Head Kidney-Derived Macrophages of Common Carp (Cyprinus carpio L.) Show Plasticity and Functional Polarization upon Differential Stimulation

Cells from the myeloid lineage are pluripotent. To investigate the potential of myeloid cell polarization in a primitive vertebrate species, we phenotypically and functionally characterized myeloid cells of common carp (Cyprinus carpio L.) during culture. Flow cytometric analysis, Ab labeling of cell surface markers, and light microscopy showed the presence of a major population of heterogeneous macrophages after culture. These head kidney-derived macrophages can be considered the fish equivalent of bone marrow-derived macrophages and show the ability to phagocytose, produce radicals, and polarize into innate activated or alternatively activated macrophages. Macrophage polarization was based on differential activity of inducible NO synthase and arginase for innate and alternative activation, respectively. Correspondingly, gene expression profiling after stimulation with LPS or cAMP showed differential expression for most of the immune genes presently described for carp. The recently described novel Ig-like transcript 1 (NILT1) and the CXCR1 and CXCR2 chemokine receptors were up-regulated after stimulation with cAMP, an inducer of alternative activation in carp macrophages. Up-regulation of NILT1 was also seen during the later phase of a Trypanosoma carassii infection, where macrophages are primarily alternatively activated. However, NILT1 could not be up-regulated during a Trypanoplasma borreli infection, a model for innate activation. Our data suggest that NILT1, CXCR1, and CXCR2 could be considered markers for alternatively activated macrophages in fish.

Biosynthesis of costunolide, dihydrocostunolide, and leucodin. Demonstration of cytochrome p450-catalyzed formation of the lactone ring present in sesquiterpene lactones of chicory

Chicory (Cichorium intybus) is known to contain guaianolides, eudesmanolides, and germacranolides. These sesquiterpene lactones are postulated to originate from a common germacranolide, namely (+)-costunolide. Whereas a pathway for the formation of germacra-1(10),4,11(13)-trien-12-oic acid from farnesyl diphosphate had previously been established, we now report the isolation of an enzyme activity from chicory roots that converts the germacrene acid into (+)-costunolide. This (+)-costunolide synthase catalyzes the last step in the formation of the lactone ring present in sesquiterpene lactones and is dependent on NADPH and molecular oxygen. Incubation of the germacrene acid in the presence of 18O2 resulted in the incorporation of one atom of 18O into (+)-costunolide. The label was situated at the ring oxygen atom. Hence, formation of the lactone ring most likely occurs via C6-hydroxylation of the germacrene acid and subsequent attack of this hydroxyl group at the C12-atom of the carboxyl group. Blue light-reversible CO inhibition and experiments with cytochrome P450 inhibitors demonstrated that the (+)-costunolide synthase is a cytochrome P450 enzyme. In addition, enzymatic conversion of (+)-costunolide into 11(S),13-dihydrocostunolide and leucodin, a guaianolide, was detected. The first-mentioned reaction involves an enoate reductase, whereas the formation of leucodin from (+)-costunolide probably involves more than one enzyme, including a cytochrome P450 enzyme.

Placental macrophage (Hofbauer cell) polarization is independent of maternal allergen-sensitization and presence of chorioamnionitis

BACKGROUND

Macrophages can polarize in which M1/classically activated and M2/alternatively activated macrophages are considered to be the extremes. M1 macrophages are involved in inflammatory reactions, while M2 macrophages are suggested to be involved in homeostasis, parasite killing, tumor promotion, tissue remodeling and in allergic reactions. We hypothesized that polarization of placental macrophages (Hofbauer cells) is influenced by the allergen-sensitization status of the mother and/or the presence of chorioamnionitis, a placental inflammation. This Hofbauer cell polarization might be associated to the intrauterine environment and influence the risk of allergy development for the child. Therefore we aimed to determine the polarization status of Hofbauer cells in health and disease.

METHODS

We determined the expression of CD68, CX3CR1, IL-7R, DC-SIGN/CD209 and CD163 in placentas of sensitized versus non-sensitized mothers (n = 17), and placentas with or without histological chorioamnionitis (n = 10) by means of immunohistochemical analysis and quantitative real-time PCR (qPCR).

RESULTS

Protein expression of the M1 markers (CX3CR1, IL-7R and CCR7) could not be detected in any of the analyzed samples while the M2 markers (DC-SIGN, CD163 and mannose receptor/CD206) were readily detected. Significant differences between non-sensitized versus sensitized mothers and uncomplicated versus chorioamnionitis complicated pregnancies were not detected at protein or at mRNA expression level.

CONCLUSIONS

These results suggest that Hofbauer cells have an M2 phenotype, and that their polarization is not affected by maternal allergen-sensitization or by presence of chorioamnionitis.

Evolutionary conservation of alternative activation of macrophages: structural and functional characterization of arginase 1 and 2 in carp (Cyprinus carpio L.)

Classically activated macrophages (caMF) play an important role in type-I immune responses and alternatively activated macrophages (aaMF) function in type-II immune responses. While the classical activation of fish macrophages has been well described, the existence of aaMF has not yet been described for teleosts. Arginase is the characteristic enzyme in aaMF and two isoforms have been described for mammals. To study the presence of aaMF in a primitive vertebrate species we cloned arginase 1 and 2 cDNA of common carp. Carp arginase 1 is a 340 aa protein with 63% aa sequence identity to human arginase 1. Carp arginase 2 is a 347 aa protein with 63% aa sequence identity to human arginase 2. Three highly homologous arginase 2 genes were found, each showing only single non-synonymous substitutions. Basal arginase 1 expression is mainly found in carp mid kidney. In contrast, arginase 2 was expressed in all organs examined with the highest basal gene expression in liver. Cultured carp head kidney-derived macrophages were used to study aaMF in vitro. Carp macrophages showed significant arginase activity which could be induced by dibutyryl cyclic adenosine mono phosphate (cAMP) and specifically inhibited by NG-hydroxy-L-arginine (NOHA). At the gene level, arginase 2 gene expression was upregulated by cAMP stimulation, while arginase 1 gene expression was not influenced. LPS stimulation did not alter the arginase 1 or 2 expression, inducible nitric oxide synthase (iNOS) expression was, however, upregulated. This expression of iNOS was used as a measure of classical activation of carp macrophages. Thus, in contrast to mammals, fish arginase 2 and not arginase 1 is differentially regulated and likely involved in the alternative activation of fish macrophages. Our data suggest there may be an evolutionary conservation of the presence of aaMF down to teleost fish.

DNA methylation levels within the CD14 promoter region are lower in placentas of mothers living on a farm

BACKGROUND

Epigenetic regulation has been suggested to be a link between environmental intrauterine exposures and development of asthma and allergy. The placenta is an essential part of the intrauterine environment. We have previously found the innate immune receptor CD14 to be differentially expressed on the mRNA level in placentas in relation to lifestyle and parental allergen sensitization. We here hypothesized that the promoter region of CD14 may be subject to differential DNA methylation and therefore a link between intrauterine exposure and mRNA expression.

METHODS

Ninety-four placentas from the ALADDIN (Assessment of Lifestyle and Allergic Disease During Infancy) study were investigated. We used methylation-sensitive high-resolution melting (MS-HRM) analysis to semi-quantitatively analyze the DNA methylation of the promoter region of CD14 in 36 placentas known to have different CD14 mRNA expression. EpiTYPER was used to validate the MS-HRM data and to analyze an additional 58 placentas selected on mothers living on a farm or not.

RESULTS

MS-HRM analysis on 36 placenta samples revealed a relation between methylation of the CD14 promoter region with the level of CD14 mRNA expression. The MS-HRM and EpiTYPER data correlated highly significantly. EpiTYPER analysis of the additional 58 placentas demonstrated that DNA methylation in the CD14 promoter was significantly lower in placentas of mothers living on a farm compared with mothers not living on a farm.

CONCLUSION

Our data suggest that epigenetic regulation of CD14 in placenta might be involved in the protective effect of 'living on a farm', with regard to allergy development.

DNA methylation in the Neuropeptide S Receptor 1 (NPSR1) promoter in relation to asthma and environmental factors

Asthma and allergy are complex disorders influenced by both inheritance and environment, a relationship that might be further clarified by epigenetics. Neuropeptide S Receptor 1 (NPSR1) has been associated with asthma and allergy and a study suggested modulation of the genetic risk by environmental factors. We aimed to study DNA methylation in the promoter region of NPSR1 in relation to asthma and environmental exposures. Electrophoretic Mobility Shift Assay (EMSA) was used to investigate potential functional roles of both genotypes and methylation status in the NPSR1 promoter. DNA methylation was analysed using EpiTYPER in blood samples from two well-characterized cohorts; the BIOAIR study of severe asthma in adults and the Swedish birth cohort BAMSE. We observed that DNA methylation and genetic variants in the promoter influenced the binding of nuclear proteins to DNA, suggesting functional relevance. Significant, although small, differences in methylation were related to both adult severe asthma (p = 0.0001) and childhood allergic asthma (p = 0.01). Furthermore, DNA methylation was associated with exposures such as current smoking in adults for two CpG sites (p = 0.005 and 0.04), parental smoking during infancy in the children (p = 0.02) and in which month the sample was taken (p = 0.01). In summary, DNA methylation levels in the promoter of NPSR1 showed small but significant associations with asthma, both in adults and in children, and to related traits such as allergy and certain environmental exposures. Both genetic variation and the methylated state of CpG sites seem to have an effect on the binding of nuclear proteins in the regulatory region of NPSR1 suggesting complex regulation of this gene in asthma and allergy.

Segment 8 encodes a structural protein of infectious salmon anaemia virus (ISAV); the co-linear transcript from Segment 7 probably encodes a non-structural or minor structural protein

In this study we present the cloning, expression and partial identification of Genomic Segment 7 of infectious salmon anaemia virus (ISAV). The nucleotide sequence corresponding to Segment 7 was isolated from a bacteriophage lambda cDNA library and contained 2 overlapping open reading frames (ORFs) of 903 and 522 bases respectively. It also contained an ISAV-specific conserved nucleotide motif in the mRNA 5' region. The co-linear transcript representing the large ORF undergoes a splicing event that removes a 526 nucleotide intron to form a mRNA corresponding to the smaller reading frame. Thus, ISAV Genomic Segment 7 has a similar coding strategy as influenza A virus Segments 7 and 8. The largest ORF of Segment 7 and the first ORF of Segment 8 was expressed in E. coli as fusion proteins and rabbit antiserum was raised against the recombinant protein from Segment 8. Immunoblot studies using this antiserum and a serum against purified virus, show that Segment 8 encodes one of the major structural proteins of the virus whereas the co-linear ORF of Segment 7 probably encodes a non- or minor structural protein

Differential macrophage polarisation during parasitic infections in common carp (Cyprinus carpio L.)

In many parasitic infections both classically activated macrophages (caMF) and alternatively activated macrophages (aaMF) play a pivotal role. To investigate if both types of macrophages also play an important role during parasitic infections in fish, we infected carp with either Trypanoplasma borreli or Trypanosoma carassii and determined the activation state of the head kidney leukocytes (HKL). Nitrite production was used as read-out for caMF and arginase activity as read-out for aaMF. Basal nitrite production and arginase activity of HKL were moderately different between the two infections. Differences were observed, however, after ex vivo re-stimulation of HKL. Re-stimulation with LPS and T. borreli lysates increased nitrite production by HKL of T. borreli-infected fish. Re-stimulation with cAMP increased arginase activity in HKL of T. carassii-infected fish. Our results indicate that T. borreli-infected carp are more prone to increase nitrite production by caMF while T. carassii-infected fish are more prone to increase arginase activity by aaMF.

Evidence for allergen-specific IgE of maternal origin in human placenta

BACKGROUND

Immunoglobulin E (IgE) has been identified on macrophage-like cells in the villi of human placenta, irrespective of the serum IgE levels or allergy status of the mother. The origin of placental IgE is debated and it is not known if it is spontaneously produced, so-called 'natural IgE', or if it has any specificity for certain allergens. The aim of this study was to investigate if placental IgE originates from mother or child and to analyse its specificity.

METHODS

Immunoglobulin E was eluted from placenta by lowering the pH. Total and allergen-specific IgEs were measured in placenta eluate, maternal and cord blood plasma by means of ImmunoCAP (Phadia AB). The levels of natural antibodies were determined with an anti-phosphorylcholine (PC) enzyme-linked immunosorbent assay, as natural IgE has been shown in one previous publication with this assay.

RESULTS

Detectable amounts of IgE were eluted from 11/12 full-term placentas. Natural (anti-PC) IgE antibodies were detected in low amounts in maternal plasma but not in the placental eluate or in cord blood plasma. There was a significant correlation between the amount of total IgE eluted from placenta and the levels of total IgE in maternal plasma; however, not between maternal and cord blood plasma. Allergen-specific IgE was only found in placental eluates from mothers with specific IgE towards these allergens. Furthermore, there was a significant correlation between the amount of allergen-specific IgE eluted from placenta and the levels of allergen-specific IgE in maternal plasma. Allergen-specific IgE could not be detected in cord blood.

CONCLUSION

These results suggest a maternal origin of placental IgE, which can be allergen-specific.

Lifestyle and parental allergen sensitization are reflected in the intrauterine environment at gene expression level

BACKGROUND

Environmental factors, including the intrauterine environment, can influence the risk of allergy development. In the present study, we investigated whether lifestyle and parental allergen sensitization status are reflected at gene expression level in the intrauterine environment.

METHODS

  mRNA expression of 17 genes was determined by means of quantitative real-time PCR in term placenta of 36 families participating in the ALADDIN study (Assessment of Lifestyle and Allergic Disease During Infancy). Data were analysed using a linear regression model to estimate the influence of lifestyle and parental allergen sensitization on the relative mRNA expression levels. Immunohistochemistry on placenta biopsies was used to verify protein expression.

RESULTS

Significant differences in mRNA expression levels were detected at the foetal side of the placenta, where CD14 was expressed at higher levels in placentas from families living on a farm compared to not living on a farm, and IL-12(p40) was expressed at lower levels when the father was sensitized compared to nonsensitized. At the maternal side of the placenta, higher expression of STAT4 and lower expression of GATA3 were detected in families with sensitized compared to nonsensitized mothers, and IL-12(p40) was lower expressed when the families were living on a farm compared to not living on a farm. Immunohistochemistry performed for STAT4 and GATA3 showed that protein and mRNA levels correlated well.

CONCLUSION

Living on a farm and parental allergen sensitization are reflected in the intrauterine environment at the gene expression level.

IgE in the human placenta: why there?

Immunoglobulin E (IgE) antibodies are key effector molecules in the allergic inflammatory response and are also involved in the protection against extracellular parasites. Allergic symptoms often develop early in life, and the intrauterine environment has been proposed to play an important role in affecting the risk of later allergy development. The placenta constitutes a selective barrier between the maternal and foetal circulation. Recently, we reported that maternal IgE antibodies are present on foetal macrophages in the villous tissue of the human placenta irrespective of maternal allergy status. This review discusses the presence of IgE antibodies in the human placenta and its possible roles in normal and pathologic pregnancy. It also deals with the relationship between placental IgE and development of allergy during childhood. A better understanding of the role of IgE in placenta could give us clues on how to prevent allergy development in the future generations.

Maternal allergic disease does not affect the phenotype of T and B cells or the immune response to allergens in neonates

BACKGROUND

It is hypothesized that the in utero environment in allergic mothers can affect the neonatal immune responses. The aim of this study was to analyse the effect of maternal allergic disease on cord blood mononuclear cell (CBMC) phenotype and proliferative responses upon allergen stimulation.

METHODS

Peripheral blood mononuclear cells (PBMC) from 12 allergic and 14 nonallergic mothers and CBMC from their children were analysed. In the mothers, we determined cell proliferation, production of IL-4 and expression of FOXP3 in response to allergen stimulation. In the children, we evaluated cell proliferation and FOXP3 expression following allergen stimulation. Furthermore, expression of different homing markers on T cells and regulatory T cells and maturity of the T cells and B cell subsets were evaluated directly ex vivo.

RESULTS

The timothy- and birch-allergic mothers responded with increased proliferation and/or IL-4 production towards timothy and birch extract, respectively, when compared to nonallergic mothers. This could not be explained by impairment of FOXP3(+) regulatory T cells in the allergic mothers. CBMC proliferation and FOXP3 expression in response to allergens were not affected by the allergic status of the mother. Also, phenotype of T cells, FOXP3(+) regulatory T cells and B cells was not affected by the allergic status of the mother.

CONCLUSION

Our results suggest that maternal allergic disease has no effect on the neonatal response to allergens or the phenotype of neonatal lymphocytes. The factors studied here could, however, still affect later development of allergy.

Parasite infections revisited

Studying parasites helps reveal basic mechanisms in immunology. For long this has been recognized for studies on the immune system of mice and man. But it is not true for immunological studies on fish. To support this argument we discuss selected examples of parasite infections not only in warm-blooded but also in cold-blooded vertebrates. We point out that parasite infections deserve more attention as model systems in comparative immunology.

Mixed infection with Trypanoplasma borreli and Trypanosoma carassii induces protection: involvement of cross-reactive antibodies

Mixed infections with Trypanoplasma borreli and Trypanosoma carassii in common carp (Cyprinus carpio L.) are commonly found in nature. So far, in the laboratory, only mono-parasitic infections have been examined in more detail. We studied the influence of mixed rather than mono-parasitic infections on the protective immune response in this naturally occurring host-parasite combination. Mixed infections were established in the laboratory by i.p. injection of fixed numbers of both parasite species and confirmed by species-specific antibody staining. Species-specific parasitaemia was determined by morphological differences and by real-time PCR. T. carassii parasitaemia developed prior to T. borreli. Infections with T. borreli reached higher levels of parasitaemia, compared to T. carassii infections and T. borreli could be lethal. Interestingly, in mixed infections, peak parasitaemia levels were reduced and to a lesser extend survival was increased compared to T. borreli mono-parasitic infections. Cross-reactive antibodies increased earlier and to higher levels in mixed infected fish than in T. borreli mono-parasitic infections. Further, carp that had received a prior T. carassii infection showed increased resistance to re-infection with T. borreli. Our data indicate a protective effect of co-infection with T. carassii on the resistance to T. borreli, possibly mediated via cross-reactive antibodies. We suggest an evolutionary advantage for a co-evolution of T. borreli and T. carassii in carp.

Dual-substrate utilization by Bordetella pertussis

To improve the cultivation of Bordetella pertussis and take advantage of the newest techniques in monitoring and control, a quantitative description of substrate utilisation is necessary. Growth of the organism is limited by two main substrates. However neither interactive nor non-interactive modelling seem appropriate. A model that combines essential and enhanced kinetics was developed based on experimental observation. Instead of fitting all model parameters at once, a step-wise experimentation procedure was used. Finally two cultivations showed the accuracy of the model.

Trypanoplasma borreli cysteine proteinase activities support a conservation of function with respect to digestion of host proteins in common carp

Trypanoplasma borreli is an extracellular parasite that is transmitted by a leech vector and is naturally found in the blood of cyprinid fish. High parasitemia and associated severe anemia together with splenomegaly are typical of infection of common carp, Cyprinus carpio L. Papain-like cysteine proteinases expressed by trypanosome parasites contribute to the pathogenicity of trypanosomes, and are considered an important target for the development of new trypanocidal drugs. T. borreli is a member of the Parabodonida, sharing a common ancestor with the other Kinetoplastida. We demonstrate the presence of a cysteine proteinase expressed by T. borreli. Alignment of the sequence with other kinetoplastid cysteine proteinase sequences supports the phylogenetic hypotheses based on analyses of ribosomal RNA genes. We expressed the T. borreli cysteine proteinase in Escherichia coli, refolded the purified protein into a biologically active proteinase and showed it has cathepsin L-like activity. Addition of the (non)active proteinase to in vitro-derived carp head kidney-derived macrophages did not significantly modulate macrophage activity. Immunization of carp with the recombinant proteinase did induce a very high increase in proteinase-specific antibodies but only slightly lowered parasitemia. Digestion of host hemoglobin and immunoglobulin by the cysteine proteinase likely contribute to the pathogenicity of T. borreli. The possibility that digestion by the cysteine proteinase of host transferrin could contribute to an innate activation profile of macrophages in vivo is discussed. Our findings suggest a conservation of function with respect to cysteine proteinase activity in the Parabodonida in support of the hypotheses on the phylogeny of the Kinetoplastida.

cDNA expression library screening and identification of two novel antigens: ubiquitin and receptor for activated C kinase (RACK) homologue, of the fish parasite Trypanosoma carassii

Trypanosoma carassii is a kinetoplastid parasite infecting cyprinid fish with a high prevalence in nature. Antibodies have been shown to play a protective role in the immune response against this parasite in common carp, Cyprinus carpio. To identify immunogenic and putative protective T. carassii antigens we constructed a lambdaTriplEx2 expression library of the parasite and screened this with pooled carp immune serum collected 6 weeks post-infection. Screening of the library not only revealed ribosomal proteins but identified ubiquitin and a homologue of the receptor for activated C kinase (RACK) as immunogenic proteins. Equivalents of all these proteins have been identified as immunogenic in expression library screenings of other Trypanosomatida, suggesting an evolutionary conservation of their immunogenicity. The possibility that ubiquitin and/or the homologue of RACK could represent protective antigens and be targets for the design of novel therapies is discussed.

Placental inflammation, lifestyle, maternal and early child sensitisation to allergens - the assessment of lifestyle and allergic disease during infancy birth cohort

AIM

To investigate (i) whether maternal sensitisation to allergens, and lifestyle can influence the risk of acute and chronic inflammation of the placenta, in the forms of chorioamnionitis and villitis, respectively, and (ii) whether these placental inflammations are associated with the outcome of sensitisation for the child during preschool age.

METHODS

Placentas from term uncomplicated pregnancies (n = 275) in the assessment of lifestyle and allergic disease during infancy study were analysed for the presence of acute chorioamnionitis and chronic villitis. Stepwise logistic regression was performed to estimate the relative risk of placental inflammation in relation to maternal allergic sensitisation and lifestyle, and the association between placental inflammation and sensitisation of the child up to five years of age.

RESULTS

Parity and delivery at home were independently associated with chorioamnionitis, home delivery only with the low grade. Maternal allergic sensitisation was associated with increased risk of villitis in the bivariable model, however, not in the multivariable model. No significant associations were detected between placental inflammation and the outcome of sensitisation to allergens at five years of age.

CONCLUSION

Our data do not support the hypothesis that the increased risk for sensitisation of a child when the mother is allergic is mediated via placental inflammation.