Fig. 4: SNAP-OMVs decorated with biotin-GFP boost GFP-specific IgG titers.

a Mean GFP-specific IgG titers (horizontal black lines) in endpoint (day 56) serum of individual mice in each group (gray circles). Five groups of six-week-old BALB/c mice (seven mice per group) were immunized s.c. with the following: PBS, blank SNAP-OMVs, SNAP-OMVs mixed with 20 pmol unbiotinylated or biotinylated GFP, and ClyA-GFP OMVs displaying a ClyA-GFP fusion. All OMVs were isolated from KPM404 ΔnlpI cells with the appropriate expression plasmid. Mice received prime injections containing an equivalent amount of OMVs (20 μg total protein) on day 0 and were boosted on day 21 and 42 with the same doses. b Mean GFP-specific IgG1 and IgG2a titers in the same endpoint serum of individual mice in select groups from (a). c Mean GFP-specific IgG titers in mice receiving SNAP-OMVs formulated with escalating doses (2–200 pmol) of biotinylated GFP (physically associated, dark gray circles) or non-biotinylated GFP (non-associated mixtures, light gray circles). An equivalent amount of SNAP-OMVs was used in each case. Dashed black line indicates mean GFP-specific IgG titer of blank SNAP-OMV control group. Data are the mean titers of 6 mice in each group ± SD. Statistical significance was determined by two-tailed t test with Welch’s correction (*p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001; ns not significant). Actual p values in (a) from left-to-right: p < 0.0001, p < 0.0001, p = 0.0013, and p = 0.2751. Actual p values in (b) from left to right: p < 0.0001  and p = 0.5184 . Actual p values in (c) from left-to-right: p = 0.1401, p = 0.0001, p < 0.0001, p < 0.0001, p = 0.4719, p < 0.0001, p < 0.0001, p = 0.0413, p = 0.0022, p = 0.0072, p = 0.0654, p < 0.0001, p = 0.0004. Source data are provided as a Source Data file.