Human papilloma virus prevalence, genotype distribution, and pattern of infection in Thai women.

Background: The pattern of infection in cervical lesions with respect to HPV subtype has not been systematically studied in Thai women. The aim here was to determine HPV prevalence, genotype, and infection pattern in cervical lesions and to estimate the potential efficacy of an HPV prophylactic vaccine.

Design: Formalin-fixed paraffin-embedded cervical tissue blocks of 410 Thai patients from 8 institutes in 4 regions of Thailand (northern, southern, north-eastern, and central) were studied. The samples included 169 low grade squamous intraepithelial lesions (LSILs), 121 high grade squamous intraepithelial lesions (HSILs), and 120 squamous cell carcinomas (SCCs). HPV-DNA was amplified by PCR using consensus primers GP5+ and GP6+. The HPV genotype was then determined by reverse linear blot assay that included 37 HPV-specific 5'-amino-linked oligonucleotide probes. Patterns of infection were classified as single infection (one HPV type), double infection (two HPV types), and multiple infection (three or more HPV types).

Results: The mean age of the subjects was 42 years. The prevalence of HPV infection was 88.8%. The highest HPV prevalence was found in the southern region (97.1%) and the lowest in the central region (78.6%). HPV-DNA was detected in 84.6% of LSILs, 90.1% of HSILs, and 93.3% of SCCs. A total of 20 HPV genotypes were identified. The five most common high risk HPV were HPV16 (83.2%), HPV18 (59.3%), HPV58 (9.3%), HPV52 (4.1%), and HPV45 (3.8%). In double and multiple infection patterns, the most common genotypes were HPV16/18 (27.8%) and HPV11/16/18 (54.9%). HPV6 was found only in LSIL and never in combination with other subtypes. HPV11 was most common in LSIL.

Conclusion: There is no difference of HPV type distribution in women from 4 regions of Thailand with prominent HPV16 and HPV18 in all cases. The bivalent and quadrivalent vaccines have the potential to prevent 48.6 % and 74.5% of cervical cancers in Thai women. The potential of cancer prevention would rise to 87.6% if other frequent HR-HPV types (HPV58, 52, and 45) were also targeted by an HPV vaccine.