Characterization of the porcine alpha interferon multigene family

Molecular characterization, tissue expression, and antiviral activities of Bama minipig interferon-α subtypes

Interferons play a major role in innate immunity and disease resistance. Porcine interferon alpha has 17 subtypes, and their gene sequences, tissue expression profiles, and antiviral activities have been primarily studied in domestic pigs but not in minipigs. Bama minipigs are genetically stable disease-resistant and making them as laboratory animal models for bioscience studies. To define the potential mechanism for disease resistance, in this study, we cloned 17 subtypes of Porcine interferon alpha genes in Bama minipigs using high fidelity polymerase chain reaction and subsequent sequencing. Sequence alignment showed that the 17 porcine interferon alpha subtypes were 98%-100 % homologous in those of domestic pigs. However, significantly different tissue expression profiles of PoIFN-α subtypes were found in the two pig species using real-time quantitative RT-PCR. Among the 10 different Bama minipig tissues tested, significant expression of multi-subtype porcine interferon alpha was detected in the lymph nodes and spleen, whereas no or low expression of fewer subtypes was detected in the heart, lung, brain, and small intestine. Sequence analysis revealed that the porcine interferon alpha promoters were almost similar between the two pig species. A cytopathic effect inhibition assay showed that the recombinant 17 porcine interferon alpha subtypes purified from mammalian cells had significantly different antiviral profile against vesicular stomatitis virus, porcine pseudorabies virus and porcine reproductive and respiratory syndrome virus compared with those in domestic pigs. Our findings provide evidence that porcine interferon alpha subtypes are highly conserved between Bama minipigs and domestic pigs but show varied tissue expression pattern and antiviral capabilities, which may contribute to their differences in disease resistance.

Analysis of the Differential Expression and Antiviral Activity of Porcine Interferon-α In Vitro

Porcine interferon α (poIFN-α) is a crucial cytokine that can prevent and treat viral infections. Seventeen functional porcine IFN-α subtypes were found in the porcine genome. In this study, multiple sequence alignment was performed to analyze IFN-α protein structure and function. Phylogenetic tree analysis of the poIFN gene family defined the evolutionary relationship of various subtypes. PoIFN-αs, including poIFN-α1-17, were expressed in an Escherichia coli expression system. The antiviral activities of these IFN-α proteins against vesicular stomatitis virus (VSV) and pseudorabies virus (PRV) were examined in PK-15 cells. We found that the antiviral activity of different poIFN-α molecules greatly differed as follows: the poIFN-α14 and 17 subtypes had the greatest antiviral activities against VSV and PRV in PK-15 cells, poIFN-α1, 2, 3, and 8 exhibited lower biological activities, and poIFN-α4, 5, 6, 7, 9, 10, 11, 12, 13, and 16 had minimal or no effect in the tested target cell‒virus systems. Moreover, our studies demonstrated that the antiviral activity of IFN-α was positively correlated with the induction of IFN-stimulated genes, such as 2'-5' oligoadenylate synthetase 1 (OSA1), interferon-stimulated gene 15 (ISG15), myxoma resistance protein 1 (Mx1), and protein kinase R (PKR). Thus, our experimental results provide important information about the antiviral functions and mechanism of poIFN-α.

In vitro evaluation of immunomodulatory activities of goat milk Extracellular Vesicles (mEVs) in a model of gut inflammation

Gut represents a major immunological defense barrier with mucosal immune system and intestinal epithelial cells (IECs). In all intestinal diseases, in particular inflammatory bowel disease (IBD), both the absorption and the local immune system are compromised and alternative effective therapies are sought after. Extracellular Vesicles (EVs) have the capability to regulate immune cells within the inflammatory microenvironment, by dampening inflammation and restoring intestinal barrier integrity. Recently, the immune-modulatory role of EVs has also been confirmed for milk EVs (mEVs), notable for their easy production, high sample volumes, cost-effective scalable production and non-toxic and non-immunogenic behavior. In this context, the aim of this study was to evaluate goat mEV anti-inflammatory and immuno-modulating effects on an in vitro model (IPEC-J2) of intestinal inflammation through gene expression evaluation with RT-qPCR and cytokine release dosage with ELISA test. After the establishment of a pro-inflammatory environment due to LPS stimuli, IL6, CXCL8, IL12p35, IL12p40, IFNB, IL18, TLR7 and NOS2 resulted significantly up-regulated in stimulated IPEC-J2 cells compared to those of the basal culture. After 48 h of mEV treatment in inflamed IPEC-J2 a partial restoration of initial conditions was detected, with the IL18 and IL12p40 significant down-regulation, and IL12p35, EBI3, TLR7, BD1 and BD3 up-regulation. IL-18 reduced protein production was also detected in supernatants. Moreover, a decrease of MMP9 and NOS2 together with a strong up-regulation of MUC2 indicated a recovery of cellular homeostasis and, therefore, potential beneficial effects on the intestinal mucosa. Nevertheless, 48 h post-treatment, an increased gene expression and protein release of IL-8 was observed. This paper is one of the firsts to assess the effect of goat mEVs and the first one, in particular, of doing this on an in vitro model of gut inflammation. The obtained results show a potential capability of goat mEVs to modulate inflammation and to play beneficial effects on the intestinal mucosa.

Gene Cloning, Tissue Expression Profiles and Antiviral Activities of Interferon-β from Two Chinese Miniature Pig Breeds

The porcine interferon (PoIFN) complex represents an ideal model for studying IFN evolution which has resulted from viral pressure during domestication. Bama and Banna miniature pigs are the two Chinese miniature pig breeds that have been developed as laboratory animal models for studying virus infection, pathogenesis, and vaccine evaluation. However, the PoIFN complex of such miniature pig breeds remains to be studied. In the present study, we cloned PoIFN-β genes from Bama and Banna miniature pigs, detected their PoIFN-β tissue expression profiles, prepared recombinant PoIFN-β (rPoIFN-β) using the E. coli expression system, and measured their antiviral activities against three different pig viruses. At the amino acid sequence level, PoIFN-βs of the two miniature pig breeds were identical, which shared 100% identity with that of Congjiang Xiang pigs, 99.4–100% identity with that of domestic pigs, and 99.5% identity with that of three species of African wild boars. The tissue expression profiles of PoIFN-β mRNA differed not only between the two miniature pig breeds but between miniature pigs and domestic pigs as well. The four promoter domains of PoIFN-β of the two miniature pig breeds were identical with that of humans, domestic pigs, and three species of African wild boars. The recombinant PoIFN-β prepared from the two miniature pig breeds showed dose-dependent pre-infection and post-infection antiviral activities against vesicular stomatitis virus, porcine respiratory and reproductive syndrome virus, and pig pseudorabies virus. This study provided evidence for the high sequence conservation of PoIFN-β genes within the Suidae family with different tissue expression profiles and antiviral activities.

Cadmium and wild boar: Environmental exposure and immunological impact on macrophages

Cadmium (Cd2+) is regarded as one of the most toxic heavy metals, which can enter the food chain through environmental contamination and be bioaccumulated. Its exposure in Ligurian wild boars was monitored between 2016-2020 and revealed high level of this heavy metal in different provinces. In one of these polluted area, 21 wild boars were additionally sampled and the relationship between hepatic and renal Cd2+ concentration suggested that majority of these animals presented chronic intoxication. Cd2+ exposure of wild boar might lead to an immunosuppression status, thus in vitro experiments on wild boar monocyte-derived macrophages (moMФ) were carried out. Effects of Cd2+ scalar doses were evaluated through viability and adsorption assays, ELISA, qPCR. Moderate doses of this environmental pollutant (20 μM) were absorbed by moMФ, with subsequent reduction of their viability. This heavy metal did not trigger release of either IFN- β, anti-inflammatory or pro-inflammatory cytokines by moMФ, instead 24 h treatment with 20 μM of Cd2+ resulted in down-regulated expression of TNF-α, IL-12p40, several TLRs, CD14, MD2, BD2, MyD88, p65, and NOS2. The results of our monitoring activity suggested that wild boar can be useful to monitor environmental exposure of this heavy metal and can help in understanding the type of contamination. In addition, in vitro experiments on wild boar moMФ revealed that Cd2+ exposure negatively affected the immune function of these cells, likely leading to increased susceptibility to infection.

The Swine IFN System in Viral Infections: Major Advances and Translational Prospects

Interferons (IFNs) are a family of cytokines that play a pivotal role in orchestrating the innate immune response during viral infections, thus representing the first line of defense in the host. After binding to their respective receptors, they are able to elicit a plethora of biological activities, by initiating signaling cascades which lead to the transcription of genes involved in antiviral, anti-inflammatory, immunomodulatory and antitumoral effector mechanisms. In hindsight, it is not surprising that viruses have evolved multiple IFN escape strategies toward efficient replication in the host. Hence, in order to achieve insight into preventive and treatment strategies, it is essential to explore the mechanisms underlying the IFN response to viral infections and the constraints thereof. Accordingly, this review is focused on three RNA and three DNA viruses of major importance in the swine farming sector, aiming to provide essential data as to how the IFN system modulates the antiviral immune response, and is affected by diverse, virus-driven, immune escape mechanisms.

Targeting Toll-Like Receptor 2: Polarization of Porcine Macrophages by a Mycoplasma-Derived Pam2cys Lipopeptide

Toll-like receptor 2 (TLR2) ligands are attracting increasing attention as prophylactic and immunotherapeutic agents against pathogens and tumors. We previously observed that a synthetic diacylated lipopeptide based on a surface protein of Mycoplasma agalactiae (Mag-Pam2Cys) strongly activated innate immune cells, including porcine monocyte-derived macrophages (moMΦ). In this study, we utilized confocal microscopy, flow cytometry, multiplex cytokine ELISA, and RT-qPCR to conduct a comprehensive analysis of the effects of scalar doses of Mag-Pam2Cys on porcine moMΦ. We observed enhanced expression of activation markers (MHC class I, MHC class II DR, CD25), increased phagocytotic activity, and release of IL-12 and proinflammatory cytokines. Mag-Pam2Cys also upregulated the gene expression of several IFN-α subtypes, p65, NOS2, and molecules with antimicrobial activities (CD14, beta defensin 1). Overall, our data showed that Mag-Pam2Cys polarized porcine macrophages towards a proinflammatory antimicrobial phenotype. However, Mag-Pam2Cys downregulated the expression of IFN-α3, six TLRs (TLR3, -4, -5, -7, -8, -9), and did not interfere with macrophage polarization induced by the immunosuppressive IL-10, suggesting that the inflammatory activity evoked by Mag-Pam2Cys could be regulated to avoid potentially harmful consequences. We hope that our in vitro results will lay the foundation for the further evaluation of this diacylated lipopeptide as an immunopotentiator in vivo.

Inhibitory effects of recombinant porcine interferon-α on porcine transmissible gastroenteritis virus infections in TGEV-seronegative piglets

Our previous research obtained purified recombinant porcine interferon-α (rPoIFN-α) containing thioredoxin (Trx) fusion tag in E. coli Rosetta (DE3). Here, we evaluate the efficacy of this rPoIFN-α to prevent piglets from the infection of the transmissible gastroenteritis virus (TGEV) attack. In this experiment, twenty-five TGEV-seronegative piglets were randomly divided into five groups. Group 1 was positive control and only challenged with TGEV; Pigs in groups 2-4 were pretreated with 2 × 10(7)IU/pig, 2 × 10(6)IU/pig, and 2 × 10(5)IU/pig rPoIFN-α before TGEV challenge. The fifth group is a negative control group. The animals of this group are pretreated only with Trx protein-containing PBS solution without TGEV challenge. After 48 h of rPoIFN-α pretreatment, the pigs in groups 1-4 were challenged by TGEV, and the pigs in group 5 were administered with PBS. The surveillance results show that Pigs pre-treated with 2 × 10 (7) IU/pig rPoIFN-α are fully aligned with the violent TGEV attack. Pigs pretreated with 2 × 10 (6) IU/pig rPoIFN-α are partially aligned with the violent TGEV attack. Though piglets pretreated with 2 × 10(6) IU/pig or 2 × 10(5)IU/pig rPoIFN-α cannot be adapted to the challenge of TGEV. However, the use of this dose of rPoIFN-α could put off the clinical signs of pigs than the positive control group of the above. These results indicate that rPoIFN-α can protect pigs from the infection of potential TGEV or delay the appearance of clinical symptoms, and its effect is dose-dependent.

Modulation of Type I Interferon System by African Swine Fever Virus

African Swine Fever Virus (ASFV) has tropism for macrophages, which seems to play a crucial role in disease pathogenesis and viral dissemination. Previous studies showed that ASFV developed mechanisms to evade type I interferon (IFN) responses. Hence, we analyzed the ability of ASFV strains of diverse virulence to modulate IFN-β and IFN-α responses. Porcine monocyte-derived macrophages un-activated (moMΦ) or activated with IFN-α (moMΦ + FN-α) were infected with virulent (22653/14) or attenuated (NH/P68) ASFV strains, and expressions of IFN-β and of 17 IFN-α subtypes genes were monitored over time. ASFV strains of diverse virulence induced different panels of IFN genes: infection of moMΦ with either strains caused statistically significant up-regulation of IFN-α3, -α7/11, whereas only attenuated NH/P68 determined statistically significant up-regulation of IFN-α10, -α12, -α13, -α15, -α17, and IFN-β. Infection of activated moMΦ with either strains resulted in up-regulation of IFN-β and many IFN-α subtypes, but statistical significance was found only for IFN-α1, -α10, -α15, -α16, -α17 in response to NH/P68-infection only. These data revealed differences in type I IFNs expression patterns, with differences between strains of diverse virulence. In addition, virulent 22653/14 ASFV seems to have developed mechanisms to suppress the induction of several type I IFN genes.

Camelid type I interferons: Identification and functional characterization of interferon alpha from the dromedary camel (Camelus dromedarius)

Investigations into the molecular immune response of dromedary camel, a key livestock species of the arid, have been limited due to the lack of species-specific reagents. Here we describe for the first time, the identification and characterization of type I IFNs of dromedary camel, which are the most important cytokines in the innate host immune response against viruses. We cloned camel IFN-α coding sequences and identified a total of eleven subtypes. The canonical IFN-α subtype designated as IFN-α1 contained a 555-bp Open Reading Frame encoding a protein of 184 amino acids. Recombinant IFN-α1 protein was produced in E. coli and purified from inclusion bodies. Recombinant camel IFN-α1 induced the mRNA expression of interferon-stimulated genes (ISGs) in camel kidney cells. The purified protein also showed potent in-vitro antiviral activity against Camelpox Virus in kidney cells. The identified camel IFN-α protein and the subtypes will facilitate a better understanding of the host immune response to viral infections in camel and the development of potential antiviral biologicals for zoonotic diseases for which camel act as a reservoir.

Molecular and functional characterization of ovis aries IFN-epsilon

Interferon-epsilon (IFN-ε) is a type I IFN playing an essential role in innate and adaptive immunity against viral infection. Ovis aries IFN-ε (OvIFN-ε), consisting of 582 bp and which encodes a protein of 193 amino acids containing a signal peptide of 21 amino acids, was cloned and characterized. OvIFN-ε shares 51.6∼ 86.5% similarity to other species of IFN-ε, and evolves from the IFN-ε branch but not the other types of IFN. Additionally, OvIFN-ε gene is well conserved during evolution, and is highly transcribed in the liver, lung, brain, skin, ovary and uterus. Recombinant protein of OvIFN-ε was expressed in Escherichia coli and purified with nickel chelated column, which exhibited broad antiviral activity in vitro, sensitivity of trypsin, and stability of pH and temperature to some extent. Furthermore, OvIFN-ε could induce the transcription of ISG15, Mx1 and OAS in a time-dependent manner, as well as inhibit the VSV and BVDV replication in Ovis aries peripheral blood lymphocyte cells and MDBK cells. This study revealed OvIFN-ε has the typical characterization of type I IFNs and exerts antiviral activity against VSV and BVDV, and induces the expression of ISGs, which not only enriches the understanding of IFN-ε, but also facilitates further research on the antiviral defense responses of Ovis aries.

Design, biological activity and signaling pathway of bovine consensus omega interferon expressed in Pichia pastoris

The bovine IFN-ω (BoIFN-ω) multigene family is located on chromosome 8, which has 14 potential functional genes and 10 pseudogenes. After aligning 14 BoIFN-ω subtypes and assigning the most frequently occurring amino acids in each position, one artificial consensus BoIFN-ω (CoBoIFN-ω) gene was designed, optimized and synthesized. Then, CoBoIFN-ω was expressed in Pichia pastoris, which was demonstrated to have 3.94-fold and 14.3-fold higher antiviral activity against VSV on MDBK cells than that of BoIFN-ω24 and BoIFN-ω3, respectively. Besides this, CoBoIFN-ω was confirmed to have antiviral activity against VSV on BL, BT, PK-15 cells, and against BEV, BHV-1, BPIV3 on MDBK cells. Additionally, CoBoIFN-ω could bind with bovine type I IFN receptors, and then activate the promoters of NF-κB, ISRE and BoIFN-β, and induce the transcription of ISGs and expression of Mx1 and NF-κB p65, which suggested CoBoIFN-ω exerts antiviral activity via activation of the JAK-STAT signaling pathway. Overall, this research on CoBoIFN-ω not only extends and improves consensus IFN research, but also reveals that CoBoIFN-ω has the potential to be used in the therapy of bovine viral diseases.

Identification and characterization of a rabbit novel IFN-α unlocated in genome

The multigene family of rabbit IFN-α (RbIFN-α) is located on chromosome 1, which shows seven functional genes in type I IFN locus. A novel RbIFN-α that remains unlocated in the rabbit genome was amplified and designated as the first novel rabbit IFN-α (RbIFN-αNov1), which possesses the typical molecular characteristics of type I IFNs and could be induced in RK-13 cells and peripheral blood mononuclear cells. After the mature peptide of RbIFN-αNov1 was expressed, its antiviral activity, physicochemical characteristics, and cytotoxicity were determined in vitro. Results indicated that RbIFN-αNov1 exerted a high specific antiviral activity against VSV and a low cytotoxic effect on RK-13 cells. RbIFN-αNov1 showed high sensitivity to trypsin and remained relatively stable after acid, alkali, or heat treatment. RbIFN-αNov1 could induce Mx1 expression on RK-13 cells and activate the NF-κB, ISRE and BoIFN-β promoter activities on bovine testicular cells. Overall, our research on RbIFN-αNov1 not only enriches the knowledge about rabbit IFNs but also makes RbIFN-αNov1 have the potential to be used as an effective therapeutic agent for rabbit viral diseases.

Interferon-omega: Current status in clinical applications

Since 1985, interferon (IFN)-ω, a type I IFN, has been identified in many animals, but not canines and mice. It has been demonstrated to have antiviral, anti-proliferation, and antitumor activities that are similar to those of IFN-α. To date, IFN-ω has been explored as a treatment option for some diseases or viral infections in humans and other animals. Studies have revealed that human IFN-ω displays antitumor activities in some models of human cancer cells and that it can be used to diagnose some diseases. While recombinant feline IFN-ω has been licensed in several countries for treating canine parvovirus, feline leukemia virus, and feline immunodeficiency virus infections, it also exhibits a certain efficacy when used to treat other viral infections or diseases. This review examines the known biological activity of IFN-ω and its clinical applications. We expect that the information provided in this review will stimulate further studies of IFN-ω as a therapeutic agent.

Molecular characterization and biological activity of bovine interferon-omega3

Bovine interferon-omega3 (BoIFN-ω3) gene was amplified from bovine liver genomic DNA, which encodes a 195-amino acid protein containing a 23-amino acid signal peptide. Analysis of the molecular characteristics revealed that BoIFN-ω3 evolving from IFN-ω, contained four cysteine residues and five alpha helices, showing that BoIFN-ω3 presented the typical molecular characteristics of type I interferon. BoIFN-ω3 exhibited antiviral and antiproliferative activities, which exerted a protective effect against VSV in several mammalian cell lines, as well as against BEV, IBRV, and BVDV in MDBK cell. Moreover, BoIFN-ω3 was shown to be highly sensitive to trypsin, but remaining stable despite changes in pH and temperature. Additionally, BoIFN-ω3 induced the transcription of Mx1, ISG15, and ISG56 genes, as well as the expression of Mx1 protein in a time-dependent manner. These findings will be useful to further study BoIFN-ω in host's defence against infectious diseases, particularly viral infections. Furthermore, results will facilitate further research on the bovine interferon family.

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BoIFN-ω3 presents antiviral activity on several mammalian cell lines and protective effect against VSV, BEV, IBRV, and BVDV.

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BoIFN-ω3 exhibits antiproliferative activity and insensitivity to pH and temperature.

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BoIFN-ω3 can activate the transcription of ISGs gene, as well as the expression of Mx1 in a time-dependent manner.

Sensitivity of African swine fever virus to type I interferon is linked to genes within multigene families 360 and 505

African swine fever virus (ASFV) causes a lethal haemorrhagic disease of pigs. There are conflicting reports on the role of interferon in ASFV infection. We therefore analysed the interaction of ASFV with porcine interferon, in vivo and in vitro. Virulent ASFV induced biologically active IFN in the circulation of pigs from day 3-post infection, whereas low virulent OUR T88/3, which lacks genes from multigene family (MGF) 360 and MGF505, did not. Infection of porcine leucocytes enriched for dendritic cells, with ASFV, in vitro, induced high levels of interferon, suggesting a potential source of interferon in animals undergoing acute ASF. Replication of OUR T88/3, but not virulent viruses, was reduced in interferon pretreated macrophages and a recombinant virus lacking similar genes to those absent in OUR T88/3 was also inhibited. These findings suggest that as well as inhibiting the induction of interferon, MGF360 and MGF505 genes also enable ASFV to overcome the antiviral state.

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Virulent strains of African swine fever virus induces interferon during infection.

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Virulent, but not attenuated strains of ASFV are resistant to the antiviral effects of interferon in porcine macrophages.

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Sensitivity to interferon is linked to genes within multigene family 360 and multigene family 530.

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Dendritic cells are a potential source of the interferon detected in vivo.

Treatment with interferon-alpha delays disease in swine infected with a highly virulent CSFV strain

Interferon-alpha (IFNα) can effectively inhibit or abort a viral infection within the host. It has been reported that IFN induction and production is hindered during classical swine fever virus (CSFV) infection. Most of those studies have been performed in vitro, making it difficult to elucidate the actual role of IFNs during CSFV infection in swine. Here, we report the effect of IFNα treatment (delivered by a replication defective recombinant human adenovirus type 5, Ad5) in swine experimentally infected with highly virulent CSFV strain Brescia. Treatment with two different subtypes of IFNα delayed the appearance of CSF-related clinical signs and virus replication although it did not prevent lethal disease. This is the first report describing the effect of IFNα treatment during CSFV infection in swine.

Expression of porcine fusion protein IRF7/3(5D) efficiently controls foot-and-mouth disease virus replication

Several studies have demonstrated that the delivery of type I, II, or III interferons (IFNs) by inoculation of a replication-defective human adenovirus 5 (Ad5) vector expressing IFNs can effectively control foot-and-mouth disease (FMD) in cattle and swine during experimental infections. However, relatively high doses are required to achieve protection. In this study, we identified the functional properties of a porcine fusion protein, poIRF7/3(5D), as a biotherapeutic and enhancer of IFN activity against FMD virus (FMDV). We showed that poIRF7/3(5D) is a potent inducer of type I IFNs, including alpha IFN (IFN-α), IFN-β, and IFN-ω but not type III IFN (interleukin-28B), without inducing cytotoxicity. Expression of poIRF7/3(5D) significantly and steadily reduced FMDV titers by up to 6 log10 units in swine and bovine cell lines. Treatment with an IFN receptor inhibitor (B18R) combined with an anti-IFN-α antibody neutralized the antiviral activity in the supernatants of cells transduced with an Ad5 vector expressing poIRF7/3(5D) [Ad5-poIRF7/3(5D)]. However, several transcripts with known antiviral function, including type I IFNs, were still highly upregulated (range of increase, 8-fold to over 500-fold) by poIRF7/3(5D) in the presence of B18R. Furthermore, the sera of mice treated with Ad5-poIRF7/3(5D) showed antiviral activity that was associated with the induction of high levels of IFN-α and resulted in complete protection against FMDV challenge at 6, 24, or 48 h posttreatment. This study highlights for the first time the antiviral potential of Ad5-poIRF7/3(5D) in vitro and in vivo against FMDV.

IMPORTANCE

FMD remains one of the most devastating diseases that affect livestock worldwide. Effective vaccine formulations are available but are serotype specific and require approximately 7 days before they are able to elicit protective immunity. We have shown that vector-delivered IFN is an option to protect animals against many FMDV serotypes as soon as 24 h and for about 4 days postadministration. Here we demonstrate that delivery of a constitutively active transcription factor that induces the production of endogenous IFNs and potentially other antiviral genes is a viable strategy to protect against FMD.

Functional characterization of canine interferon-lambda

In this study, we provide the first comprehensive annotation of canine interferon-λ (CaIFN-λ, type III IFN). Phylogenetic analysis based on genomic sequences indicated that CaIFN-λ is located in the same branch with Swine IFN-λ1 (SwIFN-λ), Bat IFN-λ1 (BaIFN-λ), and human IFN-λ1 (HuIFN-λ1). CaIFN-λ was cloned, expressed in Escherichia coli, and purified to further investigate the biological activity in vitro. The recombinant CaIFN-λ (rCaIFN-λ) displayed potent antiviral activity on both homologous and heterologous animal cells in terms of inhibiting the replication of the New Jersey serotype of vesicular stomatitis virus (VSV), canine parvovirus, and influenza virus A/WSN/33 (H1N1), respectively. In addition, we also found that rCaIFN-λ exhibits a significant antiproliferative response against A72 canine tumor cells and MDCK cells in a dose-dependent manner. Furthermore, CaIFN-λ activated the JAK-STAT signaling pathway. To evaluate the expression of CaIFN-λ induced by virus and the expression of IFN-stimulated genes (ISGs) induced by rCaIFN-λ in the MDCK cells, we measured the relative mRNA level of CaIFN-λ and ISGs (ISG15, Mx1, and 2'5'-OAS) by quantitative real-time PCR and found that the mRNA level of CaIFN-λ and the ISGs significantly increased after treating the MDCK cells with viruses and rCaIFN-λ protein, respectively. Finally, to evaluate the binding activity of rCaIFN-λ to its receptor, we expressed the extracellular domain of the canine IFN-λ receptor 1 (CaIFN-λR1-EC) and determined the binding activity via ELISA. Our results demonstrated that rCaIFN-λ bound tightly to recombinant CaIFN-λR1-EC (rCaIFN-λR1-EC).

Cloning, expression and antiviral bioactivity of red-crowned crane interferon-α

Interferon-α (IFN-α) genes have been cloned from a variety of animals, but information regarding crane IFN-α has not been reported to date. In this study, we cloned a full-length Red-crowned Crane interferon-α (crIFN-α) gene sequence consisting of a 486bp partial 5' UTR, 741bp complete ORF and 559bp partial 3' UTR. This gene encodes a protein of 246 amino acids and shares 60 to 80% identity with avian IFN-α and less than 45% identity with mammalian IFN-α. The expression of crIFN-α with an N-terminal His-tag was investigated in Escherichia coli, and the protein was purified on a nickel column. To obtain activated proteins, crIFN-α inclusion bodies were renatured by dialysis. In vitro cytopathic inhibition assays indicated that the recombinant crIFN-α could inhibit the replication of vesicular stomatitis virus in chicken fibroblasts. These antiviral activities were abrogated by rabbit anti-crIFN-α antibodies in vitro. In addition, an immunofluorescence assay indicated that crIFN-α could be expressed in chicken fibroblasts and was primarily located in the cytoplasm. Taken together, our results suggest that the crIFN-α gene may play an important role in inhibiting the replication of viruses.

Molecular and functional characterization of canine interferon-epsilon

In this study, we provide the first comprehensive annotation of the entire family of canine interferons (IFNs). Canine IFN-ε (IFNE), IFN-κ (IFNK), and IFN-λ (IFNL) were discovered for the first time. Ten functional and 2 truncated IFN-α (IFNA) pseudogenes were found in the genome, which also enriched the existing knowledge about canine IFNA. The canine type I IFN genes are clustered on chromosome 11, and their relative arrangements are illustrated. To further investigate the biological activity of canine IFNE, it was expressed and purified in Escherichia coli. Recombinant canine IFNE (rCaIFN-ε) displayed potent antiviral activity on both homologous and heterologous animal cells in vitro, indicating that rCaIFN-ε has more broad cross-species activity than recombinant canine IFNA (rCaIFN-α). The antiviral activities of rCaIFN-ε and rCaIFN-α7 against different viruses on MDCK cells were also evaluated. The antiviral activities of recombinant canine IFNK and IFNL were demonstrated using a VSV-MDCK virus-target cell system. rCaIFN-ε exhibited a significant anti-proliferative response against A72 canine tumor cells and MDCK canine epithelial cells in a dose-dependent manner. rCaIFN-α7 was approximately 16-fold more potent than rCaIFN-ε in promoting natural killer cell cytotoxicity activity. Further, rCaIFN-ε can activate the JAK-STAT signaling pathway.

Transgenically mediated shRNAs targeting conserved regions of foot-and-mouth disease virus provide heritable resistance in porcine cell lines and suckling mice

Foot-and-mouth disease virus (FMDV) is responsible for substantial economic losses in livestock breeding each year, and the development of new strategies is needed to overcome the limitations of existing vaccines and antiviral drugs. In this study, we evaluated the antiviral potential of transgenic porcine cells and suckling mice that simultaneously expressed two short-hairpin RNAs (shRNAs) targeting the conserved regions of the viral polymerase protein 3D and the non-structural protein 2B. First, two recombinant shRNA-expressing plasmids, PB-EN3D2B and PB-N3D2B, were constructed and the efficiency of the constructs for suppressing an artificial target was demonstrated in BHK-21 cells. We then integrated PB-EN3D2B into the genome of the porcine cell line IBRS-2 using the piggyBac transposon system, and stable monoclonal transgenic cell lines (MTCL) were selected. Of the 6 MTCL that were used in the antiviral assay, 3 exhibited significant resistance with suppressing ratios of more than 94% at 48 hours post-challenge (hpc) to both serotype O and serotype Asia 1 FMDV. MTCL IB-3D2B-6 displayed the strongest antiviral activity, which resulted in 100% inhibition of FMDV replication until 72 hpc. Moreover, the shRNA-expressing fragment of PB-N3D2B was integrated into the mouse genome by DNA microinjection to produce transgenic mice. When challenged with serotype O FMDV, the offspring of the transgenic mouse lines N3D2B-18 and N3D2B-81 exhibited higher survival rates of 19% to 27% relative to their non-transgenic littermates. The results suggest that these heritable shRNAs were able to suppress FMDV replication in the transgenic cell lines and suckling mice.

Pig immune response to general stimulus and to porcine reproductive and respiratory syndrome virus infection: a meta-analysis approach

BACKGROUND

The availability of gene expression data that corresponds to pig immune response challenges provides compelling material for the understanding of the host immune system. Meta-analysis offers the opportunity to confirm and expand our knowledge by combining and studying at one time a vast set of independent studies creating large datasets with increased statistical power. In this study, we performed two meta-analyses of porcine transcriptomic data: i) scrutinized the global immune response to different challenges, and ii) determined the specific response to Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) infection. To gain an in-depth knowledge of the pig response to PRRSV infection, we used an original approach comparing and eliminating the common genes from both meta-analyses in order to identify genes and pathways specifically involved in the PRRSV immune response. The software Pointillist was used to cope with the highly disparate data, circumventing the biases generated by the specific responses linked to single studies. Next, we used the Ingenuity Pathways Analysis (IPA) software to survey the canonical pathways, biological functions and transcription factors found to be significantly involved in the pig immune response. We used 779 chips corresponding to 29 datasets for the pig global immune response and 279 chips obtained from 6 datasets for the pig response to PRRSV infection, respectively.

RESULTS

The pig global immune response analysis showed interconnected canonical pathways involved in the regulation of translation and mitochondrial energy metabolism. Biological functions revealed in this meta-analysis were centred around translation regulation, which included protein synthesis, RNA-post transcriptional gene expression and cellular growth and proliferation. Furthermore, the oxidative phosphorylation and mitochondria dysfunctions, associated with stress signalling, were highly regulated. Transcription factors such as MYCN, MYC and NFE2L2 were found in this analysis to be potentially involved in the regulation of the immune response. The host specific response to PRRSV infection engendered the activation of well-defined canonical pathways in response to pathogen challenge such as TREM1, toll-like receptor and hyper-cytokinemia/ hyper-chemokinemia signalling. Furthermore, this analysis brought forth the central role of the crosstalk between innate and adaptive immune response and the regulation of anti-inflammatory response. The most significant transcription factor potentially involved in this analysis was HMGB1, which is required for the innate recognition of viral nucleic acids. Other transcription factors like interferon regulatory factors IRF1, IRF3, IRF5 and IRF8 were also involved in the pig specific response to PRRSV infection.

CONCLUSIONS

This work reveals key genes, canonical pathways and biological functions involved in the pig global immune response to diverse challenges, including PRRSV infection. The powerful statistical approach led us to consolidate previous findings as well as to gain new insights into the pig immune response either to common stimuli or specifically to PRRSV infection.

Reverse transcription real-time PCR for detection of porcine interferon α and β genes

A few studies provided convincing evidence of constitutive expression of type I interferons (IFNs) in humans and mice, and of the steady-state role of these cytokines under health conditions. These results were later confirmed in pigs, too. In line with this tenet, low levels of IFN-α/β can be detected in swine tissues in the absence of any specific inducer. These studies are compounded by the utmost complexity of type I IFNs (including among others 17 IFN-α genes in pigs), which demands proper research tools. This prompted us to analyse the available protocols and to develop a relevant, robust, reverse transcription (RT) real-time polymerase chain reaction (PCR) detection system for the amplification of porcine IFN-α/β genes. The adopted test procedure is user-friendly and provides the complete panel of gene expression of one subject in a microtitre plate. Also, a proper use of PCR fluorochromes (SYBR(®) versus EvaGreen(®) supermix) enables users to adopt proper test protocols in case of low-expression porcine IFN-α genes. This is accounted for by the much higher sensitivity of the test protocol with EvaGreen(®) supermix. Interestingly, IFN-β showed the highest frequency of constitutive expression, in agreement with its definition of 'immediate early' gene in both humans and mice. Results indicate that the outlined procedure can detect both constitutively expressed and virus-induced IFN-α/β genes, as well as the impact of environmental, non-infectious stressors on the previous profile of constitutive expression.

Interferon-λ mediates oral tolerance and inhibits antigen-specific, T-helper 2 cell-mediated inflammation in mouse intestine

BACKGROUND & AIMS

Oral tolerance is an important component of gastrointestinal homeostasis, but mechanisms of its development are not fully understood. Loss of oral tolerance occurs during food allergen-related inflammation in the gastrointestinal tract. Interferon (IFN)-λ regulates immunity, but its role in oral tolerance is not clear. We investigated the role and the mechanism of IFN-λ in the development of oral tolerance and its effect on antigen-induced, T-helper (Th)-2 cell-mediated inflammation in the intestine.

METHODS

Expression of IFN-λ and its receptor were analyzed by immunohistochemical, flow cytometric, or immunoblot analyses. Tolerogenic dendritic cells (DCs) and regulatory T cells were examined in vitro and in vivo. A mouse model of antigen-induced, Th2 cell-mediated intestinal inflammation was used to examine the role of IFN-λ and T cells in oral tolerance in the intestine.

RESULTS

CD3+ cells expressed the IFN-λ receptor, which was up-regulated following antigen-specific or nonspecific activation. Interaction between IFN-λ and its receptor induced apoptosis of T cells and their subsequent phagocytosis by DCs. This led to the generation of tolerogenic DCs and T regulatory cells in vitro and in vivo. Passive transfer of IFN-λ-primed CD3+ cells inhibited Th2 cell-mediated inflammation in the intestine.

CONCLUSIONS

IFN-λ is involved in development and maintenance of oral tolerance in the intestines of mice; it might be used to suppress antigen-specific Th2 cell-mediated inflammation in patients.

Foot-and-mouth disease virus replicates only transiently in well-differentiated porcine nasal epithelial cells

Three-dimensional (3D) porcine nasal mucosal and tracheal mucosal epithelial cell cultures were developed to analyze foot-and-mouth disease virus (FMDV) interactions with mucosal epithelial cells. The cells in these cultures differentiated and polarized until they closely resemble the epithelial layers seen in vivo. FMDV infected these cultures predominantly from the apical side, primarily by binding to integrin alphav beta6, in an Arg-Gly-Asp (RGD)-dependent manner. However, FMDV replicated only transiently without any visible cytopathic effect (CPE), and infectious progeny virus could be recovered only from the apical side. The infection induced the production of beta interferon (IFN-beta) and the IFN-inducible gene Mx1 mRNA, which coincided with the disappearance of viral RNA and progeny virus. The induction of IFN-beta mRNA correlated with the antiviral activity of the supernatants from both the apical and basolateral compartments. IFN-alpha mRNA was constitutively expressed in nasal mucosal epithelial cells in vitro and in vivo. In addition, FMDV infection induced interleukin 8 (IL-8) protein, granulocyte-macrophage colony-stimulating factor (GM-CSF), and RANTES mRNA in the infected epithelial cells, suggesting that it plays an important role in modulating the immune response.

Interferon Alpha Characterization and Its Comparative Expression in PBM Cells of Capra hircus and Antelope cervicapra Cultured in the Presence of TLR9 Agonist

TLR9 plays pivotal role in innate immune responses through upregulation of costimulatory molecules and induction of proinflammatory cytokines like type I interferons including interferon alpha (IFNA). The present study characterized IFNA cDNA and predicted protein sequences in goat and black buck. Response of the PBM cells to TLR9 agonist CpG ODN C and Phorbol Myristate Acetate (PMA) was evaluated by realtime PCR. IFNA coding sequences were amplified from leukocyte cDNA and cloned in pGEMT-easy vector for nucleotide sequencing. Sequence analysis revealed 570 bp, IFNA ORF encoding 189 amino acids in goat and black buck. Black buck and goat IFNA has 92.1% to 94.7% and 93% to 95.6% similarity at nucleotide level, 86.3% to 89.5% and 70.9% to 91.6% identity at amino acid level with other ruminants, respectively. Nonsynonymous substitutions exceeding synonymous substitutions indicated IFNA evolved through positive selection among ruminants. In spite of lower total leukocyte count, the innate immune cells like monocytes and neutrophils were more in black buck compared to goat. In addition, CpG ODN C-stimulated PBM cells revealed raised IFNA transcript in black buck than goat. These findings indicate sturdy genetically governed immune system in wild antelope black buck compared to domestic ruminant goat.

Differential expression and activity of the porcine type I interferon family

Type I interferons (IFNs) are central to innate and adaptive immunity, and many have unique developmental and physiological functions. However, in most species, only two subtypes, IFN-alpha and IFN-beta, have been well studied. Because of the increasing importance of zoonotic viral diseases and the use of pigs to address human research questions, it is important to know the complete repertoire and activity of porcine type I IFNs. Here we show that porcine type I IFNs comprise at least 39 functional genes distributed along draft genomic sequences of chromosomes 1 and 10. These functional IFN genes are classified into 17 IFN-alpha subtypes, 11 IFN-delta subtypes, 7 IFN-omega subtypes, and single-subtype subclasses of IFN-alphaomega, IFN-beta, IFN-epsilon, and IFN-kappa. We found that porcine type I IFNs have diverse expression profiles and antiviral activities against porcine reproductive and respiratory syndrome virus (PRRSV) and vesicular stomatitis virus (VSV), with activity ranging from 0 to >10(5) U.ng(-1).ml(-1). Whereas most IFN-alpha subtypes retained the greatest antiviral activity against both PRRSV and VSV in porcine and MARC-145 cells, some IFN-delta and IFN-omega subtypes, IFN-beta, and IFN-alphaomega differed in their antiviral activity based on target cells and viruses. Several IFNs, including IFN-alpha7/11, IFN-delta2/7, and IFN-omega4, exhibited minimal or no antiviral activity in the tested target cell-virus systems. Thus comparative studies showed that antiviral activity of porcine type I IFNs is virus- and cell-dependent, and IFN-alphas are positively correlated with induction of MxA, an IFN-stimulated gene. Collectively, these data provide fundamental genomic information for porcine type I IFNs, information that is necessary for understanding porcine physiological and antiviral responses.

Characterization and virus-induced expression profiles of the porcine interferon-omega multigene family

Interferon-omega is a member of the type I interferon family. In this work, 8 functional porcine interferon-omega genes and 4 pseudogenes present on porcine chromosome 1 were identified in the porcine genome database by BLAST scanning. Their genetic and genomic characteristics were investigated using bioinformatics tools. Then the PoIFN-omega functional subtype genes were isolated and expressed in BHK-21 cells. The PoIFN-omega subtypes possessed about 10(4) to 10(5) units of antiviral activity per milliliter. PoIFN-omega 7 had the highest antiviral activity, about 20 times that of PoIFN-omega 4, which had the lowest antiviral activity. Differential expression of the subtypes was detected in PK15 cells and porcine peripheral blood mononuclear cells (PBMCs) in response to pseudorabies virus and poly(I).poly(C). Expression of PoIFN-omega 2/-omega 6 was up-regulated to the greatest extent by virus infection.

Characterization of the bovine type I IFN locus: rearrangements, expansions, and novel subfamilies

BACKGROUND

The Type I interferons (IFN) have major roles in the innate immune response to viruses, a function that is believed to have led to expansion in the number and complexity of their genes, although these genes have remained confined to single chromosomal region in all mammals so far examined. IFNB and IFNE define the limits of the locus, with all other Type I IFN genes except IFNK distributed between these boundaries, strongly suggesting that the locus has broadened as IFN genes duplicated and then evolved into a series of distinct families.

RESULTS

The Type I IFN locus in Bos taurus has undergone significant rearrangement and expansion compared to mouse and human, however, with the constituent genes separated into two sub-loci separated by >700 kb. The IFNW family is greatly expanded, comprising 24 potentially functional genes and at least 8 pseudogenes. The IFNB (n = 6), represented in human and mouse by one copy, are also present as multiple copies in Bos taurus. The IFNT, which encode a non-virally inducible, ruminant-specific IFN secreted by the pre-implantation conceptus, are represented by three genes and two pseudogenes. The latter have sequences intermediate between IFNT and IFNW. A new Type I IFN family (IFNX) of four members, one of which is a pseudogene, appears to have diverged from the IFNA lineage at least 83 million years ago, but is absent in all other sequenced genomes with the possible exception of the horse, a non-ruminant herbivore.

CONCLUSION

In summary, we have provided the first comprehensive annotation of the Type I IFN locus in Bos taurus, thereby providing an insight into the functional evolution of the Type I IFN in ruminants. The diversity and global spread of the ruminant species may have required an expansion of the Type I IFN locus and its constituent genes to provide broad anti-viral protection required for foraging and foregut fermentation.

Role of Toll-like receptors in activation of porcine alveolar macrophages by porcine reproductive and respiratory syndrome virus

Control of virus replication initially depends on rapid activation of the innate immune response. Toll-like receptor (TLR) ligands are potent inducers of innate immunity against viral infections. Porcine reproductive and respiratory syndrome virus (PRRSV), a positive-sense RNA virus, initiates infection in porcine alveolar macrophages (PAMs), elicits weak immune responses, and establishes a persistent infection. To understand the role of single-stranded RNA and double-stranded RNA (dsRNA) intermediates in eliciting host immunity, we sought to determine if TLRs, particularly those that respond to viral molecular patterns, are involved in PRRSV infection. Activation of TLR3 in PAMs with dsRNA increased gene expression for alpha interferon and suppressed PRRSV infectivity. In contrast, TLR4 activation by the treatment of PAMs with lipopolysaccharide did not influence PRRSV infectivity.

Detection of Differential Expression of Porcine IFN-αSubtypes by Reverse Transcription Polymerase Chain Reaction

The porcine interferon-alpha (IFN-alpha) multigene family is a new IFN-alpha system in recent research. Characterization of the PoIFN-alpha multigene family has been described in our previous work, and 14 functional PoIFN-alpha genes were detected in the porcine genome. In this study, we designed subtype-specific primers and consensus primers for PoIFN-alpha. The expression of PoIFN-alpha was detected using the two PCR strategies in three systems, namely, poly(I).poly(C)-DEAE-dextran-induced PK15 cells, pseudorabies virus-infected PK15 cells, and infected PK15 cells with an attenuated strain of swine fever virus, respectively. In poly(I).poly(C)-DEAE-dextran-induced PK15 cells, the expression of IFN-alpha2, -alpha3, -alpha4, -alpha8, and -alpha9 after 6-h/24-h inducement in PK15 cells were observed. In pseudorabies virus-infected PK15 cells, the expression of PoIFN-alpha2, -alpha3, -alpha8, -alpha9, -alpha10, and -alpha13 was observed after 6-h/24-h infection, and in the attenuated strain of swine fever virus-infected PK15 cells, upregulation of PoIFN-alpha2, -alpha3, -alpha4, -alpha8, -alpha9, and -alpha10 was detected. The results of realtime quantitative PCR analysis suggested that the expression was time-dependent in pseudorabies virus/poly(I).poly(C)-DEAE-dextran-induced PK15 cells, but in the attenuated swine fever virus-infected PK15 system, the expression level of IFN-alpha subtypes was not obviously time dependent.

Alpha interferon is a powerful adjuvant for a recombinant protein vaccine against foot-and-mouth disease virus in swine, and an effective stimulus of in vivo immune response

The adjuvant effect of porcine interferon-alpha (PoIFN-alpha) was examined in swine vaccinated with a recombinant FMD protein vaccine named IgG-FMDV, which contains the swine IgG single heavy chain constant region and an immunogenic peptide of serotype O FMDV. The PoIFN-alpha gene was cloned into pcDNA3 vector and the recombinant plasmid was incorporated into cationic liposomes by a dehydration and rehydration procedure to use as an adjuvant, injected together with low-dose IgG-FMDV. This procedure resulted in strong induction of FMDV-specific neutralizing antibody and significant T-cell-mediated immune responses, whereas only a modest humoral and cellular response was observed with low-dose vaccine alone. As an adjuvant for the protein vaccine, PoIFN-alpha induced strong inflammatory cytokines production in vivo and the results denoted that IFN-adjuvant and our vaccines could drive the immune response toward Th1 type responses. The data of ELISA suggests that the recombinant protein vaccine synergizes with the IFN-adjuvant to produce endogenous IFN in vivo. In response to viral challenge, all control animals developed viremia and lesions, whereas all animals received IFN-adjuvant+IgG-FMDV were protected and nonstructural protein antibody in this group could not be detected by 14 days post-challenge (dpc). Our studies indicate that porcine IFN-alpha is a powerful adjuvant for recombinant FMD protein vaccine and could aid in vaccination against FMDV in swine.

Advances in swine transcriptomics

The past five years have seen a tremendous rise in porcine transcriptomic data. Available porcine Expressed Sequence Tags (ESTs) have expanded greatly, with over 623,000 ESTs deposited in Genbank. ESTs have been used to expand the pig-human comparative maps, but such data has also been used in many ways to understand pig gene expression. Several methods have been used to identify genes differentially expressed (DE) in specific tissues or cell types under different treatments. These include open screening methods such as suppression subtractive hybridization, differential display, serial analysis of gene expression, and EST sequence frequency, as well as closed methods that measure expression of a defined set of sequences such as hybridization to membrane arrays and microarrays. The use of microarrays to begin large-scale transcriptome analysis has been recently reported, using either specialized or broad-coverage arrays. This review covers published results using the above techniques in the pig, as well as unpublished data provided by the research community, and reports on unpublished Affymetrix data from our group. Published and unpublished bioinformatics efforts are discussed, including recent work by our group to integrate two broad-coverage microarray platforms. We conclude by predicting experiments that will become possible with new anticipated tools and data, including the porcine genome sequence. We emphasize that the need for bioinformatics infrastructure to efficiently store and analyze the expanding amounts of gene expression data is critical, and that this deficit has emerged as a limiting factor for acceleration of genomic understanding in the pig.