The field of HIV treatment and prevention has been freshly energised by the findings from several recent clinical trials.
By Edwina Wright, Monash University
Maintaining the momentum of scientific discoveries and breakthroughs is critical to preventing further HIV infections, improving care for the 35 million people living with HIV and because other critical global health priorities compete for funding in our fiscally-constrained world.
While many breakthroughs in HIV research have happened over the past couple of years, I’m going to explore five of the most significant of these in recent times.
Treatment as prevention
In the area of HIV prevention, striking findings were reported recently by the European PARTNER study group.
The study recruited gay and heterosexual couples who practice condomless sex where one partner was HIV positive (this means they are HIV “serodifferent”). To participate in the study, the HIV positive partner had to be on treatment that had fully suppressed the virus. This happens in approximately 90% of people who adhere well to their HIV treatment.
Researchers reported the risk of HIV transmission was remarkably low: their findings suggest that over a 10-year period of practicing condomless sex, HIV transmission would occur in only 4%, or one in 25 couples.
This research demonstrates the principle of “treatment as prevention” – where the treatment of HIV positive people prevents onward transmission. It provides long-awaited information to help HIV serodifferent couples navigate transmission risks during sexual intimacy.
Another important HIV prevention measure is known as pre-exposure prophylaxis. This involves people at risk of infection taking a daily antiretroviral tablet in conjunction with other HIV prevention measures, such as condom use and regular testing for HIV and other sexually transmitted infections.
Over the past few years, several studies enrolling people who inject drugs, men who have sex with men as well as heterosexuals have shown that pre-exposure prophylaxis can reduce HIV transmission by between 44% and 75%. It’s also been showed to reduce risk of transmission among people who adhere to their daily medication by 99%.
In Australia, pre-exposure prophylaxis is currently available in Victoria and will soon be available in New South Wales and Queensland, via demonstration projects where its use, effectiveness and acceptability will be studied.
A number of combinations of antiretroviral agents are available for people living with HIV who choose to start this treatment. Several of these regimens require only tablet daily.
This small pill burden and the relatively low toxicity profile of newer antiretroviral drugs make it easier for people living with the virus to adhere to their medications.
To further enhance adherence, injectable long-acting antiretroviral treatments have been designed and are being evaluated in early clinical trials. These agents may last for up to 12 weeks and could theoretically be used for the purpose of HIV treatment and prevention.
Co-infection of HIV and hepatitis C
People who are co-infected with both HIV and hepatitis C are at risk of developing severe liver disease, and are at risk of more rapid development of cirrhosis of the liver.
In 2012, approximately 9% of HIV positive people in Australia were co-infected with hepatitis C. In other countries, up to 80% of HIV positive people who inject drugs are co-infected with hepatitis C.
Recent data from several studies have shown new treatments for hepatitis C are highly effective, with lower toxicity and shorter treatment durations (eight to 24 weeks) than older treatment regimens, which took up to 48 weeks.
The efficacy of these agents in people who have both hepatitis C and HIV infection are being evaluated in several studies. One of the big challenges for using this approach is getting price reductions for both the older and new agents used for hepatitis C treatment.
Towards a cure
The chief obstacle to curing HIV infection is the virus' persistence in a latent form within certain cell reservoirs in the body.
The main challenges for finding a cure for HIV infection then include preventing the virus from establishing latency in these cellular reservoirs during acute infection, and removing the latent virus from reservoirs during chronic infection.
It’s possible the development of latent HIV reservoirs was prevented in the case of the “Mississippi Baby“ who received HIV treatment within 30 hours of delivery. This treatment was continued for 18 months, and tests have shown that even at 40 months of age, she has no virus detectable in her blood plasma.
Initiatives to prevent HIV from establishing latency and to remove latent HIV from the reservoirs during chronic HIV infection, including boosting the immune system with vaccines, are planned or underway in several clinical studies. The community is waiting to hear their results.
These five areas are just some in the ways HIV science is progressing. We expect to hear the results of several of these and other studies at the 20th International AIDS Conference to be held in Melbourne July 20 to 25.
This article is part of our coverage of the 20th International AIDS Conference, to be held in Melbourne from July 20 to 25. Look out for more pieces in the following weeks and full coverage during the conference.
Edwina Wright receives funding from a research grant from NIH, a Career Development Fellowship from the National Health and Medical Research Council of Australia, research funding from the Victorian Department of Health and unrestricted research funds from Gilead, Abbott, Janssen Cilag and Boehringer Ingelheim. She has also received funding that has been used for research purposes only from ViiV, Merck, Gilead, and Abbott for consultancy work, payment for lectures from ViiV and payment for developing educational resources for ViiV and Gilead. The study drug for the VicPrEP study has been donated by Gilead Sciences.