In vitro and in vivo studies of deglycosylated chimeric porcine reproductive and respiratory syndrome virus as a vaccine candidate and its realistic revenue impact at commercial pig production level.

Porcine reproductive and respiratory syndrome virus (PRRSV) causes major economic losses in the swine industry worldwide. Vaccination is the most effective method to control the disease. In a previous study, a chimeric PRRSV named as K418 which had a genome composed of ORF 1 from the FL12 strain and ORF 2-7 from the Korean representative LMY strain was created. We constructed K418DM, K418 with deglycosylated glycoprotein 5 (GP5), to improve its humoral immunity. In the follow-up on in vivo and in vitro virological and serological tests, no back mutation in amino acids of GP5 associated with deglycosylation was shown after 9 passages on MARC-145 cells, whereas only one case of back mutation was detected after single passage in pig. In serological study, K418DM induced higher serum neutralization (SN) antibody and more limited viremia compared with those of K418 virus. In clinical trial and economic analysis, the K418DM elicited SN antibody titers and PRRSV-specific IgG over protection limit. From the economic viewpoint, there was statistically significant reduction in percentage of weak pigs. These results indicated that vaccination with the K418DM may provide enhanced protection for pigs in PRRS endemic situation and increase growth performance in commercial pig farms.

Comparative genome analysis and molecular epidemiology of the reemerging porcine epidemic diarrhea virus strains isolated in Korea.

Porcine epidemic diarrhea virus (PEDV), a member of the Coronaviridae family, is an enveloped, positive-sense, single-stranded RNA virus, which causes severe diarrhea and dehydration in suckling pigs. We detected three PEDV strains from ten small intestine samples from piglets with acute diarrhea and we determined the complete genome sequences of the reemerging Korean PEDV field isolates, except for the noncoding regions from both ends. The complete genome sequences of the strains were identical or almost identical (one synonymous single-nucleotide polymorphism (SNP) in the ORF1a/1b genomic sequence). Interestingly, comparative genome analysis of recent Korean PEDV isolates and other strains revealed that the complete genome sequences of recent Korean strains were almost identical (99.9%) to those of the US PEDV strains isolated in 2013. These results suggest that the three reemerging Korean strains are distinct from previous endemic Korean PEDV strains and has been recently introduced into Korea from oversea with high likelihood.