Coated Bacterial Vaccine: A New Approach for Antigen Display on Bacterial Surface

Area of Science:

• Vaccinology
• Microbiology
• Immunology

Background:

• Bacterial vaccines with surface-displayed recombinant antigens offer advantages but face challenges.
• Existing platforms like live, inactivated, or bacterial-like particle vaccines have limitations such as genetic instability and antigen degradation.

Purpose of the Study:

• To introduce and validate a novel coated bacterial vaccine (CBV) system.
• To assess the efficacy of CBVs in inducing protective immunity against tetanus toxin.

Main Methods:

• A CBV system was developed by anchoring a recombinant tetanus toxin fragment (TTFC) fused to a cell wall-binding domain (dSLPA) onto chemically inactivated *Bacillus subtilis*.
• CBVs were used to immunize BALB/c mice, followed by challenge with tetanus toxin.
• Immune responses, including anti-TTFC IgG antibody levels and cytokine production (IL-1β, IL-6, IL-10), were analyzed.

Main Results:

• Vaccination with CBVs resulted in a 100% survival rate in mice challenged with tetanus toxin.
• A strong anti-TTFC IgG antibody response, with elevated IgG1 levels, was observed.
• Macrophage assays indicated increased mRNA levels for IL-1β, IL-6, and IL-10, and significant IL-6 secretion.

Conclusions:

• The developed *B. subtilis*-based CBV system effectively induces active immune protection against tetanus toxin challenge.
• The immune response appears to be Th2-polarized, suggesting CBVs are a promising platform for next-generation vaccines.