Biochemical characterization of two types of human papillomaviruses associated with epidermodysplasia verruciformis

Beta human papillomavirus 8E6 promotes alternative end joining

Double strand breaks (DSBs) are one of the most lethal DNA lesions in cells. The E6 protein of beta-human papillomavirus (HPV8 E6) impairs two critical DSB repair pathways: homologous recombination (HR) and non-homologous end joining (NHEJ). However, HPV8 E6 only delays DSB repair. How DSBs are repaired in cells with HPV8 E6 remains to be studied. We hypothesize that HPV8 E6 promotes a less commonly used DSB repair pathway, alternative end joining (Alt-EJ). Using CAS9-based Alt-EJ reporters, we show that HPV8 E6 promotes Alt-EJ. Further, using small molecule inhibitors, CRISPR/CAS9 gene knockout, and HPV8 E6 mutant, we find that HPV8 E6 promotes Alt-EJ by binding p300, an acetyltransferase that facilitates DSB repair by HR and NHEJ. At least some of this repair occurs through a subset of Alt-EJ known as polymerase theta dependent end joining. Finally, whole genome sequencing analysis showed HPV8 E6 caused an increased frequency of deletions bearing the microhomology signatures of Alt-EJ. This study fills the knowledge gap of how DSB is repaired in cells with HPV8 E6 and the mutagenic consequences of HPV8 E6 mediated p300 destabilization. Broadly, this study supports the hypothesis that beta-HPV promotes cancer formation by increasing genomic instability.

Beta Human Papillomavirus 8E6 Attenuates Non-Homologous End Joining by Hindering DNA-PKcs Activity

Cutaneous viral infections occur in a background of near continual exposure to environmental genotoxins, like UV radiation in sunlight. Failure to repair damaged DNA is an established driver of tumorigenesis and substantial cellular resources are devoted to repairing DNA lesions. Beta-human papillomaviruses (β-HPVs) attenuate DNA repair signaling. However, their role in human disease is unclear. Some have proposed that β-HPV promotes tumorigenesis, while others suggest that β-HPV protects against skin cancer. Most of the molecular evidence that β-HPV impairs DNA repair has been gained via characterization of the E6 protein from β-HPV 8 (β-HPV 8E6). Moreover, β-HPV 8E6 hinders DNA repair by binding and destabilizing p300, a transcription factor for multiple DNA repair genes. By reducing p300 availability, β-HPV 8E6 attenuates a major double strand DNA break (DSB) repair pathway, homologous recombination. Here, β-HPV 8E6 impairs another DSB repair pathway, non-homologous end joining (NHEJ). Specifically, β-HPV 8E6 acts by attenuating DNA-dependent protein kinase (DNA-PK) activity, a critical NHEJ kinase. This includes DNA-PK activation and the downstream of steps in the pathway associated with DNA-PK activity. Notably, β-HPV 8E6 inhibits NHEJ through p300 dependent and independent means. Together, these data expand the known genome destabilizing capabilities of β-HPV 8E6.

Loss of Genome Fidelity: Beta HPVs and the DNA Damage Response

While the role of genus alpha human papillomaviruses in the tumorigenesis and tumor maintenance of anogenital and oropharyngeal cancers is well-established, the role of genus beta human papilloviruses (β-HPVs) in non-melanoma skin cancers (NMSCs) is less certain. Persistent β-HPV infections cause NMSCs in sun-exposed skin of people with a rare genetic disorder, epidermodysplasia verruciformis. However, β-HPV infections in people without epidermodysplasia verruciformis are typically transient. Further, β-HPV gene expression is not necessary for tumor maintenance in the general population as on average there is fewer than one copy of the β-HPV genome per cell in NMSC tumor biopsies. Cell culture, epidemiological, and mouse model experiments support a role for β-HPV infections in the initiation of NMSCs through a "hit and run" mechanism. The virus is hypothesized to act as a cofactor, augmenting the genome destabilizing effects of UV. Supporting this idea, two β-HPV proteins (β-HPV E6 and E7) disrupt the cellular response to UV exposure and other genome destabilizing events by abrogating DNA repair and deregulating cell cycle progression. The aberrant damage response increases the likelihood of oncogenic mutations capable of driving tumorigenesis independent of a sustained β-HPV infection or continued viral protein expression. This review summarizes what is currently known about the deleterious effects of β-HPV on genome maintenance in the context of the virus's putative role in NMSC initiation.

Quantification of beta-human papillomavirus DNA by real-time PCR

Quantitative PCR with hybridization probes allows the reliable quantification of viral DNA sequences in clinical samples with a dynamic range and sensitivity that cannot be achieved with other methods. The technical background for the establishment of protocols is described and established protocols are presented to estimate the viral load per cell of frequently occurring betapapillomaviruses (HPV5, -8, -15, -20, -23, -24, -36 and -38) in skin tumors, healthy skin and hair bulbs. This approach accurately adjusts dilution series of reference DNA of different viral types relative to pUC18, which is crucial for comparative analyses and for interlaboratory standardization. The type-specific determination of beta-HPV DNA loads is an important research tool toward discrimination between low-level persistence and activated possibly pathologically relevant infections. The analysis of 24 samples, starting with DNA extraction and followed by HPV typing and quantification of-on average-three of the described HPV types takes about 2 d.

Epidermodysplasia verruciformis: a model for understanding the oncogenicity of human papillomaviruses

The first evidence for the oncogenic potential of human papillomaviruses (HPVs) was obtained through the study of epidermodysplasia verruciformis (EV). This rare skin disease is characterized by disseminated, refractor, pityriasis versicolor-like lesions as well as flat wart-like lesions, and by the development of skin carcinomas in about 30% of the patients. EV is a multifactorial disease involving genetic, immunological and extrinsic (actinic) factors, in addition to infection with specific HPV types. A number of HPVs (at least 15 types) have been characterized in benign EV lesions. HPV DNA sequences are regularly detected in EV carcinomas but, in contrast to benign lesions, the types associated with cancers are usually restricted to HPV-5 and, less frequently, HPV-8, an HPV-5-related type. HPV-5 genomes are usually found as free monomeric or oligomeric DNA molecules in EV carcinomas, and frequently contain deletions. This is in contrast with HPV DNA sequences in genital cancers, which are often integrated into the host DNA. Evidence for the transcription of HPV-5 genomes in primary and metastatic EV carcinomas has recently been obtained. The available data indicate that HPV-5 and some HPV-5-related types have an oncogenic potential and play a role in the malignant transformation of EV lesions. Infection by these HPVs must be considered a major risk factor for the development of cancers in EV patients. EV HPV DNA sequences have only rarely been detected in premalignant or malignant lesions of the skin in the general population. This further stresses the role of genetic, immunological and extrinsic factors in the abnormal susceptibility of EV patients to a set of specific HPV types.

Human papillomavirus detection in cervical cells by in situ hybridization with biotinylated probes

We have investigated the applicability of human papillomavirus (HPV) DNA detection by in situ hybridization with biotinylated probes in epithelial cells obtained from the cervix using a cotton tip swab. We describe a simple procedure for obtaining homogeneous cell samples and good preservation of cellular structure. This is achieved by pretreatment of cells with L-cysteine before hybridization. Separate denaturation of cellular DNA and probe DNA is also necessary for satisfactory results. Both benign HPV DNA 6/11 and potentially oncogenic HPV DNA 16/18 could be identified in our series. In situ hybridization on cervical scrapes is a rapid, simple and very specific method for detecting patients infected with oncogenic HPV types.

Detection and identification of human papillomavirus types isolated from Korean patients with flat warts

Flat warts, also called verruca planna (VP) or juvenile warts, are benign epithelial proliferations of the skin caused by infection with human papillomaviruses (HPV). Several HPV types are known to be associated with flat warts, and particularly HPV type 3 and 10 have been most frequently reported in other countries. In this study, for the detection and typing of human papillomavirus isolated from Korean patients with flat warts, polymerase chain reaction (PCR) and restriction endonuclease digestion were carried out with a set of restriction endonucleases, using the cloned HPV DNA and DNA from clinical specimens. A unique digestion pattern for HPV type 3 and 10, a form of miniature fingerprinting, enabled us to identify HPV type from the amplified fragments. A total of thirty clinical samples, as either frozen tissue or paraffin-embedded tissue, were investigated to verify the type. All the clinical samples except one were con-firmed to be type 3, one of the most frequently observed types in flat warts, and one sample was neither type 3 nor type 10. Further investigation of the unidentified sample by DNA sequencing and sequence alignment with other known HPV types revealed that the sample was a variant of HPV type 94, one of the EV-related HPVs, with the closest evolutionary distance to the HPV type 10 among the known flat wart-associated HPV types.

Pigmented Epidermal Plaques in Three Dogs

Papillomavirus was identified in pigmented epidermal plaques (PEP) from three dogs: a miniature schnauzer with hyperadrenocorticism and hypoglobulinemia, an American Staffordshire terrier with hypoglobulinemia, and a Pomeranian with unconfirmed hypothyroidism. Squamous cell carcinoma (SCC) arose within several plaques in the Pomeranian. Clinical improvement coincided in the first two cases with treatment of the concurrent disease and the administration of low-dose oral interferon-α. This is the first report of PEP in an American Staffordshire terrier and a Pomeranian. The potential for malignant transformation of PEP to SCC emphasizes the need for recognition and clinical management of PEP.

Vaccines for cervical cancer

Human papillomaviruses (HPVs) are responsible for the nearly 450,000 cervical cancers that occur each year throughout the world. In the United States, the cancer rate is low (13,500 cases per year); nevertheless, HPVs affect millions of men and women annually in the form of genital warts and preinvasive diseases of the cervix and anogenital region. The expense of cancer prevention via precancer and cancer management is high, yet most HPV infections resolve spontaneously as a result of a successful host immune response. Recently, the discovery of methods to reproduce HPV virions (viral-like particles) in vitro has resulted in a successful clinical trial of preventing HPV infection and its associated precursor lesions. Although prevention is type-specific and duration of immunity is unknown, these results validate a vaccine strategy targeting prepubertal children that could prevent a significant proportion of genital warts and cervical precancers and cancers from occurring during reproductive life. Reversing advanced preinvasive and invasive cervical neoplasia with immunotherapeutics is a more difficult challenge, inasmuch as little or no evidence for natural immune-mediated regression of these diseases exists. Nonetheless, recent controlled trials have shown some success in inducing precursor regression with vaccines targeting viral oncoproteins. Anecdotal reports of therapies that augmentcellular immunity raise hopesthattherapeutics targeting multiple pathways of anti-viral or anti-tumor immunity will be beneficial to women with established cervical cancer. However, success will require identifying and circumventing the mechanisms by which tumor cells evade the immune system.

Innovations in understanding the biology of cervical cancer

Revelation of the connection between the human papillomavirus (HPV) and cervical neoplasia and invasive cervical cancer is prompting new investigations to expand that understanding and promote vaccines, gene therapy, and other interventions. At the Second International Conference on Cervical Cancer (Houston, TX, April 11-14, 2002), laboratory and clinical researchers reported advances in new studies meant to increase understanding of the natural history of HPV and cervical intraepithelial neoplasia, to evaluate new cervical cancer screening techniques, and to promote new therapies. Using K14-HPV type 16 transgenic mice, researchers are investigating the effects of estrogen on cervical cancer carcinogenesis, and results are lending support to epidemiological theories showing a difference in HPV infection rates and the development of cervical lesions in women using oral contraceptives. Other work involves investigating genes that are up-regulated by HPV infection and the role of the p53 homologue, p63, in cervical neoplasia evolution. Telomerase also is under investigation as a biomarker in high-risk populations. Gene therapy that replaced p53 in cervical cancer cell lines in vitro and a nude mouse model inhibited cell and tumor growth, confirming previous findings in squamous epithelial carcinomas of the head and neck. Furthermore, research in intracellular targeting of antigens to subcellular locations shows promise for treating cervical cancer preclinically. Identification of molecular changes in cervical cancer and knowledge about the importance of HPV infection in cervical cancer can lead to new therapies to treat existing cervical cancer and, in the long term, prevent the disease.

Mutation and abnormal expression of the p53 gene in the viral skin carcinogenesis of epidermodysplasia verruciformis

Patients suffering from epidermodysplasia verruciformis are prone to nonmelanoma skin cancers, due to an inherited abnormal susceptibility to the oncogenic human papillomavirus type 5. Genotoxic sunlight ultraviolet B radiations are likely to be a cofactor. Lesions of two human-papillomavirus-type-5-infected epidermodysplasia verruciformis patients collected during an 8 y period were retrospectively studied for p53 mutations in exons 5 through 8 by a polymerase chain reaction single-strand conformation polymorphism technique and/or by DNA sequencing of amplified exons. Mutations were detected in 11 of 26 (42.3%) specimens, including five (62.5%) squamous cell carcinomas, three (33.3%) Bowen's carcinomas in situ, two (40%) actinic keratoses, and one (33%) benign lesion. The nine mutations characterized by sequencing were shown to be missense and to affect mutational hotspots in human cancers. Five were C-->T transitions at dicytidine sites considered as ultraviolet signature mutations. Two were transversions (C-->G and C-->A) at dicytidine sites and two were C-->T transitions at nondipyrimidine sites. A marked p53 immunoreactivity was disclosed in 72.7% of 11 invasive carcinomas, 55.6% of nine carcinomas in situ, 37.5% of eight actinic keratoses, and one of three benign lesions. This includes 81.8% of 11 specimens with a p53 mutation but also 50% of 14 specimens with no mutation detected. A dysfunction of the p53 gene is thus likely to play a part in epidermodysplasia verruciformis carcinogenesis, either due to ultraviolet-B-induced p53 mutations, as in nonmelanoma skin cancers in the general population, or involving other mutagens or mechanisms. The part played by human papillomavirus type 5 proteins expressed in epidermodysplasia verruciformis keratinocytes remains to be determined.

Detection of human papillomavirus (HPV) type 47 DNA in malignant lesions from epidermodysplasia verruciformis by protocols for precise typing of related HPV DNAs

Our discovery of human papillomavirus type 47 (HPV47) in benign lesions from a patient suffering from epidermodysplasia verruciformis prompted us to examine whether the viral DNA also resided in malignant lesions from the same patient. By using newly devised protocols for amplifying a group of epidermodysplasia verruciformis-associated HPV DNAs by PCR and differentially identifying them by reverse-phase dot blot hybridization, we demonstrated that HPV47 DNA, but not other HPV DNAs of the group, was abundant (about 10(3) copies per diploid amount of cell DNA) in DNAs prepared from three carcinomas. Using DNA from one of these carcinomas, we also confirmed that DNA of HPV5, HPV14, or HPV21, detected in significant amounts in DNAs from benign lesions from the patient, were present only in negligible amounts or not at all. The results suggest the involvement of HPV47 DNA in tumorigenesis. Furthermore, we demonstrated by the Southern technique that most, if not all, of the HPV47 DNA consists of either a unit (or a nongrossly deleted unit) length of the viral genome carrying no (or no gross) internal rearrangements or tandem repeats. This and other results obtained by this technique indicated that a considerable amount of the viral DNA resides as a circular monomer a unit length of the viral genome in carcinoma cells, while the remainder reside as catenanes, concatemers, or both. The concatemers were considered more likely to be replicated without integration into cellular DNA than to be integrated, because no bands for the corresponding fragments including integration sites were detected by treatment with restriction enzymes that would have produced such fragments.

Analysis of genomic sequences of 95 papillomavirus types: uniting typing, phylogeny, and taxonomy

Our aim was to study the phylogenetic relationships of all known papillomaviruses (PVs) and the possibility of establishing a supratype taxonomic classification based on this information. Of the many detectably homologous segments present in PV genomes, a 291-bp segment of the L1 gene is notable because it is flanked by the MY09 and MY11 consensus primers and contains highly conserved amino acid residues which simplify sequence alignment. We determined the MY09-MY11 sequences of human PV type 20 (HPV-20), HPV-21, HPV-22, HPV-23, HPV-24, HPV-36, HPV-37, HPV-38, HPV-48, HPV-50, HPV-60, HPV-70, HPV-72, HPV-73, ovine (sheep) PV, bovine PV type 3 (BPV-3), BPV-5, and BPV-6 and created a database which now encompasses HPV-1 to HPV-70, HPV-72, HPV-73, seven yet untyped HPV genomes, and 15 animal PV types. Three additional animal PVs were analyzed on the basis of other sequence data. We constructed phylogenies based on partial L1 and E6 gene sequences and distinguished five major clades that we call supergroups. One of them unites 54 genital PV types, which can be further divided into eleven groups. The second supergroup has 24 types and unites most PVs that are typically found in epidermodysplasia verruciformis patients but also includes several types typical of other cutaneous lesions, like HPV-4. The third supergroup unites the six known ungulate fibropapillomaviruses, the fourth includes the cutaneous ungulate PVs BPV-3, BPV-4, and BPV-6, and the fifth includes HPV-1, HPV-41, HPV-63, the canine oral PV, and the cottontail rabbit PV. The chaffinch PV and two rodent PVs, Micromys minutus PV and Mastomys natalensis PV, are left ungrouped because of the relative isolation of each of their lineages. Within most supergroups, groups formed on the basis of cladistic principles unite phenotypically similar PV types. We discuss the basis of our classification, the concept of the PV type, speciation, PV-host evolution, and estimates of their rates of evolution.

Nested PCR approach for detection and typing of epidermodysplasia verruciformis-associated human papillomavirus types in cutaneous cancers from renal transplant recipients

The epidermodysplasia verruciformis (EV)-associated human papillomaviruses (HPVs) constitute a group of HPV genotypes isolated mostly from the cutaneous lesions of patients with the genetic disorder of EV. Broad-spectrum detection of EV HPVs in cutaneous lesions of non-EV patients was previously difficult because no EV HPV consensus PCR was available. We describe a nested PCR that enables the detection of all known EV HPV types at relatively low-copy-number levels. The deduced sequences of a 92-amino-acid stretch of the L1 open reading frames of all types are shown for convenient typing. The technique proved very valuable in viral studies of skin cancers from renal transplant recipients. A high prevalence (81%) of EV HPV types was found in skin cancer biopsies. A wide spectrum of EV HPV types that differed from HPV-5 and -8 was found to be involved. The technique also proved useful in detecting potentially novel EV HPV types in skin cancers. The relationship of these new types to known HPV types is demonstrated by phylogenetic tree analysis.

Genetic heterogeneity of oncogenic human papillomavirus type 5 (HPV5) and phylogeny of HPV5 variants associated with epidermodysplasia verruciformis

Variants of oncogenic human papillomavirus type 5 (HPV5), specifically associated with epidermodysplasia verruciformis, were recognized on the basis of the genetic heterogeneity of the E6 open reading frame (ORF). To further evaluate the genetic heterogeneity of HPV5, we sequenced the long control region (LCR), the E7 ORF, and the terminal parts of the E2 ORF of five previously characterized HPV5 variants and compared the data with the published HPV5a1 and HPV5b sequences. Alignment of the variants showed 140 (7.6%) variable nucleotides of 1,854 sequenced. Nucleotide substitution rates varied from 3.6% in the E7 ORF to 11% in the E6 ORF. By sequencing the variable region encompassing the LCR 3' part and the E6 ORF of isolates from six additional epidermodysplasia verruciformis patients, we identified three new variants and three already known variants, indicating the stability of HPV5 variants. This stability was further demonstrated by the identity of isolates obtained years later from benign and malignant lesions of three patients. Phylogenetic analysis of the 10 HPV5 variants distributed them into three groups, tentatively defining subtypes a, b, and c. The phylogenetic grouping shows no geographical dependence, a fact that may be related to the host restriction that characterizes HPV5 infections. No differences in the enhancer potential of the LCR or in the transactivating properties of the E2 protein assayed in vitro were observed among HPV5 variants. Whether HPV5 variants possess distinct biological properties in vivo remains to be determined.

Characterization of human papillomavirus type 66 from an invasive carcinoma of the uterine cervix

Human papillomavirus (HPV) DNA sequences coexisting with HPV16 and HPV45 were cloned from an invasive cervical carcinoma. The cloned HPV was shown to be a novel type, named HPV66, and is related to HPV56 (an HPV detected in cervical cancer). After screening 160 anogenital biopsies, four specimens exhibited histological features of intraepithelial neoplasia and contained HPV66 sequences. Of these, three were found to be associated with another HPV type.

Genetic heterogeneity among human papillomaviruses (HPV) associated with epidermodysplasia verruciformis: evidence for multiple allelic forms of HPV5 and HPV8 E6 genes

In order to get some insight into modifications of human papillomavirus (HPV) genomes which could play a role in tumor progression in epidermodysplasia verruciformis (EV), we studied three EV patients infected by HPV5 and one by HPV8, with cancers containing mostly or only episomal viral genomes with a deletion. The mutants were compared with the full-length genomes present in the benign lesions of each patient. Deletions affected the L1 and/or L2 open reading frames (ORFs), and extended in the 5' end of the long control region in two cancers. The isolates studied showed a polymorphism of restriction endonuclease cleavage sites and variations in the nucleotide sequence of the E6 ORF and the regions flanking the deletions. However, except for one patient infected by two distinct HPV5 variants, no difference was observed in the nucleotide sequence of isolates cloned from the benign lesions and the cancer of the same patient. This may suggest that point mutations are not involved in tumor progression. Comparison of nucleotide sequence data revealed an unexpectedly high number of nucleotide substitutions among the four HPV5 variants and the HPV8 variant, as compared with HPV5 and HPV8 published sequences. Changes involved 49 of the 457 nucleotides of HPV5 E6 ORF and 14 of the 465 nucleotides of HPV8 E6 ORF. This corresponds to amino acid substitutions affecting 17 of the 157 amino acids of HPV5 E6 proteins and 7 of the 155 amino acids of HPV8 E6 proteins. Half of the substitutions represent nonconservative changes. The variants showing the highest degree of sequence variation were detected in additional EV patients by PCR. This points to the existence of a set of HPV5 and HPV8 stable variants, encoding for multiple allelic forms of the transforming E6 gene.

Epidermodysplasia verruciformis associated human papillomaviruses present a subgenus-specific organization of the regulatory genome region

The regulatory regions of the human papillomaviruses (HPVs) 9, 17, 20, and 36 were mapped, sequenced, and aligned. They revealed an arrangement of putative protein binding sites specific for the epidermodysplasia verruciformis associated HPVs. Three subgroups could be differentiated.

Natural cell-mediated cytotoxicity against various target cells in patients with epidermodysplasia verruciformis

Natural cell-mediated cytotoxicity of peripheral blood mononuclear cells was studied in eight patients with epidermodysplasia verruciformis induced by human papillomaviruses specific for epidermodysplasia verruciformis and in five patients with epidermodysplasia verruciformis-induced exclusively by human papillomavirus type 3. Nine patients with various cutaneous warts and 25 age- and sex-matched healthy persons were control subjects. Natural cell-mediated cytotoxicity against both K-562 erythroleukemic and Sk-v cells was in the normal range in patients with epidermodysplasia verruciformis induced by epidermodysplasia verruciformis-specific human papillomaviruses and in patients with cutaneous warts. The lysis of both targets, however, was significantly decreased in patients with the form of epidermodysplasia verruciformis associated with human papillomavirus type 3. Experiments with normal keratinocytes and with keratinocytes isolated from a malignant lesion bearing human papillomavirus type 5 genomes showed that the latter were susceptible to lysis by the peripheral blood mononuclear cells of healthy persons and of patients with cutaneous warts. Lysis of keratinocytes in epidermodysplasia verruciformis, however, was strongly reduced in patients with epidermodysplasia verruciformis induced by specific human papillomaviruses. This reduction was not associated with a decrease in anti-K-562 natural cell-mediated cytotoxicity. Our results suggest that in patients with epidermodysplasia verruciformis induced by disease-specific human papillomaviruses, there is reduced natural cell-mediated cytotoxicity against epidermodysplasia verruciformis keratinocytes.

Selective detection of human papilloma virus DNAs by specific synthetic DNA probes

Specific oligodeoxynucleotide probes ranging from 20 to 35 nucleotides were defined to differentiate each of the HPV1a, 5, 6b, 8, 11, 16, 18 and 33. They were chosen using computer programs developed to compare simultaneously several 8000 bp long DNA sequences. Sequences common to all and to specific groups of the HPV DNA were also selected. Specificity of 32P-labelled probes for HPV6b, 11, 16, 18 and 33 was demonstrated and the sensitivity of the assays was evaluated by filter hybridization with viral clones and with DNA from cervical tumor biopsies.

Human papillomaviruses and carcinomas

The recognition of multiple types of human papillomaviruses has resulted in remarkable progress in the detection of persisting viral nucleic acid sequences in carcinomas. The consistent transcription in tumors of two early open reading frames, E6 and E7, with few exceptions (Lehn et al., 1985), indicates a role for the products of these genes in the induction and/or maintenance of the transformed state. A number of studies have shown that in vitro transformation can be achieved by transfection of E6/E7 DNA, and proteins encoded by these DNA sequences can be demonstrated in primary human keratinocytes immortalized by this DNA (Kaur et al., 1989). Mutagenesis experiments are needed to determine the absolute requirement for and function of these genes in transformation. A preferential association of some types with benign lesions while others may be frequently found in malignant tumors has been observed. HPV types 5 and 8 in epidermodysplasia verruciformis patients and types 16, 18, 31, 33, etc. in genital lesions are most frequently associated with progression to malignancy, whereas other types, such as HPV-6,-10, -11, and -20, are regularly identified in benign warts. Such distinctions are not absolute but provide the initial steps toward establishing a causal role for some human papillomaviruses in carcinomas. The need for well-designed epidemiological studies in concert with optimum molecular and serologic evaluations is evident (Armstrong et al., 1988). The data from human and animal studies indicate that papillomaviruses contribute significantly to the development of many, if not all, carcinomas, but we do not yet have a clear understanding of the importance of other interacting viral, chemical, or cellular factors. The application of gene cloning and non-stringent hybridization (Law et al., 1979) has provided us with an apparently ever-increasing catalog of human papillomaviruses. More effort is now required to establish their prevalence, the natural history of infection, and the mechanism of neoplastic transformation.

Future trends in cervical cancer

The identification of the close association of certain types of human papillomavirus with the development of cervical cancer should lead to an extensive revision of appropriate health policies. Having taken into account the drawbacks inherent in the existing data (stemming from the use of varying nomenclature, diagnostic methods and reliability, registration and screening practices) it is possible to conclude that the incidence of HPV infections, all premalignant and malignant stages of cervical cancer are, or will soon be, increasing in several countries. This rate of increase is fastest for the younger age groups and is despite the introduction of various forms of screening. These trends therefore indicate an urgent need to adopt policies to avert an unnecessary increase in fatalities due to cervical cancer. It is therefore recommended to: (1) establish a routine diagnostic method which can identify either the type of HPV present or the lesions which are progressing; (2) determine the incidence of HPV infections in the general population; (3) disseminate to medical personnel, teachers, and other members of society existing knowledge concerning the dangers associated with this virus and relevant to preventing its further spread; (4) introduce an effective population screening campaign for all sexually active women, preferably involving a yearly examination at a colposcopy clinic; (5) intensify basic and applied HPV research, especially that which could lead to a deeper understanding of viral transmission and infection, identification of cofactors which promote cervical lesion progression, or to the production of a vaccine.

Epidermodysplasia verruciformis in a patient with Hodgkin's disease: characterization of a new papillomavirus type and interferon treatment

A new human papillomavirus (HPV) was discovered in disseminated, macular, pityriasis versicolor-like lesions on the skin of the neck, face, scalp, and pubic region of a 42-year-old male suffering from Hodgkin's disease. Histopathology revealed features characteristic of epidermodysplasia verruciformis (ev). In contrast to classical ev, the lesions were almost exclusively seen in previously irradiated and UV-exposed skin areas. Papillomavirus capsid antigen was demonstrated with the genus-specific antiserum and the patient's serum, which had IgM and IgG antibody titers. HPV DNA was isolated from biopsies and cloned into the vector pIC20H. It proved to be related to ev-associated viruses, showing 23% cross-hybridization with DNA of the closest relative HPV14. The new HPV type was named HPV46. The genome was physically mapped and colinearly aligned with HPV8 DNA to establish its gene organization. Interferon treatment of the patient did not significantly change the clinical picture nor was the concentration of viral DNA per lesion affected. However, no virus capsid antigen was detectable after starting treatment.

Papillomaviruses in human skin warts and their incidence in an Argentine population

Human papillomavirus genomic types present in human warts of an Argentine population were studied. HPV DNA from single warts was obtained using an alkaline extraction procedure that resulted in a clean DNA preparation, which could be analyzed with several endonucleases. This method was used to isolate and insert the HPV DNAs of two genomic types into the Bam HI site of the pBR322 plasmid. Restriction maps of both HPV DNAs were constructed. According to these maps, one of the genomic variations was identical to HPV1a and the other to HPV2a. The incidence of HPV2 and of HPV1 in different types of skin warts was studied by a dot blot hybridization assay. Twenty-two out of 28 common warts were positive for HPV2 and negative for HPV1; four were positive for HPV1 and negative for HPV2 and two were negative for both. Five out of six plantar warts were positive for HPV1, and one was negative for both. Three out of seven filiform warts were positive for HPV2, three were positive for both probes, and one was negative for both. Southern blot analysis of HPV2 positive samples indicated that 80% were HPV2a and 20% another subtype not yet characterized. All plantar warts contained HPV1a. Msp I/Hpa II restriction analysis confirms previous results indicating that HPV1a DNA is partially methylated, while no evidence of methylation was found for HPV2a DNA.

Papillomaviruses: the current status in relation to oral disease

Human papillomaviruses of different types are associated with a variety of benign oral lesions and may be associated with some premalignant and malignant oral lesions. However, since it is now clear that a variant of human papillomavirus 16 is harbored by normal oral mucosa, as well as by premalignant and malignant lesions, such associations may not necessarily always be causal. The rapid progress of recent research in this field is reviewed, with particular reference to oral disease, and the current status is discussed.

Plurality of genital human papillomaviruses: characterization of two new types with distinct biological properties

The genomes of two new genital human papillomavirus (HPV) types, tentatively named HPVs 39 and 42, have been cloned from biopsy specimens of penile Bowenoid papules and vulvar papillomas, respectively. Blot hybridization experiments, performed under stringent conditions (Tm -10 degrees), have revealed no cross-hybridization between the DNAs of HPVs 39 and 42, and between these DNAs and those of other genital and cutaneous HPVs. A significant cross-hybridization has been observed between the DNA of HPV42 and that of HPV32, the latter being associated with oral focal epithelial hyperplasia. The fraction of HPV32 and HPV42 hybrid molecules resistant to nuclease S1 treatment after hybridization in liquid phase at saturation has been evaluated to 20%, supporting the view that these HPVs constitute distinct types. In addition to HPV42 DNA, a 6.8-kb BamHI fragment, cross-hybridizing with HPV39 DNA, has been cloned from the vulvar papilloma DNA preparation. The cross-hybridization has been evaluated to 16%, pointing to the existence of an additional HPV39-related type. Electron microscope analysis of heteroduplex molecules formed between HPV32 and HPV42 DNAs showed paired regions over about 60 and 87% of their genome lenghts under stringent (Tm -18 degrees) and nonstringent (Tm -42 degrees) conditions, respectively. The 6.8-kb HPV DNA and HPV39 DNA formed paired regions over about 63 and 95% of the 6.8-kb fragment length at Tm -18 degrees and Tm -26 degrees, respectively. These data point to greater DNA sequence homologies than anticipated from the percentages of nuclease S1 resistance. Heteroduplex mapping has allowed the alignment of the physical maps of HPV39 and 42 DNAs and of the 6.8-kb HPV DNA with the map of the open reading frames of the HPV16 genome. So far, HPV42 has been detected only in benign genital lesions showing usually no cell atypia. HPV39 has been detected in a few cases of intraepithelial neoplasias and invasive carcinomas of the uterine cervix. The viral DNA sequences have been found integrated into the cell genome in all four HPV39-associated cervical cancers of our series. It seems most likely that HPV42 belongs to the low-risk group of genital HPVs, while HPV39 represents a potentially oncogenic genital HPV type.

The molecular biology of human papillomaviruses and the pathogenesis of genital papillomas and neoplasms

Numerous studies over the past several years have demonstrated that human papillomaviruses (HPV) may play a significant role in the development of several types of human neoplasia. Although it has been accepted for some time that HPVs are responsible for benign epithelial tumors, data accumulated in more recent years have implicated this group of animal viruses in a number of premalignant lesions, as well as a variety of epithelially derived malignancies. Genital, oral, and some rare types of cutaneous cancers have all been found to contain varying degrees of HPV DNA. In several instances secondary tumors resulting from metastases to lymph nodes and lungs have also been demonstrated to contain HPV DNA. Although there is a strong correlation between the presence of the virus and the malignant phenotype in several of these cancers, the precise role of the virus in the development of malignant tumors has not yet been elucidated. A major difficulty in elucidating the role of papillomaviruses in oncogenesis has been the lack of an appropriate in vitro culture system that would permit the growth of the virus and allow an analysis of its transforming properties. Nevertheless, recent advances in molecular biology have permitted the molecular cloning and amplification of HPV viral DNA, thereby facilitating its use as a probe for the detection of miniscule amounts of HPV DNA and HPV RNA in tumor biopsies. Moreover, DNA transfections of cells in culture have been extremely useful in the study of viral DNA replication and transformation properties, providing information on the maintenance and oncogenicity of HPV DNA. These advances have implications for the improved detection of HPV infections, which will aid in patient diagnosis and prognosis. In addition, future treatment and prevention programs may come as a direct result of these basic studies on the mechanism of HPV-induced oncogenesis.

A new type of papillomavirus associated with cancer of the uterine cervix

A new human papillomavirus (HPV) type was detected by low-stringency Southern blot hybridization analysis of DNA from an endocervical adenocarcinoma. The genomic DNA of the virus, which was obtained as two BamHI fragments of 3.75 and 4.1 kb, was molecularly cloned into lambda L47 and subsequently subcloned into pBR322 for further characterization. Hybridization studies demonstrated that these viral DNA isolates were only distantly related to other HPV and thus represented a new type of HPV, called HPV 35. A restriction enzyme map was prepared which allowed a comparison of the genetic organization of this HPV with that of HPV 6b; the results demonstrated collinearity of the HPV 35 genome with that of HPV 6b. Prevalence studies revealed that HPV 35 was present in 2 of 158 (1%) anogenital intraepithelial neoplasia and in 3 of 69 (4%) anogenital cancers. Thus HPV 35 is a low-prevalence human papillomavirus associated with anogenital intraepithelial neoplasia and cancer.

Human papillomavirus type 17 transcripts expressed in skin carcinoma tissue of a patient with epidermodysplasia verruciformis

Certain types of human papillomavirus (HPV) are involved in skin carcinogenesis in epidermodysplasia verruciformis. However, no gene or gene product of HPV associated with skin carcinogenesis has yet been identified. Here, we report HPV-17 transcripts expressed in skin carcinoma tissue of an epidermodysplasia verruciformis patient infected with HPV-17. Further, we show that one of these transcripts was localized to a portion of the genome which contains the 3' open reading frames of the early region (E2, E3, E4 and E5). The analogous region in bovine papillomavirus type I has been shown to contain a transforming gene (Nakabayashi et al., 1983; Sarver et al., 1984; Yang et al., 1985a).

Nucleotide sequence and genome organization of human papillomavirus type 5

Human papillomavirus (HPV) type 5 is associated with benign and malignant lesions of the disease epidermodysplasia verruciformis (EV). Because of the strong correlation between the presence of HPV-5 and malignant progression in these patients, we have elucidated the nucleotide sequence of the HPV-5 genome. The size of the HPV-5 genome is 7746 nucleotides and its organization is similar to that of other papillomaviruses. The HPV-5 genome exhibits extensive sequence homology with another EV-associated papillomavirus, HPV-8, although HPV-5 appears to contain at least one additional open reading frame.

A new type of human papillomavirus associated with oral focal epithelial hyperplasia

Lesions from 10 patients suffering from focal epithelial hyperplasia (FEH) of the oral mucosa, including those of 4 Greenlandic Eskimos, were investigated for the presence of human papillomavirus (HPV) DNA sequences by blot hybridization experiments. Two distinct HPVs were detected in the DNA extracted from these lesions, and their genomes were molecularly cloned and characterized. One of these HPVs, detected in 4 patients, was found to be identical with HPV13, whose association with FEH was already known. The other one, detected in 6 patients, was only weakly related to HPV13 and to the other HPVs associated with lesions of the mucous membranes, and constituted a new HPV type, tentatively named HPV32. Lesions from other types of oral papillomas, obtained from 14 additional patients, were also analyzed. Human papillomavirus DNA sequences were detected in the DNA preparations extracted from 5 specimens: HPV6 DNA in a condyloma and in a papilloma, 2 as yet uncharacterized HPV DNAs in 2 papillomas, and HPV32 DNA in a papilloma which showed histologic similarities to FEH. Thus, it seems likely that FEH of the oral mucosa is a disease associated with 2 specific HPVs--HPV13 and HPV32.

Partial defects of cell-mediated immunity in patients with epidermodysplasia verruciformis

Different parameters of cell-mediated immunity, including natural cytotoxic reactions, were studied in nine patients with epidermodysplasia verruciformis with or without cutaneous malignancy. We found decreased total number of T lymphocytes and T-helper cells in peripheral blood of the patients, and normal T-suppressor cell number, as detected by monoclonal antibody typing and functional E-rosette test with the use of theophylline. This decrease was found both in active and in late rosette-forming cell subpopulations. Natural killer cell activity of peripheral blood mononuclear cells was found to be increased in four of nine patients with epidermodysplasia verruciformis, whereas antibody-dependent cellular cytotoxicity was within the normal range in all patients studied. Lymphocyte-induced angiogenesis assay, which is a sensitive test for the estimation of the immunocompetence of lymphoid cells, revealed increased angiogenic capability of peripheral blood mononuclear cells in the majority of the patients. Our results suggest that cellular defects in patients with epidermodysplasia verruciformis did not relate to all functions of the immune system.

Characterization of a new type of human papillomavirus (HPV) related to HPV5 from a case of actinic keratosis

Human papillomavirus (HPV) DNA sequences, related to the genomes of HPVs associated with epidermodysplasia verruciformis (EV), were detected in DNA samples extracted from biopsied lesions in 2 of 24 cases of actinic keratosis found in the general population. An HPV DNA was molecularly cloned from one of these samples. Blot hybridization experiments, performed under stringent conditions, revealed a significant cross-hybridization only between this HPV DNA and the DNAs of HPV5 and of the HPV5-related types. The extent of homology between them ranged from 7 to 30%, as evaluated by hybridization in liquid phase at saturation followed by nuclease S1 analysis. This showed that the cloned HPV represented a new type, tentatively named HPV36. HPV36 was not found in the other 22 cases of actinic keratosis, but was detected in scrapings of benign lesions of 7 of 18 (39%) EV patients.

The role of human papillomaviruses in the pathogenesis and histologic classification of precancerous lesions of the cervix

It is clear that the relation between HPV infection and cervical neoplasia is more complex than initially realized. Preliminary molecular virologic data suggest preferential distributions of low- and high-risk HPV types in CIN that tend to correlate with the morphologic appearance. Thus, mild and moderate dysplasias (CIN I and II) contain a diverse distribution of HPV types, including a minority that have a high risk of malignant potential. HPV, therefore, appears to play a major role as a promoter. Neoplastic transformation is probably determined by specific HPV types but, in addition, requires initiation by some other carcinogenic stimulus, e.g., HSV II, cigarette smoking. Despite numerous studies, performed during the past 30 years, the long-term behavior of dysplasia remains uncertain. The natural history of HPV-associated lesions is unknown. Until this information is available, it is recommended that the conventional dysplasia--CIS or CIN nomenclature be used. The presence of associated viral changes can be considered and added to the diagnosis, e.g., "moderate dysplasia (CIN II) with evidence of papillomavirus infection." Treatment should be the same for all intraepithelial lesions, regardless of the presence of morphologic evidence of HPV. In the future, it may be necessary to modify the classification of precancerous lesions of the cervix if it is shown that a specific HPV type induces a characteristic morphologic alteration or that the HPV type, in and of itself, has greater prognostic significance. Until then, confusion will be minimized and management optimized if the conventional dysplasia--CIS or CIN nomenclature is employed.

A novel type of human papillomavirus associated with genital neoplasias

The role of human papillomaviruses (HPVs) in the development of genital neoplasias has been well documented. The genomes of two HPV types, HPV16 and HPV18, have been found to be associated with about 70% of invasive carcinomas of the uterine cervix. As, under non-stringent hybridization conditions, HPV DNA sequences have been detected in about 90% of cervical carcinomas, it seems likely that additional HPV types are associated with these tumours. Here we report the molecular cloning and characterization of a novel HPV type, tentatively named HPV33, whose sequences have been detected in 4-8% of biopsies of genital intra-epithelial neoplasias and cervical invasive carcinomas, usually as free monomeric or oligomeric molecules. However, in one specimen of vulvar Bowen's disease, HPV33 DNA sequences were integrated in the host-cell genome. Thus, HPV33 probably represents an additional type of potentially oncogenic genital HPV.

Detection of papillomavirus DNA in oral papillomas and carcinomas: application of in situ hybridization with biotinylated HPV 16 probes

Four oral papillomas and 7 carcinomas were studied for the presence of HPV DNA by means of in situ hybridization. Hybridization was carried out with a HPV 16 probe labelled with biotin under different conditions (nick translation/photobiotin). Subsequently, a modified biotin-avidin-alkaline phosphatase procedure was used to visualize virus infected cells. Four/4 papillomas and 4/7 carcinomas were seen to contain HPV harbouring cells. Positive cells were located at intermediate and superficial cell layers in papillomas and in keratinized zones in carcinomas. Analogous results were found with nick translated and photobiotinylated probes. DNA-biotinylation in conjunction with the biotin-avidin-alkaline phosphatase detection system proved to be a sensitive, convenient and rapid modification of in situ hybridization.

Epidermodysplasia verruciformis-associated human papillomavirus 8: genomic sequence and comparative analysis

Human papillomavirus (HPV) 8 induces skin tumors which are at high risk for malignant conversion. The nucleotide sequence of HPV8 has been determined and compared to sequences of papillomaviruses with different oncogenic potential. The general organization of the HPV8 genome is similar to that of other types. Highly conserved, genus-specific sequences were found in open reading frames (ORFs) E1, E2, and L1. In ORFs E6, E7, and L2, HPV8 is more distantly related, but it was possible to differentiate subgenera in which HPV8 belonged to the HPV1-cottontail rabbit papillomavirus group. Sequences within ORF E4 and part of ORF L2 are rather type specific. HPV8 stands out by several unique features: the considerably reduced size of the noncoding region (397 base pairs), with a seemingly low potential for forming complex secondary structures; a cluster of putative promoter elements in the 3' half of ORF E1; an RNA polymerase III promoter-like sequence close to the C terminus of ORF E2; and of particular interest, the homology between the putative protein encoded by ORF E4 and the Epstein-Barr virus nuclear antigen 2 protein, which may reflect similar mechanisms in virus-mediated transformation.

Molecular cloning of two new HPV types (HPV 37 and HPV 38) from a keratoacanthoma and a malignant melanoma

Several benign and malignant skin tumors were analyzed for the presence of human papillomavirus (HPV) DNA. By hybridization with different HPV DNA probes under non-stringent conditions (Tm -40 degrees C), two tumors were found to contain HPV-specific DNA sequences in high copy numbers: (1) a keratoacanthoma from a patient who also suffered from a basalioma; (2) a superficial spreading malignant melanoma of an immunosuppressed patient. For further analysis of these DNA sequences genomic libraries from both tumor DNAs were constructed and, out of these, 4 different HPV DNA types have been cloned. By cross-hybridization experiments and restriction map analysis HPV 9 DNA was identified in the keratoacanthoma whereas HPV 17a DNA could be cloned from the malignant melanoma. From each tumor one additional HPV-type not identical to other known HPV-types was cloned. These isolates are closely related to HPV 9, 15, 17, 22 and 23. A physical map of both HPV DNAs was constructed. Size (7.8 kbp), co-linear alignment to HPV 16, cross-hybridization with other HPV-types under conditions of low stringency and monomeric episomal state of the HPV molecules indicate that these two DNA probes represent new HPV types that have been tentatively designated as HPV 37 (keratoacanthoma) and HPV 38 (malignant melanoma). None of these two HPV types could be found in any other of 231 tumor DNAs originating from different tissues.

Characterization of a new type of human papillomavirus found in a lesion of Bowen's disease of the skin

The genome of a human papillomavirus (HPV) found in a patient with Bowen's disease of the skin was molecularly cloned. Blot hybridization experiments, performed under stringent conditions, revealed no cross-hybridization between this HPV DNA and the other known HPV DNAs, showing that this HPV represents a new type, tentatively named HPV34. In relaxed hybridization conditions, the highest cross-hybridization was observed with HPV16 DNA. The physical map of HPV34 DNA was aligned with the genetic map of HPV16 DNA by heteroduplex mapping. HPV34 was not detected in 12 additional patients with Bowen's disease of the skin, but a closely related HPV DNA was found in one patient with penile Bowenoid papulosis.

Papillomaviruses: their possible role in oral disease

Papillomaviruses are ubiquitous DNA viruses that are epitheliotropic and produce a range of epithelial neoplasms, both benign and malignant, in animals and man. Human papillomaviruses are associated with a variety of rare and uncommon oral lesions, and there has been increasing suspicion that they may be implicated also in some premalignant and malignant oral lesions.

Human papillomavirus type 17 DNA in skin carcinoma tissue of a patient with epidermodysplasia verruciformis

Epidermodysplasia verruciformis (EV) is a serious skin disease caused by certain types of human papillomavirus (HPV), because the flat wart-like lesions of EV very frequently change to malignant squamous cell carcinoma. The relation between HPV and skin carcinoma was examined by studies on an EV patient who had a squamous cell carcinoma. HPV-17 was isolated from EV lesions of this patient. With HPV-17 DNA as a probe, cellular DNA prepared from the carcinoma tissue was analyzed by Southern blot hybridization. Results showed that cells contained about 100 copies of monomeric and oligomeric extrachromosomal HPV DNA. These results suggest that HPV-17 is involved in skin carcinogenesis in EV.