Ter-scale particles, but disaggregated 1516647 into single round particles at pH 7.0. The FTIR spectra of A.C.Tetracosactrin site NPs-legumain at pH 1.5 or 7 are presented in Fig. 3C. The band at 1736 cm21(pH 1.5) is assigned to -COOH of alginic acid because of hydrolysis of -NH-CO- I bond.Results Characteristics of A.C.NPs/C.NPs Loaded with Legumain DNAMorphology of A.C.NPs and C.NPs loaded with legumain DNA was analyzed by TEM. A.C.NPs-legumain were round, exhibiting a distinct alginic acid layer around the chitosan core when compared with the order ML 264 non-coated C.NPs-legumain (Fig. 2A). Size and zeta potential of the A.C.NPs-legumain were measured and compared with those of C.NPs-legumain at pH 7.0. As shown in Fig. 2B, C.NPs-legumain and A.C.NPs -legumain were 317619.3 nm and 341627.5 nm in diameter, respectively (Fig. 2B). The zeta potential of C.NPs-legumain was 0.7260.25 mV while the zeta potential of A.C.NPs-legumain was 215.662.32 mV (Fig. 2C). The FTIR spectra of C.NPslegumain and A.C.NPs-legumain are presented in Fig. 2D. The band at 1582 cm21 assigned to the stretching vibration of undeacetylated amido bond of chitosan, which shifted to 1579 cm21 in the alginic acid coated group. In addition, the 1619 cm21 peak is assigned to the -NH-CO- I bond produced by chitosan -NH2 and of alginic acid -COOH groups.A.C.NPs Protect DNA against Degradation in Simulated Gastric FluidWe further explored the effect of alginic acid modification on acid-resistance since A.C.NPs aggregate at relatively low pH levels. Agarose gel electrophoresis shows that after either 1, 2 or 4 h incubation in simulated gastric fluid (pH 1.5), the degradation of plasmid DNA loaded in the A.C.NPs was significantly less than naked plasmid DNA or plasmid DNA loaded in C.NPs (Fig. 4A, B). Even after 4 h of incubation, more than 78 plasmid DNA remained in A.C.NPs-legumain, while less than 19 and 2Chitosan NPs Loaded with Legumain DNA Vaccineremained in C.NPs-legumain and naked DNA plasmid group, respectively. These data suggested that A.C.NPs can effectively protect DNA against degradation in low pH conditions.A.C.NPs Increase DNA Uptake and Expression by Macrophages and Dendritic Cells in the Intestinal Peyer’s PatchesIn vivo uptake and expression by the macrophages and/or dendritic cells in the intestinal Peyer’s patches is a critical step for oral DNA vaccination. To visualize the uptake and expression of DNA carried by A.C.NPs or C.NPs into the Peyer’s patches, we loaded the nanoparticles with EGFP DNA plasmid. 15755315 
Immunofluorescence staining showed co-staining in EGFP (green) and F4/80 (red) cells (Fig. S1). Flow cytometry results showed that the percentage of EGFP+F4/80+ (Fig. 5A, C) and EGFP+CD11c+ (Fig. 5B, D) cells loaded with A.C.NPs were higher than either naked EGFP plasmid or those loaded with C.NPs. The percentage of EGFP+F4/80+ plus EGFP+CD11c+ amounted to 100 of EGFP positive cells in the three groups (Fig. 5E). This implies that macrophages or dendritic cells in the Peyer’s patches are the major sources of EGFP expression after oral DNA vaccination. Our data suggest that compared with C.NPs, A.C.NPs increase loaded DNA uptake and expression by macrophages and dendritic cells.2.75- and 3.91- fold higher number of activated T cells than when treated with C.NPs-legumain, empty A.C.NPs or PBS, respectively. Treatment with A.C.NPs-legumain group and legumain DNA with S. typhi. carrier group showed similar results. (Fig. 8A, B). An interesting additional finding was that the percentage of act.Ter-scale particles, but disaggregated 1516647 into single round particles at pH 7.0. The FTIR spectra of A.C.NPs-legumain at pH 1.5 or 7 are presented in Fig. 3C. The band at 1736 cm21(pH 1.5) is assigned to -COOH of alginic acid because of hydrolysis of -NH-CO- I bond.Results Characteristics of A.C.NPs/C.NPs Loaded with Legumain DNAMorphology of A.C.NPs and C.NPs loaded with legumain DNA was analyzed by TEM. A.C.NPs-legumain were round, exhibiting a distinct alginic acid layer around the chitosan core when compared with the non-coated C.NPs-legumain (Fig. 2A). Size and zeta potential of the A.C.NPs-legumain were measured and compared with those of C.NPs-legumain at pH 7.0. As shown in Fig. 2B, C.NPs-legumain and A.C.NPs -legumain were 317619.3 nm and 341627.5 nm in diameter, respectively (Fig. 2B). The zeta potential of C.NPs-legumain was 0.7260.25 mV while the zeta potential of A.C.NPs-legumain was 215.662.32 mV (Fig. 2C). The FTIR spectra of C.NPslegumain and A.C.NPs-legumain are presented in Fig. 2D. The band at 1582 cm21 assigned to the stretching vibration of undeacetylated amido bond of chitosan, which shifted to 1579 cm21 in the alginic acid coated group. In addition, the 1619 cm21 peak is assigned to the -NH-CO- I bond produced by chitosan -NH2 and of alginic acid -COOH groups.A.C.NPs Protect DNA against Degradation in Simulated Gastric FluidWe further explored the effect of alginic acid modification on acid-resistance since A.C.NPs aggregate at relatively low pH levels. Agarose gel electrophoresis shows that after either 1, 2 or 4 h incubation in simulated gastric fluid (pH 1.5), the degradation of plasmid DNA loaded in the A.C.NPs was significantly less than naked plasmid DNA or plasmid DNA loaded in C.NPs (Fig. 4A, B). Even after 4 h of incubation, more than 78 plasmid DNA remained in A.C.NPs-legumain, while less than 19 and 2Chitosan NPs Loaded with Legumain DNA Vaccineremained in C.NPs-legumain and naked DNA plasmid group, respectively. These data suggested that A.C.NPs can effectively protect DNA against degradation in low pH conditions.A.C.NPs Increase 
DNA Uptake and Expression by Macrophages and Dendritic Cells in the Intestinal Peyer’s PatchesIn vivo uptake and expression by the macrophages and/or dendritic cells in the intestinal Peyer’s patches is a critical step for oral DNA vaccination. To visualize the uptake and expression of DNA carried by A.C.NPs or C.NPs into the Peyer’s patches, we loaded the nanoparticles with EGFP DNA plasmid. 15755315 Immunofluorescence staining showed co-staining in EGFP (green) and F4/80 (red) cells (Fig. S1). Flow cytometry results showed that the percentage of EGFP+F4/80+ (Fig. 5A, C) and EGFP+CD11c+ (Fig. 5B, D) cells loaded with A.C.NPs were higher than either naked EGFP plasmid or those loaded with C.NPs. The percentage of EGFP+F4/80+ plus EGFP+CD11c+ amounted to 100 of EGFP positive cells in the three groups (Fig. 5E). This implies that macrophages or dendritic cells in the Peyer’s patches are the major sources of EGFP expression after oral DNA vaccination. Our data suggest that compared with C.NPs, A.C.NPs increase loaded DNA uptake and expression by macrophages and dendritic cells.2.75- and 3.91- fold higher number of activated T cells than when treated with C.NPs-legumain, empty A.C.NPs or PBS, respectively. Treatment with A.C.NPs-legumain group and legumain DNA with S. typhi. carrier group showed similar results. (Fig. 8A, B). An interesting additional finding was that the percentage of act.