Our project

Our team wants to help stopping the propagation of malaria, a disease which has a death toll of over a million per year. Malaria is transmitted by the parasite Plasmodium whose life cycle is well-studied: The mosquitoes are the vectors which propagate the infection to humans. The infected human will then again infect mosquitoes consuming a blood meal which then completes the cycle.

Bacteria of the genus Asaia have been proven to be stably associated to a malaria propagating mosquitoe, Anopheles stephensi [1]. We plan to take advantage of this and use engineered Asaia to block the Plasmodium cycle.

Our project (derived from the summary we wrote with Henrike)

Malaria is a tropical disease that kills more than 1 million people each year, and no effective cure or vaccine exists yet.

The EPFL iGEM project aims to stop the malaria propagation by acting on its vector: the mosquito. We want to engineer Asaia, a bacterium that naturally lives in the mosquito's gut, to kill or inhibit the Malaria parasite, Plasmodium falciparum, before it can infect the mosquito.

To do so, we will make Asaia express proteins, which specifically bind to plasmodium membrane-proteins. First we will express an immunotoxin that lyses the parasite. Next, we will try to prevent the plasmodium infection by inhibiting surface P-proteins, which are necessary for the fusion of the gametes and the crossing of the intestinal epithelium.

The main advantage of our approach is that it does not wipe out the mosquitoes, which might have unwanted effects. Rather we will only alter their gut flora, which should not have any harmful side effects apart from stopping Malaria transmission.

Asaia is an organism that is easy to grow and manipulate and that is not dangerous for humans. Therefore, we are establishing Asaia as a new chassis so that future iGEM teams can quickly and efficiently engineer new and more potent Asaia strains. This will provide the synthetic biology community with a useful tool in the fight against malaria and other mosquito-borne diseases.

About us

We are a group of ten students from various backgrounds (Life Sciences, Microengineering, Computer Science and Physics) united by our interest in synthetic biology. We are looking forward to representing EPFL at the 2010 iGEM competition!

Become a fan of our team on [http://www.facebook.com/pages/EPFL-iGEM/117887404918202 facebook], if you want to receive news from us and follow our progress in the lab. You can also follow us on twitter!!

Our progress

We are now in our third week in the wet lab. Apart from training basic lab skills like making a PCR and running a gel we are growing Asaia and studying its properties. Furthermore we finished our first biobrick containing an origin of replication for Asaia.

Within the next week we also plan to test the propagation of Asaia within Drosophila.

Gwen: I suggest to suppress this, I don't really know what we could say that would not be redundant with our results page. Or maybe we can make a "Results" section and quickly summarized everything we achieved directly on the homepage. I've seen this in the heidelberg wiki, and they won the wiki prize... :p (but i still suggest to suppress "our progess" ^^ )

Our plan

The bacterium Asaia was chosen as a chassis mainly since it is naturally present in the mosquitoes gut. Furthermore it is transmitted vertically (to the offspring) and horizontally (during reproduction) which enables the engineered Asaia to propagate within a mosquito population.

We have discussed several ways of blocking the Plasmodium in the gut of the mosquito. We plan to test the following two approaches:

• Asaia produces an immunotoxin consisting of an antibody, which will bind to a specific site on the plasmodium and a toxin (a porin, which will perforate the cellular membrane of the parasite).

• p25 p28 are ookinete (a specific form of the plasmodium) surface proteins. It has been shown [2] that those 2 proteins are necessary to the ookinete to go through the gut's membrane. We therefore want to engineer Asaia to express p25 and p28 on its own surface to compete with the surface proteins of the plasmodim, thus reducing its efficience.

The BioBrick we aim to ship to the registry will contain the plasmid vector to work with Asaia, thus making from Asaia a new chassis ready to use ; one plasmid containing the "immunotoxin system" and one plasmid containing the "p25 and the p28 system".

Once the caracterisation of those BioBricks is done we are going to work on the release system of the Immunotoxin. This could be done by lysis of the cells or ideally by secretion.

As a last and very challenging step we consider the option of a blood sensor, which triggers lysis or secretion. This would greatly increase the probability that there is a sufficient amount of immunotoxin to stop the plasmodium from being able to travel to the salivary gland and hence being transmitted to the next victim.

[1] http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1885625/

[2] http://www.nature.com/emboj/journal/v20/n15/full/7593895a.html

Acknowledgements

• We thank Prof. Guido Favia and Dr. Claudia Damiani from the University of Camerino for the Asaia strains and their helpful advice and protocols on how to grow and manipulate Asaia.
• We would like to thank Prof. Bruno Lemaitre from EPFL for his advice and the possibility to conduct experiments with drosophila in his lab.
• We thank the Maerkl lab for bearing our presence in the lab. :)