title: Potent antigen-specific immune responses stimulated by codelivery of CpG ODN and antigens in degradable microparticles.
abstract: CpG ODN stimulates a TH1 response through its receptor Toll-like receptor 9 (TLR9). TLR9 is a receptor that is found intracellularly. Microparticles are efficiently internalized by dendritic cells (DCs) and macrophages and would thus be an ideal delivery vehicle for CpG ODN to reach its target site thereby enhancing the TH1 response to an antigen also encapsulated in the microparticle. Here, we show that careful control over fabrication parameters can produce biodegradable microparticles with predictable size distributions, surface morphology, and shape. Entrapment efficiencies of the model antigen OVA ranged from 19% to 23% with an average loading of 10 microg/mg of microparticles. For CpG ODN, these values were 33% to 35%, which corresponded to an average loading of 8.5 microg/mg of microparticles. The microparticles release CpG ODN and OVA in a burst followed by sustained release profile. At the highest concentration of microparticles incubated with a pure DC cell line, 92% of DCs had internalized microparticles by 16 hours, confirming that DCs efficiently take up the microparticles. Microparticles are capable of inducing DC maturation as determined by up-regulation of CD80 and CD86 markers. Although the presence of CpG ODN in the microparticles did not impact on the phenotype of the DCs, it was necessary for DCs to induce activation of antigen-specific T cells as indicated by interferon-gamma production. Microparticles entrapping both antigen and CpG ODN induced significantly higher amounts of anti-OVA antibody production than other preparations such as the soluble OVA and CpG ODN (P<0.01) and stimulated stronger IgG2a production than delivery of microparticles entrapping antigen alone. We conclude that co-encapsulating immunostimulatory CpG ODN and antigen in degradable microparticles is an effective approach to enhancing development of a TH1 immune response.
authors.affiliation: Division of Pharmaceutics, College of Pharmacy, University of Iowa, 115 S. Grand Avenue, Iowa City, IA, USA.
authors.forename: Xue-Qing
authors.initials: XQ
authors.lastname: Zhang
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Dahle
authors.forename: Nicki K
authors.initials: NK
authors.lastname: Baman
authors.forename: Nathan
authors.initials: N
authors.lastname: Rich
authors.forename: George J
authors.initials: GJ
authors.lastname: Weiner
authors.forename: Aliasger K
authors.initials: AK
authors.lastname: Salem
mesh_terms: D000818:Animals; D018122:B7-1 Antigen / Q000276:immunology; D051940:B7-2 Antigen / Q000276:immunology; D002454:Cell Differentiation; D002460:Cell Line; D004247:DNA / Q000008:administration & dosage* / Q000276:immunology / Q000493:pharmacokinetics; D003713:Dendritic Cells / Q000166:cytology / Q000276:immunology; D004337:Drug Carriers; D016503:Drug Delivery Systems; D005260:Female; D000949:Histocompatibility Antigens Class II / Q000276:immunology; D007074:Immunoglobulin G / Q000276:immunology; D019344:Lactic Acid; D051379:Mice; D008810:Mice, Inbred C57BL; D008863:Microspheres; D009838:Oligodeoxyribonucleotides; D010047:Ovalbumin / Q000008:administration & dosage* / Q000276:immunology; D010316:Particle Size; D011100:Polyglycolic Acid; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers; D014611:Vaccination
chemical_list: D018122:B7-1 Antigen; D051940:B7-2 Antigen; C423449:CpG ODN 1826; D004337:Drug Carriers; D000949:Histocompatibility Antigens Class II; D007074:Immunoglobulin G; D009838:Oligodeoxyribonucleotides; D011108:Polymers; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; D010047:Ovalbumin; D004247:DNA