Thursday, April 25, 2024
News and Views from the Global South
HEALTH: Using ARVs to Prevent as well as to Treat HIV
Kristin Palitza
- Researchers are now investigating if antiretroviral (ARV) drugs can play a role in not just treating HIV, but in preventing infection. Mitchell Warren, executive director of the AIDS Vaccine Advocacy Coalition (AVAC), called it “a pivotal moment in HIV/AIDS research”.
Electron micrograph of human immunodeficiency virus (HIV): a new proposal is testing whether wider use of ARVs can prevent the spread of the virus. Credit: Cynthia Johnson/CDC
ARV-based prevention aims to protect HIV-negative people from getting infected with the virus, similar to the way in which chloroquine is used to prevent malaria.
“Pre-exposure prophylaxis [PrEP] is biologically plausible, and mathematical modelling suggests substantial potential public health benefits,” said Professor Salim Abdool Karim, director of the Centre for the AIDS Programme of Research in South Africa (CAPRISA) in Durban. “It could prevent millions of new infections every year.”
Research in macaque monkeys has shown that a single dose of Tenofovir, one of the drugs used as ARV treatment, when administered before exposure to HIV, prevents transmission of the virus by 100 percent, Abdool Karim pointed out. “We have good grounds for optimism, but have to wait for the results of human trials,” he added.
In January 2008, researchers from the Swiss Federal Commission for HIV/AIDS (SFC) released a statement that HIV-positive individuals on effective antiretroviral (ARV) therapy and free from other sexually transmitted infections (STIs) can be sexually non-infectious.
Basing their recommendation on epidemiological and biological data from 26 international studies, the four SFC researchers said their finding is valid as long an HIV-positive person adheres strictly to ARV therapy - the effects of which must be evaluated regularly by a physician - viral load has been suppressed to below detectable levels (less than 40 copies of the virus per millilitre of blood) for at least six months and the individual has has no other STIs.
The researchers assert that effective ARV treatment eliminates HIV from genital secretions, noting that HIV ribonucleic acid, measured in sperm as well as in female genital secretions, declines below the limits of detection, even though cell-associated viral genomes are present in genital secretions.
The statement also discussed the implications for doctors, HIV-positive people, HIV prevention and legal systems.
Abdool Karim cautioned, however, that before rolling out ARV-based prevention on a large scale, researchers needed to answer a number of questions. How safe is it to give healthy people chronic medication? Could it lead to the development of ARV-resistant strains of HIV? How often should people on PrEP be tested?
“If we get people to test once a year and put [those who test HIV-positive] onto ARVs immediately, we have a very good chance to lower transmission rates [of the virus],” said Doctor Francois Venter, head of the HIV management cluster of the Reproductive Health and HIV Research Unit of the University of the Witwatersrand in Johannesburg.
As a result, “we can decrease prevalence of the actual disease,” he reckoned. Currently, in line with the South African health department’s treatment guidelines, people living with HIV have free access to ARVs if they have a CD4 count of 200 or below. A CD4 count measures the number of T-helper cells in a person’s body.
Venter stressed the need to move away from “feel-good” prevention messages, such as “be faithful”, towards science-based prevention programmes, such as ARVs.
“We have been through 25 years of failed prevention [because HIV prevalence continues to rise],” he said. “There is not a single sign of reversing this pandemic with the current prevention methods.”
Abdool Karim agreed, pointing out that for the group in which HIV prevalence is increasing fastest – young women – “most of the existing prevention methods are not an option”.
AIDS prevention campaigners stress abstaining, being faithful, using condoms, male circumcision and voluntary counselling and testing (VCT). “None of these fundamentally address the vulnerability of young women,” he said.
Venter recommends pushing for early diagnosis of HIV combined with fast access to ARVs, noting that only 20 percent to 40 percent of HIV-positive South Africans are accessing HIV care to date. “We are doing badly. We need to give people good, non-toxic ARVs long before they get sick,” he said.
Venter believes that although providing ARVs to everyone who is HIV-positive would initially increase AIDS spending significantly, it would save money in the long-term as more HIV-positive people would stay healthy and fewer people would be newly infected with the virus.
In addition, Venter reckons ARV-based prevention will dramatically cut hospital spending on opportunistic infections such as tuberculosis. “A patient spending two days in hospital costs as much money as two years of ARVs,” he explained.
In South Africa, hospitalisation costs between $106 and $212 a day, while ARV treatment costs between $318 and $424 a year.
Venter noted, however, that governments would have to “massively scale-up health systems for chronic care”, since HIV is a chronic disease. “If we fix the health system and get people into HIV care earlier, we wouldn’t need so many drugs,” he added.
Despite the strong case for ARV-based prevention, there has been little public debate on the topic so far. Venter says using ARVs as a preventative tools is “like a huge elephant in the room because it is a huge controversy”.
The debate about the pros and cons of ARV-based prevention was launched in August 2008 at the XVII International AIDS Conference in Mexico City, after researchers from the Swiss Federal Commission for HIV/AIDS (CFS) published a paper stating that HIV-positive people on ARV treatment with an undetectable viral load cannot infect their sexual partners.
Critics say promoting ARV-based prevention will undermine other prevention efforts, such as the ABC (Abstain, Be faithful, use Condoms) approach, by encouraging people to have unprotected sex, as their viral loads will be undetectable due to the treatment.
The topic was taken further when several World Health Organisation (WHO) researchers published the first scientific article on the potential benefits of ARV-based prevention in early December 2008 in medical journal The Lancet.
Treatment Action Campaign (TAC) national programme manager Nomfundo Eland believes ARV-based prevention “is very promising” but needs to be linked to other prevention strategies. It could play a particularly important role for reproductive health rights of discordant couples who want to conceive and women affected by gender-based violence, she said.
Print
|
