The severity of infectious bursal disease in White Leghorn inbred chicken lines is associated with greater bursal inflammation in vivo and more rapid induction of pro-inflammatory responses following ex vivo stimulation of primary bursal cells.

Transcriptomics analysis reveals that severity of infectious bursal disease in White Leghorn inbred chicken lines is associated with greater bursal inflammation in vivo and more rapid induction of pro-inflammatory responses following ex vivo stimulation of primary bursal cells. In order to better understand differences in the outcome of infectious bursal disease virus (IBDV) infection, we inoculated very virulent (vv) IBDV into White Leghorn chickens from inbred line W that previously had over 24% mortality, and three inbred lines (15I, C.B4 and O) that previously had 0% mortality. Within each experimental group, some individuals experienced more severe disease than others but line 15I birds experienced milder disease based on average clinical scores, percentage of birds with gross pathology, average bursal lesion scores and average peak bursal virus titre. RNA-Seq analysis revealed that more severe disease was associated with a significant up-regulation of pathways involved in inflammation, cytoskeletal regulation by Rho GTPase, nicotinic acetylcholine receptor signaling, and Wnt signaling in the bursa. Primary bursal cells cultured from line W birds and stimulated ex vivo with LPS had a more rapid up-regulation of pro-inflammatory gene expression than cells from line 15I birds, and line W birds had a significantly greater percentage of KUL01+ macrophage cells in the BF than line 15I birds. We hypothesize that a more rapid induction of pro-inflammatory cytokine responses in line W birds causes excessive inflammation and clinical disease following IBDV infection compared to line 15I, and we suggest that pro-inflammatory pathways could be targeted to engineer more disease resistant birds in the future Overall design: A comparison of the transcriptomic responses in the bursa of Fabricius from four birds from the "susceptible" White Leghorn inbred line W and six birds from the "resistant" line 15, following IBDV infection, and a comparison of the transcriptomic reponses in the bursa of Fabricius from six birds with a "high" clinical score (1 x line W, 1 x line 15, 2 x line C and 2 x line O) and six birds with a "low" clinical score (1 x line W, 1 x line 15, 2 x line C and 2 x line O) following IBDV infection