Polysaccharides belong to a class of natural polymers consisting of glycosidically linked carbohydrate monomers,22 and are believed to have a great potential to be pattern recognition receptor (PRR) agonist adjuvants

Polysaccharides belong to a class of natural polymers consisting of glycosidically linked carbohydrate monomers,22 and are believed to have a great potential to be pattern recognition receptor (PRR) agonist adjuvants. approach to anthrax prevention and control. The currently approved anthrax vaccines are Anthrax Vaccine Adsorbed (AVA, United States) and Anthrax Vaccine Precipitated (AVP, United Kingdom). The major functional immunogen of these vaccines is usually believed to be protective antigen (PA). However, the AVA and AVP still have some drawbacks, such as undefined composition, difficult quality control, and potential reactogenicity, and their efficacy can wane over time due to stability issues in storing alum-based vaccines.12 The recombinant PA (rPA)-based vaccine is regarded as the second-generation anthrax vaccine candidate after AVA and AVP. This kind of vaccine has a clear antigenic component, is easy to prepare, and quality control can be implemented, which effectively reduces the potential safety hazards. In this research, we focused on a natural herb polysaccharide, PCP-I, which is derived from is usually a saprophytic fungus and its sclerotium is called fu-ling in China. The polysaccharides and derivatives of have been reported to exhibit beneficial biological activities, including anticancer, anti-inflammatory, antioxidant, and antiviral properties.13 Here, we investigated the effects of PCP-I used as an adjuvant to enhance the immunogenicity and protection of an anthrax protective antigen-based vaccine. We also examined the synergistic effect of PCP-I combined with CpG as an adjuvant. Our findings indicate that PCP-I may be a promising vaccine adjuvant that warrants further development. Materials and methods Polysaccharide PCP-I preparation PCP-I was prepared from as described previously.14 Briefly, the sclerotium of was extracted with water, precipitated with ethanol, and then dialyzed and lyophilized to produce total polysaccharides (PCP-50). PCP-50 was exceeded through a DEAE-cellulose column to obtain two fractions (PCP-50-A and PCP-50-B). PCP-50-A was further isolated and purified using a Sephadex G-100 column and lyophilized to obtain a homogeneous active polysaccharide (PCP-I). PCP-I appeared as a white powder that dissolved readily in water. No endotoxin was found in PCP-I and its molecular weight was estimated as 30 kDa. Animals and immunization Female BALB/c mice (6C8?weeks old) were purchased from Beijing Vital River Co.Ltd. (Beijing, China). All animals were bred under specific pathogen-free conditions. All animal experiments were approved by the Animal Care and Use Committee of the Beijing Institute of Biotechnology. For immunization experiments using PCP-I alone as adjuvants, groups of mice (BALB/c, n =?6) were immunized three times intramuscularly (i.m.) Eplivanserin mixture at two-week intervals with 0.5?g of PA (PA was expressed and purified as described previously15) unadjuvanted or adjuvanted with PCP-I (200?g); mice from the control group were injected with PBS. For immunization Eplivanserin mixture experiments using PCP-I combined with CpG (ODN 2006, Invivogen, Cat#tlrl-2006-5) as adjuvants, Groups of Eplivanserin mixture mice (BALB/c, n =?8) were immunized three times i.m. at two-week intervals with 0.5?g of PA unadjuvanted or Eplivanserin mixture adjuvanted with PCP-I (200?g) or PCP-I (200?g) + CpG (25?g) or CpG (25?g); mice from the Eplivanserin mixture control group were injected with PBS. Four weeks after the last immunization, the mice were challenged with the anthrax lethal toxin. The anthrax lethal toxin (PA plus Lethal Factor (LF)), was prepared as described previously.15 For the lymphocyte-mediated immunity experiment, groups of mice (BALB/c, n =?6) were immunized three times i.m. at two-week intervals with 5?g of PA unadjuvanted or adjuvanted with PCP-I (200?g). The mice from the control group were injected with PBS. The mice were bled via tail bleeding two weeks after the third immunization, and splenocytes were also isolated from mice two weeks after the third immunization. Serological tests Enzyme-linked immunosorbent assay (ELISA) The levels of PA-specific IgG, IgG1, and IgG2a were determined by ELISA as described previously, with minor modifications.15 Serum samples were twofold serially diluted in 0.1% BSA/PBST (1:100 for total IgG or IgG1 antibodies and 1:50 for IgG2a) and incubated for 1?h Rabbit Polyclonal to CCNB1IP1 at 37C. After washing, horseradish peroxidase (HRP)-conjugated goat anti-mouse IgG (Santa Cruz, Cat#sc-2031), IgG1 (Santa Cruz, Cat#sc-2060), and IgG2a (Santa Cruz, Cat#sc-2061) were added and the samples incubated for 45?min at 37C. The final OD was calculated as.