Population- and type-specific clustering of multiple HPV types across diverse risk populations in the Netherlands

Pattern of multiple human papillomavirus infection and type competition: An analysis in healthy Chinese women aged 18-45 years

To assess the pattern of multiple human papillomavirus infection to predict the type replacement postvaccination. A total of 7372 women aged 18-45y from a phase III trial of an Escherichia coli-produced HPV-16/18 vaccine were analyzed at enrollment visit before vaccination. Hierarchical multilevel logistic regression was used to evaluate HPV vaccine type and nonvaccine-type interactions with age as a covariate. Binary logistic regression was construed to compare multiple infections with single infections to explore the impact of multiple-type infections on the risk of cervical disease. Multiple HPV infections were observed in 25.2% of HPV-positive women and multiple infections were higher than expected by chance. Statistically significant negative associations were observed between HPV16 and 52, HPV18 and HPV51/52/58, HPV31 and HPV39/51/52/53/54/58, HPV33 and HPV52/58, HPV58 and HPV52, HPV6 and HPV 39/51/52/53/54/56/58. Multiple HPV infections increased the risk of CIN2+ and HSIL+, with the ORs of 2.27(95%CI: 1.41, 3.64) and 2.26 (95%CI: 1.29, 3.95) for multiple oncogenic HPV infection separately. However, no significant evidence for the type-type interactions on risk of CIN2+ or HSIL+. There is possibility of type replacement between several pairs of vaccine and nonvaccine HPV type. Multiple HPV infection increased the risk of cervical disease, but coinfection HPV types seem to follow independent disease processes. Continued post-vaccination surveillance for HPV 51/52/58 types and HPV 39/51 types separately was essential after the first and second generation of HPV vaccination implementation in China.

Associations of Single Versus Multiple Human Papillomavirus Infections With the Prevalence of Cervical Intraepithelial Neoplasia 2/3 and Squamous Cell Carcinoma Lesions: Human Papillomavirus Type-Specific Attribution

The risk of developing cervical squamous lesions in women with multiple high-risk human papillomavirus (hrHPV) infections is uncertain. The aim of this retrospective study was to investigate the type-specific attribution and phylogenetic effects of single and multiple hrHPV subtypes in cervical squamous lesions. All cases with cervical histopathologic diagnosis and human papillomavirus (HPV) genotyping results in the 6 months preceding biopsy from October 2018 to December 2022 were studied and analyzed. Over the study period, 70,361 cases with histopathologic follow-up and prior HPV genotyping were identified. The hrHPV-positive rate was 55.6% (39,104/70,361), including single hrHPV detected in 27,182 (38.6%), 2 types of hrHPV detected in 8158 (11.6%), and 3 types of hrHPV detected in 2486 (3.5%). Among 16,457 cases with a histologically diagnosed squamous lesion (cervical intraepithelial neoplasia 1: 11411; cervical intraepithelial neoplasia 2/3: 4192; squamous cell carcinoma: 854 cases), the prevalence of single hrHPV infection increased, but the rate of multiple concomitant hrHPV infections showed negative association as the degree of squamous lesions increased. Among women with a single HPV16 infection, cervical intraepithelial neoplasia 2/3 and squamous cell carcinoma (CIN2+) diagnostic rate was 30.6%, and it increased to 47.6% when coinfected with HPV33 (P < .001) but significantly decreased when coinfected with all other hrHPV types (P < .05). By comparing CIN2+ diagnostic rates in 40 most common 2 types of hrHPV infections with related single hrHPV infection, CIN2+ rates were decreased in 12 combinations (30.0%), equivalent in 26 combinations (65.0%), and increased in 2 combinations (5.0%). The cases with 3 types of HPV infections reduced the risk for CIN2+ compared with related single HPV infections. HPV16+52+53, HPV16+52+68, HPV16+52+51, HPV16+39+52, and HPV16+58+53 significantly decreased the risk of CIN2+ compared with HPV16 single infection (P < .05). This study demonstrates that multiple hrHPV infections are not associated with cumulatively higher risk for CIN2+ development, suggesting that oncogenic progression of multiple hrHPV-associated cervical squamous lesions is neither synergistic nor a cumulative effect at the phylogenetic level, possibly a way of competitive interference.

Reconstructing multi-strain pathogen interactions from cross-sectional survey data via statistical network inference

Infectious diseases often involve multiple pathogen species or multiple strains of the same pathogen. As such, knowledge of how different pathogens interact is key to understand and predict the outcome of interventions targeting only a subset of species or strains involved in disease. Population-level data may be useful to infer pathogen strain interactions, but most previously used inference methods only consider uniform interactions between all strains or focus on marginal pairwise interactions. As such, these methods are prone to bias induced by indirect interactions through other strains. Here, we evaluated statistical network inference for reconstructing heterogeneous interactions from cross-sectional surveys detecting joint presence/absence patterns of pathogen strains within hosts. We applied various network models to simulated survey data, representing endemic infection states of multiple pathogen strains with potential interactions in acquisition or clearance of infection. Satisfactory performance was demonstrated by the estimators converging to the true interactions. Accurate reconstruction of interaction networks was achieved by regularization or penalization for sample size. Although performance deteriorated in the presence of host heterogeneity, this was overcome by correcting for individual-level risk factors. Our work demonstrates how statistical network inference could prove useful for detecting multi-strain pathogen interactions and may have applications beyond epidemiology.

Evolution of human papilloma virus prevalence in a highly vaccinated region in Belgium: a retrospective cohort study in Flemish women (2010-2019)

OBJECTIVE

In order to lower the incidence of cervical cancer, vaccines against high-risk types of the human papilloma virus (hrHPV) were approved and brought on the market in 2007, with a partial reimbursement for Belgian citizens younger than 18 years old. Since 2010, a school-based vaccination program ensures a high vaccination coverage in young women. In this study, the impact of the Belgian vaccination program on the prevalence of HPV 16/18 is studied, together with the evolution of the prevalence of other hrHPV types and precancerous lesions.

METHODS

Results of HPV typing and cytology in papanicolaou-smears from women aged 20-23 years taken between 2010 and 2019 were used. An older, nonvaccinated group of women of 40-45 years old served as a control group.

RESULTS

A significant decrease in prevalence of HPV types 16 and 18 was found in the 20-23-years-old women, whereas no decrease was found in the age group 40-45. Alongside this decrease, a significant decrease in prevalence of subtypes 6, 11 and 31 was observed, whereas type 31 is not included in the administered vaccines. Remarkably, there was no decrease in prevalence of cytological abnormalities in the study group during this study. There was even an increase in prevalence of high-risk types 53, 58 and 67.

CONCLUSION

These findings emphasise the need to maintain the screening programs, even in areas with high vaccination coverage.

HPV Sequencing Facilitates Ultrasensitive Detection of HPV Circulating Tumor DNA

PURPOSE

Human papillomavirus (HPV) DNA offers a convenient circulating tumor DNA (ctDNA) marker for HPV-associated malignancies, but current methods, such as digital PCR (dPCR), provide insufficient accuracy for clinical applications in patients with low disease burden. We asked whether a next-generation sequencing approach, HPV sequencing (HPV-seq), could provide quantitative and qualitative assessment of HPV ctDNA in low disease burden settings.

EXPERIMENTAL DESIGN

We conducted preclinical technical validation studies on HPV-seq and applied it retrospectively to a prospective multicenter cohort of patients with locally advanced cervix cancer (NCT02388698) and a cohort of patients with oropharynx cancer. HPV-seq results were compared with dPCR. The primary outcome was progression-free survival (PFS) according to end-of-treatment HPV ctDNA detectability.

RESULTS

HPV-seq achieved reproducible detection of HPV DNA at levels less than 0.6 copies in cell line data. HPV-seq and dPCR results for patients were highly correlated (R ² = 0.95, P = 1.9 × 10^-29) with HPV-seq detecting ctDNA at levels down to 0.03 copies/mL plasma in dPCR-negative posttreatment samples. Detectable HPV ctDNA at end-of-treatment was associated with inferior PFS with 100% sensitivity and 67% specificity for recurrence. Accurate HPV genotyping was successful from 100% of pretreatment samples. HPV ctDNA fragment sizes were consistently shorter than non-cancer-derived cell-free DNA (cfDNA) fragments, and stereotyped cfDNA fragmentomic patterns were observed across HPV genomes.

CONCLUSIONS

HPV-seq is a quantitative method for ctDNA detection that outperforms dPCR and reveals qualitative information about ctDNA. Our findings in this proof-of-principle study could have implications for treatment monitoring of disease burden in HPV-related cancers. Future prospective studies are needed to confirm that patients with undetectable HPV ctDNA following chemoradiotherapy have exceptionally high cure rates.

Population Impact of Girls-Only Human Papillomavirus 16/18 Vaccination in The Netherlands: Cross-Protective and Second-Order Herd Effects

Background

Human papillomavirus (HPV) vaccination programs achieve substantial population-level impact, with effects extending beyond protection of vaccinated individuals. We assessed trends in HPV prevalence up to 8 years postvaccination among men and women in the Netherlands, where bivalent HPV vaccination, targeting HPV types 16/18, has been offered to (pre)adolescent girls since 2009 with moderate vaccination coverage.

Methods

We used data from the PASSYON study, a survey initiated in 2009 (prevaccination) and repeated biennially among 16- to 24-year-old visitors of sexual health centers. We studied genital HPV positivity from 2009 to 2017 among women, heterosexual men, and unvaccinated women using Poisson generalized estimating equation models, adjusted for individual- and population-level confounders. Trends were studied for 25 HPV types detected by the SPF10-LiPA25 platform.

Results

A total of 6354 women (64.7% self-reported unvaccinated) and 2414 heterosexual men were included. Percentual declines in vaccine types HPV-16/18 were observed for all women (12.6% per year [95% confidence interval {CI}, 10.6–14.5]), heterosexual men (13.0% per year [95% CI, 8.3–17.5]), and unvaccinated women (5.4% per year [95% CI, 2.9–7.8]). We observed significant declines in HPV-31 (all women and heterosexual men), HPV-45 (all women), and in all high-risk HPV types pooled (all women and heterosexual men). Significant increases were observed for HPV-56 (all women) and HPV-52 (unvaccinated women).

Conclusions

Our results provide evidence for first-order herd effects among heterosexual men against HPV-16/18 and cross-protective types. Additionally, we show second-order herd effects against vaccine types among unvaccinated women. These results are promising regarding population-level and clinical impact of girls-only bivalent HPV vaccination in a country with moderate vaccine uptake.

Human Papillomavirus Distribution in Women with Abnormal Pap Smear and/or Cervical Intraepithelial Neoplasia in Vaccination Era. A Single-Center Study in the North Italian Population

Time trends prevalence of human papillomavirus (HPV) genotypes including negative and untypable infections were analyzed during a 15-year period (2005–2019) among 5807 subjects with abnormal pap-smears and/or cervical intraepithelial neoplasia (CIN). The rates of HPV16 dropped by 13% every 3 years (Prevalence Ratio, PR = 0.87, 95% CI = 0.82–0.93) in the CIN1 biopsy, while HPV16 status was unchanged over time in the CIN2+ biopsy. In CIN1 lesions, there was a corresponding increase of HR-HPV types unrelated to nonavalent vaccine. The rates of HPV 18, 31, and 52, decreased by 35% (PR = 0.65, 95% CI = 0.54–0.79), 19% (PR = 0.81, 95% CI = 0.73–0.91), and 21% (PR = 0.79, 95% CI = 0.73–0.86) every 3-year interval in CIN2+, respectively. Overall, the prevalence of negative/untypable HPV specimens in the entire database increased from 9.6% (129/1349) in the period 2011–2013 to 17.6% (161/913) and 28.4% (224/790) in the 2014–2016 period and in the 2017–2019 period, respectively (PR = 1.69, 95% CI = 1.52–1.88). HPV 16 prevalence decreased significantly among subjects with low-grade cervical squamous lesions. A significant increase of both HPV types unrelated to nonavalent vaccination and negative/untypable HPV infections was reported. The prevalence of HPV types among subjects with abnormal pap smears in Northern Italy is changing. Many variables including demographic factors and possibly vaccination could be responsible for this modification.

Concurrent infection with multiple human papillomavirus types among unvaccinated and vaccinated 17-year-old Norwegian girls

Background

Whether type-specific human papillomavirus (HPV) infection influences the risk of acquiring infections with other HPV types is unclear. We studied concurrent HPV infections in 17-year-old girls from 2 birth cohorts; the first vaccine-eligible cohort in Norway and a prevaccination cohort.

Methods

Urine samples were collected and tested for 37 HPV genotypes. This study was restricted to unvaccinated girls from the prevaccination cohort (n = 5245) and vaccinated girls from the vaccine-eligible cohort (n = 4904). Risk of HPV infection was modelled using mixed-effect logistic regression. Expected frequencies of concurrent infection with each pairwise combination of the vaccine types and high-risk types (6/11/16/18/31/33/35/39/45/51/52/56/58/59) were compared to observed frequencies.

Results

Infection with multiple HPV types was more common among unvaccinated girls than vaccinated girls (9.2% vs 3.7%). HPV33 and HPV51 was the only HPV pair that was detected together more often than expected among both unvaccinated (P = .002) and vaccinated girls (P < .001). No HPV pairs were observed significantly less often than expected.

Conclusions

HPV33 and HPV51 tended to be involved in coinfection among both unvaccinated and vaccinated girls. The introduction of HPV vaccination does not seem to have had an effect on the tendency of specific HPV types to cluster together.

Clinical Significance of the Interaction between Human Papillomavirus (HPV) Type 16 and Other High-Risk Human Papillomaviruses in Women with Cervical Intraepithelial Neoplasia (CIN) and Invasive Cervical Cancer

The aim is to evaluate the clinical consequences of coinfection between HPV 16 and other high-risk HPVs among women with a histological diagnosis of CIN or invasive cervical cancer. A total of 2985 women, with a diagnosis of either CIN or cancer (<IB) on cervical or cone biopsy, were included. HPV genotypes were identified using the INNO-LiPA HPV genotyping assay, version EXTRA, on cervical scraping, before the colposcopic evaluation and the colposcopic biopsies or conization. In the overall population, HPV16 interacted positively with HPV18 (RR = 2, 95% CI 1.5–2.6) and negatively with HPV33, 51, 52, and 66, in log-linear analysis. There was an excess of CIN3 diagnoses among subjects coinfected with HPV16 and HPV18 or HPV52, although the absolute number of cases was relatively small. In a logistic model, the odds ratio of CIN3+ associated with coinfection of HPV16 and HPV18 (OR = 3.8, 95% CI 2.5–5.7, p=0.004 compared to single HPV16) or HPV52 (OR = 3.6, 95% CI 2.6–5.1, p=0.009 compared to single HPV) was higher than that associated with single HPV 16 infections. Finally, multiple infections had no effect on residual disease and did not influence the recurrence of high-grade CIN during a median follow-up of 25 months (IR 17–41). HPV16 interacted positively with HPV18 and negatively with HPV33, 51, 52, and 66 supporting the notion that HPV16 interacts mostly negatively with other HR-HPVs in CIN lesions. Among specimens coinfected with HPV16 and 18 or 52, there was an excess of CIN3+ although the impact on the prevalence of severe cervical lesions was limited.

The relationship of human papillomavirus infection with endocervical glandular involvement on cone specimens in women with cervical intraepithelial neoplasia

OBJECTIVE

The aim of study was to evaluate the association of endocervical gland involvement (EGI) on histological samples with high risk (HR) human papillomavirus (HPV) infection and with the persistence/recurrence rate of cervical intraepithelial neoplasia (CIN) after treatment.

METHODS

A total of 1301 subjects who had conization procedures after cervical punch biopsies (533 persistent CIN1, 768 CIN2+ including 20 microinvasive cervical cancer) were enrolled in the study. HPV genotypes were identified using the INNO-LiPA HPV genotyping assay on cervical scraping. Logistic regression and Cox regression analyses were used to evaluate the association of EGI on the persistence/recurrence rate of CIN after treatment.

RESULTS

The rate of EGI on final histology was 46.3% (602/1301). HPV 16 was the only HR-HPV significantly associated with increasing rates of EGI (231/602 as compared to 211/699, p = 0.002). EGI was also associated with an excess of multiple HR-HPV infections (237/602 as compared with 225/699, p = 0.006). After correction for confounders, the odds ratio of EGI among women infected by HPV 16 was 1.41 (95% CI = 1.12-178). CIN2+ lesions were diagnosed in 40.5% (283/699) of EGI negative subjects and 86.7% (522/602, p < 0.001 compared to negative subjects) of EGI positive subjects.After a median of 25 months of follow-up (IQR = 15-47) of 1090 treated women, the persistence of HPV 16 during follow-up was 38.1% (93/217, p = 0.03 compared to EGI negative) among EGI positive and 32% (58/181) among controls. After corrections for potential confounders, the odds ratio of CIN2+ persistence and or recurrence was higher among EGI positive (OR = 2.35, 95% CI = 1.16-4.77) than negative controls.

CONCLUSION

EGI on histological samples is associated with increased rates of HPV 16, multiple high risk-HPV infections and CIN2+ lesions. EGI positive subjects also had an increased CIN recurrence/persistence after treatment compared to controls.

Capturing multiple-type interactions into practical predictors of type replacement following human papillomavirus vaccination

Current HPV vaccines target a subset of the oncogenic human papillomavirus (HPV) types. If HPV types compete during infection, vaccination may trigger replacement by the non-targeted types. Existing approaches to assess the risk of type replacement have focused on detecting competitive interactions between pairs of vaccine and non-vaccine types. However, methods to translate any inferred pairwise interactions into predictors of replacement have been lacking. In this paper, we develop practical predictors of type replacement in a multi-type setting, readily estimable from pre-vaccination longitudinal or cross-sectional prevalence data. The predictors we propose for replacement by individual non-targeted types take the form of weighted cross-hazard ratios of acquisition versus clearance, or aggregate odds ratios of coinfection with the vaccine types. We elucidate how the hazard-based predictors incorporate potentially heterogeneous direct and indirect type interactions by appropriately weighting type-specific hazards and show when they are equivalent to the odds-based predictors. Additionally, pooling type-specific predictors proves to be useful for predicting increase in the overall non-vaccine-type prevalence. Using simulations, we demonstrate good performance of the predictors under different interaction structures. We discuss potential applications and limitations of the proposed methodology in predicting type replacement, as compared to existing approaches. This article is part of the theme issue 'Silent cancer agents: multi-disciplinary modelling of human DNA oncoviruses'.

Inferring Pathogen Type Interactions Using Cross-sectional Prevalence Data: Opportunities and Pitfalls for Predicting Type Replacement

BACKGROUND

Many multivalent vaccines target only a subset of all pathogenic types. If vaccine and nonvaccine types compete, vaccination may lead to type replacement. The plausibility of type replacement has been assessed using the odds ratio (OR) of co-infections in cross-sectional prevalence data, with OR > 1 being interpreted as low risk of type replacement. The usefulness of the OR as a predictor for type replacement is debated, as it lacks a theoretical justification, and there is no framework explaining under which assumptions the OR predicts type replacement.

METHODS

We investigate the values that the OR can take based on deterministic S usceptible- I infected- S usceptible and S usceptible- Infected- Recovered- S usceptible multitype transmission models. We consider different mechanisms of type interactions and explore parameter values ranging from synergistic to competitive interactions.

RESULTS

We find that OR > 1 might mask competition because of confounding due to unobserved common risk factors and cross-immunity, as indicated by earlier studies. We prove mathematically that unobserved common risk factors lead to an elevation of the OR, and present an intuitive explanation why cross-immunity increases the OR. We find that OR < 1 is predictive for type replacement in the absence of immunity. With immunity, OR < 1 remains predictive under biologically reasonable assumptions of unidirectional interactions during infection, and an absence of immunity-induced synergism.

CONCLUSIONS

Using the OR in cross-sectional data to predict type replacement is justified, but is only unambiguous under strict assumptions. An accurate prediction of type replacement requires pathogen-specific knowledge on common risk factors and cross-immunity.

Distinct geographic clustering of oncogenic human papillomaviruses multiple infections in cervical cancers: Results from a worldwide cross-sectional study

Coinfections by multiple Human Papillomaviruses (HPVs) are observed in approximately 6-8% of invasive cervical cancer (ICC) cases worldwide. But neither the presence of persistent HPVs coinfections nor their etiological role in the development of ICC is well understood. Cervical HPVs coinfections have been observed randomly, mostly in women with preneoplastic lesions, and only few studies have globally analyzed ICC cases. Here we explored the HPVs multiple infection patterns in a large worldwide sample of cross-sectional ICC cases. Paraffin-embedded ICC biopsy samples were tested using stringent HPV genotyping. Logistic regression models were used to identify the most likely pairwise HPV types in multiple infections. Multivariate analysis was applied to detect significant HPV coinfection patterns beyond pairwise HPVs comparison. Among 8780 HPV DNA-positive ICC cases worldwide, 6.7% (N = 587) contained multiple HPVs. Pairwise analysis revealed that HPV16|74, HPV31|33, HPV31|44, HPV33|44 and HPV45|70 pairs were significantly more frequently found together in multiple infections compared to any other HPV type combination, which supports the occasional role of Alpha-10 LR-HPVs in cervical cancers. In contrast, HPV16|31, HPV16|45, HPV16|51 and HPV18|HPV45 pairs were significantly less frequently found together than with any other HPV pair combination. Multivariate analysis sustained the results and revealed for the first time a distinct coinfection pattern in African ICCs stemming from the clustering of oncogenic HPV51/35/18/52 coinfections in African women. We suggest that the differential geographic HPVs coinfections clustering observed might be compatible with a specific modulation of the natural history/oncogenic potential of particular HPVs multiple infections and warrant monitoring for post-vaccinated.

Common types of infection with multitypes of HPV on uterine cervix

Persistent infection by human papillomavirus (HPV) is an important factor causing cervical cancer. In recent years, infection with multiple HPV types has been confirmed in various studies. High-risk HPV 16 and 18 and low-risk HPV 6 are the most common causes of multitype HPV infection. Infection with multiple types of HPV, which results from individual susceptibility, is crucial in tumor susceptibility. This paper summarizes the common types of multiple HPV infection to enable further research on the relationship between HPV and tumor susceptibility.

Prevalence of Genital Human Papillomavirus Among Sexually Experienced Males and Females Aged 14-59 Years, United States, 2013-2014

Background

Differences in human papillomavirus (HPV) prevalence among males and females have been reported. Using the 2013-2014 National Health and Nutrition Examination Survey, we evaluated sex differences in prevalence overall and by demographic and sexual behavior characteristics.

Methods

Self-collected penile and cervicovaginal swabs from participants aged 14-59 were tested for HPV DNA. Prevalences of any HPV and high-risk HPV (HR-HPV) were estimated for sexually experienced males and females. Overall and in models stratified by demographic characteristics and behaviors, prevalence was compared in males and females using prevalence ratios (PR).

Results

Overall, males had higher prevalence than females of any HPV (PR, 1.14; 95% confidence interval [CI], 1.03-1.27) and HR-HPV (PR, 1.24; 95% CI, 1.07-1.43). Prevalences were lower among males than females at ages 14-19 and higher at ages 40-49 and 50-59. Sex differences in models stratified by race/ethnicity, poverty, sexual behaviors, and smoking were observed. After adjusting for lifetime sex partners, most sex differences were attenuated, but males had lower prevalences at ages 14-19 and 20-24 and higher HR-HPV prevalence among non-Hispanic blacks.

Conclusions

Any HPV and HR-HPV prevalences were significantly higher in males; sex differences varied by age group and race/ethnicity. Lifetime partners explained many of the differences by sex.

Epidemiologic Evaluation of Human Papillomavirus Type Competition and the Potential for Type Replacement Post-Vaccination

Background

Millions of women have been vaccinated with one of two first-generation human papillomavirus (HPV) vaccines. Both vaccines remain in use and target two oncogenic types (HPVs 16 and 18); however, if these types naturally compete with others that are not targeted, type replacement may occur following reductions in the circulating prevalence of targeted types. To explore the potential for type replacement, we evaluated natural HPV type competition in unvaccinated females.

Methods

Valid HPV DNA typing information was available from five epidemiological studies conducted in Canada and Brazil (n = 14,685; enrollment across studies took place between1993 and 2010), which used similar consensus-primer PCR assays, capable of detecting up to 40 HPV types. A total of 38,088 cervicovaginal specimens were available for inclusion in our analyses evaluating HPV type-type interactions involving vaccine-targeted types (6, 11, 16, and 18), and infection with each of the other HPV types.

Results

Across the studies, the average age of participants ranged from 21.0 to 43.7 years. HPV16 was the most common type (prevalence range: 1.0% to 13.8%), and in general HPV types were more likely to be detected as part of a multiple infection than as single infections. In our analyses focusing on each of the vaccine-targeted HPV types separately, many significant positive associations were observed (particularly involving HPV16); however, we did not observe any statistically significant negative associations.

Conclusions

Our findings suggest that natural HPV type competition does not exist, and that type replacement is unlikely to occur in vaccinated populations.

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.

An anal cancer screening program for MSM in Italy: Prevalence of multiple HPV types and vaccine-targeted infections

BACKGROUND

Elevated HPV infection rates have been described in HIV-positive males, placing these subjects at high risk of anal neoplasia. Bivalent, quadrivalent, and nonavalent vaccines to prevent HPV infection have been developed, and recently proposed for gender-neutral immunization programs.

OBJECTIVES

In order to estimate the benefit that could be obtained by vaccination of HIV-positive men who have sex with men (MSM), we aimed at describing the frequency of multiple and vaccine-targeted HPV infections in MSM enrolled in an anal cancer screening program.

STUDY DESIGN

The anal cancer screening program was conducted between July 2009 and October 2012. Mucosal anal samples were tested for HPV DNA using MY09/MY11 PCR primers and, if positive, genotyped using the CLART2HPV Clinical Array (35HPV types).

RESULTS

A total of 220 MSM were screened and 88.6% were positive for HPV DNA: in 86.5% at least one high-risk (HR) type was found and in 13% only low-risk (LR) HPV were found. Multiple infections accounted for 84.5% of HPV DNA-positive cases and overall 160 different HPV genotype combinations were recognized (only three combinations were detected in more than one patient each). Based on strain coverage, at least one vaccine-targeted HPV type was found in 38.9%, 64%, and 78.4% of cases when considering bivalent, quadrivalent and nonavalent vaccines, respectively. At least one HR vaccine-targeted strain was found in 39% of MSM for bivalent and quadrivalent vaccines, and in 64% of cases for nonavalent prevention.

CONCLUSIONS

Anal HPV infections in unvaccinated mostly HIV-infected MSM are highly prevalent. The majority of this population has multiple infections with an extremely heterogeneous number of genotype combinations. The nonavalent vaccine could theoretically have prevented a minimum of one HR HPV type in two thirds of subjects.

Invited commentary: multiple human papillomavirus infections and type replacement-anticipating the future after human papillomavirus vaccination

Prophylactic human papillomavirus (HPV) vaccination with 3 doses of either of 2 commercially available vaccines is highly efficacious in preventing infections with the most carcinogenic types of HPV (HPV 16 and HPV 18) at the cervix and other anatomical sites at which HPV-related cancers develop. Concern has been raised that eradicating the most virulent HPV types, 16 and 18, could result in 1 or more of the types that are not targeted by the vaccine occupying the ecological niche created by the elimination of these types, referred to as type replacement. In this issue of the Journal, Yang et al. (Am J Epidemiol. 2014;180(11):1066-1075) report on concurrent infections with multiple HPV types in unvaccinated women who underwent cervical screening in New Mexico (December 2007-April 2009) to identify possible interactions between HPV types, which if present could suggest the possibility of type replacement. Consistent with previous reports, they show minimal type-specific interactions among women with normal cytology, which they consider an indication that type replacement of HPV 16/18 is unlikely to be an issue in the general population postvaccination. Type replacement may be of less concern with the introduction of multivalent vaccines that include most of the carcinogenic HPV types; continued surveillance postvaccination should improve our understanding of the impact of HPV vaccination on type distribution and screening performance.