Team:Stockholm

ABBBA: Affibody-Based Bacterial Biomarker Assay

Early diagnosis is important for patient prognosis. As a rule of thumb, the earlier a disease is diagnosed, the better the odds for recovery. Studies show that treatment for many different diseases (e.g. cancer) are more efficient when therapy is started at an early stage. Yet, reliable, sensitive and easily applicable diagnostic tools are still lacking.

iGEM Stockholm 2015, consisting of students from Karolinska Institutet and the Royal Institute of Technology, KTH, is developing a novel technique to measure even small amounts of disease biomarker in body fluids. It's an "Affibody-Based Bacterial Biomarker Assay", and we call it ABBBA.

As proof-of-principle, we wanted to sensitize E. coli against the cancer biomarker HER-2 by creating a chimeric receptor. We used the Affibody molecule – a strong molecular binder – and the osmoregulator EnvZ originating from E. coli. Exploiting the EnvZ-OmpR signaling cascade, we wanted to transduce a signal from binding into the cell. In our circuit, this event regulates a differential expression of two quorum sensing molecules depending on the presence of the biomarker. A co-cultured strain will then detect these quorum sensing molecules and express fluorescence.

In the time frame of the project, we synthesized three biobricks of a chimeric antigen receptor. We have not yet show the expression of the receptor in E. coli TOP10 cells. We designed and characterized an OmpR-P dependent circuit to express GFP, which we later exchanged with a quorum sensing synthetase. Furthermore, we showed that our strain expresses RFP as a response to quorum sensing.

We have also cooperated on science and social issues with teams from Switzerland, Israel, Germany, France, Helsinki, Taiwan and Uppsala.