Evidence for antigenic determinants shared by the structural polypeptides of (Shope) rabbit papillomavirus and human papillomavirus type 1.

In contrast to antivirion antisera raised against (Shope) rabbit papillomavirus (RPV) and human plantar wart papillomavirus (HPV-1), sera of rabbits bearing Vx7 carcinoma, a transplantable tumor deriving from a RPV-induced papilloma, permit the detection of an antigenic relationship between these viruses. Sera containing anti-RPV antibodies were collected between the 116th and 165th transplant from 10 rabbits selected for their large intramuscular tumors of long duration or for their purposely grafted tumors (both intramuscularly and intraperitoneally). When tested by immunofluorescence using plantar wart sections, seven of these sera detected an antigen whose location corresponds to that of HPV-1 capsid antigens. The reactivity of fluorescein-conjugated IgG, obtained from the most cross-reactive serum, was abolished by incubation with alkali-disrupted HPV-1 virions but not with intact HPV-1 particles. In contrast to an anti-HPV-1 virion antiserum, this Vx7 serum reacted with the main HPV-1 structural polypeptide (MW, 54,000) after SDS disruption and iodination of HPV-1 particles, as shown by radioimmunoprecipitation. Furthermore, one of the two anti-disrupted HPV-1 virion antisera and the two-anti-HPV-1 polypeptide antisera studied reacted with RPV antigens, as shown by immunofluorescence using cottontail rabbit wart sections. Moreover, one of the cross-reactive Vx7 sera gave a precipitin line continuous to that given by an anti-HPV-1 virion antiserum when tested by immunodiffusion using HPV-1 virions as antigens. This was further observed for four of the 110 additional Vx7 sera tested. The specificity of this reaction was confirmed by immune electron microscopy experiments. Similarly, an anti-HPV-1 polypeptide antiserum reacted with RPV virions. The results indicate the existence of two kinds of antigenic determinants shared by RPV and HPV-1 structural polypeptides; some are masked in intact particles and others are located on the virion surface but in a form usually unable to elicit the formation of antibodies.