Male-to-Female Transmission and the Value of Circumcision

Key words: HIV, Male-to-female transmission, HIV infection in women, Circumcision, Sexually transmitted disease

Making headlines recently was the revelation that HIV infection can be transmitted from men to women through the healthy squamous epithelium of the vaginal tract. Principal investigator Thomas Hope, PhD, professor of cell and molecular biology at Northwestern University Feinberg School of Medicine in Chicago, and coinvestigators found that the natural shedding of skin cells in the vagina allows HIV to penetrate far enough into the epithelium (50 µm), where some of the immune cells targeted by HIV reside.

The findings, presented in December in San Francisco at the 48th annual meeting of the American Society for Cell Biology, were based on laboratory studies using human tissue harvested from hysterectomies and tissue from rhesus macaque monkeys. The researchers labeled HIV with photo-activated tags and observed the virus rapidly penetrate the squamous epithelium of tissue samples.

The findings challenged earlier notions that HIV predominantly penetrates the female genital tract through lesions or through the thin layer of cells of the cervix. In effect, they demonstrated that HIV is easily transmitted through male-to-female sexual contact. The revelation comes on the heels of news that the demographics of who becomes infected with HIV is changing in the United States; women-particularly African Americans-and adolescents are increasingly at risk.¹

With women representing at least 26% of new cases of HIV infection in the United States² and more than half of all new cases worldwide,³ Hope’s take-home message was that the use of condoms needs to be better promoted and that research development on antimicrobials and other technologies that help block viral transmission during sexual activity needs to be stepped up.

Hope conceded in statements to the press that persons cannot be relied on to use condoms or use them consistently and that they forgo condom use for many reasons, justified or not. Alternative strategies are now being considered in the United States because information about the changing demographics of HIV/AIDS is being taken to heart. But the strategies implemented probably will be modeled on those used in Africa, where cultural norms and lack of access to barrier contraception have pushed researchers and educators to devise novel techniques to mitigate the spread of HIV infection.

The effect of male circumcision on HIV transmission has been intensely studied in African populations. The studies generally show that circumcision can help prevent female-to-male and male-to-male transmission, which, in turn, can help prevent male-to-female transmission. A recent study has shown similar results in heterosexual American men.⁴

The study, published in the January 1 issue of the Journal of Infectious Diseases, analyzed HIV testing data of more than 26,000 African American men attending 2 sexually transmitted disease clinics in Baltimore from 1993 to 2000. The men identified themselves as heterosexual and non–drug users and were classified as having either known or unknown exposure to HIV. Known exposure was defined as receiving a notice from a sex partner or a clinic disease intervention specialist about HIV exposure.

Of 40,571 clinic visits, 1096 (2.7%) were associated with positive test results. Of the 394 visits made by men who had a known exposure to HIV, the prevalence of HIV infection among circumcised men was less than half that of uncircumcised men (10.2% vs 22.0%), suggesting that circumcision lowers risk of infection with HIV by 51%.

The findings speak for the value of routine circumcision of male infants; however, Medicaid does not cover the procedure. Ironically, cost and cultural norms are resulting in a decline in the procedure in the United States while the rate of HIV infection in women steadily climbs.

References:

REFERENCES
1. Centers for Disease Control and Prevention. HIV/AIDS among women. http://www.cdc.gov/hiv/topics/women/resources/factsheets/women.htm#3. Revised August 2008. Accessed January 22, 2009.
2. Centers for Disease Control and Prevention. HIV/AIDS Surveillance Report. Vol. 17. Atlanta: CDC, US Department of Health and Human Services; 2005:1-46. Revised June 2007.
3. Joint United Nations Programme on HIV/AIDS. 2004 Report on the global AIDS epidemic. Geneva: UNAIDS; 2004.
4. Warner L, Ghanem KG, Newman DR, et al. Male circumcision and risk of HIV infection among heterosexual African American men attending Baltimore sexually transmitted disease clinics. J Infect Dis. 2009;199:59-65.