases such as cancer, i.e., they can be used to develop chimeric VLPs. The goal of chimeric VLPs is to enhance the immunogenicity of foreign peptides displayed on VLPs and not necessarily the platforms. This review provides a summary of VLP vaccines for human and veterinary use that have been approved and those that are under development. Furthermore, this review summarizes chimeric VLP vaccines that have been developed and tested in pre-clinical studies. Finally, the review concludes with a snapshot of the advantages of VLP-based vaccines such as hybrid/mosaic VLPs over conventional vaccine approaches such as live-attenuated and inactivated vaccines.

Keywords: chimeric VLPs; efficacy; immunogenicity; vaccines; virus-like particles.

Figure 1

A schematic illustrating the generation of VLPs and chimeric VLPs. A coat protein from a virus is cloned to an expression vector. The vector with the coat protein can also be used to insert a foreign peptide into the coat protein (bottom). Each vector is then transformed or transfected to an expression system where the proteins are expressed and assembled into VLPs.

Figure 2

The activation of immune responses by VLPs. Antigen-presenting cells phagocytose and process VLPs into fragments, which are presented to T-helper cells with the help of MHC class II (tope image). This leads to the activation of T-helper cells, which secrete cytokines that activate B-cells (below). B-cells are also activated by the cross-linking of B-cell receptors (BCRs) by VLPs. Activated B-cells divide and differentiate into plasma cells and memory cells (not shown here). Plasma cells secrete antibodies into the body, which neutralize the virus of interest from which the VLPs were derived. The figure is adopted from [5].