GMO Description


The bacteria that causes cholera (Vibrio cholerae) has been genetically modified to remove its ability to cause disease. The modifications were: deletion of the genes encoding the cholera toxin A-subunit (leading to attenuation); inactivation of the gene encoding haemolysin A (also leading to attenuation); and insertion of a mercury resistance operon from Shigella flexneri (as a selectable marker). The GM cholera vaccine is currently known as PXVX0200.

Parent Organism:
Common Name:Cholera bacterium
Scientific Name:Vibrio cholerae strain 569B
Modified traits:
Categories:Loss of toxin expression/ Vaccine attenuation

Gene inactivation/ Vaccine attenuation

Selectable marker expression
Description:
  • deletion of Cholera toxin A subunit gene (ctxA) (loss of toxin expression - vaccine attenuation)
  • inactivation of haemolysin A gene (hlyA) (loss of toxin expression - vaccine attenuation)
  • insertion of mercury resistance operon (mer) from Shigella flexneri NR1 (selectable marker – mercury resistance)

Purpose of the dealings with the GMOs:


PaxVax Australia will be conducting a clinical trial of a genetically modified cholera vaccine involving volunteers covering different age groups. This trial would form part of an international clinical trial and would involve up to 1000 participants in Australia. The purpose of the trial is to verify the effectiveness of the vaccine in producing an immune response against cholera.

Genetic elements responsible for conferring the modified traits:


Gene
Full name
Function of protein
Intended purpose
ctxA
Cholera toxin A subunit gene
deletion of Cholera toxin A subunitvaccine attenuation
hlyA
haemolysin A gene
inactivation of haemolysin A genevaccine attenuation
mer
Operon
mercury resistance operon from Shigella flexneri NR1
confers mercury resistanceselectable marker
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