Project description:The closely related protozoan parasites Toxoplasma gondii and Neospora caninum display similar life cycles, subcellular ultrastructure, invasion mechanisms, metabolic pathways, and genome organization, but differ in their host range and disease pathogenesis. Type II (γ) interferon has long been known to be the major mediator of innate and adaptive immunity to Toxoplasma infection, but genome-wide expression profiling of infected host cells indicates that Neospora is a potent activator of the type I (α/β) interferon pathways typically associated with antiviral responses. Infection of macrophages from mice with targeted deletions in various innate sensing genes demonstrates that host responses to Neospora are dependent on the toll-like receptor Tlr3 and the adapter protein Trif. Consistent with this observation, RNA from Neospora elicits type I interferon responses when targeted to the host endo-lysosomal system. While live Toxoplasma fails to induce type I interferon, heat-killed parasites do trigger this response, and co-infection studies reveal that T. gondii actively suppresses the production of type I interferon. These findings reveal that eukaryotic pathogens can be potent inducers of type I interferon and that some parasite species, like Toxoplasma gondii, have evolved mechanisms to suppress this response. Human foreskin fibroblasts (HFF; line BJ-5ta) were cultured to confluency in T25 flasks, infected with one representative of each of the three architypial strains of Toxoplasma gondii: GT1 (type I), Prugniaud (type II) and VEG (type III), or the closely related parasite species, Neospora caninum (strain Nc-Liv). RNA was collected from biological replicates for expression profiling by microarray. Uninfected HFF cells were used as a reference.
Project description:The closely related protozoan parasites Toxoplasma gondii and Neospora caninum display similar life cycles, subcellular ultrastructure, invasion mechanisms, metabolic pathways, and genome organization, but differ in their host range and disease pathogenesis. Type II (γ) interferon has long been known to be the major mediator of innate and adaptive immunity to Toxoplasma infection, but genome-wide expression profiling of infected host cells indicates that Neospora is a potent activator of the type I (α/β) interferon pathways typically associated with antiviral responses. Infection of macrophages from mice with targeted deletions in various innate sensing genes demonstrates that host responses to Neospora are dependent on the toll-like receptor Tlr3 and the adapter protein Trif. Consistent with this observation, RNA from Neospora elicits TLR3-dependent type I interferon responses when targeted to the host endo-lysosomal system. Although live Toxoplasma fail to induce type I interferon, heat-killed parasites do trigger this response, albeit much weaker than Neospora, and co-infection studies reveal that T. gondii actively suppresses the production of type I interferon. These findings reveal that eukaryotic pathogens can be potent inducers of type I interferon and that related parasite species interact with this pathway in distinct ways.
Project description:The closely related protozoan parasites Toxoplasma gondii and Neospora caninum display similar life cycles, subcellular ultrastructure, invasion mechanisms, metabolic pathways, and genome organization, but differ in their host range and disease pathogenesis. Type II (γ) interferon has long been known to be the major mediator of innate and adaptive immunity to Toxoplasma infection, but genome-wide expression profiling of infected host cells indicates that Neospora is a potent activator of the type I (α/β) interferon pathways typically associated with antiviral responses. Infection of macrophages from mice with targeted deletions in various innate sensing genes demonstrates that host responses to Neospora are dependent on the toll-like receptor Tlr3 and the adapter protein Trif. Consistent with this observation, RNA from Neospora elicits TLR3-dependent type I interferon responses when targeted to the host endo-lysosomal system. Although live Toxoplasma fail to induce type I interferon, heat-killed parasites do trigger this response, albeit much weaker than Neospora, and co-infection studies reveal that T. gondii actively suppresses the production of type I interferon. These findings reveal that eukaryotic pathogens can be potent inducers of type I interferon and that related parasite species interact with this pathway in distinct ways.
Project description:Intracellular parasites reprogram the host functions for their survival and reproduction. Conversely, the infected host attempts to defend the microbial insult. The extent and relevance of parasite-mediated host response in vivo remains poorly studied. We utilized Eimeria falciformis, an obligate intracellular parasite completing its entire life cycle in the mouse intestinal epithelium, to identify and validate the host determinants of the parasite infection. The most prominent mouse genes induced during the onset of asexual (24 hrs) and sexual (144 hrs) parasite cycle include IFNg-regulated factors, e.g., immunity-related GTPases IRGA6/B6/D/M2/M3, guanylate-binding proteins GBP2/3/5/8, chemokines CxCL9-11 and several enzymes of the kynurenine pathway including indoleamine 2,3-dioxygenase 1 (IDO1). These results indicated a multifarious innate defense (tryptophan catabolism, IRG, GBP, chemokines signaling) mounted by epithelial cells, and a consequential adaptive immune response (chemokines-cytokines signaling, lymphocyte recruitment). A notable increase in the inflammation- and immunity-associated transcripts correlated with the severity of infection and influx of B-cells, T-cells and macrophages to the parasitized tissue. Indeed, parasite growth was enhanced in the animals inhibited for CxCr3, a major chemokine receptor on immune cells. Interestingly, despite a prominent induction, the mouse IRGB6 failed to recognize and disrupt the parasitophorous vacuole in the parasite cultures, implying an immune evasion by E. falciformis. Likewise, the oocyst output was impaired in IFNg-R-/- and IDO1-/- mice, which signifies a subversion of IFNg-signaling by the parasite to promote its growth. In brief, the Eimeria-rodent model shows contrasting roles of IFNg-signaling for parasite development, identifies a retinue of potential host determinants, and epitomizes its efficacy for in vivo parasite-host interaction studies. Microarray experiments were performed as dual-color hybridizations on Agilent mouse whole genome catalog 44K arrays. To compensate for dye-specific effects, a dye-reversal color-swap was applied.
Project description:Hepatitis C virus (HCV) is the most common chronic blood-borne infection in the United States with the majority of patients becoming chronically infected and a subset (20%) progressing to cirrhosis and hepatocellular carcinoma. Individual variations in immune responses may help define successful resistance to infection with HCV. We have examined the immune response in primary macrophages from patients who have spontaneously cleared HCV (viral load negative, VL-, n = 37) compared to HCV genotype 1 chronically infected (VL+) subjects (n=32) and found that macrophages from VL- subjects have an elevated baseline expression of Toll-like receptor 3 (TLR3). Macrophages from HCV patients were stimulated ex vivo through the TLR3 pathway and assessed using gene expression arrays and pathway analysis. We found elevated TLR3 response genes and pathway activity from VL- subjects. Furthermore, macrophages from VL- subjects showed higher production of IFN-b and related IFN response genes by Q-PCR, and increased phosphorylation of STAT-1 by immunoblot. Analysis of polymorphisms in TLR3 revealed a significant association of intronic TLR3 polymorphism (rs13126816) with the clearance of HCV and the expression of TLR3. Of note, PBMCs from the same donors showed opposite changes in gene expression, suggesting ongoing inflammatory responses in PBMCs from VL+ HCV patients. Our results suggest that an elevated innate immune response enhances HCV clearance mechanisms and may offer a potential therapeutic approach to increase viral clearance. Differential gene expression by primary human macrophages and PBMCs from patients with spontaneous clearance of HCV (VL-) and patients with chronic HCV infection (VL+) were generated by microarray.
Project description:Cryptosporidium is a leading cause of severe diarrhea and diarrheal-related death in children worldwide. As an obligate intracellular parasite, Cryptosporidium relies on intestinal epithelial cells to provide a niche for its growth and survival, but little is known about the contributions that the infected cell makes to this relationship. Here we conducted a genome wide CRISPR/Cas9 knockout screen to discover host genes required for Cryptosporidium parvum infection and/or host cell survival. The gene enrichment analysis indicated that the host interferon response, glycosaminoglycan (GAG) and glycosylphosphatidylinositol (GPI) anchor biosynthesis are important determinants of susceptibility to C. parvum infection. Several of these pathways are linked to parasite attachment and invasion and C-type lectins on the surface of the parasite. Evaluation of transcript and protein induction of innate interferons revealed a pronounced type III interferon response to Cryptosporidium in human cells as well as in mice. Treatment of mice with IFNλ reduced infection burden and protected immunocompromised mice from severe outcomes including death, with effects that STAT1 signaling in the enterocyte. Initiation of this type III interferon response was dependent on sustained intracellular growth and mediated by the pattern recognition receptor TLR3. We conclude that host cell intrinsic recognition of Cryptosporidium results in IFNλ production critical to early protection against this infection.
Project description:Innate immune signaling has recently been shown to play an important role in nuclear reprogramming, by altering the epigenetic landscape and thereby facilitating transcription. However, the mechanisms that link innate immune activation and metabolic regulation in pluripotent stem cells remain poorly defined, particularly with regards to key molecular components. In this study, we show that hypoxia-inducible factor one (HIF1α), a central regulator of adaptation to limiting oxygen tension, is an unexpected but crucial regulator of innate immune-mediated nuclear reprogramming. HIF1α is dramatically upregulated as a consequence of Toll-like receptor 3 (TLR3) signaling and is necessary for efficient induction of pluripotency and transdifferentiation. Bioenergetics studies reveal that HIF1α regulates the reconfiguration of innate immune-mediated reprogramming through its well-established role in throwing a glycolytic switch. We believe that results from these studies can help us better understand the influence of immune signaling in tissue regeneration and lead to new therapeutic strategies.
Project description:The closely related protozoan parasites Toxoplasma gondii and Neospora caninum display similar life cycles, subcellular ultrastructure, invasion mechanisms, metabolic pathways, and genome organization, but differ in their host range and disease pathogenesis. Type II (?) interferon has long been known to be the major mediator of innate and adaptive immunity to Toxoplasma infection, but genome-wide expression profiling of infected host cells indicates that Neospora is a potent activator of the type I (?/?) interferon pathways typically associated with antiviral responses. Infection of macrophages from mice with targeted deletions in various innate sensing genes demonstrates that host responses to Neospora are dependent on the toll-like receptor Tlr3 and the adapter protein Trif. Consistent with this observation, RNA from Neospora elicits type I interferon responses when targeted to the host endo-lysosomal system. While live Toxoplasma fails to induce type I interferon, heat-killed parasites do trigger this response, and co-infection studies reveal that T. gondii actively suppresses the production of type I interferon. These findings reveal that eukaryotic pathogens can be potent inducers of type I interferon and that some parasite species, like Toxoplasma gondii, have evolved mechanisms to suppress this response. In vitro cultures of bone marrow-derived macrophages from WT or IFNAR2-/- mice were infected with either Toxoplasma gondii (VEG strain) or Neospora caninum (Nc2 strain) for 17 hours. RNA was collected from biological replicates for expression profiling by microarray. Uninfected controls for both WT and IFNAR2-/- were used as a reference.