Sequence conservation within the major capsid protein of human papillomavirus (HPV) type 18 and formation of HPV-18 virus-like particles in Saccharomyces cerevisiae

The major capsid protein L1 of human papillomaviruses (HPVs) has been identified as a promising candidate antigen for a prophylactic HPV vaccine. Since amino acid sequence heterogeneity has been demonstrated for the L1 genes within individual HPV types, nucleotide sequences for L1 were determined from six HPV-18 clinical isolates and the cervical carcinoma cell line SW756 and compared to the published HPV-18 prototype sequence. The sequences were almost identical between the clinical isolates and SW756 but differed markedly from the published prototype sequence. Resequencing the prototype HPV-18 revealed that these differences were due to sequencing artifacts of the prototype HPV-18 sequence archived in GenBank. Thus, the HPV-18 L1 genes seem to display a very high level of sequence conservation. The HPV-18 L1 gene derived from SW756 was expressed in Saccharomyces cerevisiae and self-assembly of the L1 protein into viruslike particles was demonstrated.