Scientists at the NIAID Rocky Mountain Laboratories (RML) in Hamilton, Montana, are examining how abnormal prion protein molecules cause transmissible spongiform encephalopathy (TSE) diseases. RML has had an active TSE research program since the 1960s. RML is one of the world's premiere laboratories for studying TSE diseases. Scientists there co-discovered and were among the first to clone the prion protein gene. NIAID scientists also discovered that abnormal prion protein can convert normal prion protein to the abnormal form. This may account for the disease process in the brain.
RML scientists have published findings from significant TSE studies. One study showed that when prion protein was modified to remove a membrane "anchor" in laboratory animals, scrapie infection caused formation of abnormal prion protein, but remarkably, did not result in disease. Researchers believe that without the membrane anchor, the abnormal prion protein is unable to damage the brain cells. These results suggest that drugs aimed at blocking interactions between normal and abnormal prion protein might be able to halt the progress of disease. In these same mice where the membrane anchor was removed, scrapie infection led to an accumulation of abnormal prion protein in heart tissue resulting in heart stiffness and malfunction. This research indicates that cardiac infection may be a new and previously overlooked feature of TSE diseases.
In another study, RML scientists used a new methodology to determine the size of the smallest infectious prions. These results demonstrate that the minimal size of the infectious material is equivalent to 5 to 10 prion protein molecules. It is possible, though not yet proven, that these smallest fractions are more infectious than the larger aggregates.
At Colorado State University in Fort Collins, NIAID has established an emerging diseases research center focused on studying chronic wasting disease (CWD). This center is investigating the mechanics of CWD infection in deer and elk. Such studies underlie the search for improved diagnostics and therapies. The researchers also will seek to better understand the entire spectrum of disease transmission and under what circumstances CWD might "jump" to other species.
One study concluded that infectious prions are present in skeletal muscles of CWD-infected deer, demonstrating that humans eating or handling meat from CWD-infected deer are at risk for prion exposure. Though there is no causal proof that CWD is capable of spreading to humans, researchers suggest that people use caution when handling infectious material or consuming any part of the animal that may be infected. More recently, the research group at Colorado State University has reported that infectious prions capable of transmitting CWD are found in the saliva and blood of affected deer. This helps to explain the ease of transmission of CWD among deer and suggests caution concerning contact with body fluids of infected animals.