Research On The Efficacy And Immunity Enhancement Of Recombinant Chicken IFN-γ Against Chicken Coccidiosis

Chicken interferon gamma(ChIFN- ) is an important cytokine. It can exert antiviral activity and a number of immunomodulatory effects such as enhancement of T cell mediated cytoxicity, MHCII expression and macrophage activation. The studies were performed to assess the ability of recombinant chicken IFN- (rChlFN- ) against avian coccidiosis and discover the mechanism of enhancing immunity of coccidial vaccine, whkh is consisted of two parts.In the first part, broilers were injected with rCWFN- at the age of 6 and 7 days with different ways, challenged with 5 104 or 4 104 oocysts of E.tenella at 7 days old. When challenged with 5 X 104 oocysts, broilers injected with rChlFN- Y had the higher relative body weight gain than the infected control broilers, as well as the lower caecum lesion score and OPG. At the same time, broilers injected intramuscularly with 5000U rChlFN- Y had the highest relative body weight gain, which was 75.1%. Moreover, the broilers had the lowest caecum lesion score and OPG, which was 2.2 and 7.8 104 oocysts separately. When broilers challenged with 4 104 oocysts, the similar results were found. Broilers injected with 5000U rChlFN- Y intramuscularly had the highest relative body weight gain, whkh was 93.0%. Moreover, the broilers has the lowest caecum lesion score and OPG, which was 1.8 and 6.6 104 oocysts separately. The results showed that rChlFN- Y could improve relative body weight gain and ACI, alleviate caecum lesion score and reduce oocyst production.The effects of rChlFN- on the vaccine immunity were studied in the second part of our research. The results showed that rChlFN- Y can improve relative body weight gain, the immune organ index, alleviate caecum lesion score of treated broilers. At the same time, it can reduce oocyst production and increase ACI. LPA levels of broilers injected with rChlFN- Y were significantly higher than immunized control broilers. In the first trial, LPA levels of immunized control group is 0.59 and 0.67 at the age of 14 and 21 days old through lymphocyte proliferation assays, whereas LPA levels of group immunized with rChlFN- Y is 0.67 and 0.81 separately. The similar results were observed from the second trial. The increased CD4+,CDg+ T cell of spleen and ceacum were found through the ABC technique in the rChlFN- treated group. The results of Griess response showed that rChlFN- Y can significantlyincrease NO2" leveK a =0.05). At the age of 21 days old, NO2" level of immunized control group is 2.14 ug/ml, whereas the level of group immunized with rChlFN- Y is 2.77 ug/ml. At the same time, we found that rChlFN- y can elevate sera LSZ level. At the age of 14 and 21 days old, LSZ level of immunized control group is 12.55 ug/ml and 19.79 ug/ml separately, whereas the level of the group immunized with rChlFN- y is 14.52 ug/ml and 22.80 ug/ml separately.The results of our research demonstrate that rChlFN- y is an important cytokine which has the ability to inhibit the development of avian coccidia and enhance the protective immunity. rChlFN- y would be an excellent candidate as a therapeutic agent and potential adjuvant for coccodial immunity.