Decades after the start of the HIV / AIDS pandemic, researchers have yet to find an effective formula for a vaccine. But now that we have eight COVID vaccines in 18 months, people are asking: can we speed things up for HIV?

This is research that has eluded scientists for 40 years so far: to find a safe and effective vaccine to protect people against HIV. Not a single HIV vaccine has passed Phase III clinical testing in 37 years of research. Compared to COVID-19, this timeline seems baffling. Over the past 18 months, more than 32 COVID vaccines have moved into Phase III clinical trials, eight have so far been approved and manufactured, and another 90 are in Phase I and II.

“When there is political will, there is funding and resources,” said Hendrik Streeck, virologist and director of the German Center for HIV and AIDS. “And that means it’s possible to be much faster,” he said. DW.

Two “completely different” viruses

Although HIV vaccine researchers have so far failed, it is not for lack of trying. More than 400 HIV vaccine candidates have been tested in Phase I clinical trials, although only five large-scale Phase III trials have been completed, each at a cost of over $ 100 million.

The world may have firmly turned its attention – and its funds – to finding a vaccine for COVID-19 since the outbreak began in December 2019, but the difference in those timelines isn’t just about politics. and money, Streeck said. It also has to do with the unique makeup of the two viruses.

“SARS-CoV-2 [the virus causing COVID] and HIV cannot be compared in terms of structure and complexity, ”said Streeck DW. The human immunosuppressive virus (HIV) is “a completely different virus,” he said.

Unlike SARS-CoV-2, which is a very stable virus, the human immunosuppressive virus (HIV) is extremely variable – it is constantly changing. This makes it very difficult for the immune system of people infected with HIV to make the right antibodies to repel the virus, as this is usually one step ahead of any body response. Thousands and thousands of strains of HIV circulate in the world’s population. The HIV genome also integrates into the body’s DNA, effectively making itself invisible to the immune system.

These characteristics mean that our bodies generally do not develop an effective immune response to HIV. They also make it very difficult to design a widely effective vaccine.

Most vaccines work by stimulating “neutralizing antibodies,” which are proteins that attack unwanted invaders in the body. But when the target of this attack is constantly changing in appearance, it is very difficult to capture.

“Science and the world have been very lucky that SARS-CoV-2 was an easy target for vaccines,” said Jonathan Weber, dean of medicine at Imperial College London and longtime HIV researcher . All of the methods that vaccine developers have tested to make a COVID vaccine – including the viral vector, mRNA, and adenovirus – “all worked,” Weber said.

“With HIV, the opposite is true. We have tried all of these different techniques and none has protected against HIV effectively,” he said.

HIV vaccine trials also tend to take much longer because, while researchers want to test whether the vaccines they are developing can prevent people from becoming infected with HIV, they are also actively helping to prevent HIV infection. prevent infections with pre-exposure prophylaxis (PrEP).

HIV vaccines in progress

To date, only one vaccine against HIV, called Uhambo, has shown partial protection in human trials, but it has not been effective in a recent large-scale trial in South Africa. Two other large trials, called PrEPVacc and Mosaico are currently underway. Both use a combined approach to vaccination.

Mosaico is based on an adenovirus vaccine followed by a booster that contains a “mosaic” of proteins from several strains of HIV. This is similar to the Johnson and Johnson, Oxford-AstraZeneca, and Russian Sputnik COVID-19 vaccines.

Streeck, whose research team is involved in supporting the Mosaico trial in Europe and North and South America, says researchers are “cautiously optimistic” after vaccine shows promising results in tests about animals. The researchers expect to have results within the next month.

PrepVacc uses HIV DNA, a live viral vector and protein. Researchers in the African-led, European-backed trial project plan to enroll around 2,000 HIV-negative volunteers.

Weber’s team is leading the trial, which is currently being conducted in South Africa, Tanzania and Uganda. Although it started in 2018, progress has been “massively delayed by COVID,” he said, and, so far, only around 300 participants have been enrolled. “We believe that we will have to carry out this study until the beginning of 2024 to obtain reliable results on the effectiveness of the vaccine,” Weber said. DW.

Meanwhile, vaccine giant Moderna is working on two possibilities for an HIV mRNA vaccine. The first, called mRNA-1644, is expected to begin Phase I trials in late 2021. The second, known as mRNA-1574, is being researched in collaboration with the National Institutes of Health (NIH) in the States. -United. Researchers working on this second type of mRNA vaccine have so far seen promising results in monkeys, said Peng Zhang, an immunologist at the National Health Institute in the United States.

“The preliminary results were very exciting. We tested different strains from different regions, South Africa, Asia and America, and they were all neutralized by the monkeys receiving the vaccine,” he said. declared. DW. The mRNA approach has been used by Moderna and BioNTech-Pfizer for their COVID-19 vaccines.

While mRNA vaccines have so far proven to be extremely effective against SARS-CoV-2, Weber warns that it is too early to hail them as the next big breakthrough in HIV vaccine research.

“My point at this point before I saw any data is that we still have the problem [with mRNA vaccines] that we don’t have the optimal antigen for HIV, ”he said.

“We have to use this momentum”

Despite the hurdles, Weber is confident that scientists will eventually decipher the formula to find a safe and effective HIV vaccine. “I have made my whole career thinking we would get an HIV vaccine. I am not giving up on this – I just hope I can live to see it,” he said.

Over the past 40 years, more than 35 million people have died of HIV / AIDS. And according to Streeck, it is a pandemic “that we are far from controlling”.

“Most of those infected die from this disease,” he said. “There is momentum in the world right now. We must use this momentum to end HIV and AIDS. “



Source link

Leave a Reply

Your email address will not be published.