豬生殖與呼吸綜合症病毒和豬第二型環狀病毒混和接種豬隻後其類鐸接受體變化

Expression profiles of Toll-like receptor mRNA in pigs co-infected with porcine reproductive and respiratory syndrome virus and porcine circovirus type 2

涂邦彥(Pang-Yan Tu)

指導教授 ： 鍾文彬

國立屏東科技大學/農學院/獸醫學系所/碩士(2014年)

https://doi.org/10.6346/NPUST.2014.00161

摘要

許多研究報告指出，豬生殖與呼吸綜合症病毒 ( PRRSV ) 和豬第二型環狀病毒 ( PCV2 ) 混和接種模式在不同試驗間其接種成功率程度不一。本試驗建立穩定之 PRRSV 與 PCV2 接種模式。合計26隻SPF豬隻隨機分為4 組，於 6 週齡時分別接種PRRSV、PCV2或以上2種病毒。豬隻於6、7、8及9週齡測量體重與體溫並採集血液進行各項檢測。於9週齡時進行剖檢，評估肉眼與組織病理學病變，並進行分子生物學及類鐸接受體 ( TLR ) 變化分析。混和接種豬隻於病毒接種後其平均日增重及體溫皆與對照組具顯著差異 ( P<0.05 )。混和接種組豬隻不論肉眼與鏡下皆可見較嚴重之肺炎與淋巴流失病變，並在淋巴結中可見葡萄串狀嗜鹼性質內包涵體，多數豬隻血清皆可檢測出接種的PRRSV 及PCV2。混和感染PCV2與PRRSV豬隻則較單獨感染者呈現更嚴重的臨床症狀與病變。混和感染PCV2與PRRSV之豬隻其TLR4及8表現量上升且呈現正向之協同作用；TLR3、7及9表現量則下降且呈現負向之協同作用。另外，混和接種組的PCV2或PRRSV 核酸量都比單獨接種組高，顯示混和感染會更抑制抗病毒的TLR族群清除病毒的作用。以上結果顯示本試驗已成功建立穩定之豬隻PRRSV及PCV2混和接種模式並分析出TLR表現量變化與致病機轉關係，可作為往後開發疫苗之動物接種模式之用。

關鍵字

豬第二型環狀病毒 ； 豬生殖與呼吸綜合症病毒 ； 接種模式 ； 類鐸接受體

並列摘要

The establishment of challenge models of combined infection of pigs with porcine reproductive and respiratory syndrome virus ( PRRSV ) and porcine circovirus type 2 ( PCV2 ) have been shown with various successfulness in many studies conducted before. In this study, a consistent challenge model of combined infection of PRRSV and PCV2 in pigs was established. Twenty six, 5-week-old, cesarean-derived, specific-pathogen-free ( SPF ) pigs were obtained from the primary SPF pig unit of Animal Technology Institute Taiwan. Pigs were randomly assigned to four groups with 6 or 7 pigs each. Pigs were mock-infected, or infected with PCV2, PRRSV or in a combination at the age of 6 weeks. The pigs were monitored for respiratory syndromes, and the weight and rectal temperatures were measured at the ages of 6, 7, 8 and 9 weeks. Blood samples were collected from all pigs prior to the inoculation of pathogens and weekly thereafter, and were necropsied at the age of 9 weeks. During the necropsies, lung, tracheobronchial lymph nodes, mesentery lymph nodes, inguinal lymph nodes and spleens were collected for further examinations. To understand the interaction mechanisms between the two pathogens in pigs, the expression of Toll-like receptors ( TLRs ) 2, 3, 4, 7, 8 and 9 mRNA in peripheral blood mononuclear cells ( PBMCs ) were analyzed. Results showed that there were significant ( P< 0.05 ) decreases in mean body weights and increases in rectal temperatures in PRRSV-infected and co-infected pigs as compared with those of mock-infected and PCV2-infected pigs. The co-infected pigs had the highest levels of gross and microscopic lesions including the interstitial pneumonia and lymphoid depletion, with occasionally observed basophilic inclusion bodies in lymphoid tissues. The challenged viruses were detected in the sera of most pigs inoculated with PCV2 or PRRSV. PCV2 loads in sera were significantly ( P< 0.05 ) higher in co-infected pigs than those of PCV2-infected pigs, revealing that PRRSV infection enhances PCV2 replication. Overall, co-infection of PRRSV and PCV2 in pigs induced more severe clinical signs and lesions, and higher PCV2 loadings as compared with those of pigs infected with PRRSV or PCV2 alone. A positively synergistic effect on the TLR4 and 8 mRNA expressions, and a negatively synergistic effect on the TLR3, 7 and 9 mRNA expressions were observed in pigs co-infected with PRRSV and PCV2. Results implicated that the combined infections of pigs with PRRSV and PCV2 might modulate the TLR mRNA expressions and subsequently impair the innate immune responses and induce severe clinical signs. The challenge model and information about the Toll-like receptor ( TLR ) expression in PRRSV and PCV2 infected pigs can be used as a valuable tool for the designing and developing of PRRSV and PCV2 bivalent vaccine in the future.

並列關鍵字

porcine circovirus type 2 ； porcine reproductive and respiratory syndrome virus ； challenge model ； Toll-like receptor

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