Rhodococcus equi bacteria can cause a lethal form of equine pneumonia in foals. Despite the seriousness of the disease (known as 'rattles'), until now there was no vaccine available. Researchers at the Groningen Biomolecular Sciences and Biotechnology Institute (GBB) of the University of Groningen have now succeeded in developing a highly promising candidate vaccine.
They recently published their research in PLoS Pathogens.
Rhodococcus equi is one of the most important causes of illness in foals between one and six months old, particularly if they don't have much resistance. Pneumonia is the most common manifestation, and because it is accompanied by a rattling in the breathing, this disease is also called rattles.
If the infection is diagnosed too late, the illness can no longer be treated properly with antibiotics and will lead within a few weeks to death. R. equi is commonly found in dry and dusty soil and in manure. In stables, it can sometimes be difficult to prevent dissemination. In environments with lots of foals and a significant chance of infection, a foal vaccine would be a life-saver. Incidentally, R. equi is also dangerous for people and animals with a very weak immune system.
With the aim of developing a vaccine, Robert van der Geize, a member of Lubbert Dijkhuizen's group at the Groningen Biomolecular Sciences and Biotechnology Institute (GBB) of the University of Groningen, and his colleagues looked for 'handles' in the pathogenic bacteria. They found them in some of the genes responsible for the breakdown of steroids. If these genes are defective, then that specific breakdown process cannot take place and the pathogen loses its teeth, in a manner of speaking.
The Groningen researchers eventually succeeded in creating a mutant version of R. equi with the required gene mutations. This mutant did indeed display compromised virulence; in other words, it was not capable of damaging its host. Further research revealed that if a vaccine of this mutated R. equi is given orally to foals when they are 2-5 weeks old, they turn out to be protected against infection by the rattles pathogen.
In this way Van der Geize and his co-authors demonstrated that the breakdown process of steroids by R. equi is crucially important in causing rattles and thus a suitable 'handle' for the further development of a vaccine against the disease.
- R. van der Geize, A. W. F. Grommen, G. I. Hessels, A. A. C. Jacobs, L. Dijkhuizen. The Steroid Catabolic Pathway of the Intracellular Pathogen Rhodococcus equi Is Important for Pathogenesis and a Target for Vaccine Development. PLoS Pathogens, 2011; 7 (8): e1002181 DOI: 10.1371/journal.ppat.1002181
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