Strain-Dependent Porcine Circovirus Type 2 (PCV2) Entry and Replication in T-Lymphoblasts

Area of Science:

• Veterinary Virology
• Immunology
• Cell Biology

Background:

• Porcine circovirus type 2 (PCV2) causes PCV2-associated diseases (PCVAD) in pigs, characterized by lymphocyte depletion.
• PCV2 targets lymphoblasts, but its infection cycle in these cells remains poorly understood.
• Understanding PCV2-T-lymphoblast interactions is crucial for controlling PCVAD.

Purpose of the Study:

• To investigate the replication cycle of PCV2 strains (1121 and Stoon1010) in T-lymphoblasts.
• To elucidate the mechanisms of PCV2 attachment, entry, and disassembly in T-lymphoblasts.
• To compare the infectivity and characteristics of different PCV2 strains in T-lymphoblasts.

Main Methods:

• Cultured T-lymphoblasts were infected with PCV2 strains 1121 and Stoon1010.
• Viral attachment, internalization, Rep and Cap gene expression, and progeny virus production were assessed.
• Chondroitin sulfate (CS) involvement was studied using enzymatic removal; entry mechanisms were investigated using pharmacological inhibitors and endocytosis pathway blockers.

Main Results:

• Both PCV2 strains expressed Rep and Cap genes; only Stoon1010 produced progeny virus.
• PCV2 attached to and was internalized by T-lymphoblasts; CS was identified as a partial attachment factor.
• PCV2 entry involved clathrin-mediated endocytosis, requiring endosome acidification and serine proteases; strain Stoon1010 exhibited enhanced binding and infectivity.

Conclusions:

• PCV2 infects T-lymphoblasts via clathrin-mediated endocytosis, with partial dependence on chondroitin sulfate.
• Viral disassembly requires endosomal acidification and serine proteases.
• The Stoon1010 strain demonstrates evolutionary advantages over strain 1121, including enhanced binding, receptor-mediated endocytosis, and higher infectivity.