New HIV-1 group

Scientists identify another variant of the virus that can cause AIDS

A new variant of HIV, the virus that can cause AIDS, has emerged, scientists report online August 2 in Nature Medicine. The discovery of the new version, in a 62-year-old Cameroonian woman living in Paris, suggests this virus and related primate-infecting viruses will continue to morph, though not necessarily into forms that are lethal to humans. Infected since at least 2004, the Cameroonian woman has not yet shown signs of AIDS.

“I think we are going to continue to see new lineages of HIV discovered, and there are probably going to continue to be wild to human transmissions in this and many other viruses,” comments evolutionary biologist Joel Wertheim of the University of Arizona in Tucson.

Analyses of the virus’s genetic code found that it is more similar to the version that infects gorillas than to other human strains of HIV, says Jean-Christophe Plantier of the University of Rouen in France, who led the new work.

There are three main groups of HIV-1: M, N and O. Group M (for major) is responsible for most AIDS cases. Each group is thought to have independently jumped from chimpanzees to humans, probably through the killing or eating of infected animals. Group O is also similar to the gorilla version. (Though how gorillas acquired the virus remains unclear since they are vegetarians and tend to keep to themselves.)

Because the new version is different from existing strains and from the strain known to infect gorillas, Plantier and his colleagues do not think it jumped directly from a gorilla to the Cameroonian woman but probably infected other people first. The researchers have designated it a new HIV-1 group, named group P.

More species-to-species transmissions are likely, Wertheim says. But it isn’t clear whether such transmissions occur because the virus regularly adapts to new hosts or because it has had many opportunities to infect hosts — especially in recent years with ecological changes that result in more species-to-species and human-to-human contact.

Scientists think that the majority of U.S. AIDS cases result from one successful introduction, when the strain responsible for group M became established in the past century. There were probably many transmissions from chimps to humans before the strain began to spread among humans, though, Wertheim says. If an infected individual moves to a city or travels by airplane, a strain that might have otherwise petered out “may gain a foothold,” he says. “And there you have it.”

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