New malaria vaccine candidate ready to enter Phase I trials

Research lead | Development lead

An international team of researchers led by Simon Draper of Oxford University, UK, has developed a malaria vaccine using modified cold and pox viruses to deliver malaria antigens. The vaccine offers complete protection in a mouse model of the disease and strongly limits the growth of human malaria in vitro.

In the research, which was part funded by the Wellcome Trust and the UK Medical Research Council, the scientists genetically modified an adenovirus that causes the common cold, and a pox virus, so that they both express an antigen found in the malaria parasite’s coat.

This approach has been used before to evoke the T-cell immune response needed to destroy the malaria parasite in the early stages of infection in the liver.

Now however, the researchers have also managed to trigger the production of antibodies, which are necessary to fight the parasite in the later stages of the infection in the blood.

The unanticipated effect is a result of long-term fine tuning, both in terms of the make-up of the vaccine and in the timing of the prime vaccination and the follow-up booster jab.

“This work is the end of a slow iterative process,” said Draper. “We had to modify the viruses, for example by improving the gene promoter in the adenovirus, and optimise the time interval between the prime vaccination and the booster jab. In the end however, the results were startling, and we could use these viruses to induce very high levels of antibodies for the first time.”

On the basis of these data the researchers have obtained a grant from the MRC to move into Phase I clinical trials on healthy volunteers starting next year. In the meantime they are finalising and producing human vaccine.

Although there are other malaria vaccine trials in progress, this is the first which will use this delivery method to target blood-stage malaria.