Kinetics of the immune response toEimeria maximain relatively resistant and susceptible chicken lines

Abstract

AbstractEimeria maximais a common cause of coccidiosis in chickens, a disease which has a huge economic impact on poultry production. Knowledge of immunity toE. maximaand the specific mechanisms that contribute to differing levels of resistance observed between chicken breeds and between congenic lines derived from a single breed of chickens is required. This study aimed to define differences in the kinetics of the immune response of two inbred lines of White Leghorn chickens that exhibit differential resistance (line C.B12) or susceptibility (line 15I) to infection byE. maxima. Line C.B12 and 15I chickens were infected withE. maximaand transcriptome analysis of infected jejunal tissue was carried out at 2, 4, 6 and 8 days post-infection (dpi). RNA-Seq analysis revealed differences in the rapidity and magnitude of cytokine transcription responses post-infection between the two lines. In particular, IFN-γ and IL-10 transcripts in the jejunum accumulated earlier in line C.B12 (at 4 dpi) compared to line 15I (at 6 dpi). Line C.B12 chickens exhibited increases ofIFNGandIL10mRNA in the jejunum at 4 dpi, whereas in line 15I transcription was delayed but increased to a greater extent. RT-qPCR and ELISAs confirmed the results of the transcriptomic study. Higher serum IL-10 correlated strongly with higherE. maximareplication in line 15I compared to line C.B12 chickens. Overall, the findings suggest early induction of the IFN-γ and IL-10 responses, as well as immune-related genes at 4 dpi identified by RNA-Seq, may be key to resistance toE. maxima.