Jury out on using ARV prophylaxis
South African guidelines for the preventative use of HIV medication by men who have sex with men who are not infected with the virus are to be published in the peer-reviewed academic publication, Southern African Journal of HIV Medicine, this month.
The treatment, pre-exposure prophylaxis (Prep), consists of an antiretroviral (ARV) pill that is taken daily by HIV-negative people to lower their chances of becoming infected with the virus. The guidelines were developed by a panel of microbiologists, clinicians, virologists, pharmacists and community representatives affiliated to the South African HIV Clinicians’ Society.
Several recent studies have revealed that, if Truvada pills, which contain the ARVs tenofovir and emtricitabine, are taken regularly, they can reduce the risk of men who have sex with men of acquiring HIV by up to 72.8%.
Prep is part of a movement based on the use of ARVs to protect vulnerable groups who are consistently exposed to HIV. In “discordant” couples, where one partner is HIV positive and the other negative, the uninfected person is at a high risk of contracting HIV if condoms are not always used, particularly if the positive partner has a large amount of the virus in his or her blood or sexual fluids because he or she is not yet on ARVs.
HIV-infected people’s chances of infecting their sexual partners with HIV are significantly lower if they are using ARVs, as the medication reduces the amount of virus in their bodies. Men who have sex with men are particularly vulnerable, and HIV infections are on the increase in this group, despite awareness of the effectiveness of condoms.
Another susceptible group is sex workers. They rarely know the HIV status of their clients and unprotected sex is common.
The traditional “ABC” approach, which advocates abstinence, fidelity and condom use, has been largely unsuccessful in preventing HIV infections among some high-risk groups, such as men who have sex with men.
Although the use of ARVs for pre-exposure HIV prevention in uninfected people has not been licensed in South Africa, the co-chairperson of the guideline panel, Dr Kevin Rebe, of the Anova Health Institute’s Health4men project, said advice on how to use Prep was critical because many men who had sex with men were using it.
“The stance that we are taking is that we’re not promoting Prep; we’re promoting the proper use of it for those that are using it anyway. It’s better to provide guidance so that it’s used properly,” Rebe said.
The South African guidelines
recommend that HIV-negative men who have sex with men and are continually exposed to HIV should take Prep while they are exposed, and that they must be made aware that they must take their pills consistently. Prep should be prescribed only once a patient’s HIV-negative status has been established and not for longer than three months at a time. Clinicians must also monitor side effects and drug adherence closely.
Medical experts worldwide are in two minds about whether there is enough evidence to endorse Prep as a formal HIV-prevention method.
Based on what is available, the World Health Organisation and the Joint United Nations Programme on HIV and Aids have pledged to work with countries to protect more men and women from HIV infection. The United States’s Centres for Disease Control and Prevention (CDC) has produced an interim document similar to the South African guidelines, but the British HIV Association has decided not to incorporate Prep into its HIV programme because of a lack of evidence.
According to the US government’s National Institute of Allergy and Infectious Diseases, the science behind Prep is that taking an ARV drug before exposure to HIV could inhibit its replication immediately afterwards, thereby preventing the establishment of permanent infection.
The institute ran one of the first and largest multinational trials of pre-exposure prophylaxis among men who have sex with men (Iprex), which showed that those who took a daily dose of Truvada had on average 43.8% fewer HIV infections than those who received a dummy pill.
Also the medication’s ability to reduce the risk of HIV infection was much greater among those who took it diligently. Those who took the drug 90% of the time had 72.8% fewer HIV infections.
Research among heterosexual people also showed significant decreases in infection. A study in Kenya and Uganda by the University of Washington followed almost 5000 heterosexual couples in which one partner was HIV positive. The risk of infection was reduced by up to 73% in those who received a Truvada tablet every day.
A CDC study conducted in Botswana revealed that there were 77.9% fewer HIV infections among those who took Truvada, when those who had run out of their pills or had not taken one for at least 30 days were excluded.
According to Rebe, it was hard to apply the results of these studies to South Africa:
“Although the Iprex study included some South Africans, there were not nearly enough – 88, half of whom received a dummy pill – to generalise the findings. We are not on strong ground in terms of South African evidence,” he said.
Adhering to the treatment
Rebe also said that in some of the studies many HIV-negative participants did not take their ARVs regularly, which reduced the effectiveness of the treatment.
“Truvada’s side effects includes gastrointestinal problems, unintentional weight loss and kidney dysfunction.
“HIV-positive people, who know they will die if they don’t take the medicine, have good reasons to adhere to the treatment despite the side effects. For uninfected people, however, it’s a very different risk balance. If you don’t take the treatment regularly, you think you’re protected when you’re not,” he said.
Moreover, establishing someone’s HIV status was often complicated, which could make it dangerous to administer Prep because it could lead to drug resistance.
“It’s possible that someone who is HIV positive tests negative because that person is in the window period during which the body has not yet produced the HIV antibodies needed for a positive test. If someone has ongoing sexual risk behaviour, it wouldn’t help to wait for a month and then retest for HIV in order to circumvent the window period, as that person is likely to be constantly exposed to HIV,” Rebe said.
“The danger here is that only HIV-negative people should take Prep. If you’re positive and take the treatment, you run the risk of becoming resistant to certain ARVs,” said Rebe.
He has two patients on Prep. Both have sexual relationships with HIV-infected partners and do not always use condoms. One has been using Prep for six months and the other for three, and neither has become infected. The cost is about R350 a month. As a clinician, in justifiable circumstances, Rebe is legally allowed to use available medication for purposes for which it has not been licensed.
“There is not one HIV prevention method that suits all people. There never will be. You need a menu of prevention options which include both medical interventions and behavioural changes. People need to be able to choose what works best for them,” he said.
Mia Malan works for the Discovery Health Journalism Centre at Rhodes University