First ‘promising’ results of mRNA vaccine

“A promising approach. A vaccine that uses messenger RNA technology, like some vaccines against Covid-19, but this time against AIDS, has shown promising initial results in animals. The vaccine was proven to be safe when administered to macaques, and the risk of infection from exposure was reduced by 79%. However, it calls for improvements before they can be tested in humans.

“Despite nearly four decades of efforts by the global scientific community, finding an effective vaccine to prevent HIV remains a distant goal,” according to immunologist Anthony Fauci, co-author of the study (published Thursday in the review). temper nature) as well as the White House adviser on the health crisis. “This experimental mRNA vaccine combines several features that could overcome the failures of other experimental HIV vaccines, and therefore represents a promising approach,” added the director of the US National Institute of Allergy and Infectious Diseases (NIAD).

Scientists from this institute conducted this work in collaboration with researchers from the American company Moderna, which is behind one of the most widely used vaccines against Covid-19.

How did the experience go?

The vaccine was first tested on mice and then on rhesus macaques. These received multiple stimulant doses over one year. Despite the high doses of the mRNA, the product was well tolerated causing moderate side effects, such as temporary loss of appetite.

By week 58, all macaques had developed detectable levels of antibodies. Starting from the 60th week the animals were exposed every week to the virus via the rectal mucosa. Because primates are not susceptible to HIV-1, which infects humans, the researchers used a different but similar virus, simian HIV virus (SHIV). After 13 weeks, only two of the seven vaccinated macaques were uninfected. But while other unvaccinated macaques fell ill after about three weeks, those who were vaccinated took an average of eight weeks. “This level of risk reduction can have a significant impact on transmission of the virus,” the study said.

Relatively low antibody levels

The vaccine works by delivering genetic instructions to the body, which leads to the formation of two types of proteins characteristic of the virus. They are then aggregated to form viral pseudopodia (VLPs), mimicking infection in order to provoke an immune system response.

The scientists noted, however, that the levels of obtained antibodies were relatively low, and that a vaccine requiring multiple injections would be difficult to implement in humans. They therefore wish to improve the quality and quantity of VLPs generated before testing the vaccine in humans.