The intratypic variability of HPVs 16 and 18 has been extensively studied and has been used as an important tool in epidemiological studies of viral transmission, persistence and progression to clinically relevant cervical lesions. Infections by non-European variants of HPVs 16 and 18 are associated with an increased risk for the development of high grade squamous intraepithelial lesions (HSIL). Our aim was to correlate the intratypic molecular variability of both HPV types and risk of persistent infection and lesion outcome in a cohort study conducted in Brazil. We characterized molecular variants of HPV types 16 and 18 by sequencing a fragment of the LCR, and of the E6 and L1 genes, for HPV-16 variants only. For both types, European variants composed the most prevalent and diverse group. Persistent infections with HPV-18 were associated with continuous detection of European variants. However, risk for simultaneous detection of HSIL and HPV DNA was higher in women harboring non-European variants of HPV-16. The same trend was observed with HSIL detected during follow-up. Our study confirms the association between non-European variants and risk of cervical neoplasia, and highlights the importance of their geographic distribution for cervical cancer risk assessment. ' 2007 Wiley-Liss, Inc.Key words: human papillomavirus; molecular variants; oncogenic potential; cohort study; cervical neoplasia More than 120 different human papillomavirus (HPV) genotypes associated with infections in humans have been described, of which approximately 40 infect the anogenital area. Nearly 20 of these are classified as high-risk HPV types (HR-HPV) due to their association with cancer. In particular, HPVs 16 and 18 are the most common high-risk types in cancer biopsies, worldwide. 1 Their oncogenic potential has been demonstrated both in vitro and in vivo. 2 Nevertheless, only a minority of women infected with HPVs 16 and 18 develop neoplastic lesions. 3,4 Intratypic molecular variants of HPVs are characterized by differences in nucleotide sequence from the prototypic L1 gene of less than 2%. 5 Recently, full genome analysis of HPV-16 isolates revealed that 4% of the sequence is variable. 6 Moreover, these authors described a 9.9% amino acid variability within the eight HPV genes of the different HPV-16 molecular variants studied. The nucleotide variability of HPVs 16 and 18 has been extensively studied, and several molecular variants have been described on the basis of their geographical distribution. 7-9 Studies conducted in multiethnic populations have shown the association between Asian-American or other non-European variants of HPVs 16 and 18 and increased risk of persistent infection and development of cervical lesion. 4,10-13 Specific variants of HPVs 16 and 18 seem to be associated also with certain histopathological features of cervical neoplastic lesions. 10,14,15 In one study, Asian-American variants of both HPVs 16 and 18 were associated with squamous cell carcinomas and adenocarcinomas, while European variants were assoc...

There is paucity of data on whether or not women can be re-infected with human papillomavirus (HPV) types to which they were exposed earlier in life and on the role of natural immunity. The observation of HPV infection at older ages may be explained by reactivation of a latent infection or new exposure from sexual activity. Our objective was to analyze the association between re-infection and sexual activity. We analyzed data from 2462 women enrolled in the Ludwig-McGill cohort and followed every 4-6 months for up to 10 years. We performed HPV typing and viral load measurements via polymerase chain reaction and determined HPV-16 seroreactivity at enrolment. Incidence of infection and re-infection were estimated for individual types. Adjusted relative risks (RR) for the association between infection/re-infection and new sexual partners were calculated using Cox regression. Rates of initial infection and re-infection post-clearance were statistically comparable. RRs of initial infection or re-infection were consistently associated with new sexual partners (2.4 [95%CI: 2.0-3.1] for first infection, 3.7 [1.1-13.8] for re-infection with the same type, and 2.3 [1.5-3.7] for re-infection with a different type). Re-infection in older women was also associated with new sexual partners (RR=2.8, 95%CI: 1.4-5.3) as were new infections with HPV-16 among women with serological evidence of prior HPV-16 exposure (RR=3.0, 95%CI: 1.6-5.3). Viral loads at initial infection and at re-infection were comparable. HPV infection and re-infection were strongly associated with sexual activity. This study suggests that natural immunity does not play a role in controlling the extent of re-infections.