title: Recombinant lipoprotein-based vaccine candidates against C. difficile infections.
abstract: BACKGROUND
  Opportunistically nosocomial infections in hospitalized patients are often related to Clostridium difficile infections (CDI) due to disruption of the intestinal micro-flora by antibiotic therapies during hospitalization. Clostridial exotoxins A and B (TcdA and TcdB) specifically bind to unknown glycoprotein(s) in the host intestine, disrupt the intestinal barrier leading to acute inflammation and diarrhea. The C-terminal receptor binding domain of TcdA (A-rRBD) has been shown to elicit antibody responses that neutralize TcdA toxicity in Vero cell cytotoxicity assays, but not effectively protect hamsters against a lethal dose challenge of C. difficile spores. To develop an effective recombinant subunit vaccine against CDI, A-rRBD was lipidated (rlipoA-RBD) as a rational design to contain an intrinsic adjuvant, a toll-like receptor 2 agonist and expressed in Escherichia coli.
  
  
  RESULTS
  The purified rlipoA-RBD was characterized immunologically and found to have the following properties: (a) mice, hamsters and rabbits vaccinated with 3 μg of rlipoA-RBD produced strong antibody responses that neutralized TcdA toxicity in Vero cell cytotoxicity assays; furthermore, the neutralization titer was comparable to those obtained from antisera immunized either with 10 μg of TcdA toxoid or 30 μg of A-rRBD; (b) rlipoA-RBD elicited immune responses and protected mice from TcdA challenge, but offered insignificant protection (10 to 20 %) against C. difficile spores challenge in hamster models; (c) only rlipoA-RBD formulated with B-rRBD consistently confers protection (90 to 100 %) in the hamster challenge model; and (d) rlipoA-RBD was found to be 10-fold more potent than A-rRBD as an adjuvant to enhancing immune responses against a poor antigen such as ovalbumin.
  
  
  CONCLUSIONS
  These results indicate that rlipoA-RBD formulated with B-rRBD could be an excellent vaccine candidate for preclinical studies and future clinical trials.
authors.affiliation: Vaccine R&D Center, National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan Town, Miaoli County, Taiwan. 981046@nhri.org.tw.|Graduate Institute of Life Science, National Defense Medical Center, Taipei, Taiwan. 981046@nhri.org.tw.
authors.forename: Jui-Hsin
authors.initials: JH
authors.lastname: Huang
authors.affiliation: Vaccine R&D Center, National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan Town, Miaoli County, Taiwan. startup@nhri.org.tw.
authors.forename: Chia-Wei
authors.initials: CW
authors.lastname: Wu
authors.affiliation: Vaccine R&D Center, National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan Town, Miaoli County, Taiwan. lenharry@nhri.org.tw.
authors.forename: Shu-Pei
authors.initials: SP
authors.lastname: Lien
authors.affiliation: Vaccine R&D Center, National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan Town, Miaoli County, Taiwan. leoleng@nhri.org.tw.
authors.forename: Chih-Hsiang
authors.initials: CH
authors.lastname: Leng
authors.affiliation: Vaccine R&D Center, National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan Town, Miaoli County, Taiwan. sunnyboy@nhri.org.tw.
authors.forename: Kuang-Nan
authors.initials: KN
authors.lastname: Hsiao
authors.affiliation: Vaccine R&D Center, National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan Town, Miaoli County, Taiwan. levent@nhri.org.tw.
authors.forename: Shih-Jen
authors.initials: SJ
authors.lastname: Liu
authors.affiliation: Vaccine R&D Center, National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan Town, Miaoli County, Taiwan. chenhw@nhri.org.tw.
authors.forename: Hsin-Wei
authors.initials: HW
authors.lastname: Chen
authors.affiliation: Vaccine R&D Center, National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan Town, Miaoli County, Taiwan. lksiu@nhri.org.tw.
authors.forename: Leung-Kei
authors.initials: LK
authors.lastname: Siu
authors.affiliation: Vaccine R&D Center, National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan Town, Miaoli County, Taiwan. pelechong@nhri.org.tw.|Graduate Institute of Life Science, National Defense Medical Center, Taipei, Taiwan. pelechong@nhri.org.tw.|Graduate Institute of Immunology, China Medical University, Taichung, Taiwan. pelechong@nhri.org.tw.
authors.forename: Pele
authors.initials: P
authors.lastname: Chong
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000235:genetics / Q000276:immunology; D001428:Bacterial Vaccines / Q000235:genetics / Q000276:immunology* / Q000494:pharmacology; D002522:Chlorocebus aethiops; D016360:Clostridioides difficile / Q000235:genetics / Q000276:immunology*; D006224:Cricetinae; D004761:Enterocolitis, Pseudomembranous / Q000235:genetics / Q000276:immunology* / Q000473:pathology / Q000517:prevention & control; D004768:Enterotoxins / Q000235:genetics / Q000276:immunology; D008074:Lipoproteins / Q000235:genetics / Q000276:immunology* / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D011817:Rabbits; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000276:immunology / Q000494:pharmacology; D014709:Vero Cells
chemical_list: D001427:Bacterial Toxins; D001428:Bacterial Vaccines; C488583:Clostridium difficile lethal toxin B; D004768:Enterotoxins; D008074:Lipoproteins; D011993:Recombinant Fusion Proteins; C041348:tcdA protein, Clostridium difficile