ROME – Bacterial vaginosis and hormonal contraception may increase the risk that HIV-positive women will pass on the infection to their partners, according to two studies presented at the International AIDS Society Conference on HIV Pathogenesis and Treatment.
In addition, a third, small study suggested that measurable HIV RNA may remain in the genital tracts of some women taking antiretroviral therapy.
Dr. Craig R. Cohen of the University of California, San Francisco, presented research exploring the potential association between bacterial vaginosis (BV) and HIV transmission, from a 2-year study of 2,236 HIV-negative men with HIV-positive female partners.
While previous studies had demonstrated that women with BV are at a higher risk of acquiring HIV, Dr. Cohen and his colleagues showed for the first time that BV also makes them more likely to transmit it.
HIV incidence in men whose infected female partner had BV 3 months prior to detecting seroconversion was 2.87/100 person-years (hazard ratio, 3.09), Dr. Cohen and his colleagues found, compared with 0.88/100 person-years in men whose female partners had normal vaginal flora.
After they controlled for sociodemographic factors, sexual behavior, male circumcision, sexually transmitted infections, pregnancy and plasma HIV in female partners, Dr. Cohen and his colleagues still found an elevated risk associated with BV, with an adjusted hazard ratio of 2.83.
The reasons for that were unclear, Dr. Cohen said, though he added it was unlikely that BV increases concentrations of HIV RNA in women. However, BV might affect male partners’ susceptibility, he said.
Bacterial vaginosis affects between 15% and 20% of women in North America and as many as half of women in sub-Saharan Africa, Dr. Cohen said, nothing that 40% of women in his study had vaginosis at enrollment. Normalization of vaginal flora in HIV-positive women could mitigate female-to-male transmission, he said.
Hormonal Contraception Upped Risk
In a second study, the use of hormonal contraception was shown not only to increase women’s susceptibility to acquiring HIV but also to increase their chances of transmitting it.
Renee Heffron of the University of Washington, Seattle, presented a prospective cohort study using data from two trials enrolling 3,750 HIV-discordant couples in seven African countries.
Ms. Heffron and her colleagues found HIV acquisition rates and transmission rates alike to be twofold higher among women using hormonal contraception. Previous studies had demonstrated only higher acquisition rates for women.
Among 2,476 couples in which the women were HIV positive, acquisition rates were 2.61/100 person-years for male partners of women using hormonal contraception, compared with 1.51 for partners of women who did not (HR 1.97, P = .02).
Acquisition incidence was 6.61/100 person-years among women using injected or oral hormonal contraception, compared with 3.78 for those not using the methods (HR 1.98, P = .03). Most of the women in the study were using injectable methods. The number of women using oral contraceptives was not high enough for the findings regarding oral contraceptives to reach statistical significance.
Ms. Heffron and her colleagues also found significantly more HIV-RNA in the genital tracts of infected women on hormonal contraception, suggesting a mechanism for transmission.
The study used data collected between 2004 and 2010, and none of the enrolled seropositive women were eligible for antiretroviral therapy, according to their countries’ guidelines, at the time of enrollment.
Measurable HIV RNA Remains
The results of a third study presented at the meeting suggested that even women taking antiretroviral therapy (ART) have measurable HIV RNA in their genital tracts.
Dr. Anandi N. Sheth of Emory University, Atlanta, presented findings from a small study in which she and colleagues analyzed serum and cervicovaginal lavage (CLV) samples collected twice weekly for 3 weeks from 20 HIV-positive women in the United States.
Though all the women in the study were taking combination antiretroviral therapy (tenofovir, emtricitabine, atazanavir/ritonavir) for at least 6 months and had undetectable serum viral loads at enrollment, HIV-1 RNA was detected at low levels in CLV samples from nine women (45%).
The results suggest that the standard combination ART "does not completely inhibit local viral replication and may not completely block sexual transmission," Dr. Sheth said.
Dr. Sheth said that only one of the women in her study was using hormonal contraception; another was using an intrauterine device. An analysis of vaginal infections among the enrolled women during the study period was in progress, she said, and could shed more light on the findings.
The study presenters did not provide conflict of interest information.