Ferritin nanoparticles significantly enhance the immune response to the African swine fever virus p34 protein.

BACKGROUND

African swine fever (ASF) is a highly contagious disease, and the core-shell protein p34 is an important antigen that can induce immune responses. The use of ferritin nanoparticles for the orderly and repetitive display of antigens on the particle surface can improve the immunogenicity of subunit vaccines. Here, we used the SpyCatcher/Spytag system to conjugate ferritin nanoparticles with the p34 protein (F-p34).

RESULTS

The N-terminus of ferritin was conjugated to a truncated SpyCatcher (SC-ferritin). The antigen of ASFV p34 was linked to SpyTag (p34-ST). SC-Ferritin and p34-ST were expressed in E. coli and purified via CaptoTM Core 700 and Ni-NTA columns, respectively. Based on the isopeptide bonds formed between SpyCatcher and SpyTag, p34 linked to SpyTag was readily surface-displayed on SC-ferritin via in vitro covalent conjugation (F-p34). F-p34 can be taken up by bone marrow dendritic cells (BMDCs) and effectively stimulate BMDC maturation. Compared with the monomeric p34 protein, in vivo studies confirmed that the recombinant F-p34 nanoparticle can induce more robust T-cell responses and stronger specific IgG antibody responses against ASFV. Moreover, F-p34 can increase serum cytokines, which is also significantly greater than that of the p34 protein. These results indicate that the recombinant nanoparticles can induce not only humoral immune responses but also cellular immune responses. In addition, there were no significant pathological changes in the heart, liver, spleen, lung or kidney tissue sections of the mice immunized with F-p34, demonstrating that the recombinant nanoparticles exhibit favorable histocompatibility or safety.

CONCLUSIONS

These results demonstrate that we successfully designed a recombinant plasmid and obtained a recombinant protein through the prokaryotic expression system of E. coli. The covalently coupled recombinant F-p34 nanoparticles significantly increased the antigenicity of p34 and contributed to research on African swine fever subunit vaccines.