Human papillomavirus type 16 capsids expose multiple type-restricted and type-common antigenic epitopes

Area of Science:

• Virology
• Immunology
• Oncology

Background:

• Human papillomavirus (HPV) infection, particularly HPV-16, is a major cause of cervical cancer.
• Accurate detection of HPV capsid antigens in clinical samples requires knowledge of exposed epitopes.
• Identifying specific antigenic sites on HPV-16 is essential for developing diagnostic and potentially therapeutic strategies.

Purpose of the Study:

• To define the antigenic epitopes present on the L1 and L2 capsid proteins of human papillomavirus type 16 (HPV-16).
• To investigate the surface exposure and cross-reactivity of these epitopes with other HPV types and related viruses.
• To provide foundational data for the development of HPV diagnostics and vaccines.

Main Methods:

• Synthesized 66 overlapping peptides representing HPV-16 L1 and L2 proteins and tested antisera against them.
• Utilized immunoperoxidase staining on formalin-fixed, paraffin-embedded HPV-infected tissue sections.
• Assessed reactivity of antipeptide antisera with intact and disrupted virions/capsids of HPV-11, HPV-16, and bovine papillomavirus (BPV).

Main Results:

• Identified multiple antigenic epitopes on both HPV-16 L1 (11 peptides) and L2 (7 peptides) capsid proteins.
• Found that most epitopes were specific to certain genital HPV types, with some L1 epitopes also present in cutaneous warts.
• Demonstrated significant reactivity of antisera with intact HPV-16 capsids, indicating surface exposure of these epitopes, with varying cross-reactivity to HPV-11 and BPV.

Conclusions:

• HPV-16 L1 and L2 proteins possess multiple antigenic epitopes, many of which are shared among different HPV types.
• The study provides a detailed map of HPV-16 epitopes, crucial for understanding viral structure and antigenicity.
• These findings support the development of type-specific and potentially cross-reactive diagnostic assays for HPV infections.