This is a guest blog by Jeffrey T. Safrit, Ph.D, director of Clinical and Basic Research for the Elizabeth Glaser Pediatric AIDS Foundation. It was co-published on the Foundation’s own blog.
LOS ANGELES — In advance of the largest global HIV/AIDS conference of the year this week in Rome, there have already been several breaking news stories and research updates about HIV prevention.
Three of these stories, including preventing HIV transmission through breastfeeding, preventing sexual transmission through the use of antiretroviral drugs and HIV vaccine research, are what we’re reading this week.
The Foundation’s Vice President for Research, Dr. Laura Guay, wrote an editorial reviewing the state of the field in prevention of mother-to-child transmission of HIV (PMTCT) that was just published in the Journal of AIDS. The article focuses on efforts to prevent breastfeeding transmission, and specifically on the full results of the PEPI-Malawi breastfeeding study also published in the same volume of JAIDS.
The PEPI-Malawi study showed that extending daily doses of the antiretroviral (ARV) drug nevirapine to the HIV-exposed infant for the first six months of breastfeeding was safe and effective at reducing HIV infection. Importantly, the study also showed that when the drug is stopped after six months and breastfeeding continues, the risk of transmission of HIV during the continued breastfeeding period is still significant. The results would suggest that, per the World Health Organization’s (WHO) most recent guidelines, the use of ARV drugs for prevention (known as prophylaxis) to the infant or mother should continue throughout the duration of breastfeeding, which can be up to two years.
Also this week, the results of two recent clinical trials of pre-exposure prophylaxis (PrEP) were released with much fanfare. PrEP refers to the much discussed effort to prevent HIV infection in high risk individuals by taking a pill a day, before exposure to HIV has even occurred.
Previously, two separate trials for PrEP showed dramatically different results. The first, in men who have sex with men (MSM), showed that taking a pill a day to prevent infection was significantly effective. The second trial in women at risk for heterosexual transmission in Africa was stopped early because there was no observed benefit. These were perplexing results to say the least.
This week, however, the two new studies showed a significant reduction in heterosexual transmission of HIV in Africa by using daily doses of the drugs Tenofovir or Truvada (tenofiovir + emtricitabine). These studies on PrEP showed a reduction of new HIV infections by more than 60%. While the reasons for the differences between these latest results and the previous studies are not known, regular adherence to the daily drug regimen may have played a role.
These results follow the dramatic ‘treatment as prevention’ results from last month, where the HPTN 052 study showed an amazing 96% reduction in transmission in couples where only one partner was HIV-positive, known as HIV discordant couples. The results were best when the HIV-positive partner was treated early. Imagine if this trial had combined treatment of the infected partner with daily dosing of the uninfected partner!
So, not only can we prevent mother-to-child transmission of HIV through ARVs, but now we can significantly prevent transmission of the virus between adults using a similar technique, both by treating the infected partner as well as the uninfected high-risk individual.
Before we think that results like these mean that the HIV epidemic could soon be over, let us think about what the studies mean for the long term. The common thread of all of these efforts is antiretroviral drugs. Considering the significant challenges providing ARVs to those already HIV-positive and in need of therapy, the thought that we can immediately scale up treatment to all those who need it – PLUS those who do not yet qualify for treatment based on current WHO guidelines – AND their uninfected partners or those at high risk of infection – is simply not yet realistic.
What is clear, however, is that prevention can and does work. What is also clear is that combinations of prevention techniques will most likely be necessary to end the scourge of HIV. Combinations of PMTCT, PrEP, circumcision, and a possible vaccine will move us towards that goal.
And finally, speaking of vaccines, we continue to learn more about what may be necessary to create a successful HIV vaccine. Just last week, a study was published by Michel Nussenzweig and colleagues at Rockefeller University in New York that has uncovered additional highly potent antibodies against the virus. These antibodies, derived from HIV-infected individuals whose immune systems are controlling their infections, add more evidence to our understanding of the natural immune response to HIV.
It is even possible that the antibodies could be developed into drugs used to treat or prevent HIV infection.
Just another potential tool in our growing HIV prevention arsenal.