title: Safety and immunogenicity of an improved oral inactivated multivalent enterotoxigenic Escherichia coli (ETEC) vaccine administered alone and together with dmLT adjuvant in a double-blind, randomized, placebo-controlled Phase I study.
abstract: BACKGROUND
  We have developed a new oral vaccine against enterotoxigenic Escherichia coli (ETEC), which is the most common cause of bacterial diarrhea in children in developing countries and in travelers.
  
  
  METHODS
  The vaccine was tested for safety and immunogenicity alone and together with double-mutant heat-labile toxin (dmLT) adjuvant in a double-blind, placebo-controlled Phase I study in 129 Swedish adults. The vaccine consists of four inactivated recombinant E. coli strains overexpressing the major ETEC colonization factors (CFs) CFA/I, CS3, CS5, and CS6 mixed with an LT B-subunit related toxoid, LCTBA. Volunteers received two oral doses of vaccine alone, vaccine plus 10 μg or 25 μg dmLT or placebo. Secretory IgA antibody responses in fecal samples and IgA responses in secretions from circulating intestine-derived antibody secreting cells were assessed as primary measures of vaccine immunogenicity.
  
  
  RESULTS
  The vaccine was safe and well tolerated; adverse events were few and generally mild with no significant differences between subjects receiving placebo or vaccine with or without adjuvant. As many as 74% of subjects receiving vaccine alone and 83% receiving vaccine plus 10 μg dmLT showed significant mucosal IgA responses to all five primary vaccine antigens and about 90% of all vaccinees responded to at least four of the antigens. Subjects receiving vaccine plus 10 μg dmLT responded with significantly increased intestine-derived anti-CS6 responses compared to subjects receiving vaccine alone.
  
  
  CONCLUSIONS
  The vaccine was safe and broadly immunogenic. dmLT further enhanced mucosal immune responses to CF antigens present in low amounts in the vaccine. Based on these encouraging results, the vaccine will be tested for safety and immunogenicity in different age groups including infants in Bangladesh and for protective efficacy in travelers.
authors.affiliation: University of Gothenburg Vaccine Research Institute (GUVAX), Dept. of Microbiology and Immunology, University of Gothenburg, Box 435, 405 30 Gothenburg, Sweden. Electronic address: anna.lundgren@microbio.gu.se.
authors.forename: Anna
authors.initials: A
authors.lastname: Lundgren
authors.affiliation: PATH, 455 Massachusetts Ave, NW, WA, DC 20001, USA. Electronic address: lbourgeois@path.org.
authors.forename: Louis
authors.initials: L
authors.lastname: Bourgeois
authors.affiliation: Scandinavian Biopharma, Gunnar Asplunds allé 16, 171 63 Solna, Sweden. Electronic address: nils.carlin@etvax.se.
authors.forename: Nils
authors.initials: N
authors.lastname: Carlin
authors.affiliation: Department of Microbiology and Immunology, Tulane University School of Medicine, New Orleans, LA 70112, USA. Electronic address: jclemen@tulane.edu.
authors.forename: John
authors.initials: J
authors.lastname: Clements
authors.affiliation: Scandinavian Biopharma, Gunnar Asplunds allé 16, 171 63 Solna, Sweden. Electronic address: bjorn.gustafsson@etvax.se.
authors.forename: Björn
authors.initials: B
authors.lastname: Gustafsson
authors.affiliation: Clinical Trial Center, Sahlgrenska University Hospital, Gröna stråket 12, 413 45 Gothenburg, Sweden. Electronic address: amhgbg@gmail.com.
authors.forename: Marianne
authors.initials: M
authors.lastname: Hartford
authors.affiliation: University of Gothenburg Vaccine Research Institute (GUVAX), Dept. of Microbiology and Immunology, University of Gothenburg, Box 435, 405 30 Gothenburg, Sweden. Electronic address: jan.holmgren@microbio.gu.se.
authors.forename: Jan
authors.initials: J
authors.lastname: Holmgren
authors.affiliation: Centre for Applied Biostatistics, Sahlgrenska Academy, University of Gothenburg, Box 414, 405 30 Gothenburg, Sweden. Electronic address: max.petzold@gu.se.
authors.forename: Max
authors.initials: M
authors.lastname: Petzold
authors.affiliation: PATH, 455 Massachusetts Ave, NW, WA, DC 20001, USA. Electronic address: rwalker@path.org.
authors.forename: Richard
authors.initials: R
authors.lastname: Walker
authors.affiliation: University of Gothenburg Vaccine Research Institute (GUVAX), Dept. of Microbiology and Immunology, University of Gothenburg, Box 435, 405 30 Gothenburg, Sweden. Electronic address: ann-mari.svennerholm@microbio.gu.se.
authors.forename: Ann-Mari
authors.initials: AM
authors.lastname: Svennerholm
mesh_terms: D000276:Adjuvants, Immunologic / Q000008:administration & dosage* / Q000235:genetics; D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D000907:Antibodies, Bacterial / Q000032:analysis; D000921:Antibody-Producing Cells / Q000276:immunology; D001427:Bacterial Toxins / Q000008:administration & dosage / Q000235:genetics; D004311:Double-Blind Method; D054307:Enterotoxigenic Escherichia coli / Q000276:immunology*; D004768:Enterotoxins / Q000008:administration & dosage / Q000235:genetics; D004927:Escherichia coli Infections / Q000517:prevention & control*; D029968:Escherichia coli Proteins / Q000008:administration & dosage / Q000235:genetics; D022361:Escherichia coli Vaccines / Q000008:administration & dosage / Q000009:adverse effects* / Q000276:immunology*; D005243:Feces / Q000737:chemistry; D005260:Female; D006801:Humans; D018928:Immunity, Mucosal; D007070:Immunoglobulin A / Q000032:analysis; D008297:Male; D050505:Mutant Proteins / Q000008:administration & dosage / Q000235:genetics; D010919:Placebos / Q000008:administration & dosage; D013548:Sweden; D055815:Young Adult
chemical_list: D000276:Adjuvants, Immunologic; D000907:Antibodies, Bacterial; D001427:Bacterial Toxins; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D022361:Escherichia coli Vaccines; D007070:Immunoglobulin A; D050505:Mutant Proteins; D010919:Placebos; C027538:heat-labile enterotoxin, E coli
keywords: ETEC; Human; IgA; Intestinal immunity; Vaccine; dmLT