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Antiretroviral Therapy Lowers HIV Transmission Risk in HIV+/HIV- Couples: "96% reduction in HIV transmission risk to an HIV-negative partner..... definitive proof of the concept that antiretroviral therapy lowers the risk HIV transmission"
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6th IAS Conference on HIV Pathogenesis, Treatment and Prevention, July 17-20, 2011, Rome
Mark Mascolini
Treating HIV-positive people with antiretrovirals lowered the risk that their HIV-negative sex partners would pick up the virus, according to results of the multinational randomized HPTN 052 trial [1]. The IAS Conference offered the first public presentation of the results, though the main findings were released a few months ago [2]. As principal investigator Myron Cohen detailed the data in Rome, the New England Journal of Medicine published results in a free online article [3].
The findings represent the first data from a randomized trial indicating that treating an HIV-positive person with antiretrovirals cuts the risk that they will pass their HIV to a sex partner. The study also yielded evidence that starting treatment at a CD4 count between 350 and 550, rather than waiting till the count drops to 250, has significant clinical advantages [4]. (NATAP reviews that study separately.)
HPTN 052 investigators enrolled 1763 adult couples, 97% of them heterosexual. Researchers recruited couples at 13 sites in Botswana, Brazil, India, Kenya, Malawi, South Africa, Thailand, the United States, and Zimbabwe, but only 2 couples came from the US. The study group included 890 men and 873 women with HIV, all of them with a CD4 count between 350 and 550 within 60 days of entering the trial.
Cohen and colleagues randomized the HIV-positive partner in each couple to start antiretrovirals immediately or to wait until his or her CD4 count fell below 250 or until an AIDS-related disease developed. Among the HIV-positive partners, gender proportions were virtually identical in the immediate and delayed arms. Throughout the trial, both study groups received the same amount of counseling on safe sex and got free condoms, treatment for sexually transmitted infections, regular HIV testing, and evaluation and treatment for any HIV-related complications.
Of 39 HIV infections in HIV-negative partners, the HPTN 052 team genetically linked 28 infections to the trial partner. Twenty-seven of those new infections occurred in couples randomized to delayed antiretroviral therapy, and only 1 occurred in couples randomized to immediate treatment. Those results indicated a 96% reduction in HIV transmission risk to an HIV-negative partner. The one transmission in the immediate-treatment arm occurred soon after therapy began, perhaps before antiretrovirals had a chance to lower viral load in genital secretions. The risk of genetically linked transmission was equivalent in men and women.
Proportions of people in the immediate-treatment group with a viral load under 400 copies rose close to 90% at study month 3 and stayed there or got higher through month 46.
Sexual risk behaviors at enrollment and during follow-up--including sexual activity, condom use, and sexually transmitted diseases--did not differ between partners in the immediate-treatment group and partners in the delayed treatment group. Risk rates were virtually the same for the partners who started the study with HIV and the partners who started free of HIV.
Couples who reported 100% condom use at study entry had a 67% lower risk of linked HIV transmission than couples who reported less than 100% condom use (hazard ratio 0.33, 95% confidence interval 0.12 to 0.91). But the protective effect of antiretroviral therapy was independent of condom use.
Extrapulmonary tuberculosis arose in 17 HIV-positive partners in the delayed-antiretroviral group and in only 3 HIV-positive partners in the immediate-antiretroviral group. Mortality did not differ significantly between the two treatment groups.
The antiretrovirals used (in various combinations) in HPTN 052 were atazanavir/ritonavir (300/100 mg once daily), didanosine (400 mg once daily), efavirenz (600 mg once daily), tenofovir/emtricitabine (300/200 mg once daily), tenofovir without emtricitabine (300 mg once daily), lamivudine (300 mg once daily), lopinavir/ritonavir (800/200 mg once daily or 400/100 mg twice daily), nevirapine (200 mg once daily for 14 days, 200 mg twice daily), stavudine (weight-dependent dosage), and zidovudine/lamivudine (300/150 mg twice daily).
Cohen called these findings "definitive proof of the concept" that antiretroviral therapy lowers the risk HIV transmission.
References
1. Cohen M, Chen Y, McCauley M, et al. Antiretroviral treatment to prevent the sexual transmission of HIV-1: results from the HPTN 052 multinational randomized controlled trial. 6th IAS Conference on HIV Pathogenesis, Treatment and Prevention. July 17-20, 2011. Rome. Abstract MOAX0102.
2. National Institute of Allergy and Infectious Diseases (NIAID). Treating HIV-infected people with antiretrovirals protects partners from infection: findings result from NIH-funded international study. May 12, 2011. http://www.niaid.nih.gov/news/newsreleases/2011/Pages/HPTN052.aspx.
3. Cohen MS, Chen YQ, McCauley M, et al. Prevention of HIV-1 infection with early antiretroviral therapy. N Engl J Med. Online July 18, 2011. http://www.nejm.org/doi/full/10.1056/NEJMoa1105243?query=OF.
4. Grinsztejn B, Ribaudo H, Cohen MS, et al. Effects of early versus delayed initiation of antiretroviral therapy (ART) on HIV clinical outcomes: results from the HPTN 052 randomized clinical trial. 6th IAS Conference on HIV Pathogenesis, Treatment and Prevention. July 17-20, 2011. Rome. Abstract MOAX0105.
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