Team:Stockholm/Project Description

Project description

Mucus is a protective barrier

With every breath, we inhale oxygen along with potentially harmful pathogens and particles, such as allergens and pollutants. As a first line of defense, the respiratory tract epithelium is covered with a protective layer called mucus. Mucus is a thin and viscous gel which traps the foreign molecules and consequently prevents them from entering the body. Underneath the mucus, tiny hair-like structures called cilia are constantly transporting the mucus up and out of the lung, eliminating the captured particles. This process is well-known as mucociliary clearance (Munkholm et al., 2013). Thus, mucus functions as a protective barrier against harmful stimuli from the environment, continuously keeping the airways clear of foreign particles.

The problem

Thick mucus

Several chronic respiratory diseases are associated with excessively thickened mucus which immobilizes the cilia movement, resulting in impaired mucociliary clearance. Therefore, mucus hyperconcentration could lead to airway obstruction and plugging. Shortness of breath, coughing, wheezing, higher risk of infections and overall reduced lung function are only some of the problems which patients face. (Zhou-Suckow et al., 2017) (Munkholm et al., 2013). These struggles affect their daily life, decreasing their life quality and lifetime expectancy.

Diseases associated with thick mucus

Asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis are examples of chronic respiratory diseases associated with thick mucus. Patients suffering from these diseases require lifelong treatments and some might even have to undergo lung transplantation. Together, the three diseases affect more than 300 million people around the world with a total cost of at least 100 billion USD only in the US. For these patients, it is crucial to relieve the mucus-associated symptoms and that is what iGEM Stockholm 2017 intends to do.

Limitations of current treatments

We expanded our project into the society and met with the people behind the diseases, our driving force throughout the project. We were able to identify a need for PROlung when we sat down with patients, doctors, nurses, physiotherapists and family members to ask them, what do they really need? By doing this, we identified the gap in medications and the need for a mucus-targeting therapy. The current treatments are few, expensive and often require repeated administration by trained personnel. Therefore, there is a demand for a better solution, a need for PROlung.

Our solution

PROlung - a mucus degrading lung probiotic

iGEM Stockholm 2017 aims to fill this gap with a self-regulated system residing in the lungs, capable of releasing enzymes to promote respiratory health by degrading excessively thick mucus.

We believe that the unexplored concept of a live self-regulating biotherapeutic product holds great promise. It has only recently been demonstrated that the lungs are inhabited by diverse types of bacteria (Beck et al., 2012). We aim to harness the potential of the lung microbiome by engineering a lung probiotic to degrade excessively thickened mucus. We call it PROlung - a novel therapeutic approach to address the patient’s unmet needs.

Our lung probiotic would safely reside in the lungs, sense the change in density of the excessively thickened mucus, and subsequently release mucus-degrading enzymes. The objective is to reduce the viscosity of mucus by removing glycans, aiming to restore the mucociliary clearance. Once the mucus has been restored, the release of enzymes will be inhibited. This mechanism ensures that our probiotic can be self-regulated. At the same time, the spread of bacteria is controlled by an integrated biocontainment system, ensuring that PROlung remains in the lungs without affecting the host’s lung microbiome.

Our project is divided into three parts:

1. Biocontainment

The employment of living, genetically engineered bacteria in diseased lungs as a novel approach poses several concerns, such as the unintended proliferation of GMOs into the environment, as well as adversities on human health; thus, it is imperative to suggest a strategy to prevent or minimize these risks (Mandell et al., 2015). In particular, our aim is to design a system of two different gene-switches (cumate and tryptophan switch) regulating a toxin-antitoxin system (Colicin E2 and Immunity protein 2), while using the mini-Tn7 BioBrick toolkit to integrate them into the bacterial genome. Moreover, pH and temperature sensitive sensors can be further employed to regulate the GMO’s dissemination. To read more, click here.

2. Sensing

The thickened mucus characterizing the targeted diseases contains more mucin molecules, causing a five-fold increase of osmotic pressure in the patient’s lungs (Henderson et al, 2014). To sense this alteration in osmotic pressure and hence sense “sick” mucus, we will employ the OmpR/EnvZ two-component system, already native to the bacteria. The system triggers promoter activation upon increasing osmotic pressure (Pratt et al., 1996). Our aim is to further characterize the BioBricks for this system and demonstrate that an increase in osmotic pressure will trigger the expression of our mucus-degrading enzymes. To read more, click here.

3. Degradation

Sialidase and endo-β-galactosidase activity has been proved to alter the composition of mucus (Derrien et al., 2010). With this premise in mind we hypothesized that these changes may also affect some physical properties of mucus such as viscosity. The degradation may lead to a less viscous (more fluid) mucus and subsequently an improved mucociliary clearance (Zhou-Suckow et al., 2017). Our aim is to successfully clone and express sialidase and endo-β-galactosidase genes in our bacterial system. Simultaneously, we strive to secrete the enzymes and lastly, confirm their desired effect on mucus. To read more, click here.


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