Production of virus-like particles of porcine circovirus type 2 in baculovirus expression system and its application for antibody detection

Backgroud Porcine circovirus type 2 (PCV-2) infection is a growing and persistent threat to the swine industry, and thus the development of serological detection methods for PCV2 is of great necessity for clinical diagnosis, as well as epidemiological investigations. The study aimed to build an indirect enzyme-linked immunosorbent assay (ELISA) to examine antibodies against PCV2 based on virus-like particle (VLP). Results Through transmission electron microscopy (TEM), the VLPs were morphologically similar to authentic PCV-2 viruses. Purified VLPs can be detected in immunoblots with PCV-2 antisera, and a predominant protein of approximately 30 kDa was determined by Western blot. The VLPs were shown to have good immunogenicity in mice and stimulated a high level of PCV2-specific antibody titers. The indirect ELISA can detect PCV2 antibody responses in animals had a diagnostic sensitivity and specificity of 98.33% and 93.33% compared to immunofluorescence assay (IFA), respectively. The intra-assay and inter-assay coefficient variations (CVs) within a plate was <10%, and the CV of different ELISA plates was <15%, indicating good repeatability. There was no cross-reaction of this ELISA with antisera against other porcine viruses. A total of 170 serum samples collected from different pig farms in China were tested for anti-PCV2 antibodies, and 151 (88.9%) of the 170 samples were PCV2 antibody positive. Conclusion Our findings suggest that this ELISA assay was rapid, specific, and reproducible and can be used for large-scale serological investigations of PCV2 antibodies in pigs.