PROJECT SUMMARY/ABSTRACT Human Papillomaviruses (HPV) cause 5% of human cancers. While there are effective prophylactic HPV vaccines, their poor uptake in the US, their inaccessibility in many parts of the world where these cancers are most frequent, and the fact they do not eliminate pre-existing persistent infections that can lead to cancer, and they do not treat the resulting cancers, requires that we continue advancing studies on these important human tumor viruses. During the current, highly productive funding period for this R35 (58 publications) we made many, important, new insights that shed light on how papillomaviruses (PV) i) evade host immunity to establish persistent infections that lead to cancer, ii) how this same mechanism contributes to resistance to immunotherapy in mice and humans, iii) how estrogen alters systemic and host immunity to drive persistent PV infections and PV-induced disease, iv) that PV-induced cancers arise from epithelial progenitor cells, v) that PVs alter the microbiome, and vi) the role of host genes in PV-associated cancers. Many of these studies arose through our broad study of a recently discovered mouse papillomavirus (MmuPV1) that we and others have demonstrated induces the same range of cancers caused by HPVs in humans, is sexually transmitted as with HPVs that cause cancer, and shows a similar propensity and mechanism of integration into the host genome, as seen with HPVs, while other studies made use of our first and new, second-generation HPV transgenic mouse models. We also made important new gains to our knowledge of Merkel cell polyomavirus and its role in human cancer, and we contributed to numerous collaborative studies with other leading labs in the field of tumor virology. The competitive renewal application of this R35 builds extensively on these important gains in knowledge. Broadly, our proposed studies are focused on three general directions of study: 1) understanding the role of host immunity in papillomaviral pathogenesis; 2) characterizing MmuPV1-induced cancers and their relevance to HPV-related cancer; and 3) defining the interplay between the microbiome and papillomavirus-induced disease. The R35 mechanism has allowed my research program to pursue many new avenues of research that have yielded significant, field-altering discoveries. We will apply and build upon these discoveries in our future research directions of this competitive renewal. We will leverage our expertise in animal model development and innovative, state-of-the-art approaches to pursue experiments aimed at answering many of the new questions raised by our studies over the current funding period. In the process, I will continue to train the next generation of scientists, as demonstrated by the fact that three trainees during the current funding period took faculty positions at highly ranked universities across the US. I am excited to be nominated by the Dean of the University of Wisconsin School of Medicine and Publi...