Australian scientists have discovered a "key molecule", which can kill microbes that infect the human liver, a breakthrough experts believe could bring a malaria vaccine one step closer.

Researchers at the Australian National University (ANU) announced the breakthrough after they tracked cells and discovered a molecule which kills microbes that infect the liver - such as malaria, Xinhua news agency reported.

Malaria kills around half a million people every year in warm climates such as in Africa and Asia, but lead researcher Hayley McNamara from the ANU said the findings helped answer questions about the mystery of "T-cells" - immune cells which hunt down infections in the body.

"We know T-cells can protect against most infections, what we still don't fully understand is how these T-cells find the rare cells infected with viruses or parasites like malaria - a needle in a haystack problem if you like," McNamara said on Monday.

"We've found that without a key molecule called LFA-1, that cells don't work - they can't move quickly and can't kill malaria parasites effectively."

Associate professor Ian Cockburn from the ANU said that because the T-cells were able to effectively hunt down malaria parasites, they could one day become a major component of future malaria vaccines.

"What we want to do is understand how to make a vaccine that induces these types of immune cells. There are vaccines in clinical trials that work by inducing antibodies, adding a T-cell component would create stronger immunity by arming different parts of the immune system," he said.