Fighting hospital germs with sugar

Around 40 percent of patients in hospitals and nursing homes carry the gut bacterium C. difficile. Such patients are easy prey for the pathogen. Because the patients’ intestinal flora is often damaged by antibiotic treatments, the bacteria are able to spread unhindered. Moreover, treatment of the infection becomes increasingly difficult, as the bacteria tend to develop resistance to antibiotics.

Researchers at the Max Planck Institute of Colloids and Interfaces have now constructed a molecule that could protect patients against C. difficile. It resembles the characteristic sugar coating on the surface of bacteria and, as such, is able to elicit a similar immune response as the bacterium itself. The molecule could thus be used as a vaccine, because once the immune system has produced antibodies against a pathogen, it is prepared to fend off the invaders in the event of a later infection.
 

 
Synthetic molecule as a cost-effective alternative for immunization

The researchers first investigated which parts of the sugar coating are actually necessary to trigger an immune response. They then constructed an artificial molecule with those properties by attaching the essential sugar structures to an amino acid backbone. Coupled with an immunostimulating peptide, the molecule stimulated the immune system in mice to produce antibodies that were effective against the similarly constructed surface sugars of C. difficile. The mice are therefore protected against a subsequent infection with the bacterium. Moreover, it may be possible to use the molecule to produce therapeutic antibodies that can be administered to sick patients to boost their immune system and combat infections.

Many bacteria bear characteristic carbohydrates on their surface, and it is known that these surface sugars are suitable for immunization purposes. However, the surface sugars usually have to be detached from specially bred microbes — an expensive and complicated process. By synthesizing artificial molecules for immunization, the researchers have now come up with a cost-effective alternative. “Our findings are a very good example of how basic research into the human immune response to sugars can lead to new candidates in the fight against dangerous hospital germs,” says Peter H. Seeberger, Director at the Max Planck Institute of Colloids and Interfaces and Professor at Freie Universität Berlin. As early as 2011, he and his team synthesized a molecule for immunizing against C. difficile; at the time, however, they used a different surface sugar molecule as a template.

In order to progress from research results to actual use in patients, the scientists at the Max Planck Institute of Colloids and Interfaces in Potsdam are working with Vaxxilon AG (Reinach, Switzerland) to develop novel carbohydrate-based vaccines. Vaxxilon has licensed a portfolio of vaccine candidates against a number of pathogens, including C. difficile.