Immunopotentiation mechanism of a mannose-modified peptide fragment containing a dominant antigenic epitope of Micropterus salmoides rhabdovirus (MSRV) glycoprotein after coupling to nanocarrier

Micropterus salmoides rhabavirus (MSRV) is an important pathogen that threatens the aquaculture of bass farming worldwide, and the efficacy of vaccines developed against this pathogen still needs to be improved. In order to further enhance the immune efficacy of existing vaccines, a mannose-modified nanovector vaccine SWCNTs-M-G2 was constructed by screening for peptide fragments encoding highly immunogenic antigenic epitopes (G2) and mannose modifications. Mannose receptor (MR) is abundantly expressed on the surface of Antigen-presenting cells (APCs) and plays a role in recognizing pathogens and presenting antigens. In this study, the effect of mannosylated modification on the immunopotentiation of highly immunogenic peptide fragments was investigated by using the characteristics of MR-specific recognition of mannose and APCs surface. In vitro macrophage assays showed that SWCNTs-M-G2 was efficiently phagocytosed and taken up by largemouth black bass head kidney macrophages, and effectively stimulated macrophage activation and upregulated the secretion of macrophage cytokines IL-1 beta, IL-8 and IL-12. In vivo, SWCNTs-M-G2 was also shown to be better taken up by immune organs such as spleen and head kidney, and induced increased expression of IL-1 beta, IL-8 and IL-12 in the immune organs of Micropterus salmoides, and promoted the expression of TCR and CD4 molecules in specific immune cells. Meanwhile, in vivo fluorescence imaging revealed that SWCNTs-M-G2 could be in the immune organ of fish for a longer period of time, contributing to the efficient uptake of antigens. Finally, the challenge test showed that SWCNTs-M-G2 could mediate the production of specific antibodies at a higher level than the unmodified carrier vaccine SWCNTs-G2 and showed a higher relative immune protection rate.