Upregulation of interleukin-4 and IFN-gamma expression by IFN-tau, a member of the type I IFN family

Unrevealing functional candidate genes for bovine fertility through RNA sequencing meta-analysis and regulatory elements networks of co-expressed genes and lncRNAs

The high genetic heterogeneity and environmental effects of subfertility in livestock species make the elucidation of the genetic mechanisms associated with reproductive efficiency a difficult task. Network and co-expression network meta-analyses were applied alongside genetic variant calling and long non-coding RNA (lncRNA) characterization to identify functionally relevant target genes and regulatory subnetworks associated with fertility in dairy cattle. In total, 505 lncRNAs (441 previously annotated in the bovine reference genome ARS-UCD 1.2 and 64 novel lncRNAs) were identified. Seven differentially expressed genes between high-fertile (HF) and sub-fertile (SF) Holstein cows were identified in the network meta-analysis (CA5A, ENSBTAG00000051149, ENSBTAG00000003272, DEFB7, DIO2, TRPV3, and COL4A4). Additionally, seven functional candidate differentially co-expressed (DcoExp) modules with a differential regulatory pattern (|z-score|>2) were identified between HF and SF cows. The functional candidate genes and DcoExp modules identified were associated with fertility relevant processes such as the regulation of embryonic implantation and proliferation, interaction and molecule transfer between the fetus and the cow, and the immune system. These results help to better understand the genetic mechanisms associated with reproductive efficiency in dairy cattle through the identification of potential biomarkers and genetic variants associated with differentially expressed regulatory gene and lncRNAs regulatory element networks.

IFN-τ mediated miR-26a targeting PTEN to activate PI3K/AKT signalling to alleviate the inflammatory damage of bEECs

Endometritis is the failure of embryo implantation and an important cause of infertility in dairy cows. IFN-τ is a type I interferon unique to ruminants. In regulating the process of inflammatory response, IFN-τ can be expressed through MicroRNAs (miRNAs) to regulate the process of inflammation. However, IFN-τ regulates lipopolysaccharide (LPS)-induced inflammatory injury of bEECs through the highly conserved miR-26a in mammals, and the mechanism remains unclear. Bovine endometrial epithelial cells (bEECs)were isolated and cultured to establish an inflammatory injury model. RT–qPCR and ELISA were used to detect the secretion of inflammatory factors. Dual-luciferase assays and target gene silencing assays determine the regulatory role of miRNAs. The target protein was detected by immunofluorescence and western blotting. This study showed that the expression of miR-26a was significantly down-regulated in mouse endometrium inflammatory injury tissue and LPS stimulated bEECs; and IFN-τ reversed the expression of miR-26a. The study also showed that the overexpression of miR-26a significantly inhibited the secretion of pro-inflammatory cytokines IL-1β, IL-6 and TNF-α. In addition, studies have shown that miR-26a inhibits its translation by targeting PTEN 3′-UTR, which in turn activates the Phosphatidylinositide 3-kinases/protein kinase B (PI3K/AKT) pathway, so that nuclear factor kappa-B (NF-κB) signaling is inhibited. In summary, the results of this study further confirm that IFN-τ as an anti-inflammatory agent can up-regulate the expression of miR-26a and target the PTEN gene to inhibit the inflammatory damage of bEECs.

Implantation associated changes in expression profile of indoleamine-2, 3-dioxygenase 1, Th1-Th2 cytokines and interferon-stimulated genes on neutrophils and peripheral blood mononuclear cells of crossbred cows

Effective bidirectional communication between the embryo and dam improves the reproductive efficiency of dairy cows. Possible role of immunosuppressive indolamine-2, 3-dioxygenase 1 (IDO1) enzyme in the regulation of maternal systemic cytokine balance/shift during early pregnancy establishment along with various interferon-stimulated genes (ISGs) expression in neutrophils and peripheral blood mononuclear cell (PBMCs) were investigated in crossbred cows. Blood was collected on days 0 i.e. day of Artificial Insemination (AI), 10, 18 and 36 post-AI followed by isolation of neutrophils and PBMCs for gene expression study of IDO1, anti-inflammatory cytokines (IL-4, IL-10 and TGFβ1), pro-inflammatory cytokines (IFNγ and TNFα) and ISGs (ISG15, MX1, MX2, OAS1) in pregnant and non-pregnant cows. Cows were grouped as pregnant and non-pregnant after pregnancy confirmation by non-return to heat, ultrasonography, per rectal examination along with progesterone and IFNτ assay. Significantly (P < 0.05) higher relative mRNA expression of IDO1 and anti-inflammatory cytokines on days 10 and 18 post-AI were observed in both neutrophils and PBMCs of pregnant cows. Pregnant cows showed significantly (P < 0.05) higher mRNA transcripts of IFNγ and TNFα genes on days 18 post-AI in both neutrophils and PBMCs. Expression of ISGs was higher (P < 0.05) on day 10^th and 18^th post AI in both the neutrophils and PBMCs of pregnant cows. The study indicates that systemic immune regulation by IDO1 (through cytokine shift) and ISGs in peripheral immune cells are essential for the establishment of pregnancy and may be targeted in future as biomarkers for pregnancy diagnosis.

Modulation of Helper T Cytokines in Thymus during Early Pregnancy in Ewes

Simple Summary

The thymus is a main organ of the immune system. Immune tolerance exists in maternal immune system during pregnancy. Helper T (Th)1 and Th2 cytokines regulate the functions of immune system. We found that early pregnancy affected the production of Th1 and Th2 cytokines in maternal thymus in sheep, which may be beneficial for normal pregnancy.

Abstract

There is an immune tolerance in maternal immune system during pregnancy, and thymus is a main organ of the immune system. Helper T (Th)1 and Th2 cytokines are involved in the regulation of immune system, but the modulation of Th cytokines in the thymus during early pregnancy is unclear in ewes. Thymuses were collected on day 16 of the estrous cycle, and on days 13, 16, and 25 of pregnancy in ewes. qRT-PCR, Western blot, and immunohistochemistry were used to analyze the expression of Th1 and Th2 cytokines in the thymuses. There was a peak in the expression of interferon-gamma (IFN-γ) on day 16 of pregnancy, an upregulation of tumor necrosis factor beta (TNF-β), and a sustained expression of interleukin-2 (IL-2) and IL-4. Furthermore, there was a peak in the expression of IL-6 on day 13 of pregnancy, no expression of IL-6 on day 16 of the estrous cycle and day 25 of pregnancy, and an upregulation of IL-5 and IL-10 in the thymuses during early pregnancy. The immunohistochemistry results revealed that the IFN-γ and IL-6 proteins were limited to the stromal cells, capillaries, and thymic corpuscles. In conclusion, early pregnancy influenced the production of Th1 and Th2 cytokines of maternal thymus in sheep.

Comparison of Th1 and Th2 cytokines production in ovine lymph nodes during early pregnancy

As a fetal allograft to the mother, early conceptus regulates the intrauterine immune and systemic immune responses during early pregnancy in sheep. However, expression of T helper 1 (Th1) and Th2 cytokines in maternal lymph nodes is unclear during early pregnancy in sheep. In this study, inguinal lymph nodes were obtained on day 16 of the estrous cycle and on days 13, 16 and 25 of pregnancy (n = 4 for each group) in ewes, and qRT-PCR, western blot and immunohistochemistry were used to compare the expression of Th1 and Th2 cytokines in the lymph nodes. Our results showed that there were the highest levels of Th1 cytokines (IFN-γ, TNF-β and IL-2) and Th2 cytokines (IL-4, IL-5, IL-6 and IL-10) in the lymph nodes on day 13 or 16 of pregnancy. Furthermore, there were a downregulation of TNF-β and IL-2 and an upregulation of IL-5 and IL-10 on day 25 of pregnancy compared with that in nonpregnancy, with no significant difference in the expression of IFN-γ, IL-4, and IL-6 between the ewes on day 25 of pregnancy and nonpregnancy. The immunohistochemistry results showed that the IL-2 and IL-10 proteins were limited to the subcapsular sinus and trabeculae in the cortex, lymph sinus. In conclusion, early pregnancy exerted its effects on the lymph node and induced a Th2-biased response, which was essential for a normal pregnancy in sheep.

Differential expression of interferon-gamma, IL-4 and IL-10 in peripheral blood mononuclear cells during early pregnancy of the bovine

Maternal systemic immune response is regulated by conceptus-derived signals through peripheral blood mononuclear cells (PBMCs) via blood circulation during early pregnancy in cattle. In this study, the PBMCs from day 18 in non-pregnant cows and days 14, 18 and 30 in pregnant cows were used to explore the expression of interferon-gamma (IFN-γ), interleukin 4 (IL-4) and IL-10, and the plasma progesterone (P4) concentration was also determined. The results showed that the expression levels of mRNA and the protein of IFN-γ were lower and that IL-4 and IL-10 were higher in the PBMCs from the pregnant cows than in those of non-pregnant cows. From this study, early pregnancy induced a lower Th1 immunity (IFN-γ) and a higher Th2 immunity (IL-4 and IL-10) in the PBMCs, which may be related to interferon-tau and P4, thereby contributing to successful pregnancy in cattle.

Pregnancy-Induced ISG-15 and MX-1 Gene Expression is Detected in the Liver of Holstein-Friesian Heifers During Late Peri-Implantation Period

The bovine embryonic signal interferon-τ (IFN-τ) produced by the trophoblast is known to pass through the uterine fluid towards the endometrium and further into the maternal blood, where IFN-τ induces specific expression of interferon-stimulated gene expression (ISG), for example in peripheral leucocytes. In sheep, it was shown experimentally by administration of IFN-τ that ISG is also detectable in the liver. The objective was to test whether ISG can be detected in liver biopsy specimens from Holstein-Friesian heifers during early pregnancy. Liver biopsies were taken on day 18 from pregnant and non-pregnant heifers (n = 19), and the interferon-stimulated protein 15 kDa (ISG-15) and myxovirus-resistance protein-1 (MX-1) gene expression was detected. The expression of both MX-1 (p: 24.33 ± 7.40 vs np: 9.00 ± 4.02) and ISG-15 (p: 43.73 ± 23.22 vs 7.83 ± 3.63) was higher in pregnant compared to non-pregnant heifers (p < 0.05). In conclusion, pregnancy induced ISG-15 and MX-1 gene expression in the liver already at day 18 in cattle.

Interferon-tau: current applications and potential in antiviral therapy

Interferon-tau (IFN-tau) was initially identified as an ovine pregnancy protein. Produced by the trophoblast, it is important in preventing degradation of the corpus luteum and has been used as an early marker for ovine pregnancy. As a member of the family of type I interferons, IFN-tau has demonstrated promising antiviral activity against human viral infections in vitro. Additionally, it displays high species cross-reactivity despite its absence in humans. To date, IFN-tau has shown efficacy in reducing replication of human immunodeficiency virus, feline immunodeficiency virus, and human papillomavirus. While IFN-tau shares similar antiviral activity to IFN-alpha, the current interferon of choice for treatment of viral infections, it lacks the associated toxicity. This may make IFN-tau an attractive alternative to IFN-alpha for the treatment of viral infections.

In vitro and in vivo effects of recombinant bovine interferon-tau on bovine leukemia virus

The antiviral effects of recombinant bovine interferon-tau (rboIFN-tau) on bovine leukemia virus (BLV) were examined in vitro and in vivo. In the in vitro experiments, BLV titers decreased in FLK-BLV cells and in peripheral blood mononuclear cells of BLV-infected cattle treated with rboIFN-tau at a concentration higher than 10(2) U/ml. In order to examine the in vivo effects of rboIFN-tau, 10 BLV-infected cattle were subcutaneously injected with rboIFN-tau. In the first experiment, 6 cows were administrated with 10(5) U/kg body weight of rboIFN-tau 3 times per week for 4 weeks, while in the second experiment 4 cows were administrated with 10(6) U/kg body weight of rboIFN-tau 3 times per week for 3 weeks. No adverse effects were observed after the administration of rboIFN-tau. In experiment No. 1, the mean BLV titers in cattle decreased in the post-rboIFN-tau administration period compared to the pre-rboIFN-tau administration period. In experiment No. 2, the mean BLV titers in cattle decreased in the rboIFN-tau administration period. These results suggest that rboIFN-tau decreases BLV titers in vitro and in vivo and that rboIFN-tau possibly reduces the degree of BLV titer in cattle without severe side effects.

Trophoblast cells of ruminant placentas—A minireview

The ruminant placenta is classified as cotyledonary and synepitheliochorial on the basis of its gross anatomical features and histological characteristics, respectively. The richly vascularized embryonic chorioallantois is lined on its external surface by cells of the trophectodermal epithelium. These cells which assume specialized functions are referred to as trophoblast cells. Two morphologically and functionally distinct cell types have been recognized in the trophectoderm of the placenta of ruminant animals. These are the mononucleate trophoblast cells and the binucleate trophoblast cells. The occurrence, morphological characteristics, and specialized functions of these trophoblast cells, in relation to conceptus nutrition and survival in utero are discussed in this review.

Regulation of conceptus adhesion by endometrial CXC chemokines during the implantation period in sheep

To gain a better understanding of biochemical mechanisms of conceptus adhesion to the maternal endometrium in ruminant ungulates, the present study was performed to clarify roles of chemokines and extracellular matrix (ECM) components in the regulation of ovine blastocyst attachment to the endometrium. In addition to the chemokine, interferon-gamma inducible protein 10 kDa (IP-10, CXCL10), the chemokine receptor, CXCR3, also recognizes two other chemokines; monokine induced by IFN-gamma (MIG, CXCL9) and IFN-inducible T cell alpha chemoattractant (I-TAC, CXCL11). Similar to CXCL10, CXCL9, and CXCL11 were expressed in the uterus during the peri-implantation period, and CXCL9 mRNA expression was stimulated in endometrial explants from day 14 cyclic ewes by the addition of IFN-tau or IFN-gamma. Without ECM components, conceptus cell adhesion was low on day 14 of gestation and exhibited a 2.5-fold increase on day 17; adhesiveness on day 20 was 1/10 of that on day 14. Among various ECM components examined, trophoblast adhesion was greatest when fibronectin was used. Although day 14 conceptuses did not show much adhesive activity to fibronectin, day 17 trophoblast, and day 20 chorionic membrane exhibited 2.3-fold and 50-fold increase, respectively, which was enhanced by treatment with CXCL9 or CXCL10. These results indicate that through endometrial fibronectin and chemokines, ovine conceptus cells gain the ability to attach to the endometrium during pre-implantation period; however, elucidation of molecular mechanisms by which the conceptus acquires the adhesive ability during this time period awaits further investigation.

Involvement of IL-6 in the anti-human immunodeficiency virus activity of IFN-tau in human macrophages

IFN-tau is a non-cytotoxic type I IFN responsible for maternal recognition of the foetus in ruminants. IFN-tau has been found to inhibit HIV replication more strongly than human IFN-alpha, particularly in human monocyte-derived macrophages, without associated toxicity. Ovine IFN-tau uses the same anti-viral cellular pathways as human IFN-alpha in human macrophages, principally inhibiting the early steps of the biological cycle of HIV, preventing the integration of HIV DNA into the host-cell genome. In this study, we investigated the immunomodulatory properties of IFN-tau in human macrophages. We found that IFN-tau increased the production of IL-10 and IL-6, but not of IL-1beta or tumour necrosis factor alpha, in unstimulated, LPS-stimulated and HIV-1/Ba-L-infected macrophages. We also found that treatment with IL-6 inhibited HIV replication. Moreover, the neutralization of IL-6 activity in the cell culture supernatants of IFN-tau-treated macrophages led to a decrease in the anti-retroviral effects of IFN-tau, suggesting that IL-6 was involved in the anti-viral activity induced by IFN-tau. By focusing on the very early steps of the biological cycle of HIV, we showed that IL-6 co-operated with IFN-tau to decrease intracellular HIV RNA levels 2 h after infection.

Changes in Immune Cell Distribution and IL-10 Production are Regulated through Endometrial IP-10 Expression in the Goat Uterus

PROBLEM

Changes in distribution or redistribution of immune cells are required for the establishment and maintenance of pregnancy, but these changes during early pregnancy have been poorly understood in the ruminant ungulates. Expression of a chemokine, interferon-gamma (IFN-gamma)-inducible protein 10 kDa (IP-10, CXCL10), was identified in the endometrium of pregnant goats. Population and/or distribution of endometrial immune cells and their cytokine productions could be regulated by IP-10 during the period of pregnancy establishment.

METHOD OF STUDY

Using reverse transcriptase-polymerase chain reaction (RT-PCR), expression of IP-10, IFN-gamma, tumor necrosis factor-alpha, interleukin-10 (IL-10), CXCR3 mRNA and leukocyte cell surface markers, CD4, CD8, CD11b and CD45 mRNA during the caprine early pregnancy was investigated. The ability of IP-10 to stimulate peripheral blood mononuclear cells (PBMCs) migration was demonstrated using a chemotaxis assay. Changes in migration of PBMCs' immune cell population and cytokine expressions with IP-10 stimulation were investigated using flow cytometry and RT-PCR respectively.

RESULTS

Levels of IP-10, IL-10, CD4 and CD11b mRNA, and the number of CD4 and CD11b positive cells in pregnant goat endometrium were higher than those of cyclic goat endometrium. Migration of PBMCs was stimulated by recombinant caprine IP-10, and the effect was significantly reduced by neutralization with the use of an anti-IP-10 antibody. In the flow cytometric and RT-PCR analyses, migrated cells stimulated by IP-10 increased the expression of IL-10 and CD11b mRNA. Furthermore, IP-10 could stimulate the expression of IL-10 mRNA from PBMCs.

CONCLUSION

Endometrial chemokine IP-10 could regulate IL-10 production by resident and possibly migrated cells expressing CD11b, probably natural killer cells, and these changes may result in immune environments of the uterus suitable for conceptus implantation in ruminants.

Characterization of gelatinases in bronchoalveolar lavage fluid and gelatinases produced by alveolar macrophages isolated from healthy calves

OBJECTIVE

To characterize gelatinases in bronchoalveolar lavage fluid (BALF) and gelatinases produced by alveolar macrophages of healthy calves.

SAMPLE POPULATION

Samples of BALF and alveolar macrophages obtained from 20 healthy 2-month-old calves.

PROCEDURE

BALF was examined by use of gelatin zymography and immunoblotting to detect gelatinases and tissue inhibitor of metalloproteinase (TIMP)-1 and -2. Cultured alveolar macrophages were stimulated with lipopolysaccharide (LPS), and conditioned medium was subjected to zymography. Alveolar macrophage RNA was used for reverse transcriptase-polymerase chain reaction assay of matrix metalloproteinases (MMPs), cyclooxygenase-2, and inducible nitric oxide synthase.

RESULTS

Gelatinolytic activity in BALF was evident at 92 kd (14/20 calves; latent MMP-9) and 72 kd (18/20; latent MMP-2). Gelatinolytic activity was evident at 82 kd (10/20 calves; active MMP-9) and 62 kd (17/20; active MMP-2). Gelatinases were inhibited by metal chelators but not serine protease inhibitors. Immunoblotting of BALF protein and conditioned medium confirmed the MMP-2 and -9 proteins. Endogenous inhibitors (ie, TIMPs) were detected in BALF from all calves (TIMP-1) or BALF from only 4 calves (TIMP-2). Cultured alveolar macrophages expressed detectable amounts of MMP-9 mRNA but not MMP-2 mRNA.

CONCLUSIONS AND CLINICAL RELEVANCE

Healthy calves have detectable amounts of the gelatinases MMP-2 and -9 in BALF Endogenous inhibitors of MMPs were detected in BALF (ie, TIMP-1, all calves; TIMP-2, 4 calves). Lipopolysaccharide-stimulated alveolar macrophages express MMP-9 but not MMP-2 mRNA. The role of proteases in the pathogenesis of lung injury associated with pneumonia has yet to be determined.

Expression of Cyclooxygenase-2 and Granulocyte-Macrophage Colony-Stimulating Factor in the Endometrial Epithelium of the Cow Is Up-Regulated During Early Pregnancy and in Response to Intrauterine Infusions of Interferon-τ1

On the basis of results obtained in vitro, we previously proposed a model in which signals from the conceptus, namely interferon-tau (IFN-tau) and prostaglandin E2, increase the expression of cyclooxygenase (COX)-2 or granulocyte-macrophage colony-stimulating factor (GM-CSF) in immune and nonimmune cells of the bovine endometrium. Two experiments were conducted to verify the validity of this hypothesis in vivo. In experiment 1, the in vivo expression of COX-2 and GM-CSF during early pregnancy was monitored. Uteri from heifers were collected at different days (d) of the estrous cycle and pregnancy (P). In experiment 2, the effects of intrauterine infusions of IFN-tau on the expression of COX-2 and GM-CSF were analyzed. Immunohistochemistry was performed on uterine sections, and image analysis was used to evaluate the staining intensity in the conceptus, the luminal epithelium (LE), and the subepithelial stroma. In experiment 1, staining for COX-2 was maximal between d18P and d24P, both in the LE and in the conceptus, whereas staining for GM-CSF reached a plateau between d18P and d30P in the LE. In experiment 2, in response to IFN-tau, COX-2 was up-regulated in the LE of the ipsilateral horn, whereas GM-CSF was enhanced in both uterine horns. The current report supports the view that the conceptus, through its secretion of IFN-tau, stimulates maternal epithelial expression of COX-2 and GM-CSF during the peri-attachment period in the cow.

Interferon-tau blocks the stimulatory effect of tumor necrosis factor-alpha on prostaglandin F2alpha synthesis by bovine endometrial stromal cells

Tumor necrosis factor-alpha (TNFalpha) has been shown to be a potent stimulator of prostaglandin (PG) F2alpha synthesis in bovine endometrial stromal cells. The aims of the present study were to determine the effect of interferon-tau (IFNtau) on TNFalpha-stimulated PGF2alpha synthesis and the intracellular mechanisms of TNFalpha and IFNtau action in the stromal cells. When cultured bovine stromal cells were exposed to TNFalpha (0.006-0.6 nM) for 24 h, the production of PGF2alpha and cyclooxygenase (COX)-2 gene expression were stimulated by TNFalpha (0.06-0.6 nM, P < 0.05). Moreover, a specific COX-2 inhibitor (NS-398; 5 nM) blocked the stimulatory effect of TNFalpha on PGF2alpha production (P < 0.05). Although IFNtau (0.03-30 ng/ml) did not stimulate basal PGF2alpha production in the stromal cells, it suppressed TNFalpha action in PGF2alpha production dose dependently (P < 0.05). Moreover, the stimulatory effect of TNFalpha (0.6 nM) on COX-2 gene expression was completely blocked by IFNtau (30 ng/ml; P < 0.05), although the gene expression of COX-2 was not influenced by IFNtau. The overall results indicate that the stimulatory effect of TNFalpha on PGF2alpha production is mediated by the up-regulation of COX-2 gene expression and suggest that one of the mechanisms of the inhibitory effect of IFNtau on luteolysis is the inhibition of TNFalpha action in PGF2alpha production in the stromal cells by the down-regulation of COX-2 gene expression stimulated by TNFalpha.

Type 1 and type 2 responses in regulation of Ig isotype expression in cattle

Regulation of humoral immune responses is multifactorial involving appropriate activation, costimulation and the presence of specific soluble factors. Polarized type 1 or type 2 humoral responses in the laboratory mouse have been linked to expression of specific cytokines and thus can be used to provide insight into the type of response generated by infection. For example, IFN-gamma has been linked to IgG2a and IgG3 production, IL-4 to IgG1 and IgE production and TGF-beta to IgA production. Unlike the laboratory mouse, generally housed under defined conditions, highly skewed isotype expression patterns generally occur in cattle in chronic infections. A few examples of polarized responses have been noted in chronic experimental or naturally occurring infections including F. hepatica, M. paratuberculosis, C. parvum and B. abortus. In vitro studies using purified bovine B cells and various forms of costimulation and cytokines have demonstrated that isotype responses can be polarized under certain experimental conditions in vitro. That is, IgG1 expression is positively regulated by IL-4 and IgG2 expression is positively regulated by IFN-gamma. Other as yet unidentified factors may play pivotal roles in regulating humoral immune responses in large ruminant species in vivo. This possibility is best exemplified by recent studies using DNA vaccines in cattle that have been demonstrated in the mouse to be generally polarizing to a type 1 response. Surprisingly, studies in cattle using plasmid DNA as vaccination material show an almost exclusive IgG1 response. Based on a number of studies using T cell clones and various biological assays, it is clear that the classical roles of many cytokines in the laboratory mouse do not extrapolate entirely or at all to cattle. Thus, the design of adjuvants and immune modulators should be based on studies done in cattle or using bovine cells. Based on studies to date, several "holes" in the cytokine repertoire exist and these roles may be assumed by unique factors or activities of other known cytokines.

Phenotypic and ultrastructural characteristics of bronchoalveolar lavage cells of lentivirus-infected lambs treated with recombinant ovine IFN-tau

Ovine lentivirus (OvLV) belongs to the family Retroviridae and closely resembles the human immunodeficiency virus (HIV). Pulmonary lesions in OvLV-infected sheep consist of lymphoid interstitial pneumonia (LIP) and lymphocytic alveolitis. Similar pulmonary lesions occur in up to 40% of HIV-infected children and in some adults with AIDS. Interferon-tau (IFN-tau), a type I IFN, is produced by trophectoderm of ruminant conceptuses and is the pregnancy recognition signal in these species. To evaluate changes in phenotypes of bronchoalveolar lavage (BAL) cells of OvLV-infected lambs treated with recombinant ovine IFN-tau (rOvIFN-tau), 24 lambs were randomly allocated to one of four groups (n = 6 per group): 1, no virus + placebo (NVP); 2, no virus + rOvIFN-tau (NVI); 3, virus + placebo (VP); 4, virus + rOvIFN-tau (VI). The BAL cells from 3 lambs in each group were labeled with monoclonal antibodies (mAb) to cell surface markers at 16 weeks of treatment, and cells from the remaining 3 lambs in each group were labeled with mAb at 34 weeks of treatment. After labeling, BAL cells were analyzed by flow cytometry. The morphology of BAL cells from all experimental lambs was examined by transmission electron microscopy (TEM). At week 16, no differences in the relative proportions of BAL cell phenotypes were detected among the experimental groups. At week 34, VI lambs had higher proportions of CD8(+), gammadelta(+), MHC class II(+), and L-selectin (LS(+)) BAL cells compared with VP lambs. Higher proportions of CD14(+) and CD44(+) cells were found in VP lambs compared with NVP lambs at 34 weeks. OvLV-like particles were detected only in bronchoalveolar macrophages of VP lambs. In this study, rOvIFN-tau increased the proportions of primary antiviral gammadelta(+) and CD8(+) immune cells in OvLV-infected lambs. This may represent a cellular mechanism to explain the antiviral and therapeutic efficacy of this cytokine, in addition to its direct antiviral effect. However, because the actual number of cells labeled with mAb CD8 was low and some subsets of gammadelta cells may coexpress the CD8 marker, further studies are necessary to better define the role of rOvIFN-tau in the modulation of these cells in vivo.

Babesia bovis-stimulated macrophages express interleukin-1beta, interleukin-12, tumor necrosis factor alpha, and nitric oxide and inhibit parasite replication in vitro

The tick-transmitted hemoparasite Babesia bovis causes an acute infection that results in persistence and immunity against challenge infection in cattle that control the initial parasitemia. Resolution of acute infection with this protozoal pathogen is believed to be dependent on products of activated macrophages (Mphi), including inflammatory cytokines and nitric oxide (NO) and its derivatives. B. bovis stimulates inducible nitric oxide synthase (iNOS) and production of NO in bovine Mphi, and chemical donors of NO inhibit the growth of B. bovis in vitro. However, the induction of inflammatory cytokines in Mphi by babesial parasites has not been described, and the antiparasitic activity of NO produced by B. bovis-stimulated Mphi has not been definitively demonstrated. We report that monocyte-derived Mphi activated by B. bovis expressed enhanced levels of inflammatory cytokines interleukin-1beta (IL-1beta), IL-12, and tumor necrosis factor alpha that are important for stimulating innate and acquired immunity against protozoal pathogens. Furthermore, a lipid fraction of B. bovis-infected erythrocytes stimulated iNOS expression and NO production by Mphi. Cocultures of Mphi and B. bovis-infected erythrocytes either in contact or physically separated resulted in reduced parasite viability. However, NO produced by bovine Mphi in response to B. bovis-infected erythrocytes was only partially responsible for parasite growth inhibition, suggesting that additional factors contribute to the inhibition of B. bovis replication. These findings demonstrate that B. bovis induces an innate immune response that is capable of controlling parasite replication and that could potentially result in host survival and parasite persistence.

Production, purification, and carboxy-terminal sequencing of bioactive recombinant bovine interferon-stimulated gene product 17

An interferon (IFN)-stimulated gene (ISG) encodes a bovine 17-kDa protein (bISG17) that is released from endometrial cells but also conjugates to intracellular proteins through a ubiquitinlike mechanism. During early pregnancy in ruminants, conceptus-derived IFN-tau induces endometrial ISG17. The present experiments were designed to generate bioactive recombinant (r) bISG17. The Pichia pastoris yeast expression system was used because previous experiments expressing the human ISG15 ortholog in bacteria were confounded by inherent carboxypeptidase activity that cleaved C-terminal residues resulting in an inactive protein. In a series of extensive yeast culture experiments using shaker-bath and fermentation approaches, optimal conditions were determined for a transformant containing a multi-ISG17 gene insertion. Recombinant bISG17 was purified. Carboxy-terminal sequencing revealed that rbISG17 retained the C-terminal Gly that is potentially critical for the first step in covalent attachment to targeted intracellular proteins. The rISG17 induced (P < 0.0001) IFN-gamma mRNA (reverse transcription-polymerase chain reaction) and release of IFN-gamma protein (ELISA) by bovine peripheral blood mononuclear cells. The IFN-gamma mRNA also was upregulated (P < 0.0001) in endometrium from pregnant (Day 18) when compared with nonpregnant (Days 14 and 18) cows. It is concluded that rbISG17 generated in a yeast expression system retains cytokine/hormonal activity. This is the first description coupling the biology of two distinct IFNs (gamma and tau) through the intermediary ubiquitin homolog ISG17.

Interleukin-12 as an adjuvant promotes immunoglobulin G and type 1 cytokine recall responses to major surface protein 2 of the ehrlichial pathogen Anaplasma marginale

Anaplasma marginale is a tick-transmitted pathogen of cattle closely related to the human ehrlichiae, Ehrlichia chaffeensis and the agent of human granulocytic ehrlichiosis (HGE). These pathogens have in common a structurally conserved outer membrane protein (OMP) designated the major surface protein 2 (MSP-2) in A. marginale and HGE and OMP-1 in E. chaffeensis. Protective immunity against ehrlichial pathogens is believed to require induction of gamma interferon (IFN-gamma) and opsonizing immunoglobulin (Ig) subclasses directed against OMP epitopes that, in concert, activate macrophages for phagocytosis and killing. Because interleukin-12 (IL-12) acts as an adjuvant for protein immunization to induce IFN-gamma and protective immunity against intracellular pathogens, we hypothesized that as an adjuvant with MSP-2, IL-12 would augment type 1 recall responses to A. marginale. IL-12 was coadsorbed with MSP-2 to alum and shown to significantly enhance IFN-gamma production by lymph node cells (LNC) and LNC-derived CD4(+) T-cell lines from immunized calves following recall stimulation with A. marginale. LNC proliferation and IL-2 production were also enhanced in IL-12-treated calves. Elevated recall proliferative responses by peripheral blood mononuclear cells were still evident 9 months after immunization. Serum IgG levels were consistently increased in IL-12 immunized calves, predominantly due to higher IgG1 responses. The results support the use of IL-12 coadsorbed with OMP of ehrlichial pathogens in alum to amplify both antibody and type-1 cytokine responses important for protective immunity.

Modulation of host immune responses by protozoal DNA

The pathology caused by acute Babesia bovis infection is similar to that seen in severe human malaria caused by Plasmodium falciparum infection, which is related to dysregulated production of inflammatory cytokines and nitric oxide (NO). We have observed induction of NO, inducible nitric oxide synthase (iNOS) and inflammatory cytokines in macrophages by B. bovis. Furthermore, proliferation of lymphocytes from individuals never exposed to certain protozoal pathogens can be induced by crude protozoal parasite extracts. We have repeatedly observed stimulation of naive PBMC from cattle to antigenic extracts of Babesia bovis. Based on recent studies demonstrating the mitogenicity of bacterial and other non-vertebrate DNAs for murine B cells and macrophages, the mitogenic properties of B. bovis DNA were examined. B. bovis and E. coli DNAs induced proliferation of PBMC and purified B cells from non-exposed cattle. Stimulatory activity was reduced by DNase treatment and methylation with CpG methylase, indicating the presence of stimulatory non-methylated CpG motifs in the B. bovis genome. B. bovis and E. coli DNAs enhanced IgG secretion by cultured B cells, stimulating IgG1 and more strongly, IgG2. Several hexameric CpG immunostimulatory sequences (ISS) active for murine B cells were identified in an 11 kb fragment of B. bovis DNA. An oligodeoxyribonucleotide containing one of these (AACGTT), located in the rhoptry associated protein-1 (rap-1) open reading frame, stimulated B cell proliferation. These studies identify a potential mechanism by which protozoal parasites may modulate host immune responses, leading to consequences such as hypergammaglobulinemia and splenomegaly. These results also support the use of ISS as vaccine adjuvants to enhance Type 1 immune responses in cattle.

Comparative effects of interleukin-12 and interleukin-4 on cytokine responses by antigen-stimulated memory CD4+ T cells of cattle: IL-12 enhances IFN-gamma production, whereas IL-4 has marginal effects on cytokine expression

Interleukin-12 (IL-12) and IL-4 are important immunoregulatory cytokines that determine the fate of naive T cells during antigen priming in mice and also influence cytokine synthesis by differentiated murine and human T cells. The roles of these cytokines in regulating the differentiation and effector function of bovine T cells are less well studied. We investigated the ability of human IL-12 and bovine IL-4 to modify cytokine expression by antigen-stimulated T cells from cattle immune to the protozoal parasites Babesia bovis and Babesia bigemina or reactive with Mycobacterium bovis purified protein derivative. Peripheral blood mononuclear cells (PBMC) were cultured with specific antigen and IL-4 or IL-12 for 1 week. Then viable lymphoblasts consisting of predominantly CD4+ T cells were restimulated with antigen and antigen-presenting cells (APC) with or without cytokine. Cell lines were cultured for several weeks, and following restimulation with antigen and APC in the absence of exogenous cytokine, the cell lines were analyzed for proliferation, interferon-gamma (IFN-gamma) production, and expression of IL-2, IL4-, IL-10, or IFN-gamma transcript levels using a quantitative competitive RT-PCR. IL-12 and IL-4 had no effect on the composition of CD4, CD8, or gammadelta T cells in the cell lines or on the level of antigen-induced proliferation. IL-12 stimulated enhanced levels of IFN-gamma protein and transcript expression in all cell lines, with no consistent effects on IL-2 or IL-4 expression. In two B. bovis-specific cell lines, IL-12 suppressed IL-10 expression. IL-4 had no consistent effect on expression of any cytokine. These results indicate the use of IL-12 as an adjuvant to enhance type 1 cytokine responses in cattle during antigen priming.