Epidemiologic Factors Associated with Seropositivity to Human Papillomavirus Type 16 and 18 Virus–Like Particles and Risk of Subsequent Infection in Men

Association of naturally acquired type-specific HPV antibodies and subsequent HPV re-detection: systematic review and meta-analysis

BACKGROUND

Understanding the role of naturally acquired (i.e., infection-induced) human papillomavirus (HPV) antibodies against reinfection is important given the high incidence of this sexually transmitted infection. However, the protective effect of naturally acquired antibodies in terms of the level of protection, duration, and differential effect by sex remains incompletely understood. We conducted a systematic review and a meta-analysis to (1) strengthen the evidence on the association between HPV antibodies acquired through past infection and subsequent type-specific HPV detection, (2) investigate the potential influence of type-specific HPV antibody levels, and (3) assess differential effects by HIV status.

METHODS

We searched Embase and Medline databases to identify studies which prospectively assessed the risk of type-specific HPV detection by baseline homologous HPV serostatus among unvaccinated individuals. Random-effect models were used to pool the measures of association of naturally acquired HPV antibodies against subsequent incident detection and persistent HPV positivity. Sources of heterogeneity for each type were assessed through subgroup analyses stratified by sex, anatomical site of infection, male sexual orientation, age group, and length of follow-up period. Evidence of a dose-response relationship of the association between levels of baseline HPV antibodies and type-specific HPV detection was assessed. Finally, we pooled estimates from publications reporting associations between HPV serostatus and type-specific HPV detection by baseline HIV status.

RESULTS

We identified 26 publications (16 independent studies, with 62,363 participants) reporting associations between baseline HPV serostatus and incident HPV detection, mainly for HPV-16 and HPV-18, the most detected HPV type. We found evidence of protective effects of baseline HPV seropositivity and subsequent detection of HPV DNA (0.70, 95% CI 0.61-0.80, NE = 11) and persistent HPV positivity (0.65, 95% CI 0.42-1.01, NE = 5) mainly for HPV-16 among females, but not among males, nor for HPV-18. Estimates from 8 studies suggested a negative dose-response relationship between HPV antibody level and subsequent detection among females. Finally, we did not observe any differential effect by baseline HIV status due to the limited number of studies available.

CONCLUSION

We did not find evidence that naturally acquired HPV antibodies protect against subsequent HPV positivity in males and provide only modest protection among females for HPV-16. One potential limitation to the interpretation of these findings is potential misclassification biases due to different causes.

Reinfection of Nine-Valent Human Papillomavirus Vaccine Types Among HIV-Negative Men Who Have Sex With Men: A Prospective Cohort Study

Objectives

Reinfection of human papillomavirus (HPV) among men who have sex with men (MSM) after clearing the infection of HPV has not been well characterized. To understand the reinfection of HPV among human immunodeficiency virus (HIV) negative MSM without HPV vaccine, we analyzed the reinfection of nine-valent HPV vaccine (9v-HPV) types.

Methods

Data were acquired from a prospective cohort study among HIV-negative MSM in Urumqi of Xinjiang from 1 April 2016 to 14 July 2020. Participants were recruited through a local non-government organization using a website advertisement. Self-administered questionnaires and self-collected anal swabs were collected at baseline and every 6 months. The incidence rates of reinfection was calculated based on the number of events divided by person-months of observation of event risk. 95% confidence intervals (CIs) were calculated based on the Poisson distribution.

Results

A total of 515 HIV-negative unvaccinated MSM were included with a mean age of 30.93 years (SD 7.85), and 27.68% were reinfected with any 9v-HPV type after clearance. The reinfection incidence rate of any 9v-HPV was 14.47 per 1000 person-months (95% CI: 11.52–17.87). HPV52 was the most common type of reinfection, with a reinfection rate of 17.96 per 1,000 person months (95% CI: 11.58–26.33). Univariate analysis showed that MSM over the age of 30 had a slightly higher risk of reinfection with any 9v-HPV (Hazard ratio (HR): 1.57; 95% CI: 1.01–2.45), but no significant association was observed in multivariate analysis.

Conclusions

Our study showed MSM without HPV vaccine will become reinfected following the natural clearance of specific HPV types. It is also suggested that HPV vaccination is recommended not only prior to sexual debut but also after viral clearance for MSM to reduce HPV prevalence.

Human Papillomavirus Seroprevalence and Seroconversion Among Men Living With HIV: Cohort Study in South Africa

BACKGROUND

Men living with HIV (MLHIV) have a high burden of human papillomavirus (HPV)-related cancer. Understanding serological dynamics of HPV in men can guide decisions on introducing HPV vaccination and monitoring impact. We determined HPV seroprevalence and evaluated factors associated with HPV seroconversion among MLHIV in Johannesburg, South Africa.

METHODS

We enrolled 304 sexually active MLHIV 18 years and older and collected sociobehavioral data, blood samples (CD4 counts, HIV-1 plasma viral load, and HPV serology), and genital and anal swabs [HPV DNA and HPV viral load (VL)] at enrollment and 6-monthly for up to 18 months. Antibodies to 15 HPV types were measured using HPV pseudovirions. Generalized estimating equations were used to evaluate correlates of HPV seroconversion.

RESULTS

Median age at enrollment was 38 years (IQR: 22-59), 25% reported >1 sexual partner in the past 3 months, and 5% reported ever having sex with other men. Most participants (65%) were on antiretroviral therapy (ART), with median CD4 count of 445 cells/µL (IQR: 328-567). Seroprevalence for any HPV type was 66% (199/303). Baseline seropositivity for any bivalent (16/18), quadrivalent (6/11/16/18), and nonavalent (6/11/16/18/31/33/45/52/58) vaccine types was 19%, 37%, and 60%, respectively. At 18 months, type-specific seroconversion among 59 men whose genital samples were HPV DNA positive but seronegative for the same type at enrollment was 22% (13/59). Type-specific seroconversion was higher among men with detectable HIV plasma viral load (adjusted odds ratio = 2.78, 95% CI: 1.12 to 6.77) and high HPV VL (adjusted odds ratio = 3.32, 95% CI: 1.42 to 7.74).

CONCLUSIONS

Seropositivity and exposure to nonavalent HPV types were high among MLHIV. HPV vaccination of boys before they become sexually active could reduce the burden of HPV infection among this at-risk population.

Seroprevalence of Human Papillomavirus 6/11/16/18 Among Self-identified Gay/Bisexual Men Who Have Sex With Men, Men Who Have Sex With Women, and Females, United States, 2003-2010

BACKGROUND

Differences in human papillomavirus (HPV) seroprevalence by sex have been observed, likely due to differences in the anatomic site of HPV exposure. Seroconversion may be more likely after exposure at nonkeratinized (mucosal) compared to keratinized epithelium. We compared seroprevalence among self-identified gay/bisexual men who have sex with men (MSM) and females, 2 groups more likely exposed at mucosal epithelium, and men who only have sex with women (MSW), a group likely exposed primarily at keratinized epithelium, using data from the National Health and Nutrition Examination Survey from 2003 to 2010.

METHODS

HPV 6/11/16/18 serum antibody was detected using a multiplexed, competitive luminex immunoassay. Weighted seroprevalence was estimated among unvaccinated, sexually experienced 18-59 year-old MSM, MSW, and females, overall and by demographic and sexual behavior characteristics. Seroprevalences were compared using prevalence ratios adjusted for sexual behavior (aPRs).

RESULTS

Overall, seroprevalence in MSM, MSW, and females was 42.6%, 13.2%, and 37.1%, respectively. Seroprevalence in MSM was comparable to females (aPR: 0.85, 95% confidence interval [CI]: 0.68-1.08) and higher than MSW (aPR: 2.72, 95% CI: 2.19-3.38). MSW had a significantly lower seroprevalence than females (aPR: 0.31, 95% CI: 0.28-0.34). Similar associations were seen in all sociodemographic subgroups. Seroprevalence increased with number of lifetime sex partners in all groups.

CONCLUSIONS

In this population-based survey, HPV seroprevalence among groups likely exposed at mucosal epithelium (MSM, females) was comparable; seroprevalence in both groups was higher than in MSW. Future research could explore whether differences in seropositivity following infection result in differential protection from future infection.

Estimating incidence rates of grouped HPV types: A systematic review and comparison of the impact of different epidemiological assumptions

BACKGROUND

Some studies on human papillomavirus (HPV) provide not only type-specific incidence rates (IR), but also IRs of HPV groupings (e.g. the nonavalent grouping). We made an inventory of the different approaches used to calculate such IRs and assessed their impact on the estimated IRs of HPV groupings.

METHODS

We performed a systematic review assessing all approaches used in literature to estimate IRs. Subsequently we applied these approaches to data of a Dutch cohort study on HPV in men who have sex with men (H2M). IRs were estimated for six different HPV groupings.

RESULTS

The systematic review yielded six different approaches (A-F) for estimating the IRs, varying in exclusion criteria at baseline, and the definitions of an incident event and person-time. Applying these approaches to the H2M dataset (n = 749), we found differences in the number of participants at risk, number of incidents events, person-time, and IR. For example, for the nonavalent grouping, depending on the approach chosen, the IR varied between 3.09 and 6.54 per 100 person-months.

CONCLUSION

In published studies different epidemiological assumptions are used to estimate IRs of grouped HPV types, leading to widely differing estimates of IRs. IRs between different studies may therefore not be comparable.

An Examination of HPV16 Natural Immunity in Men Who Have Sex with Men (MSM) in the HPV in Men (HIM) Study

Background: Evidence suggests that natural antibodies developed after HPV16 infection may protect some women but not men against subsequent HPV16 reacquisition. Less is known whether antibodies developed following HPV16 infection are protective among men who have sex with men (MSM).Methods: Four hundred seventy-five MSM from the Human Papillomavirus Infection in Men (HIM) study were tested for serum antibodies to HPV16 L1 using enzyme-linked immunosorbent assays, and for anal and genital HPV16 DNA using PCR consensus primer system (PGMY 09/11). Adjusted Cox regression was used to evaluate whether baseline HPV16 seropositivity impacts subsequent genital or anal HPV16 DNA.Results: The risk of subsequent genital HPV16 [aHR = 1.05, 95% confidence interval (CI) = 0.66-1.68] and anal HPV16 infections among MSM (aHR = 2.34, 95% CI = 0.92-5.98) was similar or nonsignificantly higher in HPV16-seropositive than HPV16-seronegative MSM. The risk of genital HPV16 was also similar between HPV16-seronegative and HPV16-seropositive MSM in the highest tertile of HPV16 antibody levels and when restricting to those with new sex partners during follow-up (P > 0.20). Among the 118 MSM who were HPV16 seropositive, 90% remained HPV16 seropositive up to 4 years later. When tested together, MSM with the highest antibody titers (top tertile) had similar levels to females (mean = 130.3 vs. 134.5 EU/mL, P = 0.84).Conclusions: Despite years of HPV16 seropositivity persistence and antibody titers comparable with females, this study suggested no evidence of HPV16 natural antibodies protecting against subsequent genital or anal HPV16 infection in MSM.Impact: This could help partially explain the high incidence of genital and anal HPV16 infection and related anal cancer seen in middle-aged and older MSM. Cancer Epidemiol Biomarkers Prev; 27(4); 496-502. ©2018 AACR.

Bias Due to Correlation Between Times-at-Risk for Infection in Epidemiologic Studies Measuring Biological Interactions Between Sexually Transmitted Infections: A Case Study Using Human Papillomavirus Type Interactions

The clustering of human papillomavirus (HPV) infections in some individuals is often interpreted as the result of common risk factors rather than biological interactions between different types of HPV. The intraindividual correlation between times-at-risk for all HPV infections is not generally considered in the analysis of epidemiologic studies. We used a deterministic transmission model to simulate cross-sectional and prospective epidemiologic studies measuring associations between 2 HPV types. When we assumed no interactions, the model predicted that studies would estimate odds ratios and incidence rate ratios greater than 1 between HPV types even after complete adjustment for sexual behavior. We demonstrated that this residual association is due to correlation between the times-at-risk for different HPV types, where individuals become concurrently at risk for all of their partners' HPV types when they enter a partnership and are not at risk when they are single. This correlation can be controlled in prospective studies by restricting analyses to susceptible individuals with an infected sexual partner. The bias in the measured associations was largest in low-sexual-activity populations, cross-sectional studies, and studies which evaluated infection with a first HPV type as the exposure. These results suggest that current epidemiologic evidence does not preclude the existence of competitive biological interactions between HPV types.

Seroprevalence and Associated Factors of 9-Valent Human Papillomavirus (HPV) Types among Men in the Multinational HIM Study

Background

Human papillomavirus (HPV) is one of the most common sexually transmitted infections worldwide. Recently a 9-valent HPV (9vHPV) prophylactic vaccine was licensed. Seroprevalence prior to vaccine dissemination is needed for monitoring vaccine effectiveness over time. Few studies have assessed the seroprevalence of 9vHPV types in men.

Objectives

To investigate the seroprevalence of 9vHPV vaccine types and associated risk factors among men residing in Brazil, Mexico, and the United States.

Methods

Six hundred men were randomly selected from the HPV Infection in Men (HIM) Study. Archived serum specimens collected at enrollment were tested for antibodies against nine HPV types (6, 11, 16, 18, 31, 33, 45, 52 and 58) using a glutathione S-transferase (GST) L1-based multiplex serologic assay. Socio-demographic, lifestyle and sexual behavior data at enrollment were collected through a questionnaire. Binomial proportions were used to estimate seroprevalence and logistic regression was used to examine factors associated with seropositivity of type-specific and grouped (i.e. 9vHPV, high-risk 9vHPV, low risk 9vHPV, and five-additional) HPV types.

Results

Overall, 28.3% of men were seropositive for at least one of the 9vHPV vaccine types, 14.0% for at least one of the seven high-risk types (16, 18, 31, 33, 45, 52 and 58) and 11.2% for at least one of the five high-risk types (31, 33, 45, 52 and 58) not included in the quadrivalent HPV vaccine, and 17.4% for at least one of the low-risk types (6/11). In multivariate analyses, odds ratios adjusted (AOR) for country of residence, age, marital status, smoking, number of anal sex lifetime partners, compared to men with no anal sex lifetime partners, men with ≥2 partners were more likely to be seropositive for grouped HPV [(9vHPV: AOR 2.52; 95% confidence interval (CI) 1.40–4.54), (high-risk 9vHPV: AOR 2.18; 95%CI: 1.05–4.50) and (low-risk 9vHPV: AOR 2.12; 95%CI: 1.12–4.03)], and individual HPV types 6, 16, 33 and 58 with AORs ranging from 2.19 to 7.36. Compared to men aged 18–30 years, men older than 30 years were significantly more likely to be seropositive for any high-risk 9vHPV, in addition to individual types 18 and 45; and compared to never smokers, current smokers were more likely to be seropositive to 9vHPV, low-risk 9vHPV and HPV 6. In contrast, married men were less likely to be seropositive to any high-risk 9vHPV and individual HPV types 18 and 31 when compared to single men.

Conclusions

These data indicate that exposure to the nine HPV types included in the 9vHPV vaccine is common in men and that seropositivity to 9vHPV vaccine types is associated with older age and the lifetime number of anal sex partners. Nine valent HPV vaccination of males and females has the potential to prevent HPV related diseases and transmission in both sexes.

Gender and age-specific seroprevalence of human papillomavirus 16 and 18 in general population in Tehran, Iran

The assessment of the gender and age-specific seroprevalence of human papillomavirus (HPV) is essential for planning of HPV vaccine implementation into the preventive programs. In this study, we aimed to determine the age-specific seroprevalence of HPV-16 and 18 in both males and females in Tehran, Iran. Three hundred and seventy-eight women (10-35 years) and 162 men (10-25 years) from Tehran, Iran, were enrolled. Anti-HPV IgG antibodies against HPV-16 and HPV-18 were detected by ELISA using papillomavirus type 16 and 18 L1-capsids as antigen. HPV-16 antibody was detected in 15.6 and 13.6% of women and men, respectively. Antibody against HPV-18 was found positive in 12.7 and 8% of women and men, respectively. The highest seroprevalence of HPV-16 and 18 were seen in women aged 26-30 years (22.2 and 19.4%, respectively), and the lowest HPV-16 and 18 seropositivity rates were seen in males and females aged 10-15 years (9.3 and 1.9%, respectively). In our cohort of study, in males, both anti-HPV-16 and 18 increased after age 15 years, peaking in men aged 21-25 years. In women, both HPV-16 and 18 seropositivity increased after 15 years, declined at 21-25 years, peaked in women aged 26-30 years and again decreased after 30 years. Our data showed increasing exposure rate to high-risk HPV vaccine types in our studied population over 15 years of age. In order to prevent the HPV-related cancers, implementation of HPV vaccine into the national immunization program in Iran and vaccination of females and males less than 15 years of age are suggested.

Impact of Serum Antibodies to HPV Serotypes 6, 11, 16, and 18 to Risks of Subsequent Genital HPV Infections in Men: The HIM Study

Naturally induced serum antibodies against human papillomavirus (HPV) may affect risks of subsequent incident genital infections by HPV 6, 11, 16, or 18 in men. In this study, we examined the hypothesis by following 4,123 healthy men every 6 months (median follow-up time, 4.1 years). HPV antibodies were measured at baseline using a virus-like particle-based ELISA assay. Genital HPV genotypes were detected using Roche Linear Array. Incidence proportions and 6-month persistence proportions were calculated at 6-month intervals. Kaplan-Meier curves and Cox models were used to assess genotype-specific cumulative incidence and HRs, respectively. HPV 6, 11, 16, and 18 seroprevalence was 8.1%, 13.9%, 12.7%, and 10.8%, respectively. Significantly higher rates of incident infections were observed for HPV 16 among baseline-seropositive men [adjusted HR, 1.37; 95% confidence interval (CI), 1.01-1.86], with similar but nonsignificant HRs for 6-month persistent infections. Risk of persistent HPV 18 infection was significantly lower among seropositive men in the unadjusted model (HR, 0.22; 95% CI, 0.06-0.91), but not in the adjusted model (HR, 0.19; 95% CI, 0.03-1.37). Incident and 6-month persistent infections for HPV 6 and 11 did not differ by baseline serostatus. Baseline serostatus among men was not associated with a reduction in subsequent incident genital HPV 6, 11, and 16 infections. However, protection against persistent HPV18 infections was observed in unadjusted models. Our research suggests a need of further studies to examine the potentially protective effects of naturally induced HPV18 antibodies in men. Cancer Res; 76(20); 6066-75. ©2016 AACR.

Natural Acquired Immunity Against Subsequent Genital Human Papillomavirus Infection: A Systematic Review and Meta-analysis

BACKGROUND

Studies have been mixed on whether naturally acquired human papillomavirus (HPV) antibodies may protect against subsequent HPV infection. We performed a systematic review and meta-analysis to assess whether naturally acquired HPV antibodies protect against subsequent genital HPV infection (ie, natural immunity).

METHODS

We searched the MEDLINE and EMBASE databases for studies examining natural HPV immunity against subsequent genital type-specific HPV infection in female and male subjects. We used random-effects models to derive pooled relative risk (RR) estimates for each HPV type.

RESULTS

We identified 14 eligible studies that included >24,000 individuals from 18 countries that examined HPV natural immunity. We observed significant protection against subsequent infection in female subjects with HPV-16 (pooled RR, 0.65; 95% confidence interval, .50-.80) and HPV-18 (0.70; .43-.98) but not in male subjects (HPV-16: 1.22; .67-1.77 [P= .05 (test for heterogeneity)]; HPV-18: 1.50; .46-2.55; [P= .15]). We also observed type-specific protection against subsequent infection for a combined measure of HPV-6/11/31/33/35/45/52/58 in female subjects (pooled RR, 0.75; 95% confidence interval, .57-.92). Natural immunity was also evident in female subjects when analyses were restricted to studies that used neutralizing assays, used HPV persistence as an outcome, or reported adjusted analyses (each P< .05).

CONCLUSIONS

HPV antibodies acquired through natural infection provide modest protection against subsequent cervical HPV infection in female subjects.

Human papillomavirus serology and tobacco smoking in a community control group

Background

HPV infection is an established risk factor for oropharyngeal cancer, and it has been proposed that cigarette smoking may potentiate HPV infection in the oral epithelium. We sought to test the hypothesis that cigarette smoking increases HPV infection in an HPV16 serology study of cancer-free individuals.

Methods

Subjects were participants in a risk factor study for head and neck cancer, and were required to have no prior history of either HNSCC or any other cancer. Tobacco use and other risk factor data were gathered through interviewer-assisted questionnaires, while serology was conducted in a blinded fashion using a glutathione S-transferase capture enzyme-linked immunosorbent assay (ELISA) to detect antibodies against HPV16 L1, E1, E2, E4, E6 and E7 proteins. The differences in tobacco use by HPV serology were evaluated by ANOVA; and the reported odds ratios and 95% confidence intervals were determined by using unconditional logistic regression.

Results

We found no overall association of HPV16 serological markers with smoking. However, when the data were stratified by median age, smoking was positively associated with seropositivity for the HPV16 L1 capsid antigen in the younger controls while the older controls were less likely to be HPV16 L1 positive if they smoked (p_interaction < 0.002). There was no similar association of smoking and age with serological response to the early proteins (i.e E6, E7).

Conclusions

Exposure to HPV16 capsid protein (L1) is increased among relatively younger adults who smoke and diminished among older smokers. However, this pattern is not accompanied by a differential susceptibility for active infection (as determined by the early gene proteins such as E6 and E7) among young and older smokers.

Seroepidemiology of high-risk HPV in HIV-negative and HIV-infected MSM: the H2M study

BACKGROUND

Men who have sex with men (MSM), in particular HIV-infected MSM, are at increased risk for diseases related to human papilloma virus (HPV). Our goal was to assess the effect of HIV status on the presence of type-specific antibodies against seven high-risk HPV types in HPV-unvaccinated MSM. Moreover, we compared determinants of HPV seropositivity between HIV-negative and HIV-infected MSM.

METHODS

MSM ≥18 years of age were recruited from the Amsterdam Cohort Studies, a sexually transmitted infection clinic, and an HIV-treatment center in Amsterdam, the Netherlands. Participants completed a risk-factor questionnaire; serum samples were analyzed using a fluorescent bead-based multiplex assay.

RESULTS

MSM (n = 795) were recruited in 2010 to 2011; 758 MSM were included in this analysis. Median age was 40.1 years (interquartile range 34.8-47.5) and 308 MSM (40.6%) were HIV-infected. Seroprevalence of HPV-16 was 37.1% in HIV-negative and 62.7% in HIV-infected MSM (P < 0.001); seroprevalence of HPV-18 was 29.1% in HIV-negative MSM and 42.5% in HIV-infected MSM (P < 0.001). Similar patterns of seroprevalence were observed for HPV types 31, 33, 45, 52, and 58. In multivariable analyses, HPV seropositivity was associated with HIV infection [adjusted OR = 2.1; 95% confidence interval, 1.6-2.6]. In multivariable analyses stratified by HIV status, increasing age and number of lifetime male sex partners were significantly associated with HPV seropositivity in HIV-negative, but not HIV-infected MSM.

CONCLUSIONS

Seroprevalence of high-risk HPV types is high among unvaccinated MSM.

IMPACT

HIV infection is a strong and independent determinant for HPV seropositivity, which we hypothesize is because of increased persistence of HPV infection in HIV-infected MSM.

No evidence for a protective effect of naturally induced HPV antibodies on subsequent anogenital HPV infection in HIV-negative and HIV-infected MSM

OBJECTIVES

To assess whether HPV serum antibodies detected after natural infection protect against subsequent anal or penile infection with the same HPV type in HIV-negative and HIV-infected men who have sex with men (MSM).

METHODS

MSM aged ≥18 years were recruited in Amsterdam, the Netherlands (2010-2011), and followed-up semi-annually. Antibodies against 7 high-risk HPV types in baseline serum samples were tested using a multiplex immunoassay; baseline, 6-, and 12-month anal and penile samples were tested for HPV DNA and genotyped using the SPF10-PCR DEIA/LiPA25 system (version 1). Statistical analyses were performed using the Wei-Lin-Weissfeld method.

RESULTS

719 MSM (median age 40 years; IQR 35-48) with baseline and follow-up data were included in these analyses; 287 (40%) were HIV-infected. HPV seropositivity at baseline was not significantly associated with subsequent type-specific HPV infection at 6 or 12 months in multivariable analyses (for anal infection adjusted hazard ratio (aHR) 1.2; 95% CI 0.9-1.6; for penile infection aHR 0.8; 95% CI 0.6-1.2). High antibody concentrations showed no protective effect against subsequent infection either.

CONCLUSIONS

In a population of highly sexually active, adult MSM, naturally induced HPV antibodies may not protect MSM against subsequent anal or penile HPV infection within one year.

Prevalence, incidence, and risk factors for human papillomavirus 16 seropositivity in Australian homosexual men

BACKGROUND

Human papillomavirus 16 (HPV16) has been causally associated with approximately 70% of anal cancers. This cancer is markedly increasing among homosexual men. There is limited knowledge of the epidemiology and natural history of anal HPV infection in homosexual men.

METHODS

Behavioral data and sera for antibodies to HPV16 L1 were collected annually for 1427 HIV-negative and 245 HIV-positive Australian homosexual men. Seroprevalence, seroincidence, and risk factors were calculated.

RESULTS

Among HIV-negative men, 25.4% were HPV16 seropositive at baseline compared with 44.3% of HIV-positive men. HPV16 seroincidence was 3.1/100 person-years among HIV-negative men and 1.3/100 person-years among HIV-positive men. Seroincidence among HIV-negative men remained >3% per year until 45 years of age, before declining. In multivariate analyses of data from HIV-negative men, seroprevalent HPV16 was associated with sexual risk behaviors and seropositivity for several viral sexually transmissible infections. Seroincident HPV16 was associated with younger age and unprotected anal intercourse with HIV-positive partners. Among men who predominantly practiced insertive anal intercourse, circumcision was associated with a 57% reduction in seroincident HPV16 (hazard ratio = 0.43, 95% confidence interval: 0.21-0.88, P = 0.021).

CONCLUSIONS

HPV16 seroincidence remained common in men until their mid 40s suggesting that vaccination may be protective in sexually active young gay men. Both HPV16 seroprevalence and seroincidence correlated well with markers of higher risk sexual activity, particularly receptive anal sexual practices. An association between circumcision and decreased HPV16 seroconversion in HIV-negative men who preferred the insertive position in anal sex was observed.

Aggregation and competitive exclusion: explaining the coexistence of human Papillomavirus types and the effectiveness of limited vaccine conferred cross-immunity

Human Papillomavirus (HPV) types are sexually transmitted infections that cause a number of human cancers. According to the competitive exclusion principle in ecology, HPV types that have lower transmission probabilities and shorter durations of infection should be outcompeted by more virulent types. This, however, is not the case, as numerous HPV types co-exist, some which are less transmissible and more easily cleared than others. This paper examines whether this exception to the competitive exclusion principle can be explained by the aggregation of infection with HPV types, which results in patchy spatial distributions of infection, and what implications this has for the effect of vaccination on multiple HPV types. A deterministic transmission model is presented that models the patchy distribution of infected individuals using Lloyd's mean crowding. It is first shown that higher aggregation can result in a reduced capacity for onward transmission and reduce the required efficacy of vaccination. It is shown that greater patchiness in the distribution of lower prevalence HPV types permits co-existence. This affirms the hypothesis that the aggregation of HPV types provides an explanation for the violation of the competitive exclusion principle. Greater aggregation of lower prevalence types has important implications where type-specific HPV vaccines also offer cross-protection against non-target types. It is demonstrated that the degree of cross-protection can be less than the degree of vaccine protection conferred against directly targeted types and still result in the elimination of non-target types when these non-target types are patchily distributed.

Human papillomavirus (HPV) L1 and L1-L2 virus-like particle-based multiplex assays for measurement of HPV virion antibodies

Humoral immunity to human papillomavirus (HPV) has not been fully characterized, and there is currently no standard serologic test for the measurement of HPV antibodies. Most HPV serologic assays developed to date are based on virus-like particles (VLPs) of the major HPV capsid protein, L1. We sought to compare the performance of a multiplex HPV L1 VLP-based serologic assay to that of an assay based on VLPs comprised of both L1 and the minor capsid, L2. We developed HPV L1 VLP and L1-L2 VLP-based multiplex seroassays for the detection of HPV type 16 (HPV16) and HPV18 virion binding antibodies using Luminex fluorescent bead technology. We compared the performance of these assays to that of established pseudovirion-based neutralization and L1 VLP-based enzyme-linked immunosorbent assays (ELISAs). A total of 391 serum specimens from unvaccinated adult males and females were tested. The L1 and L1-L2 VLP multiplex seroassays each demonstrated substantial agreement with both the neutralization assays and the ELISAs for the detection of HPV16 antibodies (κ = 0.60 to 0.64). However, the L1-L2 VLP seroassay demonstrated better agreement with neutralization assays for the detection of HPV18 antibodies than the L1 VLP seroassay (κ = 0.74 and 0.43, respectively). L1 and L1-L2 VLP seroassays showed excellent agreement with one another for the detection of HPV16 antibodies (κ = 0.86) but only moderate agreement for HPV18 antibodies (κ = 0.44). The HPV L1-L2 VLP seroassay performs well for the concurrent measurement of HPV16 and -18 antibodies in large numbers of samples and may be extended to include other HPV types.

Age-specific human papillomavirus antibody and deoxyribonucleic acid prevalence: a global review

PURPOSE

Global data on human papillomavirus (HPV) serological and deoxyribonucleic acid (DNA) prevalence are essential to optimize HPV prophylactic vaccination strategies.

METHODS

We conducted a global review of age-specific HPV antibody and studies with both antibody and DNA prevalence for HPV-16, -18, -6, and -11.

RESULTS

One hundred seventeen studies were included; participants' ages ranged from several hours to >90 years. HPV-16 seroprevalence was generally higher in Africa, Central and South America, and North America, more prevalent among women than among men, and peaked around ages 25-40 years. HPV-18 seroprevalence was generally lower than HPV-16 with a later age peak. Data were limited for HPV-6 and -11, both of which peaked at ages similar to HPV-18. Among 9-26-year-old females, HPV-16 seroprevalence ranged from 0%-31% in North America, 21%-30% in Africa, 0%-23% in Asia/Australia, 0%-33% in Europe, and 13%-43% in Central and South America. HPV-16/-18 DNA prevalence peaked 10-15 years before corresponding HPV-16/-18 antibody prevalence.

CONCLUSIONS

Females within the HPV vaccine-eligible age-group (9-26 years) had a range of dual HPV-16 DNA and serology negativity from 81%-87%, whereas 90%-98% were HPV-16 DNA negative. Serology and DNA data are lacking worldwide for females younger than age 15 years, the prime target group for vaccination.

Prevalent serum antibody is not a marker of immune protection against acquisition of oncogenic HPV16 in men

In women, naturally induced anti-human papilloma virus (HPV) serum antibodies are a likely marker of host immune protection against subsequent HPV acquisition and progression to precancerous lesions and cancers. However, it is unclear whether the same is the case in men. In this study, we assessed the risk of incident genital infection and 6-month persistent genital infection with HPV16 in relation to baseline serostatus in a cohort of 2,187 men over a 48-month period. Genital swabs were collected every 6 months and tested for HPV presence. Incidence proportions by serostatus were calculated at each study visit to examine whether potential immune protection attenuated over time. Overall, incidence proportions did not differ statistically between baseline seropositive and seronegative men at any study visit or over the follow-up period. The risk of incident and 6-month persistent infection was not associated with baseline serostatus or baseline serum antibody levels in the cohort. Our findings suggest that baseline HPV seropositivity in men is not associated with reduced risk of subsequent HPV16 acquisition. Thus, prevalent serum antibodies induced by prior infection may not be a suitable marker for subsequent immune protection against genital HPV16 acquisition in men.

Serum antibody response following genital {alpha}9 human papillomavirus infection in young men

Background. Although the prevalence of human papillomavirus (HPV) genital infection is similarly high in males and females, seroprevalence is lower in males. This study assessed rates and determinants of seroconversion after detection of genital HPV infection in young men. Methods. We investigated HPV type-specific seroconversion in a cohort of heterosexual male university students who had an α9 HPV type (HPV-16, -31, -33, -35, -52, -58, or -67) detected in the genital tract (n = 156). HPV DNA and antibodies were detected and typed using liquid bead-based multiplex assays. We calculated seroconversion using Kaplan-Meier survival analysis. Cox proportional hazards models with generalized estimating equations were used to examine associations with seroconversion. Results. Within 24 months of detecting genital HPV infection, type-specific seroconversion ranged from 4% for HPV-52 to 36% for HPV-31. HPV-16 seroconversion at 24 months was 13% (95% confidence interval [CI], 7%-25%). Among incident HPV infections, ever cigarette smoking and infection site(s) (shaft/scrotum and glans/urine vs shaft/scrotum or glans/urine only) were positively associated with type-specific seroconversion. Conclusions. For each of the α9 HPV types, type-specific seroconversion within 24 months was observed in 36% or less of infected men. Seroconversion might be related to cigarette smoking and genital site(s) infected.

HPV vaccine and adolescent males

In 2009, the United States approved quadrivalent HPV vaccine for males 9-26 years old, but data on vaccine uptake are lacking. We determined HPV vaccine uptake among adolescent males, as well as stage of adoption and vaccine acceptability to parents and their sons. A national sample of parents of adolescent males ages 11-17 years (n=547) and their sons (n=421) completed online surveys during August and September 2010. Analyses used multivariate linear regression. Few sons (2%) had received any doses of HPV vaccine, and most parents and sons were unaware the vaccine can be given to males. Parents with unvaccinated sons were moderately willing to get their sons free HPV vaccine (mean=3.37, SD=1.21, possible range 1-5). Parents were more willing to get their sons vaccinated if they perceived higher levels of HPV vaccine effectiveness (β=0.20) or if they anticipated higher regret about their sons not getting vaccinated and later developing an HPV infection (β=0.32). Vaccine acceptability was also modest among unvaccinated sons (mean=2.98, SD=1.13, possible range 1-5). Sons were more willing to get vaccinated if they perceived higher peer acceptance of HPV vaccine (β=0.39) or anticipated higher regret about not getting vaccinated and later developing an HPV infection (β=0.22). HPV vaccine uptake was nearly nonexistent a year after permissive national recommendations were first issued for males. Vaccine acceptability was moderate among both parents and sons. Efforts to increase vaccine uptake among adolescent males should consider the important role of peer acceptance and anticipated regret.

Human papillomavirus (HPV) 6, 11, 16, and 18 seroprevalence is associated with sexual practice and age: results from the multinational HPV Infection in Men Study (HIM Study)

BACKGROUND

Few human papillomavirus (HPV) serology studies have evaluated type-specific seroprevalence of vaccine HPV types in men. This study investigates seroprevalence of HPV 6, 11, 16, and 18, and associated risk factors in men residing in three countries (United States, Mexico, and Brazil).

METHODS

Data from 1,477 men aged 18 to 70 enrolled in the HPV Infection in Men Study (HIM Study) were analyzed. Serum antibody testing was performed with virus-like particle-based ELISA. Potential risk factors were assessed for individual HPV types by the use of logistic regression.

RESULTS

Overall, HPV-6, 11, 16, and 18 seroprevalence was 14.8%, 17.3%, 11.2%, and 5.8%, respectively. Thirty-four percent of men were seropositive to one or more HPV types. When examined by sexual practice, 31.2% of men who had sex with women, 65.6% of men who had sex with men (MSM), and 59.4% of men who had sex with both men and women (MSMW) were seropositive to one or more HPV types. Seroprevalence increased with age among young-to-middle-aged men with significant upward age trends observed for HPV 11, 16, and 18. Men with multiple lifetime male anal sex partners were 2 to 4 times more likely to be HPV 6 or 11 seropositive and 3 to 11 times more likely to be HPV 16 or 18 seropositive.

CONCLUSION

Our data indicate that exposures to vaccine HPV types were common in men and highly prevalent among MSM and MSMW.

IMPACT

Our study provides strong evidence that the practice of same-sex anal intercourse is an independent risk factor for seroprevalence of individual vaccine HPV types. Examination of antibody responses to HPV infections at various anatomic sites in future studies is needed to elaborate on the mechanism.

Age-specific prevalence of and risk factors for anal human papillomavirus (HPV) among men who have sex with women and men who have sex with men: the HPV in men (HIM) study

BACKGROUND

An increasing incidence of anal cancer among men suggests a need to better understand anal canal human papillomavirus (HPV) infection among human immunodeficiency virus-negative men.

METHODS

Genotyping for HPV was conducted on cells from the anal canal among men who have sex with women (MSW) and men who have sex with men (MSM), aged 18-70 years, from Brazil, Mexico, and the United States. Factors associated with anal HPV infection were assessed using multivariable logistic regression.

RESULTS

The prevalence of any HPV type and oncogenic HPV types did not differ by city. Anal canal HPV prevalence was 12.2% among 1305 MSW and 47.2% among 176 MSM. Among MSW, reporting a lifetime number of ≥ 10 female sex partners, a primary sexual relationship <1 year in duration, and a prior hepatitis B diagnosis were independently associated with detection of any anal HPV in multivariable analysis. Among MSM, a younger age, reporting ≥ 2 male anal sex partners in the past 3 months, and never using a condom for anal sex in the past 6 months were independently associated with detection of any anal HPV in multivariable analysis.

CONCLUSIONS

Number of sex partners was associated with anal HPV infection in both MSW and MSM. Anal HPV infection in men may be mediated by age, duration of sexual relationship, and condom use.