Fig. 5: Antigen presentation and germinal center responses in drainage lymph nodes induced by ICO-RBD nanovaccines.

a ICO-RBD nanovaccine accumulation in lymph nodes. BALB/c mice were intramuscularly immunized with Cy5.5-labelled RBD monomers (SpyCatcher-RBD proteins) or Cy5.5-labelled ICO-RBD nanovaccines. After different time intervals, the inguinal lymph nodes were obtained and then fluorescence imaging was performed (n = 4 mice).b Immunofluorescence detection of inguinal lymph nodes on day 1, 3 and 5. Green, CD11C⁺ DCs; Red, Cy5.5-labelled RBD. Scale bar, 200 μm. c Percentages of CD21/CD35⁺Cy5.5⁺ follicular DCs in CD11C⁺ DCs in the inguinal lymph nodes after different time up to 14 days, as detected using flow cytometry (n = 4 mice). d Schematic illustration of the experiment schedule to analyze germinal center responses. BALB/c mice were randomly divided into PBS, RBD and ICO-RBD groups. The inguinal lymph nodes were harvested at week 1, 2 and 3 after priming immunization. e Percentages of T_FH cells (CXCR5⁺PD1⁺) in CD4⁺ cells, GC B cells (CD95⁺GL7⁺) in CD19⁺B220⁺ cells and plasma cells (CD44⁺CD138⁺), as detected using flow cytometry (n = 8 mice).f Immunofluorescence detection of inguinal lymph nodes on week 5. The mice were intramuscularly immunized with two doses of 50 μL nanovaccines containing 1 μg SpyCatcher-RBD at week 0 and 3, mixed with 50 μL AddaVax. The white circles indicate the germinal centers, in which there are B220⁺GL7⁺ GC B cells. Scale bar, 200 μm. These experiments (b, f) were repeated three times independently with similar results. The data were processed on GraphPad Prism 8 and are presented as the mean ± SD. Statistical significance (P value) was calculated by one-way ANOVA followed by Tukey’s test. *P < 0.05; **P < 0.01^; ***P < 0.001. Source data are provided as a Source Data file.