Vaccine for deadly intestinal parasite discovered at U of C

By Laurie Wang 
Posted Aug. 2, 2007

Dr. Kris ChadeeIt's the only amoeba in this world known to kill humans, and a University of Calgary microbiologist just might have the vaccine for it.

Kris Chadee and his team of researchers have developed a non-invasive vaccine that is able to block the harmful Entamoeba histolytica from binding to cells in the intestine in animals.

"It's hard to find a vaccine for the intestinal tract, and this one provides 100 per cent protection in the animals we tested," Chadee says.

The parasite kills an estimated 100,000 people every year worldwide. Though it is rare in developed countries, it affects countries like Mexico and Bangladesh, and areas in South-East Asia and Africa. This intestinal parasite is the cause of amoebic dysentery.

Tourists, people with a lower immune system and young children, are at higher risk of getting the parasite, Chadee explains. Symptoms include bloody stool, diarrhea and liver abscess, he adds.

Chadee and colleagues developed a vaccine made from a protein found on the surface of the amoeba that allows the amoeba to stick to the cells of the intestinal lining. This same protein stimulates antibodies that block it, thus preventing the amoeba from invading the gut because there is no adhesive.

An adjuvant called CpG-ODN was added to the vaccine to make it stronger. This adjuvant, combined with the protein, helps produce antibodies against the pathogen, blocking the amoeba from sticking to cells and stopping the initial invasion, Chadee says.

Once tested on non-human primates, this amoebic dysentery vaccine can then be tested in humans. The results are promising, and it could be the first developed strategy to immunize the intestinal tract against parasites.

"It shows there is tremendous promise in saving over 100,000 people per year from the pathogen," Chadee says.

Chadee's study is also significant in that his team has developed the first non-invasive, intranasal vaccine against a parasite. Gerbils in the study were given intranasal doses (followed by one booster injection).

"This is remarkable, imagine having a simple spray to your nostrils, and this being a vaccine for your gastrointestinal tract," Chadee says. "This could be revolutionary."

Chadee is quick to acknowledge the support he has received from the Faculty of Medicine at the University of Calgary in his research.

"The U of C is a young medical school, but its nucleus of experts in gastrointestinal research is growing and continues to propel us, putting us at the forefront for more discoveries and further research."

About the Faculty of Medicine at the University of Calgary
The U of C's Faculty of Medicine is a national leader in health research with an international reputation for excellence and innovation in health care research, education and delivery. Through its educational programs, the Faculty of Medicine trains the physicians and scientists who will lead the next generation of health practitioners. Through its clinical work, continuing medical education programs, and close relationship with the Calgary Health Region, the Faculty of Medicine moves new treatments and diagnostic techniques from the laboratory bench to the hospital bedside efficiently and effectively, improving patient care.

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