Identification of the novel KI and WU polyomaviruses in human tonsils.

Background: Three novel polyomaviruses have been recently discovered: KI, WU and MC polyomaviruses. Their role in human pathology is debated while tissue tropism and site of latency remain unknown.

Objective: To test the hypothesis that KI, WU and MC polyomaviruses can infect human tonsils.

Study Design: Archival paraffin-embedded tonsils from 91 patients affected by different tonsil diseases were screened by polymerase chain reaction to detect viral DNA of KIV, WUV, MCV, BKV and JCV. Phylogenetic and evolutionary analysis of the identified polyomaviruses was carried out.

Results: Of the 91 tested specimens, 11 contained KIV DNA (12%), 4 WUV DNA (4.4%), 5 BKV DNA (5.5%). MCV and JCV were not detected. Phylogenetic analysis showed that KIVs identified in tonsils fall into a clade distinct from that containing KIVs isolated from respiratory secretions, respiratory tissue and feces. Moreover, four positively selected sites (4.5% of t-Ag sites) were found under strong positive selection (omega=11.4), with posterior probabilities above 0.99. All the sites were located in the N-terminal region of the small t antigen.

Conclusions: The results suggest that the novel KI and WU polyomaviruses can infect human tonsils. Future studies are needed to define their role in tonsil diseases.