Rab1b-GBF1-ARF1 Secretory Pathway Axis Is Required for Birnavirus Replication

Area of Science:

• Virology
• Molecular Biology
• Cell Biology

Background:

• Birnaviruses, including Infectious Bursal Disease Virus (IBDV), cause significant economic losses in poultry and aquaculture.
• IBDV is a nonenveloped virus with a segmented double-stranded RNA (dsRNA) genome, known for causing immunosuppression in poultry.
• Previous studies showed IBDV utilizes the endocytic pathway and associates replication complexes with the Golgi complex (GC).

Purpose of the Study:

• To investigate how IBDV reorganizes the Golgi complex (GC) for viral replication.
• To identify key host cell proteins and pathways essential for IBDV replication.
• To elucidate the role of the Rab1b-GBF1-ARF1 axis in IBDV-induced intracellular trafficking and replication.

Main Methods:

• Analyzing viral replication in cells with manipulated Rab1b expression (mutant or knockdown).
• Assessing viral progeny yield after inhibiting Golgi-specific Brefeldin A resistance 1 (GBF1) activity using Brefeldin A (BFA) or Golgicide A (GCA).
• Evaluating IBDV infection in cells overexpressing an ADP-ribosylation factor 1 (ARF1) dominant-negative mutant.

Main Results:

• IBDV reorganizes the Golgi complex (GC) for replication complex localization without impairing its secretory function.
• Rab1b is essential for IBDV replication; its depletion or mutation significantly reduces infectious viral progeny.
• Inhibition of GBF1 or ARF1 activity, or overexpression of ARF1 dominant-negative mutant, hampers IBDV replication.

Conclusions:

• IBDV replication critically depends on the Rab1b-GBF1-ARF1 signaling axis for intracellular trafficking.
• These findings reveal a novel mechanism of birnavirus-host cell interaction and Golgi complex manipulation.
• The study supports the hypothesis of birnaviruses as evolutionary links between +ssRNA and dsRNA viruses, highlighting GBF1's role.