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BookmarkScienceDaily (Oct. 6, 2003) — Rockville, MD – Scientists at The Institute for Genomic Research (TIGR) are beginning to unravel the mysteries of the most prevalent human parasite in North America, Trichomonas vaginalis. On October 1, TIGR released the first draft assembly of the T. vaginalis genome into the public domain.
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One surprising result of the initial research is that the parasite's genome, at between 80 million and 90 million DNA base pairs, is more than five times larger that had been estimated before the sequencing project began. Although the genome is not yet completed, TIGR is releasing data at regular intervals during the sequencing process for the scientific community.
T. vaginalis is the most prevalent parasite in North America, where it is responsible for approximately 5 million cases of vaginitis each year. As a result of sequencing the genome, researchers are now starting to understand some aspects of the sexually-transmitted parasite's biology.
"Identifying the complete gene set of the parasite should help researchers find new ways to treat or prevent the disease" says Jane Carlton, TIGR's lead investigator in the T. vaginalis project, which is being funded by the National Institute of Allergy and Infectious Diseases (NIAID) under cooperative agreement U01 AI050913.
Noting that scientists were surprised by the actual size of the parasite's genome, Carlton says analysis of the data should help determine "whether the genome's size results from a large number of genes or a large number of highly repetitive sequences."
T. vaginalis is of special interest to biomedical researchers because it is emerging as an important factor in facilitating HIV transmission, for example in African-American communities of the United States. Individuals infected with T. vaginalis have a significantly increased incidence of HIV transmission made possible by an aggressive immune response and a heavy influx of target cells for HIV. This response may increase the chance of entry of HIV in HIV-negative individuals. Conversely, in HIV-positive individuals, the hemorrhages that are frequently associated with T. vaginalis infection tend to worsen shedding and subsequent transmission of the virus.
In addition to its role in HIV infection, trichomoniasis is also associated with pre-term delivery, low birth-weight, increased infant mortality and predisposition to cervical cancer. Given its prevalence and the role that T. vaginalis plays in several serious medical concerns, the ability to rapidly identify potential vaccine candidates for T. vaginalis, using genomic sequence, is a priority in the research community.
The Trichomonas genome sequence is also expected to deepen the understanding of several other human pathogens. T. vaginalis is a member of a group of organisms called the amitochondriates, which do not use oxygen for metabolism. Other members of that group include Giardia lamblia, which causes traveler's diarrhea, and Entamoeba histolytica, which causes amebiasis. Various species of Entamoeba are now being sequenced by scientists at TIGR (http://www.tigr.org/tdb/e2k1/eha1/ ).
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Carlton is TIGR's lead investigator on the T. vaginalis project, which is being carried out in collaboration with Patricia Johnson of the University of California-Los Angeles' Department of Microbiology, Immunology and Molecular Genetics.
The newly released sequence data can be obtained from the TIGR website at the following link: http://www.tigr.org/tdb/e2k1/tvg
The Institute for Genomic Research (TIGR), which sequenced the first complete genome of a free-living organism in 1995, is a not-for-profit research institute based in Rockville, Maryland. TIGR conducts research involving the structural, functional, and comparative analysis of genomes and gene products in viruses, bacteria, archaea, and eukaryotes.
