Our Idea

Our goal is to develop a cheap, practical, and effective diagnostic test for the parasite T. solium in humans. We call this test Wormspotter. Wormspotter will respond to RNA molecules from T. solium in order to detect a tapeworm infestation. RNA (Ribonucleic acid) is the basis of protein production, and every species, including T. solium, has specific RNA molecules which can be used to unambiguously identify it. We plan to take advantage of this in our diagnostic method.

Wormspotter will be based on a newly developed method called toehold switch sensors. This method has already been successfully applied to the diagnosis of the Zika virus [1]. We are therefore convinced that toehold switch sensors will also be useful in detecting T. solium.

In order to develop Wormspotter, we first need to achieve two things:

  1. Production of toehold switch sensors to detect RNA specific to T. solium
  2. Creation of model RNA molecules to test Wormspotter

Once these stages are complete, they will need to be brought together so that we can test whether Wormspotter can recognise and react to RNA from T. solium. We aim to achieve this in a cell-free system.

 

The experiments

Production of toehold switch sensors

Toehold switch sensors are based on synthetic biology. Essentially, they are RNA molecules which code for a reporter protein. They consist of a specific toehold sequence, a ribosome-binding site (which is important for the production of proteins) and a sequence for the reporter protein. The reporter protein can only be produced if the sensor has bonded with its specific target RNA sequence [2].

When producing the sensors, we can select both the toehold sequence and the reporter protein with complete flexibility to match our needs. In this way we can fashion our Wormspotter so that it only sends a desired signal when it binds to RNA molecules specific to T. solium.

We are planning to use T. solium-specific RNA sequences for the toehold sequence and beta-Galactosidase as a reporter protein.

 

Creation of model RNA molecules

In order to test whether our toehold switch sensor generally binds to RNA from T. solium, we will create a variety of model RNA molecules. These molecules must be specific to T. solium. Our plan is to use two different RNA molecules which have already been successfully used to identify T. solium [3,4].

Toehold switch sensor test

We will then combine the toehold switch sensors and model RNA molecules in a cell-free expression system. These systems can produce proteins, just like in a normal cell. However, they are completely synthetically produced, and therefore provide extremely controlled reaction conditions.

We will subsequently be able to verify whether the reporter protein beta-Galactosidase was produced in the cell-free system. If it is present after adding our model RNA molecules, this will serve as proof that the toehold switch sensor reacts specifically to T. solium RNA.

Application

The synthetic biology experiments described here are particularly important for participation in the iGEM competition. Simultaneously, a second team will work on the recovery of T. solium-RNA from patient stool samples in order to make our test applicable for medical purposes. We are currently forming the necessary partnerships for this goal: A working group in Nairobi has already committed to providing us with relevant material. However, these experiments will be conducted in a properly equipped laboratory, independent from the previously described experiments.

 

References:

[1] Pardee, K. et al. Rapid, Low-Cost Detection of Zika Virus Using Programmable Biomolecular Components. Cell 165, 1255–1266 (2016).

[2] Green, A. A., Silver, P. A., Collins, J. J. & Yin, P. Toehold Switches: De-Novo-Designed Regulators of Gene Expression. Cell 159, 925–939 (2014).

[3] Gomez, S. et al. Genome analysis of Excretory/Secretory proteins in Taenia solium reveals their Abundance of Antigenic Regions (AAR). Sci. Rep. 5, 9683 (2015).

[4] Mayta, H. et al. Nested PCR for Specific Diagnosis of Taenia solium Taeniasis. J. Clin. Microbiol. 46, 286–289 (2008).