Scientists have discovered the workings of a virus that causes genital warts, and largely because of these discoveries the virus has emerged as the primary suspect in nearly all cervical cancer.
Researchers say they have found after several years of study that thevirus invades healthy cells, chemically manipulates them into dividing and then steals the substances the cells make in division to make copies of itself.
Most of the time, researchers have learned, the virus merely steals enough of the substances, proteins and enzymes to make a few copies of itself. Apparently, scientists say, the immune system keeps the wart virus in check.
But scientists have found that if this control lapses, the virus becomes more aggressive and causes the growth of warts, which in turn shed new copies of the virus.
In extreme cases, the virus can invade normal cells and transform them into cancerous cells.
Based on this new knowledge of how the virus works, researchers said, they should be able to develop a vaccine against the virus, which would prevent most cases of cervical cancer.
Routine screening has greatly reduced the rate of cervical cancer in the United States. About 13,000 American women develop the disease each year, and 5,000 die from it. Worldwide, cervical cancer kills more than half a million women each year.
If the findings lead to a successful vaccine, the medical impact would be immense, said Dr. Tom Broker of the University of Rochester Medical Center, a leading expert on wart viruses.
Experts estimate that at least 90 percent of all cervical tumors contain the wart virus. Although the virus does not act alone in producing cancer, Dr. Broker said, it is the primary factor in the disease.
Humans are afflicted by 70 strains of wart viruses, each of which specializes in one type of epithelium, the kind of cell that forms the skin and lines the mouth, respiratory tract, genital tract and other body surfaces.
An estimated 20 percent to 30 percent of adults are infected with sexually transmitted wart viruses, Dr. Broker said, but most suffer no ill effects from the viruses because their immune systems hold them in check.