title: Immunogenicity and immunoprotection of porcine circovirus type 2 (PCV2) Cap protein displayed by Lactococcus lactis.
abstract: The capsid (Cap) protein, an important immunoprotective protein of porcine circovirus type 2 (PCV2), was expressed on the cell surface of the Gram-positive food-grade bacterium, Lactococcus lactis. Cap protein was fused to the peptidoglycan binding domain (known as the protein anchor domain, PA) of the lactococcal AcmA cell-wall hydrolase. The Cap protein fusion was non-covalently rebound to the surface of non-genetically modified, non-living high-binder L. lactis cells (designated Gram-positive enhancer matrix (GEM) particles). Expression of the recombinant GEM-displaying capsid protein (GEM-PA-Cap) was verified by Western blotting and immunofluorescence and transmission electron microscopy assays. To evaluate the immunogenicity of the recombinant Cap protein (rCap), 20 PCV2-seronegative piglets were immunized with the GEM-PA-Cap subunit vaccine, GEM alone, or phosphate-buffered saline (PBS, challenge control and empty control). Each group consisted of five piglets. The results showed that the level of PCV2-specific antibodies in piglets immunized with the GEM-PA-Cap subunit vaccine was significantly higher than that of the piglets immunized with GEM alone or the control group at all the time points post-vaccination (P<0.01). After challenge with the PCV2 wild-type strain, piglets that received the GEM-PA-Cap subunit vaccine showed significantly higher average daily weight gain (DWG) and shorter fever duration than the other two groups (P<0.001). Furthermore, a significant reduction in the gross lung lesion scores and lymph node lesion scores was noted in the GEM-PA-Cap-immunized group compared with the scores of the GEM or PBS-treated group (P<0.01). The results suggest that recombinant rCap displayed by L. lactis GEM particles provided the piglets with significant immunoprotection from PCV2-associated disease. Thus, the novel GEM-PA-Cap subunit vaccine has potential to be considered an effective and safe candidate vaccine against PCV2 infection in piglets.
authors.affiliation: National Research Center of Engineering and Technology for Veterinary Biologicals, Jiangsu Academy of Agricultural Science, Nanjing 210014, Jiangsu Province, China.
authors.forename: Peng-Cheng
authors.initials: PC
authors.lastname: Li
authors.affiliation: National Research Center of Engineering and Technology for Veterinary Biologicals, Jiangsu Academy of Agricultural Science, Nanjing 210014, Jiangsu Province, China.
authors.forename: Xu-Wen
authors.initials: XW
authors.lastname: Qiao
authors.affiliation: National Research Center of Engineering and Technology for Veterinary Biologicals, Jiangsu Academy of Agricultural Science, Nanjing 210014, Jiangsu Province, China.
authors.forename: Qi-Sheng
authors.initials: QS
authors.lastname: Zheng
authors.affiliation: National Research Center of Engineering and Technology for Veterinary Biologicals, Jiangsu Academy of Agricultural Science, Nanjing 210014, Jiangsu Province, China. Electronic address: houjibo@jaas.ac.cn.
authors.forename: Ji-Bo
authors.initials: JB
authors.lastname: Hou
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D036022:Capsid Proteins / Q000276:immunology*; D018173:Circoviridae Infections / Q000517:prevention & control / Q000662:veterinary*; D017925:Circovirus; D056724:Immunity, Humoral; D013294:Lactococcus lactis; D008168:Lung / Q000473:pathology; D011994:Recombinant Proteins / Q000276:immunology; D013552:Swine; D013553:Swine Diseases / Q000517:prevention & control*; D022223:Vaccines, Subunit / Q000276:immunology; D014765:Viral Vaccines / Q000276:immunology*
chemical_list: D000914:Antibodies, Viral; D036022:Capsid Proteins; D011994:Recombinant Proteins; D022223:Vaccines, Subunit; D014765:Viral Vaccines
keywords: Cap protein; Lactococcus lactis; PCV2 subunit vaccine; Porcine circovirus type 2; Surface display