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Learn which problem we are tackling with cELPro and how our technology works

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Inflammatory bowel disease

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Inflammatory bowel disease

Current treatment

Our solution



Inflammatory bowel disease (IBD) is a chronic inflammatory disease of the gastrointestinal tract, where patients typically experience symptoms such as abdominal pain, bloody stools, weight loss, and fatigue for days[1]. Worldwide, 4.9 million people suffer from IBD[2] and it has been found that the prevalence of the disease is still rising in Western and newly industrialized countries[3]. Current treatments aim at relieving IBD symptoms. However, they are not specific enough, cause many side effects or are very expensive. The global impact of IBD cannot be ignored and there is a clear need for better treatment options. The TU-Eindhoven iGEM team wants to tackle this challenge by developing an affordable, safe and targeted microbe-based therapy that works locally in the bowel. With the use of Elastin-Like Polypeptides (ELPs), the TU-Eindhoven team modify E. coli bacteria in such a way that they become unable to divide by forming an intracellular hydrogel, making it safer for ingestion. At the same time, they will produce the anti-inflammatory cytokine Interleukin 10 (IL-10) to treat IBD symptoms and reduce inflammation in the intestine. The product is called cELPro and will be used as a probiotic pill that patients will take regularly. In short, the TU-Eindhoven iGEM team is creating micrometre-sized drug factories that will relieve most of the problems that IBD patients still experience. The team also plans to use this as a modular platform to extend the application to other diseases in the future.

Figure 1: Crohn’s disease vs ulcerative collitis.

Inflammatory Bowel Disease

Worldwide, 4.9 million people suffer from Inflammatory bowel disease (IBD)[2]. Furthermore, it has been found that the prevalence of the disease is still rising in Western and newly industrialized countries[3], which means that the global impact of the disease is still rising. IBD is a chronic inflammatory disease of the gastrointestinal tract, including Crohn’s disease, ulcerative colitis, and microscopic colitis[2]. However, the prevalence of the latter is relatively low compared to the other diseases[4]. Crohn’s disease can affect any part of the gastrointestinal tract, although it most commonly affects the end of the small intestine and the beginning of the large intestine as can be seen in Figure 1[5]. Alternatively, ulcerative colitis typically affects the rectum and colon[6]. It is a lifelong disease with periods of flares and periods of remission, patients typically suffer from abdominal pain, bloody stools, weight loss, and fatigue[1]. For some patients, IBD can be a mild disease, but for others, it can lead to life-threatening complications. While the exact cause of IBD is yet unknown, studies have shown that pathogenesis of the disease is associated with genetic factors, intestinal microbiota, environmental factors, and immunological abnormalities[7].

Current treatment

Current treatments of IBD aim to relieve acute flare-ups or at maintaining remission (this means that medication aims to avoid the occurence of a flare-up). This is done with a combination of 5-aminosalicylic acid therapy and steroids, or TNF-alpha antibodies. Other types of medications that are sometimes used are immunomodulators and antibiotics[8].

Even the most advanced forms of treatment only have a 50% success rate and lots of side effects [9]. They also affect the immune system. The side effects of current therapies can be blamed on the systemic method of administration of these drugs[10]. It is common for patients to get lung infections as a result of the medications they use, since they cause weakening of the immune system[11]. Furthermore, other common side effects are headaches, abdominal pain, diarrhea, nausea, vomiting, muscle or joint pain, loss of appetite, and more. Working on alternative approaches is therefore necessary to minimize patient discomfort and hospitalization time, and to improve the success rate[7].

The financial burden of IBD on the health care system is also significant. Average costs of treatment in the United States amount to 26 thousand dollars per patient per year. Furthermore, the costs of treatment are highly correlated to the course of the disease. Patients with worsening of their disease sometimes need expensive hospitalization time and surgeries[12]. This means that it is extremely important to have ways to keep patients in remission so that no additional interventions are needed.

Please click on the dropdown menus below to learn more about current treatments on the market.

Figure 2: Facts and figures about current treatments.

5-aminosalicylic acid (5-ASA), its structure is shown in Figure 3, is an anti-inflammatory drug widely used in the treatment of patients with mild-to-moderate ulcerative colitis[13]. 5-ASAs are generally more useful for colitis than for Crohn’s disease, since 5-ASA molecules are applied directly to the inner lining of the large intestine, because they coat the colon. Since colitis typically affects the colon, that is the reason why it is more useful for colitis than Crohn’s. It remains uncertain how effective they are at treating Crohn’s disease[14].

Figure 3: 5-aminisalicyclic acid structure[13].

Anti-tumor necrosis factor (TNF) antibodies have been widely used for treatment of both Crohn’s disease and ulcerative colitis[11]. Anti-TNF-α is a proinflammatory cytokine that plays an essential role in induction and maintenance of inflammation in the intestine[15]. The block of TNF signal by anti-TNF monoclonal antibodies is recognized as the most advanced form of therapy to avoid complications and reduce the need for surgery. Although this form of therapy is currently the most advanced form of treatment, there are also downsides and side effects. The antibodies can also trigger the immune system. This leads to occurrence of immunogenicity, which may result in loss of response and treatment failure[16]. Anti-TNF antibodies do not work at all from the start of treatment for 10-30 percent of patients, and 26-46 percent of patients lose response overtime[9].

Furthermore, our team has learned from talking to physicians that treatment with antibodies is very expensive, costing around 10,000 to 40,000 euros per patient annually. Aside from that, they need to be injected, which makes the treatment very bearable on the patient. More about our conversations with the doctor who we learned this from can be read on our Human Practices Page.

Corticosteroids affect the body’s ability to begin and maintain an inflammatory process, and therefore they keep the immune system in check. Corticosteroids are effective for short-term control of flare-ups. However, they are not recommended for long-term use, since their side effects include infections, bone loss, weight gain, cataracts, skin fragility, sleep loss, and mood swings[11][17].

Corticosteroids work on multiple cells of the immune system, which can be seen in Figure 4[18].

Figure 4: Mechanism of action of corticosteroids. Corticosteroids bind to intracellular receptors that translocate into the nucleus, resulting in altered transcription of various genes. Corticosteroids have diverse physiological effects and regulate multiple different immune cells, either directly or indirectly, as shown in the image. The actions of corticosteroids are mainly accomplished by modulating inflammatory cytokines as well as through induction of apoptosis[18].

Immunomodulators are used to maintain remission in patients who do not respond well to other medications. These type of drugs modify the activity of the immune system, such that it cannot maintain ongoing inflammation. Furthermore, antibiotics might have small benefits for patients with Crohn’s disease, where they might be used when C. difficile infections occur[19]. They do not have any benefits in the treatment of ulcerative colitis[11].

Figure 5: E. coli are genetically engineered to contain two plasmids, the first plasmid containd the genetic material that encodes for the proteins that are needed for the hydrogel formation. The other plasmid encodes a therapeutic protein.

Our solution

Treating IBD is not yet possible without many side effects and a lot of money. To solve these problems, team iGEM TU-Eindhoven genetically engineer E. coli to turn them into a probiotic. This resulted in the development of cELPro. As shown in Figure 5, the bacteria were inserted with two plasmids, one of which produces Elastin-Like Polypeptides (ELPs) that form an intracellular hydrogel, and the other Interleukin 10 (IL-10). ELPs are synthetic biopolymers that have an affinity for each other based on hydrophobic interactions[20]. To increase the affinity even further, they were equipped with complementary Leucine zipper cross-linkers attached at their ends. The hydrogel forms in a temperature-dependent manner based on these interactions[21]. The goal of the hydrogel is to make sure that the bacteria stop dividing, which makes them safer to ingest. They are not able to grow out of control anymore once the gel is formed, but they can still produce the therapeutic IL-10. This makes the release of IL-10 controlled and provides a great alternative to current treatment options.

The bacteria are freeze-dried and put in a pill that the patient takes regularly when they experience a disease flare-up (Figure 6). The pill has a coating that can withstand the acidic environment of the stomach. The bacteria reach the gut alive, containing the hydrogel, where it produces IL-10 to locally treat IBD. IL-10 is an immunoregulatory cytokine that has the potential as an anti-inflammatory biological therapy for IBD. It has been used in research for treatment of IBD with promising results, but since it was often administered systemically, a high concentration was needed, causing many side effects[22]. By administering IL-10 locally with bacteria, these problems are tackled. In earlier research, it has been tried before to use bacterial strains that secrete IL-10 to treat IBD in mice with promising results[23]. Additionally, there has even been a promising study in human subjects who experienced almost no side effects[24]. However, biocontainment remains a challenge and often requires many steps to make sure the bacteria do not grow out of control outside of the patient. Solutions with transgenic bacteria have been tested before, but the route to make these bacteria is very labor-intensive[25]. This problem will be solved by our technology, since it will be easier to develop and more scalable. The sections below will explain the parts of our idea further.

Figure 6: A pill with freeze-dried bacteria is ingested by the patient when they experience a disease flare-up. The pill has a coating so that the acidic stomach can be surpassed. The non-dividing bacteria reach the gut alive and will locally produce IL-10 to treat IBD symptoms.

Figure 7: A sharp increase in absorbance can be measured when the temperature is increased above the Tt of the ELPs. This increase is due to the formation of aggreates due to hydrophobic interactions.

ELPs are protein polymers which are derived from human tropo-elastin. One of their key features is that they exhibit a phase separation behaviour that is often reversible. Samples remain soluble below a certain transition temperature (Tt) but form micelles or aggregates above Tt (Figure 7). For ELPs many applications have already been found in purification, sensing, activation, and nano assembly. Furthermore, they are non-immunogenic, can be substrates for proteolytic biodegradation, and can be decorated with pharmacologically active peptides, proteins, and small molecules{20}. This makes them very interesting for therapeutic applications. Furthermore, recombinant synthesis allows precise control over ELP properties and weight, which results in protein polymers with uniform physicochemical properties that can be used in the design of multifunctional biologics[20].

The general structure of polymeric ELPs is (VPGXG)n, where the monomeric unit is Val-Pro-Gly-X-Gly, and the "X" denotes a variable amino acid guest residue that impacts the properties of the ELP, such as the Tt. Specifically, the hydrophilicity or hydrophobicity and the presence or absence of a charge on the guest residue affects the Tt. Furthermore, the hydrophobicity of the guest residue can affect the Tt. The "n" denotes the number of monomeric units that the polymer is comprised of[21]. In general, ELPs are linear below the Tt, but aggregate into spherical clumps, or coacervates, above the Tt[26].

Figure 8: A schematic representation of the ELPs used to form a hydrogel in E. coli and how they interact. In yellow are the Leucine zippers, the hydrophobic part in red and the hydrophilic part in blue. The ELPs exhibit phase separation behavior that is temperature dependent. Furthermore, the Leucine zippers ensure a higher affinity between the proteins.

Figure 9: A schematic representation of the hydrogel formation above the transition temperature where the hydrophobic and hydrophilic domains of the Elastin-like polypeptides interact with other ELPs to form an hydrogel.

The TU-Eindhoven 2023 team used these proteins for the formation of the hydrogel in E. coli. The repeating sequences used were (VPGIG)n and ((VPGAG)3(VPGGG)2)n which creates a hydrophobic and hydrophilic part in the chain. To make the affinity for the proteins even higher, complementary Leucine zipper domains were also added to the protein. Leucine zippers are amphipathic helices, two complementary zippers are able to dimerize. Figure 8 and 9 show the structure of the designed proteins and their interaction.

Figure 10: Left: IL-10 inhibits the pro-inflammatory cytokine production from immune cells to maintain homeostasis. Right: In absence of IL-10, a severe inflammation occurs when a pathogen is present. This reaction is too severe and lasts too long in the case of IBD.

Interleukin 10 (IL-10)

Interleukin 10 (IL-10) is an anti-inflammatory cytokine made by most cells of the immune system. It acts via limiting immune responses during infection, allergic reactions, and autoimmunity. IL-10 plays a central role in the prevention of immune-mediated damage to the host. A schematic representation of the function of IL-10 can be seen in Figure 10. However, because of its immunosuppressive effects, too much IL-10 can cause chronic infections[27]. This is part of the reason that systemic use of IL-10 has not been successful yet in the treatment of IBD. Other reasons include that the concentration in the bowel does not become high enough to see therapeutic effects when systemic administration is used. Furthermore, there might be differences among individuals depending upon disease phenotype/severity. It is also possible that IL-10 is only successful at preventing and not treating the disease. More reasons that IL-10 does not work well when used systemically are that IL-10 alone fails to suppress all the pro-inflammatory mediators involved in chronic inflammation or it might be possible that IL-10’s immunostimulatory effects counterbalance its immunosuppressive properties[25].

Even though IL-10 has not been proven to be successful in the use of systemic treatments, it is an interesting protein to use in different, more local applications like the solution from the TU-Eindhoven team described above. There have been successes with the use of IL-10 in the treatment of IBD with bacteria before, such as a clinical trial and study in mice using transgenic bacteria that produce IL-10, locally in the bowel[24][23]. The patients who participated in this study experienced almost no side effects, but they did see a decline in symptoms of their disease. This is why the TU-Eindhoven team focusses on this protein as a therapeutic.


By forming the hydrogel, the bacteria become unable to divide. This concept has been tested with an intracelluar PEG polymer-based hydrogel before[28]. Upon deviding the bacteria were not able to divide anymore. The TU-Eindhoven 2023 team wants to use this approach but with synthetic biology to make a protein-based hydrogel. An advantage of this approach is that all the machinery to make the hydrogel is present in the bacteria, which makes the approach more scalable and affordable. The system requires the addition of the plasmid to the bacteria that encodes for the proteins that form the hydrogel and another one that encodes for the therapeutic protein before they are grown in large quantities. When the hydrogel needs to be formed, all that is needed is to increase the temperature to above the transition temperature of 21 degrees Celcius. The method with the PEG polymer-based gel requires the bacteria to be cultured first before equipping them with the parts that form the hydrogel, which results in more production steps. Furthermore, the production of bacteria is generally easier than the production of complicated antibodies, which makes this solution more scalable compared to current treatment options as well.

Figure 11: Advantages of cELPro

Another aspect that makes cELPro more affordable is the fact that it can be administered as a pill. This means that the patient will not have to visit the hospital for injections from trained physicians as often which reduces healthcare costs.

The fact that the bacteria stop dividing makes them safer to consume compared to bacteria that would be dividing, since our bacteria cannot grow out of control or easily mutate. This means that they do not change the microbiome of the patient.

Eventually, the system can be used to create a modular platform to cure a variety of intestinal diseases in a non-invasive way. In conclusion, the treatment is a local, non-invasive, scalable, and affordable alternative to current options for IBD treatment.

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[1] Charmot, D. (2012). Non-Systemic Drugs: A Critical Review. Current Pharmaceutical Design, 18, 1434–1445.

[2] Crohn’s Disease Severity and Progression. (n.d.). Retrieved September 26, 2023, from https://www.crohnsandcolitis.com/crohns/severity-and-progression

[3] Guan, Q. (2019). A Comprehensive Review and Update on the Pathogenesis of Inflammatory Bowel Disease. Journal of Immunology Research, 2019. https://doi.org/10.1155/2019/7247238

[4] Hadji, H., & Bouchemal, K. (2022). Advances in the treatment of inflammatory bowel disease: Focus on polysaccharide nanoparticulate drug delivery systems. Advanced Drug Delivery Reviews, 181, 114101. https://doi.org/10.1016/j.addr.2021.114101

[5] Rao, B. B., Click, B. H., Koutroubakis, I. E., Ramos Rivers, C., Regueiro, M., Swoger, J., Schwartz, M., Hashash, J., Barrie, A., Dunn, M. A., & Binion, D. G. (2017). The Cost of Crohn’s Disease: Varied Health Care Expenditure Patterns Across Distinct Disease Trajectories. Inflammatory Bowel Diseases, 23(1), 107–115. https://doi.org/10.1097/MIB.0000000000000977

[6] Roda, G., Jharap, B., Neeraj, N., & Colombel, J. F. (2016). Loss of Response to Anti-TNFs: Definition, Epidemiology, and Management. Clinical and Translational Gastroenterology, 7(1), e135. https://doi.org/10.1038/CTG.2015.63

[7] Wang, R., Li, Z., Liu, S., & Zhang, D. (2023). Global, regional and national burden of inflammatory bowel disease in 204 countries and territories from 1990 to 2019: a systematic analysis based on the Global Burden of Disease Study 2019. BMJ Open, 13(3), e065186. https://doi.org/10.1136/BMJOPEN-2022-065186

[8] What is inflammatory bowel disease (IBD)? | IBD. (n.d.). Retrieved June 14, 2023, from https://www.cdc.gov/ibd/what-is-IBD.htm