Specific identification of human papillomavirus type in cervical smears and paraffin sections by in situ hybridization with radioactive probes: a preliminary communication

Assessment of attribution algorithms for resolving CIN3-related HPV genotype prevalence in mixed-genotype biopsy specimens using laser capture microdissection as the reference standard

To make accurate determinations regarding potential and actual impact of HPV vaccine programs, precise estimates of genotype-specific contributions to disease are required for pre- and post-vaccine populations. Definitive determination of lesion-specific genotypes, particularly where multiple genotypes are detected in a sample, can be technically demanding and resource intensive; therefore, most prevalence studies use mathematical algorithms to adjust for multiple genotype detections. There are currently several algorithms, which can produce genotype estimates within a wide range of variability. The use of these for cervical cytology samples has recently been assessed for accuracy against a definitive reference standard, but none have yet been assessed for multiple-genotype-containing whole biopsy specimens. Using laser capture microdissection (LCM) on biopsy samples, lesion-specific genotype prevalence data were generated for a cohort of 516 young Australian women (aged 18-32 years) with cervical intraepithelial neoplasia grade 3 or adenocarcinoma in situ. Using whole tissue section genotype data from the same cohort, including 71 (13.7%) with multiple genotypes, lesion-associated genotype prevalence was estimated using four different attribution algorithms. The proportion of lesions attributable to HPV16 and HPV18 by LCM were 58.4% and 5%, respectively; hierarchical, proportional, single type/minimum and any type/maximum attribution estimates were comparable across genotypes. For analyses utilising whole tissue biopsy cervical specimens, attribution estimates are appropriate for estimating the proportional contribution of individual genotypes to lesions in a population.

Methods for diagnosing papillomavirus infection

The morphology of the lesion and the site in which the lesion is found are the initial clues in classifying papillomavirus-induced neoplasia. Human papillomavirus (HPV) types have limited site-specificity and differ in their association with benign or malignant neoplastic development. Cytopathology, electron microscopy, antigen detection and molecular hybridization all play a role in the armamentarium of diagnostic methods. Although nitrocellulose blotting procedures provide the most accurate and sensitive method for detecting and characterizing viral nucleic acid sequences, recent improvements in cytological hybridization methods allow for rapid detection of virus and analysis of HPV type directly in biopsied tissue and in cervical smears. In particular, these in situ hybridization procedures facilitate retrospective studies of stored specimens.

Close relationship between equine and human molluscum contagiosum virus demonstrated by in situ hybridisation

To determine whether the virus responsible for human molluscum contagiosum (MCV) is the causal agent of a similar disease in horses, in situ hybridisations using cloned fragments of human MCV DNA labelled with digoxigenin were carried out on formalin-fixed biopsy sections of lesions from two horses with molluscum contagiosum-like skin lesions. In both instances there was evidence of specific hybridisation of the labelled probe to target DNA in the sections under high stringency conditions, identified by the development of a deep blue-purple stain in the cytoplasm of cells in the stratum spinosum and stratum granulosum of the lesions and the absence of non-specific hybridisation in adjacent non-lesional areas of the epidermis. These results indicate that on the basis of very close homology of their viral DNA sequences, the causative virus of equine molluscum contagiosum is either identical with, or very closely related to, its human equivalent.

Detection of human papillomavirus infection by non-isotopic in situ hybridisation in condylomatous and CIN lesions

AIMS

To study the value of non-isotopic in situ hybridisation (NISH) in detecting human papillomavirus (HPV) infection in female genital lesions positive for the virus by conventional histology but negative by filter DNA hybridisation.

METHODS

Forty three cases, which showed the histological hallmarks of the HPV infection but produced negative results in filter dot blot hybridisation tests (Vira Pap and Vira Type kits), were identified in the course of an investigation of 304 vaginal, vulvar, and cervical samples from 267 patients. These cases were studied by NISH for the presence of HPV infection.

RESULTS

In 28 (65%) of the cases NISH gave a positive hybridisation signal. In 26 cases (96%) the signal was diffuse, and in two (4%) punctate or diffuse, representing episomal and episomal or integrated HPV DNA, respectively. In most cases only a few HPV positive cells were discernible.

CONCLUSION

NISH is a more sensitive technique than dot blot hybridisation, detecting HPV infection in most cases which show histological HPV atypia but which remain negative in filter DNA hybridisation. Thus NISH is useful as an additional technique to verify the presence of HPV in lesions which remain negative in filter hybridisation tests.

Deleterious effects of formalin/acetic acid/alcohol (FAA) fixation on the detection of HPV DNA by in situ hybridization and the polymerase chain reaction

As part of a study of archival cervical cancer specimens (1920s to 1980s) to determine whether changes have occurred in the prevalence of human papillomavirus (HPV) DNAs, investigations were performed on tissues which had been fixed in either 10% buffered formalin (NBF) or formalin-acetic acid-alcohol (FAA). HPV DNA was detected by in situ hybridization (ISH) using HPV 6, 11, 16 and 18 32P-labelled DNA probes under conditions of high stringency; and by the polymerase chain reaction (PCR) using 20-mer oligonucleotide primers to amplify 109 bases of the E6 region of HPV 16. In some instances results obtained from Southern blot hybridizations, which had been carried out on specimens of fresh cancer tissue, were available for comparison. When tissues had been fixed in NBF, HPV DNA sequences were detected in 53% of specimens by ISH and in 72% by PCR. In comparison, the rates of detection of HPV by ISH and PCR in tissues fixed in FAA were 17% and 21% respectively. These results indicate that FAA is clearly inferior to NBF for the preservation of detectable HPV DNA sequences in tissue sections.

Comparison of four non-radioactive and 35S-based methods for the detection of human papillomavirus DNA by in situ hybridization

Human papillomavirus DNA was detected in 40 condylomatous lesions of various sites (vulva, cervix, larynx, penis and anus) by in situ hybridization using 35S-labelled probes and four non-radioactive probes to compare the various sensitivities of these techniques on the same material (formalin-fixed and paraffin-embedded sections). Radioactive probes yielded 28 positive results out of 40 (70%). Sulphonated probes (HybriCyte kit) also gave 28 positive results with a fine pattern of hybridization grains and equal sensitivity to 35S-labelled probes. Biotinylated and digoxigenin-labelled probes gave analogous results (25 positive reactions with the PathoGene kit, 26 with the Viratype kit, and 25 with digoxigenin-labelled probes) but are slightly less sensitive than radiolabelled and sulphonated probes especially when the signal is weak.

Human papillomavirus DNA as a possible index of invasiveness in female genital tract carcinomas

Paraffin-embedded tumour sections were used for the polymerase chain reaction (PCR) with three primer sets that amplify specific regions of human papillomavirus (HPV) types 11, 16 and 18. The positive samples were confirmed by hybridisation of the amplified sequences with the specific HPV probes. In all screened metastases the same viral sequences were found as in the primary tumour. HPV 16 was the most frequently detected virus in genital tract tumours. In a metastatic ovary carcinoma with unknown primary site HPV 16 DNA was observed. Moreover, pelvic lymph nodes with no microscopic evidence of metastases contained HPV DNA of the same subtype as the primary tumour. Thus, the HPV DNA detected by PCR is a useful indicator of neoplastic cells in the earlier stages of invasiveness. The finding of specific HPVs in the metastatic lesions could also provide information about the location of the primary neoplasia.

Comparative in situ hybridisation study of juvenile laryngeal papillomatosis in Papua New Guinea and Australia

A comparative study of cases of juvenile laryngeal papillomatosis from Papua New Guinea (n = 3) and Brisbane, Australia (n = 9) was carried out. In situ hybridisation reactions for human papillomavirus (HPV) types 6 and 11 occurred in 11 cases. All three cases from Papua New Guinea and eight from Australia gave positive signals. A negative reaction was observed in one Australian case. The intensity of the reaction was strong in seven cases, moderate in one, and weak in three. An equivocal reaction was also noted with probes for types 16 and 18, and types 31, 33, and 35 in two cases from Australia and one from Papua New Guinea. It is concluded that as similar staining patterns and intensities occurred in cases from both areas, the aetiology is the same. The equivocal reactions noted in three cases were probably due to cross hybridisation rather than multiple infection.

The use of in situ hybridization to show human papillomavirus deoxyribonucleic acid in metastatic cancer cells within lymph nodes

Southern blot hybridization has been used to identify human papillomavirus types in both primary tumors and lymph node metastases. However, this technique requires fresh-frozen tissue and is incapable of localizing deoxyribonucleic acid sequences to specific cell types in the tumor sample. In contrast, in situ hybridization precisely locates viral sequences within tumor cells while preserving cellular architecture. Further, in situ hybridization requires only small samples of formalin-fixed, paraffin-embedded tissues. Five lymph nodes (from four patients) containing metastatic cervical squamous tumor cells (identified with hematoxylin and eosinophil staining) were analyzed with in situ hybridization techniques with human papillomavirus type 16 deoxyribonucleic acid probes labeled with sulfur 35. The primary cervical cancer from all four patients had been shown to contain human papillomavirus type 16 sequences by Southern blot. Three specimens from two patients clearly showed the presence of human papillomavirus type 16 sequences within the nuclei of metastatic tumor cells, whereas two specimens were nondiagnostic most likely as a result of the small volume of cancer relative to the size of the lymph node. This information indicates that it is the tumor cells themselves that contain viral deoxyribonucleic acid and provides additional evidence linking human papillomavirus with cervical carcinogenesis.

In-situ hybridization for the diagnosis and typing of human papillomavirus

The human papillomavirus (HPV) has been associated with the production of many skin and mucosal lesions, the development of squamous cell carcinoma of the genital areas, skin and aerodigestive tracts, and possibly adenocarcinoma of the uterine cervix. There are more than 60 known genotypes of HPV. Some genotypes have been associated with lesions that have none or minimal chances of malignant transformation; while other genotypes (especially types 16, 18, 31, 35, and 51) have been found in mild, moderate, and severe dysplasia, carcinoma in-situ or frank invasive carcinoma. HPV cannot be propagated in tissue cultures. The presence of the virus can be demonstrated by immunologic techniques, which are not sensitive enough with the present methodology, or by searching for the presence of the viral DNA by DNA or RNA hybridization techniques. Determining the viral genotype in the tissue involved will permit the separation of those lesions supposedly to be low risk from those associated with the high risk types. This knowledge may be helpful in the future to determine the appropriate management of patients infected with HPV.

Basic concepts and practical applications of recombinant DNA techniques in detection of human papillomavirus (HPV) infection. Review article

Recent studies on the role of infectious agents in the pathogenesis of malignancy have demonstrated a strong association between HPV and several human benign and malignant epithelial neoplasms. There are 60 distinct types of HPV, of which HPV 16, 18, 31, 33, 35 and 39 have been associated with squamous cell neoplasia of the genital tract. Rapid progress in the field of recombinant DNA technology with the availability of specific probes has enabled the detection of HPV genomic sequences in characteristic HPV lesions. In addition, HPV sequences have been found in malignant squamous cell lesions, and even in normal tissues lacking the morphologic signs of HPV infection. Currently, hybridization analysis of the nucleic acid is the most reliable method for diagnosis of HPV infections, also permitting the genotyping of these viruses. A variety of hybridization procedures have been developed with different sensitivities and specificities. Despite the divergent technical modifications, however, all hybridization tests working according to the same basic principles. The double helix of DNA composed of two complementary polynucleotide chains can be opened by heating or by increasing pH. Cooling of the two strands allows reassociation. Labeled HPV DNA or RNA probe hybridizes with the complementary sequences allowing the detection of HPV sequences in the samples. Hybridization assays can be conducted under conditions in which virtually all HPVs will be detected, but not specifically typed (low stringency) or under conditions in which the type can be identified (high stringency). Widely divergent results have been reported both in prevalence of HPV infection and distribution of different HPV types in the genital tract. These discordant results have been explained on the basis of sampling effects, differences in histopathological diagnosis, geographical variations in HPV types and interlaboratory variation in HPV detection and typing techniques. In this review the various procedures for detecting HPV sequences by hybridization and related techniques are shortly described.

In situ hybridization analysis of HPV DNA in cervical precancer and cervical cancers from China

A series of 103 cervical biopsies derived from 103 women during July 1958 to September 1963 from Beijing, China were investigated with in situ hybridization for the presence of HPV6, 11, 16, 18, 31 and 33 DNA. The mean age of the patients was 46.1 + 10.6 years with a range of 24-74 years. Morphological features of HPV infection were found in 80 (77.7%) biopsies. Invasive cervical cancer was diagnosed in 43 biopsies and cervical intraepithelial neoplasia CIN I, CIN II and CIN III in 9, 9, and 27 cases, respectively. A total of 63.1% (65/103) of the lesions had morphological features of HPV infections associated with CIN or invasive carcinomas. Altogether, 31.1% (32/103) of the biopsies were shown to contain HPV DNA. Of the cases showing HPV morphology, 43.1% were HPV DNA positive. HPV16 (30/32) was the most frequent type, followed by HPV11 and 18, whereas no lesions with HPV6, 31 or 33 were found. A total of 19/43 (44.2%) of the invasive carcinomas contained HPV DNA. HPV DNA positivity and the grade of CIN showed a statistically significant correlation (P = 0.0011). Our study demonstrated the presence of HPV in cervical lesions among Chinese women in the late 1950's and early 1960's when a single sexual partner was the rule and also supports the concept that HPV has as an important etiological role in cervical cancer, the highest risk being associated with HPV type 16. The applicability of in situ hybridization in retrospective assessment is emphasized.

Human papillomaviruses and the pathogenesis of cervical neoplasia. A study by in situ hybridization

In a previous topographic study of cervical conization specimens, condylomatous changes were commonly present in direct contact with intraepithelial neoplasia and were always located distal (ectocervical side) to the neoplasia. Viral DNA was detected by in situ hybridization using 35S-labeled nick translated DNA probes in 50 of 70 cases (71%) which had adequate lesions: HPV-16 in 30, HPV-18 in ten, HPV-31 in six, and multiple types in four cases. HPV-6/11 was detected only once, in a multiple infection. As a rule, a positive cervix contained a single virus type, and the same virus type was found in condylomatous and neoplastic areas. The results suggest that the neoplastic process is initiated in the area of condyloma toward the endocervix and, once established, extends proximally toward the cervical canal. Capsid antigen was detected in 19 cases, indicating that a proportion of the high-grade lesions is potentially infectious.

Epidemiology of human papillomavirus (HPV) infections and their associations with genital squamous cell cancer. Review article

Reliable assessment of the epidemiology of genital HPV infections is hamphered by a number of technical problems. Because of the lack of tissue-culture systems, methods based on morphological approaches (colposcopy, cytology and histopathology) play a central role in HPV diagnosis. Even DNA-hybridization techniques and the recently introduced DNA amplification with PCR are extremely difficult to standardize, and are thus subject to major interlaboratory variation. Further confusion in the field is created by the complex biological behaviour of HPV infections. As established by the long-term prospective follow-up study of over 500 women which has been running in Kuopio since 1981, clinical progression and regression are significantly related to the grade of the lesion at the time of diagnosis (p less than 0.00001, and p = 0.0005, respectively), as well as to the type of HPV (p = 0.0012). Most importantly, however, genital HPV infections seem to run an extremely fluctuating course, passage from manifest to subclinical or latent infection being frequently encountered in individual patients when examined at 6-month intervals over prolonged periods. This explains the significantly divergent prevalence figures reported in different series (ranging from 2% to 80%), which are completely dependent on the technique used to analyse the presence of HPV, i.e. whether a) PAP smear, b) biopsy, c) DNA hybridization, or d) PCR amplification. The first two are capable of disclosing only manifest (clinical) infections, the latter two also the latent ones. In an unselected population of 22-year-old Finnish females, the prevalence of clinical HPV infections was about 3 per cent, and the adjusted annual incidence was 8.0 per cent. According to estimates of the life-time risk, up to 79% of Finnish females will contract at least one HPV infection between the ages 20 to 79 years. When related to the long-term trends in invasive cervical cancer in Finland, it is evident that this 79% life-time risk of becoming HPV-infected or even the observed 15% clinical progression rate for HPV infections in the prospective follow-up study by no means signifies an identical risk of developing cervical cancer (i.e. 0.79 x 0.15 = 11%). It seems likely that in countries where mass-screening programmes exist (and precancer lesions are traced), the high prevalence of HPV infections is not necessarily reflected as an increased prevalence of invasive cervical carcinomas. The distinction of lesions at risk for malignant transformation from those regressing spontaneously will have major implications in therapeutic considerations of genital HPV infections.

A comparison of methods for the detection of human papillomavirus DNA by in situ hybridization with biotinylated probes on human carcinoma cell lines. Application to wart sections

We compared nine different techniques for the detection of biotinylated DNA-DNA HPV hybrids on HeLa cells with 10-50 copies of HPV 18 DNA per cell. CaSki cells with 600 copies of HPV 16 DNA per cell and tissue sections from frozen or paraffin-embedded biopsy specimens. The cell samples were either cell deposits or cytocentrifuged or cultured slides. In most cases, the samples (cell deposits and tissue sections) were denatured with hybridization mixture prepared under stringent conditions (Tm = -17 degrees C) containing biotinylated DNA probes (cloned HPV types 1, 2, 6, 11, 16 and 18), at 90 degrees C for 10 min. In other cases (cytocentrifuged or cultured cells), the denaturation was performed by HCl hydrolysis and mild heating at 50 degrees C; the probes were denatured separately by heating. All the samples were further incubated overnight at 37 degrees C. For HPV DNA detection, three amplification levels were used on cell deposits. Only the techniques involving a three-step reaction (a rabbit anti-biotin antibody - a biotinylated goat anti-rabbit antibody - a complex of streptavidin-alkaline phosphatase or streptavidin-gold or streptavidin-fluorescein) gave satisfactory results, on both cell lines. With the one step reaction (an avidin-horseradish peroxidase, or streptavidin-alkaline phosphatase or streptavidin-fluorescein complex), no labeling of HeLa cells was observed with any of the HPV probes, including HPV 18. The techniques involving four steps (avidin or streptavidin - anti-avidin goat antibody or anti-streptavidin rabbit antibody - a biotinylated anti-goat (or anti-rabbit) antibody - a complex of avidin-biotin-peroxidase or streptavidin-biotin-alkaline phosphatase or streptavidin-biotin-horseradish peroxidase) resulted in high background on both cell lines. For the reproducible detection of low copy number of HPV DNA (less than 50 copies) such as occur in HeLa cells our data suggested that the three-step technique with the streptavidin-alkaline phosphatase complex was the method of choice. The most intense labeling was always obtained with cell deposits and the technique was successfully applied to frozen and paraffin-embedded tissue sections from typical warts.

In situ hybridization technique using an immunogold silver staining system

An in situ hybridization technique using an immunogold silver staining detection system was used to detect biotinylated DNA probes in cultured cells and in formalin-fixed paraffin-embedded tissue. The detection method is rapid, reliable and economical, producing an insoluble signal at the site of hybridization which is visible at low-power light microscopy and which can be enhanced by epipolarization microscopy.

Laryngeal papillomatosis: correlation between severity of disease and presence of HPV 6 and 11 detected by in situ DNA hybridisation

A technique using a biotin-streptavidin polyalkaline phosphatase complex was applied to routinely fixed and processed biopsy specimens of laryngeal papillomata from 45 patients taken over the past 20 years to detect human papilloma virus (HPV) types 6 and 11. Two thirds of both adult and juvenile onset cases were positive for HPV 6 or HPV 11 or both. Five specimens of normal vocal cord epithelium were negative for HPV 6 and 11. The detailed clinical history, endoscopic findings, success of treatment and eventual prognosis were compared with the HPV state of biopsy material for each patient. Patients with multiple confluent lesions when first seen, whose histology showed florid koilocytosis and who had strongly positive reactivity for HPV 6 or 11 present in the surface epithelial cell nuclei, had a poor prognosis requiring multiple endoscopies to control their disease.

Human papillomaviruses: are we ready to type?

The issue of determining which human papillomavirus (HPV) is present in a clinical specimen (typing specimens for HPVs) is receiving attention because HPVs cause condyloma acuminata and are associated with the continuum of disease which ranges from dysplasia to invasive genital cancer. Morphological inspection of precancerous lesions is not sufficient to determine which lesions will progress and which will not. A number of research tools based primarily on deoxyribonucleic acid hybridization have been developed. These permit identification and typing of HPV in genital tract scrapings or biopsies. Some HPV types (e.g., HPV-16 and HPV-18) have been identified in high-grade dysplasias and carcinomas more commonly than other types (e.g., HPV-6) and have been designated "high risk" types for cervical cancer. Thus, the question arises whether HPV typing would improve patient management by providing increased sensitivity for detection of patients at risk or by providing a prognostic indicator. In this review, the available typing methods are reviewed from the standpoint of their sensitivity, specificity, and ease of application to large-scale screening programs. Data implicating HPVs in the genesis of genital tract cancers are reviewed, as is the association of specific HPV types with specific outcomes. We conclude that there is currently no simple, inexpensive assay for HPV types, although such assays may be developed in the future. Analysis of the typing data indicates that, while HPV types can be designated high risk and low risk, these designations are not absolute and thus the low-risk group should not be ignored. In addition, interpretation of the data is complicated by finding high-risk types in individuals with no indication of disease. Insufficient data exist to indicate whether knowledge of the presence of a given HPV type is a better prognostic indicator than cytological or histological results. Thus, more research is needed before it can be determined whether typing information will augment the method currently in use for deciding treatment regimen and whether it warrants widespread use.

Comparison of human papillomavirus type 1 serotyping by monoclonal antibodies with genotyping by in situ hybridization of plantar warts

Thirty plantar warts were analyzed for the presence of HPV-1 type-specific and PV genus-specific capsid antigens by immunofluorescence (IF) using monoclonal and polyclonal antibodies and type-specific HPV-1 DNA employing in situ hybridization methods. Fifteen of 30 plantar warts were positive by IF for PV genus-specific structural viral antigens. Thirteen of the 15 productively infected plantar warts expressed intranuclear HPV-1 type-specific capsid antigens and viral DNA, which were detected in the same distribution in each individual wart. The 2 productively infected plantar warts that did not react with HPV-1 type-specific MoAbs did not react with HPV-1 type-specific DNA by in situ hybridization. Thus, serotyping of HPV-1 capsid antigens by monoclonal antibodies is concordant with genotyping of HPV-1 viral DNA by in situ hybridization in productively infected plantar warts.

Juvenile and adult laryngeal papillomata: classification by in-situ hybridization for human papillomavirus

We report the application of an in-situ hybridization technique for the demonstration of human papillomavirus (HPV) employing a biotin-streptavidin-polyalkaline phosphatase complex to paraffin processed tissue from a series of patients with laryngeal papillomata. All cases of juvenile papillomata, whether solitary or multiple, proved positive for HPV types 6 and/or type 11. However, only two cases of adult solitary papillomata and five cases of adult multiple papillomata were positive for HPV type 6 and/or type 11. All papillomata were negative for HPV types 16 and 18. Five specimens of normal vocal cord epithelium were uniformly negative for all four HPV types.

Study of multiple human papillomavirus-related lesions of the lower female genital tract by in situ hybridization

Twenty-six women with multiple human papillomavirus (HPV)-related lesions of the lower genital tract were investigated by immunohistochemistry for the internal genus-specific capsid antigen of HPV and by DNA-DNA in situ hybridization with 35S-radiolabeled probes for sequences of HPV-6/11, HPV-16, and HPV-18. The vulva was the most frequently affected site in all of these cases; the cervix was the second most frequently affected site. The lesions displayed the features of papillomavirus infection in 14 patients, and there was also histologic evidence of early neoplasia in 12 patients. The mean age of patients with and without neoplasia was 40 and 30 years, respectively. Evidence of HPV association was found in 73% of the vulvar lesions and in 40% of the other synchronous lesions by one or both methods. Viral DNA was found in 67% of patients with neoplasia and in 71% of patients without neoplasia. Eleven of 12 HPV-positive patients with neoplasia revealed the presence of HPV-16 in their tissues by in situ hybridization. On the other hand, 50% of those without neoplasia had HPV-16 DNA, whereas the presence of HPV-6/11 was found in the other 50%. The clinical course of the disease, the distribution of HPV type, and the type of antigen in patients with and without neoplasia suggest that progression to neoplasia was associated with HPV-16. These results stress the practical value of the in situ hybridization method for the identification of those patients with HPV infection who are at risk for progression to malignancy.

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.

Intraepithelial neoplasia, human papilloma virus infection and argyrophilic nucleoprotein in cervical epithelium

A silver colloid technique was applied to 50 colposcopic biopsies of cervix. These comprised nine cases of wart virus infection of the cervix, 11 cases of cervical intraepithelial neoplasia (CIN) I, nine cases of CIN II, eight cases of CIN III, seven normal biopsies and six cases showing only incomplete squamous metaplasia. The mean numbers of argyrophilic nucleolar organizer regions (AgNORS) increased from CIN I to CIN III. Statistically significant differences for AgNORs were found in comparisons between CIN III, normal basal cells, human papilloma virus-infected basal cells and incomplete squamous metaplasia, and in comparisons between normal basal cells and human papilloma virus-infected basal cells. CIN III could be distinguished from incomplete squamous metaplasia and from basal cells and from human papilloma virus-infected basal cells. The latter could be distinguished from normal basal cells on the basis of their AgNORs. It is suggested that this simple technique is diagnostically useful and has considerable clinicopathological potential in cervical pathology and cytology.

Morphologic and immunohistochemical evidence of human papillomavirus capsid antigen in smokeless tobacco keratoses from juveniles and adults

Seventy-seven tissue samples from patients with either degree I, II, or III smokeless tobacco keratoses were examined. The tissues were evaluated for the presence of human papillomavirus (HPV) antigen by immunocytochemical staining. Capsid antigen could be identified in sixteen cases (20.78%). This investigation further supports the concept that smokeless tobacco-associated leukoplakias can be correlated with HPV infection.

Factors associated with progression of cervical human papillomavirus (HPV) infections into carcinoma in situ during a long-term prospective follow-up

In the course of a prospective study of 508 women with papillomavirus (HPV) lesions of the uterine cervix, 66 lesions that progressed into carcinoma in situ (CIS) were identified and treated by conization during a mean follow-up period of 35 months. The lesions were investigated with light microscopy and with in-situ DNA hybridization using 35S-labelled probes for HPV 6, 11, 16, 18, 31 and 33. After radical cone treatment, 11 of the 66 women (16.7%) have presented with a recurrent HPV infection. The recurrence rate increased with the duration of the follow-up period from less than 10% at the mean follow-up of 25 months to 16.7% at the most recent follow-up at 35 months. Most of these 66 HPV lesions (89%) presented with concomitant CIN in the first punch biopsy, but it is noteworthy that the other 11% presented without concomitant CIN. HPV DNA of at least one of the six types examined was found in 73% of the first biopsies and it is noteworthy that the so-called 'low-risk' types, HPV 6 and 11, were found as frequently as the 'high-risk' types, HPV 16 and 18 (18% and 17%, respectively). This would suggest a similarity in the biological behaviour of these two HPV groups. Although the concept of the 'high-risk' and 'low-risk' HPV types may remain at least partially valid, it is imperative to realize that infection by HPV 6 and 11 by no means excludes the possibility for clinical progression into CIS and eventually to an invasive carcinoma.

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.

Synthetic oligonucleotide probes for the detection of human papilloma viruses by in situ hybridisation

Using the published nucleotide sequence data for human papilloma virus (HPV) types 1, 6 and 16, sequences of 30 bases in length from the beginning of the E6 open reading frame (ORF) were selected. Oligonucleotides were synthesised on an Oswel Gene Synthesizer and labelled at the 3' end with biotin using the enzyme terminal transferase. In situ hybridisation was carried out on paraffin sections of wart and cervical tissues mounted on silanated slides. A 2 h hybridisation step allowed the whole process to be completed within one working day. The technique successfully demonstrated the presence of HPV-1 in skin warts, and of HPV-6 and HPV-16 in genital warts and cervical lesions. This simple approach has diagnostic potential for the detection and typing of papilloma viruses in biopsy material.

Screening of premalignant cervical lesions for HPV 16 DNA by sandwich and in situ hybridization techniques

A series of 97 cervical smears and 69 directed punch biopsies derived from 84 consecutive women prospectively followed-up for cervical HPV (human papillomavirus) infections were studied using the sandwich hybridization and in situ hybridization techniques with HPV 16 DNA probes. The aim was to test the sensitivity and applicability of these two techniques in routine diagnosis of cervical HPV infections from smears. As a measure of specimen adequacy, the number of cells recovered in the cervical scrape was determined along with HPV 16 DNA in the sandwich hybridization test using human pro-alpha 2(I)-collagen gene probe. CIN (cervical intraepithelial neoplasia) was suggested in 56% of the patients by the Pap smear, and disclosed in 65% of the biopsies. HPV 16 DNA was present in 57% of cervical scrapes consistent with CIN, i.e., were of Pap smear classes III or IV. Forty percent of the scrapes not suggestive of CIN, i.e., Pap smear classes I or II, also contained HPV 16 DNA. The detection rate for HPV 16 DNA of the sandwich hybridization method was 89% of that of the in situ method in adequate scrapes, but only 43% in cell-poor specimens. The number of HPV 16 DNA-positive scrapes as compared with the total number of diagnoses obtained by studying also the biopsies was 31/36 (69 patients). The results indicate that the cervical scrape as a noninvasive specimen is applicable for screening of cervical HPV infections, and it can be studied with acceptable sensitivity by the rapid sandwich hybridization technique. However, if a punch biopsy is indicated it should be studied using the in situ hybridization technique that allows more sensitive detection of HPV DNA than any other hybridization method and enables the analysis of several HPV types in the same sample instead of only one HPV type in the scrapes.

Sensitivity of in situ hybridization techniques using biotin- and 35S-labeled human papillomavirus (HPV) DNA probes

In order to evaluate the sensitivity of our modified in situ DNA hybridization technique using biotinylated probes, formalin fixed, paraffin embedded biopsies from 20 cervical lesions known to contain human papillomavirus (HPV) DNA were re-examined by the technique using both 35S-labeled- and biotinylated HPV DNA probes. The probe concentrations as well as the detection limits of biotin probing were screened by spotting known amounts of HPV 16 DNA on nylon filter, and allowed to hybridize with biotinylated HPV 16 DNA probe. By this method, 4 pg of HPV 16 DNA could be detected using a probe concentration of 0.2 micrograms/ml. HPV DNA could be demonstrated in all 20 biopsies with both hybridization techniques. However, signals in subrabasal cells were detected more frequently with biotin- than with 35S-labeled probes. Additional experiments were performed using three cervical cancer cell lines (with known copy numbers of HPV DNA), to assess the detection limits of HPV infections by the in situ hybridization techniques. The CaSki cells (500-600 HPV 16 copies/cell) were unequivocally positive with both labelling systems. HeLa cells (10-50 HPV 18 copies/cell) were positive with the biotin probing in 10/10 smears, as compared to 7/10 smears when 35S-labeled probes were used. Radioactive probing was inferior to biotinylated probing in detecting the signals in SiHa cells (1-2 HPV 16 copies/cell). This is because even weak background signals could mask true positive signals when 35S-labeled probes are used. In contrast, no background is generated with the biotinylated probes, detected with streptavidin-biotinylated alkaline phosphatase complex. In situ hybridization with biotinylated DNA probes is as sensitive as techniques using 35S-labeled probes for detecting HPV infections in routine cervical biopsies or smears.

Advantage of human papillomavirus typing in the clinical evaluation of genitoanal warts. Experience with the in situ deoxyribonucleic acid hybridization technique applied on paraffin sections

Genitoanal warts are predominantly induced by human papillomavirus (HPV) types 6, 11, 16, and 18. A strong association has been established between infection by HPV 16 and HPV 18 and the subsequent development of cancer in the uterine cervix. Therefore, a clinical challenge exists with respect to identification of patients harboring the latter type of high-risk HPV types. The present study on 108 men with genitoanal warts focuses on whether reliable gross and/or histopathologic criteria exist to predict the presence of HPV 16 and HPV 18 or whether there is a need for HPV typing by deoxyribonucleic acid (DNA) hybridization assay in future epidemiologic studies. The high-risk HPV types were identified in 9 of 91 HPV DNA-positive lesions (11%). The gross appearance of the lesions appeared to be of limited predictive value for the presence of these HPV types. HPV 16 was most common in warts exhibiting some degree of dysplasia (p less than 0.001) and also occurred in the two lesions with a severe dysplasia. Lack of dysplasia correlated with the presence of HPV 6 and/or 11 (p less than 0.01). However, absence of dysplasia did not preclude infection with high-risk HPV types, and a mild to moderate dysplasia was associated with all of the four HPV types studied. Therefore, we emphasize the value of HPV typing in clinical routine in order to trace men harboring the high-risk HPV types 16 and/or 18.

Altered expression of filaggrin in human papillomavirus (HPV) lesions of the uterine cervix

A series of 64 punch biopsies collected from women prospectively followed-up for cervical Human papillomavirus (HPV) infections (with and without CIN), and 38 control biopsies (normal epithelia, and classical CIN) were analysed for expression of filaggrin (a histidine-rich protein constituent of keratohyalin granules) using the ABC technique and polyclonal antibody. HPV typing was completed using the in situ hybridization technique with DNA probes for HPV 6, 11, 16, 18 and 31. Three patterns of filaggrin distribution were differentiated: pattern I, all layers above the basal cells stained positive regularly; pattern II, all layers above the basal cells stained irregularly, and pattern III, scattered superficial cells stained positive. There was a significant difference between HPV-noCIN and HPV-CIN lesions in their filaggrin patterns, pattern I being present in the majority (77.7%) of HPV-noCIN lesions, as contrasted to HPV-CIN lesions, where pattern III was the predominant one (43.5%), followed by pattern II (32.6%). In HPV-CIN as well as in CIN lesions, pattern I was inversely related to the grade of CIN, being entirely absent in HPV-CIN III and CIN III. A significant difference exists between CIN and HPV-CIN lesions, concerning the presence of pattern III (4.3% and 43.5%, respectively, P less than 0.001). The difference was less dramatic with regard to pattern I (30.4% and 21.7%, respectively, P less than 0.05). In the lesions containing HPV 6, 11 or 31 DNA, filaggrin distribution was shown to be more close to that of the normal epithelium (I 36.7%, and II 34.7%), while in the HPV 16 and 18-infected cases, pattern III was the predominant one (46.7%). The assessment of filaggrin pattern in HPV lesions might be of help in evaluating the severity of the disturbance of keratinocyte differentiation induced by the progression of HPV infections.

Nucleic acid sandwich hybridization in detection of HPV 16 DNA: technique and its clinical application

Nucleic acid sandwich hybridization technique was used for detection of HPV 16 specific DNA in cervical scrapes. Alternating HPV 16-PstI fragments were cloned into plasmid pBR322 and phage M13mp10. pBR322-clones were used as 32P-labelled probe reagents and the M13mp10 clones as catching reagents in the assay. The detection limit of the test proved to be 1-5 X 10(5) HPV 16 molecules per test. A weak cross reaction was seen with HPV 31 DNA but not with the other types tested, e.g. HPV 6, 11, 18 and 33. Cervical scrapings obtained from 163 consecutive patients included in a prospective follow up study were analyzed for HPV 16 DNA with the sandwich hybridization method, dot-blot hybridization being used as a reference method. Sandwich hybridization assay detected 25 positive cases out of 163 specimens (15.3%). Of these 6 and 3 additional specimens were positive in dot-blot hybridization assay. HPV 16 DNA was related to higher PAP grades, and HPV 16 appeared more frequently in HPV CIN than HPV NCIN lesions. None of the infections caused by HPV 16 regressed, and 24% progressed during the follow up.

In situ DNA hybridization analysis of human papillomavirus (HPV) sequences in benign oral mucosal lesions

A series of 144 surgically treated benign oral mucosal lesions were analysed using an in situ DNA hybridization technique with 35S-labeled human papillomavirus (HPV) DNA probes to demonstrate the DNA of HPV types 6, 11, 13, and 16, in routinely processed, paraffin-embedded biopsy specimens. These lesions and an additional 62 benign oral mucosal biopsy specimens (total, 206 specimens) were also assessed by the indirect immunoperoxidase (IP-PAP) technique to detect the expression of HPV structural proteins (viral antigens). A total of 54/206 (26.2%) lesions were observed to express HPV antigens, being found in 45/92 (48.9%) of the squamous cell papillomas/condylomas, in 1/54 fibrous hyperplasias, in 1/8 true fibromas, and in 7/8 (87.5%) of the focal epithelial hyperplasia (FEH) lesions. Of the HPV DNA-positive lesions, 15/45 (33.3%) expressed HPV antigens, the expression not being related to any particular HPV type. HPV DNA sequences were found in 45/144 (31.3%) of the lesions. HPV DNA was present with the highest frequency in FEH (83.3%), followed by the papilloma/condyloma group (33.8%), papillary hyperplasia (28.6%), fibrous hyperplasia (24.4%), and true fibromas (14.3%). The most frequent HPV type was HPV 11, representing 37.8% of the DNA-positive lesions. HPV 13 DNA, previously regarded as specific to FEH, was disclosed as a single HPV type in seven cases, and as a double infection by HPV 11 and 13 in an additional three cases, including all five morphologically distinct entities. Noteworthy is the discovery of the high-risk HPV type 16 DNA in 17.8% of the DNA-positive lesions, four papilloma/condyloma lesions, three fibrous hyperplasias, and one FEH.(ABSTRACT TRUNCATED AT 250 WORDS)

Demonstration of human papillomavirus types 6 and 11 in juvenile laryngeal papillomatosis by in-situ DNA hybridization

A study is reported in which an in situ hybridization technique for the demonstration of human papillomavirus (HPV) employing a biotin--streptavidin polyalkaline phosphatase complex has been successfully applied to formalin-fixed paraffin-processed tissue obtained from ten patients with juvenile laryngeal papillomatosis. In all cases, positive results were obtained for either HPV type 6 or 11. Normal vocal cord epithelium was negative.

Cytologic and histologic manifestations of human papillomavirus infection of the female genital tract and their clinical significance

The historical developments in the recognition of the role of human papillomavirus (HPV) infection in cells and tissues of the female genital tract are briefly summarized. The identification of a specific marker cell, the koilocyte, has led to initial studies of frequency and biologic significance of neoplastic lesions of the uterine cervix associated with HPV. By molecular virology techniques, over 40 types of HPV have been identified and their tissue affinity determined. Types 6, 11, 16, 18, and 31 are most commonly associated with anogenital lesions, among them a broad spectrum of cervical intraepithelial neoplasia (CIN). While current evidence suggests that lesions associated with HPV Types 6 and 11 are potentially less harmful to the patient than lesions associated with HPV Types 16 and 18 (which have been identified also in invasive cervical carcinomas and cell lines derived therefrom), a major long term prospective study may be required to confirm this view. A factor that complicates the issue still further is the recent observation that HPV DNA of all four types has been identified in 11% of women and 5.5% of men free of disease. Infection with multiple viral types (including Types 16 and 18) was common in this apparently healthy population. Although HPV must be considered as a prime candidate for a transforming virus, current evidence suggests that the infection with the virus is per se an insufficient condition for the development of precancerous lesions or cancer of the uterine cervix and that another factor or factors may be necessary for these events to take place. Some of these possible cofactors such as age, repeated infections, and the immune status of the patient are discussed. A great deal of additional work is required before the precise role of HPV virus in the genesis of carcinoma of the uterine cervix, vulva, and vagina is firmly documented.

Detection of human papillomavirus (HPV) structural antigens and DNA types in inverted papillomas and squamous cell carcinomas of the nasal cavities and paranasal sinuses

To assess the suggested etiological role of human papillomavirus (HPV), biopsies from 14 patients operated on for an inverted papilloma (11 cases) and squamous cell carcinoma (3 cases) of the nasal cavity and paranasal sinuses were analysed for light microscopical evidence of HPV, by indirect immunoperoxidase (IP-PAP) to demonstrate HPV structural proteins, and using in situ DNA-hybridization to disclose the DNA of HPV types 6, 11 and 16. The majority of the inverted papillomas contained areas of metaplastic squamous cells, including koilocytes as well as dysplastic changes consistent with intra-epithelial neoplasia as described in uterine cervix. In 3 patients, frankly invasive squamous cell carcinomas were found, originating from dysplastic squamous epithelium. Of the 14 lesions, 7 (50%) expressed HPV antigens, usually confined to only a few cells close to the surface of the epithelium. None of the malignant lesions expressed HPV antigens. In situ DNA-hybridization disclosed HPV 11 DNA alone in 5 lesions, but none of the lesions contained HPV 6 DNA. HPV 16 DNA was found in 2 lesions as a single HPV type, and in 3 other lesions concomitant with HPV 11. All three carcinomas contained HPV 16 DNA. The HPV DNA distribution proved to be different from that found in the genital tract HPV lesions; HPV DNA was less abundant in the nasal papillomas, and it was also found in the basal and suprabasal cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of human papillomavirus types in male urethral condylomata acuminata by in situ hybridization

An in situ hybridization technique was applied under stringent conditions to paraffin sections of urethral condylomata from male patients to determine the presence of DNA sequences of human papillomavirus (HPV) types 6, 11, 16, and 18. The material consisted of 15 classical condylomata acuminata, two flat condylomata, and five recurrent lesions. HPV DNA sequences could be identified in all 15 condylomata acuminata; in 13 lesions, two types of viral DNA were observed (types 6 and 11 in 12, types 6 and 18 in one). In the remaining two condylomata acuminata, only HPV type 11 was present. One of the two flat condylomata was negative with all the probes, and one was borderline-positive for HPV 6. Four of five recurrent lesions contained the same types of viral DNA as the primary lesions, albeit with slight differences in the intensity of viral expression. One lesion was negative with all probes. We conclude that urethral condylomata in males contain the same types of HPV as seen in other anogenital lesions of both sexes and that infection with two viral types is common. In situ hybridization with HPV DNA probes is applicable to archival material and therefore may prove to be of value in future epidemiologic studies comparing lesions in sexual partners. The determination of viral type may have therapeutic implications.

Topographic study of cervical condyloma and intraepithelial neoplasia

In this study of 101 cervical conization specimens, the location and the size of condyloma and intraepithelial neoplasia (dysplasia and carcinoma in situ) were mapped using the last endocervical gland as the marker for the original squamocolumnar junction. Condylomatous changes were identified in 85% of cervices affected by the intraepithelial neoplasia, and were in direct contact with 68% of intraepithelial neoplasms. The proximal location of intraepithelial neoplasia in relation to the condyloma can be explained by the occurrence of neoplasia just proximal to the condyloma and subsequent expansion of neoplasia towards the cervical canal. This study adds topographic evidence linking cervical condyloma to the development of intraepithelial neoplasia.

Distribution pattern of human papilloma virus 16 genome in cervical neoplasia by molecular in situ hybridization of tissue sections

Using a highly sensitive method with single-stranded RNA probes, we analyzed the distribution pattern of HPV 16 DNA by in situ hybridization in CIN II (10 cases), CIN III (11 cases) and in invasive cervical carcinoma (17 cases). The technique used detected as little as 20-50 viral genomes per cell. This sensitive technique unmasked HPV 16 genomes in the basal cells of all forms of CIN. In CIN III viral genomes were present throughout the entire thickness of the epithelium. There was a striking difference in the distribution of viral DNA in CIN II compared with CIN III and invasive cancer. Variable viral genome distribution was observed in CIN II with the highest copy number in the area of epithelial differentiation. In contrast, CIN III showed a uniform distribution pattern of HPV genomes reflecting the lack of epithelial maturation. The majority of invasive carcinomas showed the same uniform distribution of the HPV 16 genomes as CIN III.

Demonstration of human papillomavirus types in paraffin processed tissue from human ano-genital lesions by in-situ DNA hybridisation

A sensitive in situ hybridization technique for the demonstration of human papillomavirus (HPV) employing a biotin-streptavidin polyalkaline phosphatase complex has been successfully applied to formalin-fixed, paraffin processed tissue obtained from a selected series of patients with ano-genital lesions. Benign condylomata from males and females showed the presence of HPV 6 and 11. Two cases of vulval intraepithelial neoplasia showed HPV 16. Four cases of squamous carcinoma of the anal canal also showed HPV 16 in the tumour or in the adjacent pre-invasive neoplastic epithelium. A case of malignant transformation in a cervical condyloma was associated with HPV 6 and 11. This technique permits the retrospective evaluation of routinely processed material thus widening the investigative spectrum for HPV.

Sensitive in situ hybridisation technique using biotin-streptavidin-polyalkaline phosphatase complex

A sensitive in situ hybridisation technique, using a biotin-streptavidin-polyalkaline phosphatase complex detection system, was successfully applied to smears of fresh cultured cells, frozen sections, and formalin fixed paraffin processed tissue: the procedure was successful for DNA-DNA hybridizations using a variety of DNA probes. The detection method is rapid, reliable, and economical producing a purplish-blue precipitate at the site of hybridisation and clearly visible by low power light microscopy.

In situ hybridization detection of human papillomavirus DNAs and messenger RNAs in genital condylomas and a cervical carcinoma

Routinely processed formalin-fixed paraffin-embedded sections from anogenital condyloma acuminatum and an invasive squamous cell carcinoma of the cervix were examined by in situ hybridization for the detection of human papillomavirus (HPV) DNAs and messenger RNAs. Asymmetric, single-stranded, tritium-labeled RNA probes for both the coding and the nonsense strands of HPVs 6, 11, 16, 18, and 31 were hybridized and washed under stringent conditions and detected by autoradiography. Type-specific HPV DNAs were detected with specific nuclear localization, while HPV messenger RNAs gave much higher signals and had clear-cut cytoplasmic localization. Cross-hybridization was observed only with closely related viruses. The level of signal obtained seemed to be linked to the degree of cellular differentiation, with koilocytotic cells labeling the most heavily. However, messenger RNA could be detected in even relatively undifferentiated cells within areas of dysplasia and invasive carcinoma. In situ hybridization is a sensitive and specific method for investigation of the dynamic interplay of papillomavirus replication and gene expression, cellular differentiation, and neoplastic transformation.

Detection of human papillomavirus DNA in oral mucosal lesions using in situ DNA-hybridization applied on paraffin sections

The in situ DNA hybridization technique, carried out under stringent conditions, was used to detect human papillomavirus (HPV) DNA of types 6, 11, and 16 in paraffin sections of 32 surgically treated oral mucosal lesions. Expression of HPV structural proteins was analyzed by means of the immunoperoxidase (IP-PAP) method. A total of 10 (31.3%) of the 32 lesions proved to express HPV antigens, which were found in 4 of 7 squamous cell papillomas, in 2 of 2 classic condylomas, in 2 of 10 papillary hyperplasias, and in 2 of 3 leukoplakia lesions. Two of the squamous cell papillomas contained HPV 6 DNA, and 4 additional lesions were positive for HPV 11 DNA. In one of the condylomas, a double infection by HPV 6 and 11 was found, while the second was positive for HPV 11 alone. Both the HPV antigen-positive papillary hyperplasias contained HPV 6 DNA, as did the HPV antigen-positive leukoplakia lesions. Of the latter, one was infected by HPV 6 and 11. DNA of the "high-risk" HPV 16 was contained in two lesions: one lichen planus lesion and one of the two squamous cell carcinomas. The results confirm the previously reported evidence of HPV involvement in oral mucosal lesions. The implications of these findings are discussed in terms of the well-established premalignant character of oral leukoplakia and oral lichen planus, although far less commonly versus leukoplakia, with special emphasis on the discovery of the "high-risk" HPV 16 in the latter as well as in oral cancer.(ABSTRACT TRUNCATED AT 250 WORDS)