Development and application of a baculovirus-expressed capsid protein-based indirect ELISA for detection of porcine circovirus 3 IgG antibodies

Abstract

Background Porcine circovirus type 3 (PCV3), recently widely isolated from pigs with various clinical conditions, is likely globally epidemic. However, development of serological diagnosis for PCV3 in pigs is ongoing. Our objectives were to: 1) establish an indirect ELISA, using PCV3 capsid protein (Cap) prepared by Baculovirus Expression Vector System (BEVS) as a high-quality coating antigen for detection of PCV3-associated antibodies in serum samples; and 2) use this ELISA to conduct a serological survey for PCV3 in various regions of Hunan province, China. Results The PCV3 positive rate to the ELISA assay (total of 190 serum samples) was higher in sows with reproductive failure compared to healthy sows (34/85, 40.0% versus 30/105, 28.6%), with similar results using qPCR assays. Further, in an additional 1038 serum samples collected from January 2016 to May 2018 in various regions of Hunan province and tested with this established ELISA, 20 to 84% were positive for PCV3 (according to region of sera collection), with high PCV3 seroprevalence (> 50%) in herds in Changde, Hengyang and Yueyang. Moreover, among serum samples from herds in Shaoyang and Changde, PCV3 seroprevalence was higher in sows than in other classes of pigs (i.e., suckling piglets, nursery pigs, gilts, growing-finishing pigs and boars). Conclusions We developed a full-length PCV3 Cap-based ELISA using a eukaryotic expression system with excellent potential to elucidate PCV3 epidemiology. Based on this assay, PCV3 has been circulating in Hunan province. PCV3 prevalence was lower in healthy sows than in those with reproductive failure. Further studies are warranted to identify the PCV3 responsible for high seroprevalence in sows and determine pathogenesis of PCV3 in sows with reproductive failure. Electronic supplementary material The online version of this article (10.1186/s12917-019-1810-3) contains supplementary material, which is available to authorized users.

Pathogenicity and immune response against porcine circovirus type 3 infection in caesarean-derived, colostrum-deprived pigs

“…Information related to PCV3 immune response is scarce, and field studies have shown high seroprevalence in growerfinisher, varying from 22-80 %, while seroprevalence in sows could reach 96 % [19,20], indicating a high level of virus circulation. However, the protective role of PCV3-induced antibodies is unknown and different isotypes could have a different role in viral neutralization.…”

“…B-cell epitopes located in the Cap protein (amino acid residues 93-103, 109-146, 170-181 and 192-202) and T-cell epitopes (amino acid residues 101-109, 113-121, 172-180 and 201-210) were predicted using the immune epitope database analysis resource (IEDB) [15]. In addition, recent studies have indicated the predicted potential linear epitope in the nuclear localization signal (NLS) sequence of the capsid [19]. However, the detection of PCV3 antibodies in swine sera has been successfully accomplished using the bacteria-expressed PCV3 capsid protein without NLS [3,20].…”

“…Information related to the PCV3 immune response is scarce. Although serological field studies demonstrated that PCV3 could induce a robust humoral response [19,20], the role of viral components in the cellular or humoral response is unknown. B-cell epitopes located in the Cap protein (amino acid residues 93-103, 109-146, 170-181 and 192-202) and T-cell epitopes (amino acid residues 101-109, 113-121, 172-180 and 201-210) were predicted using the immune epitope database analysis resource (IEDB) [15].…”

Self-assembly into virus–like particles of the recombinant capsid protein of porcine circovirus type 3 and its application on antibodies detection

“…For example, PCV2 VLPs are used as coating antigens to be able to detect serum neutralizing antibodies (SNAbs) in ELISA (Nainys et al 2014;Zhang et al 2016). Currently, PCV3 Cap proteins harvested from insect cells or E. coli have been used as antigens to detect PCV3-specific antibodies in an ELISA (Deng et al 2018;Zhang et al 2019). There is still lacking a VLP-based serological diagnosis method for PCV3.…”

Novel polymerase spiral reaction assay for the visible molecular detection of porcine circovirus type 3

“…Conventional serological methods have been used to identify PCV3. These methods include an enzyme-linked immunosorbent assay that can accurately detect the viruses, but it can be time-consuming [14, 15]. Molecular methods based on polymerase chain reaction (PCR) assays, both routine and quantitative, have been developed to monitor and detect PCV3 rapidly and specifically [16–18].…”