Effects Of PCV2 Infection On The Transcription Levels Of Pattern Recognition Receptors Of Porcine Pulmonary Alveolar Macrophages In Vivo

Porcine circovirus type 2 (PCV2) is the primary aetiological agent of postweaning multisystemic wasting syndrome (PMWS) that is an important emerging disease in swine. It cause immunosuppression in the infected pigs. Its target organ and cells are the lung and pulmonary alveolar macrophages (PAM). The objective of this study is to analyze the effect of PCV2 infection on the innate immunity of PAMs at the molecular level by the change of the mRNAs transcription of pattern recognition receptor(PRR) of the PAMs from piglets postinnoculated with PCV2 at different days.Partial gene fragments of PRR including TLR2, TLR4, CD 16, CD 18 andβ-actin were amplified by RT-PCR or PCR from PAM and cloned into pGEM-T easy vector and their recombinant standard plasmids were acquired. The standard curves and regression equations of TLR2,TLR4, CD 16, CD 18 andβ-actin were required respectively by real-time fluorescent quantitative PCR, and their related indexes (r2) were more than 0.99.Twenty-four forty-day-old healthy piglets were divided into control group and infected group. After innoculated PCV2 B1 strain intranasally, pulmonary alveolar macrophages (PAM) from the infected piglets were collected on days 3,7,14 and 28.Real-time FQ-PCR was used to detect the kinetics of PRR mRNA of PAM. The study results showed that the transcriptions of TRL2 mRNA were increased, TRL4 and CD 16 mRNA increased with significant levels, but CD 18 decreased with significant levels at 3DPI; the transcriptions of TRL2, TRL4 and CD16 mRNA were increased at 7 DPI with no significant differences, and CD 18 increased with significant levels at 7DPI; the transcriptions of TRL2, TRL4 and CD16 mRNA were decreased at 14 DPI, but only TRL2 decreased with significant levels, except the levels of CD18 mRNA; the transcriptions of TRL2, TRL4,CD16 and CD18 mRNA were near to the that of the contol. All these results implied that the PRR mRNA of PAM could be disorder, which implied the change of the functions of phagocytosis of foreign body identification and signal transduction of PAM during the infection period, and the influence on its abilities of phagocytosis and clearance of pathogenic microorganisms.