Characterization of the capsid protein VP2 gene of a virulent strain NE/09 of porcine parvovirus isolated in China

A virulent strain NE/09 of porcine parvovirus (PPV) was isolated from mummified swine fetus samples in China and its capsid protein VP2 gene was analyzed. The data showed that the VP2 gene encompassed an open reading frame of 1713 nucleotides with a composition of 684 adenine (39.9%), 387 cytosine (22.6%), 268 guanine (15.7%), and 374 thymine (21.8%). The VP2 gene encoded a 570aa-long protein which could be recognized by anti-PPV-VP2 monoclonal antibody 3C9. Sequence analysis revealed that the VP2 gene of PPV-NE/09 had close sequence similarity with the VP2 gene of other PPV strains. However, a 27 nucleotide region that encodes a glycine-rich domain at the N-terminal region of VP2 was deleted in the PPV-NE/09 strain. The PPV-NE/09 virions were purified by 1.39 g/ml CsCl density centrifugation and subjected to SDS–PAGE analysis. The results showed that only two major polypeptides VP1 and VP2 with molecular weights of 83 and 64 kDa, respectively were observed, whereas VP3 with a molecular weight of 60 kDa was not present, in contrast to the PPV-NADL-2 strain. According to the phylogenetic relationship of the VP2 gene of PPV-NE/09, the isolate was a new mutant strain of PPV prevailing in China.