Nanoparticle orientationally displayed antigen epitopes improve neutralizing antibody level in a model of porcine circovirus type 2

Ding, Peiyang; Zhang, Teng; Li, Yafei; Teng, Man; Sun, Yaning; Liu, Xiao; Chai, Shujun; Zhou, Enmin; Jin, Qianyue; Zhang, Gaiping

Antibodies against PCV2 were part of the antibody against Cap protein. The candidate vaccine used in animal experiments contained large amounts of uncoupled Cap protein (99.4%). Carbopol and Freund's adjuvant are highly efficient adjuvants and can significantly increase IgG levels against Cap. Therefore, there was no significant difference in the levels of IgG between the Cap and Cap-AuNP groups when using Carbopol and Freund's adjuvant ( Figure 6A ). High levels of antibody against PCV2 require epitopes on the surface of PCV2 to be fully recognized by APCs. Cap protein that binds to the surface of AuNPs can be efficiently recognized, swallowed, processed, and presented by APCs and plays a central role in activating immune response. Therefore, there was significant difference in the level of IgG against PCV2 between the Cap group and the Cap-AuNPs group when using Carbopol and Freund's adjuvant ( Figure 6B ). Our previous experiments (data not shown) have confirmed that CpG weakly promoted the levels of anti-Cap and PCV2 IgG. Moreover, CpG had a synergistic effect with AuNPs and markedly enlarged immune effect. However, AuNPs played a key role rather than CpG. Similar results have been found by Tao et al. 36 Thus, when CpG was used as adjuvant, there was a significant difference between the Cap and Cap-AuNPs groups for IgG against Cap and PCV2 ( Figure 6A and B) .