Transmission-blocking vaccines ‘could hold key to malaria control’

A vaccine that prevents transmission of the malaria parasite from mosquitoes to people could hold the key to effective, population-wide control of the disease, according to researchers.

A team from German biopharma company ARTES Biotechnology has joined forces with Australia’s Burnet Institute to develop transmission-blocking vaccines (TBVs), with the help of funding from the PATH Malaria Vaccine Initiative (MVI).

Most vaccines – including GlaxoSmithKline’s (GSK) recently filed RTS,S candidate – are designed to target the liver and blood stages of malaria infection, when the parasite is injected into the bloodstream by a mosquito, travels to the liver to multiply and then infects circulating blood cells.

TBVs, however, are designed to work in a different way. Vaccinating humans with a TBV creates antibodies that are taken up by mosquitoes – along with the parasites – and prevent malaria developing in the insects.

As malarial infections tend to be transmitted within a few hundred metres of an infected person, the idea is that vaccines would provide community-level protection against the disease.

“Vaccines that interrupt the transmission of malaria aim to protect whole populations, toward the ultimate goal of malaria eradication,” according to the researchers.

ARTES and the Burnet Institute have developed vaccines based on purified vaccine antigens (Pfs25 and Pfs230) which are produced as virus-like particles (VLPs) that are taken up by immune cells to prime and prepare the immune system to fight malaria.

The German company’s vaccine-generating platform – called Metavax – can also be scaled up easily to allow low-cost, mass production of candidates, say the researchers.

Professor James Beeson, co-head of the Centre for Biomedical Research at Burnet, believes the hurdles in developing an effective malaria vaccine are substantial.

“One of the challenges for malaria is how to best make vaccines in order to stimulate a strong and effective immune response and boost the immune system to fight malaria infections,” he said.

Despite the prospect of GSK’s RTS,S reaching the market in 2016, it is well recognised that the vaccine is only partially effective against malaria so other vaccine approaches are needed in the war against malaria, which claims 600,000 casualties a year.

GSK filed for approval of RTS,S in Europe earlier this month on the strength of clinical trial data which found a 46 per cent reduction in malaria episodes compared to a placebo vaccine. The EU filing has been made under a procedure known as Article 58 – which allows the European Medicines Agency (EMA) to assess a drug or vaccine intended for use for a major public health issue that will ultimately be used elsewhere in the world.

If all goes according to plan, Article 58 approval could form the basis of approvals in sub-Saharan Africa – where the burden of malaria is felt most keenly – particularly if it is followed by a World Health Organisation (WHO) policy recommendation which could be forthcoming by the end of next year.

TBVs could conceivably be used alongside vaccines such as RTS,S and other established control strategies such as insecticide-treated bed nets and pharmacological treatment of infected individuals.

Several other groups are working on TBVs, including teams from the Jenner Institute in the UK and Ehime University in Japan.

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Malaria vaccine could be rolled out by 2015

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