Study finds HIV treatment reduces transmission chances to near-zero

A NEW study has found HIV-positive gay men on effective antiretroviral treatment have a near-zero chance of passing the virus on to a HIV-negative partner during unprotected sex, prompting cautious optimism from HIV organisations.

The news comes amid a raft of positive announcements made around HIV research during the Conference on Retroviruses and Opportunistic Infections (CROI) in Boston last week.

The Partner study looked at 282 serodiscordant gay male couples (where one partner is HIV-positive and one is HIV-negative) where the HIV-positive man was on effective antiretroviral treatment with an undetectable viral load and the couple were having unprotected anal sex. The study reported no HIV transmissions in these couples over the course of a year.

These results provide encouraging evidence for the “treatment as prevention” approach to HIV, which focuses on encouraging early diagnosis and treatment of HIV as a way to reduce new infections. People living with HIV on effective treatment and with a low viral load have a significantly reduced chance of passing the virus on, and increased testing and early diagnosis can lead to changes in sexual behaviour to further reduce that chance.

Most Australian HIV and AIDS organisations and research institutes are working within the treatment as prevention paradigm, and several have cautiously welcomed the news from Boston.

“While we’ve known for some time that HIV treatment can be used as a method of HIV prevention, this new research is the most conclusive indication yet about the effectiveness of antiretroviral treatment and the role it has to play in ending HIV transmission,” ACON chief executive Nicolas Parkhill said.

“While this is great news for people with HIV and their partners, it’s also important to note that this is still only an interim result, and while promising, is still not definitive.”

The Kirby Institute’s program head Professor Andrew Grulich was also positive about the results and what they mean for treatment as prevention.

“I echo the cautious optimism expressed by the Partner team. It is important to note that although no new HIV infections were seen in early study results, HIV transmission could occur in up to one per cent of gay couples per year having unprotected anal sex,” he said.

“In those couples at highest risk, where the HIV negative partner has unprotected receptive anal sex with ejaculation with his HIV positive partner, the risk could be higher, with a potential HIV transmission rate of up to four per cent per year.”

The Kirby Institute is looking at HIV transmission risk in gay, serodiscordant couples through their Opposites Attract study, which has been recruiting couples across Australia for the past two years and will soon begin recruiting in Brazil and Thailand.

Other announcements to come out of CROI included the news a baby born with HIV in Los Angeles last year may have been cleared of the virus with treatment within hours of her birth.

Victorian AIDS Council and Gay Men’s Health Centre chief executive Simon Ruth told the Star Observer it was still unclear what the impact of these announcements would be.

“The picture that has emerged from CROI over the last week is complex. Although there have been some encouraging results with the early treatment of babies with HIV, it is still too early to understand the implications of those results to the epidemic as a whole,” he said.

“It is generally conceded by researchers working in this field — including Professor Sharon Lewin from the Burnet Institute — that a cure is decades away.”

Ruth also expressed optimism at the results of the Partner study, and said it was important for understanding the impact of the treatment as prevention approach to HIV, including an increased focus on frequent testing as a way to make people aware of their HIV status.

Ruth echoed comments by Parkhill that HIV-positive people should make an informed decision about whether or not to access treatment.

Researchers at CROI also reported successfully preventing contraction of HIV for weeks at a time in monkeys injected with long-lasting antiretroviral drugs, but stressed the treatment was still years away from being tested on humans.

Scientists working on HIV treatments also announced a successful clinical trial of gene therapy as an alternative to antiretroviral drugs, but were also careful to state the trials were only in the very early stages.