Figure 7. Enhanced immunogenicity of HA-ferritin over soluble HA does not translate to nonhuman primates.

Pigtail macaques (n = 5) were vaccinated once intramuscularly with HA-ferritin (15 μg) or a molar equivalent of soluble HA (11.25 μg), both adjuvanted with AddaVax. A control group received AddaVax alone (n = 2). (A) Serum IgG titers against HA were measured by capture ELISA at 0, 7, and 21 days after vaccination. The dashed line indicates detection cutoff (1:100 dilution). Data represent mean ± SD. (B) At day 21, draining and nondraining LNs were harvested. The proportion of T_FH cells (identified as CXCR5⁺PD-1⁺) within CD4⁺ T cells and (C) their expression of transcription factor Bcl6 and proliferation marker Ki-67 were determined. (D) The proportion of CD20⁺IgM^–IgD^–IgG⁺ B cells involved in LN GCs (identified as Bcl6⁺Ki-67⁺). (E) Flow cytometry plots showing HA specificity of these GC B cells in draining LNs measured using dual probes of biotinylated PR8 HA labeled with streptavidin-fluorophores. Data collected from 1 experiment. Analyzed using a Mann-Whitney U test (A) or Wilcoxon’s matched-pairs signed-rank test (B–D).