Replication-competent foot-and-mouth disease virus RNAs lacking capsid coding sequences

Area of Science:

• Virology
• Molecular Biology
• Genetics

Background:

• Foot-and-mouth disease virus (FMDV) is a significant pathogen affecting livestock.
• Understanding FMDV RNA replication is crucial for developing control strategies.
• Previous studies suggested the importance of specific genomic regions for FMDV replication.

Purpose of the Study:

• To investigate the role of the leader (Lab and Lb) and capsid protein coding sequences in FMDV RNA replication.
• To identify potential cis-acting replication elements within these regions of the FMDV genome.
• To assess the impact of deletions in these regions on viral RNA replication and particle formation.

Main Methods:

• Construction of FMDV cDNA plasmids with deletions or replacements in the Lb and P1 (capsid precursor) coding sequences.
• Preparation of RNA transcripts from these plasmids.
• Electroporation of transcripts into BHK cells and monitoring of reporter gene (chloramphenicol acetyltransferase - CAT) and viral protease (3C) expression.
• Assessment of RNA replication efficiency and viral encapsidation.

Main Results:

• Expression of CAT and FMDV 3C protease was dependent on RNA replication.
• Deletion of the entire Lb coding sequence and 94% of the P1 capsid protein precursor coding sequence did not affect RNA replication.
• Encapsidation of FMDV replicons was inefficient, potentially explaining the absence of defective-interfering particles.

Conclusions:

• No cis-acting replication element is present within the Lb and P1 coding regions of the FMDV genome.
• The FMDV genome exhibits significant flexibility regarding the Lb and capsid protein coding sequences for RNA replication.
• Inefficient encapsidation may limit the generation of defective-interfering particles in FMDV-infected cells.