Development of modern immunizing agent against porcine circovirus type 2 infection based on chimeric VP1-PCV2bCap recombinant protein

Abstract Porcine circovirus type 2 is the main causative agent of post-weaning multisystemic wasting syndrome, which affects the immune system of swine and causes widespread epidemics in livestock farms resulting in significant piglet mortality and economic losses every year. Although several commercial vaccines were developed, the efficiency and safety need to be improved. Therefore, we have engineered the chimeric complex containing PCV2bCap protein based on virus like particles (VLPs) and the mouse polyomavirus (MPyV) as VLPs represent modern and safe alternative of classical vaccine with high B cells stimulating activity. The ability of this complex to induce an immune response in both mouse and pig models in vivo were evaluated. Firstly, experimental mice were divided into 4 groups and immunized with sterile buffer and VP1-PCV2bCap with different adjuvants, the immune response was monitored for 10 weeks. Robust immune response was detected after the first immunization and gradually increased after the second and third dose, especially in mice immunized by recombinant protein with Emulsigen (10%) as an adjuvant. Subsequently, to confirm the vaccine efficacy in a target organism, 8-week-old piglets were immunized with VP1-PCV2bCap protein with Emulsigen (10%). The levels of anti-PCV2b specific IgG antibodies were significantly increased in piglets after the second immunization. Finally, strong neutralizing activity of these antibodies was confirmed in PK-15 cells infected with PCV2 Stoon 1010. VP1-PCV2bCap protein complex appears as a promising candidate vaccine for preventing disease associated with PCV2 infection in pigs.