Polysaccharide PCP-I isolated from Poria cocos enhances the immunogenicity and protection of an anthrax protective antigen-based vaccine

Hum Vaccin Immunother. 2020 Jul 2;16(7):1699-1707. doi: 10.1080/21645515.2019.1675457. Epub 2019 Dec 6.

Abstract

Polysaccharides isolated from natural plants may represent a novel source of vaccine adjuvants. In this research, we focused on a natural plant polysaccharide, PCP-I, which is derived from Poria cocos, a Chinese traditional herbal medicine. We chose the anthrax protective antigen (PA) as a model to evaluate the adjuvant ability of PCP-I in enhancing the immunogenicity and protection of a PA-based anthrax vaccine. According to our results, PCP-I could significantly enhance anthrax specific anti-PA antibodies, toxin-neutralizing antibodies, anti-PA antibody affinity, as well as IgG1 and IgG2a levels. Besides, PCP-I increased the frequency of PA-specific memory B cells, increased the proliferation of PA-specific splenocytes, significantly stimulated the secretion of IL-4, and enhanced the activation of Dendritic cells (DCs) in vitro. The combination of PCP-I and CpG significantly enhanced the level of anti-PA antibodies and neutralizing antibodies, particularly PA-specific IgG2a, and shifted the Th2-bias to a Th1/Th2 balanced response. In addition, PCP-I with or without CpG could significantly improve the survival rate of immunized mice following challenge with the anthrax lethal toxin. These findings suggest that PCP-I may be a promising vaccine adjuvant that warrants further study.

Keywords: Poria cocos; Polysaccharide; anthrax; protective antigen; vaccine adjuvant.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Anthrax Vaccines*
  • Anthrax* / prevention & control
  • Antibodies, Bacterial
  • Antigens, Bacterial
  • Bacillus anthracis*
  • Bacterial Toxins
  • Mice
  • Mice, Inbred BALB C
  • Polysaccharides
  • Wolfiporia*

Substances

  • Anthrax Vaccines
  • Antibodies, Bacterial
  • Antigens, Bacterial
  • Bacterial Toxins
  • Polysaccharides
  • anthrax toxin

Grants and funding

This work was supported by the [National Science and Technology Major Project of China] under Grant [number 2016ZX10004001]; [National Natural Science Foundation of China] under Grant [number 31300760].