ABSTRACT:

Enterotoxigenic E. coli (ETEC) is a major cause of diarrhoea among infants in developing countries and travellers to developing countries. An important protective factor against ETEC infection is the presence of specific antibody in the small intestine. The project objective is to develop a ETEC vaccine for bovine immunisation and production of hyperimmune colostrum, which can be used for passive protection. Vaccine development began in rabbits, assessing the immunogenicity of various ETEC strains. Several inactivated Montanide based vaccines were prepared containing combination of strains at either 2 x 108 or 2 x 109 cells/ml of vaccine as well as a combination of strains suspended in PBS. Sera was analysed using Western blots, heat labile toxin (LT) ELISA and whole cell ELISA. Results indicated that optimal responses to ETEC antigens are obtained when vaccines contained the higher dose of antigen in the oil emulsion. Colonisation factor antigen/I (CFA/I), CFAII and CFAIV strains produced approximately 600, 300 and 190 fold antibody increases respectively. There was also a 55 fold increase in the anti-LT response. The magnitude of the antibody response and the pattern of reactivity is encouraging. Additional CFA strains will be examined to determine the optimal formulation required for broad protection.