Conditional cytomegalovirus replication in vitro and in vivo

Area of Science:

• Virology
• Molecular Biology
• Genetics

Background:

• Cytomegalovirus (CMV) infection is a significant concern, particularly in immunocompromised individuals.
• Studying viral gene function is crucial for understanding pathogenesis and developing antiviral strategies.
• Existing methods for studying CMV gene expression are often limited by their dependence on viral replication.

Purpose of the Study:

• To establish a novel conditional gene expression system for murine cytomegalovirus (MCMV).
• To enable independent regulation of viral genes, separate from the viral replication cycle.
• To facilitate genetic studies of large DNA viruses.

Main Methods:

• Development of a self-sufficient tetracycline-regulated expression cassette.
• Utilized Flp recombinase-mediated insertion into the MCMV genome.
• Constructed recombinant MCMVs carrying conditional genes, including reporter genes, essential M50, and a dominant-negative mutant (m48.2).
• Analyzed gene regulation in vitro and in vivo.

Main Results:

• Conditional expression of the essential M50 gene regulated viral growth by three orders of magnitude in vitro.
• Conditional expression of the dominant-negative small capsid protein mutant (m48.2) inhibited viral growth up to a millionfold in vitro.
• In vivo, doxycycline administration reduced viral growth of the dominant-negative mutant to detectable limits in mouse organs.

Conclusions:

• The developed conditional gene expression system offers precise control over viral gene function.
• This system is applicable to studying the roles of specific genes in MCMV infection.
• The approach is potentially transferable to genetic studies of other large DNA viruses.