After 40 years of research on AIDS, where is the search for a vaccine?

published on Monday 07 June 2021 at 18:21

Four decades of AIDS research have enabled researchers around the world to make immense strides, turning what was long a death sentence into a disease that we can live with on a daily basis.

But despite these advances, HIV (human immunodeficiency virus), which causes AIDS like SARS-CoV-2 causes Covid-19, still does not have a vaccine to fight infection before. that the disease does not set in.

Here is an overview of the quest for the Grail in the fight against this virus which affects 38 million people around the world.

– Why a vaccine? –

Access to antiretroviral drugs, which help limit the viral load in the body of infected people and keep them healthy, has become widespread. They also help prevent the transmission of HIV to their partners.

People who have a high risk of infection can also take so-called pre-exposure prophylaxis (PrEP), a pill taken daily that reduces the risk of infection by 99%.

“But access to drugs is not organized everywhere in the world,” Hanneke Schuitemaker, director of vaccine discovery at Johnson & Johnson (J&J), told AFP.

Even developed countries have vast socio-economic and racial disparities in access to these treatments, and vaccines have historically been the most effective tools for eradicating infectious diseases.

J&J is currently conducting two human clinical trials for its candidate vaccine, and the first results from one of them could fall as soon as “the end of this year”, says Hanneke Schuitemaker.

– Why is it so difficult to develop? –

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Vaccines against Covid-19, developed in record time while demonstrating remarkable efficacy and safety, have made it possible to dramatically reduce contamination in countries with access to enough doses.

Many of these remedies make use of technologies that were first tested on HIV. Why haven’t they worked against AIDS so far?

“The human immune system does not heal itself against HIV, while it has been very clear that it could be cured quite well from Covid-19”, details to AFP Larry Corey, principal researcher of the HIV vaccine trials network (HVTN), an organization funding the development of HIV vaccines worldwide.

Covid-19 vaccines work by causing antibodies to be made that attach to the virus’s spike protein and prevent it from infecting human cells.

HIV also has spike-like proteins, but while we only know a few dozen well-identified variants of Covid-19, HIV displays hundreds, even thousands of variants in each infected person, tells AFP William Schief, immunologist leading the development of an HIV messenger RNA vaccine at the Scripps Research Institute.

HIV, a “retrovirus”, integrates into the DNA of its host. To be effective, the vaccine must therefore stop the infection altogether, not just reduce the amount of virus leaving the virus in the body.

– Where is the research? –

Decades of attempts to develop an HIV vaccine have so far been unsuccessful.

The only vaccine candidate to have ever provided protection against the virus was deemed too ineffective last year in a clinical trial called “Uhambo”, held in South Africa.

J & J’s is currently being tested with 2,600 women from sub-Saharan Africa, and the first results of this trial, “Imbokodo”, should be known in the coming months.

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The effectiveness of this remedy is also evaluated in the trial “Mosaico” in 3,800 men who have sex with other men or transgender people, in the United States, in South America and in Europe.

Johnson & Johnson’s vaccine against HIV uses the same technology as that against Covid-19, that of the “viral vector”: a very common type of virus called adenovirus is modified to transport genetic information in the body to fight the target virus, in this case producing molecules capable of eliciting an immune response to a broad spectrum of HIV strains.

The boosters of this vaccine then directly include synthetic proteins.

Another promising approach is to generate “broad spectrum neutralizing antibodies”, which attach to areas that many HIV variants have in common.

The International AIDS Vaccine Initiative and the Scripps Research Institute recently published the results of a preliminary stage of a trial showing that their vaccine candidate stimulates the production of rare immune cells, which make just this type of antibody.

They hope to be able to take the next step in their vaccine development using messenger RNA technology, in partnership with Moderna.

This remedy aims, via several doses, to “educate” little by little the B lymphocytes, which produce the antibodies. The researchers also hope to form other lymphocytes, the “T”, to eliminate the cells which would have been infected after all.

This vaccine candidate is still far from being able to claim a clinical trial in due form, but William Schief says he hopes that the serum, which turns cells into vaccine factories and whose technology has been proven against Covid-19 make a difference against HIV.

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