• Vaccine Name: inactivated ETEC expressing expressing CFA/I and CFA/II
• Target Pathogen: Escherichia coli
• Target Disease: Hemorrhagic colitis
• Vaccine Ontology ID: VO_0000502
• Type: Inactivated or "killed" vaccine
• Antigen: The antigen used in this vaccine was ETEC bacteria expressing fimbrial colonization factor antigens I and II (CFA/I and CFA/II) (Wennerås et al., 1992).
• Adjuvant:
  • Adjuvant name:
  • VO adjuvant ID: VO_0001242
  • Description: cholera toxin B subunit (CTB). However, it was found that CTB did not function as a mucosal adjuvant, since CFA-specific ASC responses were not enhanced by the simultaneous administration of CTB (Wennerås et al., 1992).
• Preparation: Each vaccine consisted of 10^11 formalin-killed ETEC bacteria expressing CFA/I and CFA/II (CS1, CS2, and CS3). The following strains were used: an ST-positive 078:H12 strain expressing CFA/I, a toxin-negative 0139:H28 strain expressing CS1, and an ST-positive 06:H16 strain expressing CS2 and CS3 The strains were grown under conditions leading to a high level of expression of the different CFAs, and thereafter the organisms were killed by mild formalin treatment, preserving 50 to 100% of the CFA activity. The inactivated bacteria were mixed to give a total of 10^11 formalin-killed E. coli bacteria in 4 ml of phosphate-buffered saline, corresponding to one vaccine dose. The CFA/I proteins used in the vaccine were purified from a flagellum-deficient mutant of strain H10407 by homogenization with a blender followed by ammonium sulfate fractionation and negative diethylaminoethyl-Sephadex column chromatography. Purified CFA/II (CS1 plus CS3) protein was prepared from strain E1392-75 by homogenization followed by salt precipitation and column chromatography (Wennerås et al., 1992).

Human Response

• Vaccination Protocol: Thirty-seven healthy adult individuals participated in this study. Thirty-one volunteers received three oral doses of a prototype ETEC vaccine, with a 2-week interval between doses; six volunteers were studied for control purposes only. To provide the CTB component, 21 of the vaccinees also received a dose of oral cholera vaccine, consisting of 1 mg of purified CTB and 10^11 killed Vibrio cholerae O1 organisms together with the ETEC expressing the various CFAs (CFA+ ETEC) (Wennerås et al., 1992).
• Immune Response: ASC responses to both CFAs were comparable in magnitude and isotype distribution, with IgA-ASCs dominating the response. After three oral immunizations, the vaccinees had, respectively, 14- and 11-times-higher geometric mean levels of IgA-ASCs directed against CFA/I and CFA/II than did nonimmunized controls. The geometric means of specific IgA-ASCs postvaccination were 31 per 10^7 MNC for CFA/I and 23 per 10^7 MNC for CFA/II. Although less pronounced, IgM-ASC responses to the CFAs were also detected in most vaccinees. After three immunizations, the geometric means of IgM-ASCs were 11 and 6 times higher for CFA/I and CFA/II, respectively, than in nonimmunized controls. CFA-specific IgG-ASCs were rarely detected. Specific ASC responses to the CTB component of the vaccine were detected in all volunteers but differed from CFA-specific responses with respect to isotype distribution. The results of this study suggest that two oral immunizations are efficient at inducing optimal CFA-specific responses, since the numbers of CFA-ASCs were not increased but rather were decreased upon administration of a third dose of vaccine. (Wennerås et al., 1992).
• Side Effects: A few of the vaccinees experienced slight abdominal discomfort for a couple of hours on the day of either the first or second immunization (Wennerås et al., 1992).
• Efficacy: Almost 90% of the volunteers developed CFA-specific ASC responses after vaccination (Wennerås et al., 1992).