Experimental HIV Vaccine Induces Potent Antibodies in Humans

For a vaccine to be effective, it must stimulate the production of antibodies in those immunized, which are ready to neutralize future infections. To be considered safe, it should achieve this in most individuals without causing significant side effects or adverse reactions.

A new HIV vaccine candidate is navigating familiar challenges in early-stage clinical trials, achieving success in one area while encountering obstacles in another. Despite these hurdles, progress has been made. Developers have reformulated the vaccine to enhance its safety for future studies, and recent results show that the vaccine successfully generates broadly neutralizing antibodies (bnAbs) in a small number of participants.

Challenges in Generating Broadly Neutralizing Antibodies

Broadly neutralizing antibodies, which can recognize and neutralize multiple HIV strains, were first discovered in some people with HIV during the early 1990s HIV/AIDS epidemic. Their potential was immediately clear, but creating a vaccine that can generate bnAbs in humans has remained elusive despite decades of research. Only 10 to 25 percent of people with HIV naturally develop bnAbs, and it can take years.

Therefore, the news that a vaccine candidate induced bnAbs in several individuals after two doses in a small clinical trial is promising. “It was very exciting to see that, with this vaccine molecule, we could actually get neutralizing antibodies to emerge within weeks,” says Wilton Williams, an immunologist at the Duke Human Vaccine Institute (DHVI) who led the study.

Vaccine Targeting HIV-1’s Stable Envelope Enters Phase I Clinical Trial

The vaccine targets HIV-1, the most common type of HIV, focusing on a stable part of its outer envelope. The phase I clinical trial, which started in 2019, included 24 healthy participants, four of whom received a placebo.

The trial stopped after one person had a severe allergic reaction to polyethylene glycol (PEG), used to stabilize the vaccine. Before the halt, five people received three of the four planned doses, and another 15 received two.

The vaccine was reformulated without PEG to resume the trial. Analysis showed a strong immune response after two doses. Two of the five people who received three doses before the trial halted generated bnAbs. The most potent antibodies neutralized 15 to 35 percent of HIV strains in cell experiments.

Advancing HIV Vaccines

“This work is a significant advancement as it demonstrates the potential of inducing antibodies through immunization that can neutralize the toughest strains of HIV,” says DHVI immunologist Barton Haynes.

“Our next steps are to generate more potent neutralizing antibodies targeting different sites on HIV to prevent the virus from escaping. We’re not there yet, but the path forward is now much clearer.”

While still in the early stages, having options is encouraging. Other promising strategies for developing vaccines effective against various HIV strains have failed in late-stage clinical trials, highlighting the immense challenges in creating an HIV vaccine.

While potential vaccines face setbacks, other treatments are making strides. In December 2023, a groundbreaking trial demonstrated that preventive therapy reduced the likelihood of individuals contracting HIV by 86 percent with consistent use.

Read the original article on: Science Alert

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