Characterization of Human Papillomavirus Type 70 (HPV70)

Human papillomavirus type 70 (HPV70) is a member of the Alphapapillomavirus 7 species group and is phylogenetically related to several carcinogenic HPV types, yet it is not classified as such. Despite its evolutionary relationships to high-risk types such as HPV18, HPV39, and HPV45, HPV70 remains understudied, particularly regarding its genetic diversity and epidemiology. This study aimed to characterize HPV70 genetic diversity using both publicly available whole-genome sequences and a large patient-derived dataset. A total of 259 HPV70 genome sequences were collected from public databases and a Kaiser Permanente cohort. Following quality control filtering of the datasets, 224 high-quality sequences were retained for analysis. Multiple sequence alignment, phylogenetic tree construction using Neighbor-Joining and Maximum Likelihood methods, and pairwise genetic distance analyses were used to determine lineage structure. Genome-level variation was further assessed using visualization to identify single-nucleotide polymorphisms (SNPs) along with insertion and deletion events. Phylogenetic analyses confirmed the presence of two previously described lineages, A and B, and provided evidence supporting two additional lineages, C and D. Consistent grouping across methods, supported by pairwise distance and the absence of recombination, strengthened confidence in the phylogenetic tree structure. Multiple lineage-associated SNPs and repeated insertion events were also noted, which suggested additional features that may contribute to the epidemiology of the virus. Although sublineage structure was not determined in this study, initial evidence indicated more in-depth genetic variation within major lineages. Overall, this study expands the current knowledge base of HPV70 genomic diversity and establishes a structure for further lineage classification and research. These findings highlight the importance of continued research on understudied HPV types and provide a foundation for future work investigating HPV70 sublineages, insertion events, and epidemiological relationships across populations.