Human pathogenic papillomavirus types: an update

HPV infections in retinoblastoma: a systematic review

BACKGROUND

Retinoblastoma is the most common primary intraocular malignancy in children less than 4 years. Retinoblastoma (RB) contains about 3%-5% of all childhood cancers. Recent studies demonstrated that interacting between RB tumor suppressor and oncoproteins of DNA tumor viruses such as human papillomavirus (HPV). The objective of the current systematic review study was to present conducted studies in the field of HPV infection and its possible role in retinoblastoma.

METHODS

For this systematic review, all relevant original research studies were assessed by searching in electronic databases include PubMed, Embase, Scopus, Google Scholar, and Web of Science by using relevant keywords. The study was designed based on the PRISMA criteria. All publications with English literature and original researches are considered for screening.

RESULTS

Conducted search results lead to 4070 studies. The title and abstract screening lead to 11 studies. Data extraction was performed on 8 included studies. The prevalence of the HPV was ranged from 0 to 69%, and HPV genotype 16 and 18 were the most detected types. The most used method for the detection of the viruses was PCR, and the most assessed sample was formalin-fixed, paraffin-embedded tissue blocks.

CONCLUSION

The association between HPV and retinoblastoma is still inconsistent. The prevalence of the HPV in RB was ranged from 0 to 69%, which indicates a wide range and highlights the importance of further investigation for more accurate statistical of HPV prevalence in RB. Thus, further worldwide studies of larger sample sizes of cohorts should be investigated to clarify this uncertainty.

Human Papillomaviruses; Epithelial Tropisms, and the Development of Neoplasia

Papillomaviruses have evolved over many millions of years to propagate themselves at specific epithelial niches in a range of different host species. This has led to the great diversity of papillomaviruses that now exist, and to the appearance of distinct strategies for epithelial persistence. Many papillomaviruses minimise the risk of immune clearance by causing chronic asymptomatic infections, accompanied by long-term virion-production with only limited viral gene expression. Such lesions are typical of those caused by Beta HPV types in the general population, with viral activity being suppressed by host immunity. A second strategy requires the evolution of sophisticated immune evasion mechanisms, and allows some HPV types to cause prominent and persistent papillomas, even in immune competent individuals. Some Alphapapillomavirus types have evolved this strategy, including those that cause genital warts in young adults or common warts in children. These strategies reflect broad differences in virus protein function as well as differences in patterns of viral gene expression, with genotype-specific associations underlying the recent introduction of DNA testing, and also the introduction of vaccines to protect against cervical cancer. Interestingly, it appears that cellular environment and the site of infection affect viral pathogenicity by modulating viral gene expression. With the high-risk HPV gene products, changes in E6 and E7 expression are thought to account for the development of neoplasias at the endocervix, the anal and cervical transformation zones, and the tonsilar crypts and other oropharyngeal sites. A detailed analysis of site-specific patterns of gene expression and gene function is now prompted.

Human Papillomavirus Genotypes and thep53Codon 72 Polymorphism in Cervical Cancer of Northeastern Thailand

Human papillomavirus (HPV) infection including sub-strain identification was studied in patients with squamous cell cervical cancer (SCCA) in Northeastern Thailand. Subjects were 90 cases of SCCA and 100 healthy controls. Prevalence of high-risk group of HPV infection in the controls and the SCCA patients were 13.0% and 86.7%, respectively. The HPV infection significantly increased the risk for cervical cancer 43.5-fold (95% confidential interval: 17.5-110.6; P <0.00001). Among HPV carrier patients with SCCA (n = 78), HPV-16 was also prominent (70.5%) followed by HPV-18 (23.1%). There was no statistical difference in the subtype distribution between the SCCA and the control groups. There was no significant association between genotype distribution of the p53 codon 72 polymorphism and HPV infection. HPV infection was confirmed as a critical risk factor for cervical cancer development in Northeast Thailand. Since polymorphism of the p53 itself as well as in combination with HPV infection may not be a genetic risk for cervical cancer, much attention should be paid to other risk factors such as sexual behavior and smoking.

p63 is necessary for the activation of human papillomavirus late viral functions upon epithelial differentiation

The late phase of the human papillomavirus (HPV) life cycle is linked to epithelial differentiation, and we investigated the factors that regulate this process. One potential regulator is p63, a member of the p53 family of proteins, which modulates epithelial development, as well as proliferation capability, in stem cells. In this study, we examined the role of p63 in the HPV life cycle using a lentiviral knockdown system for p63. In epithelial cells, the ΔN truncated isoforms of p63 predominate, while the full-length TA isoforms are present at very low levels. Upon the differentiation of normal keratinocytes, p63 levels rapidly decreased while higher levels were retained in HPV-positive cells. Our studies indicate that reducing p63 levels in differentiated HPV-positive cells resulted in the loss of viral genome amplification and late gene expression. p63 regulates the expression of cell cycle regulators, and we determined that cyclin A, cyclin B1, cdk1, and cdc25c were reduced in p63-deficient, HPV-positive keratinocytes, which suggests a possible mechanism of action. In addition, activation of the DNA repair pathway is necessary for genome amplification, and the expression of two members, BRCA2 and RAD51, was altered in the absence of p63 in HPV-positive cells. Our studies indicate that p63 is necessary for the activation of differentiation-dependent HPV late viral functions and provide insights into relevant cellular targets.

Regulation of nucleocytoplasmic trafficking of viral proteins: an integral role in pathogenesis?

Signal-dependent targeting of proteins into and out of the nucleus is mediated by members of the importin (IMP) family of transport receptors, which recognise targeting signals within a cargo protein and mediate passage through the nuclear envelope-embedded nuclear pore complexes. Regulation of this process is paramount to processes such as cell division and differentiation, but is also critically important for viral replication and pathogenesis; phosphorylation appears to play a major role in regulating viral protein nucleocytoplasmic trafficking, along with other posttranslational modifications. This review focuses on viral proteins that utilise the host cell IMP machinery in order to traffic into/out of the nucleus, and in particular those where trafficking is critical to viral replication and/or pathogenesis, such as simian virus SV40 large tumour antigen (T-ag), human papilloma virus E1 protein, human cytomegalovirus processivity factor ppUL44, and various gene products from RNA viruses such as Rabies. Understanding of the mechanisms regulating viral protein nucleocytoplasmic trafficking is paramount to the future development of urgently needed specific and effective anti-viral therapeutics. This article was originally intended for the special issue "Regulation of Signaling and Cellular Fate through Modulation of Nuclear Protein Import". The Publisher apologizes for any inconvenience caused.

Classification of papillomaviruses (PVs) based on 189 PV types and proposal of taxonomic amendments

We present an expansion of the classification of the family Papillomaviridae, which now contains 29 genera formed by 189 papillomavirus (PV) types isolated from humans (120 types), non-human mammals, birds and reptiles (64, 3 and 2 types, respectively). To accommodate the number of PV genera exceeding the Greek alphabet, the prefix "dyo" is used, continuing after the Omega-PVs with Dyodelta-PVs. The current set of human PVs is contained within five genera, whereas mammalian, avian and reptile PVs are contained within 20, 3 and 1 genera, respectively. We propose standardizations to the names of a number of animal PVs. As prerequisite for a coherent nomenclature of animal PVs, we propose founding a reference center for animal PVs. We discuss that based on emerging species concepts derived from genome sequences, PV types could be promoted to the taxonomic level of species, but we do not recommend implementing this change at the current time.

Role of human papillomavirus and its detection in potentially malignant and malignant head and neck lesions: updated review

Head and neck malignancies are characterized by a multiphasic and multifactorial etiopathogenesis. Tobacco and alcohol consumption are the most common risk factors for head and neck malignancy. Other factors, including DNA viruses, especially human papilloma virus (HPV), may also play a role in the initiation or development of these lesions. The pathways of HPV transmission in the head and neck mucosal lesions include oral-genital contact, more than one sexual partner and perinatal transmission of HPV to the neonatal child. The increase in prevalence of HPV infection in these lesions may be due to wider acceptance of oral sex among teenagers and adults as this is perceived to be a form of safe sex. The prevalence of HPV in benign lesions as well as malignancies has been assessed by many techniques. Among these, the polymerase chain reaction is the most sensitive method. Review of literature reveals that HPV may be a risk factor for malignancies, but not in all cases. For confirmation of the role of HPV in head and neck squamous cell carcinoma, large population studies are necessary in an assortment of clinical settings. Prophylactic vaccination against high-risk HPV types eventually may prevent a significant number of cervical carcinomas. Of the two vaccines currently available, Gardasil (Merck & Co., Inc.) protects against HPV types 6, 11, 16 and 18, while the other vaccine, Cervarix (GlaxoSmithKline, Rixensart, Belgium) protects against HPV types 16 and 18 only. However, the HPV vaccine has, to the best of our knowledge, not been tried in head and neck carcinoma. The role of HPV in etiopathogenesis, prevalence in benign and malignant lesions of this area and vaccination strategies are briefly reviewed here.

Eps8 decreases chemosensitivity and affects survival of cervical cancer patients

The oncoprotein Eps8 facilitates proliferation in fibroblasts and colon cancer cells. However, its role in human cervical cancer is unclear. By immunohistochemical staining and Western blotting, aberrant Eps8 expression was observed in cervical carcinoma compared with normal cervical epithelial cells. Clinicopathologic analysis of 45 patients indicated that Eps8 expression was associated with parametrium invasion and lymph node metastasis, two major poor prognostic factors for early-stage cervical cancer. Kaplan-Meier analysis of cervical cancer specimens also indicated an inverse relationship between the level of Eps8 and the patients' survival rate. Using small interfering RNA of eps8, we observed reduced proliferation and tumorigenesis in Eps8-attenuated HeLa and SiHa cells cultured in dishes or inoculated in mice. Furthermore, diminished Eps8 impeded G(1)-phase progression in HeLa and SiHa cells that might be attributable to reduced expression of cyclins D1, D3, and E, elevated accumulation of p53 and its downstream target p21(Waf1/Cip1), and suppressed hyperphosphorylation of retinoblastoma. Alteration of these cell cycle-related proteins could be reversed by ectopic Eps8, implicating that the effect of Eps8 on the mentioned cell cycle modulators was specific. Notably, the augmented expression of p53 by diminished Eps8 was at least due to its decreased turnover rate. Concurrent with p53 up-regulation and the decrement of Src and AKT activity, Eps8-attenuated HeLa and SiHa cells exhibited increased chemosensitivity to cisplatin and paclitaxel. Together, our findings implicate the involvement of Eps8 in chemoresistance and show its importance in prognosis of cervical cancer patients.

Human papillomavirus type 16 variant analysis of E6, E7, and L1 genes and long control region in biopsy samples from cervical cancer patients in north India

High-risk human papillomaviruses (HPVs), particularly HPV types 16 and 18 (HPV-16 and HPV-18, respectively), play a cardinal role in the etiology of cervical cancer. The most prevalent type, HPV-16, shows intratypic sequence variants that are known to differ in oncogenic potential and geographic distribution. This study was designed to analyze sequence variations in E6, E7, and L1 genes and the LCR (for long control region) of HPV-16 in cervical cancer patients to identify the most prevalent and novel HPV-16 variants and to correlate them with the severity of the disease. Cervical biopsies from 60 HPV-16-positive cancer cases were analyzed by PCR and DNA sequencing. The most frequently observed variations were T350G (100%) in E6, T789C (87.5%) in E7, A6695C (54.5%) in L1, and G7521A (91.1%) in the LCR. In addition, only one novel variant (T527A) in E6 and four new variants each in L1 (A6667C, A6691G, C6906T, and A6924C) and in the LCR (C13T, A7636C, C7678T, and G7799A) were identified. While E7 was found to be highly conserved, the variant 350G of E6 was the most prevalent in all of the histopathological grades. The majority of LCR variants were found at the YY1 transcription factor binding sites. Interestingly, a complete absence of the Asian lineage and a high prevalence of European lineages in E6, E7, L1, and the LCR (85, 86.7, 67.7, and 63.3%, respectively) indicate a possible epidemiological linkage between Europe and India with regard to the dissemination of HPV-16 infections in India.

Clinical efficacy of human papillomavirus DNA detection in urine from patients with various cervical lesions

A considerable number of adult Korean women avoid a Pap smear due to fear and discomfort of the pelvic examination. A reliable but noninvasive and comfortable screening method would considerably increase the participation rate. To evaluate the clinical efficacy of urine-based human papillomavirus (HPV) detection by oligonucleotide microarray, the results of HPV test from matched cervical swab specimens were compared. HPV DNA was detected in 70 of 100 cervical samples. HPV 16 was the most prevalent type (38/70), followed by types 18, 58, 52, 33, 35, 31, and 51. HPV DNA was identified in 47 of 90 urine samples. HPV 16 was the most prevalent type (30/45), followed by types 18, 52, 35, 51, 58, 33, and 56. The HPV detection rates of the cervical swabs increased in accordance with the severity of the cytologic and histologic diagnosis. The type specific agreement of HPV DNA tests between cervical swabs and urine was good in HPV 16 (kappa index=0.64 [95% CI: 0.50-0.79]), 18, 52, and 58 and fair in HPV 33 and 35. We propose that a urine HPV test is a valuable adjunctive method for a conventional Pap smear and can be used in population screening for cervical cancer in countries where it is difficult to obtain colposcopic specimens for cultural or religious reasons.

Oncogenic human papillomavirus (HPV) type distribution and HPV type 16 E6 variants in two Spanish population groups with different levels of HPV infection risk

The aim of this study is to determine oncogenic human papillomavirus (HPV) types and HPV type 16 (HPV16) variant distribution in two Spanish population groups, commercial sex workers and imprisoned women (CSW/IPW) and the general population. A multicenter cross-sectional study of 1,889 women from five clinical settings in two Spanish cities was conducted from May to November 2004. Oncogenic HPV infection was tested by an Hybrid Capture II (HC2) test, and positive samples were genotyped by direct sequencing using three different primer sets in L1 (MY09/11 and GP5+/GP6+) and E6/E7. HPV16 variants were identified by sequencing the E6, E2, and L1 regions. Four hundred twenty-five samples were positive for the HC2 test, 31.5% from CSW/IPW and 10.7% from the general population. HPV16 was the most frequent type. Distinct profiles of oncogenic HPV type prevalence were observed across the two populations. In order of decreasing frequency, HPV types 16, 31, 58, 66, 56, and 18 were most frequent in CSW/IPW women, and types 16, 31, 52, 68, 51, and 53 were most frequent in the general population. We analyzed HPV16 intratype variants, and a large majority (78.7%) belonged to the European lineage. AA variants were detected in 16.0% of cases. African variants belonging to classes Af1 (4.0%) and Af2 (1.3%) were detected. Different HPV types and HPV16 intratype variants are involved in oncogenic HPV infections in our population. These results suggest that HPV type distribution differs in CSW/IPW women and in the general population, although further analysis is necessary.

Genital warts in children: what do they mean?

Human papillomaviruses (HPVs) are a diverse family of viruses, of which 30-40 genotypes specifically infect the genital tract. Genital HPVs are largely transmitted sexually, with most infections being asymptomatic and transient. In contrast, persistent infection with oncogenic genotypes in a minority is a strong risk factor, for subsequent development of high grade dysplasia, the precursor lesion to cervical neoplasia, which generally occurs after a long latency period. It is unknown whether there is a disease correlate in children chronically infected with oncogenic HPVs. Low risk HPV genotypes 6 and 11 are the primary cause of condylomata acuminata, although in children non-genital genotypes are also found in a proportion, with the mode of transmission being either perinatal, horizontal, or sexual. The finding of asymptomatic HPV DNA in children, and correlation with live virus, infectivity, or disease is unclear. Long term follow up for children with anogenital warts is recommended, although there are no longitudinal studies available to clarify whether they are at risk of developing carcinoma in young adulthood.

Association between HLA-DQB1 and cervical dysplasia in Vietnamese women

Host genetic background seems to play a key role in cervical carcinogenesis as only a small subset of women infected with high-risk human papillomaviruses (HPVs) develop cervical cancer. The rate of cervical cancer in Vietnamese women is notably high. To explore the association of human leukocyte antigen (HLA)-DQB1 alleles, HPV infection, and cervical dysplasia in this population, cervical smears were obtained from 101 women attending the obstetrics and gynecology clinic of Da Nang General Hospital in Vietnam. Besides the Papanicolaou test, HPV and HLA-DQB1 genotyping were performed using cervical smear DNA. Additionally, a subset of 30 blood samples was used as the gold standard for HLA genotyping. HLA-DQB1 alleles showed no association with HPV infection status. However, a positive association with cervical dysplasia was found for HLA-DQB1*0302 (P= 0.0229, relative risk (RR) = 4.737) and HLA-DQB1*0601 (P= 0.0370, RR = 4.038), whereas HLA-DQB1*0301 (P= 0.0152, RR = 0.221) was found negatively associated. The low diversity of HLA-DQB1 alleles, wide spectrum of HPV genotypes, and high prevalence of HPV 16 and HPV 18 observed in the study population suggest a permissive/susceptible genetic background that deserves further research. Total concordance of HLA-DQB1 genotyping results between blood and cervical cells confirms the potential value of cervical smears as an effective tool for the development of cervical cancer biomarkers.

Pediatric anogenital warts: a 7-year review of children referred to a tertiary-care hospital in Montreal, Canada

The objectives of this study were to delineate the clinical characteristics of a hospital-referred pediatric population infected with anogenital warts and to investigate the possible relationships between human papillomavirus types and the identified clinical characteristics. Over a 7-year period, 72 patients under the age of 12 years were seen at our dermatology clinic for anogenital warts, corresponding to a prevalence of 1.7/1000 in our patient population. Sixty-four percent (46/72) were girls. Congenital, prenatal, ascending infections occurred in two subjects. The onset of anogenital warts occurred before age 2 in 28% and between 2 and 6 years of age in 62% of children and tended to be younger in boys. We identified unusual cutaneomucosal serotypes human papillomavirus 7 and 57 (three and eight instances, respectively). The modes of transmission of anogenital warts in children cannot be identified either by the clinical appearance of the lesions or by human papillomavirus typing. We conclude that the best way to identify possible sexual abuse is still by history taking, careful assessment of the socio-clinical context, and physical examination.

Human papillomaviruses: basic mechanisms of pathogenesis and oncogenicity

Human papillomaviruses (HPVs) are small double-stranded DNA viruses that infect the cutaneous and mucosal epithelium. Infection by specific HPV types has been linked to the development of cervical carcinoma. HPV infects epithelial cells that undergo terminal differentiation and so encode multiple mechanisms to override the normal regulation of differentiation to produce progeny virions. Two viral proteins, E6 and E7, alter cell cycle control and are the main arbitrators of HPV-induced oncogenesis. Recent data suggest that E6 and E7 also play a major role in the inhibition of the host cell innate immune response to HPV. The E1 and E2 proteins, in combination with various cellular factors, mediate viral replication. In addition, E2 has been implicated in both viral and cellular transcriptional control. Despite decades of research, the function of other viral proteins still remains unclear. While prophylactic vaccines to block genital HPV infection will soon be available, the widespread nature of HPV infection requires greater understanding of both the HPV life cycle as well as the mechanisms underlying HPV-induced carcinogenesis.

Prevalência do papilomavírus humano (HPV) na cavidade oral e na orofaringe

A prevalência do papilomavírus humano (HPV) na cavidade oral e na orofaringe ainda não está bem esclarecida como nos estudos do trato genital, na qual é bem definida. Entretanto, novas pesquisas estão surgindo após o aparecimento dos exames de biologia molecular. Neste estudo foi realizada uma revisão da literatura com o objetivo de verificar a prevalência do papilomavírus humano na cavidade oral e na orofaringe. Os resultados desta pesquisa mostraram uma prevalência do HPV 16 na mucosa oral normal (infecção latente). Já nas lesões benignas orais associadas ao HPV mostraram uma prevalência do HPV 6 e 11 em papilomas de células escamosas e condilomas, e, nas verrugas, uma prevalência do HPV 2 e 57, enquanto na hiperplasia epitelial focal prevaleceram os HPVs 13 e 32, e no câncer oral, principalmente, no carcinoma de células escamosas (CCE), foi evidenciada uma alta prevalência do HPV 16, o que sugere sua participação na carcinogênese oral, apesar de ser um assunto controverso. Constatou-se também uma enorme discrepância nos resultados da prevalência do papilomavírus humano (HPV) na mucosa oral normal (infecção latente) e no câncer oral, enquanto nas lesões benignas associadas ao vírus, os resultados foram confirmatórios.

Liposome-polycation-DNA (LPD) particle as a carrier and adjuvant for protein-based vaccines: therapeutic effect against cervical cancer

With the successful identification of many tumor-specific antigens, tumor-associated antigens, and the potential of using unfractioned tumor cell derivatives as tumor antigens, a system and/or adjuvant that can deliver these antigens and help them to induce strong and effective anti-tumor immune responses is greatly needed. Previously, we reported that a MHC class I-restricted peptide epitope derived from human papillomavirus (HPV) 16 E7 protein, when incorporated into a clinically proven safe LPD (liposome-polycation-DNA) particle, was able to effectively eradicate tumors established in mice. Cervical cancer is the second most common cancer among women worldwide. HPV infection is clearly linked to this cancer. Vaccines based on the early (E) gene products of HPV could be effective in controlling it. However, besides the fact that epitope vaccines have many limitations particularly, concerning the diverse HLAs in humans, the use of the epitope as an antigen prevented us from fully characterizing the immune responses induced by the LPD as a vaccine carrier and/or adjuvant in previous studies. In the present study, by using the HPV 16 E7 protein as an antigen, we first showed that LPD, as a vaccine carrier and adjuvant induced strong and robust immune responses, both cellular and antibody. We then showed that immunization with LPD particles incorporated with either the wild type HPV 16 E7 protein or a potentially safer mutant induced strong immune responses that caused complete regressions of a model cervical cancer tumor established in murines. LPD could be a potent vaccine carrier and/or adjuvant for many antigens.

Role of the E1--E4 protein in the differentiation-dependent life cycle of human papillomavirus type 31

The most highly expressed protein in the productive life cycle of human papillomaviruses (HPVs) is E1--E4, but its function is not well understood. To investigate the role of E1--E4, we undertook a genetic analysis in the context of the complete HPV type 31 (HPV31) genome. A mutant HPV31 genome (E4M9) was constructed that contained a stop codon in the E4 open reading frame at amino acid 9 and was silent in the overlapping E2 coding sequence. Wild-type and mutant genomes were transfected into normal human foreskin keratinocytes (HFKs) and selected for drug resistance, and pooled cultures were examined for effects of E1--E4 on viral functions. Southern blot analyses of transfected HFKs demonstrated that cells carrying the E4M9 mutant genomes were maintained as episomes at copy numbers similar to those in keratinocytes transfected with wild-type HPV31. Both sets of cells grew at similar rates, exhibited comparable extensions of life spans, and had equivalent levels of early transcripts. Following suspension of the cells in a semisolid medium, differentiation-dependent genome amplification and late gene expression were significantly decreased in cells maintaining the E4M9 mutant genome compared to those with wild-type HPV31. One explanation for these effects could be a reduction in the number of cells harboring mutant genomes that enter S phase upon differentiation. An analysis of cells containing E4M9 mutant genomes in organotypic raft cultures indicated a reduction in bromodeoxyuridine incorporation in differentiated suprabasal cells compared to that seen in wild-type rafts. Our results indicate that the HPV31 E1--E4 protein plays a significant role in promoting HPV genome amplification and S phase maintenance during differentiation.

Human papillomavirus genotypes and their association with cervical neoplasia in a cohort of Western Australian women

Human papillomavirus (HPV) is known to be the cause of almost all cervical cancers. The genotypes have been classified into high and low risk types according to their oncogenic potential. However, data for many of the genotypes are limited and some (HPV-26, 53, and 66) have no agreed status. A study was undertaken to determine the HPV genotype distribution in women of Western Australia and the association with cervical neoplasia. Liquid based cervical samples from a cohort of 282 Western Australian women were tested for HPV DNA by PCR followed by DNA sequencing to determine HPV genotypes. HPV-53 and HPV-16 were the most common genotypes found in this population. In addition 86 archived liquid based cervical samples from women with cervical intraepithelial neoplasia grades 1-3 (CIN 1-3) were tested for HPV DNA. Also 32 archived paraffin biopsy samples from women with squamous cell carcinoma were also tested. HPV-16 was the most common genotype found in these samples. Of the cohort of Western Australian women tested, 27% were found to contain HPV and approximately half of these contained known high-risk HPV genotypes, but only 30% of these were types 16 or 18. The data from this study indicate that HPV-53 is not oncogenic based on an R value and odds ratio (OR) of zero. The data also suggest that HPV-73 may be oncogenic, while HPV-66 is unlikely to be. Two high-risk HPV genotypes that are associated with the Asian region (HPV-52 and HPV-58) were found in Western Australian women suggesting a possible epidemiological link between women in these countries.

Presence of papillomavirus sequences in condylomatous lesions of the mamillae and in invasive carcinoma of the breast

BACKGROUND

Viruses including Epstein-Barr virus (EBV), a human equivalent of murine mammary tumour virus (MMTV) and human papillomavirus (HPV) have been implicated in the aetiology of human breast cancer. We report the presence of HPV DNA sequences in areolar tissue and tumour tissue samples from female patients with breast carcinoma. The presence of virus in the areolar-nipple complex suggests to us a potential pathogenic mechanism.

METHODS

Polymerase chain reaction (PCR) was undertaken to amplify HPV types in areolar and tumour tissue from breast cancer cases. In situ hybridisation supported the PCR findings and localised the virus in nipple, areolar and tumour tissue.

RESULTS

Papillomavirus DNA was present in 25 of 29 samples of breast carcinoma and in 20 of 29 samples from the corresponding mamilla. The most prevalent type in both carcinomas and nipples was HPV 11, followed by HPV 6. Other types detected were HPV 16, 23, 27 and 57 (nipples and carcinomas), HPV 20, 21, 32, 37, 38, 66 and GA3-1 (nipples only) and HPV 3, 15, 24, 87 and DL473 (carcinomas only). Multiple types were demonstrated in seven carcinomas and ten nipple samples.

CONCLUSIONS

The data demonstrate the occurrence of HPV in nipple and areolar tissues in patients with breast carcinoma. The authors postulate a retrograde ductular pattern of viral spread that may have pathogenic significance.

Inhibition of human papilloma virus E2 DNA binding protein by covalently linked polyamides

Polyamides are a class of heterocyclic small molecules with the potential of controlling gene expression by binding to the minor groove of DNA in a sequence-specific manner. To evaluate the feasibility of this class of compounds as antiviral therapeutics, molecules were designed to essential sequence elements occurring numerous times in the HPV genome. This sequence element is bound by a virus-encoded transcription and replication factor E2, which binds to a 12 bp recognition site as a homodimeric protein. Here, we take advantage of polyamide:DNA and E2:DNA co-crystal structural information and advances in polyamide synthetic chemistry to design tandem hairpin polyamides that are capable of displacing the major groove-binding E2 homodimer from its DNA binding site. The binding of tandem hairpin polyamides and the E2 DNA binding protein to the DNA site is mutually exclusive even though the two ligands occupy opposite faces of the DNA double helix. We show with circular permutation studies that the tandem hairpin polyamide prevents the intrinsic bending of the E2 DNA site important for binding of the protein. Taken together, these results illustrate the feasibility of inhibiting the binding of homodimeric, major groove-binding transcription factors by altering the local DNA geometry using minor groove-binding tandem hairpin polyamides.

Modulation of the cell division cycle by human papillomavirus type 18 E4

The life cycle of human papillomaviruses (HPVs) is tightly coupled to the differentiation program of their host epithelial cells. HPV E4 gene expression is first observed in the parabasal layers of squamous epithelia, suggesting that the E4 gene product contributes to the mechanism of differentiation-dependent virus replication, although its biological function remains unclear. We analyzed the effect of HPV type 18 E4 on cell proliferation and found that E4 expression induced cell cycle arrest at the G(2)/M boundary. The functional region of E4 necessary for the growth arrest activity was located in the central portion of the molecule, and this activity was independent of the E4-mediated collapse of cytokeratin intermediate filament structures.

Human papilloma viruses and cervical tumours: mapping of integration sites and analysis of adjacent cellular sequences

BACKGROUND

In cervical tumours the integration of human papilloma viruses (HPV) transcripts often results in the generation of transcripts that consist of hybrids of viral and cellular sequences. Mapping data using a variety of techniques has demonstrated that HPV integration occurred without obvious specificity into human genome. However, these techniques could not demonstrate whether integration resulted in the generation of transcripts encoding viral or viral-cellular sequences. The aim of this work was to map the integration sites of HPV DNA and to analyse the adjacent cellular sequences.

METHODS

Amplification of the INTs was done by the APOT technique. The APOT products were sequenced according to standard protocols. The analysis of the sequences was performed using BLASTN program and public databases. To localise the INTs PCR-based screening of GeneBridge4-RH-panel was used.

RESULTS

Twelve cellular sequences adjacent to integrated HPV16 (INT markers) expressed in squamous cell cervical carcinomas were isolated. For 11 INT markers homologous human genomic sequences were readily identified and 9 of these showed significant homologies to known genes/ESTs. Using the known locations of homologous cDNAs and the RH-mapping techniques, mapping studies showed that the INTs are distributed among different human chromosomes for each tumour sample and are located in regions with the high levels of expression.

CONCLUSIONS

Integration of HPV genomes occurs into the different human chromosomes but into regions that contain highly transcribed genes. One interpretation of these studies is that integration of HPV occurs into decondensed regions, which are more accessible for integration of foreign DNA.

Long-term effect of interferon on keratinocytes that maintain human papillomavirus type 31

The long-term effects of interferon treatment on cell lines that maintain human papillomavirus type 31 (HPV-31) episomes have been examined. High doses and prolonged interferon treatment resulted in growth arrest of HPV-positive cells, with a high percentage of cells undergoing apoptosis. These effects were not seen with interferon treatment of either normal human keratinocytes or cells derived from HPV-negative squamous carcinomas, which exhibited only slight decreases in their rates of growth. Within 2 weeks of the initiation of treatment, a population of HPV-31-positive cells that were resistant to interferon appeared consistently and reproducibly. The resistant cells had growth and morphological characteristics similar to those of untreated cells. Long-term interferon treatment of HPV-positive cells also resulted in a reduction in HPV episome levels but did not significantly decrease the number of integrated copies of HPV. Cells that maintained HPV genomes lacking E5 were sensitive to interferon, while cells expressing only the E6/E7 genes were resistant. In contrast, cells that expressed E2 from a tetracycline-inducible promoter were found to be significantly more sensitive to interferon treatment than parental cells. This suggests that at least a portion of the sensitivity to interferon could be mediated through the E2 protein. These studies indicate that cells maintaining HPV episomes are highly sensitive to interferon treatment but that resistant populations arise quickly.

Human papillomavirus infection and cyclin D1 gene amplification in laryngeal squamous cell carcinoma: biologic function and clinical significance

BACKGROUND

Human papillomavirus (HPV) infection is suspected to be a risk factor for head and neck, and in particular for laryngeal, carcinogenesis. Cyclin D1 gene (CCND1) overexpression and amplification have been shown to play a role as prognostic factors in many human cancers, among which are head and neck cancers.

METHODS

A literature review of the role in head and neck cancers of HPV infection and CCND1 overexpression and amplification was undertaken. We have evaluated the extent of the current knowledge in this field under the light of recent acquisitions, in particular, about a correlation between HPV infection, a suspected risk factor, and CCND1 amplification, a frequent mutation (about 20% of laryngeal cancers) and a prognostic factor in laryngeal SCC.

RESULTS AND DISCUSSION

The significant correlation between HPV infection and CCND1 amplification supports the hypothesis of the involvement of HPV infection in laryngeal carcinogenesis and suggests that HPV positive laryngeal cancers may constitute a different subset of tumors with a peculiar molecular pattern and thus with a different clinical behavior. HPV infection may be considered a synergistic risk factor with smoking and/or alcohol consumption to be investigated in heavy smokers and drinkers, thus contributing to the identification of patient at high-risk for the development of laryngeal cancer who should undergo strict follow-up and primary and secondary prevention.

Use of PGMY primers in L1 consensus PCR improves detection of human papillomavirus DNA in genital samples

The novel PGMY L1 consensus primer pair is more sensitive than the MY09 and MY11 primer mix for detection and typing with PCR of human papillomavirus (HPV) DNA in genital specimens. We assessed the diagnostic yield of PGMY primers for the detection and typing of HPV by comparing the results obtained with PGMY09/PGMY11 and MY09/MY11/HMB01 on 299 genital samples. Amplicons generated with PGMY primers were typed with the line blot assay (PGMY-line blot), while HPV amplicons obtained with the degenerate primer pool MY09/MY11/HMB01 were detected with type-specific radiolabeled probes in a dot blot assay (standard consensus PCR test). Cervicovaginal lavage samples (N = 272) and cervical scrape samples (N = 27) were tested in parallel with both PCR tests. The PGMY-line blot test detected the presence of HPV DNA more frequently than the standard consensus PCR assay. The concordance for HPV typing between the two assays was 84.3% (214 of 255 samples), for a good kappa value of 0.69. Of the 177 samples containing HPV DNA by at least one method, 40 samples contained at least one HPV type detected only with PGMY-line blot, whereas positivity exclusively with the standard consensus PCR test was found for only 7 samples (P < 0.001). HPV types 45 and 52 were especially more frequently detected with PGMY than MY primers. However, most HPV types were better amplified with PGMY primers, including HPV-16. Samples with discordant results between the two PCR assays more frequently contained multiple HPV types. Studies using PGMY instead of MY primers have the potential to report higher detection rates of HPV infection not only for newer HPV types but also for well-known genital types.

Much higher risk of premalignant and malignant cervical diseases in younger women positive for HPV16 than in older women positive for HPV16

Human papillomavirus (HPV), particularly HPV16, is strongly associated with premalignant lesions of the uterine cervix and cervical cancer. However, HPV infection is a common sexually transmitted disease and only a few women develop cervical cancer. Although the presence of HPV and abnormal cytology are independent risk factors for cervical diseases, implementing both tests on every woman is argued not to be recommended mainly in terms of cost-effectiveness. During a 20-month period between October, 1994, and May, 1996, cervical swabs from 207 women who were referred for colposcopy because of cervical dyskaryosis (Papanicolaou class IIIa or higher) were examined by PCR for the presence of HPV16. When these women were divided into two groups; i.e., group A consisting of women who were 44 years old or younger (n = 111), and group B consisting of women who were 45 years old or older (n = 96), the risk of having premalignant and malignant cervical diseases upon infection with HPV16 was approximately 8 times higher in group A than in group B. Thus, we conclude that HPV-testing should be implemented on every young woman with an abnormal Papanicolaou smear test.

Human papillomavirus positive squamous cell carcinoma of the oropharynx: a radiosensitive subgroup of head and neck carcinoma

BACKGROUND

Epidemiologic evidence points to a connection between viral infection by the human papillomavirus (HPV) and a subgroup of squamous cell carcinoma of the oropharynx. To assess the impact of HPV infection on the response of these tumors toward radiotherapy, the authors retrospectively determined the presence of the virus and the integrity of the viral E2 gene in tumors of patients who have undergone curative irradiation.

METHODS

Paraffin embedded biopsies from 99 patients were analyzed for HPV infection and E2 gene integrity by multiplex PCR. The experimental findings were correlated with clinical characteristics, known risk factors, and treatment outcome.

RESULTS

Fourteen of 99 tumors were HPV positive (11 HPV16, 1 HPV33, 1 HPV35, and 1 HPV45). Human papillomavirus positivity was closely linked to female gender (odds ratio [OR], 5.75; P = 0.004), age older than 56 years (OR, 7.42; P = 0.012), nonsmokers (OR, 21.33; P = 0.00001), and alcohol abstainers (OR, 5.35; P = 0.012). There was an inverse association with p53 nuclear immunoreactivity (OR, 0.06; P = 0.008). The Kaplan-Meier survival estimates showed a better local control (P = 0.050, log-rank) and a better overall survival (P = 0.046, log-rank) for patients with HPV positive tumors. In the multivariate analysis, HPV positivity remained to be associated with a lower risk of local failure (risk ratio [RR], 0.31; P = 0.048). Four of 11 HPV16 positive tumors had a disrupted E2 gene. Only tumors with a disrupted E2 gene manifested local treatment failure.

CONCLUSIONS

Human papillomavirus positivity designates a specific subgroup of oropharyngeal squamous cell carcinomas of the oropharynx that arise preferentially among individuals with no consumption of tobacco and alcohol and that have a favorable outcome attributable to an increased sensitivity toward radiotherapy.

Telomerase activation by human papillomavirus type 16 E6 protein: induction of human telomerase reverse transcriptase expression through Myc and GC-rich Sp1 binding sites

High-risk human papillomaviruses (HPVs) immortalize keratinocytes by disrupting the retinoblastoma protein (Rb)/p16 pathway and activating telomerase. The E7 oncoprotein targets Rb, while the E6 oncoprotein induces telomerase activity in human keratinocytes. This study has examined the mechanism by which E6 activates telomerase. Expression of human telomerase reverse transcriptase (hTERT), the catalytic subunit of telomerase, was found to be increased in keratinocytes stably expressing HPV type 16 E6, suggesting that E6 acts to increase hTERT transcription. hTERT expression and telomerase activity were activated to significantly higher levels in cells expressing both E6 and E7 than in cells expressing E6 alone. This indicates that E7 may augment E6-mediated activation of hTERT transcription. In transient-transfection assays using hTERT reporters, the induction of hTERT expression by E6 was found to be mediated by a 258-bp fragment of the hTERT promoter, proximal to the ATG initiation codon. Previous studies have demonstrated that overexpression of Myc can activate hTERT expression, suggesting that Myc may be a mediator of E6-mediated hTERT induction. However, in cells stably expressing E6, no strict correlation between the level of Myc and the activation of hTERT was found. Consistent with this observation, mutation of the two Myc binding sites in the hTERT promoter only modestly reduced responsiveness to E6 in transient reporter assays. This indicates that activation of Myc-dependent transcription is not essential for E6-mediated upregulation of hTERT expression. The hTERT promoter also contains five GC-rich elements that can bind Sp1. Mutation of these sites within the 258-bp fragment partially reduced hTERT induction by E6. However, when mutations in the Sp1 sites were combined with the mutated Myc binding sites, all activation by E6 was lost. This indicates that it is the combinatorial binding of factors to Myc and Sp1 cis elements that is responsible for hTERT induction by E6.

Distribution of HPV 53, HPV 73 and CP8304 in genital epithelial lesions with different grades of dysplasia

To characterize the risk of malignant progression of cervical epithelial lesions associated with human papillomavirus (HPV) types of yet unknown oncogenic potential the prevalences of these HPVs in different cervical epithelial lesions of 809 patients were determined. HPV types 53, 73, and CP8304 were detected in genital specimens of 16, 22, and 12 of the patients, respectively. The ratio of prevalence in high grade dysplastic lesions or cancers and low grade dysplastic lesions or normal specimens was calculated and compared to corresponding values of well known high-risk (HR) and low-risk (LR) HPVs. For HPV 6, 11, 16, 18, 35, and 73 a ratio of 0.1, 0.2, 5.9, 6.5, 2.5, and 2.4, respectively, was calculated. The ratios of HPV53 and CP8304 were less than 1. Moreover, in contrast to HPV73, these viruses have never been detected in cancer specimens. Thus, HPV53 and CP8304 infections are probably not associated with a high risk of carcinogenesis, while HPV73 could be another HR-HPV type.

Human papillomavirus virus-like particles are efficient oral immunogens when coadministered with Escherichia coli heat-labile enterotoxin mutant R192G or CpG DNA

Certain human papillomaviruses (HPVs) cause most cervical cancer, which remains a significant source of morbidity and mortality among women worldwide. HPV recombinant virus-like particles (VLPs) are promising vaccine candidates for controlling anogenital HPV disease and are now being evaluated as a parenteral vaccine modality in human subjects. Vaccines formulated for injection generally are more costly, more difficult to administer, and less acceptable to recipients than are mucosally administered vaccines. Since oral delivery represents an attractive alternative to parenteral injection for large-scale human vaccination, the oral immunogenicity of HPV type 11 (HPV-11) VLPs in mice was previously investigated; it was found that a modest systemic neutralizing antibody response was induced (R. C. Rose, C. Lane, S. Wilson, J. A. Suzich, E. Rybicki, and A. L. Williamson, Vaccine 17:2129-2135, 1999). Here we examine whether VLPs of other genotypes may also be immunogenic when administered orally and whether mucosal adjuvants can be used to enhance VLP oral immunogenicity. We show that HPV-16 and HPV-18 VLPs are immunogenic when administered orally and that oral coadministration of these antigens with Escherichia coli heat-labile enterotoxin (LT) mutant R192G (LT R192G) or CpG DNA can significantly improve anti-VLP humoral responses in peripheral blood and in genital mucosal secretions. Our results also suggest that LT R192G may be superior to CpG DNA in this ability. These findings support the concept of oral immunization against anogenital HPV disease and suggest that clinical studies involving this approach may be warranted.

Human papillomavirus variants and squamous neoplasia of the cervix

Human papillomaviruses (HPVs) play a central role in the aetiology of cervical neoplasia. However, only a small proportion of cervical intraepithelial lesions infected with high-risk HPVs will progress to invasive cervical carcinoma, which indicates the involvement of additional factors. An important emerging viral factor is naturally occurring intratypic sequence variation. Such variation has been used to study the geographical spread of HPVs, but there is increasing evidence that it may be important in determining the risk of development of neoplastic disease. The collected data indicate that different HPV variants have altered biochemical and biological properties and represent an additional risk factor in the development of squamous intraepithelial lesions and invasive carcinoma of the cervix. This may be relevant not only to the biology of HPV infection and its association with squamous neoplasia, but also to the use of HPV typing in clinical practice.

Immunological analyses of human papillomavirus capsids

Recombinant human papillomavirus (HPV) virus-like particles (VLPs) are promising vaccine candidates for controlling anogenital HPV disease. Questions remain, however, concerning the extent of capsid antigenic similarity between closely related virus genotypes. To investigate this issue, we produced VLPs and corresponding polyclonal immune sera from several anogenital HPV types, and examined these reagents in enzyme-linked immunosorbent assays (ELISAs) and in cross-neutralization studies. Despite varying degrees of L1 genetic sequence relatedness, VLPs of each type examined induced high-titer serum polyclonal antibody responses that were entirely genotype-specific. In an in vitro infectivity assay, only cognate VLP antisera were able to neutralize pseudovirions of HPV-16, HPV-18 and HPV-33, with two exceptions: HPV-31 and HPV-45 VLP post-immune sera demonstrated low levels of neutralizing activity against pseudovirions of HPV-33 and HPV-18, respectively. In other experiments, epitopes shared between closely related types were found to be less immunogenic than, and antigenically distinct from, primary type-specific B-cell determinants of the viral capsid. In addition, results from epitope blocking experiments suggested a close correlation between primary type-specific capsid antigenic sites and virion neutralization. These findings support the view that papillomavirus genotypes denote unique viral serotypes, and suggest that a successful vaccine for these viruses will likely require the inclusion of VLPs of each serotype for which protection is desired.

Presence of human papillomavirus and Epstein-Barr virus in the cervix of women infected with the human immunodeficiency virus

The presence of human papillomavirus (HPV) and Epstein-Barr virus (EBV) was sought in cervical scrapings from 110 human immunodeficiency virus (HIV)-infected women to evaluate the role of these viruses as risk factors for squamous intraepithelial lesions of the cervix. By using PCR, presence of HPV-DNA and EBV-DNA was found in 60.9% (67/110) and in 10% (11/110) of clinical samples, respectively. Identification of oncogenic group of HPV by hybrid capture (HC II, Murex-Digene) indicated the presence of low-risk HPV in 13 (19.4%) patients, high-risk HPV in 28 (41.8%), and both types of HPV in 26 (38.8%) patients. Squamous intraepithelial lesions were present in 59 cases, being low-grade (n = 52) and high-grade (n = 7) lesions. HPV was detected in 84.7% of patients with lesions, in association with low-grade (43/52) and high-grade lesions (7/7), and in 33% of patients without lesions. EBV-DNA was detected in 8 patients with low-grade lesions and in 3 patients without lesions. Concurrent genital HPV and EBV infection was observed in 9 cases. HPV was associated with detection of squamous intraepithelial lesions [OR = 3.55; 95% CI = (1.96; 6.48)]. No significant association was found between presence of EBV and detection of lesions, both in case of EBV infection alone [OR = 1.4; 95% CI = (0. 93; 2.12)] and in case of HPV/EBV combined infection [OR = 0.87; 95%CI = (0.54; 1.42)]. These data confirm the significant role of HPV as risk factor for squamous intraepithelial lesions and suggest that EBV could not be involved in the pathogenesis of the lesions that arise in the cervix of HIV-positive women.

The ubiquity and impressive genomic diversity of human skin papillomaviruses suggest a commensalic nature of these viruses

Human papillomaviruses (HPV) are epitheliotropic viruses, with some types suggested to be associated with skin cancer. In this study, swab samples collected from five different sites on the skin of renal transplant recipients, dialysis patients, and age- and sex-matched healthy controls were analyzed for HPV DNA by a newly designed PCR test. Most individuals were found to have asymptomatic HPV infections; more specifically, 94% of the renal transplant patients, 82% of the dialysis patients, and 80% of the healthy controls were positive for HPV DNA. The multiplicity of the HPVs detected was astounding: 20 previously described and 30 putatively new types were identified by cloning and sequencing of 33 samples from 13 individuals. These results demonstrate that normal human skin harbors an array of papillomaviruses, most of them previously unknown.

Treatment of warts at the turn of the millennium

Gunpowder may no longer be a recommended treatment for warts, but most of the therapies used in 1950 are still used to some extent now. The problems, now as then, are the multiplicity of treatment options and the lack of a cure. Several treatments popular in the past decade are discussed.

The E1E4 protein of human papillomavirus type 16 associates with a putative RNA helicase through sequences in its C terminus

Human papillomavirus type 16 (HPV16) infects cervical epithelium and is associated with the majority of cervical cancers. The E1E4 protein of HPV16 but not those of HPV1 or HPV6 was found to associate with a novel member of the DEAD box protein family of RNA helicases through sequences in its C terminus. This protein, termed E4-DBP (E4-DEAD box protein), has a molecular weight of 66,000 (66K) and can shuttle between the nucleus and the cytoplasm. It binds to RNA in vitro, including the major HPV16 late transcript (E1E4. L1), and has an RNA-independent ATPase activity which can be partially inhibited by E1E4. E4-DBP was detectable in the cytoplasm of cells expressing HPV16 E1E4 (in vivo and in vitro) and could be immunoprecipitated as an E1E4 complex from cervical epithelial cell lines. In cell lines lacking cytoplasmic intermediate filaments, loss of the leucine cluster-cytoplasmic anchor region of HPV16 E1wedgeE4 resulted in both proteins colocalizing exclusively to the nucleoli. Two additional HPV16 E1E4-binding proteins, of 80K and 50K, were identified in pull-down experiments but were not recognized by antibodies to E4-DBP or the conserved DEAD box motif. Sequence analysis of E4-DBP revealed homology in its E4-binding region with three Escherichia coli DEAD box proteins involved in the regulation of mRNA stability and degradation (RhlB, SrmB, and DeaD) and with the Rrp3 protein of Saccharomyces cerevisiae, which is involved in ribosome biogenesis. The synthesis of HPV16 coat proteins occurs after E1E4 expression and genome amplification and is regulated at the level of mRNA stability and translation. Identification of E4-DBP as an HPV16 E1E4-associated protein indicates a possible role for E1E4 in virus synthesis.

Human tumor growth is inhibited by a vaccinia virus carrying the E2 gene of bovine papillomavirus

BACKGROUND

Papillomavirus is the etiologic agent associated with cervical carcinoma. The papilloma E2 protein is able to regulate negatively the expression of E6 and E7 papilloma oncoproteins. Therefore, a new, highly attenuated vaccinia virus known as modified vaccinia virus Ankara (MVA), which carries the papillomavirus E2 gene, was used for the treatment of tumors associated with human papillomavirus.

METHODS

Analysis of expression of the E2 gene from the recombinant vaccinia virus was performed by reverse transcription-polymerase chain reaction of RNA isolated from infected cells. Detection of the E2 protein was done by immunoprecipitation from proteins labeled with [(35)S]-methionine, isolated from infected cells. The therapeutic effect of the MVA E2 recombinant virus over human tumors was tested in nude mice bearing tumors generated by inoculation of HeLa cells. Series of 10 nude mice with tumors of different sizes were injected with MVA, MVA E2, or phosphate-buffered saline. Tumor size was monitored every week to assess growth.

RESULTS

The MVA E2 recombinant virus efficiently expressed the E2 protein in BS-C-1 cells. This protein was able to repress, in vivo, the papillomavirus P105 promoter, which controls the expression of the E6 and E7 oncoproteins. In nude mice the MVA E2 virus reduced tumor growth very efficiently. In contrast, tumors continued to grow in mice treated with MVA or PBS. The life expectancy of MVA E2-treated mice was also increased three- to fourfold compared with that of animals that received MVA or PBS.

CONCLUSIONS

The growth of human tumors was efficiently inhibited by the MVA E2 recombinant vaccinia virus. The absence of side effects in treated animals suggested that the MVA E2 virus is a safe biologic agent that could in the future be used in humans for the treatment of cervical carcinoma.

Seroepidemiology of human papillomavirus type 73: a sexually transmitted low-risk virus

Human papillomavirus type 73 (HPV 73) has been detected in some invasive cervical cancers and has been cloned from a squamous-cell carcinoma of the esophagus, but the epidemiology of this infection and its associated risk of cancer is unknown. We investigated the seroepidemiology of this virus using virus-like particles. The IgG response to HPV 73 appeared to be HPV type-specific, since a comparison of HPV 73 antibody levels before and after infection with HPV 6, 11, 16, 18 or 33 found no evidence of cross-induction of HPV 73 antibodies and since there was little correlation between the antibody levels to HPV 73 and the other 5 investigated HPV types. In both a cross-sectional serosurvey that included 274 women and a 7-year follow-up study that enrolled 98 women, HPV 73 seropositivity was found to be strongly dependent on the number of lifetime sexual partners [OR for > 4 vs. 0 to 1 partners: 6.0 (95%CI: 1.4-53.6) and 7.9 (95% CI: 2.8-28.3), respectively]. Finally, the risk for HPV 73 seropositive women to develop CIN was investigated in a prospective study nested in a cohort of 15,234 Swedish women. The population-based HPV 73 seroprevalence in Sweden was 14%. No excess risk for CIN was found (OR: 0.77). We conclude that HPV 73 is a mainly sexually transmitted, probably mostly transient, infection that does not confer any measurably increased risk for CIN development.

Papillomaviruses in human cancers

Papillomaviruses have proved to be the most complex group of human pathogenic viruses. Eighty-five genotypes have been fully characterized; approximately 120 additional isolates represent only partially characterized putative novel genotypes. Specific types, most notably human papillomavirus (HPV) types 16, 18, and a few others, have been shown to cause the majority of cervical cancers and their high-grade precursor lesions. The viral oncogenes E6 and E7 are required for the initiation and maintenance of the malignant phenotype in HPV-positive cancers. Proteins coded by these genes are multifunctional and interfere with important cell cycle regulatory proteins. Expression of viral oncogenes is tightly controlled in nondifferentiated keratinocytes by at least two signaling cascades, one operative at the functional level, the other at the transcriptional level. The latter has been partially characterized. Papillomaviruses are also suspected of playing a role in a subset of oropharyngeal cancers, in squamous cell cancers of the skin, and possibly also in esophageal cancers. Clinical trials are being conducted to test the preventive and therapeutic efficacy of HPV vaccines, directed particularly against HPV 16 and 18. If proven to be effective, their global application should have a measurable effect on the worldwide incidence of cancer.