New HPV Vaccine Promising in Mice
TUESDAY April 15, 2008 -- Researchers say they've created a synthetic vaccine that can be delivered as a nasal spray for human papillomavirus -- the source of the most common sexually transmitted disease in the United States and a cause of cervical cancer.
The experimental vaccine, tested so far just with mice, also offers protection against different strains of HPV, the researchers said.
The existing vaccine for HPV, called Gardasil, protects against four strains of the virus that are responsible for about 70 percent of all cervical cancers. The Gardasil vaccine requires three injections for full protection.
"We have been trying to produce a single vaccine that would be able to protect patients against all cancer causing HPV types," said Richard B.S. Roden, lead researcher for the new study and an associate professor of pathology, gynecology and obstetrics, and oncology at Johns Hopkins University.
"What we have done is to try to develop a completely synthetic vaccine that would induce antibodies that would neutralize and protect against a whole range of these cancer-causing strains," he added.
The advantages of the synthetic vaccine are that it can be synthesized as if it were a drug, Roden said, adding that "it can be made chemically in the lab rather than having to use biological systems."
A synthetic vaccine also should be cheaper, Roden added. Using this approach, the vaccine could also be given nasally, he said.
"This may be another way to reduce the cost of vaccination, because you don't have to use needles," he said.
The findings are published in the April 15-18 issue of the Proceedings of the National Academy of Sciences.
In their experiments, Roden and his colleagues used a protein from one of the strains of HPV -- HPV16 -- to create a man-made vaccine in the laboratory. When the vaccine was given to mice either by injection or nasal spray, it protected not only against HPV16, but also against another strain of the virus -- HPV45.
Roden said the mice used in this experiments had special immune system T helper cells for the vaccine to attach itself. Whether human T helper cells would work in all groups of people isn't known, he said. "Right now, that's an area we are looking at," he said.
HPV is responsible for genital warts and about 99.7 percent of all cervical cancers worldwide.
Debbie Saslow, director of breast and gynecologic cancer at the American Cancer Society, said that if this vaccine could be developed, it would represent an important advance in getting more people vaccinated against HPV, especially in developing countries.
"While we have wonderful opportunities with the current vaccine, there are limitations," she said.
One limitation is the cost of the Gardasil vaccine, an estimated $300 to $500, Saslow added. "That's a limitation in this country, but particularly in the developing world where there is so much cervical cancer," she said.
The Gardasil vaccine also requires three shots, which is difficult in developing countries and among adolescents, Saslow said.
"Needle-less vaccination is the way to go for a lot of reasons," she said. "The current shots are extremely painful, and that's going to be a deterrent for teenage populations, as is going back and getting the three doses."
To learn more about HPV, visit the U.S. Centers for Disease Control and Prevention.
Posted: April 2008