Gene Mapping Finds Surprises in Itchy Genital Bug

Gene Mapping Finds Surprises in Itchy Genital Bug

Researchers conducting a National Institutes of Health-funded study have mapped the genome of Trichomonas vaginalis, the cause of the often asymptomatic STD that infects at least 170 million people globally. The one-celled parasite Trichomonas is especially dangerous to women, making them more vulnerable to HIV, gonorrhea, and syphilis.

Dr. Jane Carlton of New York University's School of Medicine and a team of 66 researchers in 10 countries found the protozoan contains nearly 26,000 confirmed genes - almost as many as the human genome. "It was a huge shock," said Carlton, who led the study while at Maryland's Institute for Genomic Research. The scientists speculate it may have something to do with aiding the pear-shaped organism in infecting the urogenital tract.

Another surprise is that Trichomonas contains genes that appear to originate from bacteria. Some of these genes allow Trichomonas to synthesize the amino acid cysteine, thus letting it manipulate the vagina's environment. "The pH shifts toward more alkaline and that makes the vaginal environment not as healthy," said Carlton. An alkaline environment allows HIV and other STDs to take hold more easily.

Reuters (01.11.07):: Maggie Fox

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Persons at risk for HIV-2 infection include:

Sex partners of a person from a country where HIV-2 is endemic (this category includes persons originally from such countries).

Sex partners of a person known to be infected with HIV-2.

Persons who received a transfusion of blood or a nonsterile injection in a country where HIV-2 is endemic.

Persons who shared needles with a person from a country where HIV-2 is endemic or with a person known to be infected with HIV-2.

Children of women who have risk factors for HIV-2 infection or who are known to be infected with HIV-2.

Additionally, testing for HIV-2 is indicated when there is clinical evidence for or suspicion of HIV disease (such as an AIDS-associated opportunistic infection) in the absence of a positive test for antibodies to HIV-1 and in cases in which the HIV-1 Western blot exhibits the unusual indeterminate pattern of gag (p55, p24, or p17) plus pol (p66, p51, or p32) bands in the absence of env (gp160, gp120, Or gp41) bands.

Although most HIV infections in the United States are of HIV-1 group B subtype, current ELISAs can accurately identify infections with nearly all non-B subtypes and many infections with group O HIV subtypes. Infections with HIV-2 and HIV-1 group O are rare in the United States and routine screening for these subtypes is not generally recommended as part of diagnostic testing except in areas where several such infections have been identified. Routine screening for HIV-2 might be appropriate in certain populations where potential risk for HIV-2 infection is higher (e.g., in areas where West African immigrants have settled). Since June 1992, FDA has recommended routine screening for antibody to HIV-2 (in addition to HIV-1) for all blood and plasma donations. Clients with clinical, epidemiologic, or laboratory history that suggests HIV infection and negative or indeterminate HIV-1 screening tests should receive further diagnostic testing to rule out HIV infection, potentially including testing for HIV-1 non-B subtypes and HIV-2 .

Blood centers can accomplish this either by the use of a single combination test for HIV-1/HIV-2 or by the use of two independent tests, one for HIV-1 and one for HIV-2. Screening donated blood and plasma for HIV-2 infection raises issues concerning appropriate strategies for testing for both viruses, HIV-2 testing in other settings, and notification of HIV-1 and HIV-2 test results. What follows are CDC recommendations for the diagnosis of HIV-1 and HIV-2 infections in persons being tested in settings other than blood centers and CDC/FDA guidelines for serologic testing with combination HIV-1/HIV-2 screening ELISAs.

Although HIV-2 appears to have spread in West Africa primarily via heterosexual transmission, HIV-2 infection has been reported in Europe in homosexual men, injecting drug users (IDUs), transfusion recipients, and men with hemophilia. HIV-2 is endemic in parts of West Africa and has also been reported in other parts of Africa. Apparently as a result of links with former colonies in West Africa, Portugal and France have reported the highest number of cases of HIV-2 infection in Europe. As of late 1989, 12.6% of AIDS cases in Portugal were caused by HIV-2. Although most of these cases were in persons originally from Africa, HIV-2 is also present among persons in Portugal with no known contacts with Africa. HIV-2 infection has also been reported in India.

In the Western hemisphere, rare cases of HIV-2 infection have been reported from Brazil, Canada, and the United States. Within the United States, CDC and others conduct surveillance for HIV-2, including serologic surveillance of blood donors and populations at increased risk of HIV-1 infection.

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