Biomimetic phosphorus dendrimer multi-epitope nanovaccine enhances humoral and cellular immune response against African swine fever virus

Using nanoparticles (NPs) as a platform for multivalent antigen display is an effective strategy to increase the immunogenicity of subunit vaccines, which can induce high levels of humoral and cellular immunity. In addition, antigens that target antigen-presenting cells (APCs) can further increase their immunogenicity. To date, there are no commercially available ASFV vaccines available worldwide. The present study developed a dendritic cell (DC)-targeting ASFV biomimetic nanovaccine. First, a high-affinity and specific nanobody (Nb) targeting DCs was screened and expressed in tandem with B and T-cell epitopes of highly immunogenic p30, p54, p72, pB602L, and CD2V proteins of ASFV (Nb-rAg). The Nb-rAg complexes were then loaded onto azabisphosphonate-terminated phosphorus dendrimers (PPHs) to construct PPH-Nb-rAg NPs, which were subsequently coated with ASFV-infected activated porcine alveolar macrophage (PAM) membranes to prepare the PPH-Nb-rAg@PM biomimetic nanovaccine. Finally, the immune efficacy of the nanovaccine was evaluated in mice. Notably, compared with the PBS, rAg, Nb-rAg, and PPH-Nb-rAg immunization groups, the PPH-Nb-rAg@PM immunization group exhibited stronger ASFV antigen-specific humoral and cellular immune responses. Single-cell RNA sequencing (scRNA-seq) revealed that immunization with PPH-Nb-rAg@PM increased the proportions of B cells, T cells, NK cells, plasma cells, and macrophages in the mouse spleen. Further analysis revealed that PPH-Nb-rAg@PM immunization increased the numbers of memory B cells and plasma cells in the mouse spleen, and the numbers of CD4 + T cells, CD8 + T cells and NK cells also increased compared with those in the control group. These results suggest that PPH-Nb-rAg@PM is a promising and effective candidate vaccine against ASFV.