Sunday, 1 April 2012

The War on Vector Diseases: Malaria Resistant Mosquitos


Emily Daubney, 42615226

Can you imagine a world without Malaria? Did you know that Malaria is responsible for over one million deaths each year? Scientists today are looking at using genetic engineering to modify mosquitos so as they are resistant to malaria parasites.

Mosquito de la malaria (Anopheles)
Original source located here.
Why go down this path of investigation do you ask? It’s simple really, although many other alternatives are being investigated this one shows great potential. Malaria is the most deadly vector borne disease, caused by a protozoan parasite, Plasmodium carried and injected by the genus of mosquitos the Anopheles. One of the other paths of inquiry is a vaccine. However due to the antigenic variation of the parasite malaria progress on a working vaccine has been unsuccessful. The reason it’s so hard to develop a working vaccine is because antigenic variation means that the parasite has the ability to change coat antigens during the course of infection making it hard to predict a common pattern to target. An example of antigenic variation is shown in the image below which shows how the coding for human influenza can be changed over time. There are also issues which are making malaria hard to treat hence the need to look at alternative solutions allowing for eradication of malaria such as genetic engineering.
Original source located here.

Original source located here.
There are a range of methods for genetic engineering which is manipulation of an organism’s genome; the particular approach being explored to modify mosquitos to be malaria resistant is microinjection. The technique of microinjection involves incorporating foreign DNA into a living cell. The image to the left shows how it is possible through use of enzymes to take a DNA segment and creates an incision in the DNA in the living cell in which the foreign DNA segment is being injected. Microinjection is a particularly successful method as it allows for both reproducibility and reliability.

The aim is to genetically engineer mosquitos through microinjection in such a way that they carry genes that confer pathogen resistance. There are a number of successful experimental variants in this process. An example is that of the mariner element which has been successfully used to transform Ae. aegypti as well as reports of success using the piggyback element on this mosquito. The mariner element and the piggyback element are transposable elements which create the incision allowing for the insertion of the new DNA. The research focuses on the avian malaria model as opposed to malaria parasites that infect humans and how this model could possibly be used to predict outcomes of experiments using human malaria parasites.

Even though there has been success on some level in modifying mosquitos which are either unable to transmit or develop malaria parasites in the avian model there is still the issue of how accurately this  model can be used to predict outcomes of experiments using human malaria parasites. Another possible issue that could be faced further down the track is how these genes can be spread through the target population. Unfortunately there are many problems and unknowns that could arise from this particular solution and there are certain to be many more encountered in the future. But until then this alternative solution shows great potential.


Resources

Cain, M, Cooke, B, Jackson, R, Meyers, J, Minorsky, P, Reece, J, Urry, L & Wasserman, S 2012, Campbell Biology, 9th edn, Pearson, Australia, pp. 442-443.

Hickman, M & Thain, M 2004, Diction of Biology, 11th edn, Penguin Books, Victoria, pp. 39, 427.

James, AA 2002, ‘Engineering mosquito resistance to malaria parasites: the avian malaria model’, Insect Biochemistry and Molecular Biology, vol. 32, pp. 1317-1323.

World Health Sciences 2010, Malaria viewed 16 March 2012, <http://www.worldhealthsciences.com/malaria.html>

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