ABSTRACT
Although a variety of vaccines to prevent typhoid fever and cholera (caused by Vibrio cholerae O1) are licensed in many countries, there are no licensed vaccines against nontyphoidal Salmonella, Shigella, V. cholerae O139, and Escherichia coli O157. We investigated the protective antigens and the host components that confer immunity against this latter important group of diseases to devise safe and effective vaccines [1]. The long experience with vaccines composed of either inactivated or attenuated strains of bacterial pathogens was based largely upon Pasteur’s idea for vaccine development: that convalescence from disease induces immunity. But inactivated or attenuated strains of bacteria are not good immunogens when administered in a clinically acceptable form, and convalescence from many enteric infections, such as shigellosis, does not reliably confer a high degree of immunity of long duration [2].
