The stability and immunogenicity of a protein antigen encapsulated in biodegradable microparticles based on blends of lactide polymers and polyethylene glycol

• Published in: Vaccine Vol. 17; no. 6; pp. 512 - 529
• Main Authors: Lavelle, E.C, Yeh, M.-K, Coombes, A.G.A, Davis, S.S
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 12-02-1999; Elsevier
• Subjects: Animals; Antigens - administration & dosage; Antigens - chemistry; Antigens - immunology; Applied microbiology; Biodegradation, Environmental; Biological and medical sciences; Controlled-release; Female; Fundamental and applied biological sciences. Psychology; Hydrogen-Ion Concentration; IgG subtypes; Immune response; Immunization; Immunoglobulin G - classification; Lactic Acid - administration & dosage; Mice; Mice, Inbred BALB C; Microbiology; Microparticles; Microscopy, Electron, Scanning; Ovalbumin - administration & dosage; Ovalbumin - chemistry; Ovalbumin - immunology; Poly( l-lactide); Poly(lactide-co-glycolide); Polyethylene Glycols - administration & dosage; Polyglycolic Acid - administration & dosage; Polylactic Acid-Polyglycolic Acid Copolymer; Polymers - administration & dosage; Protein degradation; Stability; Vaccine; Vaccines, antisera, therapeutical immunoglobulins and monoclonal antibodies (general aspects); Controlled-release; Protein degradation; Stability; Immune response; Poly( l-lactide); Vaccine; Poly(lactide-co-glycolide); Microparticles; IgG subtypes; Encapsulation; Glycolic acid copolymer; Delivery system; Ovalbumin; Controlled release form; Lactic acid copolymer; Rodentia; Property formulation relationship; Antigen; Ethylene oxide polymer; Vertebrata; Mammalia; Immunogenicity; Mouse; Humoral immunity
• ISSN: 0264-410X; 1873-2518
• DOI: 10.1016/S0264-410X(98)00229-1

Protein-loaded microparticles were produced from blends of poly(ethylene glycol) (PEG) with poly(
l-lactide) (PLA) homopolymer or poly(
dl-lactide co-glycolide) copolymers (PLG) using a water-in oil-in oil method. The stability of ovalbumin (OVA) associated with microparticles prepared using PEG and 50:50 PLG, 75:25 PLG and PLA, respectively, was analysed by SDS-PAGE and quantified by scanning densitometry following incubation in PBS at 37°C for up to 1 month. Fragmentation and aggregation of OVA was detected with all 3 formulations. The extent of both processes correlated with the degradation rate of the lactide polymer used and decreased in the order PLA<75:25 PLG<50:50 PLG. Extensive degradation of the PLG/PEG microparticles also occurred over 4 weeks whereas the use of PLA/PEG blends resulted in a stable microparticle morphology and much reduced fragmentation and aggregation of the associated protein. Following a single sub-cutaneous immunisation, high levels of specific serum IgG antibody were elicited by OVA associated with the PLA/PEG particles. Injection of OVA associated with the 75:25 PLG/PEG microparticles resulted in very low levels of specific antibody. A higher response was induced by the 50:50 PLG/PEG formulation but there was very large inter-animal variation in this group. Antibody levels elicited by all 3 formulations were significantly higher than those elicited by a single injection of soluble OVA. Analysis of antigen specific IgG1 and IgG2a antibody subtype levels also revealed the greater efficacy of the PLA/PEG microparticles as an adjuvant system. The use of PLA/PEG microparticles shows improved protein loading and delivery capacity while maintaining a high level of stability of the associated protein. These results indicate a strong correlation between the stability of microencapsulated antigen and the magnitude of the immune response following sub-cutaneous immunisation.