Lymphocyte subpopulations in the caecum mucosa of rats after infections with Eimeria separata: early responses in naive and immune animals to primary and challenge infections

Eimeria ninakohlyakimovae casts NOX-independent NETosis and induces enhanced IL-12, TNF-α, IL-6, CCL2 and iNOS gene transcription in caprine PMN

Eimeria ninakohlyakimovae represents a highly pathogenic coccidian parasite causing severe haemorrhagic typhlocolitis in goat kids worldwide. NETosis was recently described as an efficient defense mechanism of polymorphonuclear neutrophils (PMN) acting against different parasites in vitro and in vivo. In vitro interactions of caprine PMN with parasitic stages of E. ninakohlyakimovae (i. e. oocysts and sporozoites) as well as soluble oocyst antigens (SOA) were analyzed at different ratios, concentrations and time spans. Extracellular DNA staining was used to illustrate classical molecules induced during caprine NETosis [i. e. histones (H3) and neutrophil elastase (NE)] via antibody-based immunofluorescence analyses. Functional inhibitor treatments with DPI and DNase I were applied to unveil role of NADPH oxidase (NOX) and characterize DNA-backbone composition of E. ninakohlyakimovae-triggered caprine NETosis. Scanning electron microscopy (SEM)- and immunofluorescence-analyses demonstrated that caprine PMN underwent NETosis upon contact with sporozoites and oocysts of E. ninakohlyakimovae, ensnaring filaments which firmly entrapped parasites. Detailed co-localization studies of E. ninakohlyakimovae-induced caprine NETosis revealed presence of PMN-derived DNA being adorned with nuclear H3 and NE corroborating molecular characteristics of NETosis. E. ninakohlyakoimovae-induced caprine NETosis was found to be NOX-independent since DPI inhibition led to a slight decrease of NETosis. Exposure of caprine PMN to vital E. ninakohlyakimovae sporozoites as well as SOA resulted in up-regulation of IL-12, TNF-α, IL-6, CCL2 and iNOS gene transcription in stimulated PMN. Since vital E. ninakohlyakimovae-sporozoites induced caprine NETosis, this effective entrapment mechanism might reduce initial sporozoite epithelial host cell invasion during goat coccidiosis ultimately resulting in less macromeront formation and reduced merozoites I production.

Suitable in vitro culture of Eimeria bovis meront II stages in bovine colonic epithelial cells and parasite-induced upregulation of CXCL10 and GM-CSF gene transcription

We here established a suitable in vitro cell culture system based on bovine colonic epithelial cells (BCEC) for the development of Eimeria bovis merozoites I and the characterization of early parasite-induced innate epithelial host cell reactions as gene transcription of proinflammatory molecules. Both primary and permanent BCEC (BCEC (rim) and BCEC(perm)) were suitable for E. bovis merozoite I invasion and subsequent development of meronts II leading to the release of viable merozoites II. E. bovis merozoite II failed to develop any further neither into gamont nor oocyst stages in BCEC in vitro. E. bovis merozoite I induced innate epithelial host cell reactions at the level of CXC/CCL chemokines (CXCL1, CXCL8, CXCL10, CCL2), IL-6, and GM-CSF gene transcription. Overall, both BCEC types were activated by merozoite I infections since they showed significantly enhanced gene transcript levels of the immunomodulatory molecules CXCL10 and GM-CSF. However, gene transcription profiles of BCEC(prim) and BCEC(perm) revealed different reaction patterns in response to merozoite I infection with regard to quality and kinetics of chemokine/cytokine gene transcription. Although both BCEC types equally showed most prominent responses for CXCL10 and GM-CSF, the induction of CXCL1, CXCL8, CCL2, and IL-6 gene transcripts varied qualitatively and quantitatively. Our results demonstrate that BCEC seem capable to respond to E. bovis merozoite I infection by the upregulation of CXCL10 and GM-CSF gene transcription and therefore probably contribute to host innate effector mechanisms against E. bovis.

Isolation of an Eimeria ninakohlyakimovae field strain (Canary Islands) and analysis of its infection characteristics in goat kids

The current study was conducted to isolate a field strain of Eimeria ninakohlyakimovae, characterize its infectivity and the response to challenge under experimental conditions. The isolated strain (GC) induced a prepatent period of 14-15 days p.i., a patency of 7±2 days and a noticeable pathogenicity in infected goat kids. Challenge trials resulting in a decrease of oocysts per gram counts as well as a milder intensity of clinical signs in re-infected animals indicated the capacity of this strain to induce protective immune response. Altogether, the data reported in the present study suggest that the strain E. ninakohlyakimovae GC is a useful tool for the investigation of mechanisms of pathogenicity as well as host protective immune response in caprine coccidiosis, representing a valuable prerequisite for the development of future strategies in prophylaxis and control of this important parasitic disease in goat.

Microarray-based transcriptional profiling of Eimeria bovis-infected bovine endothelial host cells

Within its life cycle Eimeria bovis undergoes a long lasting intracellular development into large macromeronts in endothelial cells. Since little is known about the molecular basis of E. bovis-triggered host cell regulation we applied a microarray-based approach to define transcript variation in bovine endothelial cells early after sporozoite invasion (4 h post inoculation (p.i.)), during trophozoite establishment (4 days p.i.), during early parasite proliferation (8 days p.i.) and towards macromeront maturation (14 days p.i.). E. bovis infection led to significant changes in the abundance of many host cell gene transcripts. As infection progressed, the number of regulated genes increased such that 12, 45, 175 and 1184 sequences were modulated at 4 h, 4, 8 and 14 days p.i., respectively. These genes significantly interfered with several host cell functions, networks and canonical pathways, especially those involved in cellular development, cell cycle, cell death, immune response and metabolism. The correlation between stage of infection and the number of regulated genes involved in different aspects of metabolism suggest parasite-derived exploitation of host cell nutrients. The modulation of genes involved in cell cycle arrest and host cell apoptosis corresponds to morphological in vitro findings and underline the importance of these aspects for parasite survival. Nevertheless, the increasing numbers of modulated transcripts associated with immune responses also demonstrate the defensive capacity of the endothelial host cell. Overall, this work reveals a panel of novel candidate genes involved in E. bovis-triggered host cell modulation, providing a valuable tool for future work on this topic.

Real-time imaging of trapping and urease-dependent transmigration of Cryptococcus neoformans in mouse brain

Infectious meningitis and encephalitis is caused by invasion of circulating pathogens into the brain. It is unknown how the circulating pathogens dynamically interact with brain endothelium under shear stress, leading to invasion into the brain. Here, using intravital microscopy, we have shown that Cryptococcus neoformans, a yeast pathogen that causes meningoencephalitis, stops suddenly in mouse brain capillaries of a similar or smaller diameter than the organism, in the same manner and with the same kinetics as polystyrene microspheres, without rolling and tethering to the endothelial surface. Trapping of the yeast pathogen in the mouse brain was not affected by viability or known virulence factors. After stopping in the brain, C. neoformans was seen to cross the capillary wall in real time. In contrast to trapping, viability, but not replication, was essential for the organism to cross the brain microvasculature. Using a knockout strain of C. neoformans, we demonstrated that transmigration into the mouse brain is urease dependent. To determine whether this could be amenable to therapy, we used the urease inhibitor flurofamide. Flurofamide ameliorated infection of the mouse brain by reducing transmigration into the brain. Together, these results suggest that C. neoformans is mechanically trapped in the brain capillary, which may not be amenable to pharmacotherapy, but actively transmigrates to the brain parenchyma with contributions from urease, suggesting that a therapeutic strategy aimed at inhibiting this enzyme could help prevent meningitis and encephalitis caused by C. neoformans infection.

T cell reactions of Eimeria bovis primary and challenge-infected calves

Eimeria bovis infections commonly have clinical impact only on young animals, as homologous reinfections generally are under immunological control. So far, the nature of the immune responses delivering protection to calves has not been investigated. In this study we therefore analysed local and peripheral proliferative T cell activities of primary and challenge-infected calves and investigated the occurrence of T cell phenotypes in the peripheral blood and in mucosal gut segments isolated either by bioptic means or by necropsies.We show that lymphocytes of E. bovis-infected calves exhibit effective, transient antigen-specific proliferative responses in the course of prepatency of primary infection but fail to react after homologous reinfection suggesting early abrogation of parasite development. Whilst in primary infection an expansion of peripheral CD4+ T cells was observed, reinfection had no effect on the proportions of CD4+, CD8+ subsets or gammadeltaTCR+ T cells. In contrast, both E. bovis primary and challenge infections had an impact on local tissue T cell distribution. Primary infection was characterised by a CD4+ T cell infiltration early in prepatency in ileum and later in colon mucosa, whereas CD8+ T cells were only found accumulating in the latter gut segment. Challenge infection led to infiltration of both CD4+ and CD8+ T cells in small intestine and large intestine segments indicating protective functions of both cell types. In contrast, infiltration of ileum and colon mucosa with gammadeltaTCR+ T cells was restricted to primary infection.

Coccidia of rabbit: a review

This article summarises the current knowledge of the rabbit coccidia and the disease they cause. Various aspects, such as life cycles, localisation in the host, pathology and pathogenicity, immunity and control, are discussed.

Antigen-induced cytokine production in lymphocytes of Eimeria bovis primary and challenge infected calves

Cellular immune responses against Eimeria bovis are highly specific and a key factor for the development of protection against challenge infections. In this study we investigate the cellular immune responses of E. bovis primary and challenge infected calves stimulated in vitro by E. bovis merozoite I-antigen. Primary infection was accompanied by an increase of IFN-gamma and IL-2 gene transcription in whole blood samples, peaking during prepatency (8-12 days p.i.) and declining thereafter, whereas IL-4 gene transcription was induced predominantly in patency. IL-10 mRNA was not influenced by E. bovis infection. Both CD4+ and CD8+ T cells were identified as source of IFN-gamma gene transcripts, whilst IL-2 and IL-4 gene transcription was enhanced mainly in CD4+ T cells. Increased levels of IFN-gamma transcripts and protein were also found in lymphocytes isolated from ileocaecal lymph node biopsy 8 days p.i., and in cell culture supernatants obtained from antigen-stimulated peripheral blood mononuclear cells (PBMC) at days 8 and 12 p.i., respectively. Challenge infections of calves influenced neither IFN-gamma nor IL-2 gene transcription in peripheral blood or in lymph node-derived lymphocytes. In contrast, IL-4 gene transcription was increased in lymphocytes isolated from draining lymph nodes. Besides antigen-specific reactions we also found an infection-triggered induction of the non-specific activation state of PBMC in the course of primary infection as measured by the intracellular IFN-gamma and IL-4 content of phorbol-12-myristate-13-acetate/ionomycin-stimulated PBMC. This may represent a new mechanism of immune cells of E. bovis-infected calves contributing to ongoing immune reactions.

PMN-mediated immune reactions against Eimeria bovis

For successful in vivo infection, Eimeria bovis sporozoites have to traverse the mucosal layer of the ileum to infect lymphatic endothelial cells and may, thereby, be exposed to the interstitial fluid and to the lymph representing potential targets for leukocytes. To mimic this situation in vitro, we exposed E. bovis sporozoites to bovine PMN and found enhanced elimination of the parasites. Addition of immune serum clearly increased these reactions, whereas neonatal calf serum had no effect, thus proposing a PMN-derived antibody-dependent cytotoxicity. Scanning and transmission electron microscopy showed PMN engulfing sporozoites or extending filopodia towards them and occasionally incorporating the parasites. PMN reacted with enhanced transcription of IL-6, MCP-1, GROalpha, TNF-alpha, and iNOS genes after exposure to sporozoites while stimulation with merozoite-antigen, in addition, upregulated IL-8, IP-10 and IL-12 gene transcription. Furthermore, enhanced in vitro oxidative burst and phagocytic activities were observed after contact of PMN with viable sporozoites. To verify the potential role of PMN in the in vivo situation, we analysed the general phagocytic and oxidative burst activities of PMN obtained ex vivo from E. bovis experimentally infected calves. Enhanced levels of both activities were found early p.i. (1-5 days) and towards the end of the first schizogony (days 13-22 p.i.) underlining the in vitro data. Our results suggest that PMN-mediated, innate immune reactions play an important role in the early immune response to E. bovis infections in calves.

Eimeria bovis infection enhances adhesion of peripheral blood mononuclear cells to and their transmigration through an infected bovine endothelial cell monolayer in vitro

The first schizogony of Eimeria bovis takes place in lymphatic endothelial cells of the ileum, resulting in the formation of macroschizonts within 2-3 weeks. In this study, we analyse early cellular immune responses to infected host cells on the basis of peripheral blood mononuclear cell (PBMC) adhesion on and transmigration through infected bovine umbilical vein endothelial cell (BUVEC) monolayers. Adhesion of PBMC was upregulated by an E. bovis infection. Most marked effects were observed 1 day p.i.; thereafter, PBMC adhesion declined reaching control levels from day 8 p.i. onward. CD8(+) T cells adhered more frequently to infected BUVEC (42%) than CD4(+) T cells (25%). About one third of attached PBMC were represented by gammadelta-TCR(+) T cells. Adhesion of T cells was not restricted to parasitised host cells, but occurred almost equally on non-infected BUVEC within the same monolayer. Furthermore, we found moderately enhanced levels of PBMC transmigration through infected BUVEC monolayers, in particular on day 2 p.i. The data presented here suggest that E. bovis infection of BUVEC induces endothelial cell-derived proinflammatory reactions, which appear suitable for the initiation of both adaptive and innate immune responses.

Treatment of mice with the anticoccidial drug Toltrazuril does not interfere with the development of a specific cellular intestinal immune response to Eimeria falciformis

Immunity against Eimeria-infections is highly specific and it depends on cell-mediated effector mechanisms. Infections of BALB/c mice with 1,000 sporulated oocysts of Eimeria falciformis led to protection against challenge infections. Treatment with the anti-coccidium Toltrazuril, during primary infection, terminated the ongoing disease and did not interfere with the establishment of protective immunity against challenge infections. Mesenteric lymph node cells of infected, treated as well as non-treated and challenged BALB/c mice, showed a similar proliferation upon stimulation with parasite antigen. In contrast, neither cells of the Peyer's patches, intraepithelial lymphocytes, nor spleen cells responded to stimulation with parasite antigens. Cells from all compartments and of all investigated groups proliferated and released the cytokines IFN-gamma and IL-4 in response to the mitogen Concanavalin A. The number of cells releasing IFN-gamma or IL-4 was not dependent on the status of infection or previous treatment with Toltrazuril. The serum IgG response against total sporozoite antigens of individual mice showed that in addition, a systemic humoral response developed in infected mice, independent of a previous drug treatment, although the specific IgG antibody concentration was higher in non-treated mice. Thus, Toltrazuril does not impair the parasite specific intestinal cellular and systemic antibody response and does not prevent the development of protection against challenge infection.

In vivo expression profiles of cytokine and iNOS mRNAs in rats infected with Eimeria separata

Studies on cytokine (IFN-gamma, IL-2, IL-4, IL-5, IL-10) and inducible NO-synthase (iNOS) gene transcription in mesenteric lymph nodes (MLN) and the caecum wall were performed 0, 48, and 72h after primary and challenge infections of rats with Eimeria separata using RT-PCR. The amount of IFN-gamma mRNA was elevated in MLN and caeca 72h after primary and 48-72h after challenge infection when compared with uninfected controls. Increased amounts of IL-2 mRNA were only found in MLN of infected rats 72h post-infection (p.i.). In case of IL-10, infections did not affect the amount of mRNA in MLN, but led to markedly increased levels in the caecum wall of both infected groups 48 and 72h p.i. Levels of IL-4 mRNA remained unchanged after infections and IL-5 gene transcripts were undetectable. Amounts of iNOS mRNA (not investigated in MLN) were found strongly enhanced 48 and 72h p.i. in the caecum walls of all infected animals when compared with naive controls. The data are discussed in regard of the cellular source of the cytokines and their immunological role.