Molecular variability of human papillomaviruses and susceptibility to cervical neoplasia

RESUMO

Genetic variability in the genome of human papillomaviruses (HPV) has been described, particularly in the high-risk types 16 and 18. Based on extensive DNA sequencing analyses of HPV isolates from clinical specimens, a number of variants have been described whose nucleotide sequence does not vary more than 2 percent in coding and 5 percent in noncoding regions of the viral genome. Nucleotide sequence variation has being used as a tool for epidemiological studies of viral transmission and persistence. In the ongoing cohort study being performed in Brazil, we are abalyzing the risk of persistent infection and development of cervical lesions regarding geographical relatedness of variants. Infections with HPV types 16 and 18 were more likely to persist than those with other oncogenic types, with no significant differences between European and non-European variants regarding their tendency to persist. On the other hand, non-European HPV 16 and 18 variants were more strongly associated with risk of cervical neoplasia during follow-up than European variants, as compared with other oncogenic HPVs and low oncogenic risk HPVs. Epitope variability mays also have important implications in the immune response elicited against these viruses as well as in the design of vaccines directed against HPVs. Since these viruses are the etiologic agents of cervical cancer, those studies may provide useful information for the control of these common infections, leading ultimately to a reduction in the morbidity and mortality rates associated with this cancer.