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A Better Vaccine

A new vaccine against bovine and human tuberculosis has been developed by the Department of Microbiology at the University of Otago.

The vaccine is an improved version of BCG (Bacille Calmette Guerin), the most widely used vaccine in existence, administered to more than three billion people since 1948 [A Multipurpose Vaccine, March 1999].

"Some researchers say that BCG doesn't work too well and have therefore started to look into new and different types of vaccines," says Dr Glenn Buchan, senior lecturer in immunology.

However, a closer look at BCG shows that it works well enough in some countries and not in others.

"The difference is that it does not work well in countries or communities where people are poor," Buchan says. "If a person's immune system is weakened because of stress, malnutrition or genetic factors, then [the] normal vaccine doesn't trigger an immune response capable of protecting them from disease. The same holds for animals such as deer, cattle and possums."

This led to a Public Good Science Fund-aided project to study how to get a better response from BCG vaccines. By using mice and deer, researchers have found that immune hormones called cytokines have a role. Natural proteins of the body, they regulate the body's defence against infection.

"We're using one of these, Interleukin 2, to test our hypothesis," Buchan says. "We have made a BCG vaccine that makes the Interleukin 2. The Interleukin 2 stimulates the immune response to be more effective in killing the tuberculosis. We have shown that this improved vaccine is safe."

The vaccine is undergoing more testing.

"Our primary interest is to protect cattle, deer and feral animals such as possums and ferrets against bovine Tb."

The work on mice has shown that animals with weakened immune responses respond better to the new vaccine than they do to the "normal" BCG and that their responses are the same as for healthy animals.

"We believe that other vaccines might also be improved by this method," Buchan says.

His team is also looking at how to improve the body's defence against influenza.