Efficacy of Fowlpox Virus Vector Vaccine Expressing VP2 and Chicken Interleukin-18 in the Protection against Infectious Bursal Disease Virus

In mammals, the role of interleukin-18 (IL-18) in the immune response is to drive inflammatory and, normally therefore, anti-viral responses. IL-18 also shows promise as a vaccine adjuvant in mammals. Chicken IL-18 (chIL-18) has been cloned. The aim of this study was to investigate the potential of chIL-18 to act as a vaccine adjuvant in the context of a live recombinant Fowlpox virus vaccine (fpIBD1) against Infectious bursal disease virus (IBDV). fpIBD1 protects against mortality, but not against damage to the bursa of Fabricius caused by IBDV infection. The Fowlpox virus genome itself contains several candidate immunomodulatory genes, including potential IL-18 binding proteins (IL-18bp). We knocked out (Δ) the potential IL-18bp genes in fpIBD1 and inserted (::) the cDNA encoding chIL-18 into fpIBD1 in the non-essential ORF030, generating five new viral constructs -fpIBD1::chIL-18, fpIBD1ΔORF073, fpIBD1ΔORF073::chIL-18, fpIBD1ΔORF214, and fpIBD1ΔORF214::chIL-18. The subsequent protection from challenge with virulent IBDV, as measured by viral load and bursal damage, given by these altered fpIBD1 strains, was compared to that given by the original fpIBD1. Complete protection was provided following challenge with IBDV in chicken groups vaccinated with either fpIBDIΔ073::IL-18 or fpIBD1Δ214::IL-18, as no bursal damage nor IBDV was detected in the bursae of the birds. The results show that chIL-18 can act as an effective vaccine adjuvant by improving the fpIBD1 vaccine and providing complete protection against IBDV challenge.

Differential immunological response detected in mRNA expression profiles among diverse chicken lines in response to Salmonella challenge

Salmonella enterica serovar Enteritidis is a bacterial pathogen that contributes to poultry production losses and human foodborne illness. The bacterium elicits a broad immune response involving both the innate and adaptive components of the immune system. Coordination of the immune response is largely directed by cytokines. The objective of the current study was to characterize the expression of a select set of cytokines and regulatory immune genes in three genetically diverse chicken lines after infection with S. Enteritidis. Leghorn, Fayoumi and broiler day-old chicks were orally infected with pathogenic S. Enteritidis or culture medium. At 2 and 18 h postinfection, spleens and ceca were collected and mRNA expression levels for 7 genes (GM-CSF, IL2, IL15, TGF-β1, SOCS3, P20K, and MHC class IIβ) were evaluated by real-time quantitative PCR. Genetic line had a significant effect on mRNA expression levels of IL15, TGF-β1, SOCS3 and P20K in the spleen and on P20K and MHC class IIβ in the cecum. Comparing challenged vs. unchallenged birds, the expression of SOCS3 and P20K mRNA were significantly higher in the spleen and cecum, while MHC class IIβ mRNA was significantly lower in spleen. Combining the current RNA expression results with those of previously reported studies on the same samples reveals distinct RNA expression profiles among the three genetic chicken lines and the 2 tissues. This study illustrates that these diverse genetic lines have distinctively different immune response to S. Enteritidis challenge within the spleen and the cecum.

Development of novel reagents to chicken FLT3, XCR1 and CSF2R for the identification and characterization of avian conventional dendritic cells

Conventional dendritic cells (cDC) are bone marrow-derived immune cells that play a central role in linking innate and adaptive immunity. cDCs efficiently uptake, process and present antigen to naïve T cells, driving clonal expansion of antigen-specific T-cell responses. In chicken, vital reagents are lacking for the efficient and precise identification of cDCs. In this study, we have developed several novel reagents for the identification and characterization of chicken cDCs. Chicken FLT3 cDNA was cloned and a monoclonal antibody to cell surface FLT3 was generated. This antibody identified a distinct FLT3^HI splenic subset which lack expression of signature markers for B cells, T cells or monocyte/macrophages. By combining anti-FLT3 and CSF1R-eGFP transgenic expression, three major populations within the mononuclear phagocyte system were identified in the spleen. The cDC1 subset of mammalian cDCs express the chemokine receptor XCR1. To characterize chicken cDCs, a synthetic chicken chemokine (C motif) ligand (XCL1) peptide conjugated to Alexa Fluor 647 was developed (XCL1^AF647 ). Flow cytometry staining of XCL1^AF647 on splenocytes showed that all chicken FLT3^HI cells exclusively express XCR1, supporting the hypothesis that this population comprises bona fide chicken cDCs. Further analysis revealed that chicken cDCs expressed CSF1R but lacked the expression of CSF2R. Collectively, the cell surface phenotypes of chicken cDCs were partially conserved with mammalian XCR1⁺ cDC1, with distinct differences in CSF1R and CSF2R expression compared with mammalian orthologues. These original reagents allow the efficient identification of chicken cDCs to investigate their important roles in the chicken immunity and diseases.

Kinetics of the Cellular and Transcriptomic Response to Eimeria maxima in Relatively Resistant and Susceptible Chicken Lines

Eimeria maxima is a common cause of coccidiosis in chickens, a disease that has a huge economic impact on poultry production. Knowledge of immunity to E. maxima and 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 by E. maxima. Line C.B12 and 15I chickens were infected with E. maxima and transcriptome analysis of jejunal tissue was performed 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 transcript expression increased in the jejunum earlier in line C.B12 (at 4 dpi) compared to line 15I (at 6 dpi). Line C.B12 chickens exhibited increases of IFNG and IL10 mRNA 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 higher E. maxima replication 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 including IL21 at 4 dpi identified by RNA-Seq, may be key to resistance to E. maxima.

Characterization of Conventional Dendritic Cells and Macrophages in the Spleen Using the CSF1R-Reporter Transgenic Chickens

The spleen is a major site for the immunological responses to blood-borne antigens that is coordinated by cells of the mononuclear phagocyte system (MPS). The chicken spleen is populated with a number of different macrophages while the presence of conventional dendritic cells (cDC) has been described. However, a detailed characterization of the phenotype and function of different macrophage subsets and cDC in the chicken spleen is limited. Using the CSF1R-reporter transgenic chickens (CSF1R-tg), in which cells of the MPS express a transgene under the control elements of the chicken CSF1R, we carried out an in-depth characterization of these cells in the spleen. Immunohistological analysis demonstrated differential expression of MRC1L-B by periarteriolar lymphoid sheaths (PALS)-associated CSF1R-tg+ cells. In the chicken's equivalent of the mammalian marginal zone, the peri-ellipsoid white-pulp (PWP), we identified high expression of putative CD11c by ellipsoid-associated cells compared to ellipsoid-associated macrophages. In addition, we identified a novel ellipsoid macrophage subset that expressed MHCII, CD11c, MRC1L-B, and CSF1R but not the CSF1R-tg. In flow cytometric analysis, diverse expression of the CSF1R-tg and MHCII was observed leading to the categorization of CSF1R-tg cells into CSF1R-tgdim MHCIIinter−hi, CSF1R-tghi MHCIIhi, and CSF1R-tghi MHCIIinter subpopulations. Low levels of CD80, CD40, MHCI, CD44, and Ch74.2 were expressed by the CSF1R-tghi MHCIIinter cells. Functionally, in vivo fluorescent bead uptake was significantly higher in the CSF1R-tghi MHCIIhi MRC1L-B+ cells compared to the CSF1R-tgdim and CSF1R-tghi MHCIIinter MRC1L-B+ subpopulations while LPS enhanced phagocytosis by the CSF1R-tghi MHCIIinter subpopulation. The analysis of bead localization in the spleen suggests the presence of ellipsoid-associated macrophage subsets. In addition, we demonstrated the functionality of ex vivo derived CSF1R-tg+ MRC1L-Bneg cDC. Finally, RNA-seq analysis of the CSF1R-tg subpopulations demonstrated that separating the CSF1R-tghi subpopulation into CD11chi and CD11cdim cells enriched for cDC and macrophage lineages, respectively, while the CSF1R-tghi MHCIIinter subpopulation was enriched for red pulp macrophages. However, our analysis could not define the cell lineage of the heterogeneous CSF1R-tgdim subpopulation. This detailed overview of the MPS in the chicken spleen will contribute to future research on their role in antigen uptake and presentation.

Mid-term follow-up of surgically treated and healed scaphoid fractures

The aim of this study was to evaluate the mid-term results of surgically treated scaphoid fractures since we were concerned that good results might deteriorate over time due to osteoarthritis or functional impairment. Thirty-three out of 121 surgically treated patients (isolated scaphoid fractures n = 23; scaphoid fractures with concomitant injuries n = 10) were evaluated retrospectively (47-138 months). Five patients (4%) had a non-union after internal fixation and were excluded because of additional treatment. The remaining 83 patients were not available for a follow-up examination. Patients with an isolated scaphoid fracture had a mean extension-flexion of 68°-0°-64°, a radial-ulnar deviation of 27°-0°-41° and a grip strength of 39 kg (corresponding to 87-98% of the uninjured contralateral wrist), while patients with concomitant injuries had a mean extension-flexion of 60°-0°-44°, radial-ulnar deviation of 22°-0°-38° and a grip strength of 42 kg (corresponding to 73-98% of the uninjured contralateral wrist). The Michigan Hand Questionnaire score was 85 and 75 and the Patient-Rated Wrist Evaluation score was 8 and 21, respectively. Fifteen patients had radiological signs of radiocarpal osteoarthritis with a significantly higher occurrence in those who had concomitant injuries compared to those with isolated scaphoid fractures (p < 0.01). There was no significant group difference in scaphotrapeziotrapezoid (STT) osteoarthritis (p = 0.968). One STT osteoarthritis case occurred after plate fixation, one after antegrade screw fixation and 10 after retrograde screw fixation. Surgical treatment of an acute isolated scaphoid fracture has excellent clinical, functional, and radiologic mid-term results, while scaphoid fractures with concomitant wrist injuries have slightly inferior results.

Erratum: Chakraborty, P. et al. Macrophages from Susceptible and Resistant Chicken Lines have Different Transcriptomes following Marek’s Disease Virus Infection. Genes 2019, 10, 74

The authors wish to make the following correction to their paper published in Genes [...]

Recent advances in the surgical treatment of malunions in hand and forearm using three-dimensional planning and patient-specific instruments

Malunions of the forearm and hand cause significant disability. Moreover, intraarticular deformities may contribute to early onset osteoarthritis. Such conditions require precise surgical correction in order to improve functional outcomes and prevent early or late complications. The purpose of this study was to describe the technical advantages of accurate anatomical reconstruction using 3D guided osteotomies and patient specific instruments (PSI) in multiple joints of the hand and forearm. Acquisition of three-dimensional (3D) datasets and surgical implementation of PSI was performed in a series of patients between December 2014 and July 2017. Patients had intra- or extra-articular malunions of the forearm, radiocarpal joint, trapeziometacarpal joint, or proximal interphalangeal joint. A previously described 3D surface model that incorporates CT data was used for segmentation (Mimics®, Materialise™, Belgium). For all the cases, CT scans of both forearms were acquired to use the contralateral uninjured side as the anatomic reconstruction template. Computer-assisted assessment of the deformity, the preoperative plan, and the design of PSI are described. Outcomes were determined by evaluating step-off correction, fusion, changes in range of motion (ROM) and grip strength. Six patients were included in the study; all achieved fusion. Improved clinical outcomes including pain reduction, better ROM and grip strength were obtained. Complete correction of intraarticular step-off was achieved in all cases with intraarticular malunions. 3D guided osteotomies are an established surgical treatment option for malunions of the hand and forearm. 3D analysis is a helpful diagnostic tool that provides detailed information about the underlying deformity. PSI can be developed and used for surgical correction with maximal accuracy for both intraarticular step-off and angular deformity.

Regulation and function of macrophage colony-stimulating factor (CSF1) in the chicken immune system

Macrophage colony-stimulating factor (CSF1) is an essential growth factor to control the proliferation, differentiation and survival of cells of the macrophage lineage in vertebrates. We have previously produced a recombinant chicken CSF1-Fc fusion protein and administrated it to birds which produced a substantial expansion of tissue macrophage populations. To further study the biology of CSF1 in the chicken, here we generated anti-chicken CSF1 antibodies (ROS-AV181 and 183) using CSF1-Fc as an immunogen. The specific binding of each monoclonal antibody was confirmed by ELISA, Western blotting and immunohistochemistry on tissue sections. Using the anti-CSF1 antibodies, we show that chicken bone marrow derived macrophages (BMDM) express CSF1 on their surface, and that the level appears to be regulated further by exogenous CSF1. By capture ELISA circulating CSF1 levels increased transiently in both layer and broiler embryos around the day of hatch. The levels of CSF1 in broilers was higher than in layers during the first week after hatch. Antibody ROS-AV183 was able to block CSF1 biological activity in vitro and treatment of hatchlings using this neutralising antibody in vivo impacted on some tissue macrophage populations, but not blood monocytes. After anti-CSF1 treatment, CSF1R-transgene reporter expressing cells were reduced in the bursa of Fabricius and cecal tonsil and TIM4⁺ Kupffer cells in the liver were almost completely ablated. Anti-CSF1 treatment also produced a reduction in overall bone density, trabecular volume and TRAP⁺ osteoclasts. Our novel neutralising antibody provides a new tool to study the roles of CSF1 in birds.

Static patella tilt and axial engagement in knee extension are mainly influenced by knee torsion, the tibial tubercle-trochlear groove distance (TTTG), and trochlear dysplasia but not by femoral or tibial torsion

PURPOSE

The aim of this study was to investigate the association of femoral (FT), tibial (TT), and knee torsion (KT) on the patella tilt (PT), the axial engagement index (AEI), and the tibial tuberosity-trochlear groove distance (TTTG).

METHODS

Femoral torsion, tibial torsion, knee torsion, patella tilt, the axial engagement index, the TTTG, and trochlear dysplasia were retrospectively evaluated on 59 patients suffering from recurrent patella instability or anterior knee pain with 118 torsional lower limb magnetic resonance imaging studies.

RESULTS

FT and TT did not show any significant associations with TTTG, PT, and AEI (n.s.). KT was significantly associated with a higher TTTG, higher PT, and lower AEI (all, p < 0.001). Higher grade trochlear dysplasia was associated with a higher PT and lower AEI (both, p < 0.001). The Dejour classification showed no significant association with FT, TT, KT, and TTTG (n.s.). All measurement parameters showed an excellent interrater agreement (ICC 0.89-0.97).

CONCLUSIONS

Static patella tilt and patellofemoral axial engagement in knee extension are mainly influenced by knee torsion, TTTG, and trochlear dysplasia but not by femoral or tibial torsion. These findings help to understand the underlying reasons for the patella position in knee extensions in CT and MRI investigations in patients suffering from patella instability and patellofemoral pain syndrome.

LEVEL OF EVIDENCE

III.

Avian Pathogenic Escherichia coli (APEC) Strain-Dependent Immunomodulation of Respiratory Granulocytes and Mononuclear Phagocytes in CSF1R-Reporter Transgenic Chickens

Avian pathogenic Escherichia coli (APEC) cause severe respiratory and systemic disease in chickens, commonly termed colibacillosis. Early immune responses after initial infection are highly important for the outcome of the infection. In this study, the early interactions between GFP-expressing APEC strains of serotypes O1:K1:H7 and O2:K1:H5 and phagocytic cells in the lung of CSF1R-reporter transgenic chickens were investigated. CSF1R-reporter transgenic chickens express fluorescent protein under the control of elements of the CSF1R promoter and enhancer, such that cells of the myeloid lineage can be visualized in situ and sorted. Chickens were separately inoculated with APEC strains expressing GFP and culled 6 h post-infection. Flow cytometric analysis was performed to phenotype and sort the cells that harbored bacteria in the lung, and the response of the sorted cells was defined by transcriptomic analysis. Both APEC strains were mainly detected in CSF1R-transgene^neg (CSF1R-tg^neg) and CSF1R-tg^low MHC II^neg MRC1L-B^neg cells and low numbers of APEC were detected in CSF1R-tg^high MHC II^pos MRC1L-B^pos cells. Transcriptomic and flow cytometric analysis identified the APEC^pos CSF1R-tg^neg and CSF1R-tg^low cells as heterophils and the APEC^pos CSF1R-tg^high cells as macrophages and dendritic cells. Both APEC strains induced strong inflammatory responses, however in both CSF1R-tg^neg/low and CSF1R-tg^high cells, many immune related pathways were repressed to a greater extent or less activated in birds inoculated with APEC O2-GFP compared to APEC O1-GFP inoculated birds. Comparison of the immune pathways revealed the aryl hydrocarbon receptor (AhR) pathway, IL17 and STAT3 signaling, heterophil recruitment pathways and the acute phase response, are modulated particularly post-APEC O2-GFP inoculation. In contrast to in vivo data, APEC O2-GFP was more invasive in CSF1R-tg^high cells in vitro than APEC O1-GFP and had higher survival rates for up to 6 h post-infection. Our data indicate significant differences in the responses induced by APEC strains of prevalent serotypes, with important implications for the design and interpretation of future studies. Moreover, we show that bacterial invasion and survival in phagocyte populations in vitro is not predictive of events in the chicken lung.

Highly multiplexed quantitative PCR-based platform for evaluation of chicken immune responses

To address the need for sensitive high-throughput assays to analyse avian innate and adaptive immune responses, we developed and validated a highly multiplexed qPCR 96.96 Fluidigm Dynamic Array to analyse the transcription of chicken immune-related genes. This microfluidic system permits the simultaneous analysis of expression of 96 transcripts in 96 samples in 6 nanolitre reactions and the 9,216 reactions are ready for interpretation immediately. A panel of 89 genes was selected from an RNA-seq analysis of the transcriptional response of chicken macrophages, dendritic cells and heterophils to agonists of innate immunity and from published transcriptome data. Assays were confirmed to be highly specific by amplicon sequencing and melting curve analysis and the reverse transcription and preamplification steps were optimised. The array was applied to RNA of various tissues from a commercial line of broiler chickens housed at two different levels of biosecurity. Gut-associated lymphoid tissues, bursa, spleen and peripheral blood leukocytes were isolated and transcript levels for immune-related genes were defined. The results identified blood cells as a potentially reliable indicator of immune responses among all the tissues tested with the highest number of genes significantly differentially transcribed between birds housed under varying biosecurity levels. Conventional qPCR analysis of three differentially transcribed genes confirmed the results from the multiplex qPCR array. A highly multiplexed qPCR-based platform for evaluation of chicken immune responses has been optimised and validated using samples from commercial chickens. Apart from applications in selective breeding programmes, the array could be used to analyse the complex interplay between the avian immune system and pathogens by including pathogen-specific probes, to screen vaccine responses, and as a predictive tool for immune robustness.

Macrophages from Susceptible and Resistant Chicken Lines have Different Transcriptomes following Marek's Disease Virus Infection

Despite successful control by vaccination, Marek’s disease (MD) has continued evolving to greater virulence over recent years. To control MD, selection and breeding of MD-resistant chickens might be a suitable option. MHC-congenic inbred chicken lines, 6₁ and 7₂, are highly resistant and susceptible to MD, respectively, but the cellular and genetic basis for these phenotypes is unknown. Marek’s disease virus (MDV) infects macrophages, B-cells, and activated T-cells in vivo. This study investigates the cellular basis of resistance to MD in vitro with the hypothesis that resistance is determined by cells active during the innate immune response. Chicken bone marrow-derived macrophages from lines 6₁ and 7₂ were infected with MDV in vitro. Flow cytometry showed that a higher percentage of macrophages were infected in line 7₂ than in line 6₁. A transcriptomic study followed by in silico functional analysis of differentially expressed genes was then carried out between the two lines pre- and post-infection. Analysis supports the hypothesis that macrophages from susceptible and resistant chicken lines display a marked difference in their transcriptome following MDV infection. Resistance to infection, differential activation of biological pathways, and suppression of oncogenic potential are among host defense strategies identified in macrophages from resistant chickens.

Dose-dependent differential resistance of inbred chicken lines to avian pathogenic Escherichia coli challenge

Avian pathogenic E. coli (APEC) cause severe respiratory and systemic disease. To address the genetic and immunological basis of resistance, inbred chicken lines were used to establish a model of differential resistance to APEC, using strain O1 of serotype O1:K1:H7. Inbred lines 7₂, 15I and C.B12 and the outbred line Novogen Brown were inoculated via the airsac with a high dose (10⁷ colony-forming units, CFU) or low dose (10⁵ CFU) of APEC O1. Clinical signs, colibacillosis lesion score and bacterial colonization of tissues after high dose challenge were significantly higher in line 15I and C.B12 birds. The majority of the 15I and C.B12 birds succumbed to the infection by 14 h post-infection, whilst none of the line 7₂ and the Novogen Brown birds developed clinical signs. No difference was observed after low dose challenge. In a repeat study, inbred lines 7₂ and 15I were inoculated with low, intermediate or high doses of APEC O1 ranging from 10⁵ to 10⁷ CFU. The colonization of lung was highest in line 15I after high dose challenge and birds developed clinical signs; however, colonization of blood and spleen, clinical signs and lesion score were not different between lines. No difference was observed after intermediate or low dose challenge. Ex vivo, the phagocytic and bactericidal activity of lung leukocytes from line 7₂ and 15I birds did not differ. Our data suggest that although differential resistance of inbred lines 7₂, 15I and C.B12 to APEC O1 challenge is apparent, it is dependent on the infectious dose. Research Highlights Lines 15I and C.B12 are more susceptible than line 7₂ to a high dose of APEC O1. Differential resistance is dose-dependent in lines 15I and 7₂. Phagocytic and bactericidal activity is similar and dose independent.

Characterization of Subpopulations of Chicken Mononuclear Phagocytes That Express TIM4 and CSF1R

The phosphatidylserine receptor TIM4, encoded by TIMD4, mediates the phagocytic uptake of apoptotic cells. We applied anti-chicken TIM4 mAbs in combination with CSF1R reporter transgenes to dissect the function of TIM4 in the chick (Gallus gallus). During development in ovo, TIM4 was present on the large majority of macrophages, but expression became more heterogeneous posthatch. Blood monocytes expressed KUL01, class II MHC, and CSF1R-mApple uniformly. Around 50% of monocytes were positive for surface TIM4. They also expressed many other monocyte-specific transcripts at a higher level than TIM4^- monocytes. In liver, highly phagocytic TIM4^hi cells shared many transcripts with mammalian Kupffer cells and were associated with uptake of apoptotic cells. Although they expressed CSF1R mRNA, Kupffer cells did not express the CSF1R-mApple transgene, suggesting that additional CSF1R transcriptional regulatory elements are required by these cells. By contrast, CSF1R-mApple was detected in liver TIM4^lo and TIM4^- cells, which were not phagocytic and were more abundant than Kupffer cells. These cells expressed CSF1R alongside high levels of FLT3, MHCII, XCR1, and other markers associated with conventional dendritic cells in mice. In bursa, TIM4 was present on the cell surface of two populations. Like Kupffer cells, bursal TIM4^hi phagocytes coexpressed many receptors involved in apoptotic cell recognition. TIM4^lo cells appear to be a subpopulation of bursal B cells. In overview, TIM4 is associated with phagocytes that eliminate apoptotic cells in the chick. In the liver, TIM4 and CSF1R reporters distinguished Kupffer cells from an abundant population of dendritic cell-like cells.

Colonization of a commercial broiler line by Campylobacter is under limited genetic control and does not significantly impair performance or intestinal health

Campylobacter is the leading bacterial cause of foodborne diarrheal illness in humans and source attribution studies unequivocally identify handling or consumption of poultry meat as a key risk factor. Campylobacter colonizes the avian intestines in high numbers and rapidly spreads within flocks. A need therefore exists to devise strategies to reduce Campylobacter populations in poultry flocks. There has been a great deal of research aiming to understand the epidemiology and transmission characteristics of Campylobacter in poultry as a means to reduce carriage rates in poultry and reduce infection in humans. One potential strategy for control is the genetic selection of poultry for increased resistance to colonization by Campylobacter. The potential for genetic control of colonization has been demonstrated in inbred populations following experimental challenge with Campylobacter where quantitative trait loci associated with resistance have been identified. Currently in the literature there is no information of the genetic basis of Campylobacter colonization in commercial broiler lines and it is unknown whether these QTL are found in commercial broiler lines. The aim of this study was to estimate genetic parameters associated with Campylobacter load and genetic correlations with gut health and production traits following natural exposure of broiler chickens to Campylobacter.The results from the analysis show a low but significant heritability estimate (0.095 ± 0.037) for Campylobacter load which indicates a limited genetic basis and that non-genetic factors have a greater influence on the level of Campylobacter found in the broiler chicken.Furthermore, through examination of macroscopic intestinal health and absorptive capacity, our study indicated that Campylobacter has no detrimental effects on intestinal health and bird growth following natural exposure in the broiler line under study. These data indicate that whilst there is a genetic component to Campylobacter colonization worthy of further investigation, there is a large proportion of phenotypic variance under the influence of non-genetic effects. As such the control of Campylobacter will require understanding and manipulation of non-genetic host and environmental factors.

Dissecting the Genomic Architecture of Resistance to Eimeria maxima Parasitism in the Chicken

Coccidiosis in poultry, caused by protozoan parasites of the genus Eimeria, is an intestinal disease with substantial economic impact. With the use of anticoccidial drugs under public and political pressure, and the comparatively higher cost of live-attenuated vaccines, an attractive complementary strategy for control is to breed chickens with increased resistance to Eimeria parasitism. Prior infection with Eimeria maxima leads to complete immunity against challenge with homologous strains, but only partial resistance to challenge with antigenically diverse heterologous strains. We investigate the genetic architecture of avian resistance to E. maxima primary infection and heterologous strain secondary challenge using White Leghorn populations of derived inbred lines, C.B12 and 15I, known to differ in susceptibility to the parasite. An intercross population was infected with E. maxima Houghton (H) strain, followed 3 weeks later by E. maxima Weybridge (W) strain challenge, while a backcross population received a single E. maxima W infection. The phenotypes measured were parasite replication (counting fecal oocyst output or qPCR for parasite numbers in intestinal tissue), intestinal lesion score (gross pathology, scale 0-4), and for the backcross only, serum interleukin-10 (IL-10) levels. Birds were genotyped using a high density genome-wide DNA array (600K, Affymetrix). Genome-wide association study located associations on chromosomes 1, 2, 3, and 5 following primary infection in the backcross population, and a suggestive association on chromosome 1 following heterologous E. maxima W challenge in the intercross population. This mapped several megabases away from the quantitative trait locus (QTL) linked to the backcross primary W strain infection, suggesting different underlying mechanisms for the primary- and heterologous secondary- responses. Underlying pathways for those genes located in the respective QTL for resistance to primary infection and protection against heterologous challenge were related mainly to immune response, with IL-10 signaling in the backcross primary infection being the most significant. Additionally, the identified markers associated with IL-10 levels exhibited significant additive genetic variance. We suggest this is a phenotype of interest to the outcome of challenge, being scalable in live birds and negating the requirement for single-bird cages, fecal oocyst counts, or slaughter for sampling (qPCR).

Phenotypic and genetic variation in the response of chickens to Eimeria tenella induced coccidiosis

BACKGROUND

Coccidiosis is a major contributor to losses in poultry production. With emerging constraints on the use of in-feed prophylactic anticoccidial drugs and the relatively high costs of effective vaccines, there are commercial incentives to breed chickens with greater resistance to this important production disease. To identify phenotypic biomarkers that are associated with the production impacts of coccidiosis, and to assess their covariance and heritability, 942 Cobb500 commercial broilers were subjected to a defined challenge with Eimeria tenella (Houghton). Three traits were measured: weight gain (WG) during the period of infection, caecal lesion score (CLS) post mortem, and the level of a serum biomarker of intestinal inflammation, i.e. circulating interleukin 10 (IL-10), measured at the height of the infection.

RESULTS

Phenotypic analysis of the challenged chicken cohort revealed a significant positive correlation between CLS and IL-10, with significant negative correlations of both these traits with WG. Eigenanalysis of phenotypic covariances between measured traits revealed three distinct eigenvectors. Trait weightings of the first eigenvector, (EV1, eigenvalue = 59%), were biologically interpreted as representing a response of birds that were susceptible to infection, with low WG, high CLS and high IL-10. Similarly, the second eigenvector represented infection resilience/resistance (EV2, 22%; high WG, low CLS and high IL-10), and the third eigenvector tolerance (EV3, 19%; high WG, high CLS and low IL-10), respectively. Genome-wide association studies (GWAS) identified two SNPs that were associated with WG at the suggestive level.

CONCLUSIONS

Eigenanalysis separated the phenotypic impact of a defined challenge with E. tenella on WG, caecal inflammation/pathology, and production of IL-10 into three major eigenvectors, indicating that the susceptibility-resistance axis is not a single continuous quantitative trait. The SNPs identified by the GWAS for body weight were located in close proximity to two genes that are involved in innate immunity (FAM96B and RRAD).

Visualisation and characterisation of mononuclear phagocytes in the chicken respiratory tract using CSF1R-transgenic chickens

The respiratory tract is a key organ for many avian pathogens as well as a major route for vaccination in the poultry industry. To improve immune responses after vaccination of chickens through increased uptake of vaccines and targeting to antigen presenting cells, a better understanding of the avian respiratory immune system is required. Transgenic MacReporter birds were used expressing a reporter gene (eGFP or mApple) under the control of the CSF1R promoter and enhancer in cells of the mononuclear phagocyte (MNP) lineage to visualize the ontogeny of the lymphoid tissue, macrophages and dendritic cells, in the trachea, lung and air sac of birds from embryonic day 18–63 weeks of age. Small aggregates of CSF1R-transgene⁺ cells start to form at the openings of the secondary bronchi at 1 week of age, indicative of the early development of the organised bronchus-associated lymphoid tissue. Immunohistochemical staining revealed subpopulations of MNPs in the lung, based on expression of CSF1R-transgene, CD11, TIM4, LAMP1, and MHC II. Specialised epithelial cells or M cells covering the bronchus-associated lymphoid tissue expressed CSF1R-transgene and type II pneumocytes expressed LAMP1 suggesting that these epithelial cells are phagocytic and transcytose antigen. Highly organised lymphoid tissue was seen in trachea from 4 weeks onwards. Throughout the air sacs at all ages, CSF1R-transgene⁺ cells were scattered and at later stages, CSF1R-transgene⁺ cells lined capillaries. These results will serve as a base for further functional characterization of macrophages and dendritic cells and their role in respiratory diseases and vaccine responses.

The role of local adaptation in sustainable village chicken production

Village chickens are ubiquitous in smallholder farming systems, contributing to household, local and national economies under diverse environmental, economic and cultural settings. However, they are raised in challenging environments where productivity is low while mortality is high. There is much interest in utilizing indigenous genetic resources to produce a chicken resilient to its environment, whilst providing the basis of an economically sustainable enterprise. Globally, however, a wide variety of interventions have so far proved unable to deliver sustainable improvements. Here, we show that regional differences in trait preferences and parasite burden are associated with distinct chicken genepools, likely in response to interacting natural and human-driven (economic and social) selection pressures. Drivers of regional differences include marketing opportunities, cultural preferences, agro-ecologies and parasite populations, and are evident in system adaptations, such as management practices, population dynamics and bird genotypes. Our results provide sound multidisciplinary evidence to support previous observations that sustainable poultry development interventions for smallholder farmers, including breeding programs, should be locally tailored and designed for flexible implementation.

Comparison of volarly and dorsally displaced distal radius fracture treated by volar locking plate fixation

INTRODUCTION

In case of distal radius fractures (DRF) the distal fragment generally displaces either dorsally or volarly. Scientific literature however, seldom differentiates between volarly and dorsally displaced DRFs when reporting results. It is no clear, if the direction of displacement has an influence on the clinical and radiological outcome. This study was intended to evaluate the influence of displacement direction in adult patients with surgically treated Colles or Smith type fractures.

PATIENTS AND METHODS

After a mean follow up (FU) time of above 5 years, 50 patients who underwent open reduction and internal fixation for DRFs (25 Smith type fractures, 25 Colles type fractures) were included. Upon FU, standard X-rays and a clinical evaluation as well as evaluation scores were raised and analysed.

RESULTS

Clinical evaluation showed no difference between the Colles and the Smith group. Radiologic and clinical results for the Colles group showed diminished flexion compared to the healthy wrist, decreased radial inclination and dorsal tilt during FU and progression of osteoarthritis. For the Smith group decreased grip strength compared to the healthy wrist and osteoarthritis-progression was found. For both groups there was no correlation between radiologic values, grip strength, arthrosis grading, disability of arm, shoulder and hand score and patient rated wrist evaluation score.

DISCUSSION

Decreased flexion in combination with a decreased dorsopalmar tilt might hint towards a mechanical inhibition in the Colles group. Altogether, the study showed good clinical outcome with satisfactory radiological result. As all patients showed arthrosis progression, the fracture per se is to be seen as a prearthrotic factor. It still remains unclear which measures could be taken to prevent this.

[Wide awake hand surgery based on application examples]

OBJECTIVE

Anesthesiologic method with low bleeding level, risk level, and complication rate for surgical procedures on the hand without a tourniquet on an unsedated patient with the possibility for functional testing during surgery.

INDICATIONS

Surgical procedures of the hand can be carried out using the wide awake technique depending on the patient's suitability and preference considering individual risk factors.

CONTRAINDICATIONS

Absolute contraindications are allergies to the local anesthetic or its components. Relative contraindications are severe hepatic or renal insufficiency, infections in the injection area, acute circulatory disorders, or higher cardiac function impairment.

INJECTION TECHNIQUE

Infiltration of a lidocaine/epinephrine mixture with 8.4% sodium bicarbonate in a ratio of 10:1.5 at least 30 min prior to surgery. Perpendicular puncture of the skin and slow injection. Continue injection until reaching a pale skin area of at least 1 cm around the entire operating area. If the needle tip always remains in a cushion of local anesthetic, a "hole-in-one" anesthesia can be achieved (only the first needle puncture is felt).

POSTOPERATIVE MANAGEMENT

Elevated care and awareness for numb body parts by the patient because of impaired sensation. Follow-up treatment according to the surgeon's specifications. Postoperative use of painkillers.

RESULTS

Of 38 patients, 32 felt that the procedure was not stressful, 6 rated it as a bit stressful. Pain perception on a visual analog scale (0 = no pain, 10 = severe pain) scored an average of 1.6 during infiltration, 0.5 during the operation, 3.5 during the reduction of the anesthesia, and 2.9 on the following day. All patients would undergo surgery again using the wide awake technique.

Synergistic effect of co-stimulation of membrane and endosomal TLRs on chicken innate immune responses

Toll-like receptor (TLR) ligands (TLR-Ls) are critical activators of immunity and are successfully being developed as vaccine adjuvants in both mammals and birds. In this study, we investigated the synergistic effect of co-stimulation of membrane and endosomal TLRs on the innate immune responses using chicken bone marrow-derived macrophages (BMMs), and studied the effect of age on the induction of innate responses. BMMs from 1 and 4-week-old birds were stimulated with Pam3Cys-SK4 (PCSK; TLR2), synthetic monophosphoryl lipid A (MPLA), Di[3-deoxy-d-manno-octulosonyl]-lipid A ammonium salt (KLA; TLR4), Gardiquimod, Resiquimod (R848; TLR7), CpG class B and C (TLR21). Nitric oxide (NO) production and mRNA levels of IL-1β, IL-10 and IL-12p40 showed macrophages from 4-week-old birds showed more sensitive responses compared to 1-week-old birds. The most potent TLR-Ls, PCSK, MPLA and CpG B were used to study the effect of co-stimulation on macrophages. Co-stimulation with TLR21 and TLR4 synergistically up-regulated inflammatory-related genes, as well as NO production. However, incubation of splenocytes with PCSK, MPLA and CpG B did not induce cell proliferation. Moreover, treatment with CpG B led to significant cell death.

Chicken anaemia virus evades host immune responses in transformed lymphocytes

Chicken anaemia virus (CAV) is a lymphotropic virus that causes anaemia and immunosuppression in chickens. Previously, we proposed that CAV evades host antiviral responses in vivo by disrupting T-cell signalling, but the precise cellular targets and modes of action remain elusive. In this study, we examined gene expression in Marek's disease virus-transformed chicken T-cell line MSB-1 after infection with CAV using both a custom 5K immune-focused microarray and quantitative real-time PCR at 24, 48 and 72 h post-infection. The data demonstrate an intricate equilibrium between CAV and the host gene expression, displaying subtle but significant modulation of transcripts involved in the T-cell, inflammation and NF-κB signalling cascades. CAV efficiently blocked the induction of type-I interferons and interferon-stimulated genes at 72 h. The cell expression pattern implies that CAV subverts host antiviral responses and that the transformed environment of MSB-1 cells offers an opportunistic advantage for virus growth.

Host-specific differences in the response of cultured macrophages to Campylobacter jejuni capsule and O-methyl phosphoramidate mutants

Campylobacter jejuni is the leading cause of bacterial food-borne gastroenteritis worldwide and human infections are frequently associated with handling and consumption of contaminated poultry. The polysaccharide capsule of C. jejuni plays important roles in colonisation of the chicken gut, invasion of epithelial cells and serum resistance and is subject to modification with O-methyl phosphoramidate (MeOPN) in most strains. In this study, the cytokine responses of mouse bone marrow-derived macrophages (mBMMs), chicken bone marrow-derived macrophages (chBMMs) and human monocyte-derived macrophages (hMDMs) were measured following infection with C. jejuni 11168H wild-type (WT) or isogenic mutants lacking either the capsule (Δcj1439) or its MeOPN modification (Δcj1417). Consistent with previous observations using murine bone marrow-derived dendritic cells, mutants lacking the capsule or MeOPN elicited enhanced transcription of IL-6 and IL-10 in mBMMs compared to wild-type C. jejuni. However, the lack of capsule and MeOPN did not alter IL-6 and IL-10 expression in chBMMs and hMDMs compared to C. jejuni WT. Phagocytosis assays showed the acapsular mutant was not impaired in uptake or net intracellular survival after phagocytosis in both chicken and human macrophages; however, the phagocytosis of the MeOPN mutant was significantly decreased in both chicken and human macrophages. In conclusion, differences in the response of macrophages of varying host origin to Campylobacter were detected. The absence of MeOPN modification on the capsule of C. jejuni did not alter the levels of innate cytokine expression in both chicken and human macrophages compared to the 11168H WT, but affected phagocytosis by host macrophages.

Identification of the Receptor and Cellular Ortholog of the Marek's Disease Virus (MDV) CXC Chemokine

Marek's disease virus (MDV) is a cell associated alphaherpesvirus that causes fatal lymphoma in chickens. One factor that plays a crucial role in MDV pathogenesis is the viral CXC chemokine vIL-8 that was originally named after chicken interleukin 8 (cIL-8). However, a recent study demonstrated that vIL-8 recruits B cells and a subset of T cells but not neutrophils, suggesting that vIL-8 is not a cIL-8 orthologue. In this study, we set to identify the cellular orthologues and receptor of vIL-8 using in silico analyses, binding and chemotaxis assays. Sequence and phylogenetic analyses of all chicken CXC chemokines present in the recently published chicken genome revealed that vIL-8 shares the highest amino acid similarity with the CXCL13L1 variant. To evaluate if vIL-8 and CXCL13L1 are also functional orthologues, we assessed their binding properties and chemotaxis activity. We demonstrated that both vIL-8 and CXCL13 variants bind B cells and subsets of T cells, confirming that they target the same cell types. In addition, the chemokines not only bound the target cells but also induced chemotaxis. Finally, we identified CXCR5 as the receptor of vIL-8 and CXCL13 variants and confirmed that the receptor is expressed on MDV target cells. Taken together, our data demonstrate the conservation of the receptor-ligand interaction between CXCR5 and CXCL13 and shed light on the origin and function of the MDV-encoded vIL-8 chemokine, which plays a crucial role in the pathogenesis of this highly oncogenic virus.

Functional annotation of the T-cell immunoglobulin mucin family in birds

T‐cell immunoglobulin and mucin (TIM) family molecules are cell membrane proteins, preferentially expressed on various immune cells and implicated in recognition and clearance of apoptotic cells. Little is known of their function outside human and mouse, and nothing outside mammals. We identified only two TIM genes (chTIM) in the chicken genome, putative orthologues of mammalian TIM1 and TIM4, and cloned the respective cDNAs. Like mammalian TIM1, chTIM1 expression was restricted to lymphoid tissues and immune cells. The gene chTIM4 encodes at least five splice variants with distinct expression profiles that also varied between strains of chicken. Expression of chTIM4 was detected in myeloid antigen‐presenting cells, and in γδ T cells, whereas mammalian TIM4 is not expressed in T cells. Like the mammalian proteins, chTIM1 and chTIM4 fusion proteins bind to phosphatidylserine, and are thereby implicated in recognition of apoptotic cells. The chTIM4–immunoglobulin fusion protein also had co‐stimulatory activity on chicken T cells, suggesting a function in antigen presentation.

Marek's disease virus infection of phagocytes: a de novo in vitro infection model

Marek's disease virus (MDV) is an alphaherpesvirus that induces T-cell lymphomas in chickens. Natural infections in vivo are caused by the inhalation of infected poultry house dust and it is presumed that MDV infection is initiated in the macrophages from where the infection is passed to B cells and activated T cells. Virus can be detected in B and T cells and macrophages in vivo, and both B and T cells can be infected in vitro. However, attempts to infect macrophages in vitro have not been successful. The aim of this study was to develop a model for infecting phagocytes [macrophages and dendritic cells (DCs)] with MDV in vitro and to characterize the infected cells. Chicken bone marrow cells were cultured with chicken CSF-1 or chicken IL-4 and chicken CSF-2 for 4 days to produce macrophages and DCs, respectively, and then co-cultured with FACS-sorted chicken embryo fibroblasts (CEFs) infected with recombinant MDV expressing EGFP. Infected phagocytes were identified and sorted by FACS using EGFP expression and phagocyte-specific mAbs. Detection of MDV-specific transcripts of ICP4 (immediate early), pp38 (early), gB (late) and Meq by RT-PCR provided evidence for MDV replication in the infected phagocytes. Time-lapse confocal microscopy was also used to demonstrate MDV spread in these cells. Subsequent co-culture of infected macrophages with CEFs suggests that productive virus infection may occur in these cell types. This is the first report of in vitro infection of phagocytic cells by MDV.

In vitro characterization of chicken bone marrow-derived dendritic cells following infection with very virulent infectious bursal disease virus

Infectious bursal disease is caused by infectious bursal disease virus (IBDV), an immunosuppressive virus that targets immune cells such as B cells and macrophages. However, the involvement of dendritic cells (DCs) during IBDV infection is not well understood. In this study the in vitro effects of live and inactivated very virulent IBDV (vvIBDV) UPM0081 on bone marrow-derived DCs (BM-DC) were characterized and compared with BM-DC treated with lipopolysaccharide (LPS). Morphologically, BM-DC treated with LPS and vvIBDV showed stellate shape when compared to immature BM-DC. In addition, LPS-treated and both live and inactivated vvIBDV-infected BM-DC expressed high levels of double positive CD86 and major histocompatibility complex class II antigens (>20%). vvIBDV-infected BM-DC showed significantly higher numbers of apoptotic cells compared to LPS. Replication of vvIBDV was detected in the infected BM-DC as evidenced by the increased expression of VP3 and VP4 IBDV antigens based on flow cytometry, real-time polymerase chain reaction and immunofluorescence tests. Levels of different immune-related genes such as interleukin-1β (IL-1β), CXCLi2 (IL-8), IL-18, interferon gamma (IFN-γ, IL-12α, CCR7 and Toll-like receptor-3 (TLR3) were measured after LPS and vvIBDV treatments. However, marked differences were noticed in the onset and intensity of the gene expression between these two treatment groups. LPS was far more potent than live and inactivated vvIBDV in inducing the expression of IL-1β, IL-18 and CCR7 while expression of Th1-like cytokines, IFN-γ and IL-12α were significantly increased in the live vvIBDV treatment group. Meanwhile, the expression of TLR3 was increased in live vvIBDV-infected BM-DC as compared to control. Inactivated vvIBDV-treated BM-DC failed to stimulate IFN-γ, IL-12α and TLR3 expressions. This study suggested that BM-DC may serve as another target cells during IBDV infection which require further confirmation via in vivo studies.

Analysis of the function of IL-10 in chickens using specific neutralising antibodies and a sensitive capture ELISA

In mammals, the inducible cytokine interleukin 10 is a feedback negative regulator of inflammation. To determine the extent to which this function is conserved in birds, recombinant chicken IL-10 was expressed as a secreted human Ig Fc fusion protein (chIL-10-Fc) and used to immunise mice. Five monoclonal antibodies (mAb) which specifically recognise chicken IL-10 were generated and characterised. Two capture ELISA assays were developed which detected native chIL-10 secreted from chicken bone marrow-derived macrophages (chBMMs) stimulated with lipopolysaccharide (LPS). Three of the mAbs detected intracellular IL-10. This was detected in only a subset of the same LPS-stimulated chBMMs. The ELISA assay also detected massive increases in circulating IL-10 in chickens challenged with the coccidial parasite, Eimeria tenella. The same mAbs neutralised the bioactivity of recombinant chIL-10. The role of IL-10 in feedback control was tested in vitro. The neutralising antibodies prevented IL-10-induced inhibition of IFN-γ synthesis by mitogen-activated lymphocytes and increased nitric oxide production in LPS-stimulated chBMMs. The results confirm that IL-10 is an inducible feedback regulator of immune response in chickens, and could be the target for improved vaccine efficacy or breeding strategies.

Genome-wide association studies of immune, disease and production traits in indigenous chicken ecotypes

Background

The majority of chickens in sub-Saharan Africa are indigenous ecotypes, well adapted to the local environment and raised in scavenging production systems. Although they are generally resilient to disease challenge, routine vaccination and biosecurity measures are rarely applied and infectious diseases remain a major cause of mortality and reduced productivity. Management and genetic improvement programmes are hampered by lack of routine data recording. Selective breeding based on genomic technologies may provide the means to enhance sustainability. In this study, we investigated the genetic architecture of antibody response to four major infectious diseases [infectious bursal disease (IBDV), Marek’s disease (MDV), fowl typhoid (SG), fowl cholera (PM)] and resistance to Eimeria and cestode parasitism, along with two production traits [body weight and body condition score (BCS)] in two distinct indigenous Ethiopian chicken ecotypes. We conducted variance component analyses, genome-wide association studies, and pathway and selective sweep analyses.

Results

The large majority of birds was found to have antibody titres for all pathogens and were infected with both parasites, suggesting almost universal exposure. We derived significant moderate to high heritabilities for IBDV, MDV and PM antibody titres, cestodes infestation, body weight and BCS. We identified single nucleotide polymorphisms (SNPs) with genome-wide significance for each trait. Based on these associations, we identified for each trait, pathways, networks and functional gene clusters that include plausible candidate genes. Selective sweep analyses revealed a locus on chromosome 18 associated with viral antibody titres and resistance to Eimeria parasitism that is within a positive selection signal. We found no significant genetic correlations between production, immune and disease traits, implying that selection for altered antibody response and/or disease resistance will not affect production.

Conclusions

We confirmed the presence of genetic variability and identified SNPs significantly associated with immune, disease and production traits in indigenous village chickens. Results underpin the feasibility of concomitant genetic improvement for enhanced antibody response, resistance to parasitism and productivity within and across indigenous chicken ecotypes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12711-016-0252-7) contains supplementary material, which is available to authorized users.

Cryopreservation of specialized chicken lines using cultured primordial germ cells

Biosecurity and sustainability in poultry production requires reliable germplasm conservation. Germplasm conservation in poultry is more challenging in comparison to other livestock species. Embryo cryopreservation is not feasible for egg-laying animals, and chicken semen conservation has variable success for different chicken breeds. A potential solution is the cryopreservation of the committed diploid stem cell precursors to the gametes, the primordial germ cells ( PGCS: ). Primordial germ cells are the lineage-restricted cells found at early embryonic stages in birds and form the sperm and eggs. We demonstrate here, using flocks of partially inbred, lower-fertility, major histocompatibility complex- ( MHC-: ) restricted lines of chicken, that we can easily derive and cryopreserve a sufficient number of independent lines of male and female PGCs that would be sufficient to reconstitute a poultry breed. We demonstrate that germ-line transmission can be attained from these PGCs using a commercial layer line of chickens as a surrogate host. This research is a major step in developing and demonstrating that cryopreserved PGCs could be used for the biobanking of specialized flocks of birds used in research settings. The prospective application of this technology to poultry production will further increase sustainability to meet current and future production needs.

The genomic architecture of resistance to Campylobacter jejuni intestinal colonisation in chickens

BACKGROUND

Campylobacter is the leading cause of foodborne diarrhoeal illness in humans and is mostly acquired from consumption or handling of contaminated poultry meat. In the absence of effective licensed vaccines and inhibitors, selection for chickens with increased resistance to Campylobacter could potentially reduce its subsequent entry into the food chain. Campylobacter intestinal colonisation levels are influenced by the host genetics of the chicken. In the present study, two chicken populations were used to investigate the genetic architecture of avian resistance to colonisation: (i) a back-cross of two White Leghorn derived inbred lines [(61 x N) x N] known to differ in resistance to Campylobacter colonisation and (ii) a 9(th) generation advanced intercross (61 x N) line.

RESULTS

The level of colonisation with Campylobacter jejuni following experimental infection was found to be a quantitative trait. A back-cross experiment using 1,243 fully informative single nucleotide polymorphism (SNP) markers revealed quantitative trait loci (QTL) on chromosomes 7, 11 and 14. In the advanced intercross line study, the location of the QTL on chromosome 14 was confirmed and refined and two new QTLs were identified located on chromosomes 4 and 16. Pathway and re-sequencing data analysis of the genes located in the QTL candidate regions identified potential pathways, networks and candidate resistance genes. Finally, gene expression analyses were performed for some of the candidate resistance genes to support the results.

CONCLUSION

Campylobacter resistance in chickens is a complex trait, possibly involving the Major Histocompatibility Complex, innate and adaptive immune responses, cadherins and other factors. Two of the QTLs for Campylobacter resistance are co-located with Salmonella resistance loci, indicating that it may be possible to breed simultaneously for enhanced resistance to both zoonoses.

Genome wide transcriptomic analysis identifies pathways affected by the infusion of Clostridium perfringens culture supernatant in the duodenum of broilers in situ

Clostridium perfringens type A is the main etiological factor for necrotic enteritis, a multifactorial enteric disease that penalizes performance, health, and welfare of poultry. Lack of knowledge of host responses and disease pathogenesis is slowing down progress on developing therapies for disease control. A combined genomewide and targeted gene approach was used to investigate pathways and biological functions affected by the infusion of C. perfringens culture supernatant in the duodenum of broilers in 2 experiments. An in situ isolated loop of duodenum was prepared in anesthetized broilers of 3 wk of age (Exp. 1) and was infused either with crude C. perfringens culture supernatant (n = 7; treated), positive for necrotic enteritis B-like toxin (NetB) as determined by a cytotoxicity assay, or with a control preparation (n = 6; control). Birds were maintained alive for 1 h and then euthanized for tissue recovery. The use of the Affymetrix chicken genome array on RNA samples from loop tissue showed top biological functions affected by culture supernatant infusion included cell morphology, immune cell trafficking, and cell death; pathways affected included death receptor signaling, inflammatory response, and nuclear factor (NF)-κB signaling. In a second in situ study (Exp. 2), broilers were maintained alive for 4 h to monitor temporal expression patterns of targeted genes. Duodenal tissue was removed at 0.5, 1, 2, and 4 h post-infusion with culture supernatant (n = 9) or a control preparation (n = 5) for histology and gene expression analysis. Genes encoding proinflammatory cytokines, such as interferon γ (IFNγ), cell trafficking, such as neuroblastoma 1 (NBL1) and B cell CLL/Lymphoma 6 (BCL6), and cell death, such as Fas cell surface death receptor (FAS) and GTPase IMAP family member 8 (GIMAP8), were differentially expressed in the duodenum of treated and control broilers (P < 0.05). We have demonstrated that C. perfringens culture supernatant (NetB positive) infusion resulted in histological and gene expression changes consistent with necrotic enteritis in the duodenum of broilers. In the absence of live bacteria, crude culture supernatant resulted in early immunomodulation, inflammation, and cell death in the duodenum. The pathways identified here can be targeted for the development of new drugs, vaccines, and novel therapies for necrotic enteritis in broilers.