HIV-positive gay men can have unprotected sex without fear of transmitting the killer virus if they take daily pills, a major study has found.
The eight year-long trial, led by British and Danish researchers, found those given antiretroviral therapy (ART) are sexually non-infectious.
No evidence exists to show transmission of HIV, which leads to AIDS if left untreated, can occur when viral loads are deemed ‘undetectable’.
The results of the trial, derived from nearly 1,000 gay couples, were unveiled today at the 2018 AIDS conference in Amsterdam.
The study is the largest to assess the risk of HIV transmission among couples where one partner is positive for the virus and on ART.
ART involves patients taking daily pills to stop the virus replicating – reducing the risk of transmission. However, the drugs do not cure people of HIV.
The eight year-long trial, led by a team of British and Danish researchers, found those given antiretroviral therapy (ART) are sexually non-infectious
Researchers from University College London and the University of Copenhagen today argued the importance of an early HIV diagnosis, to get people on ART.
Evidence already exists to show HIV transmission risk is zero among heterosexuals. But the new trial is the first to confirm the same findings in gay men.
Almost 1,000 gay male couples from 14 different countries in Europe were involved in the study, conducted between 2010 and 2018.
Couples reported almost 77,000 episodes of condomless anal sex over this period, with no linked HIV transmissions occurring.
However, 15 men, who were originally HIV negative, did become positive during the study, called PARTNER2.
But by comparing the structure of each virus in the laboratory, it was possible to show the infections were completely different.
WHAT IS ANTIRETROVIRAL THERAPY?
Antiretroviral therapy drugs are given to HIV patients to help them battle the killer virus.
ART involves patients taking daily pills to stop the virus replicating. However, the drugs do not cure people of HIV.
Doctors recommend taking a combination, or ‘cocktail’, of at least two ART drugs, which are broken into six groups because they work in different ways.
1) Nucleoside/Nucleotide Reverse Transcriptase Inhibitors (NRTIs)
NRTIs force the virus to use faulty versions of building blocks so infected cells can’t make more HIV.
2) Non-nucleoside Reverse Transcriptase Inhibitors (NNRTIs)
NNRTIs bind to a specific protein so the virus can’t make copies of itself.
3) Protease Inhibitors (PIs)
These drugs block a protein that infected cells need to put together new copies of the virus.
4) Fusion Inhibitors
These drugs help block HIV from getting inside healthy cells in the first place.
5) CCR5 Antagonist
This stops HIV before it gets inside a healthy cell, but in a different way than fusion inhibitors. It blocks a specific kind of ‘hook’ on the outside of certain cells so the virus can’t plug in.
6) Integrase Inhibitors
These stop HIV from making copies of itself by blocking a key protein that allows the virus to put its DNA into the healthy cell’s DNA
As a result, the researchers led by Dr Alison Rodger concluded that the new HIV infections were not acquired from the HIV positive partner.
Dr Rodger said: ‘The PARTNER2 study was designed to find whether HIV transmission occurs in gay men when viral load was suppressed.
‘Despite these couples having sex without condoms 75,000 times we did not find a single case.
‘PARTNER2 data provides robust evidence for gay men the risk of HIV transmission with suppressive ART is effectively zero.’
She added the study supports the message of the international campaign, U=U (Undetectable = Untransmittable).
Dr Rodger also said the results ‘underline the importance’ of an early diagnosis for HIV, so men can begin on anti-retroviral therapy.
The PARTNER2 study follows its predecessor, PARTNER1, which indicated people with an undetectable viral load cannot pass on HIV.
Gay and bisexual men are most susceptible to catching HIV because anal sex carries a 10 times higher risk of infection than vaginal.
This is due to cells in the anus being more susceptible to HIV, as well as fluid in semen and the anus’ lining carrying more HIV than vaginal secretions.
Professor Jens Lundgren, co-author for the study, said: ‘In 2015 we proved that it was better to start HIV treatment as soon as possible.
‘We have now provided the scientific evidence for how effectively treatment prevents further sexual transmission.’
Simon Collins, an HIV positive treatment activist, said the study addresses questions from gay men over their risk of transmitting the killer virus.
Commenting on the study, he said: ‘There is no evidence that HIV transmission can actually occur when viral load is undetectable.’
Michael Brady, medical director at Terrence Higgins Trust, said: ‘We’re thrilled that the PARTNER2 results are out, and confirm what we already knew: that people living with HIV on effective treatment cannot pass the virus on to their sexual partners.
‘The two studies [PARTNER1 and PARTNER2] scientifically prove this, and will be so powerful in helping to fight the stigma and myths that still surround HIV.
‘What’s most important now is ensuring that we continue to share this message and educate people as far and wide as possible, to help improve the lives of people living with HIV across the world.’
An estimated 36.7 million adults and children worldwide have HIV, including at least 88,800 in the UK and around one million in the US.
The virus progressively damages the cells in the immune system weakening the body’s ability to fight infections.
Without treatment, this leads to AIDS – the collective name for a series of life-threatening infections which the weakened immune system cannot withstand.