Effect Of ChTLR3 Signal Transduction In Bursa Immune Injury In IBDV-infected Chickens

In order to discuss the effect of chTLR3 signal transduction in immuno lesion of bursa in IBDV-infected chickens, seventy-five 14-day-old specific pathogen free( SPF)allocated into 3groups averagely which infected, vaccine group and control group. Three groups of chickens were housed in separate isolators. The infected group was infected IBDV standard strain by the intraocular and intranasal route, 0.6ml per chicken. Vaccine group was inoculated IBDV live vaccine, 2 plume per chicken, and control group was treated by PBS, 0.6ml per chicken by the same way. At 1, 4, 7, 21 and 35 days post-infection, five chickens were executed by drawing-out all the blood in their hearts and bursas were collected and stored at-80℃. Bursal cells were examined by RT-PCR for expression changes of chTLR3, chTLR3 signal transduction pathway associated molecule(chMy D88, chTRIF and chNF-κB)and cytokines(chTNF-α, chIL-1β, chIL-6,chIFN-β)mRNA and by indirect immunofluorescence assay for expression of chTLR3 protein and changes of T, B lymphocytes and macrophage count.The results showed that the expression of chTLR3 mRNA and protein of bursas in infected and vaccine groups all showed uptrend firstly and then declined. Their peak values appeared at 4day post-infection or post-vaccination(P<0.01 or P<0.05). These results indicated that chTLR3 involved in the process of chickens resisting the IBDV. The mRNA expressions of chTLR3 signal pathway associated molecular were all significantly higher than control group(P<0.01 or P<0.05) during early stage of infection. Their peak values appeared at 4 day post-infection, and descend gradually. In addition, results revealed that chMy D88 mRNA expression risen slowly and time sustained shuorter than that of chTRIF. It suggested that the primary adaptor protein of chTLR3 signal transduction pathway is chTRIF. The expression changes of cytokines mRNA were similar with that of chTLR3 signal pathway associated molecular of bursas in infected and vaccine groups. The changes showed that values ascended firstly and then descend.Adaptive immunity relevant indexes results showed that T lymphocytes count of bursas in infected group risen gradually and this difference remained significantly(P<0.01)at 1-7days post-infection, but it significantly lower than control group(P<0.05)at 21 day post-infection.Though it rising at 35 day post-infection, still significantly lower than control group(P<0.05).The number of T lymphocytes in vaccine group risen at 1 day post-vaccination, and reached peak at 4 day(P<0.05)post-vaccination, and then declined gradually. At 21 day post-vaccination the index got right(P>0.05). These results indicated that the expression changes of cytokines mRNA and the number of T lymphocytes all presented rising trend in the early stage. The number of Blymphocytes in infected group significantly lower than control group( P < 0.01) at 1 day post-infection and the difference lasted. Though it risen at 21 day post-infection, still significantly lower than control group(P<0.01), then recovered gradually. The number of B lymphocytes in vaccine group significantly lower than control group at 1-7 days post-vaccination(P<0.05), but it presented rising trend in the whole process. The result showed that cytokines(excepting IFN-β)and the number of B lymphocytes all presented rising trend in the later stage. Above-mentioned results showed that chTLR3 could induce cellular immunity in the early stage and induce humoral immunity in the later stage by cytokines.In addition, the number of macrophage in infected group chickens were significantly higher than that of control group(P<0.01 or P<0.05)at 1-7 days post-infected. At 21 day post-infected,the index was significantly lower than that of control group(P<0.05)and got right at 35 day post-infected. The number of macrophage in vaccine group chickens ascended in the early stage and then descend in the latter stage. The results showed that expression of chTLR3, the number of macrophage and T lymphocytes all increased suggesting that chTLR3 could activate cellular immunity indirectly by activating macrophage during the early stage.This study proved that chTLR3 played a critical role in process of IBDV infecting chickens and chickens resisting virus, from gene and protein level. ChTLR3 regulating adapted immunity by activating cytokines and macrophage demonstrated that chTLR3 is a bridge connecting innate immunity and adapted immunity ulteriorly. It provided scientific trial basis for researching the effect of pattern recognition receptor in the process of resisting virus and provided new though for controlling IBD.