Abstract
Herbal polysaccharides and their modifiers used as vaccine adjuvants have been widely investigated due to their safety and good immunoenhancing activity. In this study, the 50% ethanol concentration precipitated Lagenaria siceraria(Molina) standl polysaccharide (LSP50) and sulfated modified LSP50 (sLSP50) was prepared, and their characterization was investigated. LSP50 and sLSP50(-1.5) were used as vaccine adjuvants to immunize chickens, and the strength and type of immune responses induced by different adjuvants were detected. Our results showed that LSP50 was homogeneous polysaccharides, and the carbohydrate content was 98.6%. The sLSP50(-1.5) with the DS value of 1.5 was optimized by response surface methodology. The sLSP50(-1.5) has both characteristics of polysaccharide functional groups and sulfate functional groups. Adjuvant activity of LSP50 and sLSP50(-1.5) showed that LSP50 and sLSP50(-1.5) could induce long-lasting and high hemagglutination (HI) titers, antigen-specific lgG-NDV antibody, splenic lymphocyte proliferation, high immune organ index. Moreover, chicken immunized with sLSP50(-1.5) showed a strong mixed Th1-type (IFN-γ and TNF-α) and Th2-type (IL-4 and IL-6) cytokines expression. Thus, these findings demonstrated that sLSP50(-1.5) as a vaccine adjuvant can induce a mixed cellular and humoral immune response and can potentially serve as an effective vaccine adjuvant for NDV antigen.