Molecular characterization of porcine parvovirus 1 based on partial VP2 gene in the ovaries of Thai pigs

Abstract

Porcine parvovirus 1 (PPV1) is the causative agent of swine reproductive disease, particularly in naive gilts and sows. This study aimed to investigate the prevalence and genetic diversity of the partial nucleotide sequence of the VP2 gene and to compare the substitution of amino acid residues that affect relevant biological properties. The prevalence of PPV1 was found to be 12% (12/100) when the viral genome was detected using polymerase chain reaction (PCR). Determination of the genetic diversity of a partial nucleotide sequence of the VP2 gene through phylogenetic analysis indicated that a single cluster of Thai PPV1s was allocated on the phylogenetic tree. According to a comparison of the substitution of amino acid residues that affected the biological properties at 378, 383, 365, and 436 of the VP2 capsid protein between the 12 Thai PPV1s, the Kresse strain (a surrogate pathogenic strain), and the NADL-2 strain (a surrogate nonpathogenic strain). It was determined that the substitution of amino acid residues at 378, 383, and 436 of 12 Thai PPV2s was identical to those of the Kresse strains. The substitution of amino acid residues at 436 of the 12 Thai PPV1s was similar to that of a proven virulent strain in vivo. Additionally, substituting amino acid residue at 320 of the VP2 capsid protein revealed that seven Thai PPV1s were associated with isoleucine PPV1s and identical to that of both surrogate strains, whereas five Thai PPV1s were associated with threonine. This outcome was similar to what had been deposited in GenBank. Our data suggest that Thai PPV1s isolated from the ovaries of pigs raised in Chiang Mai may have originated from the Kresse strains. Based on a change of VP2 capsid protein that occurred amongst the substitution amino acid residue at 320 of the VP2 capsid protein, viruses found in this region were determined to be similar to those found in other areas. This was likely because the viruses had adapted to evade the immune systems of animals.