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'Promising' malaria vaccine developed
Dec 02, 2013

Oxford scientists have developed a novel new malaria vaccine which can protect against the deadly mosquito-borne disease.The vaccine has shown promising results in the first clinical trial to test whether it can protect people against the disease.

The trial was carried out by researchers led by Professor Adrian Hill of the Jenner Institute at Oxford University, along with colleagues from the biotechnology company Okairos.

It's the first time that a vaccine has been shown to have a protective effect through a sufficiently high immune response involving cells called CD8 T cells. It is CD8 immune cells that are seen to mount a protective response against malaria in similar studies in mice. Every existing vaccine in use - bar one - generates antibodies.

But there are two arms to the body's immune system for fighting infection: antibodies and T cells. And this vaccine aims to stimulate an immune response involving T cells.

CD8 T cells are important because they are the primary killer cells in the immune system. They can attack nearly all types of infected cells in this case liver cells infected with the malaria parasite. But this first demonstration of a large CD8 response from a vaccine could be relevant for tackling other diseases too.

The vaccine was found to work by inducing CD8+ T cells that target the malaria parasite in the liver.

The Phase II a trial involved 36 people in total, of which 14 healthy adults received two different virus-based vaccines with the same malaria antigen eight weeks apart. Of those 14, three people were protected from the bites of malaria-infected mosquitoes.

A further five had delayed onset of malaria, demonstrating that over 90 per cent of the malaria parasites had been killed by the vaccine-induced immune response.

Importantly, the size of the CD8 T cell response in these volunteers correlated with the degree of protection from malaria, suggesting that a sufficiently high cellular immune response is protective.

Ten further volunteers received only one of the vaccines and there were 12 controls. None of these people saw any protection against malaria from mosquito bites on the arm.

All volunteers were closely monitored for malaria symptoms throughout, and those getting the disease were treated rapidly with drugs. The trial results are published in the journal Nature Communications.

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