© The Author 2007. Published by Oxford University Press.
CORRESPONDENCE |
Response: Re: Human Papillomavirus Type 16 and 18 Variants: Race-Related Distribution and Persistence
Affiliations of authors: Department of Pathology (LFX), School of Medicine and Department of Epidemiology (LFX, LAK), School of Public Health and Community Medicine, University of Washington, Seattle, WA
Correspondence to: Long Fu Xi, MD, PhD, 1914 North 34th St, Ste 300, Seattle, WA 98103 (e-mail: longfu{at}u.washington.edu).
Sichero et al. report an interesting finding and make an important observation. Their study in Brazil showed no difference between whites and nonwhites in clearance rates of European variants of human papillomaviruses (HPV) 16 and 18. In contrast, our United States–based study (1) showed more rapid clearance of European variants of HPV16 and HPV18 among African American women than among white women. It is likely that the observed lack of association between viral variants and time to clearance in the Brazilian study could be attributed in part to more racial admixing in Brazil than in the United States. It is also possible that differences in the specificity of racial categories used in each study contributed to the discrepant findings.
To illustrate how racial classification affects the outcome of interest, we revisited our data by including all three race categories in the Kaplan–Meier analysis. Of 594 women with HPV16 European variants who were eligible for analysis of persistence, the mean time from date of enrollment to HPV16 DNA negativity was 17.2 months (95% confidence interval [CI] = 15.8 to 18.6) for 460 white women, 12.9 months (95% CI = 11.2 to 14.5) for 100 African American women, and 14.8 months (95% CI = 11.7 to 18.0) for 34 women classified as Asian, Pacific Islander, American Indian, or Alaskan native. The overall likelihood of remaining positive was statistically significantly higher among white women than among African American women; it was intermediate for women classified as Asian, Pacific Islander, American Indian, or Alaskan native (Fig. 1). A similar pattern was observed for women with HPV18 European variants. Grouping women classified as Asian, Pacific Islander, American Indian, or Alaskan native into either the white or African American category would attenuate the race-related risk difference.
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Other race was defined as Asian, Pacific Islander, American Indian, or Alaskan native.The lack of association between genetic relatedness and detection of HPV16 European versus non-European variants in the Costa Rica study (2) is not surprising because the non-European HPV16 variant group in that study included both African and Asian American variants. Asian American variants of HPV16 are relatively common in American Indian women. Moreover, a study of a panel of 10 population-specific alleles found that American Indians and Europeans living in Brazil had a similar ranking on a scale of African ancestry (3). The statistically significant association between HPV16 variants and human leukocyte antigen (HLA) alleles found in the Costa Rica study supports our findings and indicates that specific HLA haplotypes may be associated with inadequate immune presentation of epitopes encoded by particular HPV variants, thereby affecting their capacity to become established or to replicate.
NOTES
The work was supported by Public Health Service grant CA 84396 to L. F. Xi. Dr Koutsky is currently conducting research sponsored by Merck.
The study protocol was approved by the institutional human subject review board of the University of Washington.
The authors have no commercial or other associations that might pose a conflict of interest.
REFERENCES
(1) Xi LF, Kiviat NB, Hildesheim A, Galloway DA, Wheeler CM, Ho J, et al. Human papillomavirus type 16 and 18 variants: race-related distribution and persistence. J Natl Cancer Inst (2006) 98:1045–52.
(2) Hildesheim A, Schiffman M, Bromley C, Wacholder S, Herrero R, Rodriguez A, et al. Human papillomavirus type 16 variants and risk of cervical cancer. J Natl Cancer Inst (2001) 93:315–8.
(3) Parra FC, Amado RC, Lambertucci JR, Rocha J, Antunes CM, Pena SD. Color and genomic ancestry in Brazilians. Proc Natl Acad Sci U S A (2003) 100:177–82.
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J Natl Cancer Inst 2007 99: 653-654.
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