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

The first DIVA vaccine was used to differ between infected and vaccinated pigs for pseudorabies [22] , demonstrating that vaccination reduces the transmissibility of wild type virus in a population as the result of shortening the duration of virus shedding in pigs upon experimental challenge infection. For bovine herpesvirus type 1 (BHV-1), in vaccination-challenge experiments, both a live and an inactivated glycoprotein E-negative DIVA vaccine and a glycoprotein Dsubunit DIVA vaccine have been demonstrated to reduce virus shedding after intranasal challenge of BHV-1 [23, 24] . For classical swine fever (CSF) that is the most significant contagious swine diseases over the world, attenuated CSF vaccine is used in countries where this disease is enzootic after an outbreak, but is not used for CSF free countries [25] . Subunit vaccine composed of gE was produced in the baculovirus expression system, along with a discriminatory enzyme-linked immunosorbent assay (ELISA) [26] . This DIVA vaccine can be used for emergency vaccination in the areas that CSF is newly developing, but it is not extensively used in the field. Another strategy utilized in countries with vaccinated pigs but no outbreaks any more, is to switch from live to subunit vaccine before completely stopping vaccination. This strategy would have applied in Korea, but may not be adopted in the future because World Health Organisation for Animal Health in May 2013 could announce that countries using live vaccines without outbreaks may be recognized as CSF-free countries. The potential DIVA vaccine for CSF virus (CSFV) was a gEdeleted pseudorabies virus vector that expressed the E2 subunit of CSFV [27] . This vaccine prevents the transmission of challenged CSFV to pig in contact with the vaccinated and challenged pigs. The differentiation of infected from vaccinated pigs can probably be based on a companion diagnostic test that detects only antibody against the viral protein E. In case of herpes virus, thymidine kinase (TK)-deleted virus is able to infect neurons but cannot replicate and then cause disease since the herpes virus requires TK to return from latency. Such vaccine confers effective protection and blocks http://www.ecevr.org/ http://dx.doi.org/10.7774/cevr.2012.1.1.18 cell invasion by virulent virus and prevents establishment of a persistent carrier status. These gene-deleted vaccines for Aujeszky's diseases (AD) have been used in Korea, the US and the part of the EU, which contributed to eradication of AD. The DIVA concept used in veterinary vaccines may prove to be an important and useful strategy for the future development of human vaccines [21] .