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Malaria Parasite, Potato Famine Pathogen Share Trait

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June 27, 2006

CHICAGO --- The malaria parasite that infects humans and the Irish potato famine pathogen use the same strategy to inject disease-causing proteins into the cells of their respective hosts.

That's what researchers from Northwestern University and Ohio State University reported in the May 31 issue of the journal PLoS Pathogens. 

“It was astonishing to learn that the parasite that causes malaria in humans and the pathogen that caused the Irish potato famine use the same signals to start an infection,” said Kasturi Haldar, Charles E. and Emma H. Morrison Professor of Pathology at Northwestern University Feinberg School of Medicine, the lead author on the study.

“These are very different pathogens evolutionarily. One infects humans while the other infects plants, so their utilization of a shared protein code to establish infection was completely unexpected,” Haldar said.

Haldar also said that it may be possible to develop therapies that could treat both Plasmodium, which causes malaria, as well as Phytophthora, which causes blight in vegetables, such as potatoes and soybeans, in addition to mature trees, such as oak.

Malaria kills over 1 million people, most of whom are young African children.  Malaria also causes poverty and is a major problem in human health globally.  Phytophthora pathogens take a tremendous toll on agriculture by devastating a wide range of food and commercial crops in both the United States and rest of the world.

In earlier research, published in the journal Science in 2004, N. Luisa Hiller, Souvik Bhattacharjee and Christiaan van Ooij in Haldar's laboratory showed that the infection protein sequence in Plasmodium falciparum is a leader sequence which provides the information to malaria proteins on how to infect human cells. Hiller and Bhattacharjee then selected and swapped the leader sequence of P. falciparum with leader sequences of Phytophthora infestans.

In experiments they infected human red blood cells with the modified malarial pathogen. They found that showed that malaria parasite could just as effectively inject proteins and infect human blood cells when it contained the P. infestans leader sequence instead of its own.

“Our findings show that very distinct and distant microbes can share similar strategies for delivering toxic proteins to their targets,” Haldar said.

“This is the first article to show that these types of pathogens that belong to distinctly different evolutionary groups share common infection strategies' and she suggests that this strategy may be even more widely shared among microbes than hitherto suspected,” Haldar said.

This research was supported by grants from the National Institutes of Health, the Great Lakes Research Centers of Excellence and by a National Science Foundation Plant Genome grant.