Ontogeny of the interferon system in chickens

The Expressions of the Immunity- and Muscle Development-Related Genes of 40-Day-Old Broilers Are Promoted in Response to the In Ovo and Dietary Supplemental Administration of Calcidiol in Conjunction with the In Ovo Administration of Marek's Disease Vaccine

Effects of in ovo and dietary sources of calcidiol (25(OH)D3), combined with Marek's disease vaccine (MDV), on the expression of genes involved with the antioxidant activity, muscle deposition, and immunity in the pectoralis major (P. major) muscle and spleen of 40 d of age (doa) broilers were investigated. The in ovo treatments were as follows: (1) non-injected; (2) the injection of 50 μL of commercial MDV, (3) MDV + 1.2, or (4) 2.4 μg of 25(OH)D3. All birds received either a commercial diet containing no supplemental 25(OH)D3 (control) or the same diet supplemented with an additional 69 µg of 25(OH)D3 per kg of feed (Hy-D diet). At 40 doa, the pectoralis major (P. major) muscle and spleen of 48 birds (six replicates per diet x in ovo treatment combination) were collected. When compared to un-supplemented commercial diet-fed birds, in birds that were fed the Hy-D diet, the expression of the TGF-β4 gene in the spleen and P. major muscle, and the GSH-P1, GSH-P7, SOD2, MyoG, MyoD1, and Pax3 genes in the P. major muscle were up-regulated, whereas the expression of the IL-1β, IL-8, and CYP24A1 genes in the spleen and P. major muscle were down-regulated. Nevertheless, birds that received any of the in ovo injection doses of 25(OH)D3 exhibited a higher expression of the IL-10, TGF-β4, and CYP27B1 genes in the spleen and P. major muscle. Furthermore, in comparison to the MDV-injected control group, the CAT, MyoD1, and Pax3 genes in the P. major muscle were up-regulated, and the expression of the INF-γ, IL-1β and CYP24A1 genes in the spleen and the IL-8, and IL-1β genes in the P. major muscle were down-regulated. In conclusion, a significant improvement in the expression of genes responsible for enzymatic antioxidant activity, protein synthesis, and inflammatory reactions in 40-day-old broilers occurred in response to in ovo and dietary supplemental 25(OH)D3, and supplemental 25OHD3 provided via either route was used to enhance the expression of genes linked to vitamin D activity (CYP27B1, CYP24A1).

Enhancements in the expressions of genes associated with the immunity, muscle growth, and antioxidant activity of 14 d broilers in response to the in ovo injection of the Marek's disease vaccine alone or in conjunction with the in ovo and dietary supplemental administration of 25-hydroxycholecalciferol

Influences the Marek's disease vaccine (MDV) alone or combined with the in ovo and dietary administration of 25-hydroxycholecalciferol (25OHD3) on the expression of genes associated with the breast muscle deposition, adaptive and innate immunity, and antioxidant and vitamin D activities of 14 d-old broilers were investigated. Four in ovo treatments were: noninjected; commercial MDV-alone-injected (50 μl); or 50 μl of MDV containing 1.2 (MDV+25OHD3-1.2) or 2.4 (MDV+25OHD3-2.4) μg of 25OHD3. Two dietary treatments were a commercial diet containing 25OHD3 (250 IU)/kg of feed (control) or the same diet supplemented with additional 25OHD3 (2,760 IU)/kg of feed (Hy-D diet). One bird per pen (48 total) was sampled at 14 d for determination of the expression of genes involved with the muscle deposition (MyoD1, MyoG, Pax3, and Mrf4), immunity (INF-γ, IL-10, IL-8, IL-1β, and TGF-β4), antioxidant capacity (SOD1, SOD2, GSH-P1, GSH-P7, and CAT), and vitamin D activity (VDR, 1α-hydroxylase, and 24-hydroxylase) in the spleen and pectoralis major (P.major) muscle. The treatment differences were considered significant at P ≤ 0.05. In the P. major, Mrf4 and MyoG were up-regulated in Hy-D-fed birds. Also, the in ovo and dietary 25OHD3 sources individually increased SOD2 gene expression in the P. major. In the spleen, the expressions of IL-1β and IL-8 were down-regulated and IL-10 and TGF-β4 gene expressions were up-regulated in Hy-D-fed birds than those commercial-fed broiler. In ovo and dietary 25OHD3 sources enhanced vitamin D gene (1α-hydroxylase and 24-hydroxylase) activities in the breast and spleen. In ovo x dietary treatment interactions were significant for the MyoD1, IL-8, Pax3, TGF-β4 genes of the P. major, in which the combined MDV with 1.2 μg of 25OHD3 enhanced their expressions in birds fed the Hy-D diet. In conclusion, both 25OHD3 sources promoted the expression of genes associated with immunity and P. major growth. It is recommended that both 25OHD3 sources can be used to promote the gene expression of 14-day-old broilers in the spleen and breast muscle when MDV administered in ovo.

An alternative strategy to increasing influenza virus replication for vaccine production in chicken embryo fibroblast (DF-1) cells by inhibiting interferon alpha and beta using peptide-conjugated phosphorodiamidate morpholino oligomers

Introduction. Influenza is a global health issue causing substantial health and economic burdens on affected populations. Routine, annual vaccination for influenza virus is recommended for all persons older than 6 months of age. The propagation of the influenza virus for vaccine production is predominantly through embryonated chicken eggs.Hypothesis/Gap Statement. Many challenges face the propagation of the virus, including but not limited to low yields and lengthy production times. The development of a method to increase vaccine production in eggs or cell lines by suppressing cellular gene expression would be helpful to overcome some of the challenges facing influenza vaccine production.Aims. This study aimed to increase influenza virus titres by using a peptide-conjugated phosphorodiamidate morpholino oligomer (PPMO), an antisense molecule, to suppress protein expression of the host genes interferon alpha (IFN-α) and interferon beta (IFN-β) in chicken embryo fibroblast (DF-1) cells.Methods. The toxicity of PPMOs was evaluated by cytotoxicity assays, and their specificity to inhibit IFN-α and IFN-β proteins was measured by ELISA. We evaluated the potential of anti-IFN-α and anti-IFN-β PPMOs to reduce the antiviral proteins in influenza virus-infected DF-1 cells and compared the virus titres to untreated controls, nonsense-PPMO and JAK/STAT inhibitors. The effects of complementation and reconstitution of IFN-α and IFN-β proteins in PPMO-treated-infected cells were evaluated, and the virus titres were compared between treatment groups.Results. Suppression of IFN-α by PPMO resulted in significantly reduced levels of IFN-α protein in treated wells, as measured by ELISA and was shown to not have any cytotoxicity to DF-1 cells at the effective concentrations tested. Treatment of the self-directing PPMOs increased the ability of the influenza virus to replicate in DF-1 cells. Over a 2-log10 increase in viral production was observed in anti-IFN-α and IFN-β PPMO-treated wells compared to those of untreated controls at the initial viral input of 0.1 multiplicity of infection. The data from complementation and reconstitution of IFN-α and IFN-β proteins in PPMO-treated-infected cells was about 82 and 97% compared to the combined PPMO-treated but uncomplemented group and untreated group, respectively. There was a 0.5-log10 increase in virus titre when treated with anti-IFN-α and IFN-β PPMO compared to virus titre when treated with JAK/STAT inhibitors.Conclusions. This study emphasizes the utility of PPMO in allowing cell cultures to produce increased levels of influenza for vaccine production or alternatively, as a screening tool to cheaply test targets prior to the development of permanent knockouts of host gene expression.

Immune parameters in two different laying hen strains during five production periods

During life, the number and function of immune cells change with potential consequences for immunocompetence of an organism. In laying hens, studies have primarily focused on early development of immune competence and only few have investigated systemic and lymphatic distribution of leukocyte subsets during adolescence and the egg-laying period. The present study determined the number of various leukocyte types in blood, spleen, and cecal tonsils of 10 Lohmann Brown-Classic and 10 Lohmann LSL-Classic hens per wk of life 9/10, 15/16, 23/24, 29/30, and 59/60, encompassing important production as well as developmental stages, by flow cytometry. Although immune traits differed between the 2 hen strains, identical patterns of age-related immunological changes were found. The numbers of all investigated lymphocyte types in the spleen as well as the numbers of blood γδ T cells increased from wk 9/10 to 15/16. This suggests an ongoing release of lymphocytes from primary lymphoid tissues and an influx of blood lymphocytes into the spleen due to novel pathogen encounters during adolescence. A strong decrease in the number of CTL and γδ T cells and an increase in innate immune cells within blood and spleen were found between wk of life 15/16 and 23/24, covering the transition phase to egg-laying activity. Numbers of peripheral and splenic lymphocytes remained low during the egg-laying period or even further decreased, for example blood CD4⁺ T cells and splenic γδ T cells. Functional assessments showed that in vitro IFN-γ production of mitogen-stimulated splenocytes was lower in wk 60. Taken together, egg-laying activity seems to alter the immune system toward a more pronounced humoral and innate immune response, with probable consequences for the immunocompetence and thus for productivity, health and welfare of the hens.

The Potential of Toll-Like Receptors to Modulate Avian Immune System: Exploring the Effects of Genetic Variants and Phytonutrients

Toll-like receptors (TLRs) are pathogen recognition receptors, and primitive sources of innate immune response that also play key roles in the defense mechanism against infectious diseases. About 10 different TLRs have been discovered in chicken that recognize ligands and participate in TLR signaling pathways. Research findings related to TLRs revealed new approaches to understand the fundamental mechanisms of the immune system, patterns of resistance against diseases, and the role of TLR-specific pathways in nutrient metabolism in chicken. In particular, the uses of specific feed ingredients encourage molecular biologists to exploit the relationship between nutrients (including different phytochemicals) and TLRs to modulate immunity in chicken. Phytonutrients and prebiotics are noteworthy dietary components to promote immunity and the production of disease-resistant chicken. Supplementations of yeast-derived products have also been extensively studied to enhance innate immunity during the last decade. Such interventions pave the way to explore nutrigenomic approaches for healthy and profitable chicken production. Additionally, single-nucleotide polymorphisms in TLRs have shown potential association with few disease outbreaks in chickens. This review aimed to provide insights into the key roles of TLRs in the immune response and discuss the potential applications of these TLRs for genomic and nutritional interventions to improve health, and resistance against different fatal diseases in chicken.

Cytokine expression in the eye and brain of chickens following infection with a very virulent plus Marek's disease virus strain

Cytokine transcripts were evaluated chronologically in the brain and in the eye of chickens infected with the very virulent plus Marek's disease virus (vv + MDV) strain 648A. Brain and eye samples were collected from chickens that were either suffering from transient paralysis (TP) (11 days post inoculation, dpi) or had completely recovered from TP but started developing clinical signs of persistent neurological disease (PND) (18-31 dpi). Results obtained from samples collected at 11 dpi are referred as EL (early lesions) and results obtained from samples collected at later times (18-31 dpi) are referred as LL (late lesions). Marked differences were found in the cytokine transcripts in brain and eye. While proinflammatory cytokines (IL-1β, IL-8, IL-18), iNOS, IFN-α, IFN-γ, and IL-15 were upregulated in the brain during EL and LL, only IL-8 and IFN-γ were upregulated in the eye at both times (EL and LL). The two evaluated viral transcripts (gB and meq) were found in both eye and brain during EL and LL. Levels of the two viral transcripts evaluated were higher at LL than at EL in both brain and eye. No differences were found in any of the viral transcripts between eye and brain during EL. However, during the LL, the levels of meq transcripts were higher in the eye than in the brain. Our results suggest that MDV elicits different immune responses in the brain and in the eye of infected chickens. Because immune responses in the eye of chickens have been poorly studied, further studies on the pathogenesis of MDV in the eye could greatly contribute to our knowledge on the chicken eye immunity.

Comprehensive network map of transcriptional activation of chicken type I IFNs and IFN-stimulated genes

Chicken type I interferons (type I IFNs) are key antiviral players of the chicken immune system and mediate the first line of defense against viral pathogens infecting the avian species. Recognition of viral pathogens by specific pattern recognition receptors (PRRs) induce chicken type I IFNs expression followed by their subsequent interaction to IFN receptors and induction of a variety of IFN stimulated antiviral proteins. These antiviral effectors establish the antiviral state in neighboring cells and thus protect the host from infection. Three subtypes of chicken type I IFNs; chIFN-α, chIFN-β, and a recently discovered chIFN-κ have been identified and characterized in chicken. Chicken type I IFNs are activated by various host cell pathways and constitute a major antiviral innate defense in chicken. This review will help to understand the chicken type 1 IFNs, host cellular pathways that are involved in activation of chicken type I IFNs and IFN stimulated antiviral effectors along with the gaps in knowledge which will be important for future investigation. These findings will help us to comprehend the role of chicken type I IFNs and to develop different strategies for controlling viral infection in poultry.

Development of innate immunity in chicken embryos and newly hatched chicks: a disease control perspective

Newly hatched chickens are confronted by a wide array of pathogenic microbes because their adaptive immune defences have limited capabilities to control these pathogens. In such circumstances, and within this age group, innate responses provide a degree of protection. Moreover, as the adaptive immune system is relatively naïve to foreign antigens, synergy with innate defences is critical. This review presents knowledge on the ontogeny of innate immunity in chickens pre-hatch and early post-hatch and provides insights into possible interventions to modulate innate responses early in the life of the bird. As in other vertebrate species, the chicken innate immune system which include cellular mediators, cytokine and chemokine repertoires and molecules involved in antigen detection, develop early in life. Comparison of innate immune systems in newly hatched chickens and mature birds has revealed differences in magnitude and quality, but responses in younger chickens can be boosted using innate immune system modulators. Functional expression of pattern recognition receptors and several defence molecules by innate immune system cells of embryos and newly hatched chicks suggests that innate responses can be modulated at this stage of development to combat pathogens. Improved understanding of innate immune system ontogeny and functionality in chickens is critical for the implementation of sound and safe interventions to provide long-term protection against pathogens. Next-generation tools for studying genetic and epigenetic regulation of genes, functional metagenomics and gene knockouts can be used in the future to explore and dissect the contributions of signalling pathways of innate immunity and to devise more efficacious disease control strategies.

Attenuation of Bluetongue Virus (BTV) in an in ovo Model Is Related to the Changes of Viral Genetic Diversity of Cell-Culture Passaged BTV

The embryonated chicken egg (ECE) is routinely used for the laboratory isolation and adaptation of Bluetongue virus (BTV) in vitro. However, its utility as an alternate animal model has not been fully explored. In this paper, we evaluated the pathogenesis of BTV in ovo using a pathogenic isolate of South African BTV serotype 3 (BTV-3) derived from the blood of an infected sheep. Endothelio- and neurotropism of BTV-3 were observed by immunohistochemistry of non-structural protein 1 (NS1), NS3, NS3/3a, and viral protein 7 (VP7) antigens. In comparing the pathogenicity of BTV from infectious sheep blood with cell-culture-passaged BTV, including virus propagated through a Culicoides-derived cell line (KC) or ECE, we found virus attenuation in ECE following cell-culture passage. Genomic analysis of the consensus sequences of segments (Seg)-2, -5, -6, -7, -8, -9, and -10 identified several nucleotide and amino-acid mutations among the cell-culture-propagated BTV-3. Deep sequencing analysis revealed changes in BTV-3 genetic diversity in various genome segments, notably a reduction of Seg-7 diversity following passage in cell culture. Using this novel approach to investigate BTV pathogenicity in ovo, our findings support the notion that pathogenic BTV becomes attenuated in cell culture and that this change is associated with virus quasispecies evolution.

Recombinant live attenuated avian coronavirus vaccines with deletions in the accessory genes 3ab and/or 5ab protect against infectious bronchitis in chickens

Avian coronavirus infectious bronchitis virus (IBV) is a respiratory pathogen of chickens, causing severe economic losses in poultry industry worldwide. Live attenuated viruses are widely used in both the broiler and layer industry because of their efficacy and ability to be mass applied. Recently, we established a novel reverse genetics system based on targeted RNA recombination to manipulate the genome of IBV strain H52. Here we explore the possibilities to attenuate IBV in a rational way in order to generate safe and effective vaccines against virulent IBV (van Beurden et al., 2017). To this end, we deleted the nonessential group-specific accessory genes 3 and/or 5 in the IBV genome by targeted RNA recombination and selected the recombinant viruses in embryonated eggs. The resulting recombinant (r) rIBV-Δ3ab, rIBV-Δ5ab, and rIBV-Δ3ab5ab could be rescued and grew to the same virus titer as recombinant and wild type IBV strain H52. Thus, genes 3ab and 5ab are not essential for replication in ovo. When administered to one-day-old chickens, rIBV-Δ3ab, rIBV-Δ5ab, and rIBV-Δ3ab5ab showed reduced ciliostasis as compared to rIBV H52 and wild type H52, indicating that the accessory genes contribute to the pathogenicity of IBV. After homologous challenge with the virulent IBV strain M41, all vaccinated chickens were protected against disease based on reduced loss of ciliary movement in the trachea compared to the non-vaccinated but challenged controls. Taken together, deletion of accessory genes 3ab and/or 5ab in IBV resulted in mutant viruses with an attenuated phenotype and the ability to induce protection in chickens. Hence, targeted RNA recombination based on virulent IBV provides opportunities for the development of a next generation of rationally designed live attenuated IBV vaccines.

Zika Virus Exhibits Lineage-Specific Phenotypes in Cell Culture, in Aedes aegypti Mosquitoes, and in an Embryo Model

Zika virus (ZIKV) has quietly circulated in Africa and Southeast Asia for the past 65 years. However, the recent ZIKV epidemic in the Americas propelled this mosquito-borne virus to the forefront of flavivirus research. Based on historical evidence, ZIKV infections in Africa were sporadic and caused mild symptoms such as fever, skin rash, and general malaise. In contrast, recent Asian-lineage ZIKV infections in the Pacific Islands and the Americas are linked to birth defects and neurological disorders. The aim of this study is to compare replication, pathogenicity, and transmission efficiency of two historic and two contemporary ZIKV isolates in cell culture, the mosquito host, and an embryo model to determine if genetic variation between the African and Asian lineages results in phenotypic differences. While all tested isolates replicated at similar rates in Vero cells, the African isolates displayed more rapid viral replication in the mosquito C6/36 cell line, yet they exhibited poor infection rates in Aedes aegypti mosquitoes compared to the contemporary Asian-lineage isolates. All isolates could infect chicken embryos; however, infection with African isolates resulted in higher embryo mortality than infection with Asian-lineage isolates. These results suggest that genetic variation between ZIKV isolates can significantly alter experimental outcomes.

Hatchery Vaccination Against Poultry Viral Diseases: Potential Mechanisms and Limitations

Commercial broiler and layer chickens are heavily vaccinated against economically important viral diseases with a view of preventing morbidity, mortality, and production impacts encountered during short production cycles. Hatchery vaccination is performed through in ovo embryo vaccination prehatch or spray and subcutaneous vaccinations performed at the day of hatch before the day-old chickens are being placed in barns with potentially contaminated environments. Commercially, multiple vaccines (e.g., live, live attenuated, and viral vectored vaccines) are available to administer through these routes within a short period (embryo day 18 prehatch to day 1 posthatch). Although the ability to mount immune response, especially the adaptive immune response, is not optimal around the hatch, it is possible that the efficacy of these vaccines depends partly on innate host responses elicited in response to replicating vaccine viruses. This review focuses on the current knowledge of hatchery vaccination in poultry and potential mechanisms of hatchery vaccine-mediated protective responses and limitations.

Avian Interferons and Their Antiviral Effectors

Interferon (IFN) responses, mediated by a myriad of IFN-stimulated genes (ISGs), are the most profound innate immune responses against viruses. Cumulatively, these IFN effectors establish a multilayered antiviral state to safeguard the host against invading viral pathogens. Considerable genetic and functional characterizations of mammalian IFNs and their effectors have been made, and our understanding on the avian IFNs has started to expand. Similar to mammalian counterparts, three types of IFNs have been genetically characterized in most avian species with available annotated genomes. Intriguingly, chickens are capable of mounting potent innate immune responses upon various stimuli in the absence of essential components of IFN pathways including retinoic acid-inducible gene I, IFN regulatory factor 3 (IRF3), and possibility IRF9. Understanding these unique properties of the chicken IFN system would propose valuable targets for the development of potential therapeutics for a broader range of viruses of both veterinary and zoonotic importance. This review outlines recent developments in the roles of avian IFNs and ISGs against viruses and highlights important areas of research toward our understanding of the antiviral functions of IFN effectors against viral infections in birds.

Avian metapneumovirus infection of chicken and turkey tracheal organ cultures: comparison of virus-host interactions

Avian metapneumovirus (aMPV) is a pathogen with worldwide distribution, which can cause high economic losses in infected poultry. aMPV mainly causes infection of the upper respiratory tract in both chickens and turkeys, although turkeys seem to be more susceptible. Little is known about virus-host interactions at epithelial surfaces after aMPV infection. Tracheal organ cultures (TOC) are a suitable model to investigate virus-host interaction in the respiratory epithelium. Therefore, we investigated virus replication rates and lesion development in chicken and turkey TOC after infection with a virulent aMPV subtype A strain. Aspects of the innate immune response, such as interferon-α and inducible nitric oxide synthase mRNA expression, as well as virus-induced apoptosis were determined. The aMPV-replication rate was higher in turkey (TTOC) compared to chicken TOC (CTOC) (P < 0.05), providing circumstantial evidence that indeed turkeys may be more susceptible. The interferon-α response was down-regulated from 2 to 144 hours post infection in both species compared to virus-free controls (P < 0.05); this was more significant for CTOC than TTOC. Inducible nitric oxide synthase expression was significantly up-regulated in aMPV-A-infected TTOC and CTOC compared to virus-free controls (P < 0.05). However, the results suggest that NO may play a different role in aMPV pathogenesis between turkeys and chickens as indicated by differences in apoptosis rate and lesion development between species. Overall, our study reveals differences in innate immune response regulation and therefore may explain differences in aMPV - A replication rates between infected TTOC and CTOC, which subsequently lead to more severe clinical signs and a higher rate of secondary infections in turkeys.

Previous infection with virulent strains of Newcastle disease virus reduces highly pathogenic avian influenza virus replication, disease, and mortality in chickens

Highly pathogenic avian influenza virus (HPAIV) and Newcastle disease virus (NDV) are two of the most important viruses affecting poultry worldwide and produce co-infections especially in areas of the world where both viruses are endemic; but little is known about the interactions between these two viruses. The objective of this study was to determine if co-infection with NDV affects HPAIV replication in chickens. Only infections with virulent NDV strains (mesogenic Pigeon/1984 or velogenic CA/2002), and not a lentogenic NDV strain (LaSota), interfered with the replication of HPAIV A/chicken/Queretaro/14588-19/95 (H5N2) when the H5N2 was given at a high dose (10^6.9 EID₅₀) two days after the NDV inoculation, but despite this interference, mortality was still observed. However, chickens infected with the less virulent mesogenic NDV Pigeon/1984 strain three days prior to being infected with a lower dose (10^5.3–5.5 EID₅₀) of the same or a different HPAIV, A/chicken/Jalisco/CPA-12283-12/2012 (H7N3), had reduced HPAIV replication and increased survival rates. In conclusion, previous infection of chickens with virulent NDV strains can reduce HPAIV replication, and consequently disease and mortality. This interference depends on the titer of the viruses used, the virulence of the NDV, and the timing of the infections. The information obtained from these studies helps to understand the possible interactions and outcomes of infection (disease and virus shedding) when HPAIV and NDV co-infect chickens in the field.

Identification of Type II Interferon Receptors in Geese: Gene Structure, Phylogenetic Analysis, and Expression Patterns

Interferon γ receptor 1 (IFNGR1) and IFNGR2 are two cell membrane molecules belonging to class II cytokines, which play important roles in the IFN-mediated antiviral signaling pathway. Here, goose IFNGR1 and IFNGR2 were cloned and identified for the first time. Tissue distribution analysis revealed that relatively high levels of goose IFNγ mRNA transcripts were detected in immune tissues, including the harderian gland, cecal tonsil, cecum, and thymus. Relatively high expression levels of both IFNGR1 and IFNGR2 were detected in the cecal tonsil, which implicated an important role of IFNγ in the secondary immune system of geese. No specific correlation between IFNγ, IFNGR1, and IFNGR2 expression levels was observed in the same tissues of healthy geese. IFNγ and its cognate receptors showed different expression profiles, although they appeared to maintain a relatively balanced state. Furthermore, the agonist R848 led to the upregulation of goose IFNγ but did not affect the expression of goose IFNGR1 or IFNGR2. In summary, trends in expression of goose IFNγ and its cognate receptors showed tissue specificity, as well as an age-related dependency. These findings may help us to better understand the age-related susceptibility to pathogens in birds.

Preterm birth, intrauterine infection, and fetal inflammation

Preterm birth (PTB) (delivery before 37 weeks’ gestation) is a leading cause of neonatal death and disease in industrialized and developing countries alike. Infection (most notably in high-risk deliveries occurring before 28 weeks’ gestation) is hypothesized to initiate an intrauterine inflammatory response that plays a key role in the premature initiation of labor as well as a host of the pathologies associated with prematurity. As such, a better understanding of intrauterine inflammation in pregnancy is critical to our understanding of preterm labor and fetal injury, as well as on-going efforts to prevent PTB. Focusing on the fetal innate immune system responses to intrauterine infection, the present paper will review clinical and experimental studies to discuss the capacity for a fetal contribution to the intrauterine inflammation associated with PTB. Evidence from experimental studies to suggest that the fetus has the capacity to elicit a pro-inflammatory response to intrauterine infection is highlighted, with reference to the contribution of the lung, skin, and gastrointestinal tract. The paper will conclude that pathological intrauterine inflammation is a complex process that is modified by multiple factors including time, type of agonist, host genetics, and tissue.

Interferons and Their Receptors in Birds: A Comparison of Gene Structure, Phylogenetic Analysis, and Cross Modulation

Interferon may be thought of as a key, with the interferon receptor as the signal lock: Crosstalk between them maintains their balance during viral infection. In this review, the protein structure of avian interferon and the interferon receptor are discussed, indicating remarkable similarity between different species. However, the structures of the interferon receptors are more sophisticated than those of the interferons, suggesting that the interferon receptor is a more complicated signal lock system and has considerable diversity in subtypes or structures. Preliminary evolutionary analysis showed that the subunits of the interferon receptor formed a distinct clade, and the orthologs may be derived from the same ancestor. Furthermore, the development of interferons and interferon receptors in birds may be related to an animal’s age and the maintenance of a balanced state. In addition, the equilibrium between interferon and its receptor during pathological and physiological states revealed that the virus and the host influence this equilibrium. Birds could represent an important model for studies on interferon’s antiviral activities and may provide the basis for new antiviral strategies.

The differential antiviral activities of chicken interferon α (ChIFN-α) and ChIFN-β are related to distinct interferon-stimulated gene expression

Chicken interferon α (ChIFN-α) and ChIFN-β are type I IFNs that are important antiviral cytokines in the innate immune system. In the present study, we identified the virus-induced expression of ChIFN-α and ChIFN-β in chicken fibroblast DF-1 cells and systematically evaluated the antiviral activities of recombinant ChIFN-α and ChIFN-β by cytopathic-effect (CPE) inhibition assays. We found that ChIFN-α exhibited stronger antiviral activity than ChIFN-β in terms of inhibiting the replication of vesicular stomatitis virus, Newcastle disease virus and avian influenza virus, respectively. To elucidate the mechanism of differential antiviral activities between the two ChIFNs, we measured the relative mRNA levels of IFN-stimulated genes (ISGs) in IFN-treated DF-1 cells by real-time PCR. ChIFN-α displayed greater induction potency than ChIFN-β on several ISGs encoding antiviral proteins and MHC-I, whereas ChIFN-α was less potent than ChIFN-β for inducing ISGs involved in signaling pathways. In conclusion, ChIFN-α and ChIFN-β presented differential induction potency on various sets of ISGs, and the stronger antiviral activity of ChIFN-α is likely attributed to the greater expression levels of downstream antiviral ISGs.

Reassortment of NS segments modifies highly pathogenic avian influenza virus interaction with avian hosts and host cells

Highly pathogenic avian influenza viruses (HPAIV) of subtypes H5 and H7 have caused numerous outbreaks in diverse poultry species and rising numbers of human infections. Both HPAIV subtypes support a growing concern of a pandemic outbreak, specifically via the avian-human link. Natural reassortment of both HPAIV subtypes is a possible event with unpredictable outcome for virulence and host specificity of the progeny virus for avian and mammalian species. NS reassortment of H5N1 HPAIV viruses in the background of A/FPV/Rostock/1934 (H7N1) HPAIV has been shown to change virus replication kinetics and host cell responses in mammalian cells. However, not much is known about the virus-host interaction of such viruses in avian species. In the present study, we show that the NS segment of A/Vietnam/1203/2004 (FPV NS VN, H5N1) HPAIV significantly altered the characteristics of the H7 prototype HPAIV in tracheal organ cultures (TOC) of chicken and turkey in vitro, with decreased replication efficiency accompanied by increased induction of type I interferon (IFN) and apoptosis. Furthermore, species-specific differences between chicken and turkey were demonstrated. Interestingly, NS-reassortant FPV NS VN showed an overall highly pathogenic phenotype, with increased virulence and replication potential compared to the wild-type virus after systemic infection of chicken and turkey embryos. Our data demonstrate that single reassortment of an H5-type NS into an H7-type HPAIV significantly changed virus replication abilities and influenced the avian host cell response without prior adaptation.