Studies On Ginseng Polysaccharide As An Adjuvant For Inactivated H1N1 Influenza Vaccine

People began to exploit influenza vaccine in the 1930s, but till now, influenza virus is still one of the most important pathogens threatening human and animals’health. Seasonal influenza epidemics brought huge economic burden to the society annually, and if an influenza pandemic broke out there would be an excessive death rate of human all over the world. The 2009 H1N1 influenza pandemic caused over 16,000 deaths worldwide. Development of an effective vaccine and its adjuvants is a critical component in preparation for an influenza pandemic.Ginseng is a valuable traditional Chinese herb with a history of 2000 years. It benefits our health in many ways without any side effects. It showed that ginseng polysaccharide, purified from ginseng roots, stems or leaves, had functions in inducing cytokines, stimulating antibodies and so on. It can improve both specific immune responses and non-specific immune responses.In this study, ginseng polysaccharide, purified from ginseng stems and leaves, were mixed with H1N1 influenza inactivated vaccine and the adjuvant effect were evaluated in mouse model. Female BALB/c mice were randomly divided into eleven groups. Among them, eight groups of mice were co-immunized i.p. with 5ng (HA content) H1N1 influenza inactivated vaccine and ginseng polysaccharide at dosages of 200μg、400μg、600μg、800μg、1200μg、1400μg、1600μg and 2000μg in a total volume of 200μl, respectively. The rest three groups were used as control, in which mice were immunized with inactivated vaccine alone, co-immunized with 100μg Al(OH)3 adjuvant and un-immunized, respectively. After immunization, sera collected at different time points were analyzed to detect IgG, IgG1, IgG2a and IgM antibodies. At the fourth week, mice were challenge with a lethal dose (20×LD50) of the homologous influenza virus. The protective effect conferred by vaccination were evaluated by comparison of body-weight losses and survival rates between different groups.The result showed that ginseng polysaccharide addition could significantly improve vaccine-specific IgG、IgG1 and IgG2a antibody levels in immunized mice when compared with vaccine alone. At the third and forth weeks, vaccine mixed with 800μg of ginseng polysaccharide had an effect equal to vaccine mixed with 100μg Al(OH)3. Besides, ginseng polysaccharide could keep IgG antibody at a high level for a long time (at least three months), but could not improve IgM antibody significantly. We also found that ginseng polysaccharide could enhance the protective ability against a lethal dose challenge of influenza virus. Vaccine mixed with 800μg ginseng polysaccharide provided survival rate of 87.5%, while vaccine alone provided a survival rate of only 25%. Based on these results, we concluded that ginseng polysaccharide enhanced the immune efficacy of inactivated H1N1 influenza vaccine and could be a promising adjuvant.