Porcine circovirus type 2 (PCV2) is associated with porcine circovirus diseases (PCVD), of which postweaning multisystemic wasting syndrome is considered to cause considerable economic losses in pig industry worldwide. As the virus-like particle (VLP) is a highly effective type of subunit vaccine and has unique advantages in terms of safety and immunogenicity, this study aimed to develop PCV2-like particles, which matched currently circulating Korean PCV2 and were applicable as vaccines. The ORF2 genes encoding PCV2 capsid protein were amplified from the PCV2 subgroup 1A/B Korean C275 isolate and the subgroup 2E C94 isolate by PCR assay with primer pair specific to PCV2 ORF2 gene, and were cloned into baculovirus transfer vector. Recombinant baculovirus was generated by cotransfection with the transfer vector and linear baculovirus DNA into the Sf9 cells, and then by plaque purification. Expression of PCV2 capsid protein was determined by the indirect immunofluorescence and Western blotting assays, and electron microscopy. By both immunological assays, PCV2 capsid antigen was detected in the Sf9 cells infected with the recombinant baculoviruses. The formation of empty virus particles, characteristic of VLP, was detected in the lysate of Sf9 cells infected with the recombinant baculoviruses by negative electron microscopy. From these results, VLPs of two genogroups of PCV2 were successfully expressed and generated in a baculovirus expression system. It is expected that the expressed VLPs of two genotypic groups can be used for control of PCV2 infection as good vaccine candidates.

Although several enteric viral pathogens including the porcine groups A, B and C rotaviruses (PGARV, PGBRV, and PGCRV), sapovirus (PSaV), and torovirus (PToV) are known to cause endemic diarrheas in weaning and post-weaning piglets, their precise prevalence in Korea is not clear. Therefore, we examined 1,222 diarrhea stools obtained from 627 farms during 2004～2009 by RT-PCR and/or nested PCR for evaluating their precise prevalence in Korea. PGARV was the predominant pathogen during 2004～2007 but its prevalence was markedly reduced during 2008～2009. PGBRV infections caused endemic diarrhea during 2004～2007, but was hardly detected during 2008-2009. PGCRV was detected at 27.0%, 14.5%, 42.4%, 28.8%, 7.3%, and 54.2% during each year of 2004～2009, respectively, indicating its high prevalence in Korea throughout the years. PSaV induced with high prevalence (32.4-39.2%) during 2004～2005 but its detection rate was markedly decreased during 2006～2009. PToV caused sporadic infections only during 2006 (1.0%) and 2007 (6.9%). These enteric viruses were detected in diarrhea specimens in piglets usually in combination with each other and/or together with bacterial pathogens including the Escherichia coli, Salmonella spp., Brachispira hyodysenteriae, and Lawsonia intracellularis. Infections with PGARV, PGCRV, PSaV, and PToV were more prevalent in fecal samples collected in cold seasons. These results provide important epidemiological data for the control and establishment of a surveillance system for the prevailing enteric viruses in Korea.