Exploring individual HPV coinfections is essential to predict HPV-vaccination impact on genotype distribution: a model-based approach

Cervical cancer: Part I human papilloma virus vaccination in Taiwan

A significant decline in both incidence and prevalence of cervical cancers after widespread-introducing cervical screening strategy by Papanicolau test (Pap test) has been found in the world, but cervical cancer is still one of the most common female cancers, reporting the fourth prevalence and also one of the leading causes to result in main women-associated morbidity and mortality, particularly for those women living in low- and middle-income countries. Cervical cancer is one of the most important health concerns directly destroying the global health-care system, partly because of not only increasing the disability either secondary to diseases themselves of victims or mediated by treatment-related adverse events to the survivors but also acting as a leading cause of death of diseased patients worldwide, alarming the urgent need to do something to minimize the catastrophic diseases-related heavy socioeconomic burden. It is fortunate that cervical cancer is a preventable disease, based on its strong association with human papillomavirus (HPV) infection (more than 95%), particularly for those high-risk HPV (HR-HPV) and its high possibility by detecting HPV infection before the development of cervical cancer as well as an effective prevention by HPV vaccination. That is why WHO (World Health Organization) considers cervical cancer as a public problem and attempts to accelerate the elimination of cervical cancer program by three-pillar approach (90:70:90% targets), including (1) 90% of girls are fully vaccinated with HPV vaccine by 15 years of age; (2) 70% of women are screened with a high-performance test by 35 and 45 years of age and precancerous lesions are treated early; and (3) 90% of women identified with cervical diseases receive appropriate and adequate treatment. Herein, this review focuses on the HPV vaccination as Part I, including global recommendations and Taiwan government's policy for HPV vaccination.

Coinfections in human papillomavirus associated cancers and prophylactic recommendations

The Human Papillomavirus (HPV) infection is responsible for more than 80% of reported cervical cancer and other virus-associated tumours. Although this global threat can be controlled using effective vaccination strategies, a growing perturbation of HPV infection is an emerging coinfection likely to increase the severity of the infection in humans. Moreover, these coinfections prolong the HPV infections, thereby risking the chances for oncogenic progression. The present review consolidated the clinically significant microbial coinfections/co-presence associated with HPV and their underlying molecular mechanisms. We discussed the gaps and concerns associated with demography, present vaccination strategies, and other prophylactic limitations. We concluded our review by highlighting the potential clinical as well as emerging computational intervention measures to kerb down HPV-associated severities.

Reducing Poverty-Related Disparities in Cervical Cancer: The Role of HPV Vaccination

BACKGROUND

Near elimination of cervical cancer in the United States is possible in coming decades, yet inequities will delay this achievement for some populations. We sought to explore the effects of human papillomavirus (HPV) vaccination on disparities in cervical cancer incidence between high- and low-poverty U.S. counties.

METHODS

We calibrated a dynamic simulation model of HPV infection to reflect average counties in the highest and lowest quartile of poverty (percent of population below federal poverty level), incorporating data on HPV prevalence, cervical cancer screening, and HPV vaccination. We projected cervical cancer incidence through 2070, estimated absolute and relative disparities in incident cervical cancer for high- versus low-poverty counties, and compared incidence with the near-elimination target (4 cases/100,000 women annually).

RESULTS

We estimated that, on average, low-poverty counties will achieve near-elimination targets 14 years earlier than high-poverty counties (2029 vs. 2043). Absolute disparities by county poverty will decrease, but relative differences are estimated to increase. We estimate 21,604 cumulative excess cervical cancer cases in high-poverty counties over the next 50 years. Increasing HPV vaccine coverage nationally to the Healthy People 2020 goal (80%) would reduce excess cancer cases, but not alter estimated time to reach the near-elimination threshold.

CONCLUSIONS

High-poverty U.S. counties will likely be delayed in achieving near-elimination targets for cervical cancer and as a result will experience thousands of potentially preventable cancers.

IMPACT

Alongside vaccination efforts, it is important to address the role of social determinants and health care access in driving persistent inequities by area poverty.

Interplay between competitive and cooperative interactions in a three-player pathogen system

In ecological systems, heterogeneous interactions between pathogens take place simultaneously. This occurs, for instance, when two pathogens cooperate, while at the same time, multiple strains of these pathogens co-circulate and compete. Notable examples include the cooperation of human immunodeficiency virus with antibiotic-resistant and susceptible strains of tuberculosis or some respiratory infections with Streptococcus pneumoniae strains. Models focusing on competition or cooperation separately fail to describe how these concurrent interactions shape the epidemiology of such diseases. We studied this problem considering two cooperating pathogens, where one pathogen is further structured in two strains. The spreading follows a susceptible-infected-susceptible process and the strains differ in transmissibility and extent of cooperation with the other pathogen. We combined a mean-field stability analysis with stochastic simulations on networks considering both well-mixed and structured populations. We observed the emergence of a complex phase diagram, where the conditions for the less transmissible, but more cooperative strain to dominate are non-trivial, e.g. non-monotonic boundaries and bistability. Coupled with community structure, the presence of the cooperative pathogen enables the coexistence between strains by breaking the spatial symmetry and dynamically creating different ecological niches. These results shed light on ecological mechanisms that may impact the epidemiology of diseases of public health concern.

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.

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.

Comparison of the performance of Anyplex II HPV HR, the Cobas 4800 human papillomavirus test and Hybrid Capture 2

BACKGROUND

Anyplex II HPV HR (Anyplex_HR; Seegene, Seoul, Korea) is a new multiplex real-time polymerase chain reaction assay for screening cervical cancer, and it is designed to detect 14 high-risk human papillomaviruses along with all the genotype information in a single tube. The aim of this study was to evaluate the performance of the Anyplex_HR in comparison to that of the Cobas 4800 HPV (Cobas_4800; Roche Molecular Diagnostics, Pleasanton, CA, USA) and the Hybrid capture 2 (HC2; Qiagen GmbH, Hilden, Germany).

METHODS

The performance of the Anyplex_HR for high-risk human papillomavirus genotype detection was prospectively evaluated against that of the HC2 and the Cobas_4800 at the National Cancer Center using 400 cervical samples. All discrepant samples were confirmed by polymerase chain reaction with type-specific primers followed by sequencing.

RESULTS

The overall agreement and kappa value of the Anyplex_HR with the Cobas_4800 were 98.0% and 0.96, respectively. The level of agreement between the two assays and the corresponding kappa values for human papillomavirus16, human papillomavirus18 and other high-risk human papillomaviruses were 99.5%, 99.8% and 98.8%, and 0.98, 0.96 and 0.97, respectively. The agreement and kappa value of the HC2 with the Cobas_4800 were 95.3% and 0.91. The human papillomavirus positivity of the Anyplex_HR and the Cobas_4800 in low-grade squamous intraepithelial lesion/high-grade squamous intraepithelial lesion samples demonstrated 100% concordance. Both the Anyplex_HR and the Cobas_4800 showed excellent results in the precision test.

CONCLUSIONS

The Anyplex_HR is comparable with the Cobas_4800 and the HC2 for human papillomavirus DNA testing, and it may prove more useful for follow-up testing and patient management by providing genotyping information additional to human papillomavirus16 and human papillomavirus18.

Prevalence of type-specific HPV among female university students from northern Brazil

Background

Human papillomavirus (HPV) infection is associated with cervical cancer, the most frequent cancer in women from northern Brazil. Assessment of the short-term impact of HPV vaccination depends on the availability of data on the prevalence of type-specific HPV in young women in the pre-immunization period, although these data are currently unavailable for the study region. The aim of this study was to estimate the distribution of all mucosal HPV genotypes, including low- and high-risk HPV types, in unvaccinated college students from northern Brazil.

Findings

Specimens were collected from 265 university students during routine cervical cancer screening. The HPV DNA was assessed by Polymerase Chain Reaction and positive samples were genotyped by Restriction Fragment Length Polymorphism. Most students (85.7 %) had normal cytological results. The prevalence of HPV was 25.3 % (67/265), with a high frequency of multiple infections and non-vaccine high-risk HPV genotypes. The most prevalent type was HPV-61 (5.3 %), followed by types 82, 16, 59, and 6. Multiple infections were associated with high-risk and possibly high-risk HPVs.

Conclusions

We demonstrated a high prevalence of HPV infection in university students from northern Brazil. Vaccine high-risk types were relatively rare, emphasizing the predominance of carcinogenic genotypes that are not prevented by the currently available vaccines. Our study highlights the need to reinforce cytological screening in women from northern Brazil, and promote the early diagnosis and treatment of the precancerous lesions associated with cervical cancer.

Papillomaviruses: Viral evolution, cancer and evolutionary medicine

Papillomaviruses (PVs) are a numerous family of small dsDNA viruses infecting virtually all mammals. PVs cause infections without triggering a strong immune response, and natural infection provides only limited protection against reinfection. Most PVs are part and parcel of the skin microbiota. In some cases, infections by certain PVs take diverse clinical presentations from highly productive self-limited warts to invasive cancers. We propose PVs as an excellent model system to study the evolutionary interactions between the immune system and pathogens causing chronic infections: genotypically, PVs are very diverse, with hundreds of different genotypes infecting skin and mucosa; phenotypically, they display extremely broad gradients and trade-offs between key phenotypic traits, namely productivity, immunogenicity, prevalence, oncogenicity and clinical presentation. Public health interventions have been launched to decrease the burden of PV-associated cancers, including massive vaccination against the most oncogenic human PVs, as well as systematic screening for PV chronic anogenital infections. Anti-PVs vaccines elicit protection against infection, induce cross-protection against closely related viruses and result in herd immunity. However, our knowledge on the ecological and intrapatient dynamics of PV infections remains fragmentary. We still need to understand how the novel anthropogenic selection pressures posed by vaccination and screening will affect viral circulation and epidemiology. We present here an overview of PV evolution and the connection between PV genotypes and the phenotypic, clinical manifestations of the diseases they cause. This differential link between viral evolution and the gradient cancer-warts-asymptomatic infections makes PVs a privileged playground for evolutionary medicine research.

In vitro assessment of the effect of vaccine-targeted human papillomavirus (HPV) depletion on detection of non-vaccine HPV types: implications for post-vaccine surveillance studies

In populations where the prevalence of vaccine-targeted HPV types has been reduced significantly due to widespread vaccination of the target population, the sensitivity of some consensus PCR-based assays to detect remaining HPV types may be altered, leading to misrepresentations of prevalence. Importantly, this may lead to false indications of type replacement in vaccinated populations. To assess whether excess vaccine-targeted HPV DNA resulted in reduced detection of other genotypes on the Roche HPV linear array genotype assay, simulated samples containing 1000 copies of one or two high-risk HPV DNA genomes in the presence and the absence of 10,000 copies of the HPV16 genome were tested. HPV16 alone did not affect detection of other high-risk genotypes; however when HPV16 and an additional genotype were present, detection of HPV31, 33, 51 or 59 was impeded, indicating potential for misrepresentation of population-based prevalence of these genotypes and false evidence for type replacement following vaccination.

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

In view of possible type replacement upon introduction of human papillomavirus (HPV) vaccination, we aimed to explore patterns of type-specific clustering across populations with various background infection risks. A total of 3,874 women from 3 cross-sectional studies in the Netherlands (in 2007-2009) provided vaginal self-samples, which were tested for 25 HPV genotypes by a sensitive molecular assay (SPF10 line probe assay, DDL Diagnostic Laboratory, Voorburg, the Netherlands). The number of concurrent HPV infections per woman was studied by Poisson regression. Associations between HPV types were investigated by generalized estimating equation analyses. The prevalence of any HPV type was 14% in a population-based study, 54% in a chlamydia screening intervention study, and 73% in a study among attendees of sexually transmitted infection clinics. Overall, multiple HPV infections were detected in 26% of the women. The number of concurrent HPV infections conformed to an overdispersed Poisson distribution, even after correction for known risk factors. Types differed significantly in their tendencies to be involved in coinfections, but no evidence for particular type-type interactions was found. Moreover, the strongest associations were observed in the lowest-risk population and vice versa.We found no indications of pairwise interactions, but our findings do suggest that clustering differs among HPV types and varies across risk groups.

Human papillomavirus community in healthy persons, defined by metagenomics analysis of human microbiome project shotgun sequencing data sets

Human papillomavirus (HPV) causes a number of neoplastic diseases in humans. Here, we show a complex normal HPV community in a cohort of 103 healthy human subjects, by metagenomics analysis of the shotgun sequencing data generated from the NIH Human Microbiome Project. The overall HPV prevalence was 68.9% and was highest in the skin (61.3%), followed by the vagina (41.5%), mouth (30%), and gut (17.3%). Of the 109 HPV types as well as additional unclassified types detected, most were undetectable by the widely used commercial kits targeting the vaginal/cervical HPV types. These HPVs likely represent true HPV infections rather than transitory exposure because of strong organ tropism and persistence of the same HPV types in repeat samples. Coexistence of multiple HPV types was found in 48.1% of the HPV-positive samples. Networking between HPV types, cooccurrence or exclusion, was detected in vaginal and skin samples. Large contigs assembled from short HPV reads were obtained from several samples, confirming their genuine HPV origin. This first large-scale survey of HPV using a shotgun sequencing approach yielded a comprehensive map of HPV infections among different body sites of healthy human subjects.

IMPORTANCE

This nonbiased survey indicates that the HPV community in healthy humans is much more complex than previously defined by widely used kits that are target selective for only a few high- and low-risk HPV types for cervical cancer. The importance of nononcogenic viruses in a mixed HPV infection could be for stimulating or inhibiting a coexisting oncogenic virus via viral interference or immune cross-reaction. Knowledge gained from this study will be helpful to guide the designing of epidemiological and clinical studies in the future to determine the impact of nononcogenic HPV types on the outcome of HPV infections.

Comparing human papillomavirus prevalences in women with normal cytology or invasive cervical cancer to rank genotypes according to their oncogenic potential: a meta-analysis of observational studies

BACKGROUND

Mucosal human papillomavirus (HPV) infection is a necessary cause of cervical cancer. Vaccine and non-vaccine genotype prevalences may change after vaccine introduction. Therefore, it appears essential to rank HPV genotypes according to their oncogenic potential for invasive cervical cancer, independently of their respective prevalences.

METHODS

We performed meta-analyses of published observational studies and estimated pooled odds ratios with random-effects models for 32 HPV genotypes, using HPV-16 as the reference.

RESULTS

Twenty-seven studies yielded 9,252 HPV-infected women: 2,902 diagnosed with invasive cervical cancer and 6,350 with normal cytology. Expressed as (odds ratio [95% confidence interval]), HPV-18 (0.63 [0.51, 0.78]) ranked closest to HPV-16, while other genotypes showed continuously decreasing relative oncogenic potentials: HPV-45 (0.35 [0.22, 0.55]), HPV-69 (0.28 [0.09, 0.92]), HPV-58 (0.24 [0.15, 0.38]), HPV-31 (0.22 [0.14, 0.35]), HPV-33 (0.22 [0.12, 0.38]), HPV-34 (0.21 [0.06, 0.80]), HPV-67 (0.21 [0.06, 0.67]), HPV-39 (0.17 [0.09, 0.30]), HPV-59 (0.17 [0.09, 0.31]), HPV-73 (0.16 [0.06, 0.41]), and HPV-52 (0.16 [0.11, 0.23]).

CONCLUSIONS

Our results support the markedly higher oncogenic potentials of HPV-16 and -18, followed by HPV-31, -33, -39, -45, -52, -58 and -59, and highlight the need for further investigation of HPV-34, -67, -69 and -73. Overall, these findings could have important implications for the prevention of cervical cancer.