Human papillomavirus testing in the prevention of cervical cancer

Strong evidence now supports the adoption of cervical cancer prevention strategies that explicitly focus on persistent infection with the causal agent, human papillomavirus (HPV). To inform an evidence-based transition to a new public health approach for cervical cancer screening, we summarize the natural history and cervical carcinogenicity of HPV and discuss the promise and uncertainties of currently available screening methods. New HPV infections acquired at any age are virtually always benign, but persistent infections with one of approximately 12 carcinogenic HPV types explain virtually all cases of cervical cancer. In the absence of an overtly persistent HPV infection, the risk of cervical cancer is extremely low. Thus, HPV test results predict the risk of cervical cancer and its precursors (cervical intraepithelial neoplasia grade 3) better and longer than cytological or colposcopic abnormalities, which are signs of HPV infection. The logical and inevitable move to HPV-based cervical cancer prevention strategies will require longer screening intervals that will disrupt current gynecologic and cytology laboratory practices built on frequent screening. A major challenge will be implementing programs that do not overtreat HPV-positive women who do not have obvious long-term persistence of HPV or treatable lesions at the time of initial evaluation. The greatest potential for reduction in cervical cancer rates from HPV screening is in low-resource regions that can implement infrequent rounds of low-cost HPV testing and treatment.

Persistence of concurrent infections with multiple human papillomavirus types: a population-based cohort study

The presence of more than one human papillomavirus (HPV) genotype may influence the duration of prevalently detected infections. This analysis included 1,646 infections detected at enrollment in 980 women from the Guanacaste, Costa Rica, cohort who were actively followed up every 6-12 months for up to 8 years. We categorized HPV infections as single or multiple types. Persistence of infections was estimated using discrete-time survival analysis. The difference between the duration of single and that of concurrent multiple type-specific prevalent HPV infections was not significant (P = .9; log-rank test). Concurrent, prevalent detection of additional HPV types did not change the likelihood of viral persistence.

Alterations of T-cell surface markers in older women with persistent human papillomavirus infection

We previously reported decreased lymphocyte proliferative responses among older women with persistent human papillomavirus (HPV) infection. To characterize the phenotype of peripheral lymphocytes associated with persistent HPV infection, we evaluated the expression of different cell surface markers in peripheral blood mononuclear cells (PBMCs) from a case-control study within a 10,049 woman population-based cohort study in Guanacaste, Costa Rica. Women in the cohort aged 46-74 and with HPV results at their 5th year anniversary visit were considered, and all women (n = 87) with persistent HPV infections, all women (n = 196) with transient HPV infections and a random sample of HPV DNA-negative women (n = 261) frequency-matched to cases on age were selected for this study. A median of 3 years after the case-control matching visit, cervical cells were collected for liquid-based cytology and repeat HPV DNA genotyping. Blood was obtained from which PBMCs were extracted and cryopreserved for immunological phenotyping via flow cytometry. Significant increases in risk of HPV persistence were observed for 3 marker subsets indicative of immune cell activation/differentiation. Relative risk estimates were 5.4 (95% CI = 2.2-13.3) for CD69(+)CD4(+), 2.6 (95% CI = 1.2-5.9) for HLADR(+)CD3(+)CD4(+) and 2.3 (95% CI = 1.1-4.7) for CD45RO(+)CD27(-)CD8(+). A significant decrease in HPV persistence was observed for a subset marker indicative of an immature, undifferentiated memory state CD45RO(+)CD27(+)CD4(+) (OR = 0.36; 95% CI = 0.17-0.76). Adjustment for these markers only partially explained the previously reported association between decreased lymphoproliferative responses and persistent HPV infection. Whether phenotypic alterations observed predispose to HPV persistence or result from it should be the focus of future studies.

Chlamydia trachomatis and risk of prevalent and incident cervical premalignancy in a population-based cohort

BACKGROUND

Cofactors might affect the risk of the rare progression from infection with carcinogenic human papillomavirus (HPV) to cervical premalignancy to invasive cancer. Some studies have observed that Chlamydia trachomatis infection is associated with increased risk for cervical cancer. In a large prospective cohort, we assessed the role of C trachomatis in cervical premalignancy and addressed confounding by HPV.

METHODS

We identified 182 women with prevalent and 132 women with incident histological cervical intraepithelial neoplasia grade 2 (CIN2), grade 3 (CIN3), or cervical cancer (CIN2+) in the Costa Rica HPV Natural History Study. Control subjects were 995 (approximately 10% of the 10 049) subjects who were randomly selected from the same study. Cervical HPV status at enrollment was determined by MY09/MY11 polymerase chain reaction amplification and dot-blot hybridization. The presence of C trachomatis DNA in cervical exfoliated cells at enrollment was determined by a novel serovar-specific polymerase chain reaction-based C trachomatis detection and genotyping assay. Plasma drawn at enrollment from each subject was used to determine C trachomatis immunoglobulin G (IgG) status. Logistic regression was used to examine the association between C trachomatis and CIN2+, taking into account possible confounding by HPV.

RESULTS

C trachomatis positivity at enrollment was associated with CIN2+ and concurrent and subsequent carcinogenic HPV infection. To account for confounding by HPV status, we restricted the analysis to women positive for carcinogenic HPV DNA at enrollment and found no association between C trachomatis status (as assessed by DNA or IgG) at enrollment and combined prevalent and/or incident CIN2+ (for C trachomatis DNA positivity, odds ratio = 0.77, 95% confidence interval = 0.42 to 1.41; for C trachomatis seropositivity, odds ratio = 1.09, 95% confidence interval = 0.85 to 1.41).

CONCLUSIONS

We found no association between C trachomatis status, as assessed by DNA or IgG, and risk of cervical premalignancy, after controlling for carcinogenic HPV-positive status. Previous positive associations between C trachomatis and cervical premalignancy could have been caused, in part, by an increased susceptibility to HPV infection.

Human papillomavirus genotypes in cervical intraepithelial neoplasia grade 3

BACKGROUND

There are few large case series describing the human papillomavirus (HPV) genotypes found in women diagnosed with rigorously reviewed cervical intraepithelial neoplasia grade 3 (CIN3), cervical precancer.

METHODS

The Atypical Squamous Cells of Undetermined Significance (ASCUS) and Low-Grade Squamous Intraepithelial Lesion (LSIL) Triage Study (ALTS) was a clinical trial to evaluate the best management strategies for women with equivocal (ASCUS) or mildly abnormal (LSIL) Pap tests. During enrollment and the 2-year follow-up, 608 women had a histopathologic diagnosis of CIN3 and PCR-based HPV genotyping results on cervical specimens. The genotyping results were ranked hierarchically according to cancer risk: HPV16 > other carcinogenic HPV > noncarcinogenic HPV > PCR negative.

RESULTS

Among the 608 women diagnosed with CIN3, 601 (98.8%) cases were positive for any HPV genotype and 95.4% for any carcinogenic HPV. HPV16 (59.9%), HPV31 (18.1%), HPV52 (14.8%), HPV51 (14.0%), and HPV18 (13.2%) were the five most common HPV genotypes detected. Younger age, consensus histologic confirmation, smoking, and multiparity increased the likelihood of testing HPV 16 positive. Specifically, HPV16-positive CIN3 occurred at a younger age than CIN3 positive for other carcinogenic HPV genotypes (median of 23.5 years versus 25 years, respectively; P = 0.0003, Kruskal-Wallis).

CONCLUSIONS

HPV16-positive CIN3 was more commonly diagnosed in younger women (versus older women), with consensus diagnosis (versus some disagreement between reviewers), and in smokers (versus nonsmokers), and was less commonly diagnosed in multiparous women compared CIN3 positive for other carcinogenic HPV genotypes.

IMPACT

In populations vaccinated against HPV16 (and HPV18), the median age of CIN3 in women with ASCUS and LSIL cytology should shift to older ages, possibly permitting later age at first screening.

Comparison of measurements of human papillomavirus persistence for postcolposcopic surveillance for cervical precancerous lesions

OBJECTIVE

Following guidelines, women evaluated by colposcopy, but not found to have a precancerous lesion, could be tested again at 12 months for carcinogenic human papillomavirus (HPV). Compared with pooled-probe testing, measuring HPV genotype-specific persistence might better predict subsequent grade 3 cervical intraepithelial neoplasia (CIN3).

METHODS

For women enrolled in the immediate colposcopy arm of the Atypical squamous cells of undetermined significance (ASCUS) and Low-grade squamous intraepithelial lesion (LSIL) Triage Study (ALTS), who underwent enrollment colposcopy but were without prevalently detected CIN2 or worse (CIN2+; n = 671), we compared 1-year HPV persistence, as measured by a pooled HPV genotype test (hybrid capture 2; hc2) versus a research PCR HPV genotyping test (line blot assay; LBA) as predictors of "missed prevalent" or possibly incident CIN3 diagnosed between 12 and 24 months.

RESULTS

Thirty-two (4.8%) women were diagnosed with subsequent CIN3. Testing repeatedly hc2-positive (hc2+) was more common (49.0%) than genotype-specific persistence as detected by LBA (30.3%, P < 0.01). Although absolute risks of CIN3 following repeat hc2+ or genotype-specific persistence were similar (8.8% versus 8.4%, P = 0.86), repeat hc2+ was more sensitive for identifying CIN3 than genotype-specific persistence (90.6% versus 53.1%, P < 0.01). Among 329 women repeatedly hc2+, women with persistent HPV16 were at higher risk of CIN3 than non-HPV16-persistent women (23.1% versus 7.0%, P < 0.01).

CONCLUSIONS

For postcolposcopy management, 1-year HPV persistence as measured by hc2 would recall more women but was more sensitive and similarly predictive for CIN3 in the following year than detection of genotype-specific persistence by LBA.

IMPACT

Although find little utility for measuring type-specific persistence, testing for persistent HPV16 might be clinically useful.

Human papillomavirus type 16 variants in paired enrollment and follow-up cervical samples: implications for a proper understanding of type-specific persistent infections

Prospective studies of the persistence of human papillomavirus (HPV) variants are rare and typically small. We sequenced HPV-16 variants in longitudinal pairs of specimens from 86 women enrolled in the ASCUS-LSIL Triage Study. A change of variants was identified in 4 women (4.7% [95% confidence interval, 1.3%-11.5%]). Among women with intervening HPV results (n = 60), a variant switch occurred in 2 of 11 who had evidence of intervening negativity for HPV-16, compared with 1 of 49 who consistently tested positive (P = .11). These results suggest the possibility that rare misclassification of transient infections as persistent infections occurs in natural history studies of type-specific HPV infections.

Hierarchical clustering of human papilloma virus genotype patterns in the ASCUS-LSIL triage study

Anogenital cancers are associated with ∼13 carcinogenic human papilloma virus (HPV) types in a broader group that cause cervical intraepithelial neoplasia (CIN). Multiple concurrent cervical HPV infections are common, which complicates the attribution of HPV types to different grades of CIN. Here we report the analysis of HPV genotype patterns in the atypical squamous cells of undetermined significance-low-grade squamous intraepithelial lesion triage study with the use of unsupervised hierarchical clustering. Women who underwent colposcopy at baseline (n = 2,780) were grouped into 20 disease categories based on histology and cytology. Disease groups and HPV genotypes were clustered with the use of complete linkage. Risk of 2-year cumulative CIN3+, viral load, colposcopic impression, and age were compared between disease groups and major clusters. Hierarchical clustering yielded four major disease clusters: cluster 1 included all CIN3 histology with abnormal cytology; cluster 2 included CIN3 histology with normal cytology and combinations with either CIN2 or high-grade squamous intraepithelial lesion cytology; cluster 3 included older women with normal or low-grade histology/cytology and low viral load; and cluster 4 included younger women with low-grade histology/cytology, multiple infections, and the highest viral load. Three major groups of HPV genotypes were identified: group 1 included only HPV16; group 2 included nine carcinogenic types, plus noncarcinogenic HPV53 and HPV66; and group 3 included noncarcinogenic types, plus carcinogenic HPV33 and HPV45. Clustering results suggested that colposcopy missed a prevalent precancer in many women with no biopsy/normal histology and high-grade squamous intraepithelial lesion. This result was confirmed by an elevated 2-year risk of CIN3+ in these groups. Our novel approach to study multiple genotype infections in cervical disease with the use of unsupervised hierarchical clustering can address complex genotype distributions on a population level.

Behavioral/lifestyle and immunologic factors associated with HPV infection among women older than 45 years

BACKGROUND

Cervical human papilloma virus (HPV) detection increases after menopause, but its determinants need clarification.

METHODS

In a case-control study nested within a 10,049 women cohort, we evaluated women 45 to 75 years old who acquired HPV infection and were HPV positive 5 to 6 years after enrollment (N = 252), and HPV-negative women as matched controls (N = 265). Detailed sexual behavior and cellular immune response were investigated. Odds ratios (OR) and attributable fractions were estimated.

RESULTS

Women with 2+ lifetime partners had 1.7-fold (95% CI = 1.1-2.7) higher risk than monogamous women, with similar findings if their partners had other partners. Women with 2+ partners after last HPV-negative result had the highest risk (OR = 3.9; 95% CI = 1.2-12.4 compared with 0-1 partners). Weaker immune response to HPV-16 virus-like particles increased risk (OR = 1.7; 95% CI = 1.1-2.7 comparing lowest to highest tertile). Among women with no sexual activity in the period before HPV appearance, reduced immune response to phytohemagglutinin was the only determinant (OR = 2.9; 95% CI = 0.94-8.8). Twenty-one percent of infections were explained by recent sexual behavior, 21% by past sexual behavior, and 12% by reduced immune response.

CONCLUSIONS

New infections among older women may result from sexual activity of women and/or their partners or reappearance of past (latent) infections possibly related to weakened immune response.

IMPACT

HPV infections among older women are associated with current and past sexual exposures and possibly with immune senescence. The risk of cancer from these infections is likely to be low but could not be fully evaluated in the context of this study.

Epidemiological study of anti-HPV16/18 seropositivity and subsequent risk of HPV16 and -18 infections

BACKGROUND

Infection with human papillomavirus (HPV) 16 or HPV18 elicits an antibody response, but whether the elicited antibodies protect women against subsequent infection by a homologous HPV type compared with seronegative women is unknown.

METHODS

Study participants were women aged 18-25 years at enrollment in the control group of the ongoing National Cancer Institute-sponsored, community-based, randomized HPV16/18 Costa Rica Vaccine Trial. At enrollment, 2813 participants were negative for cervical HPV16 DNA and 2950 for HPV18 DNA. Women were interviewed regarding sociodemographic data and medical and health history. Medical and pelvic examinations were conducted for all consenting sexually experienced women. Serum samples taken at enrollment were tested for total HPV16/18 antibodies with a polyclonal enzyme-linked immunosorbent assay, and cervical specimens were tested for type-specific HPV DNA over 4 years of follow-up. Using Poisson regression, we compared rate ratios of newly detected cervical HPV16 or HPV18 infection among homologous HPV-seropositive and HPV-seronegative women, adjusting for age, education, marital status, lifetime number of sexual partners, and smoking.

RESULTS

There were 231 newly detected HPV16 infections during 5886 person-years among HPV16-seronegative women compared with 12 newly detected HPV16 infections during 581 person-years among HPV16-seropositive women with the highest HPV16 sero-levels. There were 136 newly detected HPV18 infections during 6352 person-years among HPV18-seronegative women compared with six new infections detected during 675 person-years among HPV18 seropositives with the highest sero-levels. After controlling for risk factors associated with newly detected HPV infection, having high HPV16 antibody titer at enrollment was associated with a reduced risk of subsequent HPV16 infection (women in the highest tertile of HPV16 antibody titers, adjusted rate ratio = 0.50, 95% confidence interval = 0.26 to 0.86 vs HPV16-seronegative women). Similarly, having high HPV18 antibody titer at enrollment was associated with a reduced risk of subsequent HPV18 infection (women in the highest tertile of HPV18 antibody titers, adjusted rate ratio = 0.36, 95% confidence interval = 0.14 to 0.76 vs HPV18-seronegative women).

CONCLUSION

In this study population, having high antibody levels against HPV16 and HPV18 following natural infection was associated with reduced risk of subsequent HPV16 and HPV18 infections.

Determinants of seropositivity among HPV-16/18 DNA positive young women

BACKGROUND

Not all women infected with HPV-16/18 have detectable levels of HPV-16/18 antibodies, those who seroconvert develop low antibody levels, and seroconversion occurs typically several months post-infection. We evaluated determinants of seropositivity among 646 women infected with HPV-16 and/or HPV-18.

METHODS

Data are from the enrollment visit of the NCI-sponsored Costa Rica HPV Vaccine Trial. Sera were tested for HPV-16/18 antibodies by ELISA; cervical specimens were tested for HPV DNA using HC2 and SPF10/LiPA25. Odds ratios (OR) and 95% confidence intervals (CI) were computed.

RESULTS

Among HPV-16/18 DNA positives, seropositivity was 63.0% and 57.5%, respectively. Among HPV-16 DNA positives, seropositivity increased with lifetime number of sexual partners (p-trend = 0.01). Women with abnormal cytology and/or high viral load had a 1.63-2.79-fold increase in the detection of antibodies compared to women with normal cytology/low viral load. Current users of oral contraceptives had a 1.88-fold (95%CI, 1.14-3.09) increased detection of antibodies and current users of injectables had a 3.38-fold (95%CI, 1.39-8.23) increased detection compared to never users. Among HPV-18 DNA positive women, seropositivity was associated with current oral contraceptive use (OR 2.47; 95%CI 1.08-5.65).

CONCLUSIONS

Factors associated with sustained HPV exposure (abnormal cytology, elevated HPV viral load, increasing lifetime partners) were predictive of HPV-16 seropositivity. Hormonal contraceptive use was associated with seropositivity suggesting an effect of hormones on immune responses to HPV. Patterns were less consistent for HPV-18. Follow up of incident HPV infections to evaluate seroconversion and their determinants is needed.

Elevated systemic levels of inflammatory cytokines in older women with persistent cervical human papillomavirus infection

BACKGROUND

Defects in lymphoproliferative responses to mitogens/antigens in women >45 years old with a persistent type-specific human papillomavirus (HPV) infection have been reported.

METHODS

To determine whether these defects were associated with altered cytokine profiles, plasma and peripheral blood mononuclear cell (PBMC) culture supernatants from 50 cases (oversampled for their reduced lymphoproliferative ability) and 50 uninfected controls (oversampled for their robust lymphoproliferative ability) were examined for 24 cytokines using multiplexed bead-based immunoassays and ELISA.

RESULTS

The following plasma cytokines were significantly increased in cases relative to controls (cases versus controls; median pg/mL): interleukin (IL)-6, 393.1 versus 14.5; IL-8, 1,128.5 versus 43.9; tumor necrosis factor-alpha (TNF-alpha), 164.1 versus 9.2; macrophage inflammatory protein-1alpha (MIP-1alpha), 1,368.9 versus 25.5; granulocyte macrophage colony-stimulating factor (GM-CSF), 13.8 versus 7.3; IL-1beta, 8.3 versus 1.6 (all P < 0.0001); and IL-1alpha, 218.2 versus 169.5 (P = 0.02). We focused our analysis on the cytokines IL-6, IL-8, TNF-alpha, and MIP-1alpha due to their high fold change (>10) and highly statistically significant difference between cases and controls. Length of persistence or type of infection (high risk and low risk) did not affect these differences. IL-6, TNF-alpha, and MIP-1alpha levels were also increased in unstimulated PBMC culture supernatants from cases compared with controls (P < 0.05), however, the cytokine levels from phytohemagglutinin-stimulated PBMC culture supernatants were significantly lower in the cases (P < 0.0001).

CONCLUSIONS

Persistent HPV infection in older women with evidence of immune deficit is associated with an increase in systemic inflammatory cytokines.

IMPACT

Future studies are needed to determine whether the inflammatory profile is age dependent and to examine the role that inflammatory cytokines play in HPV-induced progression from infection to cervical cancer.

A population-based prospective study of carcinogenic human papillomavirus variant lineages, viral persistence, and cervical neoplasia

Human papillomavirus (HPV) types differ profoundly in cervical carcinogenicity. For the most carcinogenic type HPV16, variant lineages representing further evolutionary divergence also differ in cancer risk. Variants of the remaining 10 to 15 carcinogenic HPV types have not been well studied. In the first prospective, population-based study of HPV variants, we explored whether, on average, the oldest evolutionary branches within each carcinogenic type predicted different risks of >2-year viral persistence and/or precancer and cancer [cervical intraepithelial neoplasia grade 3+ (CIN3+)]. We examined the natural history of HPV variants in the 7-year, 10,049-woman Guanacaste Cohort Study, using a nested case-control design. Infections were assigned to a variant lineage determined by phylogenetic parsimony methods based on URR/E6 sequences. We used the Fisher's combination test to evaluate significance of the risk associations, cumulating evidence across types. Globally, for HPV types including HPV16, the P value was 0.01 for persistence and 0.07 for CIN3+. Excluding HPV16, the P values were 0.04 and 0.37, respectively. For HPV16, non-European viral variants were significantly more likely than European variants to cause persistence [odds ratio (OR), 2.6; P = 0.01] and CIN3+ (OR, 2.4; P = 0.004). HPV35 and HPV51 variant lineages also predicted CIN3+. HPV variants generally differ in risk of persistence. For some HPV types, especially HPV16, variant lineages differ in risk of CIN3+. The findings indicate that continued evolution of HPV types has led to even finer genetic discrimination linked to HPV natural history and cervical cancer risk. Larger viral genomic studies are warranted, especially to identify the genetic basis for HPV16's unique carcinogenicity.

Risk of miscarriage with bivalent vaccine against human papillomavirus (HPV) types 16 and 18: pooled analysis of two randomised controlled trials

OBJECTIVE

To assess whether vaccination against human papillomavirus (HPV) increases the risk of miscarriage.

DESIGN

Pooled analysis of two multicentre, phase three masked randomised controlled trials

SETTING

Multicentre trials in several continents and in Costa Rica.

PARTICIPANTS

26 130 women aged 15-25 at enrolment; 3599 pregnancies eligible for analysis.

INTERVENTIONS

Participants were randomly assigned to receive three doses of bivalent HPV 16/18 VLP vaccine with AS04 adjuvant (n=13 075) or hepatitis A vaccine as control (n=13 055) over six months.

MAIN OUTCOME MEASURES

Miscarriage and other pregnancy outcomes.

RESULTS

The estimated rate of miscarriage was 11.5% in pregnancies in women in the HPV arm and 10.2% in the control arm. The one sided P value for the primary analysis was 0.16; thus, overall, there was no significant increase in miscarriage among women assigned to the HPV vaccine arm. In secondary descriptive analyses, miscarriage rates were 14.7% in the HPV vaccine arm and 9.1% in the control arm in pregnancies that began within three months after nearest vaccination.

CONCLUSION

There is no evidence overall for an association between HPV vaccination and risk of miscarriage.

TRIAL REGISTRATION

Clinical Trials NCT00128661 and NCT00122681.

Relationship between cigarette smoking and human papilloma virus types 16 and 18 DNA load

BACKGROUND

Although cigarette smoking has been associated with increased human papilloma virus (HPV) detection, its impact on HPV DNA load is unknown.

METHODS

The study subjects were women who were positive for HPV16 and/or HPV18 at enrollment into the Atypical Squamous Cells of Undetermined Significance-Low-grade Squamous Intraepithelial Lesion Triage Study. Assessments of exposure to smoke and sexual behavior were based on self-report. Viral genome copies per nanogram of cellular DNA were measured by multiplex real-time PCR. Linear or logistic regression models were used to assess the relationship between cigarette smoking and baseline viral load.

RESULTS

Of the 1,050 women (752 with HPV16, 258 with HPV18, and 40 with both HPV16 and HPV18), 452 (43.0%) were current smokers and 101 (9.6%) were former smokers at enrollment. The baseline viral load was statistically significantly greater for current compared with never smokers (P = 0.03 for HPV16; P = 0.02 for HPV18) but not for former smokers. Among current smokers, neither HPV16 nor HPV18 DNA load seemed to vary appreciably by age at smoking initiation, smoking intensity, or smoking duration. The results remained similar when the analysis of smoking-related HPV16 DNA load was restricted to women without detectable cervical abnormality.

CONCLUSION

Higher baseline HPV16 and HPV18 DNA load was associated with status as a current but not former smoker. A lack of dose-response relationship between cigarette smoking and viral load may indicate a low threshold for the effect of smoking on HPV DNA load.

Longitudinal study of human papillomavirus persistence and cervical intraepithelial neoplasia grade 2/3: critical role of duration of infection

BACKGROUND

The natural history of human papillomavirus (HPV) infections in older women is critical for preventive strategies, including vaccination and screening intervals, but is poorly understood. In a 7-year population-based cohort study in Guanacaste, Costa Rica, we examined whether women's age and the duration of carcinogenic HPV infections influenced subsequent persistence of infection and risk of cervical intraepithelial neoplasia grade 2 (CIN 2) or worse disease.

METHODS

At enrollment, of the 9466 participants eligible for pelvic examination, 9175 were screened for cervical neoplasia using multiple methods; those with CIN 2 or worse disease were censored and treated. Participants at low risk of CIN 2 or worse (n = 6029) were rescreened at 5-7 years (passively followed), whereas higher-risk participants (n = 2115) and subsets of low-risk women (n = 540) and initially sexually inactive women (n = 410) were rescreened annually or semiannually (actively followed) for up to 7 years. HPV testing was done using a polymerase chain reaction-based method. We determined, by four age groups (18-25, 26-33, 34-41, and > or =42 years), the proportion of prevalent infections (found at baseline) and newly detected infections (first found during follow-up) that persisted at successive 1-year time points and calculated absolute risks of CIN 2 and CIN grade 3 (CIN 3) or worse during follow-up. P values are two-sided.

RESULTS

Regardless of the woman's age, newly detected infections were associated with very low absolute risks of persistence, CIN 2, or worse disease. For newly detected infections, the rate of progression to CIN 2+ (or CIN 3+), after 3 years of follow-up, was not higher for women aged 34 years and older than for younger women. Moreover, rates of newly detected infections declined sharply with age (in the actively followed group, at ages 18-25, 26-33, 34-41, and > or =42 years, rates were 35.9%, 30.6%, 18.1%, and 13.5%, respectively; P < .001). Among prevalent infections, persistent infections among older women (> or =42 years) was higher than that among younger age groups or new infections at any age (P < .01 for comparison of eight groups). Most (66 of 85) CIN 2 or worse detected during follow-up was associated with prevalent infections. Only a small subset (25 of 1128) of prevalent infections persisted throughout follow-up without apparent CIN 2 or worse.

CONCLUSIONS

The rate of new infections declines with age, and new infections typically do not progress to CIN 2 or worse disease in older women; thus, overall potential benefit of prophylactic vaccination or frequent HPV screening to prevent or detect new carcinogenic HPV infections at older ages is low.

Predictors of human papillomavirus persistence among women with equivocal or mildly abnormal cytology

We investigated short-term persistence of human papillomavirus (HPV) infection among 2,408 women with low-grade or equivocal cytological abnormalities followed for 24 months. Odds ratios (ORs) for persistence to the next 6-month visit were estimated by a discrete time survival model. Prevalent HPV infections persisted longer in older women, but no association with age was found for incident HPV infections. Increased likelihood of persistence was found among current smokers of >20 cigarettes per day compared with smokers of <or=10 cigarettes per day (OR=1.43; 95% confidence interval [CI]: 1.02-2.01) and among current injectable contraceptive users (OR=1.15; 95% CI: 1.01-1.32). Persistence was more likely among infections with higher viral load (OR=2.05; 95% CI: 1.65-2.53) or with concurrent cytological abnormalities (OR=1.19; 95% CI: 1.03-1.39 and 1.29; 95% CI: 0.99-1.70 for ASCUS/LSIL and ASC-H/HSIL, respectively). We conclude that new HPV infections in older women are not riskier by the metric of viral persistence than those in younger women. Other risk factors such as oral contraceptive use and multiparity that have been associated with cervical cancer or cervical intraepithelial neoplasia grade 3 were not associated with short-term HPV persistence.

Impact of improved classification on the association of human papillomavirus with cervical precancer

Misclassification of exposure and surrogate endpoints of disease can obscure causal relations. Using data from the Atypical Squamous Cells of Undetermined Significance/Low-Grade Squamous Intraepithelial Lesion Triage Study (ALTS, 1997-2001), the authors explored the impact of exposure (human papillomavirus (HPV) detection) and endpoint (histologic cervical precancer) classification on their mutual association. Women referred into this study with an atypical squamous cells of undetermined significance Papanicolaou test with satisfactory results for all 4 HPV tests were included in this analysis (n = 3,215; 92.2%). HPV testing results were related to different definitions of cervical precancer, based on paired, worst 2-year histologic diagnoses, by calculating clinical sensitivity, specificity, and odds ratios. The authors found that HPV test sensitivity increased and specificity decreased with increasing certainty of cervical precancer, with HPV testing having the highest sensitivity (92%-98%) and lowest specificity (46%-54%) for consensus cervical intraepithelial neoplasia grade 3 (CIN 3). The overall accuracy of each HPV test, as measured by odds ratios, was greatest for consensus CIN-3 diagnoses, from 2- to 4-fold greater than for a less stringent precancer definition of any diagnosis of CIN 2 or more severe. In summary, there was convergence of greater certainty of carcinogenic HPV with greater certainty of a precancerous diagnosis, such that all 4 HPV tests almost always tested positive in women most likely to have cervical precancer. Finding increasingly strong associations when both test and diagnostic misclassification are reduced is a useful sign of "true association" in molecular epidemiology.

Common genetic variants and risk for HPV persistence and progression to cervical cancer

HPV infrequently persists and progresses to cervical cancer. We examined host genetic factors hypothesized to play a role in determining which subset of individuals infected with oncogenic human papillomavirus (HPV) have persistent infection and further develop cervical pre-cancer/cancer compared to the majority of infected individuals who will clear infection.

We evaluated 7140 tag single nucleotide polymorphisms (SNPs) from 305 candidate genes hypothesized to be involved in DNA repair, viral infection and cell entry in 416 cervical intraepithelial neoplasia 3 (CIN3)/cancer cases, 356 HPV persistent women (median: 25 months), and 425 random controls (RC) from the 10,049 women Guanacaste Costa Rica Natural History study. We used logistic regression to compute odds ratios and p-trend for CIN3/cancer and HPV persistence in relation to SNP genotypes and haplotypes (adjusted for age). We obtained pathway and gene-level summary of associations by computing the adaptive combination of p-values. Genes/regions statistically significantly associated with CIN3/cancer included the viral infection and cell entry genes 2′,5′ oligoadenylate synthetase gene 3 (OAS3), sulfatase 1 (SULF1), and interferon gamma (IFNG); the DNA repair genes deoxyuridine triphosphate (DUT), dosage suppressor of mck 1 homolog (DMC1), and general transcription factor IIH, polypeptide 3 (GTF2H4); and the EVER1 and EVER2 genes (p<0.01). From each region, the single most significant SNPs associated with CIN3/cancer were OAS3 rs12302655, SULF1 rs4737999, IFNG rs11177074, DUT rs3784621, DMC1 rs5757133, GTF2H4 rs2894054, EVER1/EVER2 rs9893818 (p-trends≤0.001). SNPs for OAS3, SULF1, DUT, and GTF2H4 were associated with HPV persistence whereas IFNG and EVER1/EVER2 SNPs were associated with progression to CIN3/cancer. We note that the associations observed were less than two-fold. We identified variations DNA repair and viral binding and cell entry genes associated with CIN3/cancer. Our results require replication but suggest that different genes may be responsible for modulating risk in the two critical transition steps important for cervical carcinogenesis: HPV persistence and disease progression.

Lack of heterogeneity of HPV16 E7 sequence compared with HPV31 and HPV73 may be related to its unique carcinogenic properties

To assess the role of human papillomavirus virus (HPV) genetics in cervical lesions, we sequenced the E7 gene of HPV16, 31, or 73 from singly infected women who (1) cleared the infection quickly, (2) had type-specific persistent infection, or (3) progressed to CIN2 or worse lesions. Four of the 296 HPV16 E7 nucleotides were variable, compared with 7 of 296 for HPV31 E7 and 4 of 296 for HPV73 E7. While most of the polymorphisms in HPV31 and -73 resulted in non-synonymous amino acid changes, the polymorphisms in the HPV16 E7 resulted in synonymous changes. The lack of heterogeneity of HPV16 E7 suggests high evolutionary purifying selection that might be related to the unique carcinogenicity of HPV16.

Human Papillomavirus (HPV) type 16 and type 18 DNA Loads at Baseline and Persistence of Type-Specific Infection during a 2-year follow-up

BACKGROUND

Studies of viral load-associated persistence of human papillomavirus (HPV) infection are rare, with inconsistent results reported.

METHODS

The study subjects were 741 and 289 women who were positive for HPV type 16 (HPV-16) and HPV type 18 (HPV-18), respectively, at the time of enrollment into in the ASCUS-LSIL (Atypical Squamous Cells of Undetermined Significance-Low-Grade Squamous Intraepithelial Lesion) Triage Study and who returned 1 or more times for HPV testing during a biannual 2-year follow-up. The numbers of HPV-16 and HPV-18 copies per nanogram of cellular DNA at baseline were measured by use of real-time polymerase chain reaction.

RESULTS

Women with, compared with women without, persistent infection at month 6 of follow-up had a higher viral load at enrollment (P< .001, for HPV-16; P=.01, for HPV-18). The association of each 1-log(10) increase in viral load with persistence of HPV-16 or HPV-18 during the first 6 months of the study was statistically significant among women with multiple HPV types at enrollment (for HPV-16: odds ratio [OR], 1.53 [95% confidence interval {CI}, 1.29-1.82]; for HPV-18: OR, 1.35 [95% CI, 1.09-1.68]) but not among women with monotype infections (in tests assessing the interaction between viral load and coinfection, P=.002 for HPV-16 and P=.34 for HPV-18). Among women who continued to have positive results at month 6, 12, or 18, persistence of infection for another 6 months was unassociated with the viral load at baseline.

CONCLUSION

Prevalent infection with a higher viral load of HPV-16 or HPV-18 was associated with short- but not long-term persistence.