Virus-like particles (VLPs) are highly structured protein particles formed by the self-assembly of single or multiple structural proteins of viruses, which are morphologically and structurally similar to natural viral particles and have strong immunogenicity and biological activity。Compared to conventional attenuated vaccines, VLPs lack regulatory proteins and infectious nucleic acids, have no replication capacity, are structurally similar to viral particles, and retain strong immunogenicity. This implies that VLPs vaccines are characterized by high safety and immunogenicity, and are a rather promising vaccine development strategy.

VLPs can be classified into the following two types：

● Non-enveloped VLPs: Which are relatively simple structural VLPs consisting of single or multiple coat proteins that can be expressed in both prokaryotic and eukaryotic systems, such as human papillomavirus (HPV) VLPs vaccines.

Types of VLPs (Yan D et al., Applied microbiology and biotechnology, 2015)

Non-enveloped VLPs monomeric proteins are usually expressed in E. coli or yeast, two systems that have the advantage of high expression and easy amplification. Enveloped VLPs require the lipid membrane structure of the expressed cell line during self-assembly and release, and are only suitable for eukaryotic expression, of which the baculovirus system is predominant.

Preparation process of VLPs (Lua LH et al., Biotechnology and bioengineering, 2014)