Immunogenic Eimeria tenella Glycosylphosphatidylinositol-Anchored Surface Antigens (SAGs) Induce Inflammatory Responses in Avian Macrophages

, but the ability of these proteins to stimulate immune responses in the chicken is unknown. infection. Concomitantly, treatment with rSAGs 4, 5 and 12 suppressed the expression of IL-12 and IFN-γ and elevated that of IL-10, suggesting that during infection these molecules may specifically impair the development of cellular mediated immunity. pathogenicity associated with the endogenous second generation stages

The Rhoptry Proteins ROP18 and ROP5 Mediate Toxoplasma gondii Evasion of the Murine, But Not the Human, Interferon-Gamma Response

The obligate intracellular parasite Toxoplasma gondii secretes effector proteins into the host cell that manipulate the immune response allowing it to establish a chronic infection. Crosses between the types I, II and III strains, which are prevalent in North America and Europe, have identified several secreted effectors that determine strain differences in mouse virulence. The polymorphic rhoptry protein kinase ROP18 was recently shown to determine the difference in virulence between type I and III strains by phosphorylating and inactivating the interferon-γ (IFNγ)-induced immunity-related GTPases (IRGs) that promote killing by disrupting the parasitophorous vacuole membrane (PVM) in murine cells. The polymorphic pseudokinase ROP5 determines strain differences in virulence through an unknown mechanism. Here we report that ROP18 can only inhibit accumulation of the IRGs on the PVM of strains that also express virulent ROP5 alleles. In contrast, specific ROP5 alleles can reduce IRG coating even in the absence of ROP18 expression and can directly interact with one or more IRGs. We further show that the allelic combination of ROP18 and ROP5 also determines IRG evasion and virulence of strains belonging to other lineages besides types I, II and III. However, neither ROP18 nor ROP5 markedly affect survival in IFNγ-activated human cells, which lack the multitude of IRGs present in murine cells. These findings suggest that ROP18 and ROP5 have specifically evolved to block the IRGs and are unlikely to have effects in species that do not have the IRG system, such as humans

Cell death of gamma interferon-stimulated human fibroblasts upon toxoplasma gondii infection induces early parasite egress and limits parasite replication

The intracellular protozoan parasite Toxoplasma gondii is a major food-borne illness and opportunistic infection for the immunosuppressed. Resistance to Toxoplasma is dependent on gamma interferon (IFN-¿) activation of both hematopoietic and nonhematopoietic cells. Although IFN-¿-induced innate immunity in nonhematopoietic cells has been extensively studied in mice, it remains unclear what resistance mechanisms are relied on in nonhematopoietic human cells. Here, we report an IFN-¿-induced mechanism of resistance to Toxoplasma in primary human foreskin fibroblasts (HFFs) that does not depend on the deprivation of tryptophan or iron. In addition, infection is still controlled in HFFs deficient in the p65 guanylate binding proteins GBP1 or GBP2 and the autophagic protein ATG5. Resistance is coincident with host cell death that is not dependent on the necroptosis mediator RIPK3 or caspases and is correlated with early egress of the parasite before replication. This IFN-¿-induced cell death and early egress limits replication in HFFs and could promote clearance of the parasite by immune cells

IL-15 converts human intestinal intraepithelial lymphocytes to CD94(+) producers of IFN-γ and IL-10, the latter promoting Fas ligand-mediated cytotoxicity

Intestinal intraepithelial lymphocytes (IELs), T-cell receptor αβ(+) CD8(+) T cells located between epithelial cells, are thought to contribute to Fas ligand (FL)-mediated epithelial cell death in coeliac disease, a condition characterized by excess interleukin-15 (IL-15). This study evaluates the effects of prolonged IL-15 stimulation on IELs. Human IELs were obtained from jejunal mucosa from gastric bypass operations for morbid obesity and cultured for 3 or 10 days with IL-15. As the culture progressed, an increasing number of IELs became CD94(+) and produced massive quantities of interferon-γ (IFN-γ) and IL-10. There was a steady rate of transcription with no feedback regulation. Few chronically activated IELs produced IL-2, IL-4, or tumour necrosis factor-α (TNF-α). To determine whether the accumulation of IL-10 affected IEL functions, endogenous IL-10 was neutralized by antibody during culture with IL-15. This manipulation reduced expression of CD94, NKG2D, and FL as well as FL-mediated killing of Jurkat cells by IELs. It did not affect perforin or TNF-α expression or the associated cytotoxic activities. This study shows that IL-15 induces the development of CD94(+) IELs containing IFN-γ and IL-10, and that endogenous IL-10 promotes FL-mediated cytotoxicity

K63-Linked Ubiquitination Targets <i>Toxoplasma gondii</i> for Endo-lysosomal Destruction in IFNγ-Stimulated Human Cells

<div><p><i>Toxoplasma gondii</i> is the most common protozoan parasitic infection in man. Gamma interferon (IFNγ) activates haematopoietic and non-haematopoietic cells to kill the parasite and mediate host resistance. IFNγ-driven host resistance pathways and parasitic virulence factors are well described in mice, but a detailed understanding of pathways that kill <i>Toxoplasma</i> in human cells is lacking. Here we show, that contrary to the widely held belief that the <i>Toxoplasma</i> vacuole is non-fusogenic, in an immune-stimulated environment, the vacuole of type II <i>Toxoplasma</i> in human cells is able to fuse with the host endo-lysosomal machinery leading to parasite death by acidification. Similar to murine cells, we find that type II, but not type I <i>Toxoplasma</i> vacuoles are targeted by K63-linked ubiquitin in an IFNγ-dependent manner in non-haematopoetic primary-like human endothelial cells. Host defence proteins p62 and NDP52 are subsequently recruited to the type II vacuole in distinct, overlapping microdomains with a loss of IFNγ-dependent restriction in p62 knocked down cells. Autophagy proteins Atg16L1, GABARAP and LC3B are recruited to <10% of parasite vacuoles and show no parasite strain preference, which is consistent with inhibition and enhancement of autophagy showing no effect on parasite replication. We demonstrate that this differs from HeLa human epithelial cells, where type II <i>Toxoplasma</i> are restricted by non-canonical autophagy leading to growth stunting that is independent of lysosomal acidification. In contrast to mouse cells, human vacuoles do not break. In HUVEC, the ubiquitinated vacuoles are targeted for destruction in acidified LAMP1-positive endo-lysosomal compartments. Consequently, parasite death can be prevented by inhibiting host ubiquitination and endosomal acidification. Thus, K63-linked ubiquitin recognition leading to vacuolar endo-lysosomal fusion and acidification is an important, novel virulence-driven <i>Toxoplasma</i> human host defence pathway.</p></div

Mutual interactions of the apicomplexan parasites Toxoplasma gondii and Eimeria tenella with cultured poultry macrophages

Abstract Background Toxoplasma gondii and Eimeria tenella are two common parasites in poultry. Mixed infections are likely to occur frequently in chickens due to the high prevalence of both pathogens. In this study, we investigate the co-occurrence of the two pathogens in the same immunocompetent host cell population towards potential parasite-parasite as well as altered patterns of parasite-host interactions. Methods Primary macrophages from chicken blood were co-infected in vitro with T. gondii tachyzoites (RH strain) and E. tenella sporozoites (Houghton strain) for 72 h. Morphological observations by light microscopy and assessments of parasite replication by quantitative real-time PCR (qPCR) were performed at 24, 48 and 72 h post-infection (hpi). Six host cell immune factors previously linked to T. gondii or E. tenella infection were selected for gene expression analysis in this study. Results Distinct morphological changes of macrophages were observed during mixed infection at 24 hpi and immunological activation of host cells was obvious. Macrophage mRNA expression for iNOS at 48 hpi and for TNF-α at 72 hpi were significantly elevated after mixed infection. Distinct upregulation of IL-10 was also present during co-infection compared to Eimeria mono-infection at 48 and 72 hpi. At 72 hpi, the total number of macrophages as well as the number of both parasites decreased markedly. As measured by qPCR, E. tenella population tended to increase during T. gondii co-infection, while T. gondii replication was not distinctly altered. Conclusions Mutual interactions of T. gondii and E. tenella were observed in the selected co-infection model. The interactions are supposed to be indirect considering the observed changes in host cell metabolism. This study would thus help understanding the course of co-infection in chickens that may be relevant in terms of veterinary and zoonotic considerations