Until a few years ago, only two human polyomaviruses (JC and BK) were known to infect humans and cause severe illness in immunocompromised hosts. Since 2007, at least eleven new polyomaviruses... Show moreUntil a few years ago, only two human polyomaviruses (JC and BK) were known to infect humans and cause severe illness in immunocompromised hosts. Since 2007, at least eleven new polyomaviruses became known that infect humans. Among them is the polyomavirus associated with trichodysplasia spinulosa (TSPyV). In Chapter 1 of this dissertation, the main focus is on the recent developments in studying the newly identified human polyomaviruses until mid-2014. This introductory chapter sets the stage for further investigation into TSPyV infection, pathogenesis, evolution and host adaptation, which is detailed in Chapter 2. To study causality between TSPyV infection and TS disease, in Chapter 3, the prevalence, load and localization of this virus is described. In Chapter 4, the cellular mechanisms behind disruption of cellular proliferation and TS spicule formation by TSPyV Large T-antigen is investigated. By In-silico analysis, in Chapter 5, the identification of a polyomavirus evolution and adaptation mechanism called COCO-VA is highlighted. Subsequently, in Chapter 6, TSPyV genome sequences are tested to gain more insight into this COCO-VA mechanism. Finally, in Chapter 7, the findings described in this dissertation are discussed with regard to several TSPyV aspects, and compared to existing knowledge about polyomaviruses in a broader context. Show less