Australasian Science Magazine

By Stephen Luntz

Of all the diseases that are developing resistance to antibiotics, pulmonary tuberculosis (TB) is by far the largest killer. One-and-a-half million people die of the disease each year, about one-quarter from co-infection with HIV.

“The existing needle vaccine is effective against childhood TB, but not so much against pulmonary TB, which is what most adults get,” says Dr Joanna Kirman of the University of Otago’s Department of Microbiology.

The vaccine is based on a closely related bacterium attenuated by French scientists and named Bacille Calmette-Guerin (BCG) in their honour. Kirman says that efforts are underway worldwide to improve the effectiveness of this vaccine.

Kirwin says that the immune system is compartmentalised so that cells go to where they are most needed. Since the mucosal immune system unites the gut and lungs, an orally administered vaccine is a better shot than delivery by needle.

However, the live bacteria in the BCG vaccine cannot survive the stomach’s harsh environment. “Growing bacteria are required to produce the proteins required for the immune response,” Kirman says. Her colleagues produced a lipid formulation called LiporaleTM that provides a protective coat for the bacteria, and Kirman tested this on mice.

“LiporaleTM–BCG vaccination induced a long-lived immune response, evident by the detection of increased numbers of tuberculosis-specific T cells in the lungs and spleen up to 30 weeks after vaccination,” Kirman says. The findings were published in PLOS ONE.

Not-for-profit development organisation AERAS is conducting experiments on the vaccine by exposing animals to bacteria from hospitals, where antibiotic-resistant strains are increasingly common. Kirman plans further investigation of the safety and mucosal immune response generated by the vaccine before clinical trials can begin.

A better vaccine cannot come fast enough for doctors at the frontline. “In 2010 New Zealand had its first case of extensively drug-resistant TB (XDR TB), which is incredibly difficult, and sometimes impossible, to treat,” Kirman says. “That is why we think prevention through vaccination is so important.”