High-Yield Production of PCV2 Cap Protein: Baculovirus Vector Construction and Cultivation Process Optimization

Porcine circovirus type 2 (PCV2) infection causes porcine circovirus disease (PCVD), a global immunosuppressive disease in pigs. Its clinical manifestations include post-weaning multisystemic wasting syndrome (PMWS) and porcine dermatitis and nephropathy syndrome (PDNS), which cause significant economic losses to the swine industry. The Cap protein, which is the major protective antigen of PCV2, can self-assemble to form virus-like particles (VLPs) when expression in the insect baculovirus expression system. Few studies have compared the expression of Cap proteins in different baculovirus expression systems. In this study, we compared two commonly commercialized baculovirus construction systems to expressing the Cap protein in various insect cells. The results demonstrated that the flashBAC system expressing Cap protein at higher levels than the Bac-to-Bac system. Notably, when expressing four copies of the Cap protein, the flashBAC system achieved the highest protein yield in High Five cells, reaching 432 μg/mL at 5 days post-infection (dpi) at 27°C cultivation. Animal experiments confirmed that the purified Cap protein effectively induced specific antibody production in mice and swine. This study provides critical data for optimizing the production of PCV2 Cap protein, which is of great significance for reducing the production cost of PCV2 vaccines and improving industrial production efficiency.