Oral Vaccines for Enterotoxigenic Escherichia coli

Abstract Although enterotoxigenic Escherichia coli (ETEC) is the most common causes of bacterial diarrhea in children in developing countries and in travelers to these areas, no licensed vaccine against ETEC disease is yet available. In this chapter, we identify the most promising vaccine antigens and immunization routes as a basis for development of an effective ETEC vaccine. A number of different candidate vaccines, both purified antigens and whole cells, have been tested for safety and immunogenicity in preclinical trials, several with promising results. A few candidate vaccines have also reached testing in clinical trials, the most advanced being an oral inactivated whole cell vaccine, ETVAX, consisting of recombinant E. coli bacteria overexpressing the most prevalent colonization factors (CFs; fimbrial and nonfimbrial antigens) in combination with a heat-labile enterotoxoid (LCTBA) and dmLT double mutant heat-labile enterotoxin serving as an adjuvant. This vaccine has been tested successfully in different phase1 and 2 trials both in Swedish adults and in descending age groups in Bangladesh, and it is currently being evaluated for protective efficacy in a large phase 2b trial in European travelers to Africa.