Coronaviruses as vectors: stability of foreign gene expression

Area of Science:

• Virology
• Molecular Biology
• Vaccine Development

Background:

• Coronaviruses are enveloped, positive-stranded RNA viruses.
• They show potential as vaccine vectors due to gene deletion, tropism modification, and heterologous gene expression.
• Genetic stability is crucial for live viral vectors, but poorly understood for recombinant coronaviruses.

Purpose of the Study:

• To investigate the genetic stability of foreign genes (Renilla and firefly luciferase) within recombinant coronaviruses.
• To determine factors influencing the stability of these genes at different genomic positions.
• To compare the stability of Renilla versus firefly luciferase genes in distinct coronavirus backgrounds.

Main Methods:

• Insertion of Renilla and firefly luciferase genes at various genomic locations in feline infectious peritonitis virus (group 1) and mouse hepatitis virus (group 2).
• Systematic analysis of gene expression and genetic integrity over time.
• Comparison of gene stability based on gene type, genomic location, and coronavirus species.

Main Results:

• The Renilla luciferase gene demonstrated greater intrinsic stability than the firefly luciferase gene.
• Loss of firefly luciferase expression was linked to deletions, likely via RNA recombination.
• Gene stability was influenced by the coronavirus genomic background (feline vs. mouse) and insertion site.
• Foreign sequences were more stable when replacing nonessential viral genes.

Conclusions:

• Intrinsic properties of the foreign gene significantly impact its stability in recombinant coronaviruses.
• RNA recombination is a key mechanism for foreign gene instability in these vectors.
• Optimizing insertion site and selecting appropriate foreign genes are critical for developing stable coronavirus-based vaccine vectors.