HIV vaccine test works on monkeys, says new study | Science and health

The new study shows that rhesus monkeys can be stimulated to produce neutralizing antibodies to an HIV strain resembling the resistant viral form that most commonly infects humans, known as the Tier 2 virus. The survey provides also the first estimate of neutralizing antibody levels required by the vaccine to protect against HIV.

• "We found that immunizing antibodies induced by vaccination can protect animals from viruses that are very much like HIV in the real world," says Dennis Burton, chair of Scripps Research's Department of Immunology and Microbiology. International AIDS Vaccine Initiative (IAVI).

Although the vaccine is far from human clinical trials, the study provides a proof of concept for the HIV vaccination strategy developed by Burton and his colleagues since the 1990s.

The purpose of this study The strategy is to identify rare and vulnerable areas of HIV and teach the immune system to produce antibodies to attack these areas. Studies by Scripps Research scientists have shown that the body needs to produce neutralizing antibodies binding to protein trimer from the external envelope of the virus.

To support this idea, scientists have discovered that they can protect animal models of HIV by injecting them with neutralizing antibodies produced in the laboratory.

The Development of the Vaccine

The challenge was to force the animals to produce their own neutralizing antibodies. To do this, scientists had to expose the immune system to the trimer of the envelope proteins and effectively train it to identify that target and produce the appropriate antibodies against it.

But there was a big problem. The trimer of the HIV envelope is unstable and tends to collapse when isolated. How could scientists use it as an ingredient in a vaccine? A breakthrough occurred in 2013 when scientists genetically developed a more stable trimer, or SOSIP.

"For the first time, we had a device that looked a lot like the trimer of the HIV envelope protein," says Matthias Pauthner, an badociate researcher at Scripps Research and co-author of the new study.

Scientists quickly developed an experimental HIV vaccine containing this stable SOSIP trimer. His goal with the new study was to see if this type of vaccine could actually protect animals from infection.

The team tested the vaccine on two groups of rhesus monkeys. An earlier study using the same vaccine had shown that some naturally immunized monkeys developed low levels of antibodies in their bodies, while others developed high levels after vaccination.

From this study, researchers selected and revaccinated six low-level monkeys and six high-level monkeys. They also studied 12 non-immunized primates as a control group.

Primates were then exposed to a form of the virus called SHIV, an artificial version of HIV containing the same trimer envelope as the human virus.

This particular strain of the virus is known as the Tier 2 virus because it has proved difficult to neutralize as well as the circulating forms of HIV in the human population.

The researchers found that vaccination was effective in animals at high levels. Monkeys were able to produce sufficient levels of neutralizing antibodies directed against the trimer of the envelope protein to prevent infection.

"Since HIV emerged, this is the first evidence that we have antibody-based protection against a Tier 2 virus after vaccination." One question now is how to achieve these high levels in all animals? "- Matthias Pauthner, Scripps Research Associate Researcher and co-author of the study

It became particularly important to focus on antibody levels as researchers found that HIV protection decreased over the course of weeks and following months of vaccination: By following the levels while continuously exposing animals to the virus, the researchers determined the levels of antibodies needed to control HIV.

It is important to note that the 39; study also showed that the presence of neutralizing antibodies, but not other aspects of the immune system, was the key to stop the virus. According to Pauthner, it is a important discovery because other laboratories have focused on the potential of T cells and other immune system defense systems to block infections.

In the future, scientists will search to improve the design of vaccines for human testing and to maintain high levels of antibodies. "There are many immune tricks that can be explored to make immunity more sustainable," said Pauthner.