Effects of recombinant turkey interferon-gamma on development of immunity to coccidia in neonatal turkeys

Abstract

Our interest in gut immunity in commercial poultry led to investigation of the effects of recombinant turkey interferon-gamma (rtIFNγ) on parameters of immunity to avian coccidia. In vitro experiments consisted of exposing baby hamster kidney cells (BHK) to increasing concentrations of rtIFNγ and measuring subsequent Eimeria tenella (ET) sporozoite invasion in short-term culture. In experiment 1 (EXP 1), when BHK were pretreated with rtIFNγ in cell culture medium 45 min prior to the addition of sporozoites to confluent monolayers, ET invasion was significantly reduced. During EXP 2, these reductions were not observed when BHK were pretreated with rtIFNγ for 48 hours prior to sporozoite addition. In vivo investigation consisted of three independent experiments (EXP 3, 4, or 5) over time in which rtIFNγ was administered to turkey poults one day post-hatch by intraperitoneal injection 30 min prior to per os challenge with Eimeria adenoeides (EA). In EXP 4 and 5, neonatal turkeys received a second challenge with EA on day 21 of age to test for potential adjuvant effects of rtIFNγ while immunizing poults with EA by primary challenge. When evaluating body weight gain in the three experiments, improvement in gain following primary challenge was associated (P<.05) with rtIFNγ administration in poults challenged with EA as compared to poults challenged with EA alone in EXP 3 and 4, but not EXP 5. Body weight gain 6 days post-secondary challenge in EXP 4 and 5 was not different between neonatal turkeys receiving rtIFNγ + EA or turkeys receiving EA alone. Similar effects were seen with regard to gross lesion formation. In EXP 3 and 4, protective effects were observed in poults receiving EA + rtIFNγ 6 days post-primary challenge. These positive effects of rtIFNγ administration were not observed following secondary EA challenge in EXP 4 or following either primary or secondary challenge in EXP 5. In EXP 3, 4, and 5, mortality was higher (P<.05) in poults receiving both EA and rtIFNγ when compared to poults receiving EA alone following primary challenge, but not secondary challenge, as significant differences in mortality were not observed in the older animals.