Immunostimulatory lipid implants containing Quil-A and DC-cholesterol

Area of Science:

• Biomaterials Science
• Vaccinology
• Immunology

Background:

• Biocompatible lipid implants offer sustained antigen release for subunit vaccines, potentially reducing the need for multiple doses.
• Previous research showed lipid implants with phosphatidylcholine, cholesterol, Quil-A, and ovalbumin stimulated immune responses comparable to injectable vaccines, but with low antigen entrapment.
• Low antigen entrapment in released particles from lipid implants limits their effectiveness as vaccine delivery systems.

Purpose of the Study:

• To evaluate if incorporating cationic DC-cholesterol into lipid implants enhances antigen entrapment and immunogenicity.
• To determine if cationic lipid implants can elicit an immune response comparable to a prime-boost injectable vaccine.
• To compare the immunogenicity of modified and unmodified lipid implants against injectable vaccines and other formulations.

Main Methods:

• Formulation of biocompatible lipid implants containing phosphatidylcholine, cholesterol, ovalbumin (antigen), and Quil-A (adjuvant).
• Inclusion of cationic DC-cholesterol in modified lipid implants to assess its impact on antigen entrapment.
• Evaluation of immune responses, including cellular responses, induced by the implants compared to injectable vaccines and controls.

Main Results:

• The inclusion of DC-cholesterol had a minimal effect on antigen entrapment into particles released from the implants.
• The cationic implants did not stimulate cellular responses as effectively as the comparable injectable vaccine or the unmodified implant containing Quil-A and cholesterol.
• Despite limitations, the lipid implants induced stronger immune responses than soluble protein alone or protein co-delivered in alum.

Conclusions:

• Cationic modification of lipid implants with DC-cholesterol did not significantly improve antigen entrapment or immunogenicity for subunit vaccine delivery.
• Unmodified lipid implants containing Quil-A and cholesterol demonstrated potential for vaccine delivery, though less effective than injectable vaccines in stimulating cellular responses.
• Further research is needed to optimize lipid implant formulations for enhanced antigen entrapment and robust immunogenicity in vaccine applications.