The effect of zearalenone (ZEN) on swine immunocytes and porcine circovirus type 2 (PCV2) replication

• Main Authors: Cheng Huang, 黃崢
• Other Authors: Victor Fei Pang
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/44580743887716580169

碩士 === 國立臺灣大學 === 分子暨比較病理生物學研究所 === 101 === Porcine circovirus type 2 (PCV2), a single-stranded circular DNA virus, is the primary causative agent of PCV-associated diseases (PCVAD). Aside from PCV2, other factors such as co-infection with other viruses or bacteria and environmental factors also play an important role on PCVAD development. Immunosuppression caused by stress, drug or other environmental factors are suggested to promote PCV2 replication. Mycotoxins are climate dependent, plant- and storage-associated problems. Climate change like global warming represents a key agro-ecosystem driving force of fungal colonization and mycotoxin production. Prolonged low-dose exposure to mycotoxin may lead to the impairment of immunity. Zearalenone (ZEN) and its derivatives, produced by Fusarium spp. and known as non-steroidal, estrogenic mycotoxins, are known to be hepatotoxic, haematotoxic, genotoxic, and immunotoxic. The present study attempted to clarify the possible effects of ZEN on PCV2 replication and functional alterations in peripheral blood mononuclear cells (PBMCs), and the subsets monocyte-derived dendritic cells (DCs) and peripheral blood lymphocytes (PBLs); and to determine whether ZEN is a potential environmental co-factor for PCV2 in PCVAD development. The first part of the study was to incubate PCV2-containing PBMCs and PBLs obtained from healthy, sub-clinically PCV2-infected pigs with ZEN at different concentrations for 24 and 72 h, with or without concanavalin A (Con A) stimulation, to quantify PBMCs viability by flow cytometry. To incubate PBMCs and PBLs with non-lethal 0.01-10 μg/ml ZEN for 24-72 h and 24-120 h, respectively, with or without Con A, to quantify the viral load by real-time PCR. The results showed that there were significant differences in PCV2 load between 1-10 μg/ml ZEN-treated and control group under Con A stimulation, but not in PBLs. The second part of the study was to incubate porcine DCs with 10 μg/ml ZEN for 24 h prior to its co-culture with PBLs, with or without Con A stimulation, for 24, 72 and 120 h, to evaluate the differences in cell proliferation and PCV2 load. The result showed that there was no significant difference between ZEN-treated and control DCs, with or without Con A stimulation, in promoting PBLs proliferation and PCV2 load. The third part of the study was to incubate porcine PBMCs with 0.1-10 μg/ml ZEN, with or without Con A stimulation, for 6-24 h and incubate DCs with different concentrations of ZEN without Con A stimulation for 6-24 h, to evaluate the differences in the expression levels of IL-2 and IL-10 mRNA for PBMCs and IL-12 and IL-10 mRNA for DCs by using real-time PCR. The result showed a significant reduction in IL-2 and IL-10 mRNA expression in ZEN-treated than in control PBMCs at 10 μg/ml ZEN, with or without Con A stimulation; but there was no significant difference in IL-12 and IL-10 mRNA expression between ZEN-treated and control DCs at 0.1-10 μg/ml ZEN without Con A stimulation. In conclusion, the major effect of ZEN was in PBMCs, including significantly elevated PCV2 load and reduced IL-2 and IL-10 mRNA expression at higher but sub-lethal concentrations of ZEN under Con A stimulation. However, no significant effects were revealed in PBLs and DCs. Because PCV2 viral load is important in PCVAD development and under the stimulation of Con A ZEN could increase the PBMCs’ PCV2 viral load, it is thous suggested that ZEN may have the potential to be an environmental co-factor for PCV2 in the induction of PCVAD.