Activities of human papillomavirus 16 E6 natural variants in human keratinocytes

The imprint of viral oncoproteins on the variable clinical behavior among human papilloma virus-related oropharyngeal squamous cell carcinomas

Human papilloma virus-related (HPV+) oropharyngeal squamous cell carcinomas (OPSCCs) are variable in their progression, immune landscape, treatment responses, and clinical outcomes. Their behavior is impacted not only by differences in host genomic alterations but also by diversity in levels and activity of HPV-encoded oncoproteins. Striking differences in HPV mRNA levels are found among HPV+ OPSCCs and likely derive in part from variations in the structurally diverse mix of integrated and episomal HPV genomes they often contain. Viral oncoprotein levels and function are also impacted by differential splicing of the two long polycistronic transcripts of HPV16, the HPV type within most HPV+ OPSCCs. Further variation in viral oncoprotein function arises from the distinct lineages and sub-lineages of HPV16, which encode polymorphisms in functionally important portions of oncogenes. Here we review the limited current knowledge linking HPV mRNA expression and splicing to differences in oncoprotein function that likely influence OPSCC behavior. We also summarize the evolving understanding of HPV16 physical genome state and genetic variants and their potential contributions to HPV oncoprotein levels and function. Addressing considerable remaining challenges in defining the quantitative and qualitative imprint of HPV oncoproteins on each OPSCC holds promise to guide personalization of therapy for this disease.

Why HPV16? Why, now, HPV42? How the discovery of HPV42 in rare cancers provides an opportunity to challenge our understanding about the transition between health and disease for common members of the healthy microbiota

In 2022, a bioinformatic, agnostic approach identified HPV42 as causative agent of a rare cancer, later confirmed experimentally. This unexpected association offers an opportunity to reconsider our understanding about papillomavirus infections and cancers. We have expanded our knowledge about the diversity of papillomaviruses and the diseases they cause. Yet, we still lack answers to fundamental questions, such as what makes HPV16 different from the closely related HPV31 or HPV33; or why the very divergent HPV13 and HPV32 cause focal epithelial hyperplasia, while HPV6 or HPV42 do not, despite their evolutionary relatedness. Certain members of the healthy skin microbiota are associated to rare clinical conditions. We propose that a focus on cellular phenotypes, most often transient and influenced by intrinsic and extrinsic factors, may help understand the continuum between health and disease. A conceptual switch is required towards an interpretation of biology as a diversity of states connected by transition probabilities, rather than quasi-deterministic programs. Under this perspective, papillomaviruses may only trigger malignant transformation when specific viral genotypes interact with precise cellular states. Drawing on Canguilhem's concepts of normal and pathological, we suggest that understanding the transition between fluid cellular states can illuminate how commensal-like infections transition from benign to malignant.

HPV16 E7 oncoprotein test as a triage strategy for HPV16-positive women in cervical cancer screening: long-term follow-up outcome

Background

Colposcopy is recommended once human papillomavirus (HPV)16/18 infection is detected. However, not all HPV16/18-positive women will necessarily develop cervical lesions. Therefore, this study aimed to investigate the application of quantitative HPV16 E7 oncoprotein detection as a cervical cancer screening method for more efficient screening while minimizing unnecessary colposcopy.

Methods

E7 oncoprotein (HPV16) was quantitatively detected in cervical exfoliated cells of HPV16-positive women. The levels of HPV16 E7 oncoprotein in different degrees of cervical lesions were compared, and the optimal cut-off value for identifying HSIL+ was determined by receiver operating characteristic (ROC) curve analysis. With a pathological diagnosis as the gold standard, the sensitivity (SEN), specificity (SPE), positive predictive value (PPV), negative predictive value (NPV), and Kappa value were calculated to verify the diagnostic value of the method. Women diagnosed with low-grade squamous intraepithelial lesions (LSIL) and normal women were followed up for 5 years to evaluate the predictive value of HPV16 E7 protein for disease progression/persistent infection.

Results

The expression level of HPV16 E7 oncoprotein was positively correlated with the degree of the cervical lesion (r = 0.589, P < 0.01). The area under the ROC curve (AUC) was 0.817 (confidence interval: 0.729-0.904). The cut-off value of E7 oncoprotein for identifying HSIL+ was 8.68 ng/ml. The SEN, SPE, PPV, NPV, and Kappa values of HPV16 E7 oncoprotein for the identification of HSIL+ were 87.1%,70.0%, 87.1%, 70.0%, and 0.571, respectively, which were higher than those of ThinPrep cytology test (TCT). The SEN, SPE, PPV, and NPV of HPV16 E7 oncoprotein in predicting disease progression/persistent infection were 93.75%, 91.30%, 88.24%, and 95.45%, respectively.

Conclusion

The quantitative detection of HPV 16 E7 oncoprotein can not only accurately screen cervical lesions but also achieve efficient colposcopy referral. Additionally, HPV16 E7 oncoprotein can accurately predict the progression of cervical lesions and persistent HPV infection.

Deep Sequencing of HPV16 E6 Region Reveals Unique Mutation Pattern of HPV16 and Predicts Cervical Cancer

The genetic diversity of human papillomavirus (HPV) 16 within cervical cells and tissue is usually associated with persistent virus infection and precancerous lesions. To explore the HPV16 mutation patterns contributing to the cervical cancer (CC) progression, a total of 199 DNA samples from HPV16-positive cervical specimens were collected and divided into high‐grade squamous intraepithelial lesion (HSIL) and the non‐HSIL(NHSIL) groups. The HPV16 E6 region (nt 7125-7566) was sequenced using next-generation sequencing. Based on HPV16 E6 amino acid mutation features selected by Lasso algorithm, four machine learning approaches were used to establish HSIL prediction models. The receiver operating characteristic was used to evaluate the model performance in both training and validation cohorts. Western blot was used to detect the degradation of p53 by the E6 variants. Based on the 13 significant mutation features, the logistic regression (LR) model demonstrated the best predictive performance in the training cohort (AUC = 0.944, 95% CI: 0.913–0.976), and also achieved a high discriminative ability in the independent validation cohort (AUC = 0.802, 95% CI: 0.601–1.000). Among these features, the E6 D32E and H85Y variants have higher ability to degrade p53 compared to the E6 wildtype (P < 0.05). In conclusion, our study provides evidence for the first time that HPV16 E6 sequences contain vital mutation features in predicting HSIL. Moreover, the D32E and H85Y variants of E6 exhibited a significantly higher ability to degrade p53, which may play a vital role in the development of CC.

IMPORTANCE The study provides evidence for the first time that HPV16 E6 sequences contain vital mutation features in predicting the high‐grade squamous intraepithelial lesion and can reduce even more unneeded colposcopies without a loss of sensitivity to detect cervical cancer. Moreover, the D32E and H85Y variants of E6 exhibited a significantly higher ability to degrade p53, which may play a vital role in the development of cervical cancer.

HPV16 E6 gene polymorphisms and the functions of the mutation site in cervical cancer among Uygur ethnic and Han nationality women in Xinjiang, China

BACKGROUND

To investigate the genotype distribution of human papillomavirus (HPV) in infected Uygur and Han women in Xinjiang, China; analyze the HPV16 E6 gene polymorphism site and relationship with the development of cervical cancer.

METHODS

The HPV16 E6 sequence was analyzed using the European standard prototype to perform an evolutionary tree. HPV16 E6-T295/T350, G295/G350, and T295/G350 GV230 vectors were stably transfected into cervical cancer C33A cells to analyze the cell proliferation, migration and invasion, apoptosis by CCK8 and clonogenic assays, transwell and cell scratch assays, FACS experiments.

RESULTS

The total HPV infection rate was 26.390% (760/2879), whereas the Uygur 22.87% (196/857) and the Han was 27.89% (564/2022) (P < 0.05). Among 110 mutations, 65 cases of E6 genes were mutated at nucleotide 350 (T350G) with the leucine changing to valine (L83V). Moreover, there were 7 cases of E6 gene mutated at nucleotide 295 (T295G) with aspartic changing to glutamic (D64E). When E6 vector(s) of mutations sites were transfected into C33A cells, they were found to promote cellular proliferation, migration, invasion, and inhibit apoptosis. T295/G350-E6 was significantly stronger than G295/G350 and T295/T350, G295/G350 was significantly stronger than T295/T350 (P < 0.05). The T295/G350 had the strongest effect on C33A cells and G295/G350 was significantly stronger than T295/T350 (P < 0.05).

CONCLUSIONS

The positive HPV infection rates differed between the Uygur and Han in Xinjiang, China, and the genotype distribution of infection was different. After transfecting C33A cells with different eukaryotic expression vectors, the T295/G350 mutation site promoted the proliferation, migration, and invasion of C33A cells to a greater extent than G295/G350; however, G295/G350 had a stronger effect than T295/T350.

Molecular insights into the interaction of HPV-16 E6 variants against MAGI-1 PDZ1 domain

Oncogenic protein E6 from Human Papilloma Virus 16 (HPV-16) mediates the degradation of Membrane-associated guanylate kinase with inverted domain structure-1 (MAGI-1), throughout the interaction of its protein binding motif (PBM) with the Discs-large homologous regions 1 (PDZ1) domain of MAG1-1. Generic variation in the E6 gene that translates to changes in the protein’s amino acidic sequence modifies the interaction of E6 with the cellular protein MAGI-1. MAGI-1 is a scaffolding protein found at tight junctions of epithelial cells, where it interacts with a variety of proteins regulating signaling pathways. MAGI-1 is a multidomain protein containing two WW (rsp-domain-9), one guanylate kinase-like, and six PDZ domains. PDZ domains played an important role in the function of MAGI-1 and served as targets for several viral proteins including the HPV-16 E6. The aim of this work was to evaluate, with an in silico approach, employing molecular dynamics simulation and protein–protein docking, the interaction of the intragenic variants E-G350 (L83V), E-C188/G350 (E29Q/L83V), E-A176/G350 (D25N/L83V), E6-AAa (Q14H/H78Y/83V) y E6-AAc (Q14H/I27RH78Y/L83V) and E6-reference of HPV-16 with MAGI-1. We found that variants E-G350, E-C188/G350, E-A176/G350, AAa and AAc increase their affinity to our two models of MAGI-1 compared to E6-reference.

E6/E7 Functional Differences among Two Natural Human Papillomavirus 18 Variants in Human Keratinocytes

It is suggested that HPV-18 variants from the A lineage have higher oncogenic potential compared to B variants. Some studies show uneven distribution of HPV-18 variants in cervical adenocarcinomas and squamous cell carcinomas. Regarding HPV-18 variants’ functions, the few studies reported focus on E6, and none were performed using natural host cells. Here, we immortalized primary human keratinocytes (PHKs) with E6/E7 of HPV-18 A1 and B1 sublineages and functionally characterized these cells. PHK18A1 reached immortalization significantly faster than PHK18B1 and formed a higher number of colonies in monolayer and 3D cultures. Moreover, PHK18A1 showed greater invasion ability and higher resistance to apoptosis induced by actinomycin-D. Nevertheless, no differences were observed regarding morphology, proliferation after immortalization, migration, or epithelial development in raft cultures. Noteworthy, our study highlights qualitative differences among HPV-18 A1 and B1 immortalized PHKs: in contrast to PHK18A1, which formed more compact colonies and spheroids of firmly grouped cells and tended to invade and migrate as clustered cells, morphologically, PHK18B1 colonies and spheroids were looser, and migration and invasion of single cells were observed. Although these observations may be relevant for the association of these variants with cervical cancer of different histological subtypes, further studies are warranted to elucidate the mechanisms behind these findings.

HPV genotype is a prognosticator for recurrence of respiratory papillomatosis in children

OBJECTIVES

This study aimed to compare the prognosis according to age, genotype or human papillomavirus (HPV) variant in patients with recurrent respiratory papillomatosis (RRP).

DESIGN

Non-concurrent cohort.

PARTICIPANTS

Forty one patients with RRP.

SETTING

Tertiary referral hospital.

MAIN OUTCOME MEASURES

Disease severity was defined by the number of surgeries performed, and Derkay score at surgeries, obtained from medical records. HPV was detected and genotyped, and HPV-6 variants were also assessed.

RESULTS

Fifteen (36.58%) individuals belonged to the juvenile RRP group (JoRRP, less than 18 years), while 26 patients (63.41%) were allocated at the adult group (AoRRP, equal or more than 18 years). JoRRP patients needed, in average, a higher number of surgeries to control the disease than AoRRP patients (mean difference: 3.36). Also, JoRRP patients showed a higher Derkay score at each surgery (mean difference: 3.76). There was no significant difference in the number of surgeries when we compared patients infected with HPV-6 or HPV-11, neither in accordance to HPV-6 variants. Patients with HPV-11 presented a higher mean Derkay score at surgery than those with HPV-6 (mean difference: 4.39); when co-variated by age, we observed that this difference occurred only among JoRRP patients (mean difference: 6.15).

CONCLUSIONS

Age of onset of RRP has an important impact on number of surgeries to control disease. Patients with JoRRP and HPV-11 tend to present worse Derkay score at each surgery. HPV genotype among adults and HPV-6 variants had no impact on the outcome of the disease.

High prevalence of human papillomavirus and European variants of HPV 16 infecting concomitantly to cervix and oral cavity in HIV positive women

OBJECTIVE

Identify the prevalence of HPV infections in the uterine cervix and oral cavity and HPV16 variants in HIV+ women.

METHODS

A total of 174 HIV+ women attended an HIV+ specialized clinic in Mexico City. Cells were obtained from the oral cavity and cervix to extract DNA. Polymerase chain reaction (PCR) was used to amplify the HPV sequence with generic primers. We detected specific HPV types using the INNO-LiPA HPV Genotyping Extra II Kit (INNOGENETICS). The identification of variants was studied by sequencing the E6 gene with a Big Dye Terminator Kit and an Applied Biosystems 3500/3500xL genetic analyzer.

RESULTS

HPV infection was very high in the uterine cervix (168/174, 96.6%) and oral cavity (161/174, 92.5%). The prevalence of HPV concurrent infections in the cervix and oral cavity was 155/174 (89.1%). We found hrHPVs to be more prevalent than low-risk HPVs (lrHPVs) in the oral cavity (90.2% versus 45.4%) and that infections simultaneously affected the cervix (94.3% versus 36.2%) and oral cavity (85.1% versus 20.1%). Surprisingly, only European variants of HPV type 16 were found in the uterine cervix of women and the oral cavity of all tested samples (52 oral cavity samples and 52 uterine cervix samples).

CONCLUSIONS

The high prevalence of HPV, multiple infections and presence of the EP350G intravariant in both anatomical regions are strongly related to the persistence of the virus, which is fundamental for the development of cancer. Therefore, it is very important to control and monitor this high-risk population as well as implement programs for the early detection of HPV and vaccination.

Human Papillomavirus 58 E7 T20I/G63S Variant Isolated from an East Asian Population Possesses High Oncogenicity

Human papillomavirus (HPV) type 58 is the third most commonly detected HPV type in cervical cancer among Eastern Asians. Our previous international epidemiological studies revealed that HPV58 carrying an E7 natural variant, T20I/G63S (designated V1), was associated with a higher risk of cervical cancer. We recently showed that V1 possesses a greater ability to immortalize and transform primary cells, as well as degrading pRB more effectively, than the prototype and other common variants. In this study, we performed a series of phenotypic and molecular assays using physiologically relevant in vitro and in vivo models to compare the oncogenicity of V1 with that of the prototype and other common natural variants. Through activation of the AKT and K-Ras/extracellular signal-regulated kinase (ERK) signaling pathways, V1 consistently showed greater oncogenicity than the prototype and other variants, as demonstrated by increased cell proliferation, migration, and invasion, as well as induction of larger tumors in athymic nude mice. This study complements our previous epidemiological and molecular observations pinpointing the higher oncogenicity of V1 than that of the prototype and all other common variants. Since V1 is more commonly found in eastern Asia, our report provides insight into the design of HPV screening assays and selection of components for HPV vaccines in this region.IMPORTANCE Epidemiological studies have revealed that a wild-type variant of HPV58 carrying an E7 variation, T20I/G63S (V1), is associated with a higher risk of cervical cancer. We previously reported that this increased oncogenicity could be the result of the virus's greater ability to degrade pRB, thereby leading to an increased ability to grow in an anchorage-independent manner. In addition to this, this report further showed that this HPV variant induced activation of the AKT and K-Ras/ERK signaling pathways, thereby explaining its genuine oncogenicity in promoting cell proliferation, migration, invasion, and formation of tumors, all to a greater extent than the prototype HPV58 and other common variants.

Phylogenetic and functional analysis of sequence variation of human papillomavirus type 31 E6 and E7 oncoproteins

High-risk human papillomaviruses (HPV) are the causative agents of cervical and other anogenital cancers as well as a subset of head and neck cancers. The E6 and E7 oncoproteins of HPV contribute to oncogenesis by associating with the tumour suppressor protein p53 and pRb, respectively. For HPV types 16 and 18, intratypic sequence variation was shown to have biological and clinical significance. The functional significance of sequence variation among HPV 31 variants was studied less intensively. HPV 31 variants belonging to different variant lineages were found to have differences in persistence and in the ability to cause high grade cervical intraepithelial neoplasia. In the present study, we started to explore the functional effects of natural sequence variation of HPV 31 E6 and E7 oncoproteins. The E6 variants were tested for their effects on p53 protein stability and transcriptional activity, while the E7 variants were tested for their effects on pRb protein level and also on the transcriptional activity of E2F transcription factors. HPV 31 E7 variants displayed uniform effects on pRb stability and also on the activity of E2F transcription factors. HPV 31 E6 variants had remarkable differences in the ability to inhibit the trans-activation function of p53 but not in the ability to induce the in vivo degradation of p53. Our results indicate that natural sequence variation of the HPV 31 E6 protein may be involved in the observed differences in the oncogenic potential between HPV 31 variants.

Analysis of human papillomavirus 16 variants and risk for cervical cancer in Chinese population

HPV16 is the most carcinogenic HPV type, but only a minority of HPV16 infections progress to cancer. Intratype genetic variants of HPV16 have been suggested to confer differential carcinogenicity. To investigate risk implications of HPV16 variants among Chinese women, a case-control study was conducted with 298 cervical cancer patients and 85 controls (all HPV16-positive). HPV16 isolates were predominantly of the A variant lineage, and variants of A4 (previously named "Asian") sublineage were common. A4/Asian variants were significantly associated with increased risk of cervical cancer compared to A1-3 (OR=1.72, 95% CI=1.04-2.85). Furthermore, a meta-analysis including 703 cases and 323 controls from East Asia confirmed the association (OR=2.82, 95% CI=1.44-5.52). In conclusion, A4 variants appear to predict higher risk of cervical cancer among HPV16-positive women, which may provide clues to the genetic basis of differences in the carcinogenicity of HPV16 variants.

Changes in global gene expression profiles induced by HPV 16 E6 oncoprotein variants in cervical carcinoma C33-A cells

We analyzed the effects of the expression of HPV 16 E6 oncoprotein variants (AA-a, AA-c, E-A176/G350, E-C188/G350, E-G350), and the E-Prototype in global gene expression profiles in an in vitro model. E6 gene was cloned into an expression vector fused to GFP and was transfected in C33-A cells. Affymetrix GeneChip Human Transcriptome Array 2.0 platform was used to analyze the expression of over 245,000 coding transcripts. We found that HPV16 E6 variants altered the expression of 387 different genes in comparison with E-Prototype. The altered genes are involved in cellular processes related to the development of cervical carcinoma, such as adhesion, angiogenesis, apoptosis, differentiation, cell cycle, proliferation, transcription and protein translation. Our results show that polymorphic changes in HPV16 E6 natural variants are sufficient to alter the overall gene expression profile in C33-A cells, explaining in part the observed differences in oncogenic potential of HPV16 variants.

The human papillomavirus 16 European-T350G E6 variant can immortalize but not transform keratinocytes in the absence of E7

Human papillomavirus type 16 is commonly implicated in HPV-related cancers. However, only a small number of infected individuals progress to this stage. Epidemiological evidence demonstrated that oncogenic risk is population-specific and variations within the viral oncogene, E6, have been suggested to play a role in these findings. Of focus in this study is the European-T350G variant, which is characterized by an L>V amino acid substitution at residue 83 of the prototype E6 protein. To elucidate the functional effects of this polymorphism, we followed keratinocytes transduced with E-T350G E6 for over 60 passages and compared them to keratinocytes transduced, in parallel, with prototype or Asian-American (Q14H/L83V/H78Y) E6. We found that although E-T350G E6 immortalized transduced keratinocytes in the absence of E7, these cells were not fully transformed. We also found that E-T350G down-regulated E-cadherin compared to the other variants, providing a possible link between its population-based oncogenicity and host genetic variations.

Human papillomavirus types detected in skin warts and cancer differ in their transforming properties but commonly counteract UVB induced protective responses in human keratinocytes

In the present study, E6E7 and E6 proteins of human papillomaviruses (HPVs) associated with skin warts and cancer were compared for their transforming and carcinogenic abilities in primary human keratinocytes (PHKs). We show that E6E7 of cancer associated beta HPV types, notably 49 and 24, were able to extend the life span and enhance the clonogenic efficiency of PHKs when maintained in serum free/low calcium medium. Activities of the beta HPV E6E7 were lower than those of HPV16 E6E7. In contrast, E6 proteins from HPV types detected in skin warts or cancer, notably 10, 49 and 38, attenuated UVB induced protective responses in PHKs including cell death, proliferation arrest and accumulation of the proapoptotic proteins, p53, bax or bak. Together, this investigation revealed functional differences and commonalities between HPVs associated with skin warts and cancer, and allowed the identification of specific properties of beta HPVs supporting their involvement in skin carcinogenesis.

Intratypic variants of human papillomavirus type 16 and risk of cervical neoplasia in Taiwan

The associations between variants of human papillomavirus (HPV) 16 and risk of cervical neoplasia have been reported, but nucleotide variations of HPV 16 in Asian populations and their association with cervical neoplasia have not been evaluated extensively. During 1991-1992, 11,923 women from seven townships in Taiwan were enrolled. The HPV DNA in cervical cells was detected and genotyped using EasyChip HPV blot. Nucleotide variations in the long control region (LCR), E6, and E7 genes were determined using DNA sequencing for 170 HPV 16-positive cervical samples. The Asian variant was the most prevalent variant (81.8%) of HPV 16 in Taiwan, and was also associated with increased prevalence of histologically confirmed cervical intraepithelial neoplasia grade 3 or worse, showing an age-adjusted odds ratio (exact confidence limits) of 10.70 (1.62-451.05; P = 0.0049) compared to the HPV 16 European variant. Similar significant associations with cervical intraepithelial neoplasia grade 3 or worse were also observed for distinct nucleotide substitutions, including T178A/G, A647G, A7730C/G, T7781C, G7842A, and C24T/G. These results demonstrate that non-European variants (non-E) of HPV 16, predominantly Asian variants, are associated with increased risk for severe cervical neoplasia, compared with European variants. Molecular mechanisms accounting for varied cervical neoplasia risk among different HPV 16 variants warrant further investigation.

Characterization and whole genome analysis of human papillomavirus type 16 e1-1374^63nt variants

BACKGROUND

The variation of the most common Human papillomavirus (HPV) type found in cervical cancer, the HPV16, has been extensively investigated in almost all viral genes. The E1 gene variation, however, has been rarely studied. The main objective of the present investigation was to analyze the variability of the E6 and E1 genes, focusing on the recently identified E1-1374^63nt variant.

METHODOLOGY/PRINCIPAL FINDINGS

Variation within the E6 of 786 HPV16 positive cervical samples was analyzed using high-resolution melting, while the E1-1374^63nt duplication was assayed by PCR. Both techniques were supplemented with sequencing. The E1-1374^63nt duplication was linked with the E-G350 and the E-C109/G350 variants. In comparison to the referent HPV16, the E1-1374^63nt E-G350 variant was significantly associated with lower grade cervical lesions (p = 0.029), while the E1-1374^63nt E-C109/G350 variant was equally distributed between high and low grade lesions. The E1-1374^63nt variants were phylogenetically closest to E-G350 variant lineage (A2 sub-lineage based on full genome classification). The major differences between E1-1374^63nt variants were within the LCR and the E6 region. On the other hand, changes within the E1 region were the major differences from the A2 sub-lineage, which has been historically but inconclusively associated with high grade cervical disease. Thus, the shared variations cannot explain the particular association of the E1-1374^63nt variant with lower grade cervical lesions.

CONCLUSIONS/SIGNIFICANCE

The E1 region has been thus far considered to be well conserved among all HPVs and therefore uninteresting for variability studies. However, this study shows that the variations within the E1 region could possibly affect cervical disease, since the E1-1374^63nt E-G350 variant is significantly associated with lower grade cervical lesions, in comparison to the A1 and A2 sub-lineage variants. Furthermore, it appears that the silent variation 109T>C of the E-C109/G350 variant might have a significant role in the viral life cycle and warrants further study.

Whole genome sequencing and evolutionary analysis of human papillomavirus type 16 in central China

Human papillomavirus type 16 plays a critical role in the neoplastic transformation of cervical cancers. Molecular variants of HPV16 existing in different ethnic groups have shown substantial phenotypic differences in pathogenicity, immunogenicity and tumorigenicity. In this study, we sequenced the entire HPV16 genome of 76 isolates originated from Anyang, central China. Phylogenetic analysis of these sequences identified two major variants of HPV16 in the Anyang area, namely the European prototype (E(p)) and the European Asian type (E(As)). These two variants show a high degree of divergence between groups, and the E(p) comprised higher genetic diversity than the E(As). Analysis with two measurements of genetic diversity indicated that viral population size was relatively stable in this area in the past. Codon based likelihood models revealed strong statistical support for adaptive evolution acting on the E6 gene. Bayesian analysis identified several important amino acid positions that may be driving adaptive selection in the HPV 16 population, including R10G, D25E, L83V, and E113D in the E6 gene. We hypothesize that the positive selection at these codons might be a contributing factor responsible for the phenotypic differences in carcinogenesis and immunogenicity among cervical cancers in China based on the potential roles of these molecular variants reported in other studies.

Characterization of a cluster of oncogenic mutations in E6 of a human papillomavirus 83 variant isolated from a high-grade squamous intraepithelial lesion

We previously isolated human papillomavirus 83 (HPV83m) from a cervical smear. Sequence analysis of E6 and E7 proteins highlighted five mutations located in the second putative zinc-finger region of E6 (E6m), an important domain for protein-protein or protein-DNA interactions. Here, we show that E6m of HPV83m can trigger human primary cell proliferation and anchorage-independent growth properties, similarly to E6 of HPV16, a high-risk HPV (HR-HPV). Interestingly, we demonstrate that, in contrast to E6 of HPV16, E6m corrupts neither p53 stability nor telomerase activity, but acts as a specific modulator of the transcriptional machinery. By studying E6m reversion mutants, we confirmed the importance of the second zinc-finger domain in triggering the observed upregulation of cell growth and of the transcriptional machinery. Reversion of these mutations in E6m (to yield strain E6r) fully abolished the oncogenic potential of E6m, transforming the phenotype of E6 from a high-risk to a low-risk phenotype. Importantly, our data define the importance of a cluster of mutations in the second zinc finger of E6m in increasing the oncogenic potential of HPV83.

Rare human papillomavirus 16 E6 variants reveal significant oncogenic potential

The aim of this study was to determine whether low prevalence human papillomavirus (HPV) 16 E6 variants differ from high prevalence types in their functional abilities. We evaluated functions relevant to carcinogenesis for the rarely-detected European variants R8Q, R10G and R48W as compared to the commonly detected L83V. Human immortalized keratinocytes (NIKS) stably transduced with the E6 variants were used in most functional assays. Low and high prevalence E6 variants displayed similar abilities in abrogation of growth arrest and inhibition of p53 elevation induced by actinomycin D. Differences were detected in the abilities to dysregulate stratification and differentiation of NIKS in organotypic raft cultures, modulate detachment induced apoptosis (anoikis) and hyperactivate Wnt signaling. No distinctive phenotype could be assigned to include all rare variants. Like L83V, raft cultures derived from variants R10G and R48W similarly induced hyperplasia and aberrantly expressed keratin 5 in the suprabasal compartment with significantly lower expression of keratin 10. Unlike L83V, both variants, and particularly R48W, induced increased levels of anoikis upon suspension in semisolid medium. R8Q induced a unique phenotype characterized by thin organotypic raft cultures, low expression of keratin 10, and high expression of keratins 5 and 14 throughout all raft layers. Interestingly, in a reporter based assay R8Q exhibited a higher ability to augment TCF/β-catenin transcription. The data suggests that differences in E6 variant prevalence in cervical carcinoma may not be related to the carcinogenic potential of the E6 protein.

E6 molecular variants of human papillomavirus (HPV) type 16: an updated and unified criterion for clustering and nomenclature

Reports on taxonomic identification of E6/HPV 16 variants, don't have a worldwide, updated and unified criterion for clustering and nomenclature. Our aim was to update the existing criterion and propose a new one for clustering and nomenclature for E6/HPV 16 molecular variants based on the descriptive and comparative analyses of nucleotide sequences. A systematic search of the publications between 1991 and 2010 was carried out in PUBMED and manually. 240 E6/HPV 16 variants were identified. 157 were classified as European (E), 24 as Asian (As), 14 as Asian American (AA), 11 as North American 1 (NA 1), 19 as African 1 (Af 1) and 15 as African 2 (Af 2). Three classes were determined for the E, 3 each for the As, Af 2 and AA branches, 4 classes for the NA 1 and 6 for the Af 1 branch. This study reports our results and proposes an updated criterion for clustering and nomenclature that will be useful for E6 variant identification.

The immortalizing and transforming ability of two common human papillomavirus 16 E6 variants with different prevalences in cervical cancer

Persistent infection with high-risk human papillomaviruses (HPVs), especially type 16 has been undeniably linked to cervical cancer. The Asian-American (AA) variant of HPV16 is more common in the Americas than the prototype in cervical cancer. The different prevalence is based on three amino acid changes within the E6 protein denoted Q14H/H78Y/L83V. To investigate the mechanism(s) behind this observation, both E6 proteins, in the presence of E7, were evaluated for their ability to extend the life span of and transform primary human foreskin keratinocytes (PHFKs). Long-term cell culture studies resulted in death at passage 9 of vector-transduced PHFKs (negative control), but survival of both E6 PHFKs to passage 65 (and beyond). Compared with E6/E7 PHFKs, AA/E7 PHFKs were significantly faster dividing, developed larger cells in monolayer cultures, showed double the epithelial thickness and expressed cytokeratin 10 when grown as organotypic raft cultures. Telomerase activation and p53 inactivation, two hallmarks of immortalization, were not significantly different between the two populations. Both were resistant to anoikis at later passages, but only AA/E7 PHFKs acquired the capacity for in vitro transformation. Proteomic analysis revealed markedly different protein patterns between E6/E7 and AA/E7, particularly with respect to key cellular metabolic enzymes. Our results provide new insights into the reasons underlying the greater prevalence of the AA variant in cervical cancer as evidenced by characteristics associated with higher oncogenic potential.

The role of HPV type in Recurrent Respiratory Papillomatosis

OBJECTIVE

Human Papillomavirus (HPV) 6 and 11 are the aetiological agents responsible for Recurrent Respiratory Papillomatosis (RRP). There is general consensus that HPV11 results in more aggressive disease compared to HPV6.

METHOD

Pubmed was searched using the terms respiratory papillomatosis, HPV 6 and HPV11. Comparisons were made in the outcomes of HPV6 versus HPV11 positive RRP disease.

RESULTS

There are numerous sub-types or variants of both HPV6 and HPV11. These sub-types have different activities at least in-vitro. The numbers of different HPV types within RRP tissue may be more extensive than initially appeared. This depends specifically upon the HPV types tested for.

CONCLUSION

The clinical differences between HPV6 and HPV11 disease may not be accurately predictable as these viruses exist in numerous sub-types. Also, RRP tissue may contain more than one subtype or even be co-infected with other viruses that may influence outcome. In-vitro studies upon cell lines are a reasonable starting point for evaluation of these differences.

Upstream regulatory region alterations found in human papillomavirus type 16 (HPV-16) isolates from cervical carcinomas increase transcription, ori function, and HPV immortalization capacity in culture

Human papillomavirus (HPV) DNAs isolated from cervical and head and neck carcinomas frequently contain nucleotide sequence alterations in the viral upstream regulatory region (URR). Our study has addressed the role such sequence changes may play in the efficiency of establishing HPV persistence and altered keratinocyte growth. Genomic mapping of integrated HPV type 16 (HPV-16) genomes from 32 cervical cancers revealed that the viral E6 and E7 oncogenes, as well as the L1 region/URR, were intact in all of them. The URR sequences from integrated and unintegrated viral DNA were found to harbor distinct sets of nucleotide substitutions. A subset of the altered URRs increased the potential of HPV-16 to establish persistent, cell growth-altering viral-genome replication in the cell. This aggressive phenotype in culture was not solely due to increased viral early gene transcription, but also to augmented initial amplification of the viral genome. As revealed in a novel ori-dependent HPV-16 plasmid amplification assay, the altered motifs that led to increased viral transcription from the intact genome also greatly augmented HPV-16 ori function. The nucleotide sequence changes correlate with those previously described in the distinct geographical North American type 1 and Asian-American variants that are associated with more aggressive disease in epidemiologic studies and encompass, but are not limited to, alterations in previously characterized sites for the negative regulatory protein YY1. Our results thus provide evidence that nucleotide alterations in HPV regulatory sequences could serve as potential prognostic markers of HPV-associated carcinogenesis.

HPV variants and HLA polymorphisms: the role of variability on the risk of cervical cancer

Human papillomavirus (HPV) infection is linked to the development of cervical cancer, and several cofactors contribute to the risk of disease. Research on the intratypic variability of HPVs has defined variants that are associated with persistent infections and are potentially more oncogenic, translating to a higher risk of malignant disease. The genetic variability of the host also plays a role in the risk of cervical cancer, especially genes controlling the immune response, such as HLA class I and II. These highly polymorphic genes are important risk determinants of HPV persistence and disease progression. The interaction between host and viral factors is complex and needs to be further investigated, paving the way to better define the patients at the highest risk of developing malignant diseases linked to HPV infection.

Identification of a novel human papillomavirus type 16 E1 gene variant with potentially reduced oncogenicity

The human papillomavirus (HPV) 16 genome has been studied extensively, although no study has focused on the E1 gene that is implicated in viral DNA replication. After analyzing the E1 region of HPV 16 genomes in 429 cervical samples, 11.2% were found to contain a 63 nucleotides duplication in this region. Sequence analysis of the E6 and the E7 regions has shown that all samples containing this duplication were related to E6-G350 variant of the HPV 16 (Chi square test, P = 0.0012). A comparison of cervical lesion severity of the examinees having regular or variant E1 genes has shown that the variant group had a significantly (Fischer's exact test, P = 0.0401) lower percentage of high grade disease cases, suggesting that this particular duplication might reduce the oncogenic potential of HPV 16, and also might clarify the differences of E6-G350 variant oncogenicity observed in European populations. Albeit, a decreased incidence of high grade cervical lesions can be linked to the prevalence of multiple HPV infection, the additional decrease of those cases with the variant E1 gene versus those without (10.5% and 18.6%, respectively) can only be ascribed to the effect of this particular HPV variant. Further research is needed to clarify the biology of these HPV 16 E1 variants.

Human papillomavirus 16 E6 variants differ in their dysregulation of human keratinocyte differentiation and apoptosis

L83V-related variants of human papillomavirus (HPV) 16 E6, exemplified by the Asian-American variant Q14H/H78Y/L83V, were shown to be more prevalent than E6 prototype in progressing lesions and cervical cancer. We evaluated functions relevant to carcinogenesis for the E6 variants L83V, R10/L83V and Q14H/H78Y/L83V as well as the prototype in a model of human normal immortalized keratinocytes (NIKS). All E6 expressing NIKS equally abrogated growth arrest and DNA damage responses. Organotypic cultures derived from these keratinocytes demonstrated hyperplasia and aberrantly expressed keratin 5 in the suprabasal compartment. In contrast, differentiation and induction of apoptosis varied. The E6 variant rafts expressed keratin 10 in nearly all suprabasal cells while the prototype raft showed keratin 10 staining in a subset of suprabasal cells only. In addition, E6 variant NIKS expressing R10G/L83V and Q14H/H78Y/L83V were more prone to undergo cell-detachment-induced apoptosis (anoikis) than NIKS expressing E6 prototype. The combined differentiation and apoptosis pattern of high-risk E6 variants, especially of Q14H/H78Y/L83V, may reflect a phenotype beneficial to carcinogenesis and viral life cycle.

Cervical cancer screening: from molecular basis to diagnostic practice, going through new technologies

In the era of Human Papillomavirus (HPV) vaccination, a lot of misunderstanding still exists among healthcare professionals and patients regarding HPV infection. The purpose of this review is to synthesize the clinical molecular mechanisms that contribute to HPV-mediated cervical carcinogenesis, as well as to appraise the current status of new biomarkers and technologies in terms of available data on clinical applications and future promises.

Interaction between polymorphisms of the human leukocyte antigen and HPV-16 variants on the risk of invasive cervical cancer

Background

Persistent infection with oncogenic types of human papillomavirus (HPV) is the major risk factor for invasive cervical cancer (ICC), and non-European variants of HPV-16 are associated with an increased risk of persistence and ICC. HLA class II polymorphisms are also associated with genetic susceptibility to ICC. Our aim is to verify if these associations are influenced by HPV-16 variability.

Methods

We characterized HPV-16 variants by PCR in 107 ICC cases, which were typed for HLA-DQA1, DRB1 and DQB1 genes and compared to 257 controls. We measured the magnitude of associations by logistic regression analysis.

Results

European (E), Asian-American (AA) and African (Af) variants were identified. Here we show that inverse association between DQB1*05 (adjusted odds ratio [OR] = 0.66; 95% confidence interval [CI]: 0.39–1.12]) and HPV-16 positive ICC in our previous report was mostly attributable to AA variant carriers (OR = 0.27; 95%CI: 0.10–0.75). We observed similar proportions of HLA DRB1*1302 carriers in E-P positive cases and controls, but interestingly, this allele was not found in AA cases (p = 0.03, Fisher exact test). A positive association with DRB1*15 was observed in both groups of women harboring either E (OR = 2.99; 95% CI: 1.13–7.86) or AA variants (OR = 2.34; 95% CI: 1.00–5.46). There was an inverse association between DRB1*04 and ICC among women with HPV-16 carrying the 350T [83L] single nucleotide polymorphism in the E6 gene (OR = 0.27; 95% CI: 0.08–0.96). An inverse association between DQB1*05 and cases carrying 350G (83V) variants was also found (OR = 0.37; 95% CI: 0.15–0.89).

Conclusion

Our results suggest that the association between HLA polymorphism and risk of ICC might be influenced by the distribution of HPV-16 variants.