Signal-amplified colorimetric in situ hybridization for assessment of human papillomavirus infection in cervical lesions.

Detection and typing of human papillomavirus (HPV) infection may have a major impact in cervical-screening and follow-up. In this study various commercially available techniques for the detection of HPV were evaluated. HPV-status was determined in 86 samples of cervical cancer by PCR and direct sequencing, catalyzed signal amplified colorimetric DNA in situ hybridization (CSAC- ISH) (GenPoint system, DAKO), immunohistochemistry (IHC) and in 12 selected cases also by conventional, non-amplified ISH. Twenty-one samples of cervical intraepithelial neoplasias grade III (CIN III) were investigated by CSAC-ISH, conventional ISH and by IHC, in corresponding PAP smears HPV-detection and typing was performed by CSAC-ISH and Hybrid Capture test II (HC). In additional 20 PAP smears HPV typing was performed using HC and a novel immunocytochemical system for HPV detection and-typing. CSAC-ISH showed good correlation with PCR analysis in cervical cancers: In 87% of PCR positive cases, HPV infection was also detected by CSAC- ISH (66/76). HPV 16 was detected in 75% of PCR-positive cases (44/59), HPV 18 in 71% of PCR positive cases (5/7). CSAC-ISH detected HPV 31 in only 29% of PCR positive cases (2/7), and HPV 33 in 64% of PCR-positive cases (23/36). Nevertheless, CSAC-ISH- false negative cases for HPV 31 or 33 were nearly always combined infections with other HPV types, which were detectable by CSAC-ISH in most cases. CSAC-ISH revealed HPV infection in 20 of 21 HC-positive cervical smears, while in corresponding biopsies (CIN III) CSAC-ISH detected 100% of HPV infections. Conventional, non-amplified ISH showed significantly lower sensitivity compared with CSAC-ISH, and immunocyto- and -histochemistry were of very low sensitivity for detection of HPV. CSAC-ISH is an easy-to-handle method for detection and typing of cervical HPV infection, and shows sufficient sensitivity for clinical practice.     

应用基因芯片诊断宫颈石蜡组织样本中人乳头状瘤病毒感染及其临床意义

目的探讨应用基因芯片检测宫颈石蜡组织标本中人乳头状瘤病毒（HPV）感染的可能性及其临床意义。方法收集解放军总医院诊断为宫颈鳞状上皮病变的石蜡组织标本40例,其中宫颈浸润性鳞癌18例,宫颈上皮内瘤变（CIN）Ⅲ12例,CINⅠ4例,CINⅡ6例。从组织中提取DNA后采用基因芯片检测23种常见HPV基因亚型,即PCR扩增后产物在基因芯片上进行杂交。同时选用10例经基因芯片检测16型和18型基因阳性的宫颈鳞癌的石蜡组织切片做原位杂交。基因芯片检测结果与部分原位杂交结果进行比较并分析。结果基因芯片检测的18例宫颈鳞癌HPV高危亚型均为阳性（100％）,其中1例为混合阳性;12例CINⅢ中11例为高危亚型阳性（91．7％）,1例阴性;6例CINⅡ的宫颈病变中高危型5例阳性,低危型1例阳性;4例CINⅠ中有2例低危型阳性、2例阴性;宫颈鳞癌和CINⅢ组与CINⅠ和Ⅱ组比较,差异有统计学意义（U=80．0,P〈0．01）。10例宫颈鳞癌基因芯片HPV16型和18型阳性组织中,原位杂交同型探针6例检测显示阳性。结论HPV基因芯片技术可用于检测多种亚型,特异性强,敏感性高,对HPV感染亚型的鉴别及宫颈癌的预防和治疗具有重要意义。     

Genital human papilloma virus infection in Oslo studied by dot blot DNA hybridization and the polymerase chain reaction.

Samples from patients with genital condyloma acuminata or with cervical condylomas and/or dysplasia and from women without cytological/clinical evidence of cervical affection were examined by dot blot DNA hybridization or the polymerase chain reaction (PCR). The PCR was much more sensitive than dot blot, more than doubling the human papilloma virus (HPV) findings. HPV DNA, mainly HPV 6/11, was detected in 18 of 19 biopsies of condyloma acuminata, whereas HPV 16 was most frequently detected in the 21 cervices (76%) with condyloma and/or dysplasia. HPV 16 was detected in eight of 103 cervical smears with no signs of infection. The prevalence of HPV 16 in cervical samples was somewhat higher than expected. This suggests that, in Oslo, HPV 16 is a common HPV type in women with cytologically normal cervices. HPV 18 was relatively rare and was detected only in combination with other HPVs.     

Detection of human papillomavirus in large cell neuroendocrine carcinoma of the uterine cervix: a study of 12 cases

AIM: To investigate the role of human papillomavirus (HPV) in large cell neuroendocrine carcinoma (LCNEC) of the uterine cervix. METHODS: Twelve archival, immunohistochemically and/or electron microscopically confirmed cases of cervical LCNEC were studied. Non-isotopic in situ hybridisation (NISH) was performed on the formalin fixed, paraffin wax embedded biopsies using digoxigenin labelled probes to HPV types 6, 11, 16, 18, 31, and 33. The tumours were then subjected to polymerase chain reaction (PCR) analysis using GP5+/GP6+ consensus primers to the HPV L1 gene, in addition to type specific primers to the E6 and E6/E7 genes. RESULTS: HPV-16 was detected by NISH and/or PCR in seven of the 12 carcinomas. Two additional tumours were HPV-18 positive by NISH and/or PCR. HPV DNA was not detected in the three remaining cases. CONCLUSION: Integration of high risk HPV, in particular type 16 and to a lesser extent type 18, is associated with this uncommon variant of cervical carcinoma.     

人乳头状瘤病毒感染与宫颈癌前病变的关系

目的 探讨人乳头状瘤毒（ＨＰＶ）感染与宫颈湿疣、癌前病变的相关性。方法 对１７９例宫颈细胞涂片异常患者行宫颈多点活检,病理形这观察,其中１２８例同时采用ＰＣＲ方法检测ＨＰＶ－ＤＮＡ,１０例行原位杂交分析。结果（１）形态学观察：宫颈湿疣多为扁平型（９７．３％）;除表现经典的诊断性控空细胞（３９．７％）外,国可见异型性明显的非典型性控空细胞（６０．３％）;宫颈湿疣常伴宫颈上皮内肿瘤（ＣＩＮ,４２．５％     

Occurrence of multiple types of human papillomavirus in genital tract lesions. Analysis by in situ hybridization and the polymerase chain reaction.

More than 22 types of human papillomavirus (HPV) have been detected in genital tract squamous cell intraepithelial lesions. Seven of two hundred eighty-six (2.4%) genital tract tissues in which HPV DNA was detected by in situ hybridization contained two or more different HPV types. When analyzed by site, 5 of 204 (2.4%) of cervical intraepithelial lesions were infected by more than one type, compared with 2 of 82 (2.4%) of vulvar lesions. The rate for low-grade lesions was similar (5/218; 2.3%) to that for high-grade lesions (2/68; 2.9%). In contrast, two different HPV types were detected in 6/33 (18%) of tissues by the polymerase chain reaction (PCR) using type-specific primers for eight HPV types. It is concluded that infection by one HPV type is rarely associated with concurrent 'active' infection by a second HPV type, even though DNA of a different viral type can be detected by PCR in about one fifth of such cases. Further study is required to determine if an existing HPV infection can inhibit replication by a different HPV type.     

Prevalence of human papillomavirus DNA in various histological subtypes of cervical adenocarcinoma: a population-based study.

The role of human papilloma virus (HPV) infection in the development of cervical carcinoma is well established, however, the prevalence of HPV DNA in cervical adenocarcinoma varies from study to study. It appears to be caused by a number of factors, one of which is that cervical adenocarcinomas comprise a heterogeneous group of multiple subtypes. To clarify the impact of HPV infection on the development of cervical adenocarcinoma with diverse histological subtypes, we performed a population-based study in Korean women from 15 different institutes for the status of HPV infection in adenocarcinoma of uterine cervix. A total of 432 cervical adenocarcinomas from 1997 to 2001 were reviewed and classified according to the modified WHO classification. For 135 cases, HPV typing was performed with HPV DNA chip (82 cases) and PCR HPV typing (53 cases), using formalin-fixed, paraffin-embedded archival tissue. The overall prevalence of HPV infection in cervical adenocarcinoma was 90%. The infection of HPV 16 and/or HPV 18 accounted for 78% of HPV-positive adenocarcinomas. Multiple HPV types were found in 13% of the cases. The HPV DNA was rarely detected in minimal deviation adenocarcinoma. Interestingly, HPV 16 was a predominant type in endometrioid and villoglandular types, whereas HPV 16 and HPV 18 were detected with equal prevalence in other subtypes. In conclusion, HPV infection, mostly HPV 16 and HPV 18, is highly associated with most of the cervical adenocarcinomas, whereas endometrioid and villoglandular type have a different pattern of HPV infection status. Minimal deviation adenocarcinoma does not seem to be related with HPV infection.     

Use of multiple PCR primer sets for optimal detection of human papillomavirus.

Using multiple PCR primer sets, we tried to optimize the detection of human papillomavirus (HPV) in DNA samples isolated from 361 frozen biopsy specimens from patients with invasive cervical carcinomas. The HPVs detected were placed into three distinct groups, including group I/Inex at Telelab (Skien, Norway) and group Ineg and group II at the Norwegian Radium Hospital (Oslo, Norway). The consensus primer sets were Oli-1b-oli-2i, My09-My11, Gp5-Gp6, and Gp(5+)-Gp6+ from the HPV L1 gene and CpI-CpIIG from the E1 gene. Using these consensus primers together with the type-specific primers from E6-E7, we found that 355 patients (98%) were HPV positive. Type-specific primers for HPV types 11, 16, 18, 31, 33, and 35 detected more HPV-infected patients than the most sensitive consensus primer set, while the three consensus primer sets My, Gp/Gp+, and Cp together detected more HPV-positive patients than the type-specific primers. Testing of sensitivity of the PCR with SiHa cells serially diluted in lymphocytes (HPV-negative cells) indicated a detection limit of 6,300 HPV type 16 DNA copies with consensus primers (My, Gp+, and Cp) and 126 original HPV type 16 DNA copies with type-specific primers. Comparison of the amplification results for consensus L1 primers and type-specific E6-E7 primers indicated the presence of L1 deletions in 23 of 56 samples. The conclusion is that in PCR detection systems, multiple consensus primers and type-specific primers should be used in order to detect all patients harboring HPV.     

High‐risk HPV types in lesions of the uterine cervix of female commercial sex workers in the Philippines

In order to prevent cervical cancer, vaccines against human papilloma virus types 16 (HPV‐16) and 18 (HPV‐18) have been implemented worldwide. However, the HPV types that cause cancer can differ according to geographical area and ethnicity. In this new era of the HPV vaccine, it is important to elucidate the prevalent HPV types in each area. Therefore, the prevalence of HPV infection and cervical abnormalities among 369 female commercial sex workers in the Philippines were examined. HPV L1 gene was amplified by polymerase chain reaction (PCR) using modified GP5+/6+ primers, and genotyping was performed by sequencing cloned PCR products. HPV DNA was detected in 211 (57.2%) women, among whom 46 HPV types were identified. HPV‐52 was most common and multiple‐type infection was observed in 44.5%. Among 56 women with abnormal cervical cytology (low‐ and high‐grade squamous intraepithelial lesions and adenocarcinoma in situ), HPV‐52 was most common (23.2%), followed by HPV‐16 (19.6%), ‐58 (10.7%), and ‐67 (10.7%). Only 27% of these women were positive for HPV‐16 and ‐18. Multivariate analysis revealed that HPV‐16, ‐39, ‐52, ‐67, and ‐82 were significantly associated with abnormal cytology. Repeated analysis of HPV‐52 single‐positive samples using the original GP5+/6+ PCR primers produced negative results in 57% of cases, suggesting that the prevalence of HPV‐52 infection may have been underestimated in previous studies, and the current vaccines may not be sufficient for preventing infection and the development of premalignant lesions of the cervix in women in the Philippines. J. Med. Virol. 81:545–551, 2009. © 2009 Wiley‐Liss, Inc.     

Infection with high‐risk HPV types among female sex workers in northern Vietnam

Vaccines against two high‐risk human papillomavirus (HPV) types, HPV‐16, and HPV‐18, are in use currently, with high efficacy for preventing infections with these HPV types and consequent cervical cancers. However, circulating HPV types can vary with geography and ethnicity. The aim of this study was to investigate the prevalence of HPV types and the association between HPV types and abnormal cervical cytology among female sex workers in Northern Vietnam. Cervical swabs and plasma samples were collected from 281 female sex workers at two health centers in Hanoi and Hai Phong in 2009. The HPV L1 gene was amplified by PCR using original and modified GP5⁺/6⁺ primers. Amplified PCR products were genotyped by the microarray system GeneSquare (KURABO) and/or clonal sequencing. Of the 281 women, 139 (49.5%) were positive for HPV DNA. Among the HPV‐positive samples, 339 strains and 29 different types were identified. Multiple‐type and high risk‐type HPV infections were found in 85 (61.2%) and 124 (89.2%) women, respectively. The most common genotype was HPV‐52, followed by HPV‐16, HPV‐18, and HPV‐58. Abnormal cervical cytology was detected in 3.2% (9/281) of the women, and all of these samples were positive for HPV‐DNA. Age ≤25 years and infection with human immunodeficiency virus were associated positively with HPV infection among the women while ever smoking was associated negatively. These results show that HPV‐52 is most prevalent among female sex workers in Northern Vietnam, most of whom had normal cervical cytology. This information may be important for designing vaccination strategies in Vietnam. J. Med. Virol. 85:288–294, 2013. © 2012 Wiley Periodicals, Inc.     

Human papillomavirus infection in non-neoplastic uterine cervical disease in Hong Kong.

The polymerase chain reaction (PCR) was used to detect and identify human papillomavirus (HPV) in 108 cases of formalin-fixed, paraffin-embedded, non-neoplastic uterine cervical biopsy tissue retrieved from the surgical pathology archives of the Department of Pathology, Caritas Medical Centre, Hong Kong. After DNA extraction, HPV L1 gene primers were used to detect the presence of HPV, and type-specific primers (to HPV types 6, 11, 16, 18, 31 and 33) were used to identify the specific HPV type on HPV L1-positive cases. PCR amplification of the beta-globin gene was used to ensure the quality of amplifiable DNA extracted. Of 94 cases that yielded sufficient good-quality DNA for PCR analysis, three (one endocervical polyp, one chronic inflammation with erosion, and a normal biopsy) had detectable HPV infection. Two of these had high-risk HPV type 16; the other had an uncommon HPV type. In view of the low incidence of HPV found in these patients, large-scale population screening of clinical samples using PCR to detect the presence of HPV and identify high-risk asymptomatic patients would not be cost-effective.     

Detection of specific types of human papillomavirus in cervical scrapes, anal scrapes, and anogenital biopsies by DNA hybridization

Specific varieties of human papillomavirus (HPV) infecting the anogenital region were detected in clinical samples by use of a filter hybridization technique suitable for rapid screening of cervical and anal scrapes. In this way possibly benign types (HPV6 and HPV11) could be differentiated from types thought to be capable of malignant transformation (HPV 16 and HPV 18). Cervical or anal canal cells were applied directly to nylon filters and fixed by u.v. irradiation before hybridization with mixed viral DNA probes under both low- and high-stringency conditions. In addition, probe for the human Alu-repeated DNA sequence was used to assess the relative amount of total nucleic acids in each sample applied to the filter. HPV DNA was detected in 3 of 19 cervical scrapes from patients with no past or present history of wart virus infection or cervical dysplasia. Within a positive study group totalling 71 patients, HPV (6/11 or 16/18) was detected in cervical scrapes from 24% of 41 patients who did not have visible genital dysplasia, 30% of 27 patients with visible genital dysplasia or cervical intraepithelial neoplasia (CIN) I, and in 1 of 3 patients with past CIN II/III. In addition, HPV6/11 or 16/18 DNA was detected in anal scrapes from 3 of 6 male patients and in 85% of genital biopsies. A notably high proportion (4/6) of vaginal condylomata were positive with both the HPV6/11 and the HPV16/18 mixed viral DNA probes. Of the biopsies prepared for histopathology and positive for HPV DNA, the HPV group-specific antigen could be detected in only 60%.     

Association of HPV infection with prognosis after neoadjuvant chemotherapy in advanced uterine cervical cancer

Whether the human papillomavirus (HPV) status of the tumor affects the sensitivity to neoadjuvant chemotherapy, and the prognosis in advanced uterine cervical cancer (FIGO stage III or higher) remains unknown. We examined the HPV status of 43 patients who had received CDDP therapy by balloon-occluded arterial infusion (BOAI), as neoadjuvant chemotherapy for advanced uterine cervical cancer (squamous cell carcinoma) stage III or higher. DNA was extracted from formalin-fixed, paraffin-embedded tumor samples obtained by punch biopsy before the neoadjuvant chemotherapy. The detection of HPV and its typing were analyzed by a polymerase chain reaction (PCR)-based assay using consensus primers for the L1 consensus regions. HPV DNA was detected in all 43 patients (100%): 29 cases with HPV 16 (67.4%), 5 cases with HPV 33 (11.6%), 4 cases with HPV 31 (9.3%), 3 cases with HPV 35 (7.0%), 1 case with HPV 18 (2.3%) and 1 case with HPV 58 (2.3%). The HPV types were divided into 3 groups, HPV 16, HPV 33 and other HPV types (HPV 18, 31, 35, 58), and comparisons and examinations were performed among the 3 groups. Although the rates of tumor reduction and operation accomplishment after 3 courses of BOAI showed no significant differences among the 3 groups, there were significant differences in the survival rates. The survival rate of advanced uterine cervical cancer patients with HPV 33 infection was the highest, followed by that of patients with HPV 16 infection. The survival rates of patients with the other types of HPV infection were the worst among the 3 groups and significantly lower than those of patients with HPV 16 or HPV 33 infection. The differences in the curative effect after BOAI may depend on the different characters of the HPV types.     

北京地区人乳头瘤病毒16型感染及其E6/E7基因变异与宫颈病变的相关性研究

目的探讨HPV16感染及其E6/E7基因变异与宫颈病变的相关性。方法采用导流杂交技术进行HPV感染分型检测,PCR扩增出80份HPV16阳性宫颈病变的E6/E7基因、克隆入pMD18-T载体,双向测序分析基因变异与宫颈病变相关性。结果HPV16在宫颈病变患者中的检出率最高为33.3%(154/463),与病变程度相关(P<0.05)。E6/E7基因72份测序成功,DNA序列变异发生率为88.9%(64/72)。氨基酸序列E6-D32E(T96G)和E7-N29S(A86G)位点突变同时伴随存在,D32E/N29S的检出率为38.9%(28/72),与宫颈病变程度相关(P<0.05)。结论HPV16是北京地区来源的宫颈病变中最常见的致病型,其D32E/N29S变异与病变程度相关。     

Human papillomavirus infection and invasive cervical neoplasia: a study of prevalence and morphology

The prevalence of human papillomavirus (HPV) DNA sequences in 45 cervical cancer biopsies was examined with the hot-start polymerase chain reaction (PCR), employing HPV consensus primers from the L1 region. The cases comprised 38 squamous cell carcinomas, three adenosquamous carcinomas, and four adenocarcinomas. PCR products were typed with single-strand conformation polymorphism (SSCP) and the HPV types detected were correlated with tumour type. Forty-three biopsies were HPV-positive, HPV16 being the most prevalent type. HPV18/33/45/58 were also detected, but no low-risk or multiple types. Keratinizing squamous cell carcinoma was invariably associated with HPV16 and adenosquamous carcinoma and adenocarcinoma with HPVs 18/45. Non-keratinizing squamous cell carcinomas harboured all five detected types. Our data corroborate the view that malignant cervical tumours are almost invariably associated with high-risk HPV and that certain malignant cervical tumour phenotypes correlate with specific HPV types. © 1997 John Wiley & Sons, Ltd.     

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.     

人乳头瘤病毒16型转换基因的序列分析

为了解中国地区宫颈癌病人中人乳头瘤病毒１６型Ｅ６Ｅ７基因结构特点,从中国山东地区宫颈癌活检组织中提取组织ＤＮＡ,经ＨＰＶ多重引物ＰＣＲ法鉴定标本中感染ＨＰＶ型别,选单纯感染ＨＰＶ１６两例标本ＤＮＡ为模板进行ＰＣＲ扩增,获得ＨＰＶ１６Ｅ６Ｅ７基因后,重组入ｐＡＬＴＥＲ－１载体,进行双向测序、分析。ＤＮＡ序列分析表明：两例标本的ＨＰＶ１６Ｅ６Ｅ７序列全长均为７７６ｂｐ,与已发表的德国标准株长度相等,两     

机会性筛查人群中高危型人乳头瘤病毒与宫颈病变相关性的分析

目的研究第二代杂交捕获法（HC2）高危型人乳头瘤病毒（HR—HPV）检测阳性样品中HPV与宫颈病变的相关性。方法随机抽取HC2阳性患者602名（344名行细胞学检查）,采用PCR一反向点杂交（RDB）法对HPV分型并分析HPV型别与细胞学的相关性。结果602例患者PCR阳性率94．5％;HPV分型检出率依次为HPVl6、52、58、56、39等;HC2检测谱外单独感染24例;HPVl6、HPVl6／18与ASCUS、LSIL、HSIL有明显相关性。结论机会性筛查人群中最常见HPV型别依次为HPVl6、52、58;HC2检测的假阳性率为4．0％;HPVl6与宫颈病变程度相关。     

机会性筛查人群中高危型人乳头瘤病毒与宫颈病变相关性的分析

目的 研究第二代杂交捕获法(HC2)高危型人乳头瘤病毒(HR-HPV)检测阳性样品中HPV与宫颈病变的相关性.方法 随机抽取HC2阳性患者602名(344名行细胞学检查),采用PCR-反向点杂交(RDB)法对HPV分型并分析HPV型别与细胞学的相关性.结果 602例患者PCR阳性率94.5%;HPV分型检出率依次为HPV16、52、58、56、39等;HC2检测谱外单独感染24例;HPV16、HPV16/18与ASCUS、LSIL、HSIL有明显相关性.结论 机会性筛查人群中最常见HPV型别依次为HPV16、52、58;HC2检测的假阳性率为4.0%;HPV16与宫颈病变程度相关.     

Human papillomavirus infection and anal carcinoma. Retrospective analysis by in situ hybridization and the polymerase chain reaction.

To examine the association of human papillomavirus (HPV) infection with anal squamous cell carcinoma, the authors applied the highly sensitive polymerase chain reaction (PCR) and in situ hybridization (ISH) techniques to detect HPV DNA in formalin-fixed, paraffin-embedded tissues from 18 patients. The presence of HPV types 16/18 in 3 (16.7%) of 18 patients with anal carcinoma was found, using a colorimetric ISH technique for HPV types 6, 11, 16, 18, 31, 35, and 51. Results from one of these three patients were also positive for HPV 31, 35, 51 by ISH techniques. When the same series was analyzed using the PCR and consensus primers to the L1 open reading frame of the HPV genomes, the frequency of positive patients rose to 14 (77.8%) of 18. PCR analysis of the 14 lesions containing HPV DNA, using type-specific primers and probes for HPV 6, 11, 16, 18, and 33, showed that 1 contained HPV 6, 1 contained HPV 11, 4 contained HPV 16, 1 contained HPV 18, 1 contained HPV 33, 5 contained HPV of unclassified type(s), and 1 contained a mixture of three HPV types. There was concordance between typing of cases that were positive by ISH and PCR methods. These data agree with the concept that HPV, in particular type 16, is implicated in the pathogenesis of anal cancer.