Failure to detect human papillomavirus DNA in malignant epithelial neoplasms of conjunctiva by polymerase chain reaction

To elucidate the putative role of human papillomavirus (HPV) infection in the etiology of conjunctival tumors, 44 formalin-fixed, paraffin-embedded specimens of conjunctival tumors (24 patients with papillomas and 20 patients with dysplastic and/or malignant tumors) were screened for HPV infection using 4 different polymerase chain reactions (PCRs). Of the 24 samples of papilloma, 14 (58%) displayed positive results by applying nested PCR using primer sets of HPV consensus L1 region. HPV type 6 or 11 was detected in 9 cases of papilloma by type-specific primer sets, but none of them were positive for HPV type 16 or 18. However, by using the highly sensitive PCR technique, we failed to demonstrate the HPV DNA of HPV types 6, 11, 16, and 18 in any of the 20 malignant epithelial tumors of conjunctiva. We conclude that HPV-6 or HPV-11 is present in a substantial percentage of conjunctival papillomas, which is in accordance with findings of previously reported studies. In contrast, malignant conjunctival carcinomas are not associated with HPV infection; other pathogenic mechanisms, such as UV light, probably are more important in the cause of these malignant lesions.     

Detection of human papillomavirus type 6/11 DNA in conjunctival papillomas by in situ hybridization with radioactive probes

Twenty-three conjunctival papillomas and 28 conjunctival dysplasias were examined for human papillomavirus (HPV)-DNA sequences by in situ hybridization with nick-translated 35S-labeled HPV probes. Adjacent paraffin sections were hybridized with HPV type 2, 6, 16, and 18 probes at Tm - 17 degrees C. Fifteen tissues, all papillomas, displayed positive hybridization with the HPV-6 probe. Infection with HPV-6 (or the closely related HPV-11) appeared to be responsible for most of the conjunctival papillomas of children and young adults. The presence of genital tract HPV-6 in these lesions suggests that some of the infections were acquired during passage through an infected birth canal. The lack of hybridization in adult conjunctival dysplasias indicates either that HPVs are not associated with this condition or that the probes and the technique utilized were not adequate for demonstration of this association.     

Association of human papillomavirus with penile carcinoma: a study using polymerase chain reaction and in situ hybridization.

Although carcinoma of the uterine cervix has been shown to be strongly associated with human papillomavirus (HPV) infection, a sexually transmitted disease, similar detailed data are lacking in penile carcinoma. To determine the association of HPV with penile carcinoma, we examined 30 specimens of penile carcinoma from 23 patients by the highly sensitive polymerase chain reaction (PCR) and in situ hybridization assays. We also examined nonneoplastic penile foreskins from 20 adults using the polymerase chain reaction assay. Human papillomavirus type 16 genome was found in 15 patients (65%), HPV type 30 was found in three (13%), and HPV type 6/11 was found in two (9%). These HPV types were not detected in any of the nonneoplastic foreskins. As in cervical carcinoma, HPV, particularly type 16, is strongly associated with penile carcinoma and may play an etiologic role in the development of this neoplasm.     

Detection of human papillomavirus DNA in genital lesions by using a modified commercially available in situ hybridization assay.

A modified, commercially available DNA-DNA in situ hybridization test that uses biotinylated probes for the identification of human papillomavirus (HPV) DNA types 6/11, 16/18, and 31/33/35 was evaluated. HPV DNA was detected in 314 of 787 (40%) histologically abnormal genital biopsy specimens by using the ViraType in situ assay (Life Technologies, Gaithersburg, Md.), in which the hybridization time was increased from 2 to 16 h. Ninety percent of positive condyloma acuminata specimens contained HPV type 6/11 DNA. The prevalences of HPV DNA for cervical intraepithelial neoplasia I, II, and III lesions by this in situ hybridization test were 42, 54, and 55%, respectively. The combined prevalence of HPV type 16/18 and 31/33/35 DNAs increased with the severity of the lesion, while the prevalence of type 6/11 DNA decreased. HPV type 6/11 DNA was found only in 1 of 16 (6%) positive cervical intraepithelial neoplasia III specimens. HPV type 16/18 and 31/33/35 DNA was detected in 11 of 16 (69%) and 4 of 16 (25%) in situ hybridization-positive cervical intraepithelial neoplasia III specimens, respectively. Thus, the observation that certain "higher-risk" HPV genotypes are associated with upper-grade cervical precancer lesions was confirmed by this commercial hybridization system. In general, the assay was found to be well suited for use in the clinical laboratory. The ViraType in situ procedure modified for a longer hybridization time may be helpful in identifying lesions containing higher-risk HPV strains.     

Analysis of human papillomavirus types in exophytic condylomata acuminata by hybrid capture and Southern blot techniques.

Exophytic condylomata acuminata of the external genitalia of 40 patients were analyzed for human papillomavirus (HPV) DNA by the Southern blot and hybrid capture methods. All lesions were initially analyzed by the Southern blot method by using a mixture of HPV type 6, 11, 16, and 18 whole genomic probes. Southern blots demonstrated characteristic PstI restriction patterns of HPV type 6, 11, or 16 in all but one lesion. HPV 6 subtypes accounted for 28 of 39 HPV-positive lesions. Twenty-seven of these 28 lesions contained HPV type 6a, and 1 lesion contained HPV type 6c. Eight lesions contained HPV type 11 and three contained HPV type 16. Two of the three condylomata acuminata containing HPV type 16 were obtained from solid-organ transplant recipients receiving immunosuppressive medications. The third lesion containing HPV type 16 was a typical exophytic condyloma acuminatum from a woman with previously resected vulvar carcinoma. The hybrid capture assay detected HPV DNAs in all lesions except the Southern blot-negative lesion. Twenty-five lesions were positive for the A probe only (HPV types 6 and 11 and related types). All of these lesions were found to contain HPV type 6 or 11 sequences in the Southern blot assay. The remaining 14 lesions were positive for both the A probe and the B probe (HPV types 16 and 18 and related types). The strongest signal in these 14 lesions by the hybrid capture assay was consistent with the result of the Southern blot assay in all but one case. We conclude that (i) HPV type 6a is the most common type found in these lesions, (ii) HPV type 16 may be present more often in exophytic condylomata acuminata from immunosuppressed individuals, (iii) hybrid capture is a useful tool for documenting the presence of HPV sequences in DNAs from exophytic condylomata acuminata, and (iv) in samples containing multiple HPV types, hybrid capture allows detection of minority HPV types.     

Human papillomaviruses of different types in precancerous lesions of the uterine cervix: histologic, immunocytochemical and ultrastructural studies

In a prospective study of 34 women with abnormal Papanicolaou smears, biopsy and cervicovaginal lavage specimens were analyzed for the presence of human papillomaviruses (HPVs) by Southern blot analysis and probes for HPVs 6, 11, 16, and 18. In 22 of the 23 patients with cervical lesions (96%), HPV DNA was identified in one or more specimens. All patients in whom HPV DNA was found had either koilocytotic or dysplastic lesions on biopsy or Papanicolaou smear. Immunocytochemical demonstration of HPV in biopsy samples was associated with the presence of large amounts of HPV DNA and with the ultrastructural identification of viral particles. The presence of HPV DNA in cervical biopsy specimens was limited to discrete geographic areas of the cervix with histologic abnormalities. Although HPV 16 and other related HPV types were found in all cases of severe cervical intraepithelial neoplasia, the type of HPV present in a given specimen could not be predicted on the basis of morphologic, immunocytochemical, or electron microscopic findings. It is concluded that virtually all dysplastic lesions of the cervix contain HPV DNA, that HPV is thus likely to be a major etiologic agent in the pathogenesis of cervical dysplasia, and that histopathologic features are not predictive of HPV type.     

Detection of human papillomavirus types 6, 11, 16 and 18 in mucosal and cutaneous lesions by the multiplex polymerase chain reaction.

A multiplex polymerase chain reaction (PCR) based on the simultaneous amplification of human papillomavirus (HPV) types 6/11, 16 and 18 in a single-step procedure was developed, using primers chosen in the E6-E7 region. The specificity and sensitivity of this technique have been proved by amplifying mixtures or various amounts of plasmid-containing HPV DNA; it allowed the detection of as few as 5-25 HPV DNA copies. Application of the multiplex PCR to 71 clinical samples showed that HPV DNA was detected in 80% (45/57 cases) of mucosal biopsies and 35% (5/14 cases) of cutaneous specimens. HPV 16 was predominant in high-grade CIN whereas HPV 6 and 11 were detected more frequently in genital condylomas and laryngeal papillomas. In cutaneous Bowen's disease HPV 16, 18 or 6/11 + 16 were detected and in squamous cell carcinomas HPV 6/11 or 16 were found. After sequence amplification with primers of one HPV type, the clinical samples displayed the same HPV types but the frequency of positive and coinfected lesions increased. Thus, multiplex PCR is a valuable technique for typing HPV DNA but coinfections may be underestimated.     

Use of AffiProbe HPV test kit for detection of human papillomavirus DNA in genital scrapes.

The presence of human papillomavirus (HPV) DNA in cervical and vaginal scrapes was analyzed by the AffiProbe HPV test kit (Orion Corp., Orion Pharmaceutica, Helsinki, Finland), which is a 1-day solution hybridization test for HPV type 6/11, 16, or 18. The AffiProbe test was compared with a commercially available dot blot test (ViraPap and ViraType tests; Life Technologies Inc., Gaithersburg, Md.). The study group consisted of 178 patients seen in a gynecological outpatient clinic. Altogether, 64 specimens (36 cervical and 28 vaginal scrapes) from 49 patients were positive by the AffiProbe test. Concurrently collected cervical scrapes from 174 patients were available for the reference test, which yielded 27 positive results for HPV type 6/11 or 16/18 and 25 positive results for HPV type 31/33/35. Agreement as to the presence of HPV type 6/11, 16, or 18 by the two tests was reached in 85% of the specimens. Eleven cervical specimens were positive by the AffiProbe test only, and nine cervical specimens were positive by the ViraType test only. Independent evidence obtained by the polymerase chain reaction, repeat examination, or the concurrent presence of HPV DNA in vaginal or vulval epithelium supported the AffiProbe and the ViraType test results for 6 of the 11 and 6 of the 9 specimens with discrepant results, respectively. Thus, the DNA tests had similar sensitivities for HPV type 6/11, 16, and 18 DNAs, but the results were obtained within 1 day by the AffiProbe test, whereas results for the ViraPap and ViraType analyses required from 4 days to 2 weeks.     

The expression of P53 protein and infection of human papilloma virus in conjunctival and eyelid neoplasms

Human papilloma virus (HPV) infection and loss of P53 function have been identified as frequent events in various human tumors. The aim of this study was to evaluate P53 protein expression and to detect HPV in the tissue samples of 45 benign (papillomas) and 38 malignant conjunctival and eyelid lesions (27 basal cell carcinomas and 11 squamous cell carcinomas). We also looked for eventual relationships between P53 expression and clinicopathological features such as age, histological type of tumor, grading and staging. HPV infection was detected using the PCR-RFLP method. Specific primers were engaged and PCR products of HPV 16, 18, and 33, underwent enzymatic digestion at 37 degrees C. We revealed P53 protein expression in 30 out of 45 (66.6%) squamous cell papillomas. In the SCC and BCC groups, P53 was present in 31 out of 38 carcinomas and there was a statistically significant correlation between histological type of tumor and P53 protein expression. Malignant type HPV 16 and 18 were detected in three squamous cell papillomas, two BCCs and one SCC. However, we observed P53 protein expression in only two HPV-positive papillomas and one infiltrative type of BCC. P53 is probably involved in the development of conjunctival and eyelid tumors due to its high rate of presence in both benign and malignant neoplasms of these organs. HPV seems to occur rarely. In some cases its role in the pathogenesis of conjunctival and eyelid tumorigenesis should be considered as auxiliary.     

Human papillomavirus associated with oesophageal cancer

AIM: To study the prevalence and the different types of human papillomavirus (HPV) in patients with oesophageal cancer from a high risk area of South Africa (Transkei). METHODS: DNA samples from 50 paraffin wax embedded tissue sections were analysed by nested polymerase chain reaction (PCR) using the degenerate HPV L1 consensus primer pairs MY09/MY11 and GP5+/GP6+. Positive PCR samples were subjected to DNA sequence analysis. RESULTS: HPV DNA was detected in 23 of the 50 samples. Sequence analysis revealed that most patients (11) harboured DNA to HPV type 11, whereas other types included DNA HPV type 39 (seven patients), type 16 (two patients), and type 52 (one patient). HPV type 39 has not previously been shown to be associated with oesophageal cancer. In contrast to earlier studies that have found HPV type 16 to be more frequently associated with oesophageal cancer, HPV type 11 was the predominant subtype in this study. CONCLUSIONS: The high frequency of occurrence of HPV in oesophageal tumours (23 of 50 patients; 46%) implicates HPV as one of the possible aetiological factors in this disease. The finding that the low risk HPV subtypes predominate indicates that transformation may be effected via the E6 and E7 proteins.     

林州市地区食管癌活检组织中人乳头瘤病毒的研究

目的探讨在我国河南省林州市地区食管癌（esophageal carcinoma,EC）活检标本中人乳头瘤病毒（humanpapillomavirus,HPV）,特别是高危型HPV的感染状况。方法收集的食管癌活检标本,使用通用引物的套式PCR反应检测HPV的核酸,分别使用型特异性PCR检测HPV16和18的感染。结果18例活检标本全部为HPV阳性,其中HPV16的阳性率为13／18,HPV18的阳性率为4／18,HPV16／18的复合感染为4／18。结论我国河南省林州市地区食管癌活检组织中有HPV存在,其中HPV16的感染占很大比例,并且HPV感染可能是食管癌发生的重要病因。     

用聚合酶链反应检测结肠癌人乳头状瘤病毒基因

目的　应用聚合酶链反应,检测人乳头状瘤病毒(Humanpapillomavirus,HPV)基因与结肠癌及癌区周边组织的相关性。方法　将结肠镜检获取的72例活检标本进行病理检测,其中结肠癌46例,非癌26例(结肠癌周边组织标本10例),标本用蜡块包埋与固定液两种方法固定,用聚合酶链反应(PCR)特定DNA片段体外扩增法。结果　结、直肠癌人乳头状瘤毒基因检测阳性率434%,结、直肠癌周边组织阳性率10%,非癌组织阳性率为0%。结论　癌区组织基因(HPVs)检测率较高,与非癌对照组相比,差异有显著性(P<0.05),癌组织中HPVs主要以HPV1633型和HPV18型为主,统计学分析表明结、直肠癌的发生、发展与HPV感染有一定的相关性,尤以HPV16型关系更为密切。     

Detection of infection by human papillomavirus in genital condylomata. A comparison study using immunocytochemistry and in situ nucleic acid hybridization

One hundred eighty exophytic genital lesions clinically suspicious for infection by human papillomavirus (HPV) were analyzed by hematoxylin and eosin light microscopy, immunocytochemistry for HPV capsid antigen; and in situ nucleic acid hybridization for HPV messenger RNA (mRNA). Of 96 cases morphologically consistent with infection by HPV, 53% were antigen-positive, and 83% were mRNA positive (P less than 0.01). Of 55 cases suggestive but not diagnostic of HPV infection, 13% were antigen-positive and 26% were mRNA positive. Negative results were obtained in all lesions not believed to be indicative of HPV infection by morphologic criteria. In mRNA positive diagnostic cases, two thirds were of HPV type 6 and one third were HPV type 11. Two cases of coinfection with HPV types 6 and 16 were found. The study concludes that in situ hybridization for HPV mRNA is a more sensitive indicator of HPV infection, and in addition, provides HPV type, which may have prognostic significance.     

Detection of Human Papillomavirus Types 6 and 11 in Pubic and Perianal Hair from Patients with Genital Warts

Genital human papillomavirus (HPV) types 6 and 11 are of clinical importance due to their role in the development of anogenital warts. A pilot study was performed to investigate whether DNAs from HPV types 6 and 11 are present in hairs plucked from the pubic and perianal regions and eyebrows of patients with genital warts at present and patients with a recent history of genital warts. Genital HPV DNA was detected in 9 of 25 (36%) pubic hair samples and in 11 of 22 (50%) perianal hair samples by the CPI/CPIIg PCR. After sequencing of 17 of 20 samples, HPV type 6 or 11 was detected in 6 of 25 (24%) hair samples from the pubis and 8 of 22 (36%) hair samples from the perianal region. These types were not detected in plucked eyebrow hairs. In contrast, the HPV types associated with epidermodysplasia verruciformis were detected in similar proportions (62%) in both samples of pubic and eyebrow hairs. Moreover, HPV type 6 and 11 DNAs were detected in pubic hairs plucked from two patients who had been successfully treated and who did not show any lesion at the time of hair collection; this finding is an argument that HPV DNA may persist in this region. The presence of genital HPV types in plucked pubic and perianal hair suggests that there is an endogenous reservoir for HPV which may play a role in the recurrences of genital warts.     

Relationship between prevalent oral and cervical human papillomavirus infections in human immunodeficiency virus-positive and -negative women

Human papillomavirus (HPV) is an etiologic agent for both oropharyngeal and cervical cancers, yet little is known about the interrelationship between oral and cervical HPV infections. Therefore, we compared the prevalences and type distributions of oral and cervical HPV infections and evaluated infection concordance in a cross-sectional study within the Women's Interagency HIV Study cohort. Oral rinse and cervical-vaginal lavage samples were concurrently collected from a convenience sample of 172 human immunodeficiency virus (HIV)-positive and 86 HIV-negative women. HPV genomic DNA was detected by PGMY09/11 L1 consensus primer PCR and type specified by reverse line blot hybridization for 37 HPV types and beta-globin. Only 26 of the 35 HPV types found to infect the cervix were also found within the oral cavity, and the type distribution for oral HPV infections appeared distinct from that for cervical infections (P<0.001). Oral HPV infections were less common than cervical infections for both HIV-positive (25.2% versus 76.9%, P<0.001) and HIV-negative (9.0% versus 44.9%, P<0.001) women. Oral HPV infections were more common among women with a cervical HPV infection than those without a cervical HPV infection (25.5% versus 7.9%, P=0.002). The majority of women (207; 93.7%) did not have simultaneous oral and cervical infections by the same HPV type; however, the number of women who did (14; 6.3%) was significantly greater than would be expected by chance (P=0.0002). Therefore, the oral and cervical reservoirs for HPV infection are likely not entirely independent of one another.     

High frequency of human papillomavirus 6/11, 16, and 18 infections in precancerous lesions and squamous cell carcinoma of the conjunctiva in subtropical Tanzania

Dysplastic lesions and epithelial neoplasms of the conjunctiva account for approximately 2% of all malignant tumors in subtropical Tanzania. We examined the pathophysiologic role of human papillomavirus (HPV) in the development of conjunctival carcinoma in subtropical Tanzania, which has a high HPV prevalence. Tissue samples from 14 patients were obtained from the cancer registry archives at the medical center of the university in Dar es Salaam, Tanzania. A highly sensitive nonradioactive in situ hybridization technique (ImmunoMax) was applied to paraffin-embedded tissue samples to identify HPV DNA in conjunctival epithelial dysplasia and epithelial neoplasms. In each case, conventional morphologic evaluation revealed a transitional lesion extending from koilocytic dysplasia to severe dysplasia or invasive squamous cell carcinoma. Highly specific, morphologically easily distinguishable labeling of HPV-6/11, HPV-16, and HPV-18 was found in most cases. Coinfections were observed frequently. The signals showed varying intensities and different patterns of distribution. In general, higher signal intensity was found in dysplasia grades 1 and 2 and in well-differentiated areas of the invasive component of conjunctival carcinoma compared with less differentiated areas. This observation underlines the central role of HPV-16 and HPV-18 in the oncogenesis of conjunctival cancers in subtropical Tanzania.     

Absence of human papillomavirus DNA in nongenital seborrheic keratosis

Seborrheic keratosis (SK) is a benign epidermal tumor of unknown etiology. Because of its wart-like morphology, human papillomavirus (HPV) has been suggested as a possible causative agent. Viral involvement, however, has not been confirmed yet despite extensive research. The aim of this study was to evaluate the presence of HPV 6/11, 31, 33 DNA in nongenital SK. We analyzed 40 biopsy specimens taken from patients with nongenital SK using in situ polymerase chain reaction (PCR) and PCR with tissue extracts. The SK specimens (n=40), analyzed by in situ PCR, were negative for all HPV probes tested (types 6/11, 31, 33). Control slides (condyloma acuminatum, n=3) were positive for type 6/11, 31, and 33 HPV probes tested. Melasma samples (n=4), the negative controls, were consistently negative. No HPV DNA band was detected by PCR with the tissue extracts from paraffin-embedded SK samples, while condyloma acuminatum, the positive controls, showed DNA bands of the correct molecular weights. Our results show that HPV type 6/11, 31, and 33 cannot be recognized as causative agents for nongenital SK, which is in contrast to the previous studies. Further studies are required to reveal the presence of other types (more than 90) of HPV DNA.     

A high frequency of human papillomavirus DNA sequences in cervical carcinomas of Indian women as revealed by Southern blot hybridization and polymerase chain reaction.

Ninety-six colposcopically directed biopsies from squamous epithelial carcinoma of the uterine cervix and 22 age-matched normal control biopsy specimens were examined by both Southern blot hybridization and polymerase chain reaction (PCR) for the presence of different human papillomavirus (HPV) DNA types. Cancer of the uterine cervix, which is the most common malignant disease in Indian women, showed a high frequency (98%) of HPV as compared to those reported from other parts of the world. HPV type 16 was found to be the dominant (64%) type while the frequency of HPV type 18 was very low (3%). On individual typing of HPV, no biopsy was found to contain any other known HPV types under stringent conditions of hybridization except a single case of HPV type 11. Only one case of double infection with HPV types 16 and 18 was recorded. Under low stringency conditions of hybridization with a mixed probe of HPV types 16 and 18, 29 additional biopsies were found to be positive. Southern blot hybridization alone detected HPV DNA in 92% of the cases but none in the controls. By PCR, six (6.25%) more cases and four (18.18%) healthy women were found to be positive for HPVs. Analysis of the physical state of HPV 16 indicated integration in about 70% of carcinoma cases while 30% of them were in episomal form. The findings suggest that infection with HPV is an important etiologic factor for the development of cervical cancer, that a number of such tumours may arise without HPV infection, and that integration of the viral DNA into host genome is not always essential for malignant progression.(ABSTRACT TRUNCATED AT 250 WORDS)     

PCR detection of human papillomavirus: comparison between MY09/MY11 and GP5+/GP6+ primer systems.

Human papillomavirus (HPV) is an etiologic agent of cervical cancer and is the most common sexually transmitted disease in women. PCR amplification of HPV genomes is the most sensitive method for the detection of cervicovaginal HPV. We have compared the two most commonly used PCR primer sets, MY09/MY11 (MY-PCR) and GP5+/GP6+ (GP+-PCR), for the detection of HPV DNA in cervicovaginal lavage samples from 208 women. Oligonucleotide probes for 39 different HPV types were used. Both primer sets amplified a wide spectrum of HPV genotypes and detected similar overall prevalences of 45% (94 of 208) and 43% (89 of 208), respectively. The MY-PCR system detected 27 of 30 (90%) samples with multiple HPV types, whereas the GP+-PCR system detected 14 of 30 (47%) samples with multiple HPV types. Differences in the detection of HPV types 35, 53, and 61 were noted between the two primer systems. Serial dilution of plasmid templates indicated a 3-log decrease in the amplification of HPV type 35 by MY-PCR and HPV types 53 and 61 by GP+-PCR. These results indicate that although the MY-PCR and GP+-PCR identified nearly equivalent prevalences of HPV in a set of clinical samples, differences in the detection of specific types and infections with multiple types were found. Differences in the sensitivities and characteristics of the PCR systems for the detection of HPV within clinical samples should be considered when comparing data between studies and/or in designing new studies or clinical trials.     

Ultrastructural visualization of human papillomavirus DNA in verrucous and precancerous squamous lesions.

Human papillomavirus (HPV) DNA was ultrastructurally localized by the non-isotopic in situ hybridization technique in formalin-fixed, paraffin-embedded specimens of verruca vulgaris of the skin, condyloma acuminatum of the penis and severe dysplasia of the uterine cervix. Biotinylated DNA probe cocktails were employed for the visualization of HPV-DNA, types 6 and 11 (HPV 6/11) and types 16 and 18 (HPV 16/18). The papillomavirus genus-specific antigen was also visualized by pre-embedding immunoelectron microscopy using rabbit antiserum. In verruca vulgaris, HPV antigen-positive 50-60 nm-particles of mature viral size were observed in the nuclei of the granular cells and parakeratotic cells with perinuclear haloes, whereas HPV 6/11 and HPV 16/18 DNA were negative. In condyloma acuminatum, the nuclei were positive for the HPV antigen and HPV 6/11 DNA, but were negative for HPV 16/18 DNA. More cells were labeled for the viral DNA than for the viral antigen. The ultrastructural observation indicated the presence of the naked (plasmid) viral DNA as fine particles sized 15-20 nm. In the dysplastic cervical mucosa, dot-like positivity of HPV 16/18 DNA was recognized. The HPV antigen and HPV 6/11 DNA were undetectable. HPV 16/18 DNA was localized in part of the nuclear chromatin. This pattern of localization may suggest integration of the viral DNA into the host cell DNA.