The Susceptibility of Swine Lymphocytes to Porcine Circovirus Type Ⅱ

• Main Authors: Chun-Ming Lin, 林俊明
• Other Authors: Victor Fei Pang
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/33139713521888108081

碩士 === 國立臺灣大學 === 獸醫學研究所 === 94 === The porcine circovirus type Ⅱ (PCV2)-associated newly emerged disease, postweaning multisystemic wasting syndrome (PMWS), is characterized by lymphoid depletion in lymphoid organs and replacement by macrophages. Until now, whether PCV2 replicates in immune system and the pathogenesis of PMWS are still not well understood. In this study, we established a model of PCV2 infection in mitogen-treated peripheral blood lymphocytes (PBL). In the first part of the study, it was demonstrated that there was only 0.1% of PCV2 antigen-containing rate in PBL isolated from PCV2-free pigs and treated simultaneously with mitogen and PCV2. The results of both MTT assay and blastogenesis indicated that PCV2 could reduce the responsiveness of PBL to mitogen stimulation, but the results of survival and apoptotic rates indicated that PCV2 had no effects on the viability of PBL. In the second part of study, it was found PCV2 nucleic acid and antigens could be more easily detected in mitogen-stimulated PBL from clinically healthy PCV2-carrier pigs by in situ hybridization and immunofluorescence analysis, respectively. After 4 days of mitogen treatment, the PCV2 antigen-containing rate in PBL could reach 20% with IgM-positive cells predominant. The mitogen-stimulated PBL had higher PCV2 titer. Additionally, PCV2 ORF1-associated protein was usually present perinuclearly or within the nuclei; ORF2-associated protein was chiefly restricted in the cytoplasm; the expression of ORF1-associated protein, but not ORF2, as well matched with TUNEL signal. Results of this study indicate that PBL are indeed susceptible to PCV2 infection and PCV2 is capable to replicate in dividing lymphocytes. This replication may play a role on PCV2-induced apoptosis in PBL. The result may explain in part the pathogenesis of PMWS.