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

Subunit vaccines can be classified as a type of inactivated vaccine that contains only part of the virus or other microorganisms. Subunit vaccines for pathogens can be generated as recombinant proteins in various expression systems, as long as appropriate immunogenic antigens of the target pathogen are empirically determined. The recombinant proteins can be a component of safe and non-replicating subunit vaccines. When manipulating DNA that encodes such proteins, a large quantity of proteins can be expressed, purified, and then immunized into a target host in order to stimulate immune reaction against the pathogen. In general, vaccination with antigens alone elicits weak immune responses so that potent adjuvant and repeated vaccinations are required. The high costs of producing subunit vaccines would deteriorate the competitiveness of such vaccine products compared to those of other types of vaccines. Despite such a limitation, several subunit vaccines have been launched on the market. Another type of subunit vaccine can be created via genetic engineering. A gene encoding immunogenic antigen is inserted into another carrier virus or into producer cells in culture system. When the carrier virus propagates or when the producer cells metabolize, the inserted gene is also expressed and released into cytoplasm. The end result of this approach is a recombinant vaccine; the immune system of vaccinated host will recognize the expressed protein and provide future protection against the target virus.