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A microscope shot of the E. histolytica parasite.

Under the microscope: Entamoeba histolytica cysts, colored by trichrome (a staining technique).

Designing a new vaccine

By Bruce Erickson

January 4, 2006

Many of us take clean drinking water and a sanitary food supply for granted. In fact, for many parts of the world the lack of clean drinking water and unsanitary food conditions can lead to a disease called amebiasis.

Amebiasis is caused by a single-celled parasite called Entamoeba histolytica or E. histolytica, an amoeba that commonly parasitizes humans and can cause a breakdown of body tissues during infection. The parasite is contracted by swallowing contaminated food or water.

Worldwide, in endemic areas such as India, Africa, Asia, Mexico, and South America, up to 60 percent of the population is infected each year. Of those with infections, up to 10 percent develop symptoms such as colitis or liver abscess. With an annual toll of up to 100 million cases and 100,000 deaths, amebiasis ranks among the world's most serious parasitic infections.

Thanks to research being done by University of Minnesota Department of Medicine's Jonathan Ravdin and Mohamed Abd-Alla, however, there may soon be a vaccine to prevent amebiasis.

"The goal when I started amebiasis research was to understand the basic mechanisms by which the parasite invaded the host, understand the human immune response, and look at those two components to rationally design a effective vaccine," says Ravdin.

Ravdin, a professor, and Abd-Alla, an associate professor, have developed the vaccine using synthetic peptides to stimulate the body's immune system to make antibodies against the key protein E. histolytica needs to create an infection. "The beauty of this approach is that we can sensitize and immunize people and as individuals go into an endemic area, they constantly get exposed to the parasite and in effect get boosters to sustain their immunity," says Ravdin.

Over the next few years Ravdin hopes to start phase one clinical trials for the vaccine, and currently, the University is working with companies from India to license the rights for further development and marketing.

"The dream 25 years ago when we started this research was to produce a vaccine, and if this works it will be the most gratifying thing that can happen," says Ravdin.