( exposure to the parasite. Both m...)Scientists sequence genome of parasite responsible for common sexually transmitted infection

Both men and women with trichomoniasis have an increased susceptibility to HIV infection and may transmit HIV to their sexual partners. Pregnant women with trichomoniasis may deliver a low birthweight (less than five pounds) or premature infant. Although the prescription drugs metronidazole and tinidazole usually cure trichomoniasis, drug resistance has become an increasing concern.

T. vaginalis is pear-shaped with thread-like flagella that propel its movement. Once it attaches to cells lining the host's urinary or genital tract, it flattens out and begins to ingest the cells, as well as white and red blood cells, causing direct damage to the urinary and vaginal tissues and resulting in inflammation. T. vaginalis also consumes bacteria that may be present in the urinary and genital areas, including the bacteria necessary for maintaining a normal healthy environment in the vagina. As a result, women infected with trichomoniasis become more susceptible to becoming infected by HIV and other STIs.

In generating the genetic blueprint for the parasite, researchers were surprised to find such a large and highly repetitive genome comprising nearly 26,000 predicted genes as determined by computer models and previously sequenced parasitic genomes. Repetitive genes accounted for roughly 65 percent of the genome.

"Parasites generally have smaller amounts of DNA than non-parasitic organisms, but in this case, there was ten times as much DNA than we originally thought there would be," says lead author Jane M. Carlton, Ph.D., who led the project while at The Institute for Genomic Research (TIGR), a not-for-profit research organization based in Rockville, Maryland. Dr. Carlton is now an associate professor in the Department of Medical Parasitology at New York University's School of Medicine.

Although it is not entirely clear why the genome is so large and repetitive, researchers theorize that the parasit
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Source:NIH/National Institute of Allergy and Infectious Diseases