Automated polymerase chain reaction for papillomavirus screening of cervicovaginal lavages: comparison with dot-blot hybridization in a sexually transmitted diseases clinic population

The advent of human papillomavirus detection for cervical screening

PURPOSE OF REVIEW

This review updates progress in the human papillomavirus (HPV)-based revolution in cervical screening and vaccination predicted to eventually eliminate cervical cancer.

RECENT FINDINGS

HPV PCR, patented by the author in 1987, has recently begun to replace cytology for primary cervical screening. I highlight the findings from large randomized clinical trials that have brought about this change, and progress with implementation. Australia was the first to introduce a national, publicly-funded HPV PCR-based program of primary screening, on 1 December 2017. The United Kingdom is set to follow, as are other countries. The widespread preference of self-sampling by under-screened women in particular will increase the effectiveness of population screening when using HPV tests. Coupled with improved vaccination now that more effective (nonavalent) HPV vaccines are being introduced, recent modeling predicts that cervical cancer will be markedly reduced, or even eliminated, in coming decades.

SUMMARY

The recent or pending change to more accurate cervical screening by HPV detection using PCR in various countries means less frequent screening for women. Women with an aversion to having their sample collected by a physician can collect their sample themselves, either at the doctor's rooms or at home, the sample then being mailed to the testing laboratory.

Age-specific prevalence of infection with human papillomavirus in females: a global review

PURPOSE

Global data on age-specific prevalence of human papillomavirus (HPV) infection overall, and for high-risk HPV types 16 and 18, are essential for the future implementation of HPV prophylactic vaccines for cervical cancer prevention.

METHODS

A systematic review of peer-reviewed publications was conducted to summarize worldwide data on genital HPV-DNA prevalence in women. Studies with clear descriptions of polymerase chain reaction or hybrid capture detection assays were included.

RESULTS

A total of 346,160 women were included in 375 studies. Of 134 studies with age-stratified HPV prevalence data (116 low sexual risk populations, 18 high sexual risk populations), over 50% were from Europe and the Middle East (38%) and North America (19%), with smaller proportions from Asia and Australia (21%), Central and South America (11%), and Africa (10%). Across all geographical regions, data on HPV prevalence were generally limited to women over 18 years of age. Consistently across studies, HPV infection prevalence decreased with increasing age from a peak prevalence in younger women (< or =25 years of age). In middle-aged women (35-50 years), maximum HPV prevalence differed across geographical regions: Africa (approximately 20%), Asia/Australia (approximately 15%), Central and South America (approximately 20%), North America (approximately 20%), Southern Europe/Middle East (approximately 15%), and Northern Europe (approximately 15%). Inconsistent trends in HPV prevalence by age were noted in older women, with a decrease or plateau of HPV prevalence in older ages in most studies, whereas others showed an increase of HPV prevalence in older ages. Similar trends of HPV 16 and/or 18 prevalence by age were noted among 12 populations with available data.

DISCUSSION

Genital HPV infection in women is predominantly acquired in adolescence, and peak prevalence in middle-aged women appears to differ across geographical regions. Worldwide variations in HPV prevalence across age appear to largely reflect differences in sexual behavior across geographical regions. Further studies of HPV prevalence in adolescents are needed for all geographic regions.

Cervical screening in the 21st century: the case for human papillomavirus testing of self-collected specimens

Cervical screening by Pap smear involves a high rate of false negatives, necessitating frequent testing. Because women do not like the sampling procedure, many avoid being screened. Testing for the causative high-risk human papillomavirus (HPV) types, by PCR or other technologies, on self-collected (tampon) samples permits women to be monitored non-invasively. The high negative predictive value of HPV testing means a greater interval between tests, and thus reduces costs. HPV testing lends itself to primary screening. A kit for self-collection and return to a testing laboratory, followed by practitioner notification and follow-up if required, should result in wider participation. The higher accuracy of HPV testing should lead to improved cervical cancer prevention.

Cervical human papillomavirus screening by PCR: advantages of targeting the E6/E7 region

PCR is a promising method for detection of human papillomavirus (HPV), the high-risk forms of which are responsible for cervical cancer. PCR primers that target the L1 or E1 region can be unreliable and may miss more advanced disease, whereas those directed at the E6 or E7 regions, which encode oncogenic products, are preferable because 1) the LI/E1 regions, but never the E6/E7 regions, are lost during integration of viral DNA into host genomic DNA, a process that can represent an integral component of progression from infection to tumorigenesis; and 2) the E6/E7 nucleotide sequence exhibits less nucleotide variation. The choice of region used for PCR has implications for HPV screening strategies in the clinical diagnosis and management of cervical cancer.

Detection and genotyping of human papillomavirus DNA by SPF10 and MY09/11 primers in cervical cells taken from women attending a colposcopy clinic

Human papillomavirus (HPV) is the main etiological agent of cervical cancer. There is a large number of HPV genotypes and therefore a need to distinguish the high risk HPV genotypes associated with invasive cancer from the low risk. Because persistence of high risk HPV infection is necessary for progression of a pre-invasive cervical change one needs to identify the individual genotype to see if it persists. PCR amplification of HPV DNA is described using two consensus primer systems from cervical cells. Amplified HPV DNA was genotyped using a reverse hybridization line probe assay (LiPA). HPV DNA was amplified from 42% of samples by MY09/11 and from 80% by SPF10. In 42 samples HPV DNA was detected by both primer sets and in 38 samples only the SPF10 primers detected HPV DNA. The LiPA detected 21 different HPV genotypes (13 high risk) in this cohort of samples. Forty-three percent contained a single HPV genotype and 24% contained multiple infections (2-5 genotypes). Overall, high risk HPV genotypes were detected in 48% of the cervical samples, the most frequent types were 16, 18, 31, and 51. The proportion of high risk HPV genotypes increased with more severe cytological abnormalities. This study demonstrates that the SPF10 primer set is more sensitive than the MY09/11 primer set and that genotyping by LiPA tells us if the HPV infection is caused by a high risk type and if the infection is mixed. Additionally LiPA provides information about the individual genotype when looking for persistence of infection. HPV DNA detection and genotyping is therefore a useful tool in the colposcopy clinic, used in conjunction with cytology.

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.

Analytic sensitivities of hybrid-capture, consensus and type-specific polymerase chain reactions for the detection of human papillomavirus type 16 DNA

Human papillomavirus type 16 (HPV-16) DNA is detected commonly in cervical carcinomas; in this study, we have determined the analytical sensitivities of Hybrid Capture, HPV-consensus PCR, and three HPV-16-specific polymerase chain reactions (PCRs) for the detection of HPV-16 DNA. Samples investigated included a cervical cancer cell line, cervical scrapes from 20 patients attending colposcopy clinics, and buccal swabs from eight immunosuppressed children. HPV-16 E7 and E5-nested PCRs [Cavuslu et al. (1996): Journal of Virological Methods, in press] produced positive signals from samples containing fewer than ten HPV-16 genomes per reaction. HPV-consensus PCR [Manos et al. (1989): Cancer Cells 7:209-214] and HPV-16 PCR using primers of van den Brule et al. [(1990): Journal of Clinical Microbiology 25:2739-2743] were of intermediate sensitivity (i.e., produced positive signals from samples containing 250 and 2,500 HPV-16 genoms/reaction, respectively) and Hybrid Capture could detect just 50,000 HPV-16 genomes/reaction. Highest rates of positivity for cervical samples were detected with HPV-16 E7 or E5-nested PCRs [50% (10 of 20 samples) and 60% (12 of 20 samples) positive, respectively], intermediate rates with HPV-consensus PCR and PCRs using the primers of van den Brule et al. [both 35% (7 of 20 samples)], and lowest rates of positivity [25% (5 of 20 samples)] with Hybrid Capture. None of eight buccal swab samples from immunosuppressed children were positive by Hybrid Capture, yet three (37.5%) were positive by HPV-16 E5-nested PCR. These data indicate that HPV-16 type-specific PCRs should be used for the investigation of specimens that may contain low amounts of HPV-16 DNA.

Simple microwave and thermal cycler boiling methods for preparation of cervicovaginal lavage cell samples prior to PCR for human papillomavirus detection

Sample preparation is an important step in the detection of viral DNA by the polymerase chain reaction (PCR) technique. The method used should achieve release of cellular DNA with the minimum of manipulation steps so as to reduce the possibility of contamination. The present report demonstrates that either microwaving or 20 min of boiling in the heating block of a thermal cycler lead to satisfactory results in the detection by PCR of human papillomavirus in cervicovaginal epithelial cell specimens obtained by lavage. Since each of these methods uses only one step the possibility of contamination is greatly reduced compared to the widely used proteins K/nonionic detergent extraction procedure.

Comparison of dot filter hybridization, Southern transfer hybridization, and polymerase chain reaction amplification for diagnosis of anal human papillomavirus infection

The detection and classification of human papillomavirus (HPV) by a consensus primer polymerase chain reaction (PCR) technique were compared with detection and classification by dot filter hybridization (DFH) and Southern transfer hybridization (STH). PCR detected HPV in 87% of specimens; the detection rates for DFH and STH were 51% and 49%, respectively. The specific HPV types detected by STH were also detected by PCR in 90% of specimens. However, 75% of the samples positive for unclassified HPV by STH were typed by PCR. PCR results were reproducible, as assessed by repeat analysis (96% agreement), by analysis of paired same-day specimens (89% agreement), and by interlaboratory analysis (88% agreement). PCR is a sensitive, specific, and reproducible test for HPV detection and classification in clinical and epidemiologic studies.

Typing of human papillomavirus DNAs by restriction endonuclease mapping of the PCR products

The polymerase chain reaction (PCR) for the diagnosis of human papillomavirus (HPV) infections, and in particular for the study of cervical HPV-associated lesions, is used widely. We identified a novel set of universal primers that are able to amplify a fragment spanning the E1 open reading frame (ORF) from different mucosotropic HPV types. A restriction endonuclease digestion of the amplified products is suggested for accurate typing. In particular, AluI digestion of the amplified fragments yields a distinctive fragment pattern for each 'high-risk' (16, 18, 31 and 33) HPV sequence, thus distinguishing them from 'low-risk' (6b and 11) HPV sequences.

Implications of rDNA technology in the microbiology laboratory

The present and potential future roles in service and research microbiological laboratories of recombinant DNA (rDNA) techniques (nucleic acid hybridization, nucleic acid amplification, in situ hybridization, pulsed field gel electrophoresis) are described. Applications rDNA technology include the detection of micro-organisms; an approach to the understanding of their role in disease pathogenesis and provision of alternative strategies for studying the epidemiology of infectious diseases.

Prevalence of human papillomavirus (HPV) infection in Basque Country women using slot-blot hybridization: a survey of women at low risk of developing cervical cancer

Cervical smears from 1,178 women with cytologically normal cervices and 67 women with cervical intra-epithelial neoplasia (CIN) or cervical carcinoma were analyzed for the presence of HPV 6, 11, 16 and 18 DNA by slot-blot hybridization. HPV DNA was detected in 17% (95% CI: 14%-19%) of the women with a normal smear; 11% of infected women harboured HPV 16 and 18 (95% CI: 9%-13%, each). HPV DNA was detected in 54% (95% CI: 41%-66%) of patients with abnormal smear; the most prevalent virus type in this group was HPV 16 (45%; 95% CI: 32%-38%). In order to verify the slot-blot results, a proportion of the samples was also investigated by PCR. There was 88% correlation between the 2 tests. The high prevalence of HPV 16 and 18 infection demonstrated in our low-cervical-cancer-risk area further support the role of as yet unidentified co-factors as determinants of the different geographic rates of cervical-cancer incidence.

Screening for high- and low-risk human papillomavirus types in single routine cervical smears by non-isotopic in situ hybridization

Routine cervical smears (n = 262) from a Sexually Transmitted Diseases clinic were screened by non-isotopic in situ hybridization (NISH) stratifying human papillomavirus (HPV) infections into HPV6/11 (low risk) and HPV16/18/33 (high risk) categories. Of 188 patients with cytologically normal smears, HPV sequences were demonstrated in 41%. Of the 128 cases analysed by dual NISH, 16% contained low risk, 20% high risk and 5% both groups. In patients with cytological evidence of wart virus infection (WVI) only, 54% (n = 50) contained high-risk and 22% low-risk HPV types. The comparable incidences in CIN1/2 plus WVI (n = 24) were not significantly different: 54% and 17%, respectively. Cytological criteria underestimate the prevalence of HPV infection in patients with cytologically normal smears. This represents either 'occult' or 'latent' infection. The identical prevalence of HPVB16/18/33 in WVI only, and CIN1/2 plus WVI, suggests that the cytopathic effect induced by these HPVs may represent one end of a spectrum of morphological change which progresses to cervical intraepithelial neoplasia (CIN).

Detection of HPV DNA in archival specimens of cervical cancer using in situ hybridisation and the polymerase chain reaction

An archival survey of 98 cervical cancer specimens dating from the 1920s to the 1980s was undertaken to determine whether changes had occurred in the prevalence of human papilloma-virus (HPV) DNA. HPV DNA was detected in paraffin sections of cancers fixed in 10% formalin by in situ hybridisation (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 30 instances results obtained from Southern blot hybridisations which had been carried out on specimens of fresh tissue from the same cancers collected during the 1980s were available for comparison. The rates of HPV DNA detection in cervical cancers ranged from 83% (by Southern or PCR) and 70% (by ISH) on specimens from the 1980s, to 50% and 63% (by ISH and PCR, respectively) on specimens from the 1920s. HPV 16 was by far the most common type, being identified by Southern or ISH in approximately 92% of HPV DNA-positive specimens. No significant change in the prevalence of HPV DNA, or of HPV types, in cervical cancers was found over the 65 year period examined.

Use of the polymerase chain reaction to study the relationship between human papillomavirus infections and cervical cancer

Although it is now evident that human papillomaviruses (HPV) are strongly associated with cervical cancer, their etiological role in the oncogenesis of this disease is still unknown. However, HPV screening may identify women at risk of acquiring this disease. With the recent development of the polymerase chain reaction (PCR), it has become possible to detect small numbers of human papillomavirus genomes in clinical samples. The sensitivity and specificity of this technique, together with the possibility of performing the test on crude cervical scrapes, makes PCR the method of choice for screening. In this paper, data on the detection of human papillomavirus by PCR are presented and the applicability of this technique for the screening of human papillomavirus genotypes is evaluated. The question arises whether screening for diagnostic purposes must include all the human papillomavirus types associated with infections of the genital tract or only those which are strongly associated with cervical cancer (HPV 16 and HPV 18). It is proposed that an international council must be created that is responsible for standardised epidemiological screening strategies and follow-up programmes.

Use of sulfonated primers to detect and type papillomavirus in cell cultures and cervical biopsies

Human papillomavirus (HPV) was detected by using two sets of deoxyribonucleotide primers for differentiating between 'low-risk' types (HPV11 and HPV6) and 'high-risk' (hri) types (HPV16, HPV18 and HPV33). A new application of the Chemiprobe method for labeling DNA was used to detect products of the polymerase chain reaction (PCR) from 36 cervical biopsies. This method, first demonstrated by Uchimura et al. (submitted), is based on the sulfonation of a polycytidylic acid tail of 5-20 monomers attached to the 5' end of either one or both of the PCR primers. This procedure can increase the sensitivity of detection of PCR products more than 100-fold with respect to ethidium bromide (EtdBr) staining. Various methods were used to detect hri HPV DNA in the 36 clinical samples. The number of positive results obtained was as follows, two by Southern-blot hybridization; five by PCR amplification followed by electrophoresis and detection of products by EtdBr staining; six by PCR amplification using one or two sulfonated C-tailed primers followed by electroblotting and immunoenzymatic visualization; and five by hybridization of sulfonated genomic viral recombinant with a PCR product immobilized on a membrane. The yield of the PCR product was significantly greater when one of the primers was C-tailed than when both or neither of the primers were C-tailed. PCR employing sulfonated C-tailed oligo primers is very specific and sensitive, and the entire procedure can be employed as a nonradioactive substitute for radioactive dot-blot or Southern-blot hybridization procedures, routinely used for detection of HPV in clinical samples.

Prevalence of HPV cervical infection in a family planning clinic determined by polymerase chain reaction and dot blot hybridisation

The overall prevalence of human papillomavirus (HPV) cervical infection in 131 women attending a family planning clinic was 7% (HPV 6/11, 16, 18, 31) by dot blot hybridisation, 53% (HPV 11, 16, 31) by polymerase chain reaction (PCR), and 56% by the two methods combined. HPV 16 and 18 were the commonest types (4% each) by dot blot, HPV 16 (39%) by PCR. Fifteen percent of subjects had mildly abnormal cervical cytology (grades 1A, 2A, or 3). There was no significant correlation between cytological abnormality and HPV positivity, or between cytological or HPV status and other postulated risk factors for cervical neoplasia. It is concluded that PCR is considerably more sensitive than dot blot DNA hybridisation in detecting HPV cervical infection in such a "low risk" setting, where HPV copy number may be low. Firm conclusions cannot be drawn from our results regarding a causal role for HPV or other factors in the development of cervical neoplasia.