Identification of alternatively spliced isoforms of interleukin-2/15 receptor β chain in ducks

Evolution of developmental and comparative immunology in poultry: The regulators and the regulated

Avian has a unique immune system that evolved in response to environmental pressures in all aspects of innate and adaptive immune responses, including localized and circulating lymphocytes, diversity of immunoglobulin repertoire, and various cytokines and chemokines. All of these attributes make birds an indispensable vertebrate model for studying the fundamental immunological concepts and comparative immunology. However, research on the immune system in birds lags far behind that of humans, mice, and other agricultural animal species, and limited immune tools have hindered the adequate application of birds as disease models for mammalian systems. An in-depth understanding of the avian immune system relies on the detailed studies of various regulated and regulatory mediators, such as cell surface antigens, cytokines, and chemokines. Here, we review current knowledge centered on the roles of avian cell surface antigens, cytokines, chemokines, and beyond. Moreover, we provide an update on recent progress in this rapidly developing field of study with respect to the availability of immune reagents that will facilitate the study of regulatory and regulated components of poultry immunity. The new information on avian immunity and available immune tools will benefit avian researchers and evolutionary biologists in conducting fundamental and applied research.

Anti-inflammatory activity of diindolylmethane alleviates Riemerella anatipestifer infection in ducks

3,3’-Diindolylmethane (DIM) is found in cruciferous vegetables and is used to treat various inflammatory diseases because of its potential anti-inflammatory effects. To investigate effects of DIM in Riemerella anatipestifer-infected ducks which induce upregulation of inflammatory cytokines, ducks were treated orally with DIM at dose of 200 mg/kg/day and infected the following day with R. anatipestifer. Infected and DIM-treated ducks exhibited 14% increased survival rate and significantly decreased bacterial burden compared to infected untreated ducks. Next, the effect on the expression level of inflammatory cytokines (interleukin [IL]-17A, IL-17F, IL-6, IL-1β) of both in vitro and in vivo DIM-treated groups was monitored by quantitative reverse-transcription PCR (qRT-PCR). Generally, the expression levels of the cytokines were significantly reduced in DIM-treated splenic lymphocytes stimulated with killed R. anatipestifer compared to stimulated untreated splenic lymphocytes. Similarly, the expression levels of the cytokines were significantly reduced in the spleens and livers of DIM-treated R. anatipestifer–infected ducks compared to infected untreated ducks. This study demonstrated the ameliorative effects of DIM in ducks infected with R. anatipestifer. Thus, DIM can potentially be used to prevent and/or treat R. anatipestifer infection via inhibition of inflammatory cytokine expression.

Downregulation of inflammatory cytokines by berberine attenuates Riemerella anatipestifer infection in ducks

Riemerella anatipestifer, an important infectious bacterium affecting the duck industry, has 5-75% mortality, depending on strain virulence. We previously demonstrated that proinflammatory cytokines are involved in inflammation during, and regulating susceptibility to, R. anatipestifer infection. We investigated the effects of the anti-inflammatory compound berberine in duck splenic lymphocytes stimulated with killed R. anatipestifer, and in R. anatipestifer-infected ducks. IL-17A, IL-17F, and IL-1β transcripts were downregulated, and IFN-γ and IL-10 transcripts enhanced, in berberine-treated stimulated splenic lymphocytes, compared to stimulated untreated splenic lymphocytes. Similarly, IL-17A, IL-17F, IL-6, and IL-1β expressions were significantly reduced, and IFN-γ and IL-10 expressions significantly upregulated, in spleens and livers of R. anatipestifer-infected berberine-treated ducks, compared to infected untreated birds. Moreover, infected and treated birds showed increased survival rates and significantly decreased bacterial burdens compared to infected untreated birds, confirming that inflammatory cytokines are strongly associated with R. anatipestifer infection in ducks.

Upregulation of duck interleukin-17A during Riemerella anatipestifer infection

Although IL-17 cytokines play critical roles in host defense immunity, dysregulated expression of these cytokines is associated with inflammation and autoimmune diseases. Riemerella anatipestifer is the most important infectious bacterium in the duck industry. Interestingly, not all avian species are equally susceptible to R. anatipestifer infection. This paper reports the first description of mortality rate, bacterial burden, and expression profiles of immune-related genes between ducks and chickens infected with R. anatipestifer. Ducks exhibited increased susceptibility to R. anatipestifer infection compared to chickens, as determined by mortality rate and bacterial burden. Comparative expression analyses of immune-related genes in R. anatipestifer-infected tissues obtained from both species revealed that TLR3, TLR7, IL-2, IL-4, and IFN-γ transcript levels were higher in chickens, whereas TLR4 and IL-17A transcript levels were higher in ducks. Marked increases in expression of IL-17A and IL-6, but not TGF-β, were associated with Th17 cell differentiation in duck splenic lymphocytes, but not in chicken splenic lymphocytes, stimulated with R. anatipestifer. Moreover, upregulation of IL-1β, IL-6, and IL-17A mRNA expressions, but not TGF-β, was confirmed in the liver and spleen of ducks infected with R. anatipestifer, indicating that IL-17A is strongly associated with Riemerella infection in ducks.

Identification and expression analysis of duck interleukin-17D in Riemerella anatipestifer infection

Interleukin (IL)-17D is a proinflammatory cytokine with currently largely unknown biological functions. Here we provide the description of the sequence, bioactivity, and mRNA expression profile of duck IL-17D homologue. A full-length duck IL-17D (duIL-17D) cDNA with a 624-bp coding region was identified from the large intestine. duIL-17D shares approximately 94.7% identity with its chicken counterpart, which is also identified in this work. duIL-17D exhibits 62.6-68.4% and 52.1-53.1% identity with mammalian and piscine homologues. Recombinant duIL-17D promoted the expression of proinflammatory cytokines such as IL-6, IL-8, and IL-1β in duck embryo fibroblast cells. Very low levels of duIL-17D transcript were observed in healthy lymphoid tissues, including bursa, thymus, and spleen, while duIL-17D expression was relatively high in the heart. The duIL-17D expression profiles were examined in mitogen-stimulated splenic lymphocytes, as well as tissues affected by Riemerella anatipestifer infection. The levels of duIL-17D were mostly upregulated in mitogen-activated splenic lymphocytes but downregulated in the liver and spleen of R. anatipestifer-infected ducks. These results provide new insights into the roles of IL-17D in host protective immune responses to Riemerella infection, which can therefore lead to further studies of its biological functions in different disease models of ducks and other avian species.