“Why finding an effective HIV vaccine remains a challenge after 40 years of research”

2023-05-20 05:04:40

On May 20, 1983, three French researchers discovered HIV. Forty years later, there is still no vaccine to eradicate the virus.

Will the world ever be able to turn the page on HIV? Since the discovery of the virus responsible for AIDS on May 20, 1983, scientists are still looking for an effective vaccine to overcome it. Because if in four decades, the daily life of patients has improved considerably thanks to triple therapies and PrEP, a preventive treatment that prevents HIV from entering the body, no effective vaccine has yet been found.

And “grand regret”explains Françoise Barré-Sinoussi, one of the researchers who discovered HIV and Nobel Prize in Medicine, in a video published by the Institut Pasteur on Tuesday. “I would have loved to leave this world thinking that HIV was eradicated.” This is still far from being the case: in 2021, the UN listed 38.4 million people living with the virus worldwide.

A virus with many mutations

How to explain that this quest is so tedious? First of all, HIV has a very strong capacity for mutation, which allows it to escape a possible vaccine. “The number of variants is incomparable with that of Sars-CoV-2 variants, it is much higher”explains Michaela Müller-Trutwin, head of the HIV unit at the Institut Pasteur in Transversala specialist magazine published by Sidaction. “A single infected patient can carry millions of different variants, more than the diversity generated during a global flu epidemic. However, the latter requires the development of a new vaccine each year”abounds Jean-Daniel Lelièvre, vaccination specialist and head of the infectious diseases department at the Henri-Mondor hospital in Créteil (Val-de-Marne), in The Conversation.

Unlike Sars-CoV-2 or other pathogens for which there is a vaccine, the human body is unable to produce antibodies on its own to neutralize HIV. It is therefore impossible to cure the disease naturally. The only three cases of remission identified so far concern people who have benefited from a bone marrow transplant. This specificity makes the task difficult for researchers, who must “Finding a parade to bring our immunity to mobilize its troops and still be able to fight HIV effectively, which takes time”, explains Jean-Daniel Lelièvre to Transversal.

However, during these years, many avenues have been explored. For example, in 2009, a preventive vaccine was tested. Although promising, it was only 30% effective, underlined Professor Yves Lévy, director of the vaccine research institute (VIR), with franceinfo, at the beginning of 2021. A clinical trial carried out in sub- safari by the Johnson & Johnson laboratory had been stopped the same year, for lack of conclusive results. Named Imbokodo, this vaccine had been tested from 2017 on around 2,600 young women in Malawi, Mozambique, Zambia, South Africa and Zimbabwe, where HIV is particularly common. The results had shown 25% efficacy, a lower result than for the vaccine tested in 2009.

A French vaccine candidate watched closely

These failures have allowed researchers to better understand the virus and develop a new strategy to fight it. In February 2023, the National AIDS Research Agency (ANRS) and Inserm published the very encouraging results of a French vaccine candidate, following a preliminary trial, known as “phase 1”, conducted on a sample of 36 healthy people. “The vaccine has shown both its safety and its ability to induce early, potent and long-lasting responses”welcomed Yves Lévy to from the ANRS.

In addition to the results, it is his strategy that is scrutinized by scientists. This preventive vaccine against HIV is indeed the first to rely on dendritic cells, these sentinel cells present throughout the body and capable of triggering an immune response. A mode of operation that has several advantages: “First, we target the right cells, then we choose fragments of the virus, in this case the HIV envelope that allows it to enter the body. Third advantage, we stimulate the dendritic cell, so immunity. Finally, as we are targeting the right fragments and the right cell, we do not need a large quantity of vaccine”, explained Professor Yves Lévy to franceinfo in February 2021.

Researchers remain cautious, however. “It’s a new strategy and we must therefore wait to see what it will give”, noted Jennifer Pasquier, scientific director of Sidaction, in March on France Inter. Also, tas it currently exists, this vaccine “is possibly not” that’s why I wrote to you “which will protect us against infection. The type of protein that has been applied may not be the optimal one for an HIV vaccine”nuanced at the same time Jean-Daniel Lelièvre, with Release (article reserved for subscribers). Because for the time being, the preparation tested has only been tested on one isolate (group) of the virus. After this first step, “observations will have to be extended with other HIV isolates to see if the antibodies produced have a broad-spectrum neutralizing power”, always explain ReleaseOlivier Schwartz, director of the virus and immunity unit at the Institut Pasteur.

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