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Mosquito gut bacteria genetically engineered to curb spread of malaria

23 July 2012
Appeared in BioNews 666

Genetically modified (GM) bacteria may be a new weapon in the fight against malaria. Researchers have altered the genome of a bacterium that lives in mosquitoes' guts so that it secretes proteins that are toxic to the malaria parasite. In a study published in the journal PNAS (Proceedings of the National Academy of Sciences), this approach was 98 percent effective in reducing the malaria parasite burden in mosquitoes.

The research team from the Johns Hopkins Bloomberg School of Public Health in Baltimore in the USA modified the Pantoea agglomerans bacterium so that it released several proteins which attack malaria parasites. 'There are not one, but several anti-malaria compounds the bacterium secretes', explained Professor Marcelo Jacobs-Lorena, leader of the study. 'Each acts by a different mechanism and makes it much more difficult for the parasite to develop a resistance to it'.

Scientists had previously attempted to combat malaria by genetically modifying the mosquitoes themselves to be resistant to the malaria parasite. Although this method was effective in the laboratory, it has proved difficult to introduce the modified insects into the wild. 'Genetic modification of bacteria is a simpler approach', said Professor Jacobs-Lorena. 'These findings provide the foundation for the use of genetically modified symbiotic bacteria as a powerful tool to combat malaria'.

When a mosquito bites a human or animal infected with malaria, the parasite enters the mosquito's midgut and reproduces. Worm-like sporozoites, the precursor germs that enable malaria to spread, are produced and navigate to the insect's salivary glands, ready to infect anyone the mosquito bites. Pantoea agglomerans is also found in the midgut, and can theoretically be contracted by all malaria-carrying mosquito species.

The challenge is now to successfully introduce the GM bacteria into the wild. Professor Jacobs-Lorena believes that this could be achieved by using 'sugar stations' in the malarial regions of Africa and South-East Asia. Having been genetically engineered within the laboratory, the bacteria can be introduced by loading them onto sugar-coated cotton balls which mosquitoes feed off.

Further complications include ensuring the GM bacteria can survive and compete with non-modified ones, and convincing local populations and anti-GM groups that the new strain poses no danger.

Professor George Dimopoulos, malaria researcher and colleague of Professor Jacobs-Lorena said of the new technique: 'It relies on a GM bacterium which can't be contained once released in mosquito populations, and will easily end up in the food chain and eventually also on people's plates. While such bacteria may not pose a hazard to humans and animals, the work required to prove, educate and finally convince various stakeholders that the implementation is safe will be lengthy and challenging'.

Malaria is one of the most prevalent fatal diseases in the world. According to the World Health Organisation, there were about 216 million malaria cases and an estimated 655,000 deaths in 2010. Most of those affected are African children under the age of five.
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