Scrapie could breach the species barrier

The pathogens responsible for scrapie in small ruminants (prions) have the potential to convert the human prion protein from a healthy state to a pathological state, researchers have discovered for the first time. In mice models reproducing the human species barrier, this prion induces a disease similar to Creutzfeldt-Jakob disease. These primary results stress the necessity to reassess the transmission of this disease to humans.

INRA scientists have shown for the first time that the pathogens responsible for scrapie in small ruminants (prions) have the potential to convert the human prion protein from a healthy state to a pathological state. In mice models reproducing the human species barrier, this prion induces a disease similar to Creutzfeldt-Jakob disease. These primary results published in Nature Communications on 16 December 2014, stress the necessity to reassess the transmission of this disease to humans. Scrapie is a neurodegenerative disease that has been known for centuries and which affects sheep and goats. Similar to Bovine Spongiform Encephalopathy (BSE) or mad cow disease, scrapie is caused by a transmissible pathogen protein called prion.

However, and contrary to BSE, epidemiological studies have never been able to establish a link between this disease and the occurrence of prion diseases in humans. "Risks of transmitting scrapie to humans (zoonose) were hitherto considered negligible because of the species barrier that naturally prevents prion propagation between species.

Scrapie is a neurodegenerative disease that has been known for centuries and which affects sheep and goats

Researchers at INRA studied the permeability of the human transmission barrier to pathogens responsible for scrapie, using animal models specifically developed for this purpose. This approach previously allowed the confirmation of the zoonotic nature of prions responsible for BSE in cows and of the variant of Creutzfeldt-Jakob disease in humans (vCJD).

Unexpectedly, in these rodent models, certain pathogens responsible for scrapie were able to cross the transmission barrier. Moreover, the pathogens that propagated through this barrier were undistinguishable from the prions causing the sporadic form of Creutzfeldt-Jakob disease (sCJD). This data suggest a potential link between the occurrence of certain sCJD and these animal prions.

"Since CJD is scarce, about 1 case per million and per year, and incubation periods are usually long -several decades- it is extremely difficult for epidemiological studies to try and make this link. In their conclusions, the authors stress the fact that CJD cases are rare though scrapie has been circulating for centuries in small ruminants for which we eat the meat. Even if in future studies scrapie is finally confirmed to have a zoonotic potential, the authors consider that this disease does not constitute a new major risk for public health.

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Biotechnology Department

Personalized ovarian cancer vaccines developed Using Computational Biology Approach

Researchers at the University of Connecticut have found a new way to identify protein mutations in cancer cells. The novel method is being used to develop personalized vaccines to treat patients with ovarian cancer.

"This has the potential to dramatically change how we treat cancer," says Dr. Pramod Srivastava, director of the Carole and Ray Neag Comprehensive Cancer Center at UConn Health and one of the principal investigators on the study. "This research will serve as the basis for the first ever genomics-driven personalized medicine clinical trial in immunotherapy of ovarian cancer, and will begin at UConn Health this fall," Srivastava says.

The researchers focused their clinical trial on patients with ovarian cancer because the disease usually responds well to surgery and chemotherapy in the short term, but often returns lethally within a year or two. That gives researchers the perfect window to prepare and administer the new therapeutic vaccines, and also means they may be able to tell within two years or so whether the vaccine made a difference. If the personalized vaccines prove to be safe and feasible, they'll design a Phase II trial to test its clinical effectiveness by determining whether they prolong patients' lives.

Identifying tiny differences

In order for the immune system to attack cancers, it first has to recognize them. Every cell in the body has a sequence of proteins on its exterior that acts like an ID card or secret handshake, confirming that it's one of the good guys. These protein sequences, called epitopes, are what the immune system 'sees' when it looks at a cell. Cancerous cells have epitopes, too. Since cancer cells originate from the body itself, their epitopes are very similar to those of healthy cells, and the immune system doesn't recognize them as bad actors that must be destroyed. But just as even the best spy occasionally slips up on the details, cancer cell epitopes have tiny differences or mistakes that could give them away, if only the immune system knew what to look for.

"We want to break the immune system's ignorance," Srivastava says. For example, there could be 1,000 subtle changes in the cancer cell epitopes, but only 10 are "real," meaning significant to the immune system. To find the real, important differences, Mandoiu, the bioinformatics engineer, took DNA sequences from skin tumors in mice and compared them with DNA from the mice's healthy tissue.

Previous researchers had done this but looked at how strongly the immune system cells bound to the cancer's epitopes. This works when making vaccines against viruses, but not for cancers. Instead, Srivastava's team came up with a novel measure: they looked at how different the cancer epitopes were from the mice's normal epitopes. And it worked. When mice were inoculated with vaccines made of the cancer epitopes differing the most from normal tissue, they were very resistant to skin cancer.

Theoretically, this approach could work for other cancers, although the research has yet to be done.

Creating a safe, effective cancer vaccine is one of the major long-term goals of personalized medicine. Using a different approach than the one described in this paper, Srivastava's research has already created a vaccine against kidney cancer, which is in clinical use and commercially available in Russia.

"It is known that patients have genetic sequences that make them better candidates for some drugs than others. And we can figure that out much more easily now than five years ago," Srivastava says. The novelty of Srivastava's approach in this new research is that it results in a drug specifically designed for a single person. If the approach proves safe and effective, it would be the ultimate in individualized medicine.

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Bioinformatice Department