Optimizing a Human Papillomavirus Type 16 L1-Based Chimaeric Gene for Expression in Plants.

Area of Science:

• Molecular Biology
• Vaccine Development
• Plant Biotechnology

Background:

• Human papillomaviruses (HPVs) cause cervical cancer, necessitating effective vaccines.
• Current HPV vaccines, based on L1 virus-like particles (VLPs), are costly and target specific types.
• The L2 protein offers potential for broader cross-neutralizing antibody responses, but requires optimized expression systems.

Purpose of the Study:

• To investigate the impact of codon optimization and increased G+C content on HPV L1/L2 gene expression in plants.
• To evaluate the role of the 5' region of the L1 gene in regulating protein expression.
• To enhance the production of HPV VLPs for more affordable and broadly protective vaccines.

Main Methods:

• Synthetic L1/L2 genes were created with varying G+C content and human codon optimization.
• The 5' region of the L1 gene was modified by replacing parts with its wild-type sequence.
• Protein and mRNA levels were quantified in plant expression systems.

Main Results:

• Increased G+C content in L1/L2 genes led to a 10-fold increase in mRNA and 3-fold increase in protein levels.
• Human codon-optimized genes with high G+C content resulted in a 100-fold mRNA increase and 8-9 fold protein increase.
• Restoring the wild-type 5' L1 sequence reduced both mRNA and protein expression.

Conclusions:

• Codon optimization and high G+C content significantly enhance HPV L1/L2 protein expression in plants.
• The 5' region of the L1 gene contains negative regulatory elements that can be disrupted by codon optimization.
• These findings support the development of cost-effective, plant-produced HPV vaccines with broader protection.