A study by Dimopoulos et al. has revealed a novel way to eradicate the malaria parasite. The scientists from Johns Hopkins Bloomberg School of Public Health found that by using a gene silencing technique, the Anopheles mosquito's immune response to the human malaria parasite Plasmodium falciparum is increased, enabling resistance to this parasite.

The scientists used the RNAi gene silencing technique, which involves introducing double-stranded RNA that specifically targets a particular gene, interfering with the gene's activity and effectively silencing the gene.

They used RNAi to silence the gene caspar, which encodes a negative regulator of Rel 2, a transcription factor in the immune signaling pathway of mosquitoes. By silencing caspar, they found an increase in Rel 2 mediated transcription of immune genes, including those encoding anti-Plasmodium effectors, which results in parasite killing. They measured the amount of parasites killed by counting the parasite oocytes in the mosquito's gut.

To test the universal relevance of this defense mechanism, they tested the effect of caspar silencing across three Anopheles species, A. gambiae, A. stephensi and A. albimanus (major malaria vector found in Africa, Asia and South America respectively). They found that caspar silencing prevented the development of P. falciparum in all three species.

The scientists pointed out that caspar silencing did not have an effect on the mosquito's longevity or fitness in this context. They also pointed out that this immune induction against P. falciparum was only temporary, due to the kinetics of the RNAi process.

In applying these findings to the wider context of malaria control, it will be crucial to find a more permanent gene silencing technique as well as an efficient RNAi delivery system in the large scale. We are years away from finding an effective, cost efficient tool for inducing resistance to P. falciparum in mosquitoes in the field, but this study certainly opens up the door for more research into this alternative method for Malaria control.

Ref:

 1. Dimopoulos, G. et al. Caspar controls resistance to Plasmodium falciparum in diverse anopheline species. PLoS Pathog. 2009 Mar; 5(3):e1000335. Epub 2009 Mar 13.

2. Eder, M., Scherr M. Gene silencing by small regulatory RNAs in mammalian cells. Cell Cycle. 2007 Feb 15;6(4):444-9. Epub 2007 Feb 5.

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Wipe out Mosquitos Instead
written by jaya wardene , April 20, 2009

The problem of malaria has baffled minds for centuries. Back in the days when we had working institutions I remember seeing armies of Nairobi City Council workers clearing the long grass and the drains, getting rid of pools of stagnant water and spraying ponds during the mosquito breeding season. The idea was to make it difficult for this irksome pest to breed around the populated areas thereby reducing the incidence of malaria.

This proposed new fangled method of control sounds a bit like a jua kali way of fooling Jayawardene with high tech sounding gibberish. Why do scientists and others seem to think that people will listen as long as you mention DNA or RNA? Isitoshe Jaya believes that this ridiculous proposal is nothing more than a clever ploy by researchers to extract huge funding from the drug manufacturer Barons who continue to benefit as long as malaria reigns in the 3rd world.

Malaria is ultimately caused by the plasmodium parasite. The only access that this little monster has to your body is non other than the blood sucking anopheles mosquitos. Can these eminent scietists please explain to me why we just don't eradicate this pest once and for all?

Mankind has managed to consign many animal and plant organisms into extiction. I would shed no tears of we included all the variants of the anopheles blood sucker and its close relative the politician in that list.

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The mosquito plans ahead
written by John Ongeri , April 24, 2009

Whilst we sit bickering about who said what to whom the mosquito marches ahead claiming more victims and preparing itself to do battle
http://www.nation.co.ke/News/-...index.html

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Been there, done that
written by snkariuki , April 29, 2009

Jaya, it is true that the prevention measures in place against Malaria all involve methods to get rid of the mosquito vector. These measures include use of insecticide-treated bed nets, indoor spraying of insecticides, and as you mentioned, environmental control to get rid of mosquito breeding sites.

However, as John Ongeri has pointed out above, whether the scientists agree or disagree on this point, we do have to worry about an increasing resistance by mosquitoes to the insecticides that are currently being used-DDT and pyrthroids. According to the WHO, there is no efficient and effective alternative to these key insecticides. Completely annihilating the mosquito is not exactly a simple thing.

So with the mosquito outsmarting us and trying to survive by any means necessary, shouldn't we look into alternative methods of Malaria control? I think we should be objective when analysing these findings. What I liked about this study was that it presents a novel way of fighting the Plasmodium parasite: harnessing the mosquito's immune system early on so as to kill off the parasite before it gets into the mosquito's salivary glands, and subsequently, into the human host. Certainly more work needs to be done in terms of figuring out how this RNAi technique can be applied to mosquitos on a larger scale in the field, but this is certainly an interesting departure from your usual drug and insecticide intervention.

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