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Porcine circovirus is a nonenveloped, single-stranded, circular-genome DNA virus belonging to the family Circoviridae. Porcine circovirus-1 (PCV-1) was first isolated as a non-pathogenic contaminant virus from a porcine kidney cell line.17 In contrast, Porcine circovirus-2 (PCV-2) was first recognized as a causative agent of postweaning multisys-temic wasting syndrome (PMWS), a multifactorial disease in swine first identified in Canada in 1991.6 Subsequently, PCV-2 has been reported in most intensive pig-producing countries worldwide including Thailand.16 The genome of PCV-2 contains 3 major open reading frames (ORFs): ORF1, ORF2, and ORF3. ORF1 encodes the Rep proteins of 35.7 kDa involved in viral replication, ORF2 encodes the struc-tural capsid protein of 30 kDa involved in immunogenicity of PCV-2,12 and ORF3 protein is involved in PCV-2–induced apoptosis.9 The most reliable serological diagnostic assays for anti-body detection against PCV-2 consist of immunoperoxidase monolayer assays1 (IPMAs) and indirect fluorescent anti-body tests2 (IFATs). However, these conventional assays are expensive, highly time-consuming, and carry the risk of virus contamination, whereas commercially available enzyme-linked immunosorbent assays (ELISAs) based on a recombinant capsid protein expressed in baculovirus expres-sion systems3 or bacterial expression systems11,15 are more convenient. Furthermore, the production of recombinant proteins in the eukaryotic expression system is costly. It should be noted that several antigenic epitopes of PCV-2 capsid protein were demonstrated at amino acid residues 47–85, 165–200, 230–2338 and 65–87, 113–147, 157–183, 193–207,10 whereas a 2011 report5 demonstrated that the rec-ognition epitope was also located in the nuclear localization signal (NLS) of capsid protein at amino acid residues 26–36. Nevertheless, most information of antigenic epitopes of PCV-2 suggested that the NLS region might not be the major domain for the conformational epitopes. As a result, in the current study, a recombinant NLS truncated capsid (rntCap