Researchers from the National Institute of Health's National Institute of Allergy and Infectious Diseases and Emory University have shown that sustained HIV remission is possible in rhesus macaque monkeys.
By supplementing antiretroviral medication with an antibody during treatment, as well as after, the researchers were able to keep simian immunodeficiency virus (HIV's form in primates) from re-emerging and causing disease once administration of antiretroviral drugs was stopped. This is the first time that immune control post-treatment was demonstrated consistently in SIV-positive monkeys that have not been previously vaccinated.
In a study published in the journal Science, it was reported that that SIV was still present in the bodies of the subjects but viral levels stayed below what is detectable in the blood, even after nearly two years since antiretroviral drug administration ceased.
The antibody the researchers used is called vedolizumab. An analogous human antibody, it has been approved by the U.S. Food and Drug Administration in 2014 for treating ulcerative colitis and Crohn's disease, designed to keep susceptible immune cells from entering tissues in the intestines, which is an area prone to damage during HIV and SIV infections.
NIAID has already started a clinical trial to assess how safe vedolizumab is and how it will affect HIV-positive individuals after the current study yielded positive results regarding the antibody.
Aftab Ansari, Ph.D., the study's senior author, explained that the idea to use an antibody to address HIV came about years ago, saying the circulation of CD4+ T cells may be stopped to offer protection when acute infections are in place. It's not clear how this prevented viral replication but it appears that antibody therapy aided in reconstituting the subjects' immune system, which helped keep SIV at bay.
"This finding could become a blueprint for an alternative therapy for HIV, which could make it so someone would not need to continuously take antiretroviral drugs," Ansari said.
"If we could figure out how the antibody works, then an effective HIV vaccine could be modeled on that mechanism," he added.
To this end, further research into antibody treatment need to be carried out. For starters, the researchers are planning additional experiments to identify which parts of the monkeys' immune systems had the biggest role in controlling SIV when antiretroviral drug treatment was stopped.
The researchers also observed that subjects that underwent antibody treatment had increased levels retinoic acid, a vitamin A derivative. It may be possible then to look at biomarkers as a means of predicting when an immune system is well enough to stop receiving antiretrovirals.
