Gene expression profile of CD4+ T cells reveals an interferon signaling suppression associated with progression of experimental Schistosoma japonicum infection

Gene expression changes in mammalian hosts during schistosomiasis: a review

Schistosomiasis affects over 250 million people worldwide with an estimated mortality of more than 200,000 deaths per year in sub-Saharan Africa. Efforts to control schistosomiasis in the affected areas have mainly relied on mass administration of praziquantel, which kills adult but not immature worms of all Schistosoma species. Mammalian hosts respond differently to Schistosoma infection with some being more susceptible than others, which is associated with risk factors such as sociodemographic, epidemiological, immunological and/or genetic. Host genetic factors play a major role in influencing molecular processes in response to schistosomiasis as shown in gene expression studies. These studies highlight gene profiles expressed at different time points of infection using model animals. Immune function related genes; cytokines (Th1 and Th17) are upregulated earlier in infection and Th2 upregulated later indicating a mixed Th1/Th2 response. However, Th1 response has been shown to be sustained in S. japonicum infection. Immune mediators such as matrix metalloproteinases (Mmps) and tissue inhibitors of matrix metalloproteinases (Timps) are expressed later in the infection and these are linked to wound healing and fibrosis. Downregulation of metabolic associated genes is recorded in later stages of infection. Most mammalian host gene expression studies have been done using rodent models, with fewer in larger hosts such as bovines and humans. The majority of these studies have focused on S. japonicum infections and less on S. haematobium and S. mansoni infections (the two species that cause most global infections). The few human schistosomiasis gene expression studies so far have focused on S. japonicum and S. haematobium infections and none on S. mansoni, as far as we are aware. This highlights a paucity of gene expression data in humans, specifically with S. mansoni infection. This data is important to understand the disease pathology, identify biomarkers, diagnostics and possible drug targets.

Switched phenotypes of macrophages during the different stages of Schistosoma japonicum infection influenced the subsequent trends of immune responses

BACKGROUND

Macrophages play crucial roles in immune responses during the course of schistosomal infections.

METHODS

We currently investigated influence of immunocompetent changes in macrophages via microarray-based analysis, mRNA expression analysis, detection of serum cytokines, and subsequent evaluation of the immune phenotypes following the differentiation of infection-induced lymphocytes in a unique T1/T2 double-transgenic mouse model.

RESULTS

The gradual upregulation of genes encoding YM1, YM2, and interleukin (IL)-4/IL-13 receptors in infected mice indicated the role of type 2 alternatively activated macrophages (M2, AAMφs) in immune responses after Schistosoma japonicum egg production. FACS analysis showed that surface markers MHC class II (IA/IE) and CD8α⁺ of the macrophages also exhibited a dramatic change at the various time points before and after egg-production. The transgenic mouse experiments further demonstrated that the shifting of macrophage phenotypes influenced the percentage of helper T (Th)-2 cells, which was observed to be higher than that of Th1 cells, which increased only at 3 and 5 weeks post-infection. The differentiation of effector B cells showed a similar but more significant trend toward type-2 immunity.

CONCLUSION

These results suggest that the infection of mice with S. japonicum resulted in a final Th2- and Be2-skewed immune response. This may be due to phenotypic changes in the macrophages. The influence of alternatively activated macrophages was also activated by S. japonicum egg production. This study elucidated the existence of variations in immune mechanisms at the schistosome infection stages.

Impact of Endemic Infections on HIV Susceptibility in Sub-Saharan Africa

Human immunodeficiency virus (HIV) remains a leading cause of global morbidity with the highest burden in Sub-Saharan Africa (SSA). For reasons that are incompletely understood, the likelihood of HIV transmission is several fold higher in SSA than in higher income countries, and most of these infections are acquired by young women. Residents of SSA are also exposed to a variety of endemic infections, such as malaria and various helminthiases that could influence mucosal and systemic immunology. Since these immune parameters are important determinants of HIV acquisition and progression, this review explores the possible effects of endemic infections on HIV susceptibility and summarizes current knowledge of the epidemiology and underlying immunological mechanisms by which endemic infections could impact HIV acquisition. A better understanding of the interaction between endemic infections and HIV may enhance HIV prevention programs in SSA.

Schistosoma mansoni treatment reduces HIV entry into cervical CD4+ T cells and induces IFN-I pathways

Schistosoma mansoni (Sm) infection has been linked with an increased risk of HIV acquisition in women. Therefore, defining the mechanism(s) by which Sm alters HIV susceptibility might lead to new HIV prevention strategies. Here, we analyze the impact of standard Sm therapy in HIV-uninfected Sm+ Ugandan adult women on genital HIV susceptibility and mucosal and systemic immunology. Schistosomiasis treatment induces a profound reduction of HIV entry into cervical and blood CD4+ T cells that is sustained for up to two months, despite transient systemic and mucosal immune activation and elevated genital IL-1α levels. Genital IFN-α2a levels are also elevated post-treatment, and IFN-α2a blocks HIV entry into primary CD4+ T cells ex vivo. Transcriptomic analysis of blood mononuclear cells post-Sm treatment shows IFN-I pathway up-regulation and partial reversal of Sm-dysregulated interferon signaling. These findings indicate that Sm therapy may reduce HIV susceptibility for women with Sm infection, potentially through de-repression of IFN-I pathways.

Mice lack of LRG-47 display the attenuated outcome of infection with Schistosoma japonicum

Interferon-inducible GTPase LRG-47 (also named immune-related GTPase M, Irgm1) is a member of the p47 GTPase family that has been shown to regulate host resistance to intracellular pathogens. Little knowledge has been known about the role of LRG-47 in host's responses to extracellular pathogens. To investigate possible roles of LRG-47 in the course of Schistosoma japonicum infection, LRG-47-deficient (LRG-47(-/-)) and wild-type (WT) mice were challenged with cercariae of S. japonicum, and the cellular and humoral responses in mice were analyzed. At the acute stage of S. japonicum infection, in contrast to WT mice, LRG-47(-/-) mice showed the significantly decreased egg burden, low schistosome-specific antibody response, and the decreased Th1 and increased Tc1 responses. Additionally, Schistosoma japonicum-specific egg antigen immunization also produced the similar humoral and cellular immune responses as S. japonicum infection. Taken together, these data suggested that the deficiency of LRG-47 might affect host's CD4(+) T cell immune response via the weakening of IFN-γ downstream signaling; however, the specific function of LRG-47 on dealing with extracellular worm needs to be further studied.

Schistosoma japonicum infection induces macrophage polarization

The role of macrophages (Mφ) as the first line of host defense is well accepted. These cells play a central role in orchestrating crucial functions during schistosomal infection. Thus, understanding the functional diversity of these cells in the process of infection as well as the mechanisms underlying these events is crucial for developing disease control strategies. In this study, we adopted a Mφ polarization recognition system. M1 macrophage was characterized by expressing CD16/32, IL-12 and iNOS. M2 macrophage was characterized by expressing CD206, IL-10 and arg-1. In vivo (mouse peritoneal macrophages of different infection stages were obtained) and in vitro (different S. japonicum antigens were used to stimulate RAW264.7) were characterized by using the above mentioned system. NCA and ACA stimulated RAW264.7 express significantly higher levels of IL-12 while significantly higher levels of IL-10 were detected after soluble egg antigen (SEA) stimulation. The results showed that dramatic changes of antigen in the microenvironment before and after egg production led to macrophage polarization. Furthermore, through TLR blocking experiments, the TLR4 signaling pathway was found to play a role in the process of macrophage polarization toward M1. Our data suggest that macrophage polarization during S. japonicum infection had significant effects on host immune responses to S. japonicum.

A study of immunomodulatory genes responses to macrophages of Schistosoma japonicum infection during different stages by microarray analysis

Macrophages initiate, modulate, and also serve as final effector cells in immune responses during the course of schistosomal infections. In this study, we investigated the gene expression profile and functional changes of macrophages in immune responses against the Schistosoma japonicum by microarray analysis. Hierarchical clustering analysis demonstrated that a significant switch in gene transformation associated with a type-1 response and linked with a type-2 cytokine phenotype occurs between 4.5 and 8 weeks post-infection. Moreover, the gene profiles at 3 later time-points following egg challenge were similar in complexity and magnitude. The data also showed that there were mostly inhibition of gene expression related TLR, IFN, MHC and TNFrsf at the switch between 4.5 and 8 weeks post-infection, It is suggested that these immunomodulatory genes may be down-regulated in defense against S. japonicum eggs and granuloma pathology. The induction of alternatively activated macrophage (AAMϕ) was important for dampening the inflammation in hepatic granulomas and contributing to a decrease in cytotoxicity. The gene expressions involved in repair/remodeling during liver fibrosis were also observed after egg production. Understanding the immune mechanisms associated with parasitic resistance, pathology of parasite infection, and parasite growth will provide useful insight on host-schistosome interactions and for the control of schistosomiasis.

Temporal expression of chemokines dictates the hepatic inflammatory infiltrate in a murine model of schistosomiasis

Schistosomiasis continues to be an important cause of parasitic morbidity and mortality world-wide. Determining the molecular mechanisms regulating the development of granulomas and fibrosis will be essential for understanding how schistosome antigens interact with the host environment. We report here the first whole genome microarray analysis of the murine liver during the progression of Schistosoma japonicum egg-induced granuloma formation and hepatic fibrosis. Our results reveal a distinct temporal relationship between the expression of chemokine subsets and the recruitment of cells to the infected liver. Genes up-regulated earlier in the response included T- and B-cell chemoattractants, reflecting the early recruitment of these cells illustrated by flow cytometry. The later phases of the response corresponded with peak recruitment of eosinophils, neutrophils, macrophages and myofibroblasts/hepatic stellate cells (HSCs) and the expression of chemokines with activity for these cells including CCL11 (eotaxin 1), members of the Monocyte-chemoattractant protein family (CCL7, CCL8, CCL12) and the Hepatic Stellate Cell/Fibrocyte chemoattractant CXCL1. Peak expression of macrophage chemoattractants (CCL6, CXCL14) and markers of alternatively activated macrophages (e.g. Retnla) during this later phase provides further evidence of a role for these cells in schistosome-induced pathology. Additionally, we demonstrate that CCL7 immunolocalises to the fibrotic zone of granulomas. Furthermore, striking up-regulation of neutrophil markers and the localisation of neutrophils and the neutrophil chemokine S100A8 to fibrotic areas suggest the involvement of neutrophils in S. japonicum-induced hepatic fibrosis. These results further our understanding of the immunopathogenic and, especially, chemokine signalling pathways that regulate the development of S. japonicum-induced granulomas and fibrosis and may provide correlative insight into the pathogenesis of other chronic inflammatory diseases of the liver where fibrosis is a common feature.

Schistosomiasis, a disease caused by parasitic worms, is a significant cause of illness and death in the developing world. Furthermore, recent reports suggest that the global burden of disease due to schistosomiasis has been significantly underestimated. Schistosomiasis of the liver arises due to inflammation and the deposition of scar tissue around parasite eggs trapped in this organ. In the current study we analysed the gene-expression profile of the mouse liver at several time points following infection with a virulent strain of Schistosoma japonicum to better understand the mechanisms that regulate this process. Progression of disease was associated with increased expression of different groups of genes with distinct biological functions. Specifically, we identified several genes encoding chemical signalling molecules that contribute to different phases of the response by recruiting key cell types to the site of inflammation. This study represents the most comprehensive report to date of the gene expression profile in the liver during schistosomiasis. These results provide further insight into the mechanisms that regulate the development of schistosome-induced inflammation and scarring and will aid in the development of novel treatments to alleviate the burden of disease caused by this parasite.

IFN-inducible p47 GTPases display differential responses to Schistosoma japonicum acute infection

Interferon gamma induced GTPase (IGTP) (also named Irgm3) and interferon gamma inducible protein 47 (IRG-47) (also named Irgd) are interferon (IFN)-inducible p47 GTPases that have been shown to regulate host resistance to intracellular pathogens. Little knowledge has been known about the role of p47 GTPases in host responses against extracellular pathogens. To investigate possible roles of IGTP and IRG-47 in the course of Schistosoma japonicum infection, IGTP and IRG-47 knockout and wild-type (WT) mice were challenged with cercariae of S. japonicum, and host responses were analyzed. At the acute stage of S. japonicum infection, mice that lacked IGTP displayed similar parasite burden and pathological damage to WT mice. Importantly, S. japonicum-infected IRG-47-deficient mice, in contrast to IGTP-deficient mice and WT mice, showed significantly reduced worms and lower egg-burden, but intense granulomatous reaction evoked by schistosome eggs in peripheral parts of liver lobes. In addition, upregulation of inflammation-related gene expression was observed in the spleen of IRG-47-deficient mice using oligonucleotide microarrays, in which multiple pathways of cytokine-cytokine receptor interaction, T-cell receptor signaling, complement, coagulation cascades and cell adhesion molecules were highlighted. Taken together, these data suggest that IGTP and IRG-47 might have distinct features that were differentially required for resistance to S. japonicum.

Immunopathogenesis of human schistosomiasis

Schistosomiasis continues to be a significant cause of parasitic morbidity and mortality worldwide. This review considers the basic features of the pathology and clinical outcomes of hepatointestinal and genitourinary schistosomiasis, presents an overview of the numerous studies on animal models that have clarified many of the immunopathological features, and provides insight into our current understanding of the immunopathogenesis and genetic control of human schistosomiasis. In murine schistosomiasis, pathology is induced by a CD4(+) Th2 driven granulomatous response directed against schistosome eggs lodged in the host liver. The Th2 cytokines IL-4 and IL-13 drive this response, whereas IL-10, IL13Ralpha2, IFN-gamma and a subset of regulatory T-cells act to limit schistosome induced pathology. A variety of cell types including hepatic stellate cells, alternatively activated macrophages and regulatory T-cells have also been implicated in the pathogenesis of schistosomiasis. Current knowledge suggests the immunopathogenic mechanisms underlying human schistosomiasis are likely to be similar. The review also considers the future development of anti-pathology schistosome vaccines. As fibrosis is an important feature of many other diseases such as Crohn's disease and sarcoidosis, a comprehensive understanding of the cellular and molecular mechanisms involved in schistosomiasis may also ultimately contribute to the development an effective disease intervention strategy for other granulofibrotic diseases.

The evolution of mathematical immunology

The types of mathematical models used in immunology and their scope have changed drastically in the past 10 years. Classical models were based on ordinary differential equations (ODEs), difference equations, and cellular automata. These models focused on the 'simple' dynamics obtained between a small number of reagent types (e.g. one type of receptor and one type of antigen or two T-cell populations). With the advent of high-throughput methods, genomic data, and unlimited computing power, immunological modeling shifted toward the informatics side. Many current applications of mathematical models in immunology are now focused around the concepts of high-throughput measurements and system immunology (immunomics), as well as the bioinformatics analysis of molecular immunology. The types of models have shifted from mainly ODEs of simple systems to the extensive use of Monte Carlo simulations. The transition to a more molecular and more computer-based attitude is similar to the one occurring over all the fields of complex systems analysis. An interesting additional aspect in theoretical immunology is the transition from an extreme focus on the adaptive immune system (that was considered more interesting from a theoretical point of view) to a more balanced focus taking into account the innate immune system also. We here review the origin and evolution of mathematical modeling in immunology and the contribution of such models to many important immunological concepts.

A classification of tasks for the systematic study of immune response using functional genomics data

A full understanding of the immune system and its responses to infection by different pathogens is important for the development of anti-parasitic vaccines. A growing number of large-scale experimental techniques, such as microarrays, are being used to gain a better understanding of the immune system. To analyse the data generated by these experiments, methods such as clustering are widely used. However, individual applications of these methods tend to analyse the experimental data without taking publicly available biological and immunological knowledge into account systematically and in an unbiased manner. To make best use of the experimental investment, to benefit from existing evidence, and to support the findings in the experimental data, available biological information should be included in the analysis in a systematic manner. In this review we present a classification of tasks that shows how experimental data produced by studies of the immune system can be placed in a broader biological context. Taking into account available evidence, the classification can be used to identify different ways of analysing the experimental data systematically. We have used the classification to identify alternative ways of analysing microarray data, and illustrate its application using studies of immune responses in mice to infection with the intestinal nematode parasites Trichuris muris and Heligmosomoides polygyrus.

Dynamics of CD4+CD25+ T cells in spleens and mesenteric lymph nodes of mice infected with Schistosoma japonicum

CD4+CD25+ T cells play a major role in modulating immune response, but few reports have been published about schistosomiasis. Here, we investigated the changes in CD4+CD25+ T cell populations in spleens and mesenteric lymph nodes of mice infected with Schistosoma japonicum. The proportions of CD4+CD25+ T cells in total CD4+ T cells were analyzed by flow cytometry. CD25 and Foxp3 expression was measured by real-time quantitative polymerase chain reaction. The suppressive activities of CD4+CD25+ T cells were detected by in vitro proliferation of splenocytes. Evidence showed that the percentage of CD4+CD25+ T cells was the same as controls 3 weeks post-infection. At the acute stage of infection, the percentage decreased significantly. However, at the chronic stage of infection, it rebounded to normal levels or even higher. The expression of the CD25 and Foxp3 showed gradual increase along with the infection progress. In vitro experiment also showed the strong suppressive effect of CD4+CD25+ T cells, isolated during the chronic stage, on proliferation of the CD25- splenocytes. This is the first time that the dynamics of CD4+CD25+ T cell populations was demonstrated in mice infected with schistosomiasis. In conclusion, our data indicated that CD4+CD25+ cells might be involved in the immune modulation during S. japonicum infection, which enhances current knowledge of the mechanisms of the immuno-downregulation and re-infection in schistosomiasis.

Characterization of CD4+ T cell responses in mice infected with Schistosoma japonicum

To better understand the interaction between Schistosoma japonicum and its murine host, we characterized the immune response of CD4+ T cells generated during an experimental S. japonicum infection based on different key aspects, from gene expression to cell behavior. Mouse oligonucleotide microarrays were used to compare gene expression profiles of CD4+ T cells from spleens of mice at 0, 3, 6 and 13 weeks post-infection. Flow cytometry analysis was used to determine type 1 and type 2 cytokine-secreting CD4+ T cells, to test apoptosis of CD4+ T cells and to count CD4+CD25+ T cells, a kind of regulatory subpopulation of CD4+ T cells. The percentage of interleukin-4-producing CD4+ T cells was found to be much higher than that of gamma-interferon-producing cells, especially after stimulation with S. japonicum egg antigen, which was consistent with type 1 and type 2 cytokine gene expression in the genechip. Microarray data also showed that S. japonicum induced the increased expression of Th2 response-related genes, whereas some transcripts related to the Th1 responsive pathway were depressed. Flow cytometry analysis showed a marked increase in the apoptotic CD4+ T cells from 6 weeks post-infection and in the ratio of CD4+CD25+ to CD4+ T cells in infected mice after 13 weeks. We therefore concluded that experimental infection of mice with S. japonicum resulted in a Th2-skewed immune response, which was to a great extent monitored by the immune regulatory network, including cytokine cross-modulation, cell apoptosis and the subpopulation of regulatory cells.