1 Department of Medical Microbiology, University of Lund, S-20502 Malmö, Sweden
2 Department of Gynaecology and Obstetrics, Central Hospital of Maputo, Mozambique
3 Department of Pathology, Malmö University Hospital, Sweden
Correspondence
Joakim Dillner
joakim.dillner{at}mikrobiol.mas.lu.se
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ABSTRACT |
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MAIN TEXT |
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From June 2002 to April 2003, all women with suspected cervical cancer at the Department of Gynaecology at the Central Hospital of Maputo, the capital of Mozambique, were asked to participate. Following written consent, two biopsies were taken from each tumour, one was formalin-fixed and used for histological diagnosis, the other biopsy was frozen for HPV DNA detection. Human immunodeficiency virus (HIV) testing was performed on serum samples and a questionnaire recorded socio-demographic factors. Ethical approval was obtained from the Commission of Investigation and Ethics at the Central Hospital in Maputo and from Lund University Research Ethics Committee in Sweden.
Biopsies and serum samples were successfully obtained from 88 of 94 patients and transported to Sweden for HPV analysis. Histopathological diagnosis was evaluated in Mozambique and in Sweden. Fourteen patients were excluded because invasive cervical cancer could not be confirmed and two samples were negative in the specimen adequacy test (-globin PCR). One patient had adenosquamous carcinoma, the others squamous carcinoma. The mean age was 46 years. HPV DNA was detected using general primer PCR (GP5+/GP6+ primers) and HPV DNA typing was performed by reverse dot-blot hybridization (RDBH) assay with full-genomic clones (Forslund et al., 2002
) of HPV types 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 66 and 68. GP5+/6+ PCR-negative samples were analysed further using type-specific PCR for HPV-16 and -18 and with another HPV general primer system (MY09/11), followed by HPV typing by sequencing. The last few still HPV-negative samples were also amplified with multiply primed rolling-circle amplification (RCA) (Rector et al., 2004
) before GP5+/6+ PCR and RDBH. A repeat analysis of 25 % of the samples found identical results. HIV testing was performed using Axsym (Abbot), followed by confirmation using RIBA HIV-1/HIV-2 SIA (Chiron).
The HPV prevalence was 66 of 72 (92 %) using GP5+/GP6+ primers. This increased to 68 of 72 (94 %) after testing with type-specific PCR and MY09/11 PCRs and reached 70 of 72 (97 %) with prior amplification with RCA before the PCR. It appears that the combination of RCA and PCR is a promising new strategy to minimize false-negative results in diagnostic virology.
The most common HPV types were 16 and 18, being present in 69 % of tumours (Table 1). Although coexistence with other HPV types was common (13, 7, 3 and 1 women were infected with 2, 3, 4 and 5 HPV types, respectively), a substantial proportion of cases (36 %) had a single HPV infection with either HPV-16 or -18.
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Our findings that HPV-16 and -18 are the most frequent HPV infections associated with cervical cancer in Mozambique is in concordance with the overall world distribution of HPV types in cervical cancer (Clifford et al., 2003), but is not in line with a study by Castellsague et al. (2001)
who investigated 239 healthy women and 23 women with cervical dysplasia in Mozambique, and found HPV-35 and 58 to be the most common HPV types. We investigated the HPV type distribution in invasive cervical cancer. Different HPV types are associated with different cancer risks (Clifford et al., 2003
), and circulation of HPV types among women without cancer may therefore not accurately reflect which HPV types cause invasive cervical cancer in a population. Furthermore, in many countries it is difficult to obtain representative population-based samples from healthy women or women with asymptomatic lesions. Recruitment of symptomatic women with cancer at the major site offering health care in the country may therefore have resulted in a more representative sample of oncogenic HPV types. However, it should be noted that HPV-35 was not uncommon in our series, being found in 19 % of patients.
Continued investigation and monitoring of which HPV types that actually cause cervical cancer in different countries is undoubtedly an important endeavour. Our study suggests that HPV vaccines targeting HPV-16 and -18, the two worldwide most frequent oncogenic HPV types, would have a substantial impact on cervical cancer also in Mozambique.
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ACKNOWLEDGEMENTS |
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REFERENCES |
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Clifford, G. M., Smith, J. S., Aguado, T. & Franceschi, S. (2003). Comparison of HPV type distribution in high-grade cervical lesions and cervical cancer: a meta-analysis. Br J Cancer 89, 101105.[CrossRef][Medline]
Davies, P., Kornegay, J. & Iftner, T. (2001). Current methods of testing for human papillomavirus. Best Pract Res Clin Obstet Gynaecol 15, 677700.[CrossRef][Medline]
Forslund, O., Antonsson, A., Edlund, K. & 9 other authors (2002). Population-based type-specific prevalence of high-risk human papillomavirus infection in middle-aged Swedish women. J Med Virol 66, 535541.[CrossRef][Medline]
Koutsky, L. A., Ault, K. A., Wheeler, C. M., Brown, D. R., Barr, E., Alvarez, F. B., Chiacchierini, L. M. & Jansen, K. U. (2002). A controlled trial of a human papillomavirus type 16 vaccine. N Engl J Med 347, 16451651.
Rector, A., Tachezy, R. & Van Ranst, M. (2004). A sequence-independent strategy for detection and cloning of circular DNA virus genomes by using multiply primed rolling-circle amplification. J Virol 78, 49934998.
Received 30 January 2004;
accepted 13 May 2004.