"Mosquito smoothies" streamline production of promising malaria vaccine

The pursuit of a vaccine for malaria has always been an important one, with more than 400,000 people dying from the disease every year. But with the parasite behind it becoming resistant to drugs and the mosquitoes that spread it becoming more resistant to pesticides, there is a need for new, advanced weapons in the fight. A new technology could give one of our most promising malaria vaccine candidates a huge boost, by streamlining the development process through what are described as "mosquito smoothies."

Two of the most promising malaria vaccines are RTS,S vaccines and Whole Sporozoite Vaccines. The former are quite well advanced, with the World Health Organization conducting trials that recently resulted in a milestone efficacy of 77 percent, higher than any malaria vaccine ever trialed and the first to surpass its goal of at least 75 percent. Larger phase 3 trials for an RTS,S vaccine are now in the works.

Sporozoite-based vaccines are still in more experimental phases. These take the whole parasites that cause malaria, attenuate them and use them to infect people and initiate an immune response. The parasite is collected from the salivary glands of mosquitoes (from where they would normally infect bitten humans) during the early stages of its development when it's known as a sporozoite. But this process of manual extraction by a skilled technician, is expensive and time-consuming.

This new process, spearheaded by scientists at Imperial College London, could make the process far more efficient. The method involves the batch processing of whole mosquitoes, which are reduced to a slurry that is then filtered by size, density and electrical charge. This process of making "mosquito smoothies" leaves behind the necessary sporozoite products for vaccination.

“Creating whole-parasites vaccines in large enough volumes and in a timely and cost-effective way has been a major roadblock for advancing malaria vaccinology, unless you can employ an army of skilled mosquito dissectors," says lead researcher Professor Jake Baum, from Imperial College London. "Our new method presents a way to radically cheapen, speed up and improve vaccine production.”

In addition to making the process faster and cheaper, the technique can also make the vaccine more potent. Traditional extraction of sporozoites brings with it contaminants such as unwanted proteins and other debris, which can affect the infectivity of the sporozoites and possibly the immune system response, compromising the efficacy of the whole parasite vaccine. Conversely, the mosquito smoothies result in pure uncontaminated samples.

"With this new approach we not only improve the scalability of vaccine production, but our isolated sporozoites may actually prove to be more potent as a vaccine, giving us additional bang per mosquito buck," says first author Dr Joshua Blight.

The scientists used their new process to produce a malaria vaccine for rodents, which showed 60 to 70 percent protection when exposed to an infected mosquito bite. These were administered into the muscle, and the scientists found when they administered the vaccine directly into the bloodstream instead, it offered 100 percent protection.

The scientists are now refining the technique with an eye to moving toward human trials, in which participants would be administered the vaccine and then bitten by infected mosquitoes.

The research was published in the journal Life Science Alliance.

Source: Imperial College London