"April 2002"Bibliography: leaves 143-173.[12], 173 leaves : ill. ; 30 cm.Research into methods of vaccination against enteric diseases has demonstrated the advantages of using live attenuated Salmonella as carriers of foreign antigen. However, recent data have shown that prior exposure of mice to Salmonella can dramatically reduce serum antibody responses to foreign antigen subsequently delivered by the same strain. Since these findings contradict earlier reports, the aim of this thesis was to further assess the significance of pre-existing anti-vector immunity as an impediment to the Salmonella-based vaccine strategy. The results of experiments conducted strengthen concerns that pre-existing anti-vector immunity represents a serious threat to the Salmonella-based vaccine strategy.Thesis (Ph.D.)--University of Adelaide, Dept. of Molecular Biosciences, 200