Scientists have created a unique “living medicine”

This shows a cross section of a mouse lung infected with Pseudonomas aeruginosa. The mouse was treated with a version of Mycoplasma pneumoniae that could not produce therapeutic molecules, leading to severe pneumonia. This is characterized by massive infiltration of inflammatory cells into the alveolar septa, resulting in air loss in the alveoli. Credit: Rocco Mazzolini/CRG

Synthetic biology presents new approaches to combat the leading cause of death in hospitals.

Scientists have created the first “living medicine” to treat lung infections. This innovative treatment targets Pseudomonas aeruginosa, a bacterium known to be resistant to many antibiotics and often causing infections in hospitals.

This treatment involves the use of a modified form of the bacterium Mycoplasma pneumoniae that has had its disease-causing abilities removed and reprogrammed to target P. aeruginosa. The modified bacterium is used in combination with low doses of antibiotics, which are ineffective on their own.

The researchers tested the effectiveness of the treatment in mice and found that it significantly reduced lung infections. The “living drug” doubled the survival rate of mice compared to no treatment. The introduction of a single high dose of the drug did not reveal signs of toxicity in the lungs. After the treatment ended, the innate immune system got rid of the modified bacteria within four days.

The results are published in the journal Nature Biotechnology and were funded by the “la Caixa” foundation through the CaixaResearch Health Appeal. The study was led by researchers from the Center for Genomic Regulation (CRG) and Pulmobiotics, in collaboration with the August Pi y Sunyer Institute for Biomedical Research (IDIBAPS), the Hospital Clinic of Barcelona and the Institute of Agrobiotechnology (IdAB). Spanish institute CSIC and the government of Navarre.

This shows a cross section of a mouse lung infected with Pseudonomas aeruginosa. The mouse was treated with a version of Mycoplasma pneumoniae that is capable of producing therapeutic molecules such as pyocins specifically designed to fight P. aeruginosa. This therapeutic version of M. pneumoniae acts like a “living medicine”, reducing the effects of infection and keeping air in the alveoli. Credit: Rocco Mazzolini/CRG

P. aeruginosa infections are difficult to treat because the bacteria live in biofilm-forming communities. Biofilms can attach to various body surfaces, forming impenetrable structures that are inaccessible to antibiotics.

P. aeruginosa biofilms can grow on the surface of endotracheal tubes used by critically ill patients who require a ventilator to breathe. This causes ventilator-associated pneumonia (VAP), a condition that affects one in four (9-27%) patients requiring intubation. The incidence exceeds 50% for patients intubated due to severe Covid-19. VAP can extend ICU stay to thirteen days and kill up to one in eight patients (9-13%).

The authors of the study developed M. pneumoniae to dissolve biofilms, endowing it with the ability to produce various molecules, including pyocins, toxins naturally produced by bacteria to kill or inhibit the growth of Pseudomonas bacterial strains. To test its effectiveness, they collected P. aeruginosa biofilms from the endotracheal tubes of patients in intensive care units. They found that the treatment penetrated the barrier and successfully dissolved the biofilms.

“We have developed a ram that precipitates antibiotic-resistant bacteria. The treatment punches holes in their cell walls, providing important entry points for antibiotics to enter and kill infections at their source. We believe this is a promising new strategy to address the leading cause of death in hospitals,” says Dr. Maria Luh, Chief Scientist at Pulmobiotics, study co-author and principal investigator at the International University of Catalonia.

With a view to using a “living drug” for the treatment of VAP, researchers will conduct additional trials before moving on to the clinical trial phase. Treatment is expected to be carried out using a nebulizer, a device that turns liquid medicine into a mist, which is then inhaled through a mouthpiece or mask.

M. pneumoniae is one of the smallest known bacterial species. Dr. Luis Serrano, director of the CRG, first came up with the idea of ​​modifying bacteria and using them as a “living medicine” two decades ago. Dr. Serrano is an expert in synthetic biology, a field that involves repurposing organisms and creating useful new abilities in them. With only 684 genes and no cell wall, the relative simplicity of M. pneumoniae makes it ideal for engineering biology for specific applications.

One of the benefits of using M. pneumoniae to treat respiratory diseases is that it naturally adapts to lung tissue. After the introduction of the modified bacterium, it goes directly to the source of the respiratory infection, where it sets up like a temporary factory and produces various therapeutic molecules.

By showing that M. pneumoniae can fight infections in the lungs, the study opens up the possibility for researchers to create new strains of bacteria to fight other types of respiratory diseases, such as lung cancer or asthma. “A bacterium can be modified with various payloads, whether it be cytokines, nanobodies or defensins. The goal is to diversify the arsenal of modified bacteria and unlock their full potential in the treatment of various complex diseases,” says ICREA research professor Dr. Luis Serrano.

In addition to developing a “living drug”, Dr. Serrano’s research team is also using its expertise in synthetic biology to develop new proteins that can be delivered by M. pneumoniae. The team uses these proteins to fight inflammation caused by P. aeruginosa infections.

Although inflammation is the body’s natural response to infection, excessive or prolonged inflammation can damage lung tissue. The inflammatory response is driven by the immune system, which releases mediator proteins such as cytokines. One type of cytokine, IL-10, has well-known anti-inflammatory properties and is of growing therapeutic interest.

The study, published in the journal Molecular Systems Biology by Dr. Serrano’s research team, used ModelX and FoldX protein design software to create new versions of IL-10 specifically optimized to treat inflammation. Cytokines have been designed to be created more efficiently and have a higher affinity, meaning that fewer cytokines are needed to achieve the same effect.

The researchers created strains of M. pneumoniae that express the new cytokines and tested their efficacy in the lungs of mice with acute P. aeruginosa infection. They found that the engineered versions of IL-10 were significantly more effective at reducing inflammation than the wild-type cytokine IL-10.

According to Dr. Ariadne Montero Blay, co-author of the study in Molecular Systems Biology, “Live biotherapeutics such as M. pneumoniae are ideal tools to help overcome the traditional limitations of cytokines and unlock their great potential in the treatment of various human diseases.” illness. The creation of cytokines as therapeutic molecules has been critical in combating inflammation. This approach may also benefit other lung diseases such as asthma or pulmonary fibrosis.”

Reference: “Engineered live bacteria suppress Pseudomonas aeruginosa infection in mouse lungs and dissolve endotracheal tube biofilms” Rocco Mazzolini, Irene Rodriguez-Arce, Laia Fernandez-Barat, Carlos Piñero-Lambea, Victoria Garrido, Agustín Rebollada-Merino, Anna Motos, Antoni Torres , Maria Jesus Grillo, Luis Serrano and Maria Luh-Senar, 19 January 2023, Nature Biotechnology.
DOI: 10.1038/s41587-022-01584-9