# Preparation and mechanism study of Alhagi honey polysaccharide-aluminum Pickering emulsion adjuvant for improving intestinal mucosal immune function

## TL;DR

This study develops a new adjuvant using Alhagi honey polysaccharide to boost intestinal and systemic immunity against bovine viral diarrhea in mice.

## Contribution

A novel Pickering emulsion adjuvant combining Alhagi honey polysaccharide and aluminum is shown to enhance mucosal and systemic immune responses.

## Key findings

- AHPPE adjuvant induced IgA production in multiple intestinal segments and elevated serum IgG and cytokine levels.
- The adjuvant recruits antigen-presenting cells and activates immune pathways via CCR9 and T cell-dependent routes.
- AHPPE shows potential as an intestinal-targeted adjuvant for improving BVDV vaccine efficacy.

## Abstract

Bovine viral diarrhea virus (BVDV) can induce diarrhea and mucosal tissue damage, and in severe cases, may result in fatal. Targeted adjuvants capable of enhancing intestinal IgA antibody responses represent an effective strategy for preventing bovine viral diarrhea.

In this study, an Alhagi honey polysaccharide Pickering emulsion (AHPPE) adjuvant was developed by incorporating Alhagi honey polysaccharide (AHP) and retinoic acid (RA) with an aluminium-based adjuvant. Mice were subsequently immunized via intramuscular injection to evaluate the adjuvants' immunostimulatory potential.

The results demonstrate that the particle size of AHPPE is 2133 nm, with excellent dispersion and stability. The encapsulation efficiencies for BVDV and AHP were 66.8% and 73.2%, respectively. AHPPE demonstrated recruitment of antigen-presenting cells at the injection site and activated IgA cells in the duodenum, jejunum, and ileum, inducing to increased IgA expression across multiple intestinal segments. Furthermore, AHPPE significantly induced serum IgG production and elevated levels of cytokines, including IL-4, IL-10, IL-17, IFN-γ, and TNF-α (P<0.05). Through sequencing analysis, it was found that IgA production may be induced via Intestinal immune network for IgA production, thereby mediating intestinal mucosal immune responses.

Collectively, these findings indicate that AHPPE adjuvant administered via injection can simultaneously induce effective systemic immune and intestinal mucosal immunity. Therefore, as a novel intestinal-targeted adjuvant, AHPPE shows potential to enhance the specific intestinal mucosal immunity and systemic immunity of BVDV vaccine.

After mixing the Alhagi honey polysaccharide Pickering emulsion with the antigen BVDV, and immunising mice through intramuscular injection into the skin, the antigen-presenting cells undergo uptake phagocytosis, recruiting dendritic cells and macrophages, and then homing to the intestine through the action of the intestinal homing receptor CCR9, and then B cell activation in the intestinal lymph nodes via a T cell-dependent route to produce IgA antibodies, and immune cell activation via a non-translocated T cell-dependent route, leading to IgA antibody production; thus inducing systemic and mucosal immunity. Activation of immune cells through a T-cell-dependent route, resulting in the production of IgA antibodies; this in turn induces systemic immunity and intestinal mucosal immunity.Scientific illustration depicts a mouse receiving an AHPP/BVDV injection, showing antigen movement through tissues to immune cells. Pathways detail antigen presenting cells, dendritic cells, T and B cell activation, cytokine release, and IgA and IgG antibody production via lymph node trafficking.

After mixing the Alhagi honey polysaccharide Pickering emulsion with the antigen BVDV, and immunising mice through intramuscular injection into the skin, the antigen-presenting cells undergo uptake phagocytosis, recruiting dendritic cells and macrophages, and then homing to the intestine through the action of the intestinal homing receptor CCR9, and then B cell activation in the intestinal lymph nodes via a T cell-dependent route to produce IgA antibodies, and immune cell activation via a non-translocated T cell-dependent route, leading to IgA antibody production; thus inducing systemic and mucosal immunity. Activation of immune cells through a T-cell-dependent route, resulting in the production of IgA antibodies; this in turn induces systemic immunity and intestinal mucosal immunity.