4). When the mice were immunized with SEZ ΔhasB, there was an absence of antibody elicited against capsid protein (0.135 ± 0.007) but a high-level antibody response with the inactive PCV2 vaccine (1.204 ± 0.157). A significant level of antibody (0.629 ± 0.116) could be induced by the recombinant strain compared with the AZD6244 datasheet negative control, indicating that the cap gene was expressed during the course of
immunization. Diseases associated with PCV2 infections are becoming a major problem for the swine industry worldwide. Commercially available and currently developed vaccines focus on the Cap protein, and these include DNA vaccines (Kamstrup et al., 2004; An et al., 2008) and virus-vectored vaccines (Ju et al., 2005; Wang et al., 2007; Fan et al., 2008a). However, producing a sufficient amount of DNA/viral for vaccine development is relatively expensive. To overcome this problem, heterologously expressing Cap protein through attenuated swine pathogenic bacteria is an attractive route: it is cost effective compared with DNA/viral vector-based
vaccines, and the swine bacterial vector benefits selleck inhibitor the recombinant strain against other bacterial infection simultaneously compared with yeast (Bucarey et al., 2009) and Lactococcus lactis (Wang et al., 2008) vectors. Kim et al. (2009) used an aroA mutant of Bordetella bronchiseptica, which efficiently colonized ciliated respiratory mucosa of pigs, as a live vaccine vehicle for Cap protein expression. Results in mice and pigs showed that this bacterial vehicle could elicit an immune response against Cap protein and was effective in preventing PCV2 multiplication in pigs. Unfortunately, the kanamycin-resistant gene used for mutant selection was still present in the B. bronchiseptica
genome, limiting its spread in the field. The SEZ-Cap recombinant stain was a more promising vaccine candidate. Therefore, SEZ rather than B. bronchiseptica coincident with PCV2 plays an important Tacrolimus (FK506) role in respiratory infection development in the swine industry (Metwally et al., 2010), and the recombinant strain was constructed without any resistant marker. In addition, the Cap protein was stably expressed on SEZ at transcriptional and translational level both in vitro and in vivo. Real-time PCR showed that the cap gene could transcript at the same level as the substitutive szp gene, either in TSB culture or during the course of infection in mice. FACS and immunofluorescence microscopy analysis demonstrated that Cap protein could be displayed on the surface of SEZ. Almost all SEZ-Cap immune sera showed a higher S/P value than negative sera assessed by enzyme-linked immunosorbent assay, which indicated that the Cap protein was expressed in vivo and most individuals were able to mount an immune response against this protein. The two conditions above were indispensable to a successful vaccine.