HPV-16 L1 Virus-like Particles Research Articles

Surface Conformational and Linear Epitopes on HPV-16 and HPV-18 L1 Virus-like Particles as Defined by Monoclonal Antibodies

A panel of 24 monoclonal antibodies (MAbs) was generated against human papillomavirus (HPV) types 16 and 18 L1 virus-like particles (VLPs). The MAbs were screened for reactivity to a variety of VLPs prepared from HPV-6, -11, -16, -18, -31, -33, -35, and -45, cottontail rabbit papillomavirus, bovine papillomavirus type 1, and a set of 35 overlapping 20-amino-acid peptides spanning the entire HPV-16 L1 gene. Type-specific linear and conformational surface epitopes were detected as well as several cross-reactive linear epitopes that showed various levels of cross-reactivity between different genital HPV and animal papillomavirus L1s. Most of the linear epitopes were mapped using synthetic peptides, and the epitopes were identified as being either surface or buried within the VLP as defined by the pattern of reactivity in ELISA using intact and disrupted VLP antigen. These MAbs may be useful reagents to help define neutralizing epitopes of HPV-16 and -18 when infectivity assays become available, and to define the regions of L1 that are exposed on the surface or buried within the assembled capsid.

Human Papillomavirus Types 6 and 11 Have Antigenically Distinct Strongly Immunogenic Conformationally Dependent Neutralizing Epitopes

Antibodies reactive to HPV types 6 and 11 were tested in ELISA and HPV-11 neutralization assays to determine whether these closely related types shared cross-reactive neutralizing epitopes. A series of HPV-11 neutralizing monoclonal antibodies (N-MAbs) that targeted conformational epitopes on infectious HPV-11 and HPV-11 L1 virus-like particles (VLPs) were tested for type-specificity of reactivity using intact HPV-6 L1 VLPs. Polyclonal antisera generated against intact HPV-6 L1 VLPs were also tested for HPV-11 neutralizing capacity using the athymic mouse xenograft system. The results demonstrated that conformationally dependent neutralizing epitopes on HPV-11 were very type-specific. Three of the four HPV-11 N-MAbs were negative for binding to HPV-6 L1 VLP, and the fourth demonstrated binding to HPV-6 L1 VLPs that was several orders of magnitude weaker than its binding to HPV-11 L1 VLP. The polyclonal anti-HPV-6 L1 VLP antiserum was only partially protective against HPV-11 infectivity even at a low dilution of 1:100. In contrast, polyclonal anti-HPV-11 L1 VLP antiserum was completely protective at dilutions greater than 1:10,000.

Serological differentiation of human papillomavirus types 11, 16 and 18 using recombinant virus-like particles.

The L1 major capsid protein-coding sequences of human papillomavirus (HPV) types 11, 16 and 18 were expressed in the baculovirus system. Virus-like particles (VLPs) were purified from recombinant-infected Spodoptera frugiperda Sf9 cells and cell-free culture supernatants. Rabbits immunized with purified VLPs developed antibodies that reacted only with the specific VLP type used as the immunogen. In addition, rabbit antibodies raised against infectious HPV-11 virions only reacted with HPV-11 L1 VLPs and not with VLPs derived from either HPV-16 or HPV-18. These results suggest that HPV-11, HPV-16 and HPV-18 virions are antigenically distinct from one another. This observation should be considered in future studies of immune responses to HPV.