HPV Strains Affecting African-American Women Differ from Vaccines
By Duke Medicine News and Communications
Oct. 28, 2013 - NATIONAL HARBOR, M.D. - Two subtypes of human papillomavirus (HPV) prevented by vaccines
are half as likely to be found in African-American women as in white women with precancerous cervical lesions, according to researchers
at Duke Medicine.
The findings, presented on Oct. 28, 2013, at the 12th annual International Conference on Frontiers in Cancer Prevention
Research hosted by the American Association for Cancer Research, suggest that African-American women may be less likely to benefit
from available HPV vaccines to prevent cervical cancer.
HPV is a common sexually transmitted infection with more than 40 subtypes. The virus causes nearly all cases of cervical cancer,
which begin as precancerous cervical abnormalities. Two vaccines currently available to young women prevent infection by HPV 16
and HPV 18, the HPV strains responsible for about 70 percent cervical cancers.
"Screening programs for cervical cancer are known to work well, with around 90 percent of sexually active women getting screened
through Pap tests," said senior author Cathrine Hoyo, Ph.D., M.P.H., associate professor of obstetrics and gynecology at Duke
University School of Medicine.
"The question is, if screening rates are comparable in African-American and white women, why are the rates of cervical cancer
and mortality higher among African-American women when we have a program that works so well?"
Hoyo and her colleagues sought to better understand these disparities by determining if African-American and white women in the U.S.
are infected with the same subtypes of HPV. The researchers enrolled 572 participants -- 280 African-American women and 292
non-Hispanic white women -- who came for additional testing after receiving abnormal Pap test results.
Of the 572 participants, 245 (43 percent) had no precancerous cervical abnormalities, 239 (42 percent) had early precancerous cervical
abnormalities, and 88 (15 percent) had advanced precancerous cervical abnormalities. Seventy-three percent of the women infected with
HPV were infected with multiple HPV subtypes.
When the researchers looked at the specific strains of HPV, they found that white women and African-American women were often infected
with different subtypes. The most frequent HPV subtypes detected among white women with early precancerous cervical abnormalities were
16, 18, 56, 39 and 66, while HPV subtypes 33, 35, 58 and 68 were the most common ones detected in African-Americans.
In those with advanced precancerous cervical abnormalities, HPV 16, 18, 33, 39 and 59 were the most common genotypes detected in white
women, whereas HPV 31, 35, 45, 56, 58, 66 and 68 were the most prevalent in African-American women.
"Compared with white women, we saw that African-American women had about half as many infections with HPV 16 and 18, the subtypes
that are covered by HPV vaccines," said Adriana Vidal, Ph.D., assistant professor of obstetrics and gynecology at Duke University
School of Medicine and the study's first author. "Since African-American women don't seem to be getting the same subtypes of HPV
with the same frequency, the vaccines aren't helping all women equally."
A new HPV vaccine targeting nine HPV subtypes (6, 11, 16, 18, 31, 33, 45, 52 and 58) is currently being tested in phase III trials.
While the new vaccine may help prevent additional HPV infections by covering new subtypes, it may not address the disparities found
in this study.
"The most disconcerting part of this new vaccine is it doesn't include HPV 35, 66 and 68, three of the strains of HPV of which
African-American women are getting the most," Hoyo said. "We may want to rethink how we develop these vaccines, given that
African-Americans tend to be underrepresented in clinical trials."
The researchers noted that while these findings are compelling, the results are preliminary and the studies should be replicated
in larger populations. Hoyo, Vidal and their colleagues are also continuing the research to define epigenetic marks that can be
used to predict which precancerous cervical abnormalities will advance.
In additional to Hoyo and Vidal, study authors from Duke include Fidel Valea, Anne Ford, Francine Overcash and Susan K. Murphy of the
Department of Obstetrics and Gynecology; Rex Bentley and Katherine Grant of the Department of Pathology; and Maggie Gradison and
Kimberly S. H. Yarnall of the Department of Community and Family Medicine. Jennifer S. Smith of the Department of Epidemiology
at Gillings School of Global Public Health at the University of North Carolina at Chapel Hill also contributed to the research.
The research was supported by the National Cancer Institute (R01CA142983 and R01CA142983-02S1). The authors reported no conflicts of
interest.
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Source: Duke University Health System
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