title: Immunogenicity of a cholera toxin B subunit Porphyromonas gingivalis fimbrial antigen fusion protein expressed in E. coli.
abstract: The gram-negative anaerobic oral bacterium Porphyromonas gingivalis initiates periodontal disease through fimbrial attachment to saliva-coated oral surfaces. To study the effects of immunomodulation on enhancement of subunit vaccination, the expression in E. coli and immunogenicity of P. gingivalis fimbrial protein (FimA) linked to the C-terminus of the cholera toxin B subunit (CTB) were investigated. Complementary DNAs encoding the P. gingivalis 381 fimbrillin protein sequence FimA1 (amino acid residues 1-200) and FimA2 (amino acid residues 201-337) were cloned into an E. coli expression vector downstream of a cDNA fragment encoding the immunostimulatory CTB. CTB-FimA1 and CTB-FimA2 fusion proteins synthesized in E. coli BL21 (DE3) cells were purified under denaturing conditions by Ni2+-NTA affinity column chromatography. Renaturation of the CTB-FimA1 and CTB-FimA2 fusion proteins, permitted identification of CTB-FimA pentamers and restored CTB binding activity to GM1-ganglioside to provide a biologically active CTB-FimA fusion protein. Mice orally inoculated with purified CTB-FimA1 or CTB-FimA2 fusion proteins generated measurable FimA1 and FimA2 IgG antibody titers, while no serum fimbrial IgG antibodies were detected when mice were inoculated with FimA1 or FimA2 proteins alone. Immunoblot analysis confirmed that sera from mice immunized with CTB linked to FimA1 or FimA2 contained antibodies specific for P. gingivalis fimbrial proteins. In addition, mice immunized with FimA2 or CTB-FimA2 generated measurable intestinal IgA titers indicating the presence of fimbrial antibody class switching. Further, mice orally immunized with CTB-FimA1 generated higher IgA antibody titers than mice inoculated with FimA1 alone. The experimental data show that the immunostimulatory molecule CTB enhances B cell-mediated immunity against linked P. gingivalis FimA fusion proteins, in comparison to immunization with FimA protein alone. Thus, linkage of CTB to P. gingivalis fimbrial antigens can increase subunit vaccine immunogenicity to provide enhanced protection against periodontal disease.
authors.affiliation: Division of Biological Sciences, Research Center for Bioactive Materials, Department of Periodontology, School of Dentistry, Chonbuk National University, Jeonju, 561-756, Republic of Korea.
authors.forename: Tae-Geum
authors.initials: TG
authors.lastname: Kim
authors.forename: Nguyen-Xuan
authors.initials: NX
authors.lastname: Huy
authors.forename: Mi-Young
authors.initials: MY
authors.lastname: Kim
authors.forename: Dong-Keun
authors.initials: DK
authors.lastname: Jeong
authors.forename: Yong-Suk
authors.initials: YS
authors.lastname: Jang
authors.forename: Moon-Sik
authors.initials: MS
authors.lastname: Yang
authors.forename: William H R
authors.initials: WH
authors.lastname: Langridge
authors.forename: Jin-Yong
authors.initials: JY
authors.lastname: Lee
mesh_terms: D000284:Administration, Oral; D000907:Antibodies, Bacterial / Q000032:analysis / Q000097:blood; D001428:Bacterial Vaccines / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D016866:Bacteroidaceae Infections / Q000276:immunology / Q000382:microbiology; D002772:Cholera Toxin / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005243:Feces / Q000737:chemistry; D036781:Fimbriae Proteins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D007114:Immunization; D007070:Immunoglobulin A / Q000032:analysis; D007074:Immunoglobulin G / Q000097:blood; D016966:Porphyromonas gingivalis / Q000235:genetics* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism
chemical_list: D000907:Antibodies, Bacterial; D001428:Bacterial Vaccines; D007070:Immunoglobulin A; D007074:Immunoglobulin G; D011993:Recombinant Fusion Proteins; C063055:fimbrillin; D036781:Fimbriae Proteins; D002772:Cholera Toxin