Scientists cautiously optimistic about HIV vaccine candidate

Are we on the road to an HIV vaccine?Hide Caption

More than three decades after the identification of the human immunodeficiency virus (HIV), scientists are still working to develop a preventative vaccine that could finally put an end to the epidemic for which there are almost two million new infections each year.

"The challenges in the development of an HIV vaccine are unprecedented, and the ability to induce HIV-specific immune responses does not necessarily indicate that a vaccine will protect humans from HIV infection", he explains.

The study in monkeys took a similar approach to vaccination, but involved exposing the monkeys to HIV infection on a weekly basis for a period of 6 weeks to see if the vaccine was effective at preventing infection.

The new vaccine was tested in 393 healthy people considered at low risk for infection and 72 rhesus monkeys. Each year, around 2 million people are diagnosed with HIV.

According to the World Health Organization (WHO), about 40 million people around the world are HIV-positive, while about 2 million people are getting HIV, every year. Till date, this is the first out of five HIV vaccine concepts to have showed a positive response in nearly around 40 years of the HIV virus causing havoc among humans.

In both humans and monkeys, researchers found those who received the vaccine still showed signs of the vaccine in their immune system after a year. The vaccine containing "mosaic" HIV Env/Gag/Pol antigens was created from many HIV strains, delivered using a nonreplicating common-cold virus (Ad26).

The study selected participants from around the world, notably those from the United States, Thailand, South Africa, Uganda, and Rwanda. The experimental regimens tested in this study are based on "mosaic" vaccines that take pieces of different HIV viruses and combine them to elicit immune responses against a wide variety of HIV strains.

Barouch is the director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center as well as a professor of medicine at the Harvard Medical School.

Mild side effects were common, and around 1% of people in the trial had more serious adverse reactions to the vaccine. We do not have a licensed prophylactic, i.e., meant to prevent disease, HIV vaccine.

Barouch reminded that this is the "fifth HIV vaccine concept" that has been tested in the four decades of the advent of HIV.

"I can not emphasise how badly we need to have a get rid of HIV in the next generation altogether", said Francois Venter of the University of the Witwatersrand Reproductive Health and HIV Institute in South Africa.

It is still too early to speculate that it would work with 100 percent success say the researchers but they are hopeful.

"We have been here before, with promising candidate vaccines that haven't panned out", he told AFP.

Jean-Daniel Lelievre of France's Vaccine Research Institute said the vaccine was likely not the "definitive" version, but may represent "a phenomenal advance". "But the data is promising and we are happy to report the immune response". The mosaic is one of five vaccines to ever make it this far in the testing stages, but none of the previous vaccines were successful enough to make it to the next round of testing. It's unclear whether it would provide protection in humans.

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