Cervical cancer virus risk may depend on race

Roxanne Khamsi:

Race may influence a woman’s risk of a virus known to cause cervical cancer, researchers report. The new study finds that a variant of the human papillomavirus (HPV) from a particular geographical region will infect a woman longer if her ancestors come from the same region. Experts say it is an uncommon example of how people are more prone to viral agents from their own place of origin.

HPV is by no means an uncommon virus: about 50% of sexually active women between the ages of 18 and 22 are believed to be infected with HPV at some point. While most of these infections are cleared up by the women’s natural immune system, some linger and can eventually cause cervical cancer.

To find out how race may influence vulnerability to HPV, Long Fu Xi at the University of Washington in Seattle, US, and colleagues followed over 1000 women infected with HPV for two years. They analysed the HPV in samples from each patient’s cervical swabs to determine its genetic code, revealing the region from which it evolved.

“The HPV virus is a pretty interesting one because it maintains its evolutionary history,” says Rob DeSalle, an expert in evolutionary genetics at the American Museum of Natural History in New York. He says this stands in contrast with a disease such as HIV, which mutates rapidly, muddling such evolutionary information.

In white women, infections linked to the European variant of the HPV-16 strain persisted for about 17 months, on average, while infections from African variants of the virus lasted only half as long.

In African-American women, by contrast, infections from the European variant lasted 13 months on average. This was a shorter-lasting infection than those caused by African variants of the virus, but only by about 15%.

Exactly why variants of a certain origin are better suited to infect women with ancestors from the same place remains a mystery. It may be because the virus adapts to take advantage of the local human population’s genetic makeup. “It’s kind of an evolutionary dance,” says DeSalle. “That’s the nice way of putting it. Most people call it an arms race.”

Xi believes the findings may help in preventing cervical cancer. Longer infections may translate into greater cancer risk, he says. Xi believes that women with HPV should know what variant of the virus they have and be particularly mindful of the infection if the variant matches their racial background.

In contrast to the current findings, other studies have found that non-European variants of HPV are actually more likely than European ones to cause cancer in white women. But Xi says these previous studies are too small to be definitive. He hopes to explore how race may influence the cancer risk from HPV in future work.

A vaccine against HPV-16 and HPV-18, two of the strains most likely to result in cancer, became available in the US in June 2006.

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