Biodegradable microspheres: vaccine delivery system for oral immunization

Area of Science:

• Biomaterials Science
• Immunology
• Drug Delivery

Background:

• Controlled release oral vaccine delivery is crucial for improved patient compliance and efficacy.
• Biocompatible and biodegradable microspheres offer a promising platform for oral vaccine administration.
• Understanding microsphere uptake and distribution in the gastrointestinal tract is key to optimizing delivery.

Purpose of the Study:

• To evaluate poly (DL-lactide-co-glycolide) microspheres as a controlled release oral vaccine delivery system.
• To investigate the biodistribution and immune response elicited by orally administered microspheres.
• To compare the immunogenicity of microsphere-encapsulated antigen versus soluble antigen.

Main Methods:

• Orally administered poly (DL-lactide-co-glycolide) microspheres (1-10 micron) were used.
• Microsphere uptake in Peyer's patch lymphoid tissue and dissemination to mesenteric lymph nodes and spleen were analyzed.
• Serum and mucosal (saliva, gut fluid) immune responses were measured after immunization with staphylococcal enterotoxin B toxoid (enterotoxoid) in microspheres.

Main Results:

• Microspheres (≥5 micron) were retained in Peyer's patches for up to 35 days.
• Smaller microspheres (<5 micron) disseminated to mesenteric lymph nodes and spleen via macrophages.
• Oral immunization with enterotoxoid-loaded microspheres induced circulating toxin-specific antibodies and secretory IgA in saliva and gut fluid.

Conclusions:

• Poly (DL-lactide-co-glycolide) microspheres are effective for controlled oral vaccine delivery.
• The microsphere delivery system successfully targets gut-associated lymphoid tissue, promoting both systemic and mucosal immunity.
• This approach offers a viable strategy for developing oral vaccines with enhanced immunogenicity.