Hydroxypropyltrimethyl ammonium chloride chitosan-based hydrogel as the split H5N1 mucosal adjuvant:...

Area of Science:

• Biomaterials Science
• Immunology
• Vaccine Adjuvants

Background:

• Chitosan-based hydrogels are promising mucosal adjuvants.
• Understanding the structure-activity relationship is crucial for optimizing vaccine efficacy.

Purpose of the Study:

• To investigate the structure-activity relationship between 2-hydroxypropyltrimethyl ammonium chloride chitosan (HTCC) hydrogel physicochemical properties and immune responses.
• To evaluate HTCC hydrogels as mucosal adjuvants for an H5N1 vaccine.

Main Methods:

• Prepared a series of HTCC hydrogels with varying quaternization degrees (DQs).
• Characterized hydrogel properties: positive charge, gelation time, and viscosity.
• Assessed immune responses in vivo using an H5N1 vaccine model and an in vivo imaging system.
• Measured systemic (IgG, IgG1, IgG2a, HI) and mucosal (IgA) antibody levels.

Main Results:

• Increasing DQ correlated with higher positive charge and gelation time, but decreased viscosity.
• HTCC hydrogel with moderate DQ (41%) prolonged antigen residence time, enhancing systemic immune responses.
• HTCC hydrogel with the lowest DQ (0%) promoted superior mucosal IgA responses due to closer mucosal contact.
• Animal gender influenced immune responses.

Conclusions:

• Physicochemical properties of HTCC hydrogels, particularly DQ, significantly modulate immune responses.
• HTCC hydrogels demonstrate potential as tunable mucosal adjuvants for vaccines.
• Further research is needed to fully elucidate the mechanisms and optimize adjuvant design.