Differential recognition of ORF2 protein from type 1 and type 2 porcine circoviruses and identification of immunorelevant epitopes

Two types of porcine circovirus (PCV) have been isolated and are referred t o as PCV1 and PCV2, PCV1 represents an apathogenic virus, whereas PCV2 is a ssociated with post-weaning multisystemic wasting syndrome. The two PCVs ar e related, since they display about 70% identity based on nucleotide sequen ces. In order to discriminate between common and type-specific antigens, an immunocytological approach was used following transfections with cloned ci rcovirus DNAs, as well as recombinant proteins expressed by either baculovi rus or plasmid vectors. The ORF1-encoded proteins in the two viruses were s hown to be antigenically related, whereas the ORF2 proteins were recognized differentially by polyclonal anti-PCV2 antibodies. Furthermore, PEPSCAN an alysis performed on overlapping fragments of the genes encoding part of ORF 1 and the entire ORF2 and ORF3 led to the identification of five dominant i mmunoreactive areas, one located on ORF1 and four on ORF2, However, only so me ORF2 peptides proved to be immunorelevant epitopes for virus type discri mination. The potential use of ORF2-derived antigens as diagnostic tools is demonstrated.