Abstract: The sequence analysis indicated that PCV2 SD2 (DQ478947) included 11 opening reading frames at least and some opening reading frames were different from other isolated strains. A pair of primers were designed according to the PCV2 sequence published on GenBank to amplify gene ORF3 of PCV2, the predict fragment size respectively was 209 bp. At 12, 24, 36, 48 hours post-PCV2 infection, total RNA was extracted from viral cell culture using Trizol reagent and treated with DNase I to eliminate the remained virus DNA. mRNA was separated by acetyl cellulose. ORF 3 were amplified by RT-PCR. Results showed the amplified fragments size matched the estimate increase the fragment size totally, the sequence result indicated that the increased fragments and the corresponding sequences in PCV2 SD2 (DQ478947) were identical. Thus, the ORF3 gene of PCV2 SD2 isolate could express at the level of transcription after 24 hours post-infection.

Key words: PCV2; ORF3 gene; transcription analysis