Re-evaluation of the chicken MIP family of chemokines and their receptors suggests that CCL5 is the prototypic MIP family chemokine, and that different species have developed different repertoires of both the CC chemokines and their receptors

Enhancement of protective efficacy of recombinant attenuated Salmonella typhimurium delivering H9N2 avian influenza virus hemagglutinins(HA) antigen vaccine candidate strains by C-C motif chemokine ligand 5 in chickens(chCCL5)

The H9N2 inactivated avian influenza vaccine cannot induce cellular and mucosal immune responses, while the attenuated Salmonella vector as an intracellular bacterium can induce dominant cellular and mucosal immune responses. However, it provides low protection against the virus when delivering viral antigens and needs further optimization. Chicken C-C motif chemokine ligand 5 (chCCL5) is an important CC chemokine associated with immune cell chemotaxis, migration, and viral infection. This study connected the sequence of chCCL5 (CCL5) with the hemagglutinin sequence of the H9N2 avian influenza virus (yH9HA), utilizing the attenuated Salmonella typhimurium vector containing the delayed lysis system MazE/F regulated by arabinose as a carrier. A vaccine strain of recombinant attenuated Salmonella typhimurium and H9N2 avian influenza virus HA, rSC0130 (pS0017-yH9HA-CCL5), was successfully constructed. The experimental results indicate that yH9HA-CCL5 can be expressed in 293 T cells; compared to the strain without CCL5, rSC0130 (pS0017-yH9HA-CCL5) can induce significantly increased cellular immune responses and provide better protective effects in H9N2 virus challenge experiments. The above results indicate that chCCL5 can significantly enhance the protective effect of Salmonella delivering H9N2 avian influenza virus HA protein vaccine against H9N2 avian influenza virus infection, providing valuable theoretical support for further improving the protective efficiency of recombinant attenuated Salmonella vectors for delivering viral antigens.

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.

Chicken-Specific Kinome Analysis of Early Host Immune Signaling Pathways in the Cecum of Newly Hatched Chickens Infected With Salmonella enterica Serovar Enteritidis

Poultry is a major source of human foodborne illness caused by broad host range Salmonella serovars (paratyphoid), and developing cost-effective, pre-harvest interventions to reduce these pathogens would be valuable to the industry and consumer. Host responses to infectious agents are often regulated through phosphorylation. However, proteomic mechanisms of Salmonella acute infection biology and host responses to the bacteria have been limited concentrating predominately on the genomic responses of the host to infection. Our recent development of chicken-specific peptide arrays for kinome analysis of host phosphorylation-based cellular signaling responses provided us with the opportunity to develop a more detailed understanding of the early (4-24 h post-infection) host-pathogen interactions during the initial colonization of the cecum by Salmonella. Using the chicken-specific kinomic immune peptide array, biological pathway analysis showed infection with S. Enteritidis increased signaling related to the innate immune response, relative to the non-infected control ceca. Notably, the acute innate immune signaling pathways were characterized by increased peptide phosphorylation (activation) of the Toll-like receptor and NOD-like receptor signaling pathways, the activation of the chemokine signaling pathway, and the activation of the apoptosis signaling pathways. In addition, Salmonella infection induced a dramatic alteration in the phosphorylation events of the JAK-STAT signaling pathway. Lastly, there is also significant activation of the T cell receptor signaling pathway demonstrating the initiation of the acquired immune response to Salmonella infection. Based on the individual phosphorylation events altered by the early Salmonella infection of the cecum, certain conclusions can be drawn: (1) Salmonella was recognized by both TLR and NOD receptors that initiated the innate immune response; (2) activation of the PPRs induced the production of chemokines CXCLi2 (IL-8) and cytokines IL-2, IL-6, IFN-α, and IFN-γ; (3) Salmonella infection targeted the JAK-STAT pathway as a means of evading the host response by targeting the dephosphorylation of JAK1 and TYK2 and STAT1,2,3,4, and 6; (4) apoptosis appears to be a host defense mechanism where the infection with Salmonella induced both the intrinsic and extrinsic apoptotic pathways; and (5) the T cell receptor signaling pathway activates the AP-1 and NF-κB transcription factor cascades, but not NFAT.

Towards Improved Use of Vaccination in the Control of Infectious Bronchitis and Newcastle Disease in Poultry: Understanding the Immunological Mechanisms

Infectious bronchitis (IB) and Newcastle disease (ND) are two important diseases of poultry and have remained a threat to the development of the poultry industry in many parts of the world. The immunology of avian has been well studied and numerous vaccines have been developed against the two viruses. Most of these vaccines are either inactivated vaccines or live attenuated vaccines. Inactivated vaccines induce weak cellular immune responses and require priming with live or other types of vaccines. Advanced technology has been used to produce several types of vaccines that can initiate prime immune responses. However, as a result of rapid genetic variations, the control of these two viral infections through vaccination has remained a challenge. Using various strategies such as combination of live attenuated and inactivated vaccines, development of IB/ND vaccines, use of DNA vaccines and transgenic plant vaccines, the problem is being surmounted. It is hoped that with increasing understanding of the immunological mechanisms in birds that are used in fighting these viruses, a more successful control of the diseases will be achieved. This will go a long way in contributing to global food security and the economic development of many developing countries, given the role of poultry in the attainment of these goals.

Immune Modulation and the Development of Fowl Typhoid: A Model of Human Disease?

Salmonella enterica serovar Gallinarum (S. Gallinarum) is the cause of typhoid in chickens but the immune factors that may facilitate the development of typhoid have not been fully elucidated. We show that, in contrast to non-typhoid S. Enteritidis infection, S. Gallinarum significantly reduced nitrite ion production and expression of mRNA for heterophil granulocyte chemoattractants CXCLi2 and IL-6 in chicken monocyte-derived macrophages (chMDMs) (p < 0.05) at 6 h post-infection (pi). S. Gallinarum also reduced IFN-γ and IL-17 expression by CD4⁺ lymphocytes cultured with infected chMDMs for 5 days but did not induce a Th2 phenotype or anergy. In vivo, S. Gallinarum also induced significantly lower expression of CXCLi1, CXCLi2, IL-1β, IL-6 and iNOS mRNA in the caecal tonsil by day 2 pi (p < 0.05–0.01) and consistently lower levels of IFN-γ, IL-18, IL-12, and IL-17. In the spleen, S. Gallinarum induced significantly lower levels of iNOS and IFN-γ (p < 0.01 and 0.05 respectively) and consistently lower levels of IL-18 and IL-12 but significantly greater (p < 0.01) expression of anti-inflammatory IL-10 at day 4 and 5 pi when compared to S. Enteritidis. This immune phenotype was associated with transit from the intestinal tissues to the liver by S. Gallinarum, not observed following S. Enteritidis infection. In conclusion, we report an immune mechanism that may facilitate typhoid disease in S. Gallinarum-infected chickens. However, down-regulation of inflammatory mediators, upregulation of IL-10, and associated liver colonisation are also characteristic of human typhoid, suggesting that this may also be a useful model of typhoid in humans.

Characterisation of Listeria monocytogenes isolates from cattle using a bovine caruncular epithelial cell model

Listeria monocytogenes is an important foodborne pathogen in human and veterinary health, causing significant morbidity and mortality including abortion. It has a particular tropism for the gravid uterus, however, the route of infection in reproductive tissues of ruminants (i.e. placentome), is much less clear. In this study, we aimed to investigate a bovine caruncular epithelial cell (BCEC) line as a model for L. monocytogenes infection of the bovine reproductive tract. The BCEC infection model was used to assess the ability of 14 different L. monocytogenes isolates to infect these cells. Lysozyme sensitivity and bacterial survival in 580 μg lysozyme/ml correlated with attenuated ability to proliferate in BCEC (p = 0.004 and p = 0.02, respectively). Four isolates were significantly attenuated compared to the control strain 10403S. One of these strains (AR008) showed evidence of compromised cell wall leading to increased sensitivity to ß-lactam antibiotics, and another (7644) had compromised cell membrane integrity leading to increased sensitivity to cationic peptides. Whole genome sequencing followed by Multi Locus Sequence Type analysis identified that five invasive isolates had the same sequence type, ST59, despite originating from three different clinical conditions. Virulence gene analysis showed that the attenuated isolate LM4 was lacking two virulence genes (uhpT, virR) known to be involved in intracellular growth and virulence.

In conclusion, the BCEC model was able to differentiate between the infective potential of different isolates. Moreover, resistance to lysozyme correlated with the ability to invade and replicate within BCEC, suggesting co-selection for surviving challenging environments as the abomasum.

Model of Persistent Salmonella Infection: Salmonella enterica Serovar Pullorum Modulates the Immune Response of the Chicken from a Th17-Type Response towards a Th2-Type Response

Salmonella enterica infection affects a wide range of animals and humans, and a small number of serovars cause typhoid-like infections, one characteristic of which is persistent infection in convalescents. Avian-specific S. enterica serovar Pullorum produces systemic disease in young chickens, which is followed by a carrier state in convalescent birds, leading to infection of the ovary at sexual maturity and vertical transmission. However, the immunological basis of persistent infection remains unclear. S. enterica serovar Enteritidis is taxonomically closely related but does not show this characteristic. Differences in the immune responses between S Pullorum and S Enteritidis were compared by using Salmonella-infected chicken monocyte-derived macrophages (chMDMs) and CD4⁺ T lymphocytes that had been cocultured with infected chMDMs or chicken splenocytes in vitro and also in 2-day-old chickens in vivo In comparison with S Enteritidis, S Pullorum-infected chMDMs showed reduced mRNA expression levels of interleukin-12α (IL-12α) and IL-18 and stimulated the proliferation of Th2 lymphocytes, with reduced expression of gamma interferon (IFN-γ) and IL-17 and increased expression levels of IL-4 and IL-13 There was little evidence of clonal anergy or immune suppression induced by S Pullorum in vitro. S Pullorum also increased the levels of expression of IL-4 and decreased the levels of IFN-γ in the spleen and cecal tonsil of infected birds. This suggests that S Pullorum is able to modulate host immunity from a dominant IFN-γ-producing Th17 response toward a Th2 response, which may promote persistent infection in chickens. S Pullorum in chickens is presented as a good model of the typhoid group to study persistent infection.

Protective Effect of Melatonin on LPS-stimulated Granulosa Cells in Japanese Quail

The aim of this study was to evaluate the potential of melatonin to protect cultured granulosa cells from the harmful effects of lipopolysaccharide (LPS) in quail. Granulosa cells isolated from Japanese quails were pretreated with or without melatonin (10 or 100 µg/mL) for 12 hand then incubated for 12 hin the absence or presence of 100 ng/mL LPS. The expression of pro-inflammatory cytokines and chemokine was detected by quantitative real-time PCR. The levels of oxidative stress biomarkers (dityrosine and nitrite) were determined by ELISA and the Griess reaction. Cell viability was quantified using an MTT assay. Additionally, the level of progesterone was measured by ELISA. We found that melatonin decreased LPS-induced expression of IL-1β, IL-6, and IL-8. In addition, melatonin increased the dityrosine level, but suppressed the nitrite level. Finally, melatonin administration increased the viability of LPS-stimulated granulosa cells in vitro. However, progesterone basal secretion was not significantly changed. These results suggest that melatonin protects cultured granulosa cells from LPS-induced inflammatory and oxidative stress damage and provide evidence that melatonin might have therapeutic utility in ovarian follicle infection in Japanese quail.

Physiological responses of cultured bovine granulosa cells to elevated temperatures under low and high oxygen in the presence of different concentrations of melatonin

Our understanding of the effects of temperature on granulosa cell (GC) physiology is primarily limited to in vitro studies conducted under atmospheric (∼20% O₂) conditions. In the current series of factorial experiments we identify important effects of O₂ level (i.e. 5% vs 20% O₂) on GC viability and steroidogenesis, and go onto report effects of standard (37.5 °C) vs high (40.0 °C) temperatures under more physiologically representative (i.e. 5%) O₂ levels in the presence of different levels of melatonin (0, 20, 200 and 2000 pg/ml); a potent free-radical scavenger and abundant molecule within the ovarian follicle. Cells aspirated from antral (4-6 mm) follicles were cultured in fibronectin-coated wells using serum-free M199 for up to 144 h. At 37.5 °C viable cell number was enhanced and luteinization reduced under 5 vs 20% O₂. Oxygen level interacted (P < 0.001) with time in culture to affect aromatase activity and cell estradiol (E₂) production (pg/mL/10⁵ cells). These decreased between 48 and 96 h for both O₂ levels but increased again by 144 h for cells cultured under 5% but not 20% O₂. Progesterone (P₄) concentration (ng/mL/10⁵ cells) was greater (P < 0.001) under 20 vs 5% O₂ at 96 and 144 h. Cell number increased (P < 0.01) with time in culture under 5% O₂ irrespective of temperature. However, higher doses of melatonin increased viable cell number at 40.0 °C but reduced viable cell number at 37.5 °C (P = 0.004). Melatonin also reduced (P < 0.001) ROS generation at both O₂ levels across all concentrations. E₂ increased with time in culture at both temperatures under 5% O₂, however P₄ declined between 96 and 144 h at 40.0 but not 37.5 °C. Furthermore, melatonin interacted (P < 0.001) with temperature in a dose dependent manner to increase P₄ at 37.5 °C but to reduce P₄ at 40.0 °C. Transcript expression for HSD3B1 paralleled temporal changes in P₄ production, and those for HBA were greater at 5% than 20% O₂, suggesting that hemoglobin synthesis is responsive to changes in O₂ level. In conclusion, 5% O₂ enhances GC proliferation and reduces luteinization. Elevated temperatures under 5% O₂ reduce GC proliferation and P₄ production. Melatonin reduces ROS generation irrespective of O₂ level and temperature, but interacts with temperature in a dose dependent manner to influence GC proliferation and luteinization.

A distinct bacterial dysbiosis associated skin inflammation in ovine footrot

Ovine footrot is a highly prevalent bacterial disease caused by Dichelobacter nodosus and characterised by the separation of the hoof horn from the underlying skin. The role of innate immune molecules and other bacterial communities in the development of footrot lesions remains unclear. This study shows a significant association between the high expression of IL1β and high D. nodosus load in footrot samples. Investigation of the microbial population identified distinct bacterial populations in the different disease stages and also depending on the level of inflammation. Treponema (34%), Mycoplasma (29%) and Porphyromonas (15%) were the most abundant genera associated with high levels of inflammation in footrot. In contrast, Acinetobacter (25%), Corynebacteria (17%) and Flavobacterium (17%) were the most abundant genera associated with high levels of inflammation in healthy feet. This demonstrates for the first time there is a distinct microbial community associated with footrot and high cytokine expression.

Cytokine activation during embryonic development and in hen ovary and vagina during reproductive age and Salmonella infection

Salmonellosis is one of the most important zoonotic diseases and is usually associated with consumption of Salmonella Enteritidis (SE) contaminated poultry meat or eggs. Contamination with SE is usually the result of infection of the digestive tract, or reproductive organs, especially the ovary and vagina. Thus, knowledge of endogenous innate immune mechanisms operating in the ovary and vagina of hen is an emerging aspect of reproductive physiology. Cytokines are key factors for triggering the immune response and inflammation in chicken to Salmonella infection. The aim of this study was to investigate the expression profile of 11 proinflammatory cytokines in the chicken embryos during embryonic development, as well as in the hen ovary and vagina in vivo, to investigate whether sexual maturation affects their ovarian and vaginal mRNA abundance and to determine whether cytokine expression was constitutive or induced in the ovary and vagina as a response to SE infection. RT-PCR analysis revealed that several cytokines were expressed in the chicken embryos, and in the ovary and vagina of healthy birds. Expression of various cytokines during sexual maturation appeared to be developmentally regulated. In addition, a significant up-regulation of several cytokines in the ovary and vagina of sexually mature SE infected birds compared to healthy birds of the same age was observed. These results suggest a cytokine-mediated immune response mechanism against Salmonella infection in the hen reproductive organs.

The development and maintenance of the mononuclear phagocyte system of the chick is controlled by signals from the macrophage colony-stimulating factor receptor

BACKGROUND

Macrophages have many functions in development and homeostasis as well as innate immunity. Recent studies in mammals suggest that cells arising in the yolk sac give rise to self-renewing macrophage populations that persist in adult tissues. Macrophage proliferation and differentiation is controlled by macrophage colony-stimulating factor (CSF1) and interleukin 34 (IL34), both agonists of the CSF1 receptor (CSF1R). In the current manuscript we describe the origin, function and regulation of macrophages, and the role of CSF1R signaling during embryonic development, using the chick as a model.

RESULTS

Based upon RNA-sequencing comparison to bone marrow-derived macrophages grown in CSF1, we show that embryonic macrophages contribute around 2% of the total embryo RNA in day 7 chick embryos, and have similar gene expression profiles to bone marrow-derived macrophages. To explore the origins of embryonic and adult macrophages, we injected Hamburger-Hamilton stage 16 to 17 chick embryos with either yolk sac-derived blood cells, or bone marrow cells from EGFP+ donors. In both cases, the transferred cells gave rise to large numbers of EGFP+ tissue macrophages in the embryo. In the case of the yolk sac, these cells were not retained in hatched birds. Conversely, bone marrow EGFP+ cells gave rise to tissue macrophages in all organs of adult birds, and regenerated CSF1-responsive marrow macrophage progenitors. Surprisingly, they did not contribute to any other hematopoietic lineage. To explore the role of CSF1 further, we injected embryonic or hatchling CSF1R-reporter transgenic birds with a novel chicken CSF1-Fc conjugate. In both cases, the treatment produced a large increase in macrophage numbers in all tissues examined. There were no apparent adverse effects of chicken CSF1-Fc on embryonic or post-hatch development, but there was an unexpected increase in bone density in the treated hatchlings.

CONCLUSIONS

The data indicate that the yolk sac is not the major source of macrophages in adult birds, and that there is a macrophage-restricted, self-renewing progenitor cell in bone marrow. CSF1R is demonstrated to be limiting for macrophage development during development in ovo and post-hatch. The chicken provides a novel and tractable model to study the development of the mononuclear phagocyte system and CSF1R signaling.

Differential expression of Toll-like receptors and inflammatory cytokines in ovine interdigital dermatitis and footrot

Footrot is a common inflammatory bacterial disease affecting the health and welfare of sheep worldwide. The pathogenesis of footrot is complex and multifactorial. The primary causal pathogen is the anaerobic bacterium Dichelobacter nodosus, with Fusobacterium necrophorum also shown to play a key role in disease. Since immune-mediated pathology is implicated, the aim of this research was to investigate the role of the host response in interdigital dermatitis (ID) and footrot. We compared the expression of Toll-like receptors (TLRs) and pro-inflammatory cytokines and the histological appearance of clinically normal in comparison to ID and footrot affected tissues. Severe ID and footrot were characterised by significantly increased transcript levels of pro-inflammatory cytokines TNFα and IL1β and the pattern recognition receptors TLR2 and TLR4 in the interdigital skin. This was reflected in the histopathological appearance, with ID and footrot presenting progressive chronic-active pododermatitis with a mixed lymphocytic and neutrophilic infiltration, gradually increasing from a mild form in clinically normal feet, to moderate in ID and to a focally severe form with frequent areas of purulence in footrot. Stimulation with F. necrophorum and/or D. nodosus extracts demonstrated that dermal fibroblasts, the resident cell type of the dermis, also contribute to the inflammatory response to footrot bacteria by increased expression of TNFα, IL1β and TLR2. Overall, ID and footrot lead to a local inflammatory response given that expression levels of TLRs and IL1β were dependent on the disease state of the foot not the animal.

Alteration in lymphocytes responses, cytokine and chemokine profiles in laying hens infected with Salmonella Typhimurium

Salmonella Typhimurium has been reported to contaminate egg production across the world, but the exact nature of the immune mechanisms protective against Salmonella infection in laying hens has not been characterized at the molecular level. The experiment was conducted to determine Salmonella colonization and lymphocytes subpopulation in the ileum and spleen, and the mRNA expression of pro-inflammatory cytokines [interleukin (IL)-1β and IL-6], chemokine IL-8, and T helper (Th)1/Th2 cytokines [Interferon (IFN)-γ, IL-12 and IL-18; IL-4 and IL-10 respectively] in the cecal tonsil and spleen of Salmonella challenged hens. Forty Salmonella-free laying hens were challenged orally with Salmonella Typhimurium or phosphate-buffered saline (PBS; control). The Salmonella challenged or non-challenged hens (n=10) were sacrificed at 2 and 7 days post-infection (DPI). The lymphocyte subpopulation was determined via flow cytometric analysis in the ileum and spleen. The cecal tonsil and spleen samples were collected for mRNA expression through quantitative-RT-PCR. The Salmonella counts were higher (P<0.05) in the ileum than that in the spleen at 2 and 7DPI, and were higher (P<0.05) at 7DPI than that at 2DPI in the spleen. Salmonella challenge increased (P<0.05) ileal CD4+ and CD8α+ cells ratios at 2 and 7DPI, whereas it increased (P<0.05) splenic CD8α+ cells ratio only at 7DPI. The magnitude of increase in ileal CD8α+ cells ratio was higher (P<0.05) than that in CD4+ cells ratio. The mRNA expression of IL-1β, IL-6, IL-8, IFN-γ, IL-12 and IL-18 were significantly up-regulated in the cecal tonsil of Salmonella challenged hens, and the magnitude of increases in IL-6, IL-8 and IL-12 were significantly higher at 7DPI than that at 2DPI. However, Salmonella challenge increased (P<0.05) the mRNA expression of IL-1β, IL-10 and IL-18 at 2 and 7DPI, and IL-8 and IFN-γ mRNA only at 7DPI in the spleen. These findings demonstrated that there appeared the induction of cellular immune responses, and a Th1-cytokines reaction in the intestine and spleen of laying hens infected with Salmonella Typhimurium.

Class B CpG ODN stimulation upregulates expression of TLR21 and IFN-γ in chicken Harderian gland cells

This study aimed to evaluate the response of Harderian gland (HG) cells after in vitro stimulation with class B synthetic oligodeoxyribonucleotides (ODN) containing CpG motifs. This knowledge is of importance for the development of mucosal vaccines for poultry, such as eye-drop or spray vaccines, to determine if class B CpG ODN can act as an vaccine adjuvant or as a prophylactic treatment mainly against respiratory disease viruses. The relative expression of Toll-like receptor 21 (TLR21), interferon (IFN)-γ, interleukin (IL)-1β and IL-10 genes were quantified at 1, 3, 6 and 18 h post-stimulation of HG cells from 5-week-old birds. In addition, it was also investigated if expression of these genes was affected by the age of the birds (differences between 5- and 12-week-old birds), concentrations of ODN or cell preparation method used. Class B CpG ODN induced upregulation of TLR21 and IFN-γ mRNA expression levels at 1h post-stimulation depending on concentration of ODN used but only in HG cells isolated from young birds.

Characterization of cytokine expression induced by avian influenza virus infection with real-time RT-PCR

Knowledge of how birds react to infection from avian influenza virus is critical to understanding disease pathogenesis and host response. The use of real-time (R) RT-PCR to measure innate immunity, including cytokine and interferon gene expression, has become a standard technique employed by avian immunologists interested in examining these responses. This technique utilizes nucleotide primers and fluorescent reporter molecules to measure amplification of the gene of interest. The use of RRT-PCR negates the need for northern blot analysis or DNA sequencing. It is simple, specific and sensitive for the gene of interest. However, it is dependent on knowing the target sequence prior to testing so that the optimal primers can be designed. The recent publication of genomic sequences of Gallus gallus, Meleagris gallopavo, and Anas platyrhynchos species makes it possible to measure cytokine expression in chicken, turkey, and duck species, respectively. Although these tests do not measure functionally expressed protein, the lack of antibodies to identify and quantify avian cytokines from different avian species makes this technique critical to any characterization of innate immune responses through cytokine and interferon activation or repression.

Defense genes missing from the flight division

Birds have a smaller repertoire of immune genes than mammals. In our efforts to study antiviral responses to influenza in avian hosts, we have noted key genes that appear to be missing. As a result, we speculate that birds have impaired detection of viruses and intracellular pathogens. Birds are missing TLR8, a detector for single-stranded RNA. Chickens also lack RIG-I, the intracellular detector for single-stranded viral RNA. Riplet, an activator for RIG-I, is also missing in chickens. IRF3, the nuclear activator of interferon-beta in the RIG-I pathway is missing in birds. Downstream of interferon (IFN) signaling, some of the antiviral effectors are missing, including ISG15, and ISG54 and ISG56 (IFITs). Birds have only three antibody isotypes and IgD is missing. Ducks, but not chickens, make an unusual truncated IgY antibody that is missing the Fc fragment. Chickens have an expanded family of LILR leukocyte receptor genes, called CHIR genes, with hundreds of members, including several that encode IgY Fc receptors. Intriguingly, LILR homologues appear to be missing in ducks, including these IgY Fc receptors. The truncated IgY in ducks, and the duplicated IgY receptor genes in chickens may both have resulted from selective pressure by a pathogen on IgY FcR interactions. Birds have a minimal MHC, and the TAP transport and presentation of peptides on MHC class I is constrained, limiting function. Perhaps removing some constraint, ducks appear to lack tapasin, a chaperone involved in loading peptides on MHC class I. Finally, the absence of lymphotoxin-alpha and beta may account for the observed lack of lymph nodes in birds. As illustrated by these examples, the picture that emerges is some impairment of immune response to viruses in birds, either a cause or consequence of the host-pathogen arms race and long evolutionary relationship of birds and RNA viruses.

Twist1 induces CCL2 and recruits macrophages to promote angiogenesis

The transcription factor Twist1 induces epithelial-mesenchymal transition and extracellular matrix degradation to promote tumor metastasis. Although Twist1 also plays a role in embryonic vascular development and tumor angiogenesis, the molecular mechanisms that underlie these processes are not as well understood. Here, we report a novel function for Twist1 in modifying the tumor microenvironment to promote progression. We found that expression of Twist1 in human mammary epithelial cells potently promoted angiogenesis. Surprisingly, Twist1 expression did not increase the secretion of the common proangiogenic factors VEGF and basic fibroblast growth factor but rather induced expression of the macrophage chemoattractant CCL2. Attenuation of endogenous Twist1 in vivo blocked macrophage recruitment and angiogenesis, whereas exogenous CCL2 rescued the ability of tumor cells lacking Twist1 to attract macrophages and promote angiogenesis. Macrophage recruitment also was essential for the ability of Twist1-expressing cells to elicit a strong angiogenic response. Together, our findings show that how Twist1 recruits stromal macrophages through CCL2 induction to promote angiogenesis and tumor progression. As Twist1 expression has been associated with poor survival in many human cancers, this finding suggests that anti-CCL2 therapy may offer a rational strategy to treat Twist1-positive metastatic cancers.

Antigen presenting cells in a non-mammalian model system, the chicken

The chicken has a different repertoire of tissues, cells and genes of the immune response compared to mammals, yet generally survives infection with viral, bacterial, protozoal and fungal pathogens, and also worms and ectoparasites, just like mammals. Poultry are also probably the most heavily vaccinated group of farmed animals. Antigen presentation to the adaptive immune response therefore obviously normally occurs efficiently in birds. Although comparatively much is known about macrophages and B cells in the chicken, there is as yet little work on the other, professional, antigen-presenting cells, the dendritic cells (DC). Birds also have at least two other sets of phagocytic cells, heterophils and thrombocytes, which may also have the ability to present antigen. Here we review the current state of knowledge about antigen presenting cells in the chicken, concentrating mainly on recent advances in our knowledge of DC.

Chicken CCR6 and CCR7 are markers for immature and mature dendritic cells respectively

In mammals, the CC chemokine receptors 6 and 7 (CCR6 and CCR7) play important roles in controlling the trafficking of dendritic cells (DC). CCR6 is expressed primarily on immature DC in the periphery and plays a role in the recruitment of immature DC to sites of potential antigen entry. On encountering pathogens, DC mature and migrate to secondary lymphoid organs where they present pathogen antigen to T cells to initiate specific adaptive immune responses. Maturation involves down-regulation of CCR6 but up-regulation of CCR7. To investigate the role of these two chemokine receptors in the function of DC in the chicken, a full-length chicken CCR7 (chCCR7) cDNA was cloned. Chicken CCR6 (chCCR6) was already available (Munoz et al., 2009). ChCCR7 shows the typical secondary structure of a seven-transmembrane G protein-coupled receptor and has 66% and 64% amino acid identity with human and mouse CCR7, respectively. Like its mammalian orthologues, chCCR7 mRNA was highly expressed in most lymphoid tissues (with the exception of the Harderian gland) and also in some non-lymphoid tissues (especially the heart, lung, skin and small intestine). Both chCCR6 and chCCR7 were expressed at the mRNA level in immature chicken bone marrow-derived dendritic cells (chBM-DC), as measured by real-time quantitative RT-PCR. After DC maturation following stimulation with LPS or CD40L, expression levels of chCCR6 mRNA were down-regulated, whereas those of chCCR7 were up-regulated, suggesting that these two chemokine receptors play a similar role in the trafficking of chicken DC as they do in mammals and that they act as markers of immature (chCCR6) and mature (chCCR7) DC.

Advances in avian immunology--prospects for disease control: a review

In order to develop novel solutions to avian disease problems, including novel vaccines and/or vaccine adjuvants, and the identification of disease resistance genes which can feed into conventional breeding programmes, it is necessary to gain a more thorough understanding of the avian immune response and how pathogens can subvert that response. Birds occupy the same habitats as mammals, have similar ranges of longevity and body mass, and face similar pathogen challenges, yet birds have a different repertoire of organs, cells, molecules and genes of the immune system compared to mammals. This review summarises the current state of knowledge of the chicken's immune response, highlighting differences in the bird compared to mammals, and discusses how the availability of the chicken genome sequence and the associated postgenomics technologies are contributing to theses studies and also to the development of novel intervention strategies againts avian and zoonotic disease.

Genomic identification of chemokines and cytokines in opossum

The cytokine repertoire of marsupials is largely unknown. The sequencing of the opossum genome has expedited the identification of many immune genes. However, many genes have not been identified using automated annotation pipelines because of high levels of sequence divergence. To fill gaps in our knowledge of the cytokine gene complement in marsupials, we searched the genome assembly of the gray short-tailed opossum for chemokine, interleukin, colony-stimulating factor, tumor necrosis factor, and transforming growth factor genes. In particular, we focused on genes that were not previously identified through Ensembl's automatic annotations. We report that the vast majority of cytokines are conserved, with direct orthologs between therian species. The major exceptions are chemokine genes, which show lineage-specific duplication/loss. Thirty-six chemokines were identified in opossum, including a lineage-specific expansion of macrophage inflammatory protein family genes. Divergent cytokines IL7, IL9, IL31, IL33, and CSF2 were identified. This is the first time IL31 and IL33 have been described outside of eutherian species. The high levels of similarities between the cytokine gene repertoires of therians suggest that the marsupial immune response is highly similar to eutherians.

Functional characterization of the CC chemokine RANTES from Pekin duck (Anas platyrhynchos)

RANTES (Regulated upon Activation, Normal T-cell Expressed and Secreted) is a key pro-inflammatory cytokine that belongs to the CC-group of chemokines. The present study was carried out to functionally characterize the previously identified RANTES homologue in domestic duck (GenBank Accession No. AY641435). Recombinant duck RANTES was expressed in Escherichia coli-based and HEK293T cell-based systems. A tRNA supplementation strategy was required to express the protein in E. coli due to the presence of rare codons. In biological assays using HEK293T cell-expressed protein, RANTES was found to mediate chemotaxis of DT-40 chicken B cells and primary duck splenocytes at a concentration of 0.505μg/ml (0.6μM). Immunostaining of the migrated splenocytes using anti-duck CD4 and CD8 monoclonal antibodies and subsequent flow cytometric analysis showed enhanced chemotaxis of CD8+ cells. The recombinant RANTES exhibited in vitro antiviral activity by inhibiting infection of chicken embryo fibroblast cells with duck enteritis virus (DEV) at the same concentration. The effect could be neutralized by rabbit anti-duck RANTES polyclonal serum. The mechanism seems to be direct on viral particles as evidenced by the need for co-incubation of RANTES with DEV prior to the infection for antiviral activity, and also by the enhanced binding of DEV to E. coli expressed purified RANTES on ELISA-based assays. Our results show that the duck RANTES has overlapping biological properties with its mammalian orthologue, and also has possible functional cross-reactivity with chicken immune cells indicated by the chemotaxis of DT-40 cells.

Cloning and characterisation of the chicken orthologue of dendritic cell-lysosomal associated membrane protein (DC-LAMP)

A cDNA encoding the chicken orthologue of dendritic cell-lysosomal associated membrane protein (DC-LAMP)/CD208 was cloned by RT-PCR from RNA isolated from mature chicken bone marrow-derived dendritic cells (chBM-DCs). The cloned chicken DC-LAMP (chDC-LAMP) cDNA consists of 1281 nucleotides encoding an open reading frame of 426 amino acids (aa). Comparison of the deduced aa sequence of DC-LAMP with orthologous proteins from human and mouse revealed 27 and 24% identity, respectively. The predicted chDC-LAMP protein shares the characteristic features of LAMP family members. ChDC-LAMP mRNA, unlike its mammalian orthologues, was expressed in a wide range of tissues, at highest levels in the lung. Lymphoid tissues including thymus, spleen, bursa, ceacal tonsil and Meckel's diverticulum had high chDC-LAMP mRNA expression levels. ChDC-LAMP mRNA was expressed in all splenocyte subsets with the highest expression in Bu-1(+) B cells and KUL01(+) cells, which would include macrophages and DC. ChDC-LAMP mRNA was highly expressed in chBM-DC, whereas expression levels in chicken monocyte-derived macrophages (chMo-Mac) and the HD11 macrophage cell line were significantly lower. Following CD40L stimulation, chDC-LAMP mRNA expression levels were up-regulated in mature chBM-DC, chMo-Mac and HD11 cells whereas lipopolysaccharide (LPS) only up-regulated chDC-LAMP mRNA expression levels in chBM-DC. ChDC-LAMP is not solely expressed on chicken DC but can be used as a marker to differentiate between immature and mature DC.

Selection of broilers with improved innate immune responsiveness to reduce on-farm infection by foodborne pathogens

Economic pressure on the modern poultry industry has directed the selection process towards fast-growing broilers that have a reduced feed conversion ratio. Selection based heavily on growth characteristics could adversely affect immune competence leaving chickens more susceptible to disease. Since the innate immune response directs the acquired immune response, efforts to select poultry with an efficient innate immune response would be beneficial. Our laboratories have been evaluating the innate immune system of two parental broiler lines to assess their capacity to protect against multiple infections. We have shown increased in vitro heterophil function corresponds with increased in vivo resistance to Gram-positive and Gram-negative bacterial infections. Additionally, there are increased mRNA expression levels of pro-inflammatory cytokines/chemokines in heterophils isolated from resistant lines compared to susceptible lines. Collectively, all data indicate there are measurable differences in innate responsiveness under genetic control. Recently, a small-scale selection trial was begun. We identified sires within a broiler population with higher and/or lower-than-average pro-inflammatory cytokine/chemokine mRNA expression levels and subsequently utilized small numbers of high-expressing and low-expressing sires to produce progeny with increased or decreased, respectively, pro-inflammatory cytokine/chemokine profiles. This novel approach should allow us to improve breeding stock by improving the overall immunological responsiveness. This will produce a line of chickens with an effective pro-inflammatory innate immune response that should improve resistance against diverse pathogens, improve responses to vaccines, and increase livability. Ongoing work from this project is providing fundamental information for the development of poultry lines that will be inherently resistant to colonization by pathogenic and food-poisoning microorganisms. Utilization of pathogen-resistant birds by the poultry production industry would significantly enhance the microbiological safety of poultry products reaching the consumer.

Effects of stress, mimicked by administration of corticosterone in drinking water, on the expression of chicken cytokine and chemokine genes in lymphocytes

In this study, we identify molecular mediators that participate in the regulation of the immune response during corticosterone-induced stress in chickens. At 7 weeks of age, 120 chickens were exposed for 1 week to corticosterone treatment. Cytokine and chemokine mRNA expression levels were evaluated in peripheral blood and splenic lymphocytes. Expression levels of interleukin (IL)-1beta, IL-6, IL-18 and transforming growth factor (TGF)-beta4 mRNA were significantly up-regulated in lymphocytes 3 h after first treatment with corticosterone. TGF-beta4 and IL-18 remained elevated 1 week post-initial treatment. Compared with controls, corticosterone-treated birds showed greater expression levels of chemokine (CC) mRNA, particularly for CCLi2, CCL5 (RANTES), CCL16 and CXCLi1, in peripheral and splenic lymphocytes 3 h post-initial exposure. CCLi2 mRNA was highly expressed in splenocytes at all time-points. Administration of corticosterone significantly increased circulating corticosterone concentrations and decreased total lymphocyte counts at 3, 24 h and 1 week post-initiation of corticosterone treatment. There was a positive correlation between plasma corticosterone concentrations and CCL5 and CCL16 mRNA at 3 h post-initial administration. At 1 week post-initial treatment, corticosterone concentrations correlated positively with CCL5 and negatively with IL-18 mRNA level. Conditions associated with significant changes in corticosterone levels might therefore affect the immune response by increasing pro-inflammatory responses, leading to potential modulation of the Th1/Th2 balance.

Prospects for understanding immune-endocrine interactions in the chicken

Despite occupying the same habitats as mammals, having similar ranges of body mass and longevity, and facing similar pathogen challenges, birds have a different repertoire of organs, cells, molecules and genes of the immune system when compared to mammals. In other words, birds are not "mice with feathers", at least not in terms of their immune systems. Here we discuss differences between immune gene repertoires of birds and mammals, particularly those known to play a role in immune-endocrine interactions in mammals. If we are to begin to understand immune-endocrine interactions in the chicken, we need to understand these repertoires and also the biological function of the proteins encoded by these genes. We also discuss developments in our ability to understand the function of dendritic cells in the chicken; the function of these professional antigen-presenting cells is affected by stress in mammals. With regard to the endocrine system, we describe relevant chicken pituitary-adrenal hormones, and review recent findings on the expression of their receptors, as these receptors play a crucial role in modulating immune-endocrine interactions. Finally, we review the (albeit limited) work that has been carried out to understand immune-endocrine interactions in the chicken in the post-genome era.

Generation and characterization of chicken bone marrow-derived dendritic cells

Dendritic cells (DCs) are bone marrow-derived professional antigen-presenting cells. The in vitro generation of DCs from either bone marrow or blood is routine in mammals. Their distinct morphology and phenotype and their unique ability to stimulate naïve T cells are used to define DCs. In this study, chicken bone marrow cells were cultured in the presence of recombinant chicken granulocyte-macrophage colony-stimulating factor (GM-CSF) and recombinant chicken interleukin-4 (IL-4) for 7 days. The cultured population showed the typical morphology of DCs, with the surface phenotype of major histocompatibility complex (MHC) class II(+) (high), CD11c(+) (high), CD40(+) (moderate), CD1.1(+) (moderate), CD86(+) (low), CD83(-) and DEC-205(-). Upon maturation with lipopolysaccharide (LPS) or CD40L, surface expression of CD40, CD1.1, CD86, CD83 and DEC-205 was greatly increased. Endocytosis and phagocytosis were assessed by fluorescein isothiocyanate (FITC)-dextran uptake and fluorescent bead uptake, respectively, and both decreased after stimulation. Non-stimulated chicken bone marrow-derived DCs (chBM-DCs) stimulated both allogeneic and syngeneic peripheral blood lymphocytes (PBLs) to proliferate in a mixed lymphocyte reaction (MLR). LPS- or CD40L-stimulated chBM-DCs were more effective T-cell stimulators in MLR than non-stimulated chBM-DCs. Cultured chBM-DCs could be matured to a T helper type 1 (Th1)-promoting phenotype by LPS or CD40L stimulation, as determined by mRNA expression levels of Th1 and Th2 cytokines. We have therefore cultured functional chBM-DCs in a non-mammalian species for the first time.

Chicken CD14, unlike mammalian CD14, is trans-membrane rather than GPI-anchored

A cDNA encoding the chicken homologue of the human myelomonocytic differentiation antigen, CD14, was cloned by RT-PCR from chicken bone marrow cell RNA, using oligonucleotide primers based on the predicted cDNA sequence. The cloned chicken CD14 (chCD14) cDNA encodes an open reading frame of 465 amino acids (aa), with 31-34% aa identity to mouse, bovine and human (hu) CD14. As in mouse and man, chCD14 is a leucine-rich protein. In mammals, CD14 is a GPI-anchored protein. Protein structure analysis suggested that chCD14, by contrast, was potentially a trans-membrane protein. The predicted aa sequence comprises an extracellular domain of 417 aa, followed by a 23-aa trans-membrane segment, and a 25-aa intracytoplasmic region, the latter containing no obvious signalling motifs. COS-7 cells were transfected with p3XFLAG-CMV-8::chCD14 or pCDM8::huCD14, incubated with or without PI-PLC and stained with anti-FLAG or anti-huCD14 antibody respectively. PI-PLC cleaved huCD14 but not chCD14, suggesting that chCD14 is not GPI-anchored. Real-time quantitative RT-PCR analysis revealed that chCD14 mRNA was expressed in most lymphoid and non-lymphoid tissues, except muscle. ChCD14 mRNA was also expressed in most cells examined but strongly expressed in chicken peripheral blood monocyte/macrophages and KUL01+ splenocytes.

The immunobiology of avian systemic salmonellosis

Avian systemic salmonellosis is primarily caused by Salmonella enterica serovar Gallinarum and serovar Pullorum causing the diseases Fowl Typhoid and Pullorum Disease respectively. During infection interaction with the immune system occurs in three main phases. First is invasion via the gastrointestinal tract. Infection with S. Pullorum or S. Gallinarum does not cause substantial inflammation, unlike S. Typhimurium or S. Enteritidis. Through in vitro models it was found that S. Gallinarum does not induce expression of CXC chemokines or pro-inflammatory cytokines such as IL-1beta or IL-6, whilst in an in vivo model S. Pullorum infection leads to down-regulation of CXCLi1 and CXCLi2 in the ileum. The absence of flagella in S. Gallinarum and S. Pullorum means they are not recognised by TLR5, which is believed to play a key role in the initiation of inflammatory responses, though other pathogen-factors are likely to be involved. The second phase is establishing systemic infection. Salmonella invade macrophages and probably dendritic cells and are translocated to the spleen and liver, where replication occurs. Salmonella survival is dependent on the Salmonella pathogenicity island 2 type III secretion system, which inhibits antimicrobial activity by preventing fusion of lysosymes with the phagocytic vacuole and by modulation of MHC and cytokine expression. Studies in resistant and susceptible chicken lines have shown that the interaction with macrophages is central to the progression of infection or immunological clearance. Primary macrophages from resistant animals are more efficient in killing Salmonella through respiratory burst and by induction of cytokine expression including the initiation of protective Th1 responses that leads to the third phase. Where replication of Salmonella is not controlled the death of the animal usually results. If the innate immune system is not able to control replication then cellular and humoral responses, primarily mediated through Th1-associated cytokines, are able to clear infection. In S. Pullorum a significant number of animals develop persistent infection of splenic macrophages. Here we show preliminary evidence of modulation of adaptive immunity away from a Th1 response to facilitate the development of the carrier state. In carrier animals persistence may lead to reproductive tract and egg infection associated with a decline in CD4+ T cell numbers and function associated with the onset of sexual maturity in hens.

Cytokines and chemokines in postovulatory follicle regression of domestic chicken (Gallus gallus domesticus)

The mechanism of postovulatory follicle (POF) regression in birds is still poorly understood. In the current study, expression of IL-1beta, IL-6, GM-CSF, IFN-gamma, IL-2, IL-4, IL-13, chCXCLi2, chCCLi2, chCCLi4, chCCLi7, IL-10 and TGF-beta2 mRNAs was estimated in regressing POF by semi-quantitative RT-PCR. In addition, the changes in immune cell population, histological and apoptotic changes were also studied in regressing POF. The expression of cytokines (IL-1beta, IL-6, IL-10 and TGF-beta2) and chemokines (chCXCLi2, chCCLi2, chCCLi4 and chCCLi7) was upregulated in POFs, suggesting a role for these molecules in tissue regression. The histological findings suggested a significant infiltration of immune cells, especially heterophils, lymphocytes and macrophages, into the regressing POF. The flow cytometry analysis of lymphocyte subpopulations revealed that CD3(+), CD4(+), CD8(+) and Bu-1(+) lymphocytes were significantly increased during this regression. The significant up-regulation of chemokines might have attracted the immune cells during POF regression. The percentage of apoptotic cells was significantly increased during the regression of POF. The up-regulation of IL-1beta, IL-6, IL-10 and TGF-beta2 and down-regulation of GM-CSF might have induced apoptosis during the POF regression. However, expression of IFN-gamma, IL-2, IL-4 and IL-13 was not significantly altered during POF regression. In conclusion, cytokines appear to play an important role in the regression of POF in chicken. Furthermore, the regression of chicken POF seems to be an inflammatory event similar to luteolysis of the mammalian corpus luteum.

Molecular mechanisms of primary and secondary mucosal immunity using avian infectious bronchitis virus as a model system

Although mucosal immune responses are critical for protection of hosts from clinical illness and even mortality caused by mucosal pathogens, the molecular mechanism of mucosal immunity, which is independent of systemic immunity, remains elusive. To explore the mechanistic basis of mucosal protective immunity, gene transcriptional profiling in mucosal tissues was evaluated after the primary and secondary immunization of animals with an attenuated avian infectious bronchitis virus (IBV), a prototype of Coronavirus and a well-characterized mucosal pathogen. Results showed that a number of innate immune factors including toll-like receptors (TLRs), retinoic-acid-inducible gene-1 (RIG-1), type I interferons (IFNs), complements, and interleukin-1 beta (IL-1β) were activated locally after the primary immunization. This was accompanied or immediately followed by a potent Th1 adaptive immunity as evidenced by the activation of T-cell signaling molecules, surface markers, and effector molecules. A strong humoral immune response as supported by the significantly up-regulated immunoglobulin (Ig) gamma chain was observed in the absence of innate, Th1 adaptive immunity, or IgA up-regulation after the secondary immunization, indicating that the local memory response is dominated by IgG. Overall, the results provided the first detailed kinetics on the molecular basis underlying the development of primary and secondary mucosal immunity. The key molecular signatures identified may provide new opportunities for improved prophylactic and therapeutic strategies to combat mucosal infections.

Net replication of Salmonella enterica serovars Typhimurium and Choleraesuis in porcine intestinal mucosa and nodes is associated with their differential virulence

Salmonella enterica is a facultative intracellular pathogen of worldwide importance and causes a spectrum of diseases depending on serovar- and host-specific factors. Oral infection of pigs with S. enterica serovar Typhimurium strain 4/74 produces acute enteritis but is rarely fatal, whereas serovar Choleraesuis strain A50 causes systemic disease with a high mortality rate. With a porcine ligated ileal loop model, we observed that systemic virulence of serovar Choleraesuis A50 is not associated with enhanced intestinal invasion, secretory responses, or neutrophil recruitment compared to serovar Typhimurium 4/74. The net growth in vivo of serovar Choleraesuis A50 and serovar Typhimurium 4/74 was monitored following oral inoculation of pigs with strains harboring pHSG422, which exhibits temperature-sensitive replication. Analysis of plasmid partitioning revealed that the enteric virulence of serovar Typhimurium 4/74 relative to that of serovar Choleraesuis A50 is associated with rapid replication in the intestinal wall, whereas systemic virulence of serovar Choleraesuis A50 is associated with enhanced persistence in intestinal mesenteric lymph nodes. Faster replication of serovar Typhimurium, compared to that of serovar Choleraesuis, in the intestinal mucosa was associated with greater induction of the proinflammatory cytokines tumor necrosis factor alpha, interleukin-8 (IL-8), and IL-18 as detected by reverse transcriptase PCR analysis of transcripts from infected mucosa. During replication in batch culture and porcine alveolar macrophages, transcription of genes encoding components of type III secretion systems 1 (sipC) and 2 (sseC) was observed to be significantly higher in serovar Typhimurium 4/74 than in serovar Choleraesuis A50, and this may contribute to the differences in epithelial invasion and intracellular proliferation. The rapid induction of proinflammatory responses by strain 4/74 may explain why pigs confine serovar Typhimurium infection to the intestines, whereas slow replication of serovar Choleraesuis may enable it to evade host innate immunity and thus disseminate by stealth.

Evolution of CC chemokines in teleost fish: a case study in gene duplication and implications for immune diversity

Chemokines are a superfamily of cytokines responsible for regulating cell migration under both inflammatory and physiological conditions. CC chemokines are the largest subfamily of chemokines, with 28 members in humans. A subject of intense study in mammalian species, the known functional roles of CC chemokines ligands in both developmental and disease conditions continue to expand. They are also an important family for the study of gene copy number variation and tandem duplication in mammalian species. However, little is known regarding the evolutionary origin and status of these ligands in primitive vertebrates such as teleost fish. In this paper, we review the evolution of the teleost fish CC chemokine gene family, noting evidence of widespread tandem gene duplications and examining the implications of this phenomenon on immune diversity. Through extensive phylogenetic analysis of the CC chemokine sets of four teleost species, zebrafish, catfish, rainbow trout, and Atlantic salmon, we identified seven large groups of CC chemokines. It appeared that several major groups of CC chemokines are highly related including the CCL19/21/25 group, the CCL20 group, CCL27/28 group, and the fish-specific group. In the three remaining groups that contained the largest number of members, the CCL17/22 group, the MIP group, and the MCP group, similarities among species members were obscured by rapid, tandem duplications that may contribute to immune diversity.