HPV-16 E1, E2 and E6 each complement the Ad5 helper gene set, increasing rAAV2 and wt AAV2 production

Area of Science:

• Molecular Biology
• Virology
• Gene Therapy

Background:

• Adeno-associated virus type 2 (AAV) is a key vector in gene therapy due to its safety and long-term gene expression capabilities.
• Large-scale production of recombinant AAV (rAAV) is hindered by low particle yields.
• While adenovirus (Ad) helper genes are well-established, human papillomavirus (HPV) helper genes for AAV production are less explored.

Purpose of the Study:

• To investigate the potential of HPV-16 E1, E2, and E6 genes as helper genes for rAAV production in HEK293 cells.
• To assess the effect of HPV genes on AAV DNA replication and virus particle yield, both alone and in combination with Ad5 helper genes.

Main Methods:

• HEK293 cells were used as the standard cell line for rAAV generation.
• HPV-16 E1, E2, and E6 genes were tested individually and in combination with standard Adenovirus type 5 (Ad5) helper genes.
• Wild-type (wt) AAV DNA replication and virion yield were measured under various conditions, including co-infection with wt Ad5.
• Protein and mRNA levels of AAV rep and cap genes were analyzed.

Main Results:

• Individually, HPV-16 E1, E2, and E6 genes did not significantly stimulate rAAV replication in HEK293 cells.
• Complementation with the Ad5 helper gene set significantly boosted rAAV DNA replication and virus particle yield when E1, E2, or E6 were included.
• Co-infection with wt Ad5 and each HPV gene also significantly increased wt AAV DNA replication and virion yield.
• While rep mRNA was upregulated, cap mRNA showed a greater increase, and higher virus yields correlated with specific viral protein species.

Conclusions:

• HPV helper genes, particularly when combined with Ad5 helper genes, can significantly enhance AAV production.
• The distinct mechanisms of Ad and HPV helper genes suggest potential for creating improved, hybrid helper gene sets.
• This finding opens avenues for optimizing AAV vector production for gene therapy applications.