Nucleotide and amino acid sequence variations in the L1 open reading frame of human papillomavirus type 6

Human papillomavirus (HPV) type 6 induces benign tumors such as condyloma acuminata and laryngeal papilloma. The HPV-6 DNA has been thought to be a heterogeneous group of subtypes and variant-types. To examine sequence variations of the HPV-6 L1 ORF, we analyzed by single-strand conformation polymorphism (SSCP) and by DNA sequencing 21 specimens from condyloma acuminata and laryngeal papilloma that harbor HPV-6 DNA. PCR products of HPV-6 DNA were digested with 6 restriction enzymes yielding 8 fragments, which were then analyzed by SSCP. The resolution patterns showed that the L1 coding sequences were separated into three SSCP groups, I, II, and III, and two minor groups, (I) and (III). By sequencing the five representatives of each SSCP group and by comparing these sequences with those of HPV-6a [Hofmann et al., 1995] and HPV-6b [Schwarz et al., 1983], we identified base substitutions at 20 positions in the L1 coding region and an amino acid substitution in one case.