Development of a subunit vaccine and Diagnostic assays against porcine circovirus type 2

Abstract

Porcine circovirus type 2 (PCV2) was first recognized as a causative agent of porcine circovirus associated diseases (PCVAD) in Canada in 1991. Subsequently, PMWS has become a major economic problem to the swine industry worldwide including Thailand. Importantly, virological, serological study and also development of vaccine and serological assay are useful for prevention and control of PCVAD. Genetic characterizations of PCV2 isolates from Thai pigs with PCVAD during 2007-2010 revealed that all recent Thai PCV2 sequences belong to genotype 1 (PCV2b) and subgroup 1A/B was predominated in this study. Later, an indirect ELISA was developed and validated for PCV2 antibody detection using a recombinant truncated capsid (rntCap) protein from PCV2b genotype expressed in E. coli system. Swine serum samples were obtained and tested using the indirect ELISA comparing with IPMA as a gold standard for serological assay. The results demonstrated that the diagnostic sensitivity, specificity and accuracy of a developed indirect ELISA are 98.33%, 93.33% and 96.67%, respectively. Finally, the efficacy of a developed subunit PCV2b vaccine using a rntCap protein expressed in E. coli was determined in PCVAD-affected farm. The results indicated that vaccination by a developed subunit PCV2b vaccine could induce specific antibody and partially control PCV2 viral load in serum suggesting that using higher protein concentration dose and/or using an appropriate adjuvant could enhance the better efficacy.