Abstract:

【Objective】 In order to obtain the valuable evidence of pathogenic mechanism and clinical diagnosis about PCV2 infection, the dynamic changes of acute phase proteins (APPs) concentration in serum and APPs expression in liver were studied in piglets infected with PCV2. 【Method】Nineteen conventional piglets without antibodies against PCV2, obtained from a farrow-to-finish farm and certified as having a health status, were divided into control group and challenge group, at randomly. Their blood and liver tissues were collected at different days post-inoculation (DPI) of PCV2. The dynamic changes in concentration of APPs were detected by ELISA, and its mRNA expression in liver were evaluated using fluorescence quantitative RT-PCR, respectively. The histopathological changes of liver lesions were also observed. 【Result】 After PCV2 infection, there were variable degrees of pathological lesions of parenchymal cells in livers, vacuolar degeneration in hepatocytes, proliferation of connective tissue in perilobuler area, and variable degrees of eosinophilic granulocyte infiltration in the perilobular and parenchymal area. The maximum values of pig-main acute phase protein (pig-MAP) were reached on 7 DPI, a significant increase with respect to the serum concentrations before infection (0 DPI)(P＜0.05), and the values were gradually recovered to baseline after 14 DPI. Serum amyloid A (SAA) concentration had a significant increase on 7 and 21 DPI compared to the pre-infection (P＜0.05). Apolipoprotein-AⅠ (ApoA-Ⅰ) was significantly increased on 21 DPI (P＜0.05). There was an increasable tendency of haptoglobin (HP), C-reactive protein (CRP), alpha-1 acid glycoprotein (AGP) and SAA mRNA on 21 DPI. 【Conclusion】 The main histopathological lesions of liver were hepatocytes degeneration and necrosis, connective tissue proliferation in piglets infected with PCV2. The APPs showed different levels in concentration in serum and expression profile in livers. Among them, Pig-MAP could be a valuable marker for monitoring the course of PCV2 infection and prognosis.

Key words: piglet, liver, porcine circovirus type 2 (PCV2), acute phase proteins