'Good bacteria' may aid in slowing HIV spread
By Rebecca Bowers
This article originally appeared in the May 2008 issue of Contraceptive Technology Update
Early research indicates that beneficial bacteria found in the healthy vagina aids in reducing the amount of vaginal HIV among HIV-infected women and may make it more difficult for the virus to spread.1
What's next in terms of research when it comes to determining the impact of the beneficial Lacto-bacillus bacteria in affecting HIV transmission? A logical next step would be to better understand factors that determine whether women, HIV-infected and HIV-negative, are colonized with Lactobacillus, particularly the species that produces hydrogen peroxide and other protective factors, says Jane Hitti, MD, associate professor in the Department of Obstetrics & Gynecology at the University of Washington School of Medicine in Seattle. Hitti, who presented study findings at the February 2008 Conference on Retroviruses and Opportunistic Infections, is part of a team of physicians and scientists at the University of Washington and the University of Rochester Medical Center who are working to learn more about how HIV survives and spreads.
"We should explore whether it is possible to establish Lactobacillus colonization among HIV-infected women who do not have this helpful bacteria, and if so, whether colonization alters vaginal HIV viral load," says Hitti.
What factors are needed to promote healthy vaginal flora? A healthy vagina is highly acidic, with a pH less than 4.7. This acid environment is achieved primarily by lactic acid, which is produced by human lactobacilli. With a low pH, the growth of acidophilic organisms such as lactobacilli are encouraged, and the growth of other organisms are inhibited. An elevated vaginal pH is associated with loss of hydrogen peroxide-producing lactobacilli, presence of bacterial vaginosis and trichomoniasis, acquisition of gonorrhea, and enhanced transmission of HIV.2
To conduct the current study, researchers followed a group of 57 HIV-infected women from Seattle and Rochester for up to five years. They looked at changes in their vaginal bacteria, as well as changes in the vaginal viral load and the plasma viral load.
The team found that women with hydrogen peroxide-producing Lactobacillus in the vagina had lower levels of HIV virus in their genital secretions. Findings also indicate that the amount of the HIV virus in the vagina varied in step with the presence of Lactobacillus. Women who did not have the bacteria at first, but who had acquired it by a subsequent visit, had decreased vaginal HIV levels while vaginal HIV levels increased in women in whom the good bacteria had disappeared between visits.
Promote vaginal health
While previous work in the laboratory has indicated that Lactobacillus might help prevent HIV infection in women, the current study provides a direct link to decreased levels of the virus in the vagina with the presence of Lactobacillus that produce hydrogen peroxide there.
Jeanne Marrazzo, MD, MPH, associate professor in the Division of Allergy & Infectious Diseases at the Department of Medicine at the University of Washington, says, "I think the data to support that lactobacilli have a strong protective role in reducing women's risk of getting HIV and other sexually transmitted diseases [STDs] are really quite strong. However, we haven't yet figured out how to give women back their vaginal lactobacilli."
Promoting vaginal health is important for HIV-negative and HIV-infected women, she says. "We know that avoiding douching is important to keeping the lactobacilli healthy, but we don't yet have probiotics available to really recolonize vaginal lactobacilli," states Marrazzo.
Douching is not recommended for the prevention or treatment of vaginitis, according to the American College of Obstetricians and Gynecologists.3 In a study of 1,200 U.S. women at high risk for sexually transmitted infections, douching for symptoms or hygiene, particularly frequent or recent douching, was associated with bacterial vaginosis (BV) and bacterial vaginosis-associated vaginal microflora.4
What roles may probiotics play in vaginal health? While early research surrounding the effectiveness of the administration of lactobacilli for the treatment of BV are mostly positive, it cannot yet be concluded definitively that probiotics are useful for this purpose.5 Attempts are under way to formulate a Lactobacillus preparation that does not alter commensal bacteria.2
References
- Hitti J, Paul K, Agnew K, et al. Protective effect of vaginal Lactobacillus on genital HIV-1 RNA concentrations: Longitudinal data from a U.S. cohort study. Presented at the 15th Conference on Retroviruses and Opportunistic Infections. Boston; February 2008.
- Marrazzo JM. "Normal vaginal flora." In: A Practical Update on Sexually Transmitted Infections: Advances in Diagnosis and Treatment Highlights From a Symposium. Accessed at www.familypracticenews.com.
- American College of Obstetricians and Gynecologists. Vaginitis. Washington, DC: 2006.
- Ness RB, Hillier SL, Richter HE, et al. Douching in relation to bacterial vaginosis, lactobacilli, and facultative bacteria in the vagina. Obstet Gynecol 2002; 100:765-772.
- Falagas ME, Betsi GI, Athanasiou S. Probiotics for the treatment of women with bacterial vaginosis. Clin Microbiol Infect 2007; 13:657-664.
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