Effects of dexamethasone immunosuppression on turkey clostridial dermatitis

Immunization of turkeys with Clostridium septicum alpha toxin-based recombinant subunit proteins can confer protection against experimental Clostridial dermatitis

Clostridial dermatitis (CD), caused by Clostridium septicum, is an emerging disease of increasing economic importance in turkeys. Currently, there are no effective vaccines for CD control. Here, two non-toxic domains of C. septicum alpha toxin, namely ntATX-D1 and ntATX-D2, were identified, cloned, and expressed in Escherichia coli as recombinant subunit proteins to investigate their use as potential vaccine candidates. Experimental groups consisted of a Negative control (NCx) that did not receive C. septicum challenge, while the adjuvant-only Positive control (PCx), ntATX-D1 immunization (D1) and ntATX-D2 immunization (D2) groups received C. septicum challenge. Turkeys were immunized subcutaneously with 100 μg of protein at 7, 8 and 9 weeks of age along with an oil-in-water nano-emulsion adjuvant, followed by C. septicum challenge at 11 weeks of age. Results showed that while 46.2% of birds in the PCx group died post-challenge, the rate of mortality in D1- or D2-immunization groups was 13.3%. The gross and histopathological lesions in the skin, muscle and spleen showed that the disease severity was highest in PCx group, while the D2-immunized birds had significantly lower lesion scores when compared to PCx. Gene expression analysis revealed that PCx birds had significantly higher expression of pro-inflammatory cytokine genes in the skin, muscle and spleen than the NCx group, while the D2 group had significantly lower expression of these genes compared to PCx. Peripheral blood cellular analysis showed increased frequencies of activated CD4+ and/or CD8+ cells in the D1 and D2-immunized groups. Additionally, the immunized turkeys developed antigen-specific serum IgY antibodies. Collectively, these findings indicate that ntATX proteins, specifically the ntATX-D2 can be a promising vaccine candidate for protecting turkeys against CD and that the protection mechanisms may include downregulation of C. septicum-induced inflammation and increased CD4+ and CD8+ cellular activation.

Characterization of immune responses and immunopathology in turkeys experimentally infected with clostridial dermatitis-producing strains of Clostridium septicum

Clostridium septicum is one of the major causative agents of clostridial dermatitis (CD), an emerging disease of turkeys, characterized by sudden deaths and necrotic dermatitis. Despite its economic burden on the poultry industry, the immunopathological changes and pathogen-specific immune responses are poorly characterized. Here, we used three strains of C. septicum, namely Str. A1, Str. B1 and Str. C1, isolated from CD field outbreaks, to experimentally infect turkeys to evaluate local (skin and muscle) and systemic (spleen) pathological and immunological responses. Results showed that while all three strains produced an acute disease, Str. A1 and B1 caused significantly higher mortality when compared to Str. C1. Gross and histopathology evaluation showed that birds infected with Str. A1 and B1 had severe inflammatory, edematous, granulomatous and necrotic lesions in the skin, muscle and spleen, while these lesions produced by Str. C1 were relatively less severe and mostly confined to skin and/or muscle. Immune gene expression in these tissues showed that Str. B1-infected birds had significantly higher expression of interleukin (IL)-1β, IL-6 and interferon (IFN)γ genes compared to uninfected control, suggesting a robust inflammatory response both locally as well as systemically. The transcription of IL-1β and IFNγ in the muscle or spleen of Str. A1-infected birds and IL-1β in the skin of Str. C1-infected group was also significantly higher than control. Additionally, Str. A1 or B1-infected groups also had significantly higher IL-4 transcription in these tissues, while birds infected with all three strains developed C. septicum-specific serum antibodies. Furthermore, splenic cellular immunophenotyping in the infected turkeys showed a marked reduction in CD4+ cells. Collectively, it can be inferred that host responses against C. septicum involve an acute inflammatory response along with antibody production and that the disease severity seem to depend on the strain of C. septicum involved in CD in turkeys.

Modulation of inflammatory and oxidative stress biomarkers due to dexamethasone exposure in chicken splenocytes

Dexamethasone (DEXA) is a potent corticosteroid, commonly used for treating inflammatory, hypersensitive and allergic conditions. It is administered to birds with tumours. Many studies were conducted on its immunosuppressive effects; however none of the similar study is available employing chicken splenocytes culture system. The present study was conducted to assess DEXA induced alterations in inflammatory and oxidative stress biomarkers in chicken splenocytes due to its in vitro exposure. The maximum non-cytotoxic dose (MNCD) was evaluated and was further used for conducting lymphocytes proliferation assay (LPA), antioxidant assays (lipid peroxidation, GSH, superoxide dismutase and nitric oxide assays) and assessment of mRNA levels of various genes (IL-1β, IL-6, IL-10, LITAF, iNOS, NF-κB1, Nrf-2, Caspase-3 and -9) through qPCR. The MNCD was determined to be 30 ng/ml in chicken splenocytes culture system. DEXA caused reduction in B and T lymphocytes proliferation indicating its immunosuppressive effects, however improved the antioxidant status of the exposed splenocytes. The expression levels of IL-1β, IL-6, iNOS, LITAF and NF-κB1 were significantly reduced while IL-10 was enhanced, which signify potent anti-inflammatory potential of DEXA. NF-κB is a major transcription factor that regulates genes responsible for both, innate and adaptive immune responses and elicits inflammation. The nuclear factor erythroid 2-related factor 2 (Nrf-2) level was found to be up-regulated. Nrf-2 plays important role in combating the oxidant stress and its increased expression could be the reason of improved antioxidant status of DEXA exposed cells. Present findings indicated that DEXA exhibited modulation in anti-inflammatory, immunomodulatory and antioxidant mediators in chicken splenocytes.

Immune Response Evaluation in Commercial Turkeys Affected with Clostridial Dermatitis

Clostridial dermatitis (CD), caused by Clostridium septicum and Clostridium perfringens, is an economically important emerging disease of turkeys characterized by sudden deaths and necrotic dermatitis. Immune responses in CD-affected commercial turkeys are poorly understood. In the present study, C. septicum was isolated from CD-affected commercial turkeys during a recent outbreak, and the tissues (skin, muscle, and spleen) were collected and analyzed for immune gene expression, along with samples from clinically healthy birds. The results showed that CD-affected turkeys had significantly higher levels of IL-1β, IL-6, IFNγ, and iNOS transcripts in the skin, muscle, and spleen tissues compared to healthy birds. Affected turkeys also had a significantly elevated transcription of toll-like receptor (TLR21) gene in the skin and spleen tissues, suggesting a role for this receptor in the immune recognition. The expression of IL-4 and IL-13 genes in the spleen and muscle was also significantly higher in the affected birds. Additional birds from the same affected and healthy farms examined for serology revealed that the CD-affected turkeys had significantly higher levels of serum IgM and IgY antibodies. Furthermore, in vitro stimulation of MQ-NCSU macrophages with C. septicum led to a significant transcriptional upregulation of IL-1β and IFNγ genes, while the IL-10 gene expression was downregulated. The surface expression of MHC-II protein and cellular production of nitric oxide were also significantly increased in the C. septicum-stimulated macrophages, indicating cellular activation. Collectively, our findings suggest that the host responses in CD-affected turkeys involve a robust inflammatory response as well as a response mediated by IL4/IL-13 cytokines that may aid in antibody-mediated immunity.

Proof-of-Concept Preclinical Use of Drosophila melanogaster in the Initial Screening of Immunomodulators

Drug discovery is a complex process, and the use of a comprehensive approach is deemed necessary to discover new chemical entities with novel mechanisms of action. This research was carried out to determine whether Drosophila melanogaster can serve as an appropriate model organism in the initial screening of drug candidates with immunomodulatory activities. To test this, we performed phenotypic assay and molecular analysis to investigate the immunomodulatory activities of aspirin, dexamethasone, curcumin, and epigallocatechin gallate (EGCG), that have been reported to yield such effects in the mammalian model system. In vivo survival analysis demonstrated that all drugs/compounds were relatively safe at the tested concentrations. In the infection assay, curcumin and EGCG showed a protective signature to bacterial infection in flies lacking Toll-mediated immune responses. Furthermore, dexamethasone and aspirin, drugs with immunosuppressive activity, could improve the survival of PGRP-LBΔ mutant flies with hyperactivated immune system. These phenotypes were supported by RT-qPCR-based molecular analysis, revealing that drugs/compounds used in this study could modulate the expression level of genes related to the immune system. In conclusion, while curcumin and EGCG could promote the improvement of fly survival against infection, aspirin and dexamethasone were able to suppress overactivation of immune responses in D. melanogaster. These results are in line with the ones observed in the mammalian model system, further emphasizing the notion that flies would serve as a prospective model organism in the initial screening of drug candidates for their immunomodulatory activities prior to further checking in the mammalian animal models. In the end, this will reduce the use of mammalian animal models for preliminary experiments in an effort to discover/repurpose drugs with immunomodulatory activity.

Occurrence and relevance of Mycoplasma spp. in free-ranging pheasants from northwestern Germany

Since 2008/2009, the population of free-ranging ring-necked pheasants was recorded to decrease all over Germany. Various Mycoplasma (M.) spp. are causing severe respiratory signs in captive game bird species. Furthermore, M. gallisepticum is responsible for massive die-offs in consequence to severe conjunctivitis in house finches in the USA. Therefore, the prevalence of mycoplasmas in free-ranging pheasants was investigated and a potential impact on the population decline of pheasants discussed. Within this study, 150 free-ranging pheasants were sampled via tracheal swabs and tissue samples of the trachea and the periorbital skin, as the latter displayed inflammatory alterations in previous studies. In total, 177 samples were investigated for the presence of mycoplasmas using cultural and molecular biological methods. In 76 birds, necropsy was performed additionally. In total, 73.7% (51/76) of the examined pheasants had periorbital skin alterations. Furthermore, 64.4% (114/177) of the samples tested positive for mycoplasmas via PCR. Overall, 102/177 samples (57.6%, 78/105 tracheal swabs, 19/51 skin tissue, 5/21 trachea tissue) tested positive for mycoplasmas via culture. Mycoplasma gallinaceum (n = 50), M. pullorum (n = 45), M. glycophilum (n = 43), M. iners (n = 11), and M. gallinarum (n = 5) were frequently isolated. In 45 cases (45.9%), multiple Mycoplasma spp. were isolated from one sample. All examined samples tested negative for M. gallisepticum. Of 51 skin samples investigated for mycoplasmas, 24 (47.1%) showed inflammatory skin alterations in histology, and 58.3% (14/24) of these samples tested positive for Mycoplasma spp. additionally. Overall, there was a significant correlation between inflammatory altered skin samples and the detection of mycoplasmas in periorbital skin samples. Based on the present results, the isolated Mycoplasma spp. may play a role as facultative agents for the observed inflammatory skin alterations. However, additional investigation is needed to confirm this presumption.

Analysis of risk factors for dermatitis and cellulitis in turkeys using abattoir post mortem data

1. Cellulitis and dermatitis are often seen in turkeys at slaughter and are, in many cases, reasons for rejection at meat inspection. Using the results of meat inspections and information about the housing conditions of the animals may provide information on causative factors in the development of cellulitis and dermatitis. 2. A census of two years of turkey production in a company including both fattening farms and an abattoir in the north of England was used to study the relationship between the prevalence of cellulitis/dermatitis and mechanical versus natural ventilation in the poultry house, litter type (long straw, short straw and wood shavings) and stocking density. 3. The overall prevalence of cellulitis and dermatitis in this population was 0.12 %, which was extremely low compared to reports in the literature. In mechanically ventilated houses, the odds of developing cellulitis and/or dermatitis was significantly higher than in naturally ventilated houses (Odds Ratio 3.18). Long straw had a protective effect compared to wood shavings (Odds Ratio 0.18). 4. The study showed that using slaughter data can be helpful in studying on-farm risk factors for disease development.

Specific-pathogen-free Turkey model for reoviral arthritis

Turkey arthritis reovirus (TARV) infections have been recognized since 2011 to cause disease and significant economic losses to the U.S. turkey industry. Reoviral arthritis has been reproduced in commercial-origin turkeys. However, determination of pathogenesis or vaccine efficacy in these turkeys can be complicated by enteric reovirus strains and other pathogens that ubiquitously exist at subclinical levels among commercial turkey flocks. In this study, turkeys from a specific-pathogen-free (SPF) flock were evaluated for use as a turkey reoviral arthritis model. One-day-old or 1-week-old poults were orally inoculated with TARV (O'Neil strain) and monitored for disease onset and progression. A gut isolate of turkey reovirus (MN1 strain) was also tested for comparison. Disease was observed only in TARV-infected birds. Features of reoviral arthritis in SPF turkeys included swelling of hock joints, tenosynovitis, distal tibiotarsal cartilage erosion, and gait defects (lameness). Moreover, TARV infection resulted in a significant depression of body weights during the early times post-infection. Age-dependent susceptibility to TARV infection was unclear. TARV was transmitted to all sentinel birds, which manifested high levels of tenosynovitis and tibiotarsal cartilage erosion. Simulation of stressful conditions by dexamethasone treatment did not affect the viral load or exacerbate the disease. Collectively, the clinical and pathological features of reoviral arthritis in the SPF turkey model generally resembled those induced in commercial turkeys under field and/or experimental conditions. The SPF turkey reoviral arthritis model will be instrumental in evaluation of TARV pathogenesis and reoviral vaccine efficacy.

Effect of sulfated yeast beta-glucan on cyclophosphamide-induced immunosuppression in chickens

Immunosuppression is a condition that causes large economic losses in the poultry industry. To investigate the effect of sulfated yeast beta-glucan on immunosuppression, two hundred and fifty 11-day-old chickens were randomly assigned to five groups, and except for the normal control group, injected with cyclophosphamide once a day for 3 successive days. At 14 days of age, sulfated yeast beta-glucan from Saccharomyces cerevisiae(sGSC) was orally administered at three doses to the chickens in three experimental groups for 14 days. On days 7 and 14 after the first sGSC dose, serum cytokine concentrations and peripheral lymphocyte proliferation were measured. Gut microbiota, organ index, and histopathological changes in the bursa were investigated on day 14. The results demonstrated that at 4 mg/kg, sGSC could significantly enhance the bursa index and IFN-γ and IL-6 concentrations, decrease TGF-β1 concentration, and promote lymphocyte proliferation; it could effectively decrease histopathological changes in the bursa and improve gut Bifidobacterium and Lactobacillus populations in cecal digesta of chickens compared with the model control group. This indicated that sGSC could effectively alleviate immunosuppression and regulate the beneficial microbiota in the gut.

Investigation into diseases in free-ranging ring-necked pheasants (Phasianus colchicus) in northwestern Germany during population decline with special reference to infectious pathogens

The population of ring-necked pheasants (Phasianus colchicus) is decreasing all over Germany since the years 2008/2009. Besides impacts of habitat changes caused by current rates of land conversion, climatic influences or predators, a contribution of infectious pathogens needs also to be considered. Infectious and non-infectious diseases in free-living populations of ring-necked pheasants have been scarcely investigated so far. In the present study, carcasses of 258 deceased free-ranging pheasants of different age groups, predominantly adult pheasants, collected over a period of 4 years in the states of Lower Saxony, North Rhine–Westphalia and Schleswig-Holstein, were examined pathomorphologically, parasitologically, virologically and bacteriologically, with a focus set on infectious pathogens. A periocular and perinasal dermatitis of unknown origin was present in 62.3% of the pheasants. Additional alterations included protozoal cysts in the skeletal musculature (19.0%), hepatitis (21.7%), enteritis (18.7%), gastritis (12.6%), and pneumonia (11.7%). In single cases, neoplasms (2.6%) and mycobacteriosis (1.7%) occurred. Further findings included identification of coronaviral DNA from trachea or caecal tonsils (16.8%), siadenoviral DNA (7.6%), avian metapneumoviral RNA (6.6%), and infectious bursal disease viral RNA (3.7%). Polymerase chain reaction (PCR) on herpesvirus, avian influenza virus (AIV), paramyxovirus type 1 (PMV-1), avian encephalomyelitis virus (AEV), and chlamydia were negative. Based on the present results, there is no indication of a specific pathogen as a sole cause for population decline in adult pheasants. However, an infectious disease can still not be completely excluded as it may only affect reproduction effectivity or a certain age group of pheasants (e.g., chicks) which were not presented in the study.

Gangrenous dermatitis in chickens and turkeys

Gangrenous dermatitis (GD) is a disease of chickens and turkeys that causes severe economic losses in the poultry industry worldwide. Clostridium septicum, Clostridium perfringens type A, and occasionally Clostridium sordellii are considered the main causes of GD, although Staphylococcus aureus and other aerobic bacteria may also be involved in some cases of the disease. GD has become one of the most significant diseases of commercial turkeys in the United States. Several infectious and/or environmental immunosuppressive factors can predispose to GD. Skin lesions are considered to be the main portal of entry of the microorganism(s) involved. GD is characterized by acute onset of mortality associated with gross skin and subcutaneous tissue lesions consisting of variable amounts of serosanguineous exudate together with emphysema and hemorrhages. The underlying skeletal muscle can also be involved. Ulceration of the epidermis may be also noticed in cases complicated with S. aureus. Microscopically, necrosis of the epidermis and dermis, and subcutaneous edema and emphysema are commonly observed. Gram-positive rods can be identified within the subcutis and skeletal muscles, usually associated with minimal inflammatory infiltrate. A presumptive diagnosis of GD can be made based on history, clinical signs, and gross anatomic and microscopic lesions. However, confirmation should be based on demonstration of the causative agents by culture, PCR, immunohistochemistry, and/or fluorescent antibody tests.

Long-Term Dexamethasone Exposure Down-Regulates Hepatic TFR1 and Reduces Liver Iron Concentration in Rats

Exposure to stress is known to cause hepatic iron dysregulation, but the relationship between prolonged stress and liver iron metabolism is not yet fully understood. Thirty 13-week-old female Sprague-Dawley rats were randomly divided into two groups, as follows: the control group (saline-injection) and the dexamethasone group (Dexamethasone (Dex)-injection 0.1 mg/kg/day). After the 21-day stress trial, the results showed that chronic Dex administration not only impaired serum corticosterone (p = 0.00) and interleukin-6 (IL-6) (p = 0.01) levels, but also decreased white blood cell counts (p = 0.00), and reduced blood lymphocyte counts (p = 0.00). The daily Dex-injection also significantly reduced body weight (p < 0.01) by inhibiting food intake. Consecutive Dex administration resulted in decreased iron intake (p = 0.00), enhanced serum iron levels (p = 0.01), and increased the serum souble transferrin receptor (sTfR) content (p = 0.00) in rats. Meanwhile, long-term Dex exposure down-regulated duodenal cytochrome b (DCYTB) (p = 0.00) and the divalent metal transporter 1 (DMT1) (p = 0.04) protein expression, but up-regulated ferroportin (FPN) protein expression (p = 0.04). Chronic Dex administration reduced liver iron concentration (p = 0.02) in rats. Hepatic transferrin receptor 1 (TFR1) expression was lowered at the protein level (p = 0.03), yet with uncoupled mRNA abundance in Dex-treated rats. Enhanced iron-regulatory protein (IRP)/iron-responsive element (IRE) binding activity was observed, but did not line up with lowered hepatic TFR1 protein expression. This study indicates that long-term Dex exposure reduces liver iron content, which is closely associated with down-regulated hepatic TFR1 protein expression.