Open AccessSerotype conversion of a Shigella flexneri candidate vaccine strain via a novel site‐specific chromosome‐integration system
Author(s) -
Guan Shukui,
Verma Naresh K
Publication year - 1998
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1998.tb13186.x
Subject(s) - shigella flexneri , serotype , virology , biology , microbiology and biotechnology , bacteriophage , gene , escherichia coli , genetics
Shigella flexneri SFL124 (serotype Y) is a promising live oral vaccine candidate, which has been shown to be safe and immunogenic in human volunteers. To change the serotype of this vaccine strain, we inserted a serotype conversion gene cluster into the chromosome of SFL124 by using a bacteriophage‐based site‐specific integration system. By cloning an integrase gene ( int ), an attachment site ( attP ) and a glucosyl transfer gene cluster from bacteriophage SfX into a suicide vector, and subsequently introducing this construct into S. flexneri SFL124, we obtained a S. flexneri strain (designated SFL1213) expressing the serotype X somatic antigen specificity. The strain retained other characteristics of the parent strain, such as colony shape, growth rate, and Congo red binding property. Stability test showed that the serotype X O‐antigen specificity in SFL1213 was 100% stable after being cultured approximately 72 successive hours under non‐selective condition. In a mouse pulmonary model, the recombinant strain elicited a significant level of humoral antibodies which recognized the lipopolysaccharide (LPS) of a wild‐type S. flexneri serotype X strain. The site‐specific insertion system will be useful when stable expression of a cloned single copy gene is desired in the chromosome of S. flexneri vaccine candidate, SFL124.