Modifying Mosquito Bacteria Can Prevent Malaria
By on July 16th, 2012

A new malaria ‘vaccine’ is being developed and might throw you some surprises. The ‘vaccine’ is a bacterium, and it won’t be administered to humans, but to the mosquitoes which transmit this virus. It makes sense, doesn’t it? We can prevent malaria by ensuring that mosquitoes don’t carry the parasite that is then transferred to humans.

Where Mosquitoes Come in

The life cycle of the malarial parasite, called Plasmodium, is dependent on the mosquito. Mosquitoes get infected when they draw blood from an infected vertebrate. The mosquito becomes the factory within which the parasite grows, and is transmitted to the next human the mosquito chooses to draw blood from.

Disinfecting the Malarial Factory

P. agglomerans is a symbiotic bacterium that lives in the guts of mosquitoes. Researchers at the Johns Hopkins University inserted genes for ‘antimalaria effector molecules’ —chemicals that are toxic to the malarial parasite— into these bacteria and then let them enter mosquitoes. As the bacterium grows inside the mosquito, the genes inserted into it produce antimalarial toxins into the mosquito’s gut. As soon as  a mosquito is infected, the parasite dies in the mosquito’s blood leaving no chance of transmission to humans. The researchers found that 84% of mosquitoes that had been infected with the malarial parasite did not have the parasite.

Mosquitoes serve as efficient vectors for the malarial parasite. [Image Credit: African Explore]


Prior to this, researchers had tried to make genetically-modified mosquitoes that had the anti-malarial genes inserted into their genetic sequences. That is, these mosquitoes would have produced the gene without the bacterial intermediary. However, this led them to a very practical problem. All the mosquitoes in the world can’t be hauled up and made to queue up to be genetically modified, can they? In order for this to be a viable solution, the genetically modified mosquitoes would have to out-survive their wild ‘normal’ counterparts so that every mosquito in the world would eventually carry this anti-malarial gene. This did not seem very feasible, at least in the present.

Because of the above reason, and because it is relatively easier to infect mosquitoes with a bacterium than it is to transfer a new gene into one, scientists came up with the bacterial solution. They propose that one way to get this bacterium into mosquitoes in the wild is to place ‘baiting stations’ of cotton balls with sugar and bacteria in villages with high prevalence of malaria. This research also throws up the possibility of modifying bacteria that live in the human gut.

Miles to Go…

However, it is to be noted that many problems associated with malarial prevalence remain. Many vaccines against malaria become obsolete because the parasite develops a resistance to these vaccines. The same could be true for the genes being inserted into the bacterium; there is no guarantee that these will always remain effective against all malarial strains. Moreover, the time frame within which mosquito populations could be engineered with this bacterium remains to be seen.

With news of viral vaccines against nicotine addiction coming out last week, it certainly looks like “GMM”s— genetically modified microorganisms— might be the next big thing in biomedical research. You can view more details of this research here.

 

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Author: Shweta Ramdas
Beginning life as a grad student studying human genetics.

Shweta Ramdas has written and can be contacted at shweta@techie-buzz.com.
 
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