THE EXPRESSED L1 PROTEINS OF HPV-1, HPV-6 AND HPV-11 DISPLAY TYPE-SPECIFIC EPITOPES WITH NATIVE CONFORMATION AND REACTIVITY WITH NEUTRALIZING AND NONNEUTRALIZING ANTIBODIES

Previous studies demonstrated that the human papillomavirus (HPV) type 1 L1 protein, expressed in cos cells by an SV40-based vector, display s conformational epitopes characteristic of native virions. In this st udy, we analyzed the expression of HPV-1, HPV-6, and HPV-11 L1 protein s in order to determine the forms of conformational epitopes expressed by recombinant L1 proteins. Using both immunofluorescence and immunop recipitation techniques, polyclonal and monoclonal antibodies (MAbs) g enerated against native HPV-11 virions reacted with expressed L1 prote ins of HPV-6 and/or HPV-11, but not HPV-1. Similarly, polyclonal antib odies and MAbs generated against HPV-1 virions reacted with the expres sed L1 protein of HPV-1, but not HPV-6 or HPV-11. Of two MAbs that neu tralized HPV-11 infection of murine fetal foreskin xenografts, one rea cted with the expressed L1 protein of both HPV-6 and HPV-11, and the o ther reacted with HPV-11 only. A nonneutralizing conformationally depe ndent MAb reacted with the expressed L1 protein of both HPV-6 and HPV- 11. These results demonstrate that expressed HPV L1 proteins retain ty pe-specific, neutralizing, and nonneutralizing conformational epitopes and that cos cells may be utilized to evaluate host immune responses to such epitopes.