Modification of PCV-2 virulence by substitution of the genogroup motif of the capsid protein

Allemandou, Aude; Grasland, Béatrice; Hernandez-Nignol, Anne-Cécile; Kéranflec'h, André; Cariolet, Roland; Jestin, André

Detection of viral genomes in the control groups 1 and 2 remained negative throughout the trial (data not shown). Viral genomes were detected first in the group 4 (PCV-2b) at 14 dpt in all piglets, with an average of 10 6.8 genome copies/mL of serum ( Figure 2B) . Then, the load remains constant until the end of the trial. In the group 3 (PCV-2a) and group 6 (PCV-2b/motif 2a), genomic viral loads were detected in all piglets at 14 dpt with mean of 10 6.8 genome copies/mL of serum in group 3 and of 10 6 copies/mL in group 6 ( Figure 2A and 2D). Compared to the group 4 (PCV-2b), the expression of the viral genome decreased more rapidly in the PCV-2b/motif 2a and PCV-2a groups (p < 0.05 with the PCV-2b group). In the group 3 (PCV-2a), three pigs positive in sera became negative at the end of the trial for the detection of viral genomes. In the group 6 (PCV-2b/motif 2a), two pigs were negative at 21 dpt and until the end and another pig presented no genomic load in serum at the end. In group 5, no genomic viral load was detected in any piglet inoculated with the PCV-2a/motif 2b mutant ( Figure 2C ) (p < 0.05 with the three other transfected groups).