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HIV-like virus in monkey cured by experimental vaccine

By Catholic Online (NEWS CONSORTIUM)
September 12th, 2013
Catholic Online (www.catholic.org)

A vaccine for the primate equivalent of HIV appears to eradicate the virus, a study suggests. Sixteen monkeys infected with Simian Immunodeficiency Virus, or SIV were given a vaccine. Nine of the 16 test subjects responded favorably. Scientists in the United States say they now want to use a similar approach to test a vaccine for HIV in humans.

LOS ANGELES, CA (Catholic Online) - "It's always tough to claim eradication - there could always be a cell which we didn't analyze that has the virus in it," Professor Louis Picker, from the Vaccine and Gene Therapy Institute at Oregon Health and Science University, says. 

"But for the most part, with very stringent criteria... there was no virus left in the body of these monkeys."

Picker and his colleagues looked at an aggressive form of virus called SIVmac239, up to 100 times more deadly than HIV. Monkeys with SIV usually die within two years. However - in some inoculated primates, the virus did not take hold.

The vaccine is based on another virus called cytomegalovirus, or CMV, which belongs to the herpes family. The infectious power of CMV sweeps through the body. Instead of causing disease, CMV 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," Picker explains.

In the study, researchers gave rhesus macaque monkeys the vaccine, and then exposed them to SIV. The infection at first began to establish and spread. In time, the monkeys' bodies began to respond, and sought out and destroying all signs of the virus.

Of the test subject monkeys that successfully responded to the vaccine, all were clear of infection between one-and-a-half to three years later.

A mystery remains: Picker said his team was still trying to work out why the vaccination worked in only about half of the monkeys. "It could be the fact that SIV is so pathogenic that this is the best you are ever going to get.

"There is a battle going on, and half the time the vaccine wins and half the time it doesn't," he said.

In regards to application to human beings, researchers are now testing the vaccine to see if it can be used after SIV exposure to treat and perhaps cure infected monkeys - as a step to testing it on humans.

"In order to make a human version we have to make sure it is absolutely safe," Picker 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."

This would first have to pass through the regulatory authorities, but if it does, he said he hoped to start the first clinical trials in humans in the next two years.

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