Incredulity turns to praise as malaria vaccine posts positive PhI data

In the 1970s, experiments showed that volunteers developed immunity from malaria after irradiated infected mosquitoes bit them thousands of times. Understandably, this immunization method never went mainstream, but a vaccine based on the underlying science just might.

While an immunization method based on biting is impractical, Maryland-based biotech Sanaria saw there are other ways to get the irradiated parasites into people. Sanaria has spent the past decade harvesting parasites from the salivary glands of mosquitoes to use in malaria vaccines. The resulting vaccine uses a weakened form of the whole parasite to generate an immune response. Other malaria vaccine candidates use proteins found on the surface of the parasite, but, as Sanaria observed, these recombinant, subunit designs have had little success.

Phase I results of the Sanaria vaccine, called PfSPZ, suggest it could offer better protection. Data published in Science shows the six subjects who received five doses intravenously were 100% protected from infectious mosquito bites. In contrast, five of the six people in the control group contracted malaria. The data has excited the malaria research community. "The trial results constitute the most important advance in malaria vaccine development since the first demonstration of protection with radiation attenuated sporozoite immunization by mosquito bite in the 70s," Seattle Biomedical Research Institute malaria researcher Stefan Kappe told Nature.

The response was a little different when Dr. Stephen Hoffman founded the company in 2003. In a 2004 article, Nature reported other malaria researchers responded to his plans with a mixture of curiosity, incredulity and admiration. Many doubted if a vaccine based on harvesting billions of parasites from the salivary glands of mosquitoes could pass quality and safety standards. Advancing the vaccine into Phase I shows the manufacturing process--which involves raising mosquitoes in sterile conditions, infecting them with malaria and then irradiating--is viable.

Doubts remain about practicality of the vaccine though. PfSPZ is delivered intravenously, making it less well suited to mass vaccinations than oral forms or injections into the skin. Sanaria is looking for a more convenient way of delivering the vaccine. The need to keep the vaccine frozen in the liquid nitrogen vapor phase is another potential problem, but Hoffman and others argue this infrastructure is already in place to transport semen for artificial insemination of livestock. "If you can carry semen into the deep Saharan belt and remote areas, why can't you do that for a human vaccine?" Swiss Tropical and Public Health Institute director Marcel Tanner said.

- read Nature's article
- check out the BBC's take
- here's the Science abstract