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Infectious disease molecular biology

31 Oct 2007   The search for a better TB vaccine

The search for a better TB vaccine

The Hopkirk's Molecular Biology team is charged with producing a new, more effective  vaccine for the prevention  of tuberculosis (TB).

The costly cycle of re-infection and the increasing unpopularity of chemical controls to eradicate possums have led scientists to believe the best solution is to stem the tide of TB infections at the source. And the best way to do this is by vaccinating the possums.

Funded by the Foundation for Research, Science and Technology (FRST), the team is undertaking research that has already identified at least one potential vaccine strain that protects possums more than the existing Bacillus Calmette-Guérin (BCG strain).

It's a long process, however, because the scientists have to test each strain and unravel its genetic and biochemical characteristics to discover what combination of characteristics will make the best final vaccine.

"As you go through the process, you introduce mutations into a virulent strain, test each strain to see if it still causes disease and, if it doesn't, test its efficacy as a vaccine," says Dr Des Collins who leads the team.

"It's a case of identifying the best genes to disrupt that will give us the best vaccine, and trying to understand what makes a good vaccine strain at the molecular level.

"Ultimately, we want to produce a vaccine strain that carries targeted disruptions in two or more genes, but without any additional genetic material - no antibiotic resistance gene, for example."

An important aspect of the work is determining how to immunise wild possums with better vaccines. Research funded by the Animal Health Board that involves the University of Otago and the AgResearch Infectious Diseases Immunology team has shown possums can be effectively immunised against TB by eating special baits that contain vaccine.

"A vaccine against TB in possums will reduce many of the continuing costs of controlling the disease, as well as the threat to market access," says Des.

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