Humoral assays of human sera to disrupted and nondisrupted epitopes of human papillomavirus type 1.

The use of different assay systems and the disparity in results obtained has meant that we have little understanding about the role played by the humoral response during human papillomavirus (HPV) infection. Human antibody responses have so far appeared to be largely directed against the major capsid protein, L1. This protein possesses both type-specific and type-common antigenic determinants but it is not known which of these is important in vivo during the natural course of infection. In this study humoral responses of 83 individuals to purified HPV 1 virions were tested in three types of antibody assay. Western blot analysis detected antibodies in only eight of the serum samples, whereas an enzyme-linked immunosorbent assay (ELISA) and immunoprecipitation assay using nondisrupted HPV 1 virions showed positive antibody reactivities for 71 and 64 individuals, respectively. We suggest from these results that the humoral response to L1 is mainly directed against native conformational epitopes present on the whole HPV 1 particle and that type-common epitopes are not largely involved. This was further demonstrated by the fact that when samples were tested in the same ELISA system using disrupted HPV 1 virions as the antigen instead of whole virus particles, the number of positive sera was reduced to 9 out of 83. We further conclude that humoral assays using antigenic material pertaining to disrupted HPV epitopes are of limited use, at least in the case of HPV type 1. There were no obvious correlations between the antibody assay results and clinical histories of wart infection except that a lower number of positive serum reactivities were found among the group of individuals claiming to have no past history of HPV infection.