HUMAN PAPILLOMAVIRUS TYPE-16 CAPSIDS EXPOSE MULTIPLE TYPE-RESTRICTED AND TYPE-COMMON ANTIGENIC EPITOPES

The study of viral infectivity and detection of viral capsid antigens of the major cervical cancer-associated human papillomavirus (HPV) typ e, HPV-16, requires knowledge of which epitopes are exposed in clinica l specimens of infected tissue or on intact capsids. To define the ant igenic epitopes of HPV-16, antisera to 66 overlapping synthetic peptid es corresponding to the HPV-16 capsid proteins L1 and L2 and to seven peptide analogues were tested in immunoperoxidase stainings of consecu tive sections from formalin-fixed, paraffin-embedded HPV infected tiss ue. Antisera against eleven different peptides from L1 and against sev en different peptides from L2 recognized the HPV capsid antigen. Most epitopes were only found on the capsid antigen of certain genital HPV types, but four antigenic epitopes in L1 were detectable also in cutan eous wart specimens. All antigenic epitopes in L2 were restricted to g enital HPV types and four L2 epitopes were only detectable in HPV-16 o r HPV-33 positive specimens. The surface exposure of the antigenic epi topes was investigated by comparing the reactivity of the antipeptide antisera with intact or disrupted virions or capsids of HPV-11, HPV-16 and bovine papillomavirus (BPV). Twenty antipeptide sera from L1 and seven antipeptide sera from L2 were reactive with intact HPV-16 capsid s at titres up to 1:146000. Sixteen of these antisera were also reacti ve with disrupted HPV-16 capsids. Cross-reactivity with disrupted HPV- 11 and BPV was detected for eleven and six antisera, respectively, whe reas intact HPV-11 or BPV virions showed only weak cross-reactivity. I n conclusion, the HPV-16 L1 and L2 capsid proteins contained multiple antigenic epitopes, most of which were shared with one or several addi tional HPV types.