26 November 2013

A HIV vaccine preventing healthy cells’ infection

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Scientists are testing a new HIV vaccine candidate aiming at blocking the virus from entering the body, but it is still early days

AIDS research has attempted many strategies to tackle the HIV virus infection. Now, a new type of vaccine developed within an EU-funded project, called EuroNeut-41, is based on one of the envelope proteins of the HIV virus, called the gp41 protein. What makes it interesting it that it is directly responsible for the fusion of the HIV virus into human cells. By integrating the gp41 protein into the vaccine, researchers try to trigger the production of antibodies that would block the entrance of HIV into human cells.

“We have used an innovative approach, combining protein engineering, specific vaccine formulation and a combination of routes of administration, [nasal] and intramuscular,” explains Nicolas Mouz, chief scientific officer at PX'Therapeutics, one of the project partners. The company is also providing services, in protein engineering research and manufacturing and it is located in Grenoble, France.

There have been many trials since the discovery of the virus, in the early 1980s, to create both a cure for infected people and a preventative therapy to stop the contagion. “This gp41 protein from the virus envelope is not an absolute novelty in the long history of anti HIV vaccine development,” says Alexandru Rafila, Chairman of the Romanian Society for Microbiology in Bucharest. “But it is a meaningful approach in protein design that could be given as a vaccine so that it triggers an immune response.”

The trouble is that the virus targets not only the lymphocyte cells, which include T cells—a key component of the body's immune system helping to fight diseases—but also other immune system cells. The latter are not exclusively infected through the gp41 protein but also through other mechanisms. “An efficient vaccine should hamper the infection of any other cells,” Rafila tells youris.com.

Other experts concur that the diversity of HIV and its enormous capacity to mutate are major challenges for vaccine development. “The idea basically is that a vaccine should induce an immune response (antibodies or T cells), that would neutralise HIV in all of its forms,” says Ulrich Fruth, team leader for vaccine development and evaluation at the World Health Organisation, in Geneva, Switzerland.

Even though Fruth considers the project strategy a viable approach, chances of success for this vaccine are difficult to predict. “We just don’t know,” he says, “The animal models we have are not very predictive. We absolutely need human clinical trial in order to decide which vaccine to take forward.” The vaccine is in its first stage of clinical safety studies, which are not designed to demonstrate a protective effect. It is still too early to draw conclusions.

In addition, Fruth points to a minor limitation of this vaccine, namely that it focuses primarily on the induction of antibodies. He says: “we think that for a successful protection we may need to target both arms of the adaptive immune system: antibodies and T cells. In that context, rather than a stand-alone, I could see a role for such a vaccine as part of a combination vaccine with components that induce T cell immune responses".

Image: an HIV-infected H9 T cell
Image credits to: NIAID

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