Yi, Chang Yang
(2008)
Mutation of hemA gene of shigella flexneri:
towards development of an oral live attenuated
shigella vaccine.
Other.
Universiti Sains Malaysia.
(Submitted)
Abstract
Shigella is one of the most important causes of gastroenteritis and death of 3-5
millions of children under the age of 5 years in developing countries (Ashkenazi, 2004;
Raqib et al., 2006; Sur et al., 2004). Even though antibiotics are generally effective against
shigellosis, but Shigella are increasingly developing antibiotic resistance, even to the
newest antibiotics (Ashkenazi et al., 2003). Therefore the World Health Organization has
given priority to the development of a safe and effective vaccine against Shigella. (Kotloff
et al., 1999} Shigellosis, which continues to have an important global impact, cannot be
adequately controlled with the existing prevention and treatment measures. One of the ways
of prevention is to interrupt the metabolic pathway of Shigella. Shigella jlexneri poses a
metabolic gene, hemA which encodes for glutamyl-tRNA reductase enzyme. This enzyme
catalyzes the formation of glutamate-I -semialdehyde from glutamyl-tRNA Glu and NADPH
m prophyrin biosynthesis. Therefore, in this study hemA gene will be mutated by
insertional mutation technique. The most likely effect of the hemA mutation is to block or
retard the growth of Shigella jlexneri in an aerobic in vivo environment. Such mutants will
induce protective immunity against shigellosis. In the present study, hemA gene has been
successfully mutated with a kanamycin gene cassette (aphA) and the construct was
successfully subcloned into a conjugative suicide vector, p WM91. The use of the antibiotic
gene cassette is to facilitate the process of manipulating the genes as it serves as a selective
marker. The construction of hemA::aphA thus will facilitate the development of a potential
vaccine strain of Shigella jlexneri.
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