Concern over malaria trial

A TRIAL vaccine against malaria is using weakened parasites from fly spit to build up human resistance to the disease, but experts have questioned whether the approach is practical.

Malaria kills an estimated one million people around the globe each year. The parasite that causes the disease is carried by mosquitoes and transmitted to humans through bites from infected female flies.

Current advice includes using bed nets and insecticides to stop parasite-laden mosquitoes from biting, and taking preventative drugs when visiting certain endemic regions.

Meanwhile, several potential vaccines are in the pipeline, the most advanced of which is being developed by pharmaceutical giant GlaxoSmithKline.

But last week US biotech company Sanaria announced it was starting early clinical trials of another vaccine candidate, which uses a weakened version of the whole malaria parasite. To generate the vaccine they infect Anopheles mosquitoes with the parasite Plasmodium falciparum, then irradiate the flies to render the parasite harmless. The weakened parasite is then harvested from the salivary glands of the mosquitoes, to be injected into humans so the immune system can develop resistance.

The new clinical study will involve about 100 healthy volunteers and inoculations are expected to start in mid-May, according to Sanaria, which is supported by the PATH Malaria Vaccine Initiative.

“When the attenuated parasite is given to individuals, they are expected to become immune to malaria and not get sick,” said a statement from Sanaria that described the trial as a “watershed event”.

However, experts have expressed doubts to The Irish Timesabout whether the resulting "whole parasite" vaccine would be widely useful.

“[Clinical] studies might be okay but when it comes to the field then it’s problematic because there are so many strains of malaria, and how strain-specific is this vaccine going to be?” asked malaria expert Prof Lars Rombo from the Karolinksa Institute in Sweden, who addressed the Irish Society of Travel Medicine (ISTM) in Dublin last weekend.

Concerns about the vaccine being too specific were echoed by Dr Dom Colbert, a co-founder of the ISTM and lecturer in tropical medicine at the Royal College of Surgeons in Ireland.

“It’s an interesting approach, but there is a lot of scepticism about it,” he said.

Dr Colbert also warned against targeting efforts against a single species of malaria-carrying mosquito. “I fear if you get rid of one , an even more aggressive one will come to replace it,” he said.