You are here

Article Text

Article menu

Download PDFPDF

Epidemiology
Original article
DNA detection and seroprevalence of human papillomavirus in a cohort of adolescent women
  1. Aaron C Ermel1,
  2. Marcia L Shew2,
  3. Bree A Weaver1,2,
  4. Brahim Qadadri1,
  5. Cheryl Denski3,
  6. Wanzhu Tu3,
  7. Yan Tong3,
  8. J D Fortenberry2,
  9. Darron R Brown1,4
  1. 1Department of Internal Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
  2. 2Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana, USA
  3. 3Department of Biostatistics, Indiana University School of Medicine, Indianapolis, Indiana, USA
  4. 4Department of Immunology and Microbiology, Indiana University School of Medicine, Indianapolis, Indiana, USA
  1. Correspondence to Dr Darron R Brown, Indiana University School of Medicine, 635 Barnhill Drive, Room MS 224, Indianapolis, IN 46202, USA; darbrow{at}iu.edu

Abstract

Objectives Human papillomavirus (HPV) infections are common in adolescent women, while the rare cancerous sequelae of HPV infections do not generally occur until the 4th or 5th decades of life. This prospective study of a cohort of adolescent women was performed to further our knowledge of the natural history of incident and prevalent HPV infections.

Methods Self-vaginal swabs collected from high-risk, unvaccinated adolescent women in a longitudinal study were analysed for HPV DNA. Sera were collected at enrolment and later tested for HPV antibodies. Statistical analysis was performed to determine the HPV genotype distribution and duration of detection, and to determine rates of seropositivity and seroconversion for HPV types represented in the assays.

Results 146 subjects (mean enrolment age=15.4 years; mean duration of follow-up=5.8 years) had samples adequate for analysis of HPV detection, and 95 of these subjects had paired sera available. The cumulative prevalence for high-risk and low-risk HPV types was 95.9% and 91.1%, respectively. HPV types 6, 11, 16 and 18 (HPV types represented in the quadrivalent vaccine) were found at some point in 40.4%, 6.2%, 48% and 24% of participants, respectively. Serological data confirmed exposure to these vaccine-covered types, as well as to other high-risk HPV types.

Conclusions In this cohort of adolescent women, high- and low-risk HPV types were frequently detected, and serological data confirmed exposure in most subjects. The high-prevalence HPV types represented in the quadrivalent HPV vaccine further support vaccination of women at an age well before sexual debut.

  • HPV
  • SEROPREVALENCE
  • ANTIBODIES
  • ADOLESCENT

https://doi.org/10.1136/sextrans-2012-050886

Statistics from Altmetric.com

    Request Permissions

    If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.

    Introduction

    Certain oncogenic or high-risk human papillomavirus (HR-HPV) types are associated with malignancies of the cervix, vagina, vulva, anus and oropharynx.1–4 An initial HPV infection occurs in most young women within a few years of first vaginal sex, and subsequent infections by other types often occur for several years.5–7 Malignant sequelae (specifically carcinoma in situ and invasive cervical cancers) of HPV infection occur in the 4th or 5th decades of life, primarily in a subset of individuals with ‘persistent’ infection, meaning that the same type can be detected over varying time intervals before the clinical diagnosis of malignancy.8 Cohorts of women have been followed for HPV infections and cytological abnormalities in longitudinal studies using various follow-up periods.9 Few studies of adolescent women include sufficient follow-up to define incident and prevalent HPV infection, describe HPV detection within the context of detailed assessment of behavioural risk factors and assess HPV seroprevalence during longitudinal observation.

    The knowledge of the immune response in natural infection is incomplete.10 ,11 For example, Carter et al determined in a cohort of University aged women (unvaccinated against HPV) that the time to seroconversion after detection of HPV types 6, 16 or 18 was approximately 12 months. They also noted that 54.1–68.8% of women with incident infections seroconverted, and that transient infections were associated with failure to seroconvert.12 Thus, there is still much to be learned about HPV infection in adolescent women. In an era where safe and effective vaccines are available, answering such questions about the natural immune response to HPV infection may be challenging as the presence of antibody would reflect prior vaccination.

    Materials and methods

    Subjects

    This analysis consists of 150 women, none of whom received HPV vaccination because it was not available in the clinics until 2007 and was limited at that time to women less than 19 years of age. Subjects were enrolled under the Young Women's Project protocol, which was a cohort of adolescent women (n=386) enrolled starting in 1998 to study behaviours related to sexually transmitted infections (STIs) and was approved by the Institutional Review Board at the Indiana University School of Medicine.13 Adolescent women attending one of three primary-care clinics in Indianapolis were eligible for enrolment. Inclusion criteria were as follows: age of 14–17 years, able to understand English and provide written consent, have no serious psychiatric problems and have parental permission for participation. Adolescents could be enrolled regardless of past sexual experience, although pregnant women were not enrolled. Informed consent was obtained at enrolment. All subjects received financial compensation.

    Subjects provided self-obtained vaginal samples approximately every 3 months that were tested for STIs including HPV. Self-obtained vaginal swabs were used for this study as they are easily collected, compliance with collection is generally high, recovery of DNA is sufficient for testing, and results correlate well with cervical swab samples.14 ,15 Specifically, Chlamydia trachomatis and Neisseria gonorrhoeae were tested using a nucleic acid amplification test.16 ,17 Testing for Trichomonas vaginalis was performed by nucleic acid amplification test as described previously.18 Sera were collected from subjects at or near enrolment and at a second time point. At enrolment and annually, a written questionnaire assessed vaginal intercourse and other behaviours, and history of STI. Every 3 months, face-to-face interviews were conducted to assess contraceptive methods used (oral contraceptive pills, depo-medroxyprogesterone and condoms), number of sexual partners, frequency of coital events and the number condom-protected coital events over the preceding 3 months.

    DNA isolation and HPV testing

    DNA was extracted from self-obtained vaginal cotton swabs (‘samples’) using QIAamp MinElute Media Kit (Qiagen, Valencia, California, USA) as previously described.19 The Linear Array HPV Genotyping Test (Roche Molecular Diagnostics, Indianapolis, Indiana, USA) (LA-HPV) was used for HPV detection and genotyping.20 Reactions were amplified in a PerkinElmer TC9600 Thermal Cycler (PerkinElmer), and positive and negative controls (included in the LA-HPV) were performed with every run. The GH20/PC04 human β-globin target was coamplified to determine sample adequacy, and detection of specific HPV types was performed as previously described.21 The 37 HPV types detected in the LA-HPV are HR-HPV types (16, 18, 26, 31, 33, 35, 39, 45, 51, 52, 53, 56, 58, 59, 66, 67, 68, 69, 70, 73, 82 and Subtype 82 IS39) and low-risk HPV (LR-HPV) types (6, 11, 40, 42, 54, 55, 61, 62, 64, 72, 81, 83, 84 and 89).

    Serology testing

    Two different assays were used to determine antibody titres to HPV. The Total IgG Luminex immunoassay (LIA) is a nine-valent Luminex-based immunoassay, using yeast-derived L1 virus-like particles (VLPs) of HPV types 6, 11, 16, 18, 31, 33, 45, 52 and 58 coupled to a set of nine fluorescent Luminex microspheres. The Total IgG LIA measures all antibodies binding to HPV L1 VLPs and does not distinguish between neutralising and non-neutralising antibodies. The defined serostatus cut-offs were set at a level that delineated HPV-negative samples above VLP adsorption-depleted serum background.22

    The competitive LIA (cLIA) is a type-specific assay that measures antibody binding to a single neutralising epitope for each HPV-type L1 VLP (HPV 6, 11, 16 and 18), and does not measure complete antibody binding. Instead, the cLIA measures a type-specific, conformational, neutralising response that is a subset of the total immune response.23 Because each HPV type employs a type-specific monoclonal antibody with a unique binding affinity, cLIA mMU/mL titres cannot be compared between HPV types. The serostatus cut-offs were those used in the quadrivalent HPV vaccine clinical trials.24 The results were expressed as either less than the cut-off value or the absolute number. For both serological assays, values less than the cut-off were assigned a value of zero for calculating the mean values for each HPV type.

    Statistical analysis

    Demographic and clinical characteristics of the study subjects were summarised by descriptive statistics. The duration of a period of detection of a specific HPV type was defined as the time between the initial and the last detection of that type or until the end of the observation period. Median durations (in days) for type-specific infections were obtained from Kaplan-Meier estimates of the survival functions.25 Type-specific HPV detection ended when there were no further positive samples for that type and at least two or more samples were negative to the end of observation. However, if a period of detection lasted until the end of the observation period, that is, the last or the next to last sample remained positive for that type, the duration of the detection was considered as right censored, meaning that the infection lasted at least until the end of observation.

    Point and cumulative prevalence rates of HPV (per DNA test) for HR, LR and vaccine-protected types were provided at study entry, closeout, as well as for the entire observational time period. A subject was considered to have a type-specific HPV period of detection if two or more quarterly samples tested positive for that HPV type during the study. However, these quarterly samples did not have to be consecutive. For an individual subject, all samples positive for an HPV type previously detected were considered part of one type-specific period of detection. Any HPV type detected in only one sample during a subject's period of enrolment was dropped from the analysis.

    Results

    Description of subjects

    Data from 150 subjects were analysed. Subjects with ≥ three consecutive β-globin negative samples or ≤75% β-globin positive samples during the entire study period were excluded as this indicated specimen inadequacy. Specimens from 146 subjects (97.3%) were adequate based on β-globin positivity. For these 146 subjects, the mean age at enrolment was 15.4 years (range, 14–17 years old). The study group was 94.5% African–American and the remaining 5.5% were Caucasian. Mean duration of follow-up was 5.8 years (range, 3.9–9.2 years). At enrolment, 124 of 146 (84.9%) reported a history of vaginal sex, while the remaining 22 of 146 (15.1%) reported no vaginal sex prior to enrolment. The number of subjects who reported vaginal sex increased during the study (table 1). The mean age at first vaginal sex for those subjects who reported vaginal sex prior to enrolment was 14.4 years old. The mean cumulative numbers of lifetime sexual partners at enrolment and as of the last visit were 2.9 (SD, 3.7) and 10.6 (SD, 6.8), respectively. The prevalence of other STIs (C trachomatis, N gonorrhoeae and T vaginalis) was high in this cohort with close to 85% of women having tested positive for one or more STIs during follow-up (table 1).

    View this table:
    Table 1

    Study subject characteristics

    Analysis of self-collected vaginal samples

    At total of 3165 samples were collected from the 146 adolescent women and 3038 (96%) were positive for ß-globin. The mean number of self-collected vaginal samples per subject was 21.7 (range, 9.00–36.00 samples). Seventy-one per cent of β-globin positive samples (2150/3038 samples) were positive for at least one HPV type. A mean of 1.19 HR-HPV types (SD, 1.19; range, 0–8 types) and 0.73 LR-HPV types per sample (SD, 0.98, range, 0–5 types) were detected.

    Incidence and prevalence of type-specific HPV infections

    One hundred and forty of 146 subjects (95.9%) had samples positive for at least one HR-HPV type at any point in the study; and 133/146 (91.1%) had samples positive for at least one LR-HPV type. The mean number of HPV types detected per subject was 1.92 (SD, 1.95; range, 0–12.0 types). The most frequently detected HR-HPV types were HPV 16 (70/146 subjects, 47.9%), HPV 59 (67/146 subjects, 45.9%) and HPV 66 (65/146 subjects, 44.5%) (table 3). The most frequently detected LR-HPV types were HPV 84 (63/146 subjects, 43.2%), HPV 62 (60/146 subjects, 41.1%) and HPV 6 (59/146 subjects, 40.4%) (table 3).

    Detection of HR-HPV and LR-HPV types increased from enrolment to the final visit (table 2). Thirty-two of 146 subjects (21.9%) had at least one of the HPV types represented in the quadrivalent vaccine (ie, HPV types 6, 11, 16 and 18) detected at enrolment. At enrolment, the prevalence of HPV types 6, 11, 16 and 18 were 5.5%, 2.1%, 9.6% and 7.5%, respectively. At the end of the study, HPV types 6, 11, 16 and 18 were detected in 9.6%, 2.1%, 15.8% and 3.4%, respectively. Cumulative prevalence of HPV types 6, 11, 16 and 18 were 40.4%, 6.2%, 48% and 24%, respectively.

    View this table:
    Table 2

    Point and cumulative prevalence of HPV DNA detected

    Duration of type-specific HPV detection

    The median duration of detection periods were calculated for each HPV type (table 3). The median duration of detection for all HPV types was 423 days (95% CI 393 to 435). The median duration of detection of all LR-HPV types was 414 days (95% CI 338 to 435) and 428 days (95% CI 407 to 466) for all HR-HPV types. A survival analysis was performed to determine the significance of the observed difference in duration of detection between LR-HPV and HR-HPV types. Time to non-detection for LR-HPV types was significantly shorter than that for HR-HPV types (HR 0.85, 95% CI 0.73 to 0.98).

    View this table:
    Table 3

    Detection of HPV DNA for 37 types, including the percentage of 146 subjects positive for each type and the median duration of detection for each type

    Antibody detection

    Total IgG LIA results

    For 95 of 146 subjects, paired serology samples of sufficient volume were available from enrolment and a second time near the study conclusion. The median time between collections of the two sera was 5.17 years (range 0.25–8.17). Antibodies against the L1 major capsid protein were measured, and the median antibody titres of nine HPV types at enrolment and the second collection were determined (table 4). Specifically, for types represented in the quadrivalent vaccine, seropositivity at enrolment for HPV types 6, 11, 16 and 18 were 23.2%, 4.2%, 38.9% and 30.5%, respectively. At the second collection, seropositivity for HPV types 6, 11, 16 and 18 were 50.5%, 17.9%, 60% and 42.1%, respectively.

    View this table:
    Table 4

    Number of subjects with positive serology to the nine types assayed by the total IgG and cLIA assays

    Median titres increased during the study for all HPV types except HPV types 33, 52 and 58. Seroconversion rates for each HPV type were calculated regardless of their HPV DNA type results (table 4).

    cLIA results

    The same sera from 95 subjects were tested in the cLIA (table 4). Seroprevalence at enrolment was 24.2%, 2.1%, 6.3% and 6.3% for HPV types 6, 11, 16 and 18, respectively. Seroprevalence at the second collection was 48.4%, 12.6%, 35.8% and 20.0% for HPV types 6, 11, 16 and 18, respectively. The median titre increased for HPV types 6 and 18, but decreased for types 11 and 16. The rate of seroconversion was calculated for each of these four HPV types and is presented in table 4.

    Discussion

    This longitudinal study was performed to gain insights into the natural history of genital tract HPV infections in a group of adolescent women at high risk for STIs, but unvaccinated against HPV. This unique cohort, while modest in size, was very closely followed for about 6 years on average; some for up to 9 years. Multiple, sequential samples from each subject were analysed for HPV, and serological samples from approximately two-thirds of the subjects were also analysed for antibodies against HPV. A high percentage of subjects had HR-HPV and LR-HPV types detected at enrolment. Additionally, 21.9% had at least one vaccine type detected at enrolment. Nearly all subjects had evidence of infections with HR-HPV and LR-HPV types at some point during the study. Detection of HR-HPV and LR-HPV types increased from enrolment to the final visit, and a high cumulative prevalence of any of the four vaccine types among the study subjects was found. HPV 16, the causative agent of nearly half of all cervical cancers, was detected at some point in nearly 48% of these young women.

    Given that this cohort of adolescent women represents one with close, long-term follow-up, and was unvaccinated against HPV, it was informative to examine the presence of antibodies during natural infection. In contrast with HPV DNA detection, which has been shown to wax and wane over time, the antibody response to infection remains relatively constant over time, and may provide a better overall gauge of exposure in cohorts that would be at risk for repeated HPV exposure.26 ,27 As in prior studies, failure to seroconvert during the study period could have been due to a very transient infections.12 However, cases in which a specific HPV type was detected on only one occasion were removed from the analysis to provide a better estimation of the true prevalence of HPV infections.

    At the beginning of the study, seropositivity as measured in the nine-type total IgG LIA was highest for HPV types 6 and 16. Seropositivity against most HPV types increased during the study period similar to the results noted above in the total IgG LIA and cLIA. Results of the two serological assays were comparable (for types represented in both assays), which was best illustrated in the case of HPV 16 with seroconversion rates of 29.5% and 28.4% for the total IgG and cLIA assays, respectively. The increases in seropositivity for all HPV types tested (except in the case of HPV 45) indicated a high degree of past exposure to oncogenic HPV types.

    It is difficult to compare rates of seropositivity found in this cohort with those described in other studies due to variations in study populations and assays used. For example, Safaeian et al,28 measured seropositivity against HPV 16 and 18 in a population of women 18–25 years of age, using an ELISA, and found rates of 24.8% for both HPV types at enrolment. In another study, a lower rate of seropositivity against the four vaccine types using the cLIA was found in a population-based study.29 These authors found seropositivity rates of 5.3%, 1.9%, 4.0% and 0.9% for HPV types 6, 11, 16 and 18, respectively within the 14–19 year-old age group.29 However, a similar population-based study conducted in the Netherlands noted a higher seroprevalence for seven HPV types (HPV 16, 18, 31, 33, 45, 52 and 58) of 25.2% in young women.30 The higher percentage of seropositive women in our study may be due to the high number of lifetime partners.

    Serological testing for HPV may underestimate exposure to HPV as many women do not develop an antibody response. In our cohort for example, serology appeared to reflect overall exposure given that 60% of the subjects were seropositive for HPV 16 based on the total IgG assay at the second collection. This correlates to the percentage of subjects (48%) who were found to have HPV 16 infections based on DNA testing. When compared with testing by cLIA, the number of subjects positive for HPV 16 was below that of the total IgG result and HPV DNA testing (35.8% vs 60%). This would be expected given that not all women would be expected to develop the neutralising antibodies measured by this assay.

    This study has some limitations. While the overall number of subjects was small, these young women were followed closely for many years. There was little racial diversity among the subjects, which does not reflect the diversity in the population of the USA. It does, however mirror the demographics of the population served by the clinic sites used for recruitment, and is representative of those women at high risk for cervical cancer. Third, the young women in this study had a high number of sexual partners per subject; thus, the findings presented here cannot be extrapolated to all other ages or populations. Lastly, the evaluation of the antibody response to natural HPV infection was limited by the sample size, as only two-thirds of subjects had serum available for analysis. The collection times for the sera were not standardised and so, in some cases lack of seroconversion could also be attributed to the short time interval between sample collections.

    In conclusion, in a longitudinally followed cohort of adolescent women, nearly all were infected with multiple HPV types, including HR types and types represented in the HPV vaccines. Serological analysis confirmed the results of HPV DNA testing, thus contributing to the evolving comprehension of HPV epidemiology. Correlation of various characteristics of HPV DNA detection (duration and viral load) to the development of antibody is planned for future analyses. Our findings support the need to vaccinate young women against HPV before they become sexually active, rather than waiting until an age at which they may become exposed to HPV, including HPV 16, the type responsible for half of all cervical cancers.

    Key messages

    • High-risk and low-risk human papillomavirus (HPV) types are prevalent in sexually active adolescent women.

    • Testing for the presence of type-specific HPV antibodies to high-risk and low-risk types confirms exposure.

    • The high cumulative prevalence of the HPV types in the available vaccines supports the vaccination of adolescent women prior to sexual debut.

    Acknowledgments

    The authors thank Pharmaceutical Product Development for performing the serology testing for this study, and Merck & Co for funding the serological testing. Information has been previously presented in part at the 2010 Society of Adolescent Health and Medicine Annual Meeting, April 7–10, 2010, Toronto, Canada and at the International Papillomavirus Society Meeting, December 6–9, 2012, San Juan Puerto Rico.

    References

    1. ↵
      1. Walboomers JMM,
      2. Jacobs MV,
      3. Manos MM
      et al. Human papillomavirus is a necessary cause of invasive cervical cancer worldwide. J Pathol 1999;189:12–19.
      OpenUrlCrossRefPubMedWeb of Science
    2. ↵
      1. Munoz N,
      2. Bosch FX,
      3. de Sanjose S
      et al. Epidemiologic classification of human papillomavirus types associated with cervical cancer. N Engl J Med 2003;348:518–27.
      OpenUrlCrossRefPubMedWeb of Science
    3. ↵
      1. zur Hausen H
      . Papillomaviruses in the causation of human cancers—a brief historical account. Virology 2009;384:260–5.
      OpenUrlCrossRefPubMedWeb of Science
    4. ↵
      1. Gravitt PE
      . The known unknowns of HPV natural history. J Clin Invest 2011;121:4593–9.
      OpenUrlCrossRefPubMedWeb of Science
    5. ↵
      1. Smith JS,
      2. Melendy A,
      3. Rana RK,
      4. et al
      . Age-specific prevalence of infection with human papillomavirus in females: a global review. J Adolesc Health 2008;43:S5–25, S e1–41.
      OpenUrlCrossRefPubMedWeb of Science
    6. ↵
      1. Moscicki AB,
      2. Schiffman M,
      3. Burchell A,
      4. et al
      . Updating the natural history of human papillomavirus and anogenital cancers. Vaccine 2012;30(Suppl 5):F24–33.
      OpenUrlCrossRefPubMedWeb of Science
    7. ↵
      1. Winer RL,
      2. Hughes JP,
      3. Feng Q
      et al. Early natural history of incident, type-specific human papillomavirus infections in newly sexually active young women. Cancer Epidemiol Biomarkers Prev 2011;20:699–707.
      OpenUrlAbstract/FREE Full Text
    8. ↵
      1. Woodman CB,
      2. Collins S,
      3. Winter H
      et al. Natural history of cervical human papillomavirus infection in young women: a longitudinal cohort study. Lancet 2001;357:1831–6.
      OpenUrlCrossRefPubMedWeb of Science
    9. ↵
      1. Bratti MC,
      2. Rodriguez AC,
      3. Schiffman M
      et al. Description of a seven-year prospective study of human papillomavirus infection and cervical neoplasia among 10000 women in Guanacaste, Costa Rica. Rev Panam Salud Publica 2004;15:75–89.
      OpenUrlPubMedWeb of Science
    10. ↵
      1. Stanley M
      . Immune responses to human papillomavirus. Vaccine 2006;24(Suppl 1):S16–22.
      OpenUrlCrossRefPubMedWeb of Science
    11. ↵
      1. Brown DR,
      2. Garland SM,
      3. Ferris DG
      et al. The humoral response to Gardasil over four years as defined by total IgG and competitive Luminex immunoassay. Hum Vaccin 2011;7:230–8.
      OpenUrlPubMed
    12. ↵
      1. Carter JJ,
      2. Koutsky LA,
      3. Wipf GC
      et al. The natural history of human papillomavirus type 16 capsid antibodies among a cohort of university women. J Infect Dis 1996;174:927–36.
      OpenUrlAbstract/FREE Full Text
    13. ↵
      1. Tu W,
      2. Batteiger BE,
      3. Wiehe S
      et al. Time from first intercourse to first sexually transmitted infection diagnosis among adolescent women. Arch Pediatr Adolesc Med 2009;163:1106–11.
      OpenUrlCrossRefPubMedWeb of Science
    14. ↵
      1. Gravitt PE,
      2. Lacey JV Jr.,
      3. Brinton LA
      et al. Evaluation of self-collected cervicovaginal cell samples for human papillomavirus testing by polymerase chain reaction. Cancer Epidemiol Biomarkers Prev 2001;10:95–100.
      OpenUrlAbstract/FREE Full Text
    15. ↵
      1. Lorenzato FR,
      2. Singer A,
      3. Ho L
      et al. Human papillomavirus detection for cervical cancer prevention with polymerase chain reaction in self-collected samples. Am J Obstet Gynecol 2002;186:962–8.
      OpenUrlCrossRefPubMedWeb of Science
    16. ↵
      1. Van Der Pol B,
      2. Quinn TC,
      3. Gaydos CA
      et al. Multicenter evaluation of the AMPLICOR and automated COBAS AMPLICOR CT/NG tests for detection of Chlamydia trachomatis. J Clin Microbiol 2000;38:1105–12.
      OpenUrlAbstract/FREE Full Text
    17. ↵
      1. Van Der Pol B,
      2. Martin DH,
      3. Schachter J
      et al. Enhancing the specificity of the COBAS AMPLICOR CT/NG test for Neisseria gonorrhoeae by retesting specimens with equivocal results. J Clin Microbiol 2001;39:3092–8.
      OpenUrlAbstract/FREE Full Text
    18. ↵
      1. Van Der Pol B,
      2. Kraft CS,
      3. Williams JA
      . Use of an adaptation of a commercially available PCR assay aimed at diagnosis of chlamydia and gonorrhea to detect Trichomonas vaginalis in urogenital specimens. J Clin Microbiol 2006;44:366–73.
      OpenUrlAbstract/FREE Full Text
    19. ↵
      1. Brown DR,
      2. Shew ML,
      3. Qadadri B
      et al. A longitudinal study of genital human papillomavirus infection in a cohort of closely followed adolescent women. J Infect Dis 2005;191:182–92.
      OpenUrlAbstract/FREE Full Text
    20. ↵
      1. Castle PE,
      2. Porras C,
      3. Quint WG,
      4. et al
      . Comparison of two PCR-based human papillomavirus genotyping methods. J Clin Microbiol 2008;46:3437–45.
      OpenUrlAbstract/FREE Full Text
    21. ↵
      1. Brown DR,
      2. Shew ML,
      3. Qadadri B,
      4. et al
      . . A longitudinal study of genital human papillomavirus infection in a cohort of closely followed adolescent women. J Infect Dis 2005;191:182–92.
      OpenUrlAbstract/FREE Full Text
    22. ↵
      1. Opalka D,
      2. Matys K,
      3. Bojczuk P,
      4. et al
      . Multiplexed serologic assay for nine anogenital human papillomavirus types. Clin Vaccine Immunol 17:818–27.
    23. ↵
      1. Dias D,
      2. Van Doren J,
      3. Schlottmann S
      et al. Optimization and validation of a multiplexed luminex assay to quantify antibodies to neutralizing epitopes on human papillomaviruses 6, 11, 16, and 18. Clin Diagn Lab Immunol 2005;12:959–69.
      OpenUrlCrossRefPubMed
    24. ↵
      1. Villa LL,
      2. Costa RL,
      3. Petta CA
      et al. High sustained efficacy of a prophylactic quadrivalent human papillomavirus types 6/11/16/18 L1 virus-like particle vaccine through 5 years of follow-up. Br J Cancer 2006;95:1459–66.
      OpenUrlCrossRefPubMedWeb of Science
    25. ↵
      1. Therneau T,
      2. Grambsch P
      . Modeling survival data: extending the Cox model. New York: Springer, 2000.
    26. ↵
      1. af Geijersstam V,
      2. Kibur M,
      3. Wang Z
      et al. Stability over time of serum antibody levels to human papillomavirus type 16. J Infect Dis 1998;177:1710–14.
      OpenUrlAbstract/FREE Full Text
    27. ↵
      1. Silins I,
      2. Kallings I,
      3. Dillner J
      . Correlates of the spread of human papillomavirus infection. Cancer Epidemiol Biomarkers Prev 2000;9:953–9.
      OpenUrlAbstract/FREE Full Text
    28. ↵
      1. Safaeian M,
      2. Porras C,
      3. Schiffman M
      et al. Epidemiological study of anti-HPV16/18 seropositivity and subsequent risk of HPV16 and -18 infections. J Natl Cancer Inst 2010;102:1653–62.
      OpenUrlAbstract/FREE Full Text
    29. ↵
      1. Markowitz LE,
      2. Sternberg M,
      3. Dunne EF
      et al. Seroprevalence of human papillomavirus types 6, 11, 16, and 18 in the United States: National Health and Nutrition Examination Survey 2003–2004. J Infect Dis 2009; 200:1059–67.
      OpenUrlAbstract/FREE Full Text
    30. ↵
      1. Scherpenisse M,
      2. Mollers M,
      3. Schepp RM
      et al. Seroprevalence of seven high-risk HPV types in The Netherlands. Vaccine 2012;30:6686–93.
      OpenUrlCrossRefPubMedWeb of Science

    Footnotes

    • Handling editor Jennifer Smith

    • Contributors ACE, MLS and DRB collaborated in the writing of this manuscript. JDF, WT, YT and BAW participated in the revision of the manuscript. MLS and JDF were involved in management of the cohort. DRB was involved in project design and management as the Principal Investigator of the grant funding the project. BQ was involved in the testing of samples and preparation of data. CD was responsible for data management and assisted in data analysis. ACE, DRB MLS, JDF, WT, YT and BAW were responsible for data interpretation and analysis.

    • Funding This work was supported by the National Institute of Allergy and Infectious Diseases at the National Institutes of Health (Grant Number NIH R01 AI072020-01A2 to DRB); Supported in part by a research grant from the Investigator-Initiated Studies Program of Merck, Sharp & Dohme Corp. The opinions expressed this paper are those of the authors and do not necessarily represent those of Merck, Sharp & Dohme Corp. Serology testing was performed by Pharmaceutical Product Development.

    • Competing interests MLS: Investigator for Merck & Co. related HPV vaccine trials. DRB: Received lecture fees, advisory board fees, and intellectual property fees from Merck and Co.

    • Ethics approval The study was approved by the local Institutional Review Board (IRB) at Indiana University School of Medicine, Indianapolis, IN, USA.

    • Provenance and peer review Not commissioned; externally peer reviewed.