Researchers have spent decades studying human papillomavirus, the sexually transmitted infection that causes most cervical cancers, but University of New Mexico’s Dr. Patti Gravitt says questions remain about the body’s ability to fend off the microorganism.
It is unclear, for example, whether our immune system can completely eliminate HPV infection, or whether the virus merely goes dormant, waiting to re-emerge, says Gravitt, a professor of pathology in the UNM School of Medicine.
She suspects that after an infectious phase HPV is not eradicated, instead remaining latent in epithelial tissue for the rest of a woman’s life. In some cases, where the immune system is compromised, the virus is re-activated, however.
“We control HPV infection immunologically very well in most women,” Gravitt says. “My paradigm is that control of HPV infection is the norm, and as long as you’re immune-competent, you’ll be fine.”
Gravitt, who came to UNM in August from Johns Hopkins University’s Bloomberg School of Public Health, was drawn here by her long friendship with Dr. Cosette Wheeler, who oversees New Mexico’s HPV Pap Registry, the nation’s only population-based cervical screening registry.
“It’s amazing what she has accomplished almost single-handedly,” Gravitt says. She believes Wheeler’s registry, which collects the results of all Pap and HPV test conducted in the state, holds the key to unraveling the secrets of the virus’s behavior.
Wheeler has also played a major role in conducting clinical tests of new vaccines that are highly effective in preventing HPV transmission. Her partnership with Gravitt helps place UNM at the forefront of HPV research.
Gravitt has studied HPV for most of her professional career. She earned her undergraduate and master’s degrees in molecular biology from the University of North Carolina at Charlotte before embarking on a career in the biotech industry.
Gravitt worked as a laboratory scientist for several companies, including Roche Molecular Systems, Inc., where she developed the current gold-standard methods for detecting and genotyping HPV nucleic acids. Her method uses highly accurate polymerase chain reaction technology to conduct broad-spectrum genotype assays.
Changing course, she headed to Johns Hopkins for her Ph.D. in epidemiology. “This is a good combination – molecular biology with epidemiology,” she says, explaining that the intersection of those disciplines yields a deeper understanding of the disease.
Most recently, Gravitt served as the vice dean for research at a graduate medical school in Malayasia established in collaboration with Johns Hopkins. There, she worked to develop a new program in interdisciplinary training.
“I went out to try to help them establish their research platform,” Gravitt says.
“We managed to get a pretty strong trajectory for bioinformatics training. It was very interesting, in terms of understanding how research is valued differently in different countries.”
HPV actually refers to a group of related viruses. A dozen or more strains have been associated with cancer, but two in particular – HPV types 16 and 18 – cause about 70 percent of all cervical cancers. Those strains are also strongly linked to anal, vaginal, vulvar, penile and oropharyngeal cancers.
While HPV infection is widespread, most people seem to clear the disease spontaneously – meaning no detectable virus is present. In a relatively small number of cases, it appears to cause cancer, however.
Worldwide, HPV is most prevalent in younger women. A second peak in prevalence around the age of menopause occurs in Central and South America and Western Africa, but is absent in much of the rest of the world, including North America.
Gravitt theorizes that the body never really eradicates HPV, and a flagging immune response in older women may explain why the virus activates in many of the women living in Third World countries.
She studied 843 middle-aged women in Baltimore, looking at their rates of infection and their number of lifetime sex partners, and found a potential explanation for the absence of a second peak in developed countries.
The older Baltimore women starting having sex before the dawn of the sexual revolution and had fewer partners, Gravitt says, so they likely avoided HPV infections in the first place. This pattern likely masks a trend toward reactivation that would otherwise be evident. “You can’t reactivate what you never got,” she says.
The introduction of highly effective HPV vaccines in recent years promises to reduce the rate of new infections, but there still isn’t broad coverage among U.S. women, she says.
Even with the protection afforded by a vaccine, human behavior still plays a big role in the prevalence of the disease, she adds. “Without population data, we are just going to be left guessing,” Gravitt says.
That’s where the New Mexico registry comes in. With six years of data, UNM researchers should be able figure out who is most at risk and which HPV strains are most prevalent.
“That’s kind of the exciting next new wave,” Gravitt says. “This is just a tremendous opportunity to answer some big questions.”