Changes of Toll-like Receptor mRNA Transcription in Alveolar Macrophages of Piglets Infected with Porcine Circovirus Type 2

Six conventional piglets free of porcine circovirus type 2(PCV2)and porcine reproductive and respiratory syndrome virus(PRRSV)were used in this experiment as detected by ELISA and fluorescence quantitative PCR.The alveolar macrophages(AMs)were isolated aseptically and divided into two groups,control group and PCV2infection group(PCV2group)and cultured in vitro.The AMs were collected at 0,6,12,24and 48hours post infection(hpi).The amount of PCV2infected cells was observed by indirect immunofluorescence assay(IFA)and the mRNA transcription of TLR2,TLR3,TLR4,TLR7,TLR8and TLR9were detected by real-time PCR. The results show that the mRNA levels of TLR2were significantly higher at 6,12and 24h(hpi)(P0.01or P0.05),then the levels were recovered at 48hpi.The expression of TLR3were significantly elevated at 6and 12hpi(P0.05),and the transcription were then restored at 24 and 48hpi;PCV2stimulation up-regulated the transcriptions of TLR4in AMs at 12hpi(P 0.05)and down-regulated the transcriptions at 24and 48hpi(P0.05);PCV2-infection increased TLR7,TLR8and TLR9transcriptions in AMs at 6and 12hpi(P0.01or P0.05)andtheir of transcriptions were restored at 24and 48hpi.Thus,PCV2can significantly affect TLR2, TLR3,TLR4,TLR7,TLR8and TLR9transcriptions in piglets AMs in vitro.