Abstract
We describe here the development of stable classical and El Tor V. cholerae O1 strains of the Hikojima serotype that co–express the Inaba and Ogawa antigens of O1 lipopolysaccharide (LPS). Mutation of the wbeT gene reduced LPS perosamine methylation and thereby gave only partial transformation into Ogawa LPS on the cell surface. The strains express approximately equal amounts of Inaba– and Ogawa–LPS antigens which are preserved after formalin–inactivation of the bacteria. Oral immunizations of both inbred and outbred mice with formalin–inactivated whole–cell vaccine preparations of these strains elicited strong intestinal IgA anti–LPS as well as serum vibriocidal antibody responses against both Inaba and Ogawa that were fully comparable to the responses induced by the licensed Dukoral vaccine. Passive protection studies in infant mice showed that immune sera raised against either of the novel Hikojima vaccine strains protected baby mice against infection with virulent strains of both serotypes. This study illustrates the power of using genetic manipulation to improve the properties of bacteria strains for use in killed whole–cell vaccines.
Highlights
IntroductionOften severe diarrheal disease which can be fatal to both children and adults [1]
Cholera is an acute, often severe diarrheal disease which can be fatal to both children and adults [1]
Mutagenesis of the wbeT gene and serotype switching We determined that a point mutation in wbeT creating the mutation S158P in the gene product completely destroyed its LPS methylation activity resulting in the Inaba serotype
Summary
Often severe diarrheal disease which can be fatal to both children and adults [1]. It is caused in most cases by Vibrio cholerae bacteria of a single serogroup, O1. In many cholera–endemic countries and in cholera outbreaks following natural or political disasters clean water and basic sanitation measures are lacking and vaccines are increasingly recognized as an important preventive intervention [3,4,5,6]. Two licensed OCVs are available both of which are killed V. cholerae O1 whole cell vaccines comprising a mixture of strains of Inaba and Ogawa serotypes and El Tor and classical biotypes: one (Dukoral) contains cholera toxin B–subunit (CTB) and one (Shanchol) lacks CTB but contains a V. cholerae strain of the O139 serogroup
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