Analysis of human papillomavirus type-16 variants in Italian women with cervical intraepithelial neoplasia and cervical cancer

Human papillomavirus type 16 (HPV-16) classes (E, AA, As, Af1, Af2) and their variants have different geographic distribution and different degrees of association with cervical lesions. This study was designed to examine HPV-16 variants among Italian women and their prevalence in case patients (affected by invasive cervical carcinoma or cervical intraepithelial neoplasia grade 2-3 and cervical intraepithelial neoplasia grade 1), versus control subjects with normal cervical epithelium (controls). A total of 90 HPV-16 positive cervical samples from women of Italian Caucasian descent have been tested, including 36 invasive cervical carcinomas, 21 with cervical intraepithelial neoplasias grade 2-3, 17 with cervical intraepithelial neoplasia grade 1 and 16 controls. HPV-16 was detected with an E6/E7 gene-specific polymerase chain reaction, and variant HPV-16 classes and subclasses were identified by direct nucleotide sequencing of the region coding for the E6 and the E7 oncoproteins, the MY09/11-amplified highly conserved L1 region, and the long control region (LCR). Among the 90 HPV-16 samples, nine viral variants have been identified belonging to the European (Ep-T350 and E-G350) and non-European (AA and Af-1) branches. The E-G350 is the prevalent variant in all analyzed different disease stages being present in 55.5% of ICC, 52.4% of cervical intraepithelial neoplasias 2-3, 47.1% of cervical intraepithelial neoplasia grade 1, and 50.0% of control samples. The non-European variants AA and Af1, rarely detected in control samples, represent 33.3% of all HPV-16 infections in invasive cervical carcinoma (with a peak of 19.4% and 13.9%, respectively), showing a statistically significant increase in frequency in more advanced lesions (chi(2) trend = 7.2; P < 0.05). The prevalence of HPV-16 Ep-T350, however, is higher in controls (43.7%) and in of cervical intraepithelial neoplasia grade 1 (41.2%) than in cervical intraepithelial neoplasia grade 2-3 (28.6%) and in invasive cervical carcinoma (11.1%) cases strongly suggesting lack of progression for pre-neoplastic lesions associated with such variant. The increased frequency of non-European variants in invasive lesions suggests that they are more oncogenic than European variants. This could have implications for future diagnostic and therapeutic strategies.     

Development of a sensitive and specific nanoparticle-assisted PCR assay for detecting HPV-16 and HPV-18 DNA

Carcinoma precursor lesion caused by persistent infection of human papillomavirus (HPV) types 16 and 18 is known as a principal inducer of cervical cancer. Therefore, rapid and effective detection of HPV-16 and HPV-18 infection at early stage is an important strategy for preventing such disease. In this study, a novel duplex nanoparticle-assisted polymerase chain reaction (nanoPCR) assay was developed to detect both of the two genotypes simultaneously. Two pairs of primers for nanoPCR were designed based on the conserved region within the early 6 (E6) gene of HPV-16 and HPV-18, respectively. After optimizing reaction conditions, the nanoPCR assay displayed 10-fold more sensitive than that of conventional PCR and showed high specificity. The detection limit of nanoPCR was 1.7 × 10¹ copies/μL for HPV-16, 1.2 × 10² copies/μL for HPV-18, and no cross-reaction was detected after using other viruses or HPV subtypes as templates. Of 209 clinical samples collected from patients, as also confirmed by sequencing, the nanoPCR method gave consistent results with conventional PCR assay: 7 positives for HPV-16, 4 positives for HPV-18, and no co-infection. Here is the first report to introduce a reproducible nanoPCR assay for detecting HPV DNA with high sensitivity and specificity, which may point out a useful diagnostic tool for potential clinical application.     

A non-radioactive PCR-SSCP analysis allows to distinguish between HPV 16 European and Asian-American variants in squamous cell carcinomas of the uterine cervix in Colombia

Human Papillomavirus type 16 (HPV 16) DNA is regularly found in around 50% of all cervical carcinomas. Variants of this type have been found associated with different risks for cervical cancer development. Presence of HPV 16 variants in Colombia has not been previously reported. The aims of this study were to assess the feasibility of non-radioactive PCR-SSCP (polymerase chain reaction single-strand conformation polymorphism) analysis for determination of variability of ORF of E6, variability in the enhancer sequence of the LCR, and for establishment of the distribution of HPV 16 variants in invasive squamous cell carcinoma of the uterine cervix in Colombian women. Biopsies from 59 patients at the Instituto Nacional de Cancerología (INC) in Bogotá (Colombia) were collected. HPV detection was performed using universal primers. HPV 16 variants were detected by non-radioactive single-stranded conformational polymorphism (SSCP) analysis and direct sequencing. HPV 16 was detected in 57.6% of the tumors. The European branch was identified in 88.2% of the samples with the E-G350 class being the most prevalent variant (41.1%). The Asian-American branch was identified in 8.8% of the samples. Within this group it was possible to distinguish between c and a classes. It was not possible to determine the branch in 2.9% of the cases. A nucleotide transition (G to A) at position 7521 was the most prevalent variation (80%) found in the enhancer sequence of the LCR region. Conclusion: A non-radioactive PCR-SSCP analysis allowed us to distinguish between European and Asian-American branches of HPV 16, and to distinguish among classes in squamous cell carcinomas of the uterine cervix in Colombia. This method is an excellent alternative that can be used as a screening tool for identification of HPV 16 variants.     

Correlation of laryngeal squamous cell carcinoma and infections with either HHV-8 or HPV-16/18

Each year more than 159,000 new cases of laryngeal cancer are diagnosed globally, and more than 9000 patients die due to this malignancy. Viral infections are a known risk factor for this malignancy. Thus, this study aimed to evaluate the role of HPV-16/18 and HHV-8 infection in patients with laryngeal cancer.     

Phenotypic effects of HPV-16 E2 protein expression in human keratinocytes

Expression of the HPV E2 open reading frame in cervical cancer cells has been shown to affect the expression of both viral and cellular genes. We have examined the phenotypic effects of the expression of human papillomavirus 16 E2 open reading frame in the human keratinocyte cell line HaCaT. Increased levels of apoptotic cell death were seen within 24 h of the transfection of HPV-16 E2 expression constructs. However, in those cells which survived selection and retained the intact E2 ORF, long-term stable expression of E2, as detected by RT-PCR, produced cells which developed phenotypes typical of terminally differentiated cells. These included characteristic morphological changes and expression of involucrin, filaggrin and senescence markers. This provides the first evidence of a role for E2 in stimulation of the normal epithelial differentiation programme, which would promote the progression of the HPV life cycle.     

Worldwide genomic diversity of the human papillomaviruses-53, 56, and 66, a group of high-risk HPVs unrelated to HPV-16 and HPV-18

Among more than 200 human papillomavirus (HPV) types presumed to exist, 18 "high-risk" HPV types are frequently found in anogenital cancer. The best studied types are HPV-16 and 18, which are only distantly related to one another and form two separate phylogenetic branches, each including six closely related types. HPV-30, 53, 56, and 66 form a third phylogenetic branch unrelated to HPV-16 and 18. Worldwide comparison of HPV-16 and 18 isolates revealed a distribution of variant genomes that correlated with the geographic origin and the ethnicity of the infected cohort and led to the concept of unique African, European, Asian, and Native American HPV-16 and 18 variants. Here, we address the question whether similar phylogenies are found for HPV-53, 56, and 66 by determining the sequence of the long control regions (LCR) of these HPVs in samples from Europe, Asia, and Africa, and from immigrant societies in North and South America. Phylogenetic trees calculated from point mutations and a few insertions/deletions affecting 2-4.2% of the nucleotide sequences were distinct for each of the three HPVs and divergent from HPV-16 and 18. In contrast to the "star-phylogenies" formed by HPV-16 and 18 variants, 44 HPV-53 isolates represented nine variants, which formed two deep dichotomic branches reminiscent of the beginning split into two new taxa, as recently observed for subtypes of HPV-44 and 68. A total of 66 HPV-56 isolates represented 17 variants, which formed three branches preferentially containing European, Asian, and African variants. Variants of a fourth branch, deeply separated from the other three, were characterized by a 25 bp insertion and created a dichotomy rather than star-like phylogeny. As it contained isolates from cohorts in all continents, it may have evolved before the spread of humans into all continents. 18 of 31 HPV-66 isolates represented the prototype clone, which was found in all parts of the world, while the remaining 13 clones formed 11 branches without any geographic association. Our findings confirm the notion of a quantitatively limited genomic diversity of each HPV type with some correlation to the geographic origin of the sample. In addition, we observed in some variants of these three HPV types mutations that affect the amino acid sequence of the E6 oncoproteins and the L1 capsid protein, supporting the possibility of immunogenic and oncogenic diversity between variants of any HPV type.     

Identification of a 17-nucleotide splicing enhancer in HPV-16 L1 that counteracts the effect of multiple hnRNP A1-binding splicing silencers

Human papillomavirus type 16 (HPV-16) infections can in rare cases persist and cause lesions that may progress to cervical cancer. Cells in the lesions are not permissive for virus production, nor are cervical cancer cells. The intracellular environment is such that it prevents production of the highly immunogenic, viral structural proteins L1 and L2. One may speculate that inhibition of L1 and L2 expression is a prerequisite for persistence and cancer progression. We have therefore investigated how expression of HPV-16 L1 is regulated. We found that the only splice site in the HPV-16 late region, which is used to produce L1 mRNAs, is under control of a splicing enhancer located in the 17 nucleotides immediately downstream of the splice site. However, the function of this enhancer in cervical cancer cells is largely overshadowed by multiple splicing silencers in the late region which bind to hnRNP A1. High levels of hnRNP A1 therefore inhibit HPV-16 L1 expression. Immunohistological analysis of cervical epithelia revealed that hnRNP A1 is expressed primarily in the lower layers of the epithelium. hnRNP A1 is undetectable in terminally differentiated cells that can express HPV-16 late genes, which supports the conclusion that high levels of hnRNP A1 inhibit HPV-16 L1 expression.     

HPV-16 L1 genes with inactivated negative RNA elements induce potent immune responses

Introduction of point mutations in the 5' end of the human papillomavirus type 16 (HPV-16) L1 gene specifically inactivates negative regulatory RNA processing elements. DNA vaccination of C57Bl/6 mice with the mutated L1 gene resulted in improved immunogenicity for both neutralizing antibodies as well as for broad cellular immune responses. Previous reports on the activation of L1 by codon optimization may be explained by inactivation of the regulatory RNA elements. The modified HPV-16 L1 DNA that induced anti-HPV-16 immunity may be seen as a complementary approach to protein subunit immunization against papillomavirus.     

Oncogenic potential diverge among human papillomavirus type 16 natural variants

We compared E6/E7 protein properties of three different HPV-16 variants: AA, E-P and E-350G. Primary human foreskin keratinocytes (PHFK) were transduced with HPV-16 E6 and E7 and evaluated for proliferation and ability to grow in soft agar. E-P infected keratinocytes presented the lowest efficiency in colony formation. AA and E-350G keratinocytes attained higher capacity for in vitro transformation. We observed similar degradation of TP53 among HPV-16 variants. Furthermore, we accessed the expression profile in early (p5) and late passage (p30) transduced cells of 84 genes commonly involved in carcinogenesis. Most differences could be attributed to HPV-16 E6/E7 expression. In particular, we detected different expression of ITGA2 and CHEK2 in keratinocytes infected with AA and AA/E-350G late passage cells, respectively, and higher expression of MAP2K1 in E-350G transduced keratinocytes. Our results indicate differences among HPV-16 variants that could explain, at least in part, differences in oncogenic potential attributed to these variants.     

Subcellular localization of the human papillomavirus 16 E7 oncoprotein in CaSki cells and its detection in cervical adenocarcinoma and adenocarcinoma in situ

E7 is the major oncoprotein of high-risk human papillomaviruses (HPV) which causes cervical cancer. To date E7 oncoproteins have not been investigated in cervical adenocarcinoma. In this study we generated a rabbit monoclonal anti-HPV-16 E7 antibody, RabMab42-3, which recognizes a conformational epitope in the E7 carboxy-terminal zinc-finger resulting in a strong increase in the sensitivity for the detection of cell-associated HPV-16 E7 protein relative to conventional polyclonal anti-HPV-16 E7 antibodies. Using RabMab42-3, we show that the subcellular localization of endogenous HPV-16 E7 oncoprotein varies during the cell cycle in cervical cancer cells. Moreover, we demonstrate for the first time that the HPV-16 E7 oncoprotein is abundantly expressed in cervical adenocarcinoma in situ and adenocarcinoma, suggesting an important role of HPV-16 E7 for the development of these tumors. Our findings suggest that the HPV-16 E7 oncoprotein could be a useful marker for the detection of cervical adenocarcinoma and their precursors.     

HPV-16 E5 down-regulates expression of surface HLA class I and reduces recognition by CD8 T cells

HPV-16 is the major causes of cervical cancer. Persistence of infection is a necessary event for progression of the infection to cancer. Among other factors, virus persistence is due the viral proteins fighting the immune response. HPV-16 E5 down-regulates MHC/HLA class I, which is much reduced on the cell surface and accumulates in the Golgi apparatus in cells expressing E5. This effect is observed also in W12 cells, which mimic early cervical intraepithelial progression to cervical cancer. The functional effect of MHC I down-regulation on human CD8 T cells is not known, because of the need for HLA-matched, HPV-specific T cells that recognise E5 expressing-cells. Here we employ a heterologous cell/MHC I system which uses mouse cells expressing both E5 and HLA-A2, and A2-restricted CTLs; we show that the E5-induced reduction of HLA-A2 has a functional impact by reducing recognition of E5 expressing cells by HPV specific CD8+ T cells.     

A pilot study on the distribution of human papillomavirus genotypes and HPV-16 variants in cervical neoplastic lesions from Ecuadorian women

Human papillomaviruses (HPVs) are the cause of cervical intraepithelial neoplasia and invasive carcinomas of the uterine cervix. The distribution of specific HPV genotypes varies greatly across populations and HPV surveys have been performed in different geographical regions in order to apply appropriate vaccine strategies. The aim of this study was to determine the spectrum of HPV genotypes and HPV-16 variants among women with cervical lesions living in Ecuador. A total of 71 cases have been analyzed, including 32 chronic cervicitis, 29 cervical intraepithelial neoplasia grade 1, and 10 cervical intraepithelial neoplasia grade 2-3. HPV sequences were detected by broad spectrum consensus-primer-pairs MY09/MY11 and GP5+/GP6+-based polymerase chain reaction and characterized by nucleotide sequence analysis. Overall, 31 (43.7%) cases were HPV positive with prevalence rates of 37.5%, 44.8%, and 60% in patients with chronic cervicitis, cervical intraepithelial neoplasia grade 1 and cervical intraepithelial neoplasia grade 2-3, respectively. Among the positive cases, the most common genotypes were HPV 16 (64.5%) and HPV 81 (29%) followed by HPV 31, 53, 56, and 58, in descending order of prevalence. Seventeen (85%) HPV-16 isolates were classified as European and three (15%) as African-1 variant on the basis of nucleotide signature present within the MY09/MY11 L1 sequence. The results suggest that HPV 16 has a very high prevalence among women with cervical lesions in Ecuador; therefore, an effective HPV-16 based vaccine should prevent the development of cervical cancer in a large proportion of Ecuadorian women.     

新疆维吾尔族妇女宫颈癌组织中人乳头状瘤病毒16型上游调控区DNA多态性分析

目的 探讨新疆南部地区维吾尔族妇女官颈癌组织中人乳头状瘤病毒16型（human papillomavirus16，HPV-16）上游调控区（upstream regulatory region，URR）的变异及其与新疆维吾尔族妇女官颈癌发生的关系。方法 从19份中国新疆南部地区维吾尔族妇女官颈癌活检组织标本中提取DNA，以此DNA为模板，PCR扩增HPV-16 URR DNA片段，PCR产物直接测序或克隆后测序，分析新疆维吾尔族妇女官颈癌组织HPV-16URR DNA多态性。结果 PCR检测结果显示宫颈癌组织中HPV-16 URR阳性率为89．47％（17／19）；测序和序列分析表明，与HPV-16原型比较，HPV-16URR核苷酸多处发生变异，URR在核苷酸水平上形成11种突变模式（XJU-1～XJU-11），XJU-1和XJU-4突变模式各占23．53％（4／17），其余各突变模式均占5．88％（1／17），各模式与HPV-16URR原型比较，同源性在98．50％～99．68％之间。在各位点的突变中，7192位（G→T）、7520位（G→A）的突变（100％，17／17）在新疆地区趋于恒定，该两处突变在亚裔美洲型（从）中普遍存在，与病毒感染及官颈癌发生相关；7729位（A→C）、7843位（A→G）、7792位（C→T）的突变可显著提高启动子的转录活性；其余突变尚未见报道，部分突变为新疆地区分离的HPV-16 URR所特有。结论 中国新疆南部HPV-16 URR基因发生变异，HPV-16 URR的突变与HPV-16的系统发生以及新疆维吾尔族妇女高发宫颈癌存在一定关系。     

The human papillomavirus type 16 E7 oncoprotein targets Myc-interacting zinc-finger protein-1

We demonstrate that HPV-16 E7 forms a complex with Miz-1. UV-induced expression of the CDK-inhibitor p21^Cip1 and subsequent cell cycle arrest depends upon endogenous Miz-1 in HPV-negative C33A cervical cancer cells containing mutated p53. Transient expression of E7 in C33A inhibits UV-induced expression of p21^Cip1 and overcomes Miz-1-induced G1-phase arrest. The C-terminal E7Δ79LEDLL83-mutant with reduced Miz-1-binding capacity was impaired in its capability to repress p21^Cip1 expression; whereas the pRB-binding-deficient E7C24G-mutant inhibited p21^Cip1 expression similar to wild-type E7. Using ChIP, we demonstrate that endogenous E7 is bound to the endogenous p21^Cip1 core-promoter in CaSki cells and RNAi-mediated knock down of Miz-1 abrogates E7-binding to the p21^Cip1 promoter. Co-expression of E7 with Miz-1 inhibited Miz-1-induced p21^Cip1 expression from the minimal-promoter via Miz-1 DNA-binding sites. Co-expression of E7Δ79LEDLL83 did not inhibit Miz-1-induced p21^Cip1 expression. E7C24G retained E7-wild-type capability to inhibit Miz-1-dependent transactivation. These findings suggest that HPV-16 E7 can repress Miz-1-induced p21^Cip1 gene expression.     

新疆南部地区维吾尔族妇女宫颈癌组织中HPV-16型L2基因多态性分析

目的探讨新疆南部地区维吾尔族妇女宫颈癌组织中人乳头瘤病毒16型(humanpapillomavirus16,HPV16)L2基因的变异,并预测L2蛋白的功能变化。方法从19份中国新疆南部地区维吾尔族妇女宫颈癌活检组织标本中提取DNA,以此DNA为模板,PCR扩增HPV16L2全长基因,PCR产物直接测序或克隆后测序,分析新疆维吾尔族妇女宫颈癌组织HPV16L2基因多态性及HPV16L2蛋白功能的变化。结果PCR检测结果显示宫颈癌组织中HPV16L2阳性率为84.21%(1619);测序和序列分析表明L2基因核苷酸多处发生变异,并引起编码氨基酸的变异;L2基因在核苷酸水平上形成7种突变模式(XJL21～XJL27),各模式与HPV16原型比较,同源性在99.37%～99.79%之间;在氨基酸水平上形成5种突变模式,其中XJL1123突变模式占66.67%(812),是突变的主流模式,各模式与HPV16原型比较,同源性在98.31%～99.58%之间;以上突变引起HPV16L2蛋白疏水性和抗原性的改变,继而改变了L1蛋白的结构及功能。结论中国新疆南部地区维吾尔族妇女宫颈癌组织中HPV16L2基因发生多位点变异,并形成多种突变模式和突变主流模式;这些突变引起HPV16L2蛋白疏水性和抗原性的改变,提示HPV16L2基因突变可能与HPV16的系统发生以及病毒逃避机体免疫识别有关。