Riding On Simian Success, New Vaccine To Treat HIV

Riding on the success of a vaccine tested on simians, scientists have expressed hope of testing its human equivalent in next two years to treat the HIV infection.

A research published in the journal, Nature has shown that in monkeys who were intentionally infected with Simian Immunodeficiency Virus (SIV), the new vaccine not only cleared the infection but also kept the animals virus-free for up to three years.

“50% of rhesus macaques vaccinated with SIV protein-expressing rhesus cytomegalovirus (RhCMV/SIV) vectors manifest durable, aviraemic control of infection with the highly pathogenic strain SIVmac239,” the study says.

Efforts to develop HIV vaccine have so far failed and scientists have only managed to produce medications that can keep HIV in check for long periods of time. After these results, however, the US scientists say they now want to use a similar approach to test a vaccine for HIV in humans.

“In order to make a human version we have to make sure it is absolutely safe,” said Louis Picker, an immunologist at Oregon Health and Science University who helped design the vaccine.

During the tests, the research team tried to treat an aggressive form of the virus known as SIVmac239 – up to 100 times more deadly than HIV.

The scientists said that the infected monkeys usually within two years, but in some inoculated primates, surprisingly, the virus didn’t even take hold.

Based on another virus, cytomegalovirus (CMV) that belongs to the herpes family, the vaccine used its infectious power to sweep throughout the body.

And instead of causing disease, it has been modified to spur the immune system into action to fight off the SIV molecules.

“It maintains an armed force, that patrols all the tissues of the body, all the time, indefinitely,” explained Prof Picker.

About two months after giving them the vaccine, the rhesus macaque monkeys were exposed to the SIV. After it was established, the infection began to spread in the monkeys, but soon their bodies began to respond by searching and destroying all signs of the deadly virus.

To their amazement, the researchers found that the monkeys who successfully responded to the vaccine were still free from the infection between one-and-a-half and three years later.

What, however, is a cause of concern for the researchers, is why the vaccination worked in only about half of the monkeys. On this, Prof Picker says that his team is trying to figure it out.

The results have nonetheless offered fresh hopes of curing the deadly HIV virus in humans. This vaccine, Prof Pickers says, would first have to pass through the regulatory authorities. “If it does we hope to start the first clinical trials in humans in the next two years,” he says.

“We have now engineered a CMV virus which generates the same immune response but has been attenuated [modified to lose its virulence] to the point where we think it is unequivocally safe.”

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