A Phase I human study using a vaccine called MVA-B has achieved an immunological response in 92% of healthy volunteers against HIV, with 85% of them maintaining immunity for at least 12 months. Researchers from the Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Gregorio Marañón Hospital, Madrid and Clínic Hospital, Barcelona, reported the results of the trial in the journals Vaccine and Journal of Virology.

If further trials go according to plan, the scientists believe they may well have a vaccine that could turn HIV into a minor chronic infection, similar to herpes, which would only be a problem for people with compromised immune systems.

The researchers explain that the vaccine’s success is based on the human immune system’s ability to learn how to react against virus particles and infected cells over time.

Lead researcher, Mariano Esteban, said:

“MVA‐B vaccine has proven to be as powerful as any other vaccine currently being studied, or even more.”

Animal studies (mice and macaque monkeys) in 2008 demonstrated MVA-B’s efficacy against SIV (simian immunodeficiency virus).

The authors wrote that the latest trial’s success means they will move on to testing it on HIV infected participants. The trial only used healthy volunteers – people without HIV infection.

In 1999, Mariano Esteban and team started R&D and preclinical studies on a vaccine based on the Modified Ankara Vaccinia virus. MVA-B is an attenuated virus (its virulence has been reduced) that had already been utilized to eradicate smallpox. It had also been used as a model in other vaccine research. The “B” in MVA-B stands for the subtype of HIV the vaccine is designed to work against – the most common subtype in the European continent.

The vaccine contains four HIV genes in Vaccina’s genetic sequence – Gag, Pol, Nef and Env. These genes stimulate T and B lymphocytes. Lymphocytes are small white blood cells that play an important role in the body’s immune system. The authors stress that the inserted genes cannot self-replicate.

This double-blind Phase I trial involved 30 healthy volunteers. 24 received the MVA-B vaccine, and the other 6 received a placebo. The participants were given an injection on day one, week 4 and week 16. Their blood was tested regularly up to week 48.

The aim of the vaccine it to train the body’s immune system to identify and learn how to fight and destroy the virus’ components.

Esteban said:

“It is like showing a picture of the HIV so that it is able to recognize it if it sees it again in the future. Our body is full of lymphocytes, each of them programmed to fight against a different pathogen. Training is needed when it involves a pathogen, like the HIV one, which cannot be naturally defeated.”

T cells seek out and destroy infected cells. B cells release antibodies which target viruses before they infect a cell. Nearly three-quarters of the volunteers developed HIV-specific antibodies 11 months after receiving the vaccine. More than one third of them developed CD4+, a type of T cell that fights HIV, while more than two-thirds developed CD8+. 92% of them developed some kind of immunity. This does not necessarily mean they were all protected from HIV infection.

The researchers stressed that they are still in the early stages of the vaccine.

Esteban said:

“MVA‐B immune profile meets, initially, the requirements for a promising HIV vaccine”. MVA‐B is not capable of removing the virus from the body as once a cell is infected, virus’ genetic data is integrated and replicated with the cell.

However, the immune response induced by the vaccine could keep the virus under control, “if the virus enters the body and tries to develop in a cell, the immune system is ready to inactivate the virus and destroy the infected cell.”

The researcher’s wrote:

“If this genetic cocktail passes Phase II and Phase III future clinic trials, and makes it into production, in the future HIV could be compared to herpes virus nowadays.”

They added that if the vaccine does what they think it will do, the virus would no longer cause disease – it would become a minor chronic infection.

Written by Christian Nordqvist