The characterization of two novel neotropical primate papillomaviruses supports the ancient within-species diversity model

Papillomaviruses (PVs) are non-enveloped icosahedral viruses with a circular double-stranded DNA genome of ∼8,000 base pairs (bp). More than 200 different PV types have been identified to date in humans, which are distributed in five genera, with several strains associated with cancer development. Although widely distributed in vertebrates, Neotropical Primates (NP) PV infection was described for the first time only in 2016. Currently, four complete genomes of NP PVs have been characterized, three from Saimiri sciureus (SscPV1 to SscPV3) and one from Alouatta guariba (AgPV1). In this work, we describe two novel PV strains infecting Callithrix penicillata (provisionally named CpenPV1 and CpenPV2), using anal swab samples from animals residing at the Brasilia Primatology Center and next generation sequencing. The genomes of CpenPV1 (7,288 bp; 41.5% guanine-cytosine content - GC) and CpenPV2 (7,250 bp; 40.7% GC) contain the characteristic open reading frames (ORFs) for the early (E6, E7, E1, E2, and E4) and late (L2 and L1) PV genes. The L1 ORFs, commonly used for phylogenetic identification, share 76 per cent similarity with each other and differ 32 per cent from any other known PV, indicating that these new strains meet the criteria for defining novel species. PV genes phylogenetic variance was analyzed and different degrees of saturation revealed similar levels of topological heterogeneity, ruling out saturation as primary etiological factor for this phenomenon. Interestingly, the two CpenPV strains form a monophyletic clade within the Gammapapillomavirus genus (provisionally named gammapapillomavirus 32). Unlike for other NP PV strains, which grouped into a new sister genus of Alphapapillomavirus, this is the first report of NP PV strains grouping into a genus previously considered to exclusively comprise Old World Primates (OWP) PVs, including human PVs. These findings confirm the existence of a common ancestor for Gammapapillomavirus already infecting primates before the split of OWP and NP at ∼40 million years ago. Finally, our findings are consistent with an ancient within-species diversity model and emphasize the importance of increasing sampling to help understanding the PV-primate codivergence dynamics and pathogenic potential.