An HIV vaccine may have helped five study participants keep their virus in check without antiretroviral therapy (ART). One has been off ART for seven months.
While the findings need to be confirmed with larger studies, they suggest that the vaccine strategy could boost the immune system enough to control HIV levels without drugs.
“It’s the proof of concept that through therapeutic vaccination we can really re-educate our T cells to control the virus,” said Dr. Beatriz Mothe, a clinician at IrsiCaixa AIDS Research Institute in Barcelona, Spain. She presented the results at the Conference on Retroviruses and Opportunistic Infections (CROI) last month in Seattle. “This is the first time that we see this is possible in humans.”
Previous “treatment interruption studies” in people who started antiretroviral drugs soon after becoming infected have found that only 10% control their infections for longer than four weeks, according to Mothe. In the current study, she noted that 38% of those who were vaccinated passed that milestone.
This study involved 13 participants who had taken antiretrovirals for an average of 3.2 years. All had started treatment within six months following infection and had undetectable virus levels at the beginning of the study.
The strategy involved administering the MVA.HIVconsv vaccine developed by Tomas Hanke of the University of Oxford. A previous trial found the vaccine demonstrated promising potency. The patients were then given three weekly doses of romidepsin, a cancer drug that can activate hidden reservoirs. That was followed by a second MVA.HIVconsv vaccination.
After receiving the shots, the participants stopped ART. Within four weeks, eight participants experienced HIV rebound and had to resume the drugs. The other five, however, have now gone between six and 28 weeks without restarting ART. The virus became temporarily detectable in each of them at various time points, but the “blips” never went above 2,000 copies/mL, the criterion for restarting treatment.
Commenting on the study in Science magazine, Dr. Steven Deeks, a lead investigator at the amfAR Institute for HIV Cure Research at the University of California, San Francisco, said of the more than 50 therapeutic vaccine trials so far, this is the first one that has boosted the immune system in a “meaningful” way. He told the publication he was “cautiously optimistic” that the results will encourage others to explore the approach.
Mothe and colleagues intend to monitor the participants to find ways to improve the outcome in future studies.