A water-soluble polysaccharide (WSPA) was isolated with alkali and purified from the mature stem of Physalis alkekengi L. WSPA (Mw=31kDa) was an acid heteropolysaccharide, which consisted of Rha, Ara, Xyl, Gal, Glc and GalA in ratio of 1.0:2.5:0.8:2.7:4.4:1.4. The results from structural analysis indicated backbone and branches of WSPA were composed of (1→3)-linked Glc, (1→3)-linked Gal, (1→2)-linked Xyl, (1→2)-linked Ara, and (1→2)-linked Rha residues. However, GalA was distributed only in the backbone of WSPA. All branches of WSPA were at O-2 of (1→6)-linked Gal and terminated with Glc. More importantly, it was found that WSPA significantly enhanced specific antibody IgG response with higher titers of IgG1 as well as IgG2b (p<0.05) in mice immunized with DNA vaccine. Therefore, WSPA can be considered as a potential adjuvant candidate in DNA vaccine.
Keywords: Adjuvant; DNA vaccine; Physalis alkekengi L.; Polysaccharide; Structure analysis.
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