Malaria vaccine ready for human trials

Posted by Emma Woollacott

Melbourne, Australia - The first genetically-engineered malaria vaccine, developed with funding from the Bill & Melinda Gates Foundation,  is about to enter human trials.

Malaria kills around a million people each year, and existing vaccines have proved unreliable.

Now, Walter and Eliza Hall Institute scientists have created a weakened strain of the malaria parasite that will be used as a live vaccine against the disease. The vaccine, developed with funding from the Bill & Melinda Gates Foundation, will be trialled in humans from early next year.

Professor Alan Cowman, head of the institute's Infection and Immunity division, said in developing the vaccine the research team had deleted two key genes in the Plasmodium falciparum parasite – which causes the form of malaria most deadly to humans. By removing the genes the malaria parasite is halted during its liver infection phase, preventing it from spreading to the blood stream where it can cause severe disease and death.

Professor Cowman said similar vaccines had been tested in mice and offered 100 per cent protection against malaria infection. He said it was hoped the vaccine would produce similar results in humans. "Although two genes have been deleted the parasite is still alive and able to stimulate the body's protective immune system to recognize and destroy incoming mosquito-transmitted deadly parasites," Professor Cowman said.

This approach to vaccine development – using a weakened form of the whole organism – has proven successful in eradicating smallpox and controlling diseases such as flu and polio.

"Although vaccines are under development that use whole malaria parasites weakened by irradiation to protect against infection, their safety and effectiveness rely on a precise irradiation dose and trial results have been variable," Professor Cowman said. "We believe that our genetically attenuated parasite approach provides a safe and reproducible way of developing a whole organism malaria vaccine."

The details are published in the current issue of the Proceedings of the National Academy of Sciences USA.