DNA-EIA to detect high and low risk HPV genotypes in cervical lesions with E6/E7 primer mediated multiplex PCR

Prevalence of human papillomavirus infection in women in Benin, West Africa

BACKGROUND

Cervical cancer ranks as the first most frequent cancer among women in Benin. The major cause of cervical cancer now recognized is persistent infection of Human Papillomavirus (HPV). In Benin there is a lack of screening programs for prevention of cervical cancer and little information exists regarding HPV genotype distribution.

METHODS

Cervical cells from 725 women were examined for the presence of viral DNA by means of a polymerase chain reaction (PCR) multiplex-based assay with the amplification of a fragment of L1 region and of E6/E7 region of the HPV genome, and of abnormal cytology by Papanicolaou method. The association between HPV status and Pap test reports was evaluated. Socio-demographic and reproductive characteristics were also related.

RESULTS

A total of 18 different HPV types were identified, with a prevalence of 33.2% overall, and 52% and 26.7% among women with and without cervical lesions, respectively. Multiple HPV infections were observed in 40.2% of HPV-infected women. In the HPV-testing group, the odds ratio for the detection of abnormal cytology was 2.98 (95% CI, 1.83-4.84) for HPV positive in comparison to HPV negative women. High risk types were involved in 88% of infections, most notably HPV-59, HPV-35, HPV-16, HPV-18, HPV-58 and HPV-45. In multiple infections of women with cytological abnormalities HPV-45 predominated.

CONCLUSIONS

This study provides the first estimates of the prevalence of HPV and type-specific distribution among women from Benin and demonstrates that the epidemiology of HPV infection in Benin is different from that of other world regions. Specific area vaccinations may be needed to prevent cervical cancer and the other HPV-related diseases.

Epidemiological and clinical aspects of human papillomavirus detection in the prevention of cervical cancer

Cervical cancer is a major cause of death, and the second most frequent cancer in women worldwide. Many studies have indicated a causal relation between genital human papillomavirus (HPV) infections and cervical cancer. High-risk HPV genotypes have been detected in almost 100% of all cervical cancers, and the process of HPV mediated carcinogenesis has been partly clarified. The concept that HPV is a obligatory cause in cervical cancer development has lead to extensive research regarding the incorporation of HPV detection in (1) cervical cancer prevention programs, (2) triage of women with abnormal cervical scrapes in the screening program, and (3) follow-up of patients treated for cervical intraepithelial neoplasia (CIN). Epidemiological studies indicate that 50% of women becoming sexually active contract a genital HPV infection within 2 years. The lifetime risk of a genital HPV infection is estimated to be 80%, but very few of these women will develop cervical cancer. Several studies have shown that the persistence of genital HPV infections is especially related to the development of cervical cancer. As a result, HPV detection at a single moment was shown to be of limited clinical value in the triage of patients with abnormal cervical scrapes, or during follow-up after treatment for CIN. Furthermore, major variations in the sensitivity of different HPV detection methods, as well as differences in HPV detection related to the menstrual cycle, have shown that many facts regarding HPV transmission, replication, and detection need to be clarified, before HPV detection can be of clinical value.

Human papillomavirus testing methods

Testing for human papillomavirus (HPV) relies exclusively on techniques of molecular biology using nucleic acid probes. Tests for HPV using nucleic acid probes have been commercially available since the late 1980s, but early tests were cumbersome, involving the use of nucleic acid probes labeled with radioactive phosphorus (32P). These early HPV tests did not achieve widespread use because they did not detect all oncogenic HPV genotypes. The current commercial HPV detection kit, Digene's Hybrid Capture 2 kit, detects virtually all high-risk oncogenic HPV types, as well as most low-risk nononcogenic HPV genotypes. The Hybrid Capture 2 test format is a proprietary nucleic acid hybridization signal amplification system owned by Digene Corporation. Virtually all test formats for DNA sequence analysis are amenable to applications intended to detect and perhaps quantify the various HPV genotypes. These methods can involve direct hybridization with complementary DNA probes, such as Southern blotting or in situ hybridization, signal amplification, such as the Hybrid Capture 2 method or target nucleic acid amplification, most notably the polymerase chain reaction (PCR). Polymerase chain reaction has been used for HPV detection, genotyping, and viral load determination. General or consensus primer-mediated PCR assays have enabled screening for a broad spectrum of HPV types in clinical specimens using a single PCR reaction. Following amplification using consensus primers, individual HPV genotypes are identified using a variety of methods. Using consensus primers in a test format known as real-time quantitative PCR (RQ-PCR), it is possible to generate viral load (concentration) data from reaction curves generated by monitoring PCR reaction kinetics in real time.

Evaluation of commercial kits for the detection and typing of human papillomavirus in cervical swabs

Human papillomaviruses (HPV) detection by MY consensus primers amplification within the L1 region and typing of prevalent genital HPVs by reference and commercial sets of probes was compared by PCR-ELISA systems. The specificity of commercial probes used in the L1 HPV Geno-Kit with respect to the reference probes proved to be 100%, with an overall agreement of 97.6%. The discordant results concerned only the detection of HPV 16, both as single genotype present in the sample and as multiple infections. The analytical sensitivity of the commercial probe for HPV 16 proved to be slightly less sensitive than the reference probe in the hybridisation conditions of the PCR-ELISA system. The L1 PCR-ELISA reference system was evaluated further in comparison with commercial E6/E7 consensus PCR and microplate hybridisation by typing kit. Amplified products of both the L1 and E6/E7 consensus regions were also analysed by agarose gel electrophoresis. An overall concordance of 95.2% was found. On account of its specificity and sensitivity the E6/E7 commercial system proved to be particularly useful for diagnostic laboratory, as it detects only the prevalent high risk genotypes. The agarose gel detection can therefore be used as screening test, thus reducing the costs, while the E6 E7 HPV Geno-Kit High Risk can be used when specific typing is required.

Detection of human papillomavirus DNA by PCR/microfluorometry for screening of cervical cancer

BACKGROUND

Cervical cancer screening is conducted by a cytological Papanicolaou (Pap) test. For screening, it is becoming increasingly important to introduce a more objective result, based on human papillomavirus (HPV) DNA test. We describe here a practical method allowing the mass detection of HPV-DNA by PCR followed by fluorogenic DNA intercalation.

METHODS

Samples used were cervical scrapes or biopsy specimens obtained from women who had undergone cytological testing for cervical cancer. Crude DNAs were extracted by a simplified proteinase K-boil method. Common and type-specific primers were newly designed for major types of high-risk HPVs. A fluorogenic DNA intercalator, SYBR Green I was directly added to the specific PCR products. The resultant fluorescence was measured by a conventional fluorometric microplate reader.

RESULTS

The proposed PCR/microfluorometry (MFL) allowed a simple, rapid and economical detection of HPV-DNA without any use of labeling primers or probes. HPV-DNAs were found in 48.2% (123/255) of the cervical scrapes. The detection rate of HPV in cervical cancer biopsy specimen was 92.4% (61/66).

CONCLUSIONS

PCR/MFL detection of HPV-DNA, followed by combined type-specific PCR, is expected to be an extremely useful tool in cervical cancer screening.

Multiplex PCR: optimization and application in diagnostic virology

PCR has revolutionized the field of infectious disease diagnosis. To overcome the inherent disadvantage of cost and to improve the diagnostic capacity of the test, multiplex PCR, a variant of the test in which more than one target sequence is amplified using more than one pair of primers, has been developed. Multiplex PCRs to detect viral, bacterial, and/or other infectious agents in one reaction tube have been described. Early studies highlighted the obstacles that can jeopardize the production of sensitive and specific multiplex assays, but more recent studies have provided systematic protocols and technical improvements for simple test design. The most useful of these are the empirical choice of oligonucleotide primers and the use of hot start-based PCR methodology. These advances along with others to enhance sensitivity and specificity and to facilitate automation have resulted in the appearance of numerous publications regarding the application of multiplex PCR in the diagnosis of infectious agents, especially those which target viral nucleic acids. This article reviews the principles, optimization, and application of multiplex PCR for the detection of viruses of clinical and epidemiological importance.

Multiplex PCR: optimization and application in diagnostic virology

PCR has revolutionized the field of infectious disease diagnosis. To overcome the inherent disadvantage of cost and to improve the diagnostic capacity of the test, multiplex PCR, a variant of the test in which more than one target sequence is amplified using more than one pair of primers, has been developed. Multiplex PCRs to detect viral, bacterial, and/or other infectious agents in one reaction tube have been described. Early studies highlighted the obstacles that can jeopardize the production of sensitive and specific multiplex assays, but more recent studies have provided systematic protocols and technical improvements for simple test design. The most useful of these are the empirical choice of oligonucleotide primers and the use of hot start-based PCR methodology. These advances along with others to enhance sensitivity and specificity and to facilitate automation have resulted in the appearance of numerous publications regarding the application of multiplex PCR in the diagnosis of infectious agents, especially those which target viral nucleic acids. This article reviews the principles, optimization, and application of multiplex PCR for the detection of viruses of clinical and epidemiological importance.

Co-factors related to the causal relationship between human papillomavirus and invasive cervical cancer in Honduras

BACKGROUND

A case-control study was conducted in Honduras to identify co-factors in the carcinogenic pathway by which human papillomavirus (HPV) causes invasive cervical cancer.

METHODS

Ninety-nine cases aged 23-65 (median 47) years participated. Two controls were matched to each case by age and clinic where they first presented for cytological screening; controls had no cervical abnormalities. Information on risk factors was obtained by personal interviews in the clinics regarding sociodemographic, reproductive and behavioral characteristics. Human papillomavirus was detected in cervical scrapes by general primer-mediated polymerase chain reaction (PCR) followed by sequence analysis to identify the different types present.

RESULTS

All cases had squamous cell tumours and most were FIGO (International Federation of Gynecologists and Obstetricians) class II or higher; HPV was strongly associated with cervical cancer (odds ratio [OR] = 7.66, 95% CI : 3.88-15.1). Among HPV-positive women, dose-response relationships were observed for education, age at first intercourse and exposure to wood smoke that persisted after adjustment for previous screening. Among HPV-negative women, the number of sexual partners and parity were associated with cervical cancer. The protective effect of previous cytological screening operated independently of HPV.

CONCLUSIONS

Our findings speak for the powerful role that both primary and secondary education plays in fostering a lifestyle that reduces the risk of invasive cervical cancer. The data suggest that important elements of such a lifestyle include later age at first sexual intercourse, a limited number of pregnancies, greater likelihood of undergoing cytological screening and reduced exposure to carcinogens in the household environment.

The Use of Molecular Techniques for the Diagnosis and Epidemiologic Study of Sexually Transmitted Infections

Molecular diagnostic tests are more sensitive and, in many cases, more specific than conventional laboratory methods for the detection of sexually transmitted infections. Here, we review recently developed molecular methods for the diagnosis and subtyping of the most common sexually transmitted infections: infections caused by Chlamydia trachomatis, Neisseria gonorrhoeae, human papillomavirus, Trichomonas vaginalis, and the agents of genital ulcer disease (Haemophilus ducreyi, herpes simplex virus, Treponema pallidum, and Calymmatobacterium granulomatis). We also provide an overview of the laboratory diagnostic tests and clinical specimens to use when infection with these agents is suspected.

Development and clinical evaluation of a highly sensitive PCR-reverse hybridization line probe assay for detection and identification of anogenital human papillomavirus

Human papillomavirus (HPV) can be detected by amplification of viral DNA. A novel PCR primer set generating a short PCR fragment (SPF PCR) was used for amplification of a fragment of only 65 bp from the L1 region and permitted ultrasensitive detection of a broad spectrum of HPV genotypes. The intra- and intertypic sequence variations of the 22-bp interprimer region of this amplimer were studied. Among 238 HPV sequences from GenBank and clinical specimens, HPV genotypes were correctly identified based on the 22-bp sequence in 232 cases (97.2%). Genotype-specific probes for HPV genotypes 6, 11, 16, 18, 31, 33 to 35, 39, 40, 42 to 45, 51 to 54, 56, 58, 59, 66, 68, 70, and 74 were selected, and a reverse hybridization line probe assay (LiPA) (the INNO-LiPA HPV prototype research assay) was developed. This LiPA permits the use of amplimers generated by the SPF as well as the MY 09/11 primers. The assay was evaluated with a total of 1, 354 clinical specimens, comprising cervical scrapes (classifications ranging from normal cytology to severe dyskaryosis) and formalin-fixed, paraffin-embedded cervical carcinoma samples. LiPA results were highly concordant with sequence analysis of the SPF amplimer, genotype-specific PCR, and sequence analysis of amplimers generated by MY 09/11 primers. The sensitivity of the SPF primers was higher than that of the GP5(+)/6(+) primers over a broad range of HPV types, especially when multiple HPV genotypes were present. In conclusion, the SPF LiPA method allows extremely sensitive detection of HPV DNA as well as reliable identification of HPV genotypes in both cervical smears and paraffin-embedded materials.

Hybrid capture II, a new sensitive test for human papillomavirus detection. Comparison with hybrid capture I and PCR results in cervical lesions

AIM

To test a new assay for the detection of human papillomavirus (HPV) DNA, hybrid capture II (HC II), compared with the previous commercialized hybrid capture I (HC I) and polymerase chain reaction (PCR) results on cervical scrapes from fresh cone excision biopsy samples.

METHODS

The three methods were used on cervical scrapes from 42 fresh cone excision biopsy samples. There were nine metaplastic and inflammatory lesions, five low grade lesions, and 28 high grade lesions. PCR was performed using the general primers GP5+/GP6+. The viral load of high risk HPV DNA was estimated by the ratio of relative light units to positive control values in the samples.

RESULTS

The sensitivity of HC I for the detection of high grade lesions was 71.4%, while it was 92.8% for HC II and 96.4% for the PCR. Considering only the absence of detectable cervical in situ neoplasia, the specificity was 88.9% for HC I, 66.7% for HC II, and 66.7% for PCR. With HC II, for a ratio of cervical sample to normal control of > 200, the sensitivity for the detection of high grade lesion was only 34.6% with a specificity of 66.7%.

CONCLUSIONS

HPV detection with the HC II assay is more sensitive than the previous HC I and represents a more convenient and easier test than PCR for routine use. Nevertheless the viral load estimated with this test cannot be a reliable predictive indicator of high grade lesions.

Human papillomavirus infection with particular reference to genital disease

HPV is the commonest sexually transmitted viral infection in the United Kingdom and as such poses a major public health problem. In addition to the potential physical morbidity associated with genital warts, abnormal cervical cytology, and anogenital dysplasia and neoplasia, the associated psychological morbidity should not be forgotten. Although our knowledge of viral function and disease pathogenesis has advanced appreciably in recent years, we are still some way from developing an in vitro method of viral propagation. Vaccination against HPV infection will hopefully be achieved within the next 10 years, but a prevention and treatment strategy which is appropriate for both developed and developing nations must be our major long term goal.