The 6th amino acid mutation of Rep protein had no effect on PCV2b but
enhanced PCV2d virus replication in vitro
Abstract
Porcine circovirus type 2 (PCV2) is the etiological agent that primary
cause of post-weaning multisystemic wasting syndrome (PMWS). The major
genotypes, PCV2a, PCV2b and PCV2d, are highly prevalent, but now
replaced with 2b and 2d in swine population in worldwide. Rep protein is
the key protein for viral replication. Compared a large number of Rep
protein amino acid (aa) sequences, we found that there were three sites
with regular changes between 2b and 2d.In order to analyze the effect of
key sites on viral replication, we used site-directed mutagenesis to
mutate the 6th aa of Rep (alternations with asparagine and serine)
between PCV2b and PCV2d, Two wild-type and two mutant viruses infectious
clones were rescued by non-contaminated porcine kidney-15 (PK-15) cells.
Real-time quantitative PCR and a one-step growth curve were used to
determine viral load to assess the replication of rescued viruses. The
results showed that there was no significant difference between the
PCV2b mutation and the wild-type PCV2b virus in vitro, while the
mutation ofPCV2d enhanced viral replication.