New experimental HIV vaccine shows promise in early trials

A new HIV vaccine candidate has shown promise in its early clinical trials.

In a study published in the journal Cell, the vaccine successfully generated broadly neutralising antibodies (bnAbs) in a small sample of people.

Without getting too technical, bnAbs are antibodies that can recognise and fight off many different strains of HIV - which has been a major goal in the search for an effective HIV vaccine as they are difficult to generate in humans.

The new vaccine candidate DHVI was tested in a small clinical trial and shown to target HIV-1, the most common of the two types of HIV.

The trial showed that the vaccine was able to generate bnAbs in several people after two doses.

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Although it's a major step forward in developing an HIV vaccine, it's still early days to confirm anything as the safety and efficacy of the vaccine are yet to be determined.

For a vaccine to work, it must stimulate the production of antibodies that are primed to neutralise intruders.

But, for it to be safe, the vaccine has to achieve this response for the vast majority without any major side effects or reactions.

It's still progress though as, despite nearly four decades of research, the road to any kind of immunisation against HIV has been a long and tough one.

'The challenge has always been to recreate the necessary events in a shorter space of time using a vaccine,' said Wilton Williams, an immunologist at the Duke Human Vaccine Institute (DHVI) who led the study.

'It was very exciting to see that, with this vaccine molecule, we could actually get neutralizing antibodies to emerge within weeks.'

Initially, the phase I clinical trial began in 2019 and enrolled 24 healthy participants, 4 of whom received a placebo.

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But the trial came to a stop when one person suffered a severe allergic reaction to polyethylene glycol (PEG) - a stabilising ingredient - after their third dose.

Before the trial was halted, five people received three of the four planned doses, and another 15 people received two.

As a result, the vaccine has been reformulated to exclude PEG and so the trial will resume with a PEG-free version.

Interestingly, two people out of the former group produced the bnAbs, shown to neutralise between 15 to 35% of HIV strains in laboratory tests.

'This work is a major step forward as it shows the feasibility of inducing antibodies with immunizations that neutralize the most difficult strains of HIV,' added DHVI immunologist Barton Haynes.

'Our next steps are to induce more potent neutralizing antibodies against other sites on HIV to prevent virus escape.

'We are not there yet, but the way forward is now much clearer.'