03 Feb 2014

Researchers find novel approach for controlling deadly C. difficile hospital infections

Llama-derived antibodies open door to development of new treatment

CALGARY – Using data collected at the Canadian Light Source, researchers have revealed the first molecular views showing how antibodies derived from llamas may provide a new method for controlling the highly infectious disease C. difficile, common in health-care facilities.

One of the most problematic hospital-acquired infections worldwide, C. difficile (Clostridium difficile) is an opportunistic bacterial pathogen that causes extreme diarrhea and potentially fatal colon inflammation. This new research provides exciting opportunities for creating a new generation of engineered antibodies that will be more effective at preventing the toxins from damaging the intestine during the normal course of the disease.

Researchers from the Alberta Glycomics Centre at the University of Calgary and the University of Alberta, in collaboration with researchers at the National Research Council of Canada in Ottawa, have shown for the first time how antibodies recognize the disease’s two central toxin proteins: toxin A (TcdA) and toxin B (TcdB). The research was published in the Journal of Biological Chemistry,

“Our research is an important step towards developing highly specific ways to treat this very common and serious disease,” says Kenneth Ng, associate professor in the Department of Biological Sciences at the University of Calgary and the study’s senior author.

Disease takes sweeping toll in health care

A Canadian hospital study found that of 136,877 hospital admissions, 1 in 100 patients will contract C. difficile infection, and of those, 1 in 10 will die regardless of the initial reasons for admission. The disease is most frequently seen in older adults who take antibiotics and get medical care. Annual health-care costs are estimated to be several billion dollars worldwide.

The key findings in the paper derive from the three-dimensional structures of antibody-toxin complexes that were determined using X-ray crystallography by Tomohiko Murase, Luiz Eugenio and Melissa Schorr in Ng’s laboratory. The antibody-toxin complexes were developed using single-domain antibodies derived from llamas.

“The smaller size of the llama antibodies compared to the monoclonal antibodies currently used for diagnostics or in development for therapeutics greatly assists with structure determination and protein engineering,” explains Ng. “Starting from these structures, we are now creating modified antibodies for improving treatments in the future.”

Simpler antibody structure allows modifications

“Basic biological research on llamas, camels and sharks led to the discovery of a smaller type of antibody with a simpler structure,” adds Ng. “It is this simpler structure that allows us to make modifications and perform many detailed studies that are not easily done with other types of antibodies. The unique characteristics of these single-domain antibodies provide an attractive approach for developing new treatments for C. difficile.”

According to Ng, although the research is at the fundamental science level, the new structures provide a blueprint for designing new molecules that could neutralize the bacterial toxins more effectively than anything currently available.

This project relied on important contributions from Elena Kitova in John Klassen's mass spectrometry group at the Alberta Glycomics Centre, at the University of Alberta, as well as from Greg Hussack in Jamshid Tanha’s antibody therapeutics group at the National Research Council in Ottawa.

The research was primarily supported by the Alberta Glycomics Centre, which is funded by Alberta Innovates Technology Futures, as well as the Natural Sciences and Engineering Research Council of Canada, and the National Research Council of Canada.  Crystallographic work was performed at the CLS synchrotron in Saskatoon and the Stanford Synchrotron Radiation Light Source in California.

University of Calgary Associate Professor of Biochemistry, Kenneth Kai-Sing Ng (right) and Research Associate Tomohiko Murase have made advances for the detection and treatment of Clostridium difficile using data collected at the Canadian Light Source synchrotron.
Photo by Riley Brandt, University of Calgary
This and other photos available through a Creative Commons licence in theCLS Flickr gallery
Reference: Murase, Tomohiko, et al. "Structural Basis for Antibody Recognition in the Receptor-binding Domains of Toxins A and B from Clostridium difficile." Journal of Biological Chemistry 289.4 (2014): 2331-2343. 
DOI: 10.1074/jbc.M113.505917

http://www.jbc.org/content/289/4/2331.short

About the CLS:

The Canadian Light Source is Canada’s national centre for synchrotron research and a global centre of excellence in synchrotron science and its applications. Located on the University of Saskatchewan campus in Saskatoon, the CLS has hosted 1,700 researchers from academic institutions, government, and industry from 10 provinces and territories; delivered over 26,000 experimental shifts; received over 6,600 user visits; and provided a scientific service critical in over 1,000 scientific publications, since beginning operations in 2005.

CLS operations are funded by Canada Foundation for Innovation, Natural Sciences and Engineering Research Council, Western Economic Diversification Canada, National Research Council of Canada, Canadian Institutes of Health Research, the Government of Saskatchewan and the University of Saskatchewan.

Synchrotrons work by accelerating electrons in a tube to nearly the speed of light using powerful magnets and radio frequency waves. By manipulating the electrons, scientists can select different forms of very bright light using a spectrum of X-ray, infrared, and ultraviolet light to conduct experiments.

Synchrotrons are used to probe the structure of matter and analyze a host of physical, chemical, geological and biological processes. Information obtained by scientists can be used to help design new drugs, examine the structure of surfaces in order to develop more effective motor oils, build more powerful computer chips, develop new materials for safer medical implants, and help clean up mining wastes, to name a few applications.

For more information visit the CLS website 
For photos to accompany this story and more images from the CLS visit our Flickr gallery

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