Declining prevalence of cervicovaginal human papillomavirus infection with age is independent of other risk factors

Chapter 2: Natural history of anogenital human papillomavirus infection and neoplasia

This chapter suggests promising areas of future epidemiologic research on human papillomavirus (HPV) and anogenital cancer, organized around our understanding of cervical carcinogenesis. The major steps in cervical carcinogenesis include HPV infection, HPV persistence over a certain period of time, progression to precancer, and invasion. Backward steps include clearance of HPV infection and regression of precancer. Additional studies of incident HPV infections among virgins initiating sexual activity could clarify the earliest aspects of transmission and immune response. Research on older women and their male partners should focus on understanding the determinants of varying age-specific HPV prevalence curves and underlying dynamics of viral persistence, clearance, and latency. It will be particularly important for epidemiologists to define HPV persistence rigorously in order to guide clinical management and vaccine trials. Intensive longitudinal studies that collect visual, microscopic (cytologic and histologic), and molecular data will be needed to understand the fate of individual HPV infections and to clarify whether multiple, concurrent infections act independently on the cervix. Case-control designs will be useful mainly in searching for new biomarkers of risk of progression among HPV-infected women that could then be validated prospectively. Prospective confirmation is also needed for the etiologic cofactors established by case-control studies of invasive cervical cancer. Much of the knowledge about cervical cancer might apply to anal neoplasia. Epidemiologic studies of other genital tumors such as penile neoplasia are still needed, but multicentric groups must place great emphasis on measurement technology, given the difficulty in obtaining reliable comprehensive measurements.

A comprehensive natural history model of HPV infection and cervical cancer to estimate the clinical impact of a prophylactic HPV-16/18 vaccine

The object of our study is to project the impact of a prophylactic vaccine against persistent human papillomavirus (HPV)-16/18 infection on age-specific incidence of invasive cervical cancer. We developed a computer-based mathematical model of the natural history of cervical carcinogenesis to incorporate the underlying type-specific HPV distribution within precancerous lesions and invasive cancer. After defining plausible ranges for each parameter based on a comprehensive literature review, the model was calibrated to the best available population-based data. We projected the age-specific reduction in cervical cancer that would occur with a vaccine that reduced the probability of acquiring persistent infection with HPV 16/18, and explored the impact of alternative assumptions about vaccine efficacy and coverage, waning immunity and competing risks associated with non-16/18 HPV types in vaccinated women. The model predicted a peak age-specific cancer incidence of 90 per 100,000 in the 6th decade, a lifetime cancer risk of 3.7% and a reproducible representation of type-specific HPV within low and high-grade cervical precancerous lesions and cervical cancer. A vaccine that prevented 98% of persistent HPV 16/18 was associated with an approximate equivalent reduction in 16/18-associated cancer and a 51% reduction in total cervical cancer; the effect on total cancer was attenuated due to the competing risks associated with other oncogenic non-16/18 types. A vaccine that prevented 75% of persistent HPV 16/18 was associated with a 70% to 83% reduction in HPV-16/18 cancer cases. Similar effects were observed with high-grade squamous intraepithelial lesions (HSIL) although the impact of vaccination on the overall prevalence of HPV and low-grade squamous intraepithelial lesions (LSIL) was minimal. In conclusion, a prophylactic vaccine that prevents persistent HPV-16/18 infection can be expected to significantly reduce HPV-16/18-associated LSIL, HSIL and cervical cancer. The impact on overall prevalence of HPV or LSIL, however, may be minimal. Based on the relative importance of different parameters in the model, several priorities for future research were identified. These include a better understanding of the heterogeneity of vaccine response, the effect of type-specific vaccination on other HPV types and the degree to which vaccination effect persists over time.

Prevalence of human papillomavirus infection among women in Concordia, Argentina: a population-based study

BACKGROUND

Preparing for HPV vaccine programs, studies are needed of HPV infection in different populations.

GOAL

The goal was to evaluate HPV prevalence and determinants in Concordia, Argentina.

STUDY DESIGN

A stratified random sample of 1786 households was obtained. Consenting women aged > or =15 years were interviewed and underwent examination, including colposcopy. Cells were collected for a Papanicolaou smear and HPV DNA testing with GP5+/6+ primer-mediated PCR-EIA.

RESULTS

PCR was performed on specimens from 987 women. Prevalence among women reporting no previous sexual activity was 3%, and among sexually active women it was 17.7%, peaking at <25 years of age and decreasing to a minimum at > or =65 years of age. However, low-risk types had similar prevalence (approximately 5%) in all age groups. HPV16 (4.0%), HPV35 (2.6%), and other high-risk types were the most common. Almost half of infections were multiple. Younger women initiated sexual activity earlier and had more partners. The main determinants of HPV detection were lifetime number of sex partners and vaginal discharge.

CONCLUSION

A clear pattern of decreasing prevalence of HPV with age was observed. This could be explained by development of immunity against specific types over time or related to a cohort effect associated with a recent spread of HPV in this population after recent changes in sexual behavior.

Occurrence of cervical infection with multiple human papillomavirus types is associated with age and cytologic abnormalities

BACKGROUND

Few aspects of the occurrence of infections with multiple HPV types have been described. Since the immunity conferred by vaccines is type-specific, the epidemiology of such coinfections needs to be addressed.

GOAL

The goal of the study was to document the prevalence and incidence of infection with multiple HPV types and the distribution of HPV types in coinfections.

STUDY DESIGN

In a prospective cohort of 2075 Brazilian women, cervical specimens were collected for cytology and HPV detection. Information on potential risk factors was obtained by interview.

RESULTS

The prevalence of HPV coinfections was 3% among cytologically normal women, 10% among women with ASCUS, 23% among those with LSIL, and 7% among those with HSIL. The incidence rate of coinfection declined markedly with age (Ptrend<0.001). Some HPV types co-occurred less frequently than expected, namely, HPV 16 and 18 occurring with other oncogenic HPV types and HPV 6/11.

CONCLUSION

We have observed that occurrence of HPV coinfection was dependent both on age and on the presence of cytologic abnormalities. These results may have implications for vaccine development and for public health decisions about vaccination programs.

Histologic findings from the cervix among older women with abnormal cervical cytology

OBJECTIVE

The aim of this study was to determine rates of cervical neoplasia among women at least 50 years of age referred for colposcopy after abnormal cytology and to compare these to younger women.

METHODS

From a prospectively accrued database of 2825 women undergoing colposcopy in the gynecology clinic of an urban public hospital, women at least 50 years of age with a known cytologic abnormality were selected for retrospective analysis. Demographic and medical information collected at colposcopy and subsequent histology was reviewed. Cytology results were based on the Bethesda system, and histology was reported as grades of cervical intraepithelial neoplasia (CIN). Statistical analysis was by t test, chi(2) test, and Mann-Whitney U test.

RESULTS

Among 325 women at least age 50, cervical histologic results were benign or atypical for 147 (45%), CIN1 for 28 (9%), CIN2 for 21 (6%), CIN3 for 49 (15%), cancer for 11 (3%), and ungraded dysplasia for 7 (2%), with no biopsy performed for 62 (19%) women. Symptoms were more common among women with cancer (6/11 or 55%) than those without (62/263 or 21%, P = 0.01). Negative histology (80/231 or 35%), CIN3 (49/231 or 21%), and cancer (9/231 or 4%) were more common among older than younger women (287/1403 or 20%, 199/1403 or 14%, and 11/1403 or 1%, respectively), while atypia (438/1403 or 31%), CIN1 (321/1403 or 23%), and CIN2 (147/1403 or 10%) were more common among younger than older women (53/231 or 23%, 23/231 or 10%, and 17/231 or 7%, respectively, P < 0.04). Differences in the distribution of cervical histology results remained significant among women with ASCUS (P = 0.001) but not those with LSIL (P > 0.9), HSIL (P > 0.07), or cancer (P > 0.4).

CONCLUSIONS

Most older women are referred for colposcopy with lesser grades of abnormality, but cervical cancers are found across all cytologic grades and were more common in symptomatic women. Compared to younger women with abnormal cytology, women at least 50 years of age with ASCUS had higher rates of negative evaluations and high grade but not low- or mid-grade lesions.

Repetitive and consistent cervicovaginal exposure to certain viral pathogens appears to protect against their sexual acquisition in some women: potential mechanisms

Several groups have proposed that human female promiscuity or polyandry, with repetitive and consistent cervicovaginal exposure to human immunodeficiency virus type 1 (HIV-1), can lead to protection against sexual acquisition of HIV-1 in some of these women. The mechanism of this phenomenon, the highly exposed persistently HIV-seronegative (HEPS) state, is unknown. Thus far, it has been correlated with viral epitope-specific immune responses in only about half of the women evaluated. But when present, these responses decline rapidly following interruption of pathogen exposure, and correlate with prompt acquisition of HIV. I have extended the concept of HEPS to another sexually transmitted viral pathogen, human papillomavirus (HPV). Supporting clinical and immunological information were identified from a literature search using PubMed as well as several sets of epidemiological data, including longitudinal surveys of HIV-1 incidence among female commercial sex workers (CSWs) in Africa and Thailand, and follow-up of a Danish cohort of CSWs and a large group of Brazilian women, both at high risk for HPV infection. These studies suggest that male-to-female penile-vaginal transmission of at least two viruses, HIV-1 and HPV, is blocked by local mucosal responses, immunologic or otherwise, which require repetitive, uninterrupted exposure to pathogen. Exploration of the mechanisms underlying such ostensibly protective responses may facilitate development of STD vaccines.

Can cervical cancer screening be stopped at 50? The prevalence of HPV in elderly women

Although the relation between cervical cancer and the human papillomavirus (HPV) has been established beyond doubt, the introduction of HPV detection in cervical cancer screening is halted, primarily by the high rate of false positivity in relation to morbidity, since the majority of women infected with HPV will not develop lesions. To counteract overconsumption of cervical cancer screening in elderly women, we wanted to test the hypothesis that women of 50 years or older who are HPV-negative and have a cytologically normal smear might be encouraged to refrain from further screening. As a first step, the prevalence of high-risk HPV in a population of 1,936 women of 50 years and older was investigated. After an initial decline, a slightly higher prevalence can be seen with increasing age. There is a decrease in the prevalence of multiple infections with age, paralleled by an increase in single infections, especially of HPV type 16 in the eldest-age group. However, neither the decrease in multiple infections nor the increase in single infections is statistically significant. The data obtained in this study show that, even in the presence of a slight increase in the HPV prevalence in elderly women, approximately 94% of the elderly women can be withdrawn from the cervical cancer screening. However, a follow-up study will be necessary to determine the frequency of (re)infection as well as the course of an HPV infection in elderly women.

Baseline cytology, human papillomavirus testing, and risk for cervical neoplasia: a 10-year cohort analysis

BACKGROUND

Annual Pap smear screening has been favored over less frequent screening in the United States to minimize the risk of cervical cancer. We evaluated whether simultaneous screening with a Pap test and human papillomavirus (HPV) testing is useful for assessing the risk for cervical intraepithelial neoplasia (CIN) 3 or cervical cancer.

METHODS

We enrolled 23 702 subjects in a study of HPV infection at Kaiser Permanente, Northwest Division, Portland, OR. Data were analyzed for 20 810 volunteers who were at least 16 years old (mean = 35.9 years) with satisfactory baseline Pap tests and suitable samples for HPV testing. Women were followed for up to 122 months (from April 1, 1989, to June 30, 1999) to determine the risk for histopathologically confirmed CIN3 or cancer.

RESULTS

Among 171 women with CIN3 or cancer diagnosed over 122 months, 123 (71.9%, 95% confidence interval [CI] = 65.2% to 78.7%) had baseline Pap results of atypical squamous cells or worse and/or a positive HPV test, including 102 (86.4%, 95% CI = 80.3% to 92.6%) of the 118 cases diagnosed within the first 45 months of follow-up. During this 45-month period, the cumulative incidence of CIN3 or cancer was 4.54% (95% CI = 3.61% to 5.46%) among women with a Pap test result of atypical squamous cells or worse, positive HPV tests, or both compared with 0.16% (95% CI = 0.08% to 0.24%) among women with negative Pap and HPV tests. Age, screening behavior, a history of cervical cancer precursors, and a history of treatment for CIN minimally affected results.

CONCLUSIONS

Negative baseline Pap and HPV tests were associated with a low risk for CIN3 or cancer in the subsequent 45 months, largely because a negative HPV test was associated with a decreased risk of cervical neoplasia. Negative combined test results should provide added reassurance for lengthening the screening interval among low-risk women, whereas positive results identify a relatively small subgroup that requires more frequent surveillance.

Human papillomavirus and cervical cancer

Of the many types of human papillomavirus (HPV), more than 30 infect the genital tract. The association between certain oncogenic (high-risk) strains of HPV and cervical cancer is well established. Although HPV is essential to the transformation of cervical epithelial cells, it is not sufficient, and a variety of cofactors and molecular events influence whether cervical cancer will develop. Early detection and treatment of precancerous lesions can prevent progression to cervical cancer. Identification of precancerous lesions has been primarily by cytologic screening of cervical cells. Cellular abnormalities, however, may be missed or may not be sufficiently distinct, and a portion of patients with borderline or mildly dyskaryotic cytomorphology will have higher-grade disease identified by subsequent colposcopy and biopsy. Sensitive and specific molecular techniques that detect HPV DNA and distinguish high-risk HPV types from low-risk HPV types have been introduced as an adjunct to cytology. Earlier detection of high-risk HPV types may improve triage, treatment, and follow-up in infected patients. Currently, the clearest role for HPV DNA testing is to improve diagnostic accuracy and limit unnecessary colposcopy in patients with borderline or mildly abnormal cytologic test results.

Human papillomavirus and cervical neoplasia

Cervical cancer accounts for about 10% of all newly diagnosed cancers in women worldwide. The association between HPV infection and cervical neoplasia appears to be stronger than the association between smoking and lung cancer. At least 20 oncogenic HPV types have been identified in > 95% of preinvasive and invasive cervical cancers, HPV type 16 being the most common. HPV detection is important to identify those patients who may be at high risk for the development of cervical neoplasia. Detection techniques include Hybrid Capture (Digene, Silver Springs, MD) and PCR. Viral integration appears to be one of the necessary steps in malignant transformation. Recently, some of the repeated chromosomal alterations and patterns of integration sites have been identified in cervical cancer specimens. The low rate of HPV-negative cancers implies an effective HPV vaccine might have the ability to eradicate cervical cancer worldwide.

The status of HPV16-specific T-cell reactivity in health and disease as a guide to HPV vaccine development

Human papilloma viruses (HPV) are among the most common sexually transmitted pathogens in young adults. In the majority of individuals, anti-viral immunity is capable of suppressing viral infection but in a minority of patients viral infection is not cleared in time to prevent the development of malignancies. In these cases, HPV16-specific immunity may develop too late, is not strong enough, and/or is possibly of the wrong type. The influence of pre-existing immunity on the efficacy of vaccines is largely unknown. Nor has it been studied what the effect is of vaccines on the various types of pre-existing HPV-specific T-cell immunity. Animal models showing that vaccines are able to protect against a subsequent tumor challenge and even to treat transplantable tumors, are not qualified to address this point because tumor development is not preceded by persistent viral infection. Therefore, the comparison between fully characterized pre-existing HPV-specific immunity in patients and healthy subjects is a prerequisite for the full appreciation of vaccine-efficacy as well as for further development of next-generation vaccines.

Risk factors for genital HPV DNA in men resemble those found in women: a study of male attendees at a Danish STD clinic

OBJECTIVES

Genital infection with certain types of human papillomavirus (HPV) is the most important risk factor for cervical cancer. The male sexual partner is supposed to be the vector of the infection. However, the knowledge of risk factors for genital HPV DNA in men is limited. The objective of this paper is to study the risk factors for HPV infection in men and to compare them with those found in women, including the study of whether there are different risk profiles for oncogenic and non-oncogenic HPV types.

METHODS

From a sexually transmitted diseases (STD) clinic in Denmark, 216 men were consecutively included. A personal interview was done and material for genital HPV DNA detection was obtained with swabs. HPV DNA was detected by polymerase chain reaction (PCR). Odds ratios (OR) for HPV as well as for oncogenic and non-oncogenic types separately were computed with a 95% confidence interval (CI) by means of unconditional multiple logistic regresssion.

RESULTS

The most important predictors of any HPV were lifetime number of sex partners (OR = 4.3; 95% CI 1.4 to 13.1 for 25-39 v 1-9 partners), young age, and being uncircumcised. The most important risk factor for oncogenic HPV types was lifetime number of partners, whereas number of partners in the past year and ever having genital warts were risk factors for the non-oncogenic HPV types. Young age predicted risk of both oncogenic and non-oncogenic HPV types.

CONCLUSIONS

Most risk factors for HPV DNA detection in men resemble those found in women. As in women, the risk factor profile for the oncogenic HPV types was different from that of the non-oncogenic HPV types.

Pap test results among low-income youth: prevalence of dysplasia and practice implications

OBJECTIVES

To describe Papanicolaou (Pap) test findings and identify prevalence and correlates of dysplastic cervical abnormalities in low-income adolescent females.

DESIGN AND SETTING

This cross-sectional study included a modified random sample of female students ages 16 to 25 years at 54 U.S. Job Corps centers.

PARTICIPANTS

5,734 female students enrolled in a federal job training program. Admission health records were reviewed and abstracted.

MAIN OUTCOME MEASURE

Pap test findings using the Bethesda classifications. Pap smear results indicating dysplasia (atypical squamous cells of undetermined significance [ASCUS] with dysplasia) or squamous intraepithelial lesions (low-grade squamous interepithelial lesions [LGSIL] or high-grade squamous intraepithelial lesions [HGSIL]). Participants with less severe findings were compared with those who needed follow-up.

RESULTS

For 71.4% of participants, no abnormalities were found. 15.6% had benign cellular changes, 9.2% had reactive changes, and 9.9% had epithelial cell abnormalities. Of those tested, 5.6% (+/- 0.8%) had dysplastic Pap smear findings, with 0.3% (n = 12) HGSIL. All groups were equally affected, with abnormalities not associated with race/ethnicity, age, geographic region, education level, size of city of residence, or receiving public assistance.

CONCLUSIONS

In this population, dysplastic Pap smear results were not uncommon. Findings indicate that Pap screening, alone or in combination with more sensitive tests, can identify cervical abnormalities, including HGSIL, that suggest a need for further evaluation or follow-up.

Characterization of genital human papillomavirus infection in women who have or who are at risk of having HIV infection

OBJECTIVE

The purpose of this study was to describe the prevalence of human papillomavirus infection and the likelihood of human papillomavirus expression and Papanicolaou test abnormalities among women who have and who are at risk of having human immunodeficiency virus infection.

STUDY DESIGN

Cross-sectional analysis of 767 women who had human immunodeficiency virus infection and 390 women who were at risk of having human immunodeficiency virus infection in 4 cities in the United States.

RESULTS

Women who were infected with human immunodeficiency virus were more likely than women who were not infected to have human papillomavirus infection (prevalence ratio, 2.3; 95% CI, 2.0-2.8) but had similar human papillomavirus types. Among women who tested positive for human papillomavirus by polymerase chain reaction, human immunodeficiency virus infection was associated with a high level of human papillomavirus expression (prevalence ratio, 1.3-1.6) and multiple human papillomavirus infections (prevalence ratio, 1.9). However, among women with a high level of human papillomavirus expression or infection with multiple types, there was no association between human immunodeficiency virus serostatus and risk of cervical dysplasia.

CONCLUSION

Through its association with a high level of expression and multiple human papillomavirus infections, human immunodeficiency virus infection may increase the risk of cervical dysplasia in women who are infected with human papillomavirus.

The effect of highly active antiretroviral therapy on cervical cytologic changes associated with oncogenic HPV among HIV-infected women

OBJECTIVE

Cervical intraepithelial neoplasia (CIN), a common condition among HIV-infected women, has been linked to HIV load and immune status. Highly active antiretroviral therapy (HAART) improves immunologic and virologic status. This study was undertaken to determine the relationship between HAART use and CIN.

DESIGN

Cohort study. The Women's Interagency HIV Study (WIHS) in five cities in the USA (Bronx/Manhattan, New York; Brooklyn, New York; Chicago, Illinois; Los Angeles, California; San Francisco Bay area, California; Washington, District of Columbia).

METHODS

HIV-infected women were followed every 6 months with Papanicolaou smears and cervicovaginal lavage for human papillomavirus (HPV) DNA testing. To characterize exposures that changed over time and to capture the dynamic nature of cytologic changes, Papanicolaou smear findings from each participant's consecutive visits were defined as a pair. We determined the proportion of all pairs that exhibited either regression or progression, according to HAART exposure, HPV results and Papanicolaou smear status. As participants could contribute multiple pairs, inferences were based on robust methods to adjust for correlated observations.

RESULTS

Women with persistent HPV infection were more likely to have progression of their lesions. After adjustment for CD4 cell count and Papanicolaou smear status, women on HAART were 40% (95% confidence interval, 4-81%) more likely to demonstrate regression and less likely (odds ratio, 0.68; 95% confidence interval, 0.52-0.88) to demonstrate progression

CONCLUSIONS

HAART altered the course of HPV disease in HIV-infected women, reducing progression and increasing regression. As HPV disease is a common sex-specific manifestation of HIV disease this effect of HAART would be a major additional benefit from this modality of therapy.

The prognostic significance of acetowhitening of the vulva and HPV-DNA test. A multicentre study

Acetowhitening of the vulva has been related to a subclinical human papillomavirus (HPV) infection. No consense has been reached about undertaking -or not- any therapy for these acetowhite changes. We have observed from our clinical experience and in a 10 years observational follow-up, that acetowhitening of the vulva regarding high risk (16-18) and low risk (6-11) HPV groups (as assessed by PCR analysis) significantly decreased; and acetowhitening areas negative to polymerase chain reaction (PCR), significantly increased from 53% (202/382) to 85% (276/325) (P<0.001). Our findings suggest that independently from HPV type and in the absence of cofactors, there is a statistically significant spontaneous remission of these areas.

The relationship of human papillomavirus (HPV) detection to pap smear classification of cervical-scraped cells in asymptomatic women in northeast Thailand

OBJECTIVE

To correlate the detection of human papillomavirus (HPV) with the Pap smear classification of cervical-scraped cells from asymptomatic women living in northeast Thailand.

METHODS

A total of 260 asymptomatic women attending the Obstetrics and Gynecology's Outpatient Clinic, Srinagarind Hospital, Thailand, were interviewed for risk factors and cervical scrapes were taken. The cells were examined by Pap smear for cytological changes and by PCR for HPV DNAs--nononcogenic (HPVs 6 and 11) and oncogenic (HPVs 16, 18 and 33) types. Cervical biopsies were taken from women with abnormal Pap smears for histological examination.

RESULTS

Of the 260 cervical smear samples, the cervical cells were classified as normal and abnormal in 174 and 86, respectively. Twenty-three percent of all samples were positive for overall HPV DNA. HPV DNAs (mostly HPVs 6 and 11) were detected in 21% of normal cells, and the higher detection rate (27%) for HPV DNA in abnormal cells gradually increased in severity from 16% in Class 3 to 35 and 60% in Classes 4 and 5, respectively. Histologically 46, 90 and 100% of HPV detection was associated with CIS, SCC and adenocarcinoma, respectively. Almost all of the HPV DNAs detected were types 16, 18 or 33. There was no significant association between HPV infection and reproduction history, sexual behavior and demographic variables.

CONCLUSION

We speculated that an abnormal Pap smear and the detection of an oncogenic type HPV may indicate the presence of neoplastic cells in asymptomatic woman who might be at risk for the development of cervical cancer.

Human papillomavirus: a highly prevalent sexually transmitted disease agent among female sex workers from Mexico City

BACKGROUND

Cervical cancer, a human papillomavirus (HPV)-caused neoplasia, is highly prevalent in Mexico.

GOAL

To determine the prevalence of HPV infection in female sex workers (FSW) from Mexico City and to assess the association between HPV infection and the characteristics of these women.

STUDY DESIGN

A questionnaire was applied to 495 FSW. Cervical cell specimens were obtained for DNA amplification and hybridization to detect 27 HPV types. A risk factor analysis was performed.

RESULTS

The overall prevalence of HPV infection was 48.9%. The prevalence of high-risk HPV types was 43%, whereas that of low-risk types was 24.6%. A total of 18.8% of study participants was infected with both high-risk and low-risk HPV types, and 28.5% were infected with two or more HPV types. Younger age and failure to use a condom were independently associated HPV risks (odds ratio, 7.3 and 2.3; 95% CI, 3.5-15.0 and 1.2-4.4, respectively).

CONCLUSIONS

Infection with high-risk and multiple HPV types is high among Mexican FSW. This study corroborated a higher infection rate in younger women. A higher risk of HPV infection is also observed in women who have been involved with sex work for less than 1 year. However, condom use showed a protective effect against HPV infection.

Diagnosing human papillomaviruses: recent advances

The biological importance of a group of human papillomaviruses, known as high-risk human papillomaviruses, as the key causal agent for almost all cervical cancer has now been established. Many aspects of the natural history of high-risk human papillomaviruses as sexually transmitted infections and as oncogenic agents have been researched. Although human papillomavirus diagnosis is largely confined to DNA detection techniques in cervical smears, there is accumulating evidence that the best polymerase chain reaction and hybrid capture techniques are more sensitive and probably of similar specificity compared with cervical cytology as a triage test for women with borderline smear abnormalities and for screening older women. This is strong presumptive evidence that high-risk human papillomavirus testing could be useful in cervical screening. Current research is aimed at establishing a place for high-risk human papillomavirus testing in routine screening practice. Randomised clinical trials, long-term natural history studies, mathematical modelling, and economic and psychosocial studies are being used to demonstrate whether this testing can improve both the effectiveness and efficiency of cervical screening in a range of situations.

Prediction of high-grade cervical intraepithelial neoplasia in cytologically normal women by human papillomavirus testing

Human papillomavirus (HPV) testing has been suggested for primary screening of cervical cancer. Prediction of future high-grade cervical lesions is crucial for effectiveness and cost. We performed a case control study in a retrospective cohort of women with at least two cervical smears, all but the last one being negative, from the organized cervical screening programme in Florence, Italy. We searched for high-risk HPV in all previous, archival, smears from cases (new histologically confirmed cervical intraepithelial neoplasia (CIN) grade II or worse) and in one previous smear from each control (last smear cytologically normal, matched by age and interval (latency) from last smear). We applied polymerase chain reaction (PCR), and the b-globin gene was used as a DNA preservation marker. High-risk HPV was identified in 71/92 (77.17%) previous smears from 79 cases and 17/332 controls (5.12%). The odds ratio (OR) was 63.76 (95% CI 30.57-132.96). Among cases the proportion of HPV-positive smears declined slightly with increasing latency. Among cases, HPV was found in 81.24% (95% CI 69.93-88.96%) of smears with latency < 4 years and in 67.80% (95% CI 47.72-82.93%) of those taken at longer intervals, up to 6 years. These findings suggest that testing for high-risk HPV allows predicting 80% of CINII/III 3 years before the cytological diagnosis and two thirds 6 years before. They also suggest that testing women negative for high-risk HPV at longer interval and strictly following-up women who are HPV positive could be an effective strategy for cervical cancer screening.

Population-based study of human papillomavirus infection and cervical neoplasia in rural Costa Rica

BACKGROUND

Human papillomavirus (HPV) is the main cause of cervical neoplasia. Because few population-based studies have investigated the prevalence of type-specific infection in relation to cervical disease, we studied a high-risk population, estimating the prevalence of HPV infection and the risk associated with various HPV types.

METHODS

We screened 9175 women in Guanacaste, Costa Rica, to obtain a referent standard final diagnosis, and tested 3024 women for more than 40 types of HPV with a polymerase chain reaction-based system.

RESULTS

Among women with normal cytology, HPV infections peaked first in women younger than 25 years, and they peaked again at age 55 years or older with predominantly non-cancer-associated types of HPV and uncharacterized HPV types. Low-grade squamous intraepithelial lesions (LSILs) (n = 189) decreased consistently with age. The prevalence of high-grade squamous intraepithelial lesions (HSILs) (n = 128) peaked first around age 30 years and again at age 65 years or older. Seventy-three percent of LSILs were HPV positive, with HPV16 being the predominant type (16% of positive subjects). HPV was found in 89% of HSILs and 88% of cancers, with HPV16 being strongly predominant (51% and 53% of positive subjects). Virtually all HSILs and cancers had cancer-associated HPV types, with high odds ratios (ORs) and attributable fractions around 80%. Risk for HPV16 was particularly high (OR for HSILs = 320, 95% confidence interval [CI] = 97-1000; OR for cancer = 710, 95% CI = 110-4500).

CONCLUSIONS

We confirm the early decline of HPV infection with age but note increased prevalence after menopause, which could be related to a second peak of HSILs, an observation that warrants further investigation. At least 80% of HPVs involved in cervical carcinogenesis in this population have been characterized. Polyvalent vaccines including the main cancer-associated HPV types may be able to prevent most cases of cervical disease in this region.

Asymptomatic penile HPV infection: a prospective study

The occurrence of human papillomavirus (HPV) among males was analysed with the polymerase chain reaction (PCR) method. Penile brush samples were taken once from 147 males attending for a control or for HPV non-related reasons, and consecutive samples were collected from 88 males re-attending the clinic. Of the males attending once, 13% (19/147) were HPV DNA positive and among the re-attenders 14% (12/88) were initially positive as compared with 33% (29/88) who were positive at least at one visit. Totally, 22 different HPV types were detected of which HPV 16 was most common, found in 6.4% (15/235), followed by HPV 42 found in 3.8% (9/235). Among 14 HPV-positive males with at least one follow-up, 7 had persistent infections with at least one HPV type, and transient HPV types were observed in 9; but in 5 of them new types appeared at follow-up. Among sexually-active males subclinical/latent HPV infection is common and repeated sampling increases its prevalence.

Advances in the diagnosis and treatment of human papillomavirus infections

During the past decade, much has been learned about the natural history of HPV. Most infections occur early in one's sexual life. The overwhelming majority of infections are cleared by the host immune system and never present as warts or neoplasia. Certain patient behavior such as smoking, frequent sex with many different partners, other STD infections, especially HIV, and immune-suppressive drugs promote HPV expression and cause persistent infection. Persistent HPV infection is very strongly related to neoplasia. In addition to high-risk HPV types, variant subtypes have been identified that interact with the host immune system to subvert host immunity and encourage viral persistence. New treatment programs rely on drugs that modulate the immune system and disrupt viral persistence. There is a real possibility of HPV vaccines in the future, which may protect the unexposed patient.

University students' knowledge and awareness of HPV

BACKGROUND

The purpose of this study was to evaluate the knowledge, attitudes, and behaviors of university students regarding the human papillomavirus (HPV).

METHODS

A random sample of 500 university students was mailed a self-administered questionnaire that elicited their knowledge and awareness about HPV and compared their knowledge and attitudes with those of other sexually transmitted diseases (STDs). Among the 480 deliverable addresses, 289 students responded (response rate 60%).

RESULTS

Only 37% of respondents had ever heard of HPV, and the median score on a 13-item knowledge scale was only 3. Of seven STDs assessed, respondents indicated they knew the least about HPV and perceived that this STD has received the least educational effort. In multivariate analyses, predictors of lower knowledge and awareness about HPV were male gender and sexual behavior (having multiple partners, not using condoms).

CONCLUSIONS

Despite the high prevalence of HPV among young adults, most students knew very little about this infection. Implementing HPV educational programs and measuring their effectiveness should be a priority.

Cervicovaginal human papillomavirus infection in human immunodeficiency virus-1 (HIV)-positive and high-risk HIV-negative women

BACKGROUND

Human papillomavirus (HPV) infection is associated with precancerous cervical squamous intraepithelial lesions commonly seen among women infected with human immunodeficiency virus-1 (HIV). We characterized HPV infection in a large cohort of HIV-positive and HIV-negative women participating in the Women's Interagency HIV Study to determine the prevalence of and risk factors for cervicovaginal HPV infection in HIV-positive women.

METHODS

HIV-positive (n = 1778) and HIV-negative (n = 500) women were tested at enrollment for the presence of HPV DNA in a cervicovaginal lavage specimen. Blood samples were tested for HIV antibody status, level of CD4-positive T cells, and HIV RNA load (copies/mL). An interview detailing risk factors was conducted. Univariate and multivariate analyses were performed.

RESULTS

Compared with HIV-negative women, HIV-positive women with a CD4+ cell count of less than 200/mm3 were at the highest risk of HPV infection, regardless of HIV RNA load (odds ratio [OR] = 10.13; 95% confidence interval [CI] = 7.32-14.04), followed by women with a CD4+ count greater than 200/mm3 and an HIV RNA load greater than 20,000 copies/mL (OR = 5.78; 95% CI = 4.17-8.08) and women with a CD4+ count greater than 200/mm3 and an HIV RNA load less than 20,000 copies/mL (OR = 3.12; 95% CI = 2.36-4.12), after adjustment for other factors. Other risk factors among HIV-positive women included racial/ethnic background (African-American versus Caucasian, OR = 1.64; 95% CI = 1.19-2.28), current smoking (yes versus no; OR = 1.55; 95% CI = 1.20-1.99), and younger age (age < 30 years versus > or = 40 years; OR = 1.75; 95% CI = 1.23-2.49).

CONCLUSIONS

Although the strongest risk factors of HPV infection among HIV-positive women were indicators of more advanced HIV-related disease, other factors commonly found in studies of HIV-negative women, including racial/ethnic background, current smoking, and age, were important in HIV-positive women as well.

Epidemiology of genital human papillomavirus

Genital human papillomavirus (HPV) infection is the most common sexually transmitted viral infection and the major risk factor for cervical neoplasia worldwide; however, little is still known about the epidemiology and natural history of the disease. Prospective cohort studies currently being conducted will increase our knowledge and understanding of these issues and provide critical information for the formulation of future primary and secondary prevention strategies.

Pap smear screening in an urban STD clinic. Yield of screening and predictors of abnormalities

BACKGROUND

Pap smear screening studies in STD clinics have reported high rates of squamous intraepithelial lesions (SIL); however, there are limited data on levels of unsatisfactory smears of characteristics associated with cytologic abnormalities.

GOAL

To assess the yield to Pap smear screening in an STD clinic and to evaluate the rates of and risk factors for atypia, low-grade SIL (LSIL), and high-grade SIL (HSIL).

STUDY DESIGN

A chart review of the clinic records of women undergoing Pap smear screening between 1991 and 1994 was conducted. Results were assessed from two different screening protocols, the first using a Dacron swab to obtain the endocervical sample and the second using a cytobrush.

RESULTS

Of 2034 Pap smears, 1313 (64.6%) were negative, 202 (9.9%) were unsatisfactory, 257 (12.6%) were atypical, 211 (10.4%) had LSIL, and 51 (2.5%) had HSIL. With the change to the cytobrush protocol, the rate of unsatisfactory smears decreased from 14.4% to 3% (p < 0.001), atypia increased from 10% to 16.7% (p < 0.001), and HSIL rose from 1.7% to 3.7% (p < 0.001). By multivariate analysis, atypia was associated with genital warts (odds ratio (OR) 1.53, 95% confidence interval (CI): 1.16-2.02); LSIL with younger age (p < 0.001, for trend), black race (OR 1.51, 95% CI: 1.08-2.10), genital warts (OR 1.81, 95% CI: 1.33-2.47), and an abnormal appearance of the cervix on examination (OR 2.49, 95% CI: 1.85-3.35); and HSIL with a previous abnormal Pap smear (OR 2.48, 95% CI: 1.08-2.10). Overall, abnormality rates were significantly higher in adolescents (35.5%) than older women (21.7%) (p < 0.01).

CONCLUSIONS

Obtaining satisfactory Pap smears among women undergoing screening in an STD clinic is feasible and cytologic abnormalities are common. These results continue to support the need for Pap smear screening in STD clinics, but the high rates in adolescents, a group in whom the natural history of cytologic abnormalities has not been well-defined, raise questions about the need to develop age-appropriate screening and management strategies.

Risk factors for HPV detection in archival Pap smears. A population-based study from Greenland and Denmark

The most important risk factor for cervical cancer is genital infection with certain types of human papillomavirus (HPV). The presence of HPV was studied in archival smears from a random sample of women living in Greenland (GW) and Denmark (DW) having, respectively, a high risk and an intermediate risk for cervical cancer. Risk factors were also examined of the original 126 Danish and 129 Greenlandic archived smears collected during October and November 1988. 125 were located from each country including all abnormal smears. HPV DNA was isolated from the smears and detected by means of a consensus polymerase chain reaction (PCR) detecting a broad spectrum of genital HPV types. HPV was detected in all the abnormal smears and in 22 and 33% respectively of the cytological normal smears from DW and GW. Risk of HPV was significantly higher in smears from women who started sexual life relatively recently (respectively, < or = 4 and < or = 6 years ago in DW and GW) compared with > or = 10 years ago (adjusted prevalence-OR: 9.3; 95% CI: 2.2-39.2 in DW and 5.9; 95% CI: 1.4-25.3 in GW). Among other important risk factors were age in both areas, lifetime number of sex partners and current smoking in DW and ever and gonorrhoea in GW. This study confirms the usefulness of the method as all abnormal smears were positive and, furthermore, the predictors for HPV presence in the normal smears corroborate with those found in recent studies of HPV in fresh cervical swabs. Thus, this method can be useful for large-scale epidemiological studies of HPV DNA in already sampled material.

A longitudinal study of human papillomavirus carriage in human immunodeficiency virus-infected and human immunodeficiency virus-uninfected women

OBJECTIVE

We sought to determine the relationship of human immunodeficiency virus serostatus to carriage of oncogenic human papillomavirus.

MATERIAL AND METHODS

A total of 268 human immunodeficiency virus-infected and 265 human immunodeficiency virus-uninfected women were seen every 6 months, at which time they had laboratory tests performed including a CD4 count. Human papillomavirus deoxyribonucleic acid was analyzed by polymerase chain reaction. Statistical methods included Kaplan-Meier and Cox's proportional hazard models.

RESULTS

The prevalence at baseline of any human papillomavirus type was 73% and 43% among human immunodeficiency virus-seropositive and seronegative women, respectively (p < 0.0001) and of oncogenic types was 32.5% and 17.0% (p < 0.001). The prevalence of oncogenic human papillomavirus was higher in women with CD4 counts <200 mm3 (p < 0.001). The rate of detection of new oncogenic human papillomavirus per 100 patient years of follow-up in human immunodeficiency virus-seropositive women was almost three times higher than among human immunodeficiency virus-seronegative women (p < 0.01). The rate of loss of an oncogenic human papillomavirus was higher in the human immunodeficiency virus-seronegative women but the difference was not significant. The relative risk of a human immunodeficiency virus-infected woman who did not initially have a specific type of oncogenic human papillomavirus having one detected during follow-up was 6.6 times greater than among human immunodeficiency virus-negative women (p < 0.001).

CONCLUSIONS

Human immunodeficiency virus-seropositive women are more likely to have newly detectable oncogenic types of human papillomavirus at follow-up and to show persistent carriage of oncogenic types of human papillomavirus types. Among human immunodeficiency virus-infected women, those with higher CD4 counts were more likely to have a newly detected oncogenic human papillomavirus during follow-up.

Natural history of cervicovaginal papillomavirus infection in young women

BACKGROUND

Genital human papillomavirus (HPV) infection is highly prevalent in sexually active young women. However, precise risk factors for HPV infection and its incidence and duration are not well known.

METHODS

We followed 608 college women at six-month intervals for three years. At each visit, we collected information about lifestyle and sexual behavior and obtained cervicovaginal-lavage samples for the detection of HPV DNA by polymerase chain reaction and Southern blot hybridization. Pap smears were obtained annually.

RESULTS

The cumulative 36-month incidence of HPV infection was 43 percent (95 percent confidence interval, 36 to 49 percent). An increased risk of HPV infection was significantly associated with younger age, Hispanic ethnicity, black race, an increased number of vaginal-sex partners, high frequencies of vaginal sex and alcohol consumption, anal sex, and certain characteristics of partners (regular partners having an increased number of lifetime partners and not being in school). The median duration of new infections was 8 months (95 percent confidence interval, 7 to 10 months). The persistence of HPV for > or =6 months was related to older age, types of HPV associated with cervical cancer, and infection with multiple types of HPV but not with smoking. The risk of an abnormal Pap smear increased with persistent HPV infection, particularly with high-risk types (relative risk, 37.2; 95 percent confidence interval, 14.6 to 94.8).

CONCLUSIONS

The incidence of HPV infection in sexually active young college women is high. The short duration of most HPV infections in these women suggests that the associated cervical dysplasia should be managed conservatively.

The future of HPV testing in clinical laboratories and applied virology research

BACKGROUND

Human papillomaviruses (HPV) are now considered etiologic agents of cancer of the uterine cervix. Adjunctive diagnostic procedures for the detection of HPV infection could increase the sensitivity of primary and secondary screening of cervical cancer. HPV testing could also improve the specificity of screening programs resulting in avoidance of overtreatment and saving of costs for confirmatory procedures.

OBJECTIVES

To review the rationale of HPV testing in genital diseases and the potential applications of HPV DNA detection methods for clinical and epidemiological purposes.

RESULTS

Progression of HPV infection is associated with the persistence of HPV infection, involvement of high-risk HPV types, high HPV viral load in specimens, integration of viral DNA and possibly the presence of cofactors. The design of HPV diagnostic tests will need to take into account these parameters of disease progression. HPV DNA detection techniques based on signal-amplification are standardized, commercially available and detect several high-risk HPV types. They increase the sensitivity of screening for high-grade and low-grade lesions. Although they may yield false-negative results in the presence of significant HPV-related disease, new test formats could resolve this weakness. Amplification techniques are ideal instruments for epidemiologic purposes since they minimize misclassification of HPV infection status and allow for the detection of low viral burden infections. They are currently not readily applicable to diagnostic laboratories.

CONCLUSIONS

Before recommending HPV testing, prospective trials of untreated LSIL with HPV testing as well as the determination of the efficacy and cost-effectiveness of novel HPV tests, need to be completed.