Porcine circovirus type 2 (PCV2) is a major causal agent of post-weaning multisystemic
wasting syndrome in piglets. To investigate the feasibility of PCV2 expressing an exogenous
epitope, a 14-amino-acid V5
epitope derived from simian
parainfluenza virus type 5, was inserted into the C terminus of the
capsid protein. Recombinant PCV2 expressing the V5
epitope, recPCV2/CL-V5, was rescued by transfecting an infectious clone into PK-15 cells and was characterised by an immunoperoxidase monolayer assay (IPMA), a serum neutralisation assay (SNA), a capture
enzyme-linked
immunosorbent assay (ELISA) and immunoelectron microscopy. The V5
epitope was detected in the recombinant marker virus by IPMA and capture ELISA. Furthermore, there was no detectable difference in the antigenicity of the recombinant marker virus compared with the parental virus by IPMA and SNA using PCV2-positive serum and the neutralising
monoclonal antibody 1D2. However, recPCV2/CL-V5 marker virus could be differentiated from the parental virus by PCR, IPMA and capture ELISA. The recombinant marker virus was stable on multiplication through 10 passages in PK-15 cells, with a maximum titre of 10(6.25) 50% tissue culture infective dose (TCID(50))/ml. BALB/c mice were inoculated with the recombinant or parental virus via the intranasal and intraperitoneal routes. The parental and recombinant viruses both could replicate in mice, cause microscopic pathological changes, and induce mice to generate anti-PCV2
antibodies. Furthermore, the recombinant marker virus could also induce anti-V5
epitope tag
antibodies. These results indicated that V5
epitope could be displayed on the surface of the
capsid protein by inserting its gene just before stop
codon of open reading frame 2. More importantly, insertion of the V5
epitope did not seem to interfere with biological characterisation of the recPCV2/CL-V5 marker virus.