As a married woman, Shawnna Greco wouldn't be a high-risk candidate for a sexually transmitted disease.
But in the interest of science, she willingly offered up her arm to test a vaccine at the Medical College of Georgia that seeks to combat human papillomavirus, strains of which can cause cervical cancer in women.
"If something like this (vaccine) could actually happen, it would be a wonderful thing," said Mrs. Greco, 24, a first-year physician assistant student at MCG.
The experimental vaccine is part of an array of clinical trials at MCG focusing on HPV and cervical cancer.
Human papillomavirus is the most common sexually transmitted disease, said Daron Ferris, family medicine physician at MCG and principal investigator on the vaccine trials. Estimates are that 50 percent of sexually active women have had it at one time or another, including about 15 percent who have a current infection, said Lauri Markowitz, medical epidemiologist with the Division of Sexually Transmitted Diseases at the Centers for Disease Control and Prevention.
Yet ironically it is one of the least known, Dr. Ferris said.
"It is the most common. And it's probably the most poorly understood," the doctor said.
A recent survey shows very few high school students even know what HPV is, Dr. Ferris said. "And for that matter even know what a Pap smear is used for. There's very little understanding."
A Pap smear is a swab test looking for pre-cancerous or malignant cells in a woman's cervix, which may be caused by HPV infecting the cells. Someone with HPV might get genital warts or itching but more likely will have no symptoms at all and might have no clue they are infected, Dr. Ferris said.
"Unfortunately, the abnormal growths that occur are usually caused by the non-oncogenic (not cancer-causing) strains of HPV," Dr. Ferris said. Most cancer-causing strains do not produce growths, a warning sign to physicians.
In about 60 percent of the cases, the person's immune system will clear the infection within nine months, although dormant traces of the virus may hang around in the cells.
There are 100 or so known strains of HPV, and some can cause the changes in cells that can lead to cervical cancer. The vaccine being tested at MCG and other centers around the country seeks to stop two of those strains, labeled 16 and 18, Dr. Ferris said.
"It's kind of a silent epidemic," Dr. Ferris said.
And the difference in survival in catching it early vs. late, as with many cancers, is life or death, Dr. Ferris said. Caught early, it is "one of the most successfully treatable cancers, with a five-year survival rate of 92 percent," according to the American Cancer Society's Cancer Prevention and Early Detection. But once it has spread to other organ systems, chances of survival fall to less than 25 percent, Dr. Ferris said. There are 14,000 cases and 5,000 deaths annually in the United States, Dr. Markowitz said.
"In spite of Pap smear, there are still 5,000 deaths in the U.S.," Dr. Markowitz said.
And in developing countries where resources are scarce and access to Pap smears is more difficult, cervical cancer is the second leading cancer among women, Dr. Ferris said. That's why part of the vaccine trial is being conducted in Brazil, and Dr. Ferris and researchers at Johns Hopkins are working in Mexico on a test women can conduct themselves and mail in.
The vaccine trial is for women like Mrs. Greco who have not had an abnormal Pap test and do not have HPV. But Dr. Ferris is working on another study testing gene therapy on women who have already contracted HPV and developed a high-grade lesion. Normally these women would require some type of surgery, but in this case they receive a series of injections.
"It hopefully targets only those cells that are involved, to destroy those cells or draw the immune system's attention to those cells," Dr. Ferris said.
About 85 percent of women who have an abnormal Pap test do have one of the cancer-causing strains, and having a way to prevent that would go a long way toward preventing cervical cancer, Dr. Ferris said.
"We think that if these oncogenic strains of HPV invoke a good immune response (from the vaccine) to prevent women from acquiring these strains, then theoretically we will have eliminated a cancer, a type of cancer, by vaccination," Dr. Ferris said.
Reach Tom Corwin at (706) 823-3213.
|Seeking test subjects|
Medical College of Georgia is looking for women between the ages of 15 and 25 who have not had an abnormal Pap smear or who have not had an infection of human papillomavirus to test a new vaccine against the virus. Study subjects will get a free physical exam and a free Pap smear and be tested for HPV. The subjects will get either the vaccine or a placebo. The vaccine does not contain a living virus and cannot cause HPV. For more information, call (706) 721-2535.
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