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FcMBL: Broad-Spectrum Pathogen Capture for Infectious Diseases

A broad-spectrum pathogen capture technology that removes pathogens from blood and other body fluids for therapeutic and diagnostic applications

Microbial infection is the cause of life-threatening cases of sepsis, meningitis and multiple other diseases that are major causes of death world-wide. Equally prevalent are pathogenic contaminants in our environment, food, and manufacturing processes. In each case, the presence of dangerous microbes must be confirmed, and when they are found, they need to be removed, identified or targeted with therapeutics.

FcMBL: Broad-Spectrum Pathogen Capture for Infectious Diseases
This electron micrograph shows Staphylococcus aureus bacteria (artificially colored in yellow), whose surface has been bound by FcMBL protein coupled to magnetic beads after the enzyme-based method has exposed the sugar molecules that are recognized by FcMBL. Exposing the FcMBL-bead-covered bacteria to a magnetic field allows their rapid and efficient isolation for subsequent analysis. Credit: Wyss Institute at Harvard University.

The Wyss Institute’s pathogen capture platform is based on a genetically engineered version of the natural human blood protein, Mannose Binding Lectin (MBL), which is part of our body’s innate immune system. Native MBL is an ‘opsonin’ that binds to numerous pathogens from all microbial classes (Gram +/- bacteria, fungi, viruses and parasites) as well as many toxins. Wyss researchers created a genetically engineered form of MBL by deleting potentially complicating complement activation and coagulation-promoting domains, and fusing it to an antibody Fc fragment (FcMBL), which stabilizes the molecule and enables rapid purification.

FcMBL retains the ability of native MBL to bind to the same broad spectrum of pathogens, can be easily coupled to surfaces for pathogen capture or to biologically active therapeutic molecules or diagnostic markers. Importantly, FcMBL not only captures live and intact pathogens, but also toxic fragments and toxins released by dead pathogens, known as Pathogen Associated Molecular Patterns (PAMPs), which trigger the inflammatory cascade that leads to organ injury and sepsis. Manufacturing of FcMBL also can be scaled in a cost effective manner, much like the production of a monoclonal antibody, and this has been accomplished under GMP conditions;  the FcMBL protein also has been shown to be well tolerated in toxicology studies.

FcMBL: Broad-Spectrum Pathogen Capture for Infectious Diseases
In the pathogen detection technology, engineered FcMBL proteins coupled to magnetic beads (grey) specifically bind to carbohydrate molecules on the surface of life pathogens, like infectious E.coli bacteria (colored in blue) in this electron micrograph, or on fragments of dead pathogens circulating in the blood-stream. After isolation in a magnetic field, the total pathogenic material is quantified with a second FcMBL protein that is linked to a color-producing enzyme. Credit: Wyss Institute at Harvard University.


The Wyss Institute’s first major application based on this strategy is a broad-spectrum, pathogen-extracting therapy in the form of an extracorporeal device that mimics the blood cleansing function of the human spleen by removing pathogens and pathogen-released toxins from the blood of patients with bloodstream infections or sepsis.  Additional applications could include the capture circulating tumor cells for cancer diagnostics; FcMBL linked to an imaging reagent as a clinical diagnostic to localize infections in the body; injectable therapeutics for patients with opsonin deficiencies; and injectable therapeutics coupling FcMBL with anti-infectious agents, thereby targeting a payload directly to pathogens regardless of the site of infection. In addition, Wyss researchers are also leveraging FcMBL as a quality control and safety assessment tool for pharmaceutical and food products, and a cleansing strategy for agricultural and research products.

This technology has been licensed.

This video explains how sepsis induced by an overload of blood pathogens can be treated with the Wyss Institute’s improved pathogen-extracting, spleen-mimicking device. Blood is flown through a cartridge filled with hollow fibers that are coated with a genetically engineered blood protein inspired by a naturally-occurring human molecule called Mannose Binding Lectin (MBL). MBL is found in our innate immune system and binds to toxic invaders, marking them for capture by immune cells in the spleen. Credit: Wyss Institute at Harvard University.

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