Indirectly loaded exosomes induce a potent memory response to OVA that is distinct from the response obtained with other adjuvants. All primed mouse groups were boosted with 50 μg OVA alone per mouse 4 weeks later and bled 7 days after boosting. The presence of OVA-specific (A) IgG, (B) IgG1, and (C) IgG2a antibodies was detected by ELISA using serial dilution of the sera. The results from the 1:2700 dilutions are presented, showing OD (A 405 nm) values for each subject and the mean. Significant differences between groups after nonparametric Mann-Whitney U test are depicted with asterisks: *P < .01, **P < .002.