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Scientists Just Found One of The Most Promising Malaria Vaccine Targets to Date

This is how we stop malaria grabbing onto our blood cells.

MIKE MCRAE
11 FEB 2017
 

In spite of a decade of intense research, we still don't have a commercially available vaccine for malaria.

While a candidate vaccine is being piloted next year, scientists have found a potentially more promising target in the bridge malaria makes with our red blood cells, which could lead to a more effective, cheaply made vaccine.

 

There are half a dozen species of the plasmodium parasite responsible for causing malaria in humans, with P. vivax and the extra nasty P. falciparum being the two most common. They are all spread through the bite of infected mosquitos, affecting 97 countries and territories world-wide. 

In 2015, plasmodium made 212 million people sick and took roughly 430 thousand lives, mostly children under the age of 15.

If these numbers seem big, we've seen a marked improvement over the past 15 years. Mosquito netting and insecticides have helped reduce the number of cases since 2000 by 22 percent, while fatalities have been halved.

The World Health Organisation's Global Technical Strategy for Malaria has set a goal to wipe the disease out completely in at least 10 countries by 2020, and reduce cases by 40 percent in all other countries where the disease is endemic.

Yet we still have far to go if we're to eradicate what is considered to be one of the deadliest diseases that's threatening our modern world.

A powerful weapon in the fight against the parasite would be a cheap, stable vaccine which could be distributed through the world's remote, poorer populations.

 

One promising candidate is the RTS,S vaccine - also known as Mosquirix - which will be piloted in Africa next year. If it works as hope, it could cut down infections in young children by half.

Yet the search is still on for even more effective tools capable of providing solid immunity against the blood-invading parasite.

With that in mind, a team of researchers at the Wellcome Trust Sanger Institute has turned its focus a chemical the pathogen uses to link itself to the host's red blood cells. 

The molecule, dubbed RH5, was found in previous research to connect a red blood cell receptor called basigin, somehow sticking the two cells together. Another two proteins, CyRPA and RIPR, were found to form a complex with RH5. The details, however, were still hazy.

Now the researchers have discovered precisely how this process works.

Plasmodium parasite sticking to a red blood cell.Sanger Institute: Genome Research Ltd

As the plasmodium secretes the RH5 protein, a receptor on its surface called P113 grabs hold, allowing it to anchor itself to a red blood cell long enough to slip inside. The other two proteins were found to stick to one another, with CyRPA then connecting with a specific spot on RH5.

The research revealed just a small area of RH5 was used to connect to the plasmodium receptor, hinting at the possibility of producing a 'blocker' easily and cheaply.

One of the team members, Julian Raynor, explained how this is exciting news for making a cost effective multi-component vaccine.

"We knew both proteins were essential for invasion but this is the first time anyone has seen the interaction between RH5 and P113 and showed that they work together.

In theory, an antibody that blocked P113 could stop RH5 binding and so prevent the parasite from gaining entry to red blood cells. This makes the P113 protein another good vaccine target."

The RH5 protein complex is the vital link between the malarial parasite and our blood cells. Finding ways to target it with a vaccine could lock the pathogen out of our bodies, putting us one step closer to a malaria-free future.

This research was published in Nature Communications.

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