A review of vaccine development and research for industry animals in Korea

Lee, Nak-Hyung; Lee, Jung-Ah; Park, Seung-Yong; Song, Chang-Seon; Choi, In-Soo; Lee, Joong-Bok

During replication of virus in eukaryotic cells, a virus has a unique characteristic of self-assembling into particles. This characteristic makes it possible to generate VLPs in cell culture system. VLPs are differentiated from live attenuated virus by the lack of productive viral infection. They are nonreplicating and non-pathogenic, and they mimic virus particles [42, 43] . VLP vaccines have been recognized as a relatively new concept in vaccine development. Since no genetic materials are required for forming VLP, no drawbacks shown in other vaccine strategies are observed, including virulence reversion, accidental mutation, and spontaneous re-assortment. Mammalian immune systems are highly attuned to recognize and attack these VLPs following injection [37, 42] . Since the conformational similarity of VLPs to infectious virions, a considerably low quantity of VLP antigen is sufficient to provoke a similar protective immunity. Additionally, VLPs have been shown to be highly effective at stimulating CD4 + T cell proliferation and a cytotoxic T lymphocyte response. The use of VLP would be a promising vaccination strategy for a variety of viruses [37] , since it can elicit high titer, long-lived immunity to diverse viruses. To date, VLPs have been produced for more than 30 different viruses that infect humans and other animals. However, all viruses cannot be applicable for forming VLP vaccines since conformational structures of each virus are variable, composed of either single or multiple capsids, and are with or without a lipid envelope. The major advantage of VLP vaccine presenting multiple viral epitopes on a single particle is the ability to effectively stimulate immune responses without serious deleterious effects induced by live attenuated virus vaccine [37] . Additionally, VLPs have the potential for activating both endogenous and exogenous antigen processing pathways leading to presentation of viral peptides by major histocompatibility complex (MHC) class I and II molecules. Nevertheless, better understanding for the replication feature of each virus is needed to generate VLP vaccines [42] .