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

On the other hand, difference in virulence could also be observed between isolates of the same PCV-2a genogroup [30] . Indeed, two PCV-2a isolates (Genbank accession numbers DQ397521 and AF264042) exhibited differences in microlesions, in genomic viral loads in sera and in seroconversion. The conclusion stated that the AF264042 strain was more virulent than the other one even if the AF264042 PCV-2a induced sub-clinical infections [30, 31] . These two strains presented nine amino acids difference in their Cap proteins and two in their Rep proteins. A study has also demonstrated that only two amino acid differences in the Cap protein at positions 110 and 191 led to difference in PCV-2 virulence in vivo [32] . In our study, the Cap proteins of PCV-2a and PCV-2b had twenty amino acid differences ( Figure 4 ) and the Rep proteins one amino acid (at position 32). The two parental Cap proteins differed by their motif specific of the genogroup but also in amino acids 59, 75, 131, 206 and 232 that were amino acid changes between the two PCV-2a DQ397521 and AF264042 that previously showed differences in virulence [31] . Here the two parental clone Cap also displayed a change in amino acid 191 that was one of the amino acid found responsible for virulence attenuation [32] . Thus there were several differences that could be involved in the different characteristics of PCV-2a and PCV-2b.