Failure to produce warts on human skin grafts on 'nude' mice

Split-thickness human skin was exposed to a suspension of human papilloma virus containing 10(11)-10(12) particles/ml, by immersion for varying lengths of time. It was then grafted onto the backs of congenitally athymic 'nude' mice. All grafts were accepted, but no warts developed during an observation period of up to 9 weeks.