Characterization of a human papillomavirus type 16 variant-dependent neutralizing epitope

Area of Science:

• Virology
• Immunology
• Structural Biology

Background:

• Human papillomavirus type 16 (HPV16) is a major cause of cervical cancer.
• Monoclonal antibodies are crucial tools for studying viral neutralization.
• Understanding HPV16 variant neutralization is important for vaccine and therapeutic development.

Purpose of the Study:

• To investigate the neutralizing capabilities of three specific monoclonal antibodies (H16.E70, H16.U4, H16.V5) against HPV16 pseudotype virions.
• To characterize the differential neutralization activity of these antibodies against different HPV16 variants.
• To identify the structural basis for antibody-epitope interactions in HPV16.

Main Methods:

• In vitro neutralization assays using pseudotype HPV16 virions.
• Enzyme-linked immunosorbent assays (ELISA) to assess antibody binding to L1 virus-like particles (VLPs).
• Comparative analysis of antibody reactivity against HPV16 variants with known sequence differences.

Main Results:

• Monoclonal antibodies H16.U4 and H16.V5 demonstrated equal neutralization efficiency against German (114K) and Zairian (Z-1194) HPV16 variants.
• Antibody H16.E70 exhibited significantly weaker neutralization (two orders of magnitude) against the Zairian variant (Z-1194) compared to the German variant (114K).
• Differential reactivity of H16.E70 correlated with its binding to L1 VLPs from the two variants, pinpointing a substitution at residue 282 of L1 as the cause.

Conclusions:

• The neutralizing activity of monoclonal antibodies against HPV16 can be variant-specific.
• A single amino acid substitution at residue 282 in the HPV16 L1 protein significantly impacts the binding and neutralization efficacy of antibody H16.E70.
• This residue is likely a critical component of the H16.E70 epitope, highlighting the conformational dependence of antibody recognition.