| Genome Sequence Reveals Leaner, Meaner Intestinal
Cryptosporidium parvum an insidious, one-celled,
waterborne parasite that lodges in the intestines of infected people
and animals and for which there is currently no effective treatment
is missing key structures normally found in similar parasites,
say researchers supported by the National Institute of Allergy and
Infectious Diseases (NIAID), one of the National Institutes of Health.
The results of their genome sequencing project, now available in
the online issue of Science, could help scientists home in
on new drug targets that may lead to therapies for the disease.
C. parvum is an extremely hardy parasite found in water
supplies throughout the world, including the United States. In persons
with healthy immune systems, symptoms of infection include diarrhea,
stomach cramps, upset stomach and fever. For persons with weakened
immune systems, however, such as individuals with HIV/AIDS, symptoms
may be more severe and can lead to serious or life-threatening illness.
Because C. parvum could potentially be used as a bioterrorist
agent, the NIAID has classified it as a Category B priority pathogen.
After reconstructing the predicted genes and resulting proteins
of one form of C. parvum, researcher Mitchell S. Abrahamsen,
Ph.D., University of Minnesota, St. Paul, MN, and his team discovered
that Cryptosporidium is missing two organelles commonly found
in related protozoan parasites. Gone is the apicoplast, a cellular
component that provides essential metabolic functions in related
parasites, including those that cause malaria and toxoplasmosis,
respectively. Also absent is the mitochondrion, the so-called "energy
factory" found in the cells of most plants, animals, fungi
and one-celled organisms. In addition, the researchers found that
Cryptosporidium has significantly fewer genes than related
parasites, and, as a result, can carry out fewer metabolic functions
on its own.
Because Cryptosporidium has been so difficult to study up
until now presumably because its demands for energy and nutrients
have made it virtually impossible to grow in the laboratory
the decoding of the genome sequence provides valuable opportunities
to inform and study the organism's biology. And with an understanding
of its biology, researchers are better positioned to find treatments
that zero in on unique biological processes essential for the organism's
NIAID is a component of the National Institutes of Health, an agency
of the U.S. Department of Health and Human Services. NIAID supports
basic and applied research to prevent, diagnose and treat infectious
diseases such as HIV/AIDS and other sexually transmitted infections,
influenza, tuberculosis, malaria and illness from potential agents
of bioterrorism. NIAID also supports research on transplantation
and immune-related illnesses, including autoimmune disorders, asthma
Press releases, fact sheets and other NIAID-related materials
are available on the NIAID Web site at http://www.niaid.nih.gov.
Reference: MS Abrahamsen et al. Complete genome sequence
of the apicomplexan, Cryptosporidium parvum. Science
DOI: 10.1126/science.1094786 (published online March 25, 2004).