Dogs play a central role in laboratory medicine, ranging from studies of toxicology and pharmacokinetics to genetic therapy and bone marrow transplantation. Emerging papillomavirus infections and the tumors that they induce are increasingly complicating the study of immunosuppressed dogs. Defective immune responses in dogs are primarily the consequence of studying new drugs for treating dermatologic, neurologic and immunologic diseases. In addition, pioneering experiments on bone marrow transplantation also interfere with normal host immunity and make dogs susceptible to papillomavirus infection. To address this issue, we propose to identify the canine papillomaviruses responsible for these infections, to evaluate the time at which dogs are infected, and to develop prophylactic vaccines. The ultimate goal of our studies is to develop vaccines that will allow investigators to carry out medical research without being compromised by serious papillomavirus infections.