Infectious human papillomavirus type 18 pseudovirions

Area of Science:

• Molecular Virology
• Viral Vector Technology
• Gene Therapy

Background:

• Human papillomavirus (HPV) capsid proteins L1 and L2 assemble into virus-like particles (VLPs).
• Previous studies suggest HPV particle formation and DNA encapsidation are specific processes.

Purpose of the Study:

• To investigate the ability of HPV18 L1 and L2 proteins to encapsidate non-viral DNA.
• To determine if HPV DNA sequences or replication are necessary for encapsidation.
• To explore the role of L2 in the DNA packaging mechanism.

Main Methods:

• Synthesis of HPV18 L1 and L2 proteins using recombinant vaccinia viral vectors.
• Transfection of 293T cells with plasmid DNA and infection with vaccinia vectors.
• Analysis of DNA encapsidation into HPV-like particles using various reporter genes.
• Testing pseudovirion infectivity in different cell types.

Main Results:

• Plasmid DNA (5.4–7.9 kb) was successfully encapsidated into HPV-like particles.
• Pseudovirions containing beta-galactosidase or puromycin resistance genes were infectious, transferring genetic material.
• Encapsidation occurred independently of HPV DNA sequences and T antigen-mediated replication.
• The minor capsid protein L2, not L1 alone, was implicated in DNA binding and encapsidation.

Conclusions:

• HPV18 L1 and L2 proteins can package intracellular episomal DNA of suitable size without specific HPV packaging signals.
• The L2 protein plays a crucial role in the DNA encapsidation process.
• This mechanism allows for the reintroduction of cellular DNA into new cells via pseudovirions.