Identification of an amino acid domain encoded by the capsid gene of porcine circovirus type 2 that modulates intracellular viral protein distribution during replication.

Previous work showed that distinct amino acid motifs are encoded by the Rep, Cap and ORF3 genes of two subgroups of porcine circoviruses (PCV), PCV2a and PCV2b. At a specific location of the gene, a certain amino acid residue or sequence is preferred. Specifically, two amino acid domains located in the capsid protein, designated motif-1 (six residues located at positions 86-91) and motif-2 (four residues at positions 190-191-206-210), have been identified to associate with either PCV2a (motif-1a:T(N)KI(S)I and motif-2a:SRKD) or PCV2b (motif-1b:S(N)PR(S)V and motif-2b:AGIE) preferentially. In this study, the protein distribution pattern of a PCV2a isolate and a PCV2b isolate was examined. Each virus exhibited a different viral protein pattern during replication in porcine kidney cells and the viral protein distribution pattern was associated with amino acid motif-2 but not motif-1. The results also showed that a more robust accumulation of viral proteins in the nucleus was associated with motif-2b than with motif-2a. In addition, viruses containing motif-2b replicated better than viruses containing motif-2a in porcine kidney cells.