Enterotoxigenic @entity526 (ETEC) is a leading cause of @entity294 in travelers to countries where the disease is endemic and causes a major disease burden in the indigenous population, particularly @entity1 . We describe here the generation and preclinical characterization of candidate strains of ETEC which are intended to provide the basis of a live attenuated oral vaccine to prevent this disease. It has been shown previously that a spontaneously arising toxin-negative variant ETEC strain, E1392/75-2A, could confer 75% protection against challenge when administered to volunteers. Unfortunately this strain induced mild @entity294 in 15% of recipients. To eliminate the unacceptable reactogenicity of strain E1392/75-2A, it was further attenuated by introducing three different combinations of defined deletion mutations into the chromosome. A @entity19 intranasal model of immunization was developed and used to show that all of the strains were immunogenic. Immune responses against colonization factor antigens (CFAs) were particularly strong when the bacterial inocula were grown on " @entity3795 agar," which induces strong expression of these antigens. Two of the strains were selected for a phase I dose escalation safety study with healthy adult volunteers. Freshly grown organisms were harvested from @entity3795 agar plates and administered to volunteers as a suspension containing from 5 x 10(7) to 5 x 10(9) CFU. The vaccine was well tolerated at all doses and induced significant immune responses in all recipients at the highest dose of either strain. The results provide the basis for further clinical evaluation of these vaccine candidates.

Construction and characterization of genetically defined aro omp mutants of enterotoxigenic XXXX and preliminary studies of safety and immunogenicity in @entity1 .

@entity1 :: ('9606', 'Species') :: ['children'] @entity19 :: ('10090', 'Species') :: ['mouse'] @entity294 :: ('MESH:D003967', 'Disease') :: ['diarrhea'] @entity3795 :: ('31658', 'Species') :: ['CFA'] @entity526 :: ('562', 'Species') :: ['Escherichia coli']
@entity526 :: (562,Species) :: ['Escherichia coli']
