Adjuvant effect enhancement of porcine interleukin-2 packaged into solid lipid nanoparticles

In this paper, we investigated the enhancement of adjuvant effects of porcine IL-2 (pIL-2) by packaging it into a solid lipid nanoparticle (SLN) delivery system. SLN–pIL-2 was prepared using hydrogenated castor oil and Polylactide-co-glycolide by double emulsion solvent evaporation methods (w/o/w). In animal trials, BALB/c mice were immunized with inactivated foot and mouth disease virus (FMDV) antigen combined with the SLN–pIL-2 adjuvant on days 0 and 14. Antibody titer, splenocyte proliferation, and secretion of IFN-γ and IL-4 cytokines were determined. Our results showed that SLN–pIL-2 could significantly enhance FMDV-specific antibody level compared with recombinant pIL-2 alone (p < 0.05). In addition, SLN–pIL-2 significantly increased the proliferative responses of antigen-specific spleen cells. Furthermore, SLN–pIL-2 induced the secretion of IFN-γ at a level higher than that induced by recombinant pIL-2 alone. Our results indicate that packaging recombinant pIL-2 in SLNs can be an effective way of boosting the effectiveness of pIL-2 as an adjuvant to enhance immune responses of vaccines.