Mutations in human papillomavirus type 16 L1 hypervariable surface-exposed loops affect L2 binding and DNA...

Area of Science:

• Virology
• Immunology
• Structural Biology

Background:

• Prophylactic human papillomavirus (HPV) vaccines utilize virus-like particles (VLPs) to elicit type-specific neutralizing antibodies.
• These antibodies target hypervariable residues on the major capsid protein L1's surface-exposed loops.

Purpose of the Study:

• To investigate the functional significance of specific surface-exposed residues in HPV L1 loops.
• To determine the impact of mutations on neutralization, cross-neutralization, L2 incorporation, and genome encapsidation.

Main Methods:

• Site-directed mutagenesis was employed to alter ten surface-exposed amino acid residues in four hypervariable L1 loops.
• Mutated and wild-type (WT) L1 VLPs, with or without WT L2, were produced in 293TT cells using pseudovirion expression vectors.

Main Results:

• Mutations in L1 loops significantly reduced the induction of neutralizing antibodies.
• L1 mutations impaired L2 protein incorporation into the capsid.
• The ability to induce cross-neutralizing antibodies and encapsidate pseudogenomes was completely lost.

Conclusions:

• Surface-exposed loops of the HPV L1 protein are critical for VLP function.
• These findings underscore the importance of specific L1 residues for vaccine efficacy and viral particle integrity.