July 2, 2007 -- A common ingredient found in over-the-counter vaginal spermicides may ease the transmission of human papillomavirus or HPV infection, at least in animals, according to a new study.
HPV infection causes genital warts and the majority of cervical cancers.
"Spermicides containing nonoxynol-9 may enhance the ability of the HPV to take hold in the genital tract, at least in animals," says researcher Jeff Roberts, MD, a postdoctoral fellow at the National Cancer Institute at the National Institutes of Health in Bethesda, Md. The study appears in the July issue of Nature Medicine.
While emphasizing that the study results are preliminary and may not hold true in people, Roberts tells WebMD that the findings deserve more study. Nonoxynol-9 is found in lubricants, contraceptive jellies and creams, and other birth control products. In recent years, its use has been found in some studies to boost the risk of transmission of HIV, the virus that causes AIDS.
The nonoxynol-9 and HPV link "will be news to most physicians," says Diane M. Harper, MD, MPH, director of the Gynecologic Cancer Prevention Research Group at the Norris Cotton Cancer Center of Dartmouth Medical School in Hanover, N.H. Harper, a leading expert on HPV infection, was not involved in the study but is familiar with the findings.
The researchers also found that using a vaginal lubricant containing the ingredient carrageenan seems to protect against getting HPV infection, even in the presence of nonoxynol-9.
Nonoxynol-9 and HPV
Roberts and his colleagues first pretreated one group of mice with the spermicide and another group with an inert substance, then exposed both groups to the HPV 16 virus, one of the "high-risk" HPV viruses thought to cause cervical cancer. A third group, not exposed to the virus or the other substances, served as a comparison group.
"One hundred percent of those exposed to nonoxynol-9 got infected" with HPV, Roberts tells WebMD. But the mice exposed to the inert substance were not infected.
Exactly why the spermicide seems to boost HPV infection risk isn't known, he tells WebMD.
WebMD attempted to contact several makers of nonoxynol-9, but none responded in time for publication.
Carrageenan Tests
Next, the researchers focused on the use of carrageenan, a substance widely used as a thickening agent in foods and also used in some vaginal lubricants, including the brands Divine No. 9 and BIOglide.
The researchers use pure carrageenan, not the commercial lubricant formulas. They pretreated one group of mice with the spermicide and another group with both the spermicide and carrageenan. The third group wasn't pretreated with anything and wasn't exposed to the virus.
None of the animals exposed to both the spermicide and carrageenan got infected with HPV, Roberts says. But of those exposed just to the spermicide, "all were infected," he says.
Exactly how carrageenan protects isn’t certain, either, Roberts say. It may interfere with the HPV interaction at the cellular level, helping to prevent infection, he tells WebMD.
"We have no idea whether this is valid in humans," cautions Harper. Human trials of carrageenan are definitely in order, she says.
HPV and Cervical Cancer
In 2007, more than 11,000 women in the U.S. will learn they have cervical cancer, according to estimates from the American Cancer Society, and about 3,670 women will die from it this year.
Of the more than 100 HPV types, about 30 or so types can cause genital HPV infections. Of those, certain types are classified as "high risk" because they lead to abnormal cell changes and can cause genital cancers. HPV 16 and 18 are high risk -- thought to cause about 70% of all cervical cancers.
Most sexually active men and women do contract HPV at some point. Most won't have symptoms and the virus will typically clear on its own, often within two years or less. When it doesn't clear, the cells in the cervix can continue to change abnormally, with precancer or cancer the result if no treatment is received.
Though the new HPV vaccine, Gardasil, can help prevent infection, and another HPV vaccine is expected to be available soon, neither is a perfect solution because they don't protect against all HPV types. For that reason, Roberts and other public health experts believe it is important to consider other interventions against HPV to reduce the toll of cervical cancer.
Preventing HPV Infection
More research is needed before any practical advice can be given, Roberts says. Carrageenan, he says, "has not been studied enough to officially recommend. It's something I think is worth investigating."
Earlier NIH research, Roberts says, showed that carrageenan is also protective against some of the other HPV types besides 16. And their research suggests that when the nonoxynol-9 and carrageenan are used together, the spermicide is still effective for birth control purposes.
Perhaps, Roberts says, manufacturers of commercial spermicides with nonoxynol-9 might consider adding carrageenan to the formulas.
"We recommend using condoms without spermicide," says Fred Wyand, spokesman for the American Social Health Association in Research Triangle Park, N.C., a nonprofit organization focusing on sexually transmitted disease information and education.
"There is some evidence that the spermicides can cause inflammation of the skin, which may make acquisition of sexually transmitted infections more likely," Wyand says.
If a woman wanted to prevent both HPV infection and pregnancy, Harper says, she would "probably tell her to use a different birth control method than a spermicide. She should still use a condom, and if she uses a lubricant, she could pick one with carrageenan."
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