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- Early research into a potential HIV vaccine shows promise according to study authors.
- The experimental vaccine candidate may be able to target part of the virus that remains essentially unchanged even as the virus mutates.
- Previous vaccine candidates have failed in part because the virus mutates so rapidly.
A Phase 1 study of a new experimental HIV vaccine is showing promising results among a small group of volunteers. The findings published this month in Science are showing that when a two-dose regimen of the vaccine is administered eight weeks apart, an immune response is triggered that may fight against HIV. Though it’s still early days in the testing process, this is a promising first step.
The vaccine, called eOD-GT8 60mer, was found to induce what are known as broadly neutralizing antibody precursors in the small group of volunteers. Broadly neutralizing antibodies is an approach that targets the core part of the virus, which remains unchanged even when a virus mutates. Among the participants, the vaccine induced the broadly neutralizing antibody precursor in 97% of the recipients.
“This is a case of a long journey beginning with first steps. We know that we do not have an effective vaccine against HIV and several previous attempts to create a vaccine have not been very successful,” said Dr. William Schaffner, professor of preventive medicine and health policy, and professor in the Division of Infectious Diseases at Vanderbilt University School of Medicine..
Previous vaccine candidates have failed in part because the virus mutates so rapidly.
“The current strategy and idea is because HIV mutates so much, on an hourly basis, it’s been very difficult to create an effective vaccine. Broadly neutralizing antibodies is the approach that gets to the core part of the virus, which is the part of the virus that doesn’t change,” said Dr. Jeffrey Klausner, clinical professor of population and public health sciences at the University of Southern California Keck School of Medicine. “This part of the virus is independent of these mutations.”
The start of the Phase 1 clinical trial began in 2018 and was designed to evaluate the safety of the experimental vaccine. During this phase, 48 adult volunteers were enrolled at George Washington University in Washington, D.C. and Fred Hutchinson Cancer Research Center in Seattle.
Eighteen of the participants received a 20-microgram dose of the vaccine and then a second dose eight weeks later. Another 18 of the participants received a 100-microgram dose and then the same eight weeks later. Finally, 12 participants received two doses of a saline placebo.
Following the first dose, the research found the recipients of the experimental vaccine had produced antibodies that could help protect against HIV infection. These antibodies then increased after the second dose.
“With any new intervention, whether it be medication or vaccines, the first hurdle is to determine if it’s safe. The second is to determine if it produces the intended biological effect,” said Klausner. “Then it has to go to the real clinical trials, which is the real hurdle. Will it protect people from getting HIV infected?”
It’s still too early to know.
The results are promising, but experts are remaining cautiously optimistic. The next step will be a Phase II investigation, which is like a Phase I study, only larger. Following a potentially successful Phase II study, then research would move to Phase III, which will determine whether or not the vaccine actually provides protection against the acquisition of HIV infection.
“We are not there yet by any means. We have a lot of stories and hope from vaccines in the past,” said Klausner. “Most of us in the field are cautiously optimistic. It’s promising, but it’s early days.”
Even though it’s still years away from anything definitive, should this vaccine be effective, it would be revolutionary.
“We’ve been trying to make a vaccine against HIV for 25 years and we’re still not there. It shows you what a hard job this is scientifically. Should it work, this could be of enormous importance not just in the developed world, but in the developing world,” said Schaffner. “We have medicine that can treat HIV and they are being used progressively around the world. But if we were able to prevent the infection on the front end, that would be so much more successful.”
“While we wait for an effective vaccine, we do have the highly effective prevention tools,” said Klausner. “We have oral medication, long-acting injectable medications, and condoms for some people are still a good way to protect themselves. There are other interventions available now on the table that people who think they may be at risk should use.”
It will be several years before this experimental vaccine could be offered, but experts watching are excited and encouraging the research to continue.
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