Smallpox vaccine may serve as firewall against HIV: study

LOS ANGELES, May 18 (Xinhua) -- People who are vaccinated with the smallpox vaccine called "vaccinia" may have greater resistance against HIV infection, a new study finds.

The notion stems from recent work by researchers at the University of California, Los Angeles, and George Mason University in Manassas, Va. The findings were published in the May issue of Immunology, a journal of the British Medical Council (BMC).

If true, the finding could link the rapid, late 20th-century spread of HIV to the simultaneous vanquishing of smallpox disease and the removal of the smallpox vaccine from worldwide distribution, experts say.

The vaccine for smallpox was gradually removed from use between the 1950s and the 1970s, following global elimination of the disease.

"There have been several proposed explanations for the rapid spread of HIV in Africa," Dr. Raymond Weinstein of George Mason University said in a news release. These include "wars, the reuse of unsterilized needles and the contamination of early batches of polio vaccine," he said.

"However, all of these have been either disproved or do not sufficiently explain the behavior of the HIV pandemic," he said. " Our finding that prior immunization with vaccinia virus may provide an individual with some degree of protection to subsequent HIV infection suggests that the withdrawal of such vaccination may be a partial explanation."

The study authors noted that the vaccine for smallpox was gradually removed from use between the 1950s and the 1970s, following global elimination of the disease.

They point out that HIV began spreading faster in more or less the same time frame.

To get a closer look at how the two occurrences might be associated, the researchers analyzed the behavior of white blood cells sampled from patients recently immunized with the smallpox vaccine.

They found that after exposure to HIV, cells from immunized individuals were five times less likely to allow for HIV replication than the same cells taken from non-immunized patients.

The research team theorized that administration of the smallpox vaccine might trigger long-term changes in the immune system that guard against HIV infection. They further highlighted a certain receptor on the surface of white blood cells -- called "CCR5" -- as one possible target of such a beneficial change.

But the researchers said the results are preliminary and further studies are needed.

"While these results are very interesting and hopefully may lead to a new weapon against the HIV pandemic, they are very preliminary and it is far too soon to recommend the general use of vaccinia immunization for fighting HIV," said Weinstein.

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