Breed Differences in PCV2 Uptake and Disintegration in Porcine Monocytes

Area of Science:

• Veterinary Virology
• Immunology
• Swine Health

Background:

• Porcine circovirus type 2 (PCV2) causes significant disease (PCVADs) in pigs, with severity varying by breed.
• The role of monocytes in PCV2 infection and breed-specific susceptibility remains unclear.
• Understanding PCV2 interaction with monocytes is crucial for disease management.

Purpose of the Study:

• To investigate PCV2 entry mechanisms into primary porcine monocytes.
• To compare PCV2 uptake and intracellular fate across different pig breeds.
• To elucidate the role of monocytes in PCV2 genetic susceptibility.

Main Methods:

• Analysis of PCV2 uptake and trafficking in monocytes from Piétrain, Landrace, Large White, and hybrid pigs.
• Inhibition studies using chlorpromazine, cytochalasin D, and dynasore to identify entry pathways.
• In vitro assessment of viral genome integrity using lysosomal DNase II.

Main Results:

• PCV2 is rapidly internalized into monocytes via clathrin-mediated endocytosis.
• Internalized capsids undergo partial disintegration within the endosomal-lysosomal pathway.
• Monocytes from Piétrain and hybrid pigs exhibited higher PCV2 uptake and disintegration compared to Landrace and Large White.
• Viral genomes largely escape lysosomal degradation in vivo.

Conclusions:

• PCV2 entry into porcine monocytes is primarily mediated by clathrin-dependent endocytosis.
• Significant breed-associated differences exist in PCV2 monocyte interaction and viral processing.
• Monocyte responses to PCV2 vary, contributing to differential genetic susceptibility to PCVADs.