STD Quarterly-Emerging technologies for detection and treatment of STDs hold promise
Research is ongoing for microbicide candidates and vaccines
What will be the status of detection and treatment of sexually transmitted diseases (STDs) in the next five years? While that timeline may be too close in for the market debut of an effective microbicide for HIV or a vaccine for genital herpes, experts point to promising research on several fronts in the field of reproductive health.
"With new emerging technologies in diagnostic and treatment options for people with sexually transmitted diseases, health care providers will have better resources to manage infections," predicts Linda Alexander, PhD, FAAN, president of the American Social Health Association in Research Triangle Park, NC. "New diagnostic options will provide more sensitive and specific tools to detect multiple STDs and new treatment options will afford better management of viral infections."
This year will bring new prevention and treatment guidelines from the Atlanta-based Centers for Disease Control and Prevention (CDC). The agency’s STD Treatment Guidelines are being revised following a comprehensive evaluation performed in September 2000.
The new guidelines will recommend that sexually active adolescent women be screened for chlamydial infection at least annually, even if symptoms are not present, states Judith Wasserheit, MD, MPH, director of the division of STD prevention in CDC’s National Center for HIV, STD, and TB Prevention. Annual screening of all sexually active women ages 20-25 also will be recommended, as will screening of older women with risk factors such as new sexual partners or multiple sexual partners, she states.
Focus on microbicides
Fall 2001 is the projected start for a Phase III efficacy trial of two microbicide candidates in the search for a female-controlled prevention method against HIV. The trial is sponsored by the HIV Prevention Trials Network (HPTN), a program established by the Bethesda, MD-based National Institutes of Health (NIH) to develop and test nonvaccine strategies to prevent the spread of HIV infection and AIDS. The two products to be evaluated are BufferGel from ReProtect LLC of Baltimore and PRO 2000 from Interneuron Pharmaceuticals Inc. of Lexington, MA.
BufferGel is a nonirritating lubricant made of a carbopol gel, which is a high-molecular weight, cross-linked, polyacrylic acid. Pro 2000 is a naphthalene sulphonate derivative in a gel formulation. (See Contraceptive Technology Update, April 1999, p. 37, for more information on these two novel microbicides.) The international study protocol is in development, reports Roberta Black, PhD, a microbiologist in the division of AIDS at the Bethesda, MD-based National Institute of Allergy and Infectious Diseases (NIAID).
There are many promising microbicide products now in the research pipeline, with several having completed Phase I or II testing, observes Willard Cates Jr., MD, MPH, president of Family Health International (FHI). FHI is a Research Triangle Park, NC-based research organization that has been designated by the NIH to coordinate the HPTN effort.
"A big push is needed during the next several years to support global phase III microbicide research infrastructures capable of assessing the effectiveness of these new products," states Cates.
Added emphasis to the search for effective microbicides comes with the July 2000 release of preliminary results from a large international study of a microbicide gel containing the spermicide nonoxynol-9 (N-9).1 Results indicate that among the study population of female sex workers, those using a gel containing N-9 had a higher risk of acquiring HIV than those using the placebo vaginal moisturizer. (See CTU, October 2000, for the CDC’s recommendations concerning use of N-9 in STD prevention, as well as a companion story on the use of the spermicide in pregnancy prevention.)
While the results of the study indicated that N-9 is not effective in preventing HIV, further research is needed to study its impact in more typical N-9 users, says Cates. Until there are more data on the risks of the spermicide in typical settings, women who use N-9 for contraception should continue in their current practice, he says.
The search for an effective vaccine against herpes simplex virus 2 (HSV-2), the strain responsible for most cases of genital herpes, continues following initial reports from two large clinical trials.2 Preliminary research indicates that the vaccine proves highly effective compared with a placebo, but is effective only in women, not men, and only in women who have not been previously infected with herpes simplex virus 1 (HSV-1), the strain responsible for most cases of oral herpes.3 The trial data are under review by Smith-Kline Beecham Biologicals in Belgium, the vaccine manufacturer, and the Food and Drug Administration.
On one hand, the findings suggest the vaccine may be helpful for a relatively small portion of the population, but on the other hand, it is proof that scientists can develop a vaccine that can make a difference, comments Edward Hook III, MD, professor of medicine at the University of Alabama at Birmingham and medical director of the Jefferson County STD Control Program.
"Even if you can only protect a portion of the women, that’s a whole lot better than anything you could do before," states Hook. "Further evaluation of those tests and further tests of even better vaccines are on the horizon and are very important areas."
Hook points to the increased use of type-specific serologic tests as an important step in the fight against HSV-2. Testing options for herpes simplex virus (HSV) have expanded in the United States, with three companies offering new diagnostic methods. (See the STD Quarterly inserted in the August 2000 issue of CTU, p. 3, for a review of the current tests.)
While it is a treatable infection, there is no cure at present for HSV-2. The debate over increasing the knowledge of one’s HSV-2 status in light of no known cure will be an important one in the coming years, Hook predicts.
Rapid testing moves up
The recent availability of inexpensive, noninvasive tests and single-dose therapy will make it easier to identify and treat women infected with chlamydia, states Wasserheit. (See the STD Quarterly inserted in the February 2001 issue of CTU, p. 1, for more information on nucleic acid amplification tests.)
Point-of-care rapid diagnostics will have patient and public health impact in the coming years, predicts Holli Hamilton, MPH, branch chief for the Office of Clinical Research Affairs in the division of microbiology and infectious diseases at NIAID. New tests are being developed that might provide better ways to diagnose syphilis and define the stage of infection, she notes.
Research is under way to evaluate the use of azithromycin as a suitable one-dose treatment for syphilis, Hamilton reports.4 If the drug indeed proves efficacious, then the ramifications are great for having one drug for use against the major bacterial STDs, she states.
Look to use of vaginal swabs as an acceptable specimen for certain STDs in the next five years, says Hamilton. For screening purposes, such a collection method would prove "vastly simpler" than a pelvic exam, she states.
"We can expect to see more research into options that enable women to self-sample for STDs," agrees Alexander. "Home testing for STDs is clearly a possibility."
References
1. Van Damme L, Masse B, Laga M, et al. Vaginal microbicides, an update. XIII World Conference on HIV/AIDS. Durban, South Africa, July 12, 2000.
2. Stephenson J. Genital herpes vaccine shows limited promise. JAMA 2000; 284:1,913-1,914.
3. Spruance S. Gender-specific efficacy of a prophylactic SBAS4-adjuvanted gD2 subunit vaccine against genital herpes disease: Results of two clinical efficacy trials. Presented at the 40th Interscience Conference on Antimicrobial Agents and Chemotherapy. Toronto; Sept. 17, 2000. Abstract L-6.
4. Hook EW, Stephens J, Ennis DM. Azithromycin compared with penicillin G benzathine for treatment of incubating syphilis. Ann Intern Med 1999; 131:434-437.
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