Evolution and persistence mechanisms of mouse hepatitis virus

Area of Science:

• Virology
• Molecular Biology
• Cell Biology

Background:

• Understanding viral persistence is crucial for developing effective treatments.
• Mouse hepatitis virus (MHV) is a model coronavirus that can establish persistent infections.
• The molecular mechanisms underlying MHV persistence are not fully understood.

Purpose of the Study:

• To establish and characterize persistently infected DBT cells with MHV.
• To investigate the molecular mechanisms of MHV persistence and evolution in vitro.
• To identify genetic factors associated with MHV persistence.

Main Methods:

• Establishment and characterization of persistently infected DBT cells.
• Analysis of viral mRNA and double-stranded RNA (RF RNA) levels.
• Assessment of viral RNA synthesis rates and relative molar ratios.
• Sequencing and analysis of MHV leader RNA and 5' untranslated region (UTR).

Main Results:

• Viral mRNA and RF RNA were coordinately reduced by approximately 70% in persistent infection compared to acute infection.
• Reduced viral RNA synthesis was attributed to lower levels of transcriptionally active RNAs.
• MHV leader RNA and leader/body junction sequences remained stable during persistence.
• A significant association was found between MHV persistence and an A to G mutation at nucleotide 77 in the 5' UTR of the genomic RNA.

Conclusions:

• MHV persistence is characterized by reduced viral RNA synthesis.
• Intraleader open reading frames (ORFs) and mutations are not essential for MHV persistence.
• A specific mutation in the 5' UTR is strongly associated with MHV persistence, suggesting its role in viral adaptation.