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1.
Int J Med Microbiol ; 299(4): 233-46, 2009 Apr.
Article in English | MEDLINE | ID: mdl-19121604

ABSTRACT

The attenuated live bacterial vaccine strain Salmonella enterica Serovar Typhi Ty21a is the main constituent of Vivotif, the only licensed oral vaccine against typhoid fever. The strain was developed in the 1970s by chemical mutagenesis. In the course of this mutagenesis, a number of mutations were introduced into the vaccine strain. Characterisation of the vaccine strain during development as well as release of master- and working seed lots (MSL and WSL) and commercial batches is based on phenotypic assays assessing microbiological and biochemical characteristics of Ty21a. In the current study, we have analysed by DNA sequencing the specific mutations originally correlated with the attenuation of strain Ty21a. These data demonstrate the stability of these mutations for MSLs and WSLs of Ty21a produced between 1980 and 2005. Finally, we have confirmed the correlation of these genetic mutations with the expected phenotypic attenuations for the seed lots used in vaccine manufacture over 25 years.


Subject(s)
Genomic Instability , Salmonella Vaccines/genetics , Salmonella typhi/genetics , DNA, Bacterial/genetics , Humans , Mutation, Missense , Point Mutation , Sequence Analysis, DNA , Vaccines, Attenuated/genetics , Virulence Factors/genetics
2.
Int J Med Microbiol ; 299(2): 109-19, 2009 Feb.
Article in English | MEDLINE | ID: mdl-18706861

ABSTRACT

The attenuated Salmonella enterica serovar Typhi strain Ty21a (Ty21a) is the only attenuated live oral vaccine against typhoid fever. Ty21a is also an attractive carrier for the delivery of heterologous antigens. We have used Ty21a for antigen delivery via the hemolysin (HlyA) secretion system of Escherichia coli, the prototype of the type I secretion system (T1SS). In this study, we identified by genetic complementation that the specific mutation of rpoS correlated with the hemolysin production of strain Ty21a. We furthermore showed that complementation with a plasmid encoding rfaH, which is described to be a downstream target of rpoS, led to increased expression and secretion of hemolysin. Finally, we demonstrated a significant enhancement of antibody responses against the heterologous HlyA antigen of Ty21a after immunization of mice with rfaH complemented S. typhi strain secreting HlyA compared with the same strain without rfaH plasmid.


Subject(s)
Bacterial Vaccines/genetics , Bacterial Vaccines/immunology , Escherichia coli Proteins/genetics , Escherichia coli Proteins/metabolism , Hemolysin Proteins/genetics , Hemolysin Proteins/metabolism , Salmonella typhi/genetics , Salmonella typhi/immunology , Animals , Antibodies, Bacterial/blood , Antigens, Bacterial/genetics , Antigens, Bacterial/immunology , Bacterial Proteins/genetics , Bacterial Proteins/physiology , Genetic Complementation Test , Hemolysin Proteins/biosynthesis , Mice , Peptide Elongation Factors/genetics , Peptide Elongation Factors/metabolism , Plasmids , Sigma Factor/genetics , Sigma Factor/physiology , Trans-Activators/genetics , Trans-Activators/metabolism , Vaccines, Attenuated/genetics , Vaccines, Attenuated/immunology
3.
Chem Rev ; 97(5): 1567-1608, 1997 Aug 05.
Article in English | MEDLINE | ID: mdl-11851459
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