How deadly fungus protects itself

February 4th, 2009 - 5:43 pm ICT by ANI  

Washington, Feb 4 (ANI): Scientists have uncovered how a deadly fungus, called Cryptococcus neoformans, evades the human immune system and causes disease.

The study by researchers at Albert Einstein College of Medicine of Yeshiva University may help scientists develop new therapies or vaccines against infections caused by the fungus.

Usually, such fungal infections occur in those with compromised immune systems especially AIDS patients and transplant patients who must take lifelong immunosuppressive therapy.

The fungus causes an estimated one million deaths each year worldwide, including some 600,000 in sub-Saharan Africa.

The lead author of the study was Susana Frases-Carvajal, Ph.D., a postdoctoral fellow in microbiology & immunology at Einstein.

Normally, C. neoformans enters the body through the lungs and can spread throughout the body, including the brain.

The resulting infection, called cryptococcosis, can cause chest pain, dry cough, abdominal swelling, headache, blurred vision, or confusion. The infection can be fatal, especially if not treated with antifungal medications.

“It’’s a horrendous disease, and even with therapy, you often can”t get rid of it,” said the paper’’s senior author, Arturo Casadevall, M.D., Ph.D., professor and chair of microbiology & immunology.

Itfs known that the capsule surrounding C. neoformans is essential to its ability to cause disease. When the fungus enters a host, the capsule begins to enlarge.

“As the capsule grows larger, it reaches a point where immune system scavenger cells, known as macrophages, can”t swallow it. But we didn”t understand the mechanism responsible for capsule growth,” said Dr. Casadevall.

The protective capsule of C. neoformans is composed of polysaccharides, which are long chains of sugar molecules, or saccharides.

Using a technique called dynamic light scattering, researchers found that the capsule grows by linking more and more saccharides together at the outer edge of the capsule, forming giant molecules pointing in an outward, or axial, direction.

The findings point to potential new targets for drug intervention and reveal a new area of investigation into basic polysaccharide biology.

“Also, scientists have tended to view polysaccharides as boring molecules that simply grow to a specified length,” said Casadevall.

The study is published in the journal Proceedings of the National Academy of Sciences (PNAS). (ANI)

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