ABSTRACT
Lessons Learned from Studies with a Prototype Attenuated Escherichia coli Live Oral ETEC Vaccine E. coli E1392-75-2A is a CFA/II-positive mutant strain derived in the Central Public Health Laboratory, Colindale, U.K. wherein the genes encoding LT and ST spontaneously deleted from the CFA/II plasmid. Consequently, E1392-75-2A, which expresses CS1 and CS3 fimbrial antigens, is negative when tested with toxin assays and gene probes for LT and ST. Levine et al. (7,19,20) utilized strain E1392-75-2A to explore fundamental questions of anticolonization immunity in the absence of antitoxic immunity. All volunteers who were fed 1010 CFU of strain E1392-75-2A developed significant rises in intestinal fluid SIgA antibody to CS1 and CS3 fimbriae. The geometric mean titer (GMT) of anti-fimbrial CS1 and CS3 SIgA antibody in these volunteers was 10-fold higher than the peak postvaccination GMT of volunteers who received enteral immunization with multiple doses of purified CS1 and CS3 fimbriae.
