A novel in vitro model of the small intestinal epithelium in co-culture with 'gut-like' dendritic cells

Cross-talk between dendritic cells (DCs) and the intestinal epithelium is important in the decision to mount a protective immune response to a pathogen or to regulate potentially damaging responses to food antigens and the microbiota. Failures in this decision-making process contribute to the development of intestinal inflammation, making the molecular signals that pass between DCs and intestinal epithelial cells potential therapeutic targets. Until now, in vitro models with sufficient complexity to understand these interactions have been lacking. Here, we outline the development of a co-culture model of in vitro differentiated 'gut-like' DCs with small intestinal organoids (enteroids). Sequential exposure of murine bone marrow progenitors to Flt3L, granulocyte macrophage colony-stimulating factor (GM-CSF) and all-trans-retinoic acid (RA) resulted in the generation of a distinct population of conventional DCs expressing CD11b+SIRPα+CD103+/- (cDC2) exhibiting retinaldehyde dehydrogenase (RALDH) activity. These 'gut-like' DCs extended transepithelial dendrites across the intact epithelium of enteroids. 'Gut-like' DC in co-culture with enteroids can be utilized to define how epithelial cells and cDCs communicate in the intestine under a variety of different physiological conditions, including exposure to different nutrients, natural products, components of the microbiota, or pathogens. Surprisingly, we found that co-culture with enteroids resulted in a loss of RALDH activity in 'gut-like' DCs. Continued provision of GM-CSF and RA during co-culture was required to oppose putative negative signals from the enteroid epithelium. Our data contribute to a growing understanding of how intestinal cDCs assess environmental conditions to ensure appropriate activation of the immune response.

Dissecting the molecular diversity and commonality of bovine and human treponemes identifies key survival and adhesion mechanisms

Here, we report the first complete genomes of three cultivable treponeme species from bovine digital dermatitis (DD) skin lesions, two comparative human treponemes, considered indistinguishable from bovine DD species, and a bovine gastrointestinal (GI) treponeme isolate. Key genomic differences between bovine and human treponemes implicate microbial mechanisms that enhance knowledge of how DD, a severe disease of ruminants, has emerged into a prolific, worldwide disease. Bovine DD treponemes have additional oxidative stress genes compared to nearest human-isolated relatives, suggesting better oxidative stress tolerance, and potentially explaining how bovine strains can colonize skin surfaces. Comparison of both bovine DD and GI treponemes as well as bovine pathogenic and human non-pathogenic saprophyte Treponema phagedenis strains indicates genes encoding a five-enzyme biosynthetic pathway for production of 2,3-diacetamido-2,3-dideoxy-d-mannuronic acid, a rare di-N-acetylated mannuronic acid sugar, as important for pathogenesis. Bovine T. phagedenis strains further differed from human strains by having unique genetic clusters including components of a type IV secretion system and a phosphate utilisation system including phoU, a gene associated with osmotic stress survival. Proteomic analyses confirmed bovine derived T. phagedenis exhibits expression of PhoU but not the putative secretion system, whilst the novel mannuronic acid pathway was expressed in near entirety across the DD treponemes. Analysis of osmotic stress response in water identified a difference between bovine and human T. phagedenis with bovine strains exhibiting enhanced survival. This novel mechanism could enable a selective advantage, allowing environmental persistence and transmission of bovine T. phagedenis. Finally, we investigated putative outer membrane protein (OMP) ortholog families across the DD treponemes and identified several families as multi-specific adhesins capable of binding extra cellular matrix (ECM) components. One bovine pathogen specific adhesin ortholog family showed considerable serodiagnostic potential with the Treponema medium representative demonstrating considerable disease specificity (91.6%). This work has shed light on treponeme host adaptation and has identified candidate molecules for future diagnostics, vaccination and therapeutic intervention.

Bovine digital dermatitis (DD) is a severe infectious disease causing cattle lameness, which is now endemic in many countries across the world. This lameness results from inflamed lesions between the heel bulbs and is very painful resulting in poor animal welfare and substantially reduced production. There remains no single cure for DD and whilst topical antibiotic treatment enables some healing, lesions frequently reappear. Current evidence implicates bacteria known as Treponema in the pathogenesis of DD. Here we characterise the genomes of several bovine DD treponeme species as well as related bacteria from humans and the bovine gastrointestinal tract. Comparative analyses demonstrate that production of a novel mannuronic acid sugar is a key feature of bovine pathogens and several survival mechanisms were identified which likely enable the bovine pathogens to inhabit the skin surface and be transmitted within the farm environment. Studies investigating putative outer membrane proteins which are potential vaccine candidates identified that the majority have a role in host attachment, with one family of proteins exhibiting particular promise as serodiagnostic antigens. This increased understanding of the considered causal pathogens of bovine DD, together with the genomic and proteomic resources produced by this study should underpin future diagnostic, vaccination and therapeutics studies to combat this severe disease of ruminants.

Downregulation of the Central Noradrenergic System by Toxoplasma gondii Infection

Toxoplasma gondii is associated with physiological effects in the host. Dysregulation of catecholamines in the central nervous system has previously been observed in chronically infected animals. In the study described here, the noradrenergic system was found to be suppressed with decreased levels of norepinephrine (NE) in brains of infected animals and in infected human and rat neural cells in vitro The mechanism responsible for the NE suppression was found to be downregulation of dopamine β-hydroxylase (DBH) gene expression, encoding the enzyme that synthesizes norepinephrine from dopamine, with downregulation observed in vitro and in infected brain tissue, particularly in the dorsal locus coeruleus/pons region. The downregulation was sex specific, with males expressing reduced DBH mRNA levels whereas females were unchanged. Rather, DBH expression correlated with estrogen receptor in the female rat brains for this estrogen-regulated gene. DBH silencing was not a general response of neurons to infection, as human cytomegalovirus did not downregulate DBH expression. The noradrenergic-linked behaviors of sociability and arousal were altered in chronically infected animals, with a high correlation between DBH expression and infection intensity. A decrease in DBH expression in noradrenergic neurons can elevate dopamine levels, which provides a possible explanation for mixed observations of changes in this neurotransmitter with infection. Decreased NE is consistent with the loss of coordination and motor impairments associated with toxoplasmosis. Further, the altered norepinephrine synthesis observed here may, in part, explain behavioral effects of infection and associations with mental illness.

Glycolysis is important for optimal asexual growth and formation of mature tissue cysts by Toxoplasma gondii

Toxoplasma gondii can grow and replicate using either glucose or glutamine as the major carbon source. Here, we have studied the essentiality of glycolysis in the tachyzoite and bradyzoite stages of T. gondii, using transgenic parasites that lack a functional hexokinase gene (Δhk) in RH (Type-1) and Prugniaud (Type-II) strain parasites. Tachyzoite stage Δhk parasites exhibit a fitness defect similar to that reported previously for the major glucose transporter mutant, and remain virulent in mice. However, although Prugniaud strain Δhk tachyzoites were capable of transforming into bradyzoites in vitro, they were severely compromised in their ability to make mature bradyzoite cysts in the brain tissue of mice. Isotopic labelling studies reveal that glucose-deprived tacyzoites utilise glutamine to replenish glycolytic and pentose phosphate pathway intermediates via gluconeogenesis. Interestingly, while glutamine-deprived intracellular Δhk tachyzoites continued to replicate, extracellular parasites were unable to efficiently invade host cells. Further, studies on mutant tachyzoites lacking a functional phosphoenolpyruvate carboxykinase (Δpepck1) revealed that glutaminolysis is the sole source of gluconeogenic flux in glucose-deprived parasites. In addition, glutaminolysis is essential for sustaining oxidative phosphorylation in Δhk parasites, while wild type (wt) and Δpepck1 parasites can obtain ATP from either glycolysis or oxidative phosphorylation. This study provides insights into the role of nutrient metabolism during asexual propagation and development of T. gondii, and validates the versatile nature of central carbon and energy metabolism in this parasite.

Investigation of Volatile Organic Compounds Emitted from Faeces for the Diagnosis of Giardiasis

BACKGROUND

Giardiasis is a common intestinal infection caused by the flagellated intestinal protozoan Giardia duodenalis. Several methods are available for the laboratory diagnosis of Giardia, ranging from the microscopic identification of the parasite trophozoite and cyst stages, to immunodiagnosis and PCR. Giardia has unique metabolic pathways resulting from its lack of mitochondria, making it an ideal target for volatile organic compound (VOC) profiling.

AIM

To characterise the VOC profile of stool infected with Giardia to detect differences from those found in samples of diarrhoea without Giardia or other infections.

METHOD

Stool was obtained from patients with confirmed Giardia infection and controls with diarrhoea but no identifiable infection. Faecal headspace gas extraction and gas chromatography-mass spectrometry were used to extract and identify VOCs.

RESULTS

More than 100 VOCs were identified when control and Giardia groups were combined, of which 24 showed significant differences between the two groups (p<0.05). Three VOCs had a significantly greater prevalence amongst Giardia cases (p<0.0001) and 9 VOCs showed a significant difference in terms of abundance (p<0.05). AUROC analysis demonstrated a value of 0.902.

CONCLUSION

There is a significant difference in the VOC profile of stool from subjects infected with Giardia spp, when compared with non-infected controls. These findings can be explained by the unique metabolism of Giardia.

The genomic basis of parasitism in the Strongyloides clade of nematodes

Soil-transmitted nematodes, including the Strongyloides genus, cause one of the most prevalent neglected tropical diseases. Here we compare the genomes of four Strongyloides species, including the human pathogen Strongyloides stercoralis, and their close relatives that are facultatively parasitic (Parastrongyloides trichosuri) and free-living (Rhabditophanes sp. KR3021). A significant paralogous expansion of key gene families--families encoding astacin-like and SCP/TAPS proteins--is associated with the evolution of parasitism in this clade. Exploiting the unique Strongyloides life cycle, we compare the transcriptomes of the parasitic and free-living stages and find that these same gene families are upregulated in the parasitic stages, underscoring their role in nematode parasitism.

Comprehensive evaluation of Toxoplasma gondii VEG and Neospora caninum LIV genomes with tachyzoite stage transcriptome and proteome defines novel transcript features

Toxoplasma gondii is an important protozoan parasite that infects all warm-blooded animals and causes opportunistic infections in immuno-compromised humans. Its closest relative, Neospora caninum, is an important veterinary pathogen that causes spontaneous abortion in livestock. Comparative genomics of these two closely related coccidians has been of particular interest to identify genes that contribute to varied host cell specificity and disease. Here, we describe a manual evaluation of these genomes based on strand-specific RNA sequencing and shotgun proteomics from the invasive tachyzoite stages of these two parasites. We have corrected predicted structures of over one third of the previously annotated gene models and have annotated untranslated regions (UTRs) in over half of the predicted protein-coding genes. We observe distinctly long UTRs in both the organisms, almost four times longer than other model eukaryotes. We have also identified a putative set of cis-natural antisense transcripts (cis-NATs) and long intergenic non-coding RNAs (lincRNAs). We have significantly improved the annotation quality in these genomes that would serve as a manually curated dataset for Toxoplasma and Neospora research communities.

Proposal for a standard representation of two-dimensional gel electrophoresis data

The global analysis of proteins is now feasible due to improvements in techniques such as two-dimensional gel electrophoresis (2-DE), mass spectrometry, yeast two-hybrid systems and the development of bioinformatics applications. The experiments form the basis of proteomics, and present significant challenges in data analysis, storage and querying. We argue that a standard format for proteome data is required to enable the storage, exchange and subsequent re-analysis of large datasets. We describe the criteria that must be met for the development of a standard for proteomics. We have developed a model to represent data from 2-DE experiments, including difference gel electrophoresis along with image analysis and statistical analysis across multiple gels. This part of proteomics analysis is not represented in current proposals for proteomics standards. We are working with the Proteomics Standards Initiative to develop a model encompassing biological sample origin, experimental protocols, a number of separation techniques and mass spectrometry. The standard format will facilitate the development of central repositories of data, enabling results to be verified or re-analysed, and the correlation of results produced by different research groups using a variety of laboratory techniques.

Thiazolides inhibit growth and induce glutathione-S-transferase Pi (GSTP1)-dependent cell death in human colon cancer cells

Thiazolides are a novel class of broad-spectrum anti-infective drugs with promising in vitro and in vivo activities against intracellular and extracellular protozoan parasites. The nitrothiazole-analogue nitazoxanide (NTZ; 2-acetolyloxy-N-(5-nitro 2-thiazolyl) benzamide) represents the thiazolide parent compound, and a number of bromo- and carboxy-derivatives with differing activities have been synthesized. Here we report that NTZ and the bromo-thiazolide RM4819, but not the carboxy-thiazolide RM4825, inhibited proliferation of the colon cancer cell line Caco2 and nontransformed human foreskin fibroblasts (HFF) at or below concentrations the compounds normally exhibit anti-parasitic activity. Thiazolides induced typical signs of apoptosis, such as nuclear condensation, DNA fragmentation and phosphatidylserine exposure. Interestingly, the apoptosis-inducing effect of thiazolides appeared to be cell cycle-dependent and induction of cell cycle arrest substantially inhibited the cell death-inducing activity of these compounds. Using affinity chromatography and mass spectrometry glutathione-S-transferase P1 (GSTP1) from the GST class Pi was identified as a major thiazolide-binding protein. GSTP1 expression was more than 10 times higher in the thiazolide-sensitive Caco2 cells than in the less sensitive HFF cells. The enzymatic activity of recombinant GSTP1 was strongly inhibited by thiazolides. Silencing of GSTP1 using siRNA rendered cells insensitive to RM4819, while overexpression of GSTP1 increased sensitivity to RM4819-induced cell death. Thiazolides may thus represent an interesting novel class of future cancer therapeutics.

Prevalence of Cryptosporidium, Giardia and Isospora species infections in pet cats with clinical signs of gastrointestinal disease

This study reports the prevalence of Cryptosporidium, Giardia and Isospora species in cats showing signs of gastrointestinal disease. Records from a United Kingdom commercial diagnostic laboratory between December 2003 and December 2005 were reviewed. Of 1355 cats, Cryptosporidium species oocysts were found in 13 cats (1%), Giardia species trophozoites in 74 (6%), and Isospora felis oocysts in 46 (3%). In a second group of 48 cats, prevalence of Giardia species was 15% using an immunoassay for detection of antigen compared to 4% detected with microscopy. Prevalence of Giardia (9%) and Isospora (9%) species was higher in cats less than 6 months old. Gender and breed did not affect prevalence. There was a trend for Cryptosporidium and Isospora species infections to be detected in late autumn and early winter. Regional differences in prevalence were not detected. None of these organisms show a characteristic pattern of clinical signs. This study demonstrates that enteric protozoal infection is common in domestic cats showing signs of alimentary disease.

A novel Giardia lamblia nitroreductase, GlNR1, interacts with nitazoxanide and other thiazolides

The nitrothiazole analogue nitazoxanide [NTZ; 2-acetolyloxy-N-(5-nitro-2-thiazolyl)benzamide] represents the parent compound of a class of drugs referred to as thiazolides and exhibits a broad spectrum of activities against a wide variety of helminths, protozoa, and enteric bacteria infecting animals and humans. NTZ and other thiazolides are active against a wide range of other intracellular and extracellular protozoan parasites in vitro and in vivo, but their mode of action and respective subcellular target(s) have only recently been investigated. In order to identify potential targets of NTZ and other thiazolides in Giardia lamblia trophozoites, we have developed an affinity chromatography system using the deacetylated derivative of NTZ, tizoxanide (TIZ), as a ligand. Affinity chromatography on TIZ-agarose using cell extracts of G. lamblia trophozoites resulted in the isolation of an approximately 35-kDa polypeptide, which was identified by mass spectrometry as a nitroreductase (NR) homologue (EAA43030.1). NR was overexpressed as a six-histidine-tagged recombinant protein in Escherichia coli, purified, and then characterized using an assay for oxygen-insensitive NRs with dinitrotoluene as a substrate. This demonstrated that the NR was functionally active, and the protein was designated GlNR1. In this assay system, NR activity was severely inhibited by NTZ and other thiazolides, demonstrating that the antigiardial activity of these drugs could be, at least partially, mediated through inhibition of GlNR1.

A proteomic analysis of arsenical drug resistance inTrypanosoma brucei

We have undertaken 2-DE and MS to identify proteins associated with arsenical drug resistance in Trypanosoma brucei. This parasite causes sleeping sickness in humans, and arsenical drug resistance is a significant potential problem. Comparative analysis of approximately 2000 spots resolved by 2-DE in the soluble proteomes of drug-sensitive and drug-resistant isogenic lines of T. brucei identified a protein spot whose absence associated with resistance to the arsenical drug, Cymelarsan. MS matched this protein to an identical pair of tandem genes Tb09.211.0120 and 0130 that encode a putative nascent polypeptide associated complex subunit. This protein also occurs as an isoform located in both resistant and sensitive lines at a similar molecular weight, but different pI. The difference between isogenic lines was confirmed by Western blot using an antibody against recombinant protein. Both genes were identical in sequence between drug-sensitive and drug-resistant lines and both were transcribed as determined by RT-PCR. We postulate that the missing protein isoform arose due to the lack of a PTM.

Population structures and the role of genetic exchange in the zoonotic pathogen Cryptosporidium parvum

Apicomplexan protozoan parasites include some of the most globally important human and animal pathogens, all of which have obligatory sexual cycles in their definitive hosts. Despite their importance and the relevance of understanding the population genetic structure and role of genetic exchange in generating diversity, population genetic analysis has largely been restricted to Plasmodium spp. and Toxoplasma gondii. These species show a considerable diversity of population structure suggesting different strategies for transmission and survival in mammalian hosts. We have undertaken a population genetic analysis of a further apicomplexan species (Cryptosporidium parvum) to extend our understanding of the diversity of genetic structures and test whether it has a clonal population structure. Nothing is known about the population structure of this parasite. We have analyzed 180 parasite isolates from both humans and cattle derived from a single discrete geographical area, using three minisatellite and four microsatellite markers that define 38 multilocus genotypes. Analysis of linkage disequilibria between pairs of loci combined with measures of genetic distance and similarity provides evidence that the sample comprises four genetically isolated populations. One group of human isolates consists primarily of two closely related multilocus genotypes (clonal), while the major subtypes of a second group, common to both humans and animals, show a panmictic population structure. The data provide an important step in understanding the role of genetic exchange in these parasites, which is an essential prerequisite for determining the value of multilocus genotyping for the analysis of sources of human infection as well as future molecular epidemiological studies.

Seroprevalence of Neospora caninum infection in dairy and beef cattle in Paraguay

Seroprevalence of Neospora caninum in 879 beef and dairy cattle in different locations of Paraguay was determined by an ELISA. In the survey, 262 (29.8%) cattle were positive to N. caninum, and animals with anti-Neospora antibody titre were observed in all the locations tested in the country. Serum samples taken from a herd that exhibited persistent abortion had the highest percentage of animals being positive to the parasite (17/30, 56.7%). In the same herd, abortion was significantly more likely in animals with high anti-Neospora antibody titre. Immunoblot analysis demonstrated that the banding pattern from positive Paraguayan cattle was similar to that seen with the positive control sample. In conclusion, N. caninum infection is present among Paraguayan beef and dairy cattle, and it may be an important cause of bovine abortion in Paraguay.

Neosporosis. Aspects of epidemiology and host immune response

Neospora caninum is a recently recognized protozoan parasite which has been described as causing a neuromuscular paralysis in dogs and is emerging as a major cause of bovine infertility and abortion worldwide. The parasite is known to infect a range of warm blooded animals but the disease predominates in dogs and cattle. It is not yet known if N. caninum can infect and cause disease in people. The dog has recently been identified as the definitive host and the parasite may be transmitted through the ingestion of oocysts or congenitally from mother to fetus. N. caninum is known to infect red foxes (Vulpes vulpes) and coyotes (Canis latrans) and the role of wildlife species as reservoirs of infection requires further investigation. Little is known about the range of parasite genotypes within the environment or the variation in virulence between different strains. RAPD-PCR analysis of geographically distinct bovine and canine isolates has revealed little genetic variation. Epidemiological studies from different areas of the world have investigated the importance of N. caninum as an abortifacient agent and longitudinal studies have shown the high rate (approximately 80%) of congenital transmission within infected herds. Information on the rates of repeat abortion due to neosporosis are less well defined however current estimates put this at 5% suggesting that cattle may develop some form of protective immunity against N. caninum-induced abortion. Diagnosis of the disease is based upon detection of the parasite in the tissues, most commonly using immunohistochemistry with additional information provided by serology. However, although positive fetal serology is a strong indicator of exposure to the parasite, care should be taken in the interpretation of maternal serology. As we understand more about the epidemiology of neosporosis we are also better able to interpret the results of diagnostic tests. The mere presence of the parasite does not necessarily infer that this was the primary cause of abortion. CD4+ T-cells, interferon gamma and macrophages have all been found to significantly inhibit multiplication of N. caninum tachyzoites. The nature of a protective immune response and its modulation in the pregnant animal is discussed.

Toxoplasma gondii--keeping our guests under control

You might have a closer relationship than you think with one of nature's most widespread and successful parasites. Many of us harbour this subtle organism in our brains and muscles in an uneasy truce; but recent insights into its biochemistry and genetics could provide us with new ways of coping when this 'guest' gets out of hand.

A multiple antigen ELISA to detect Neospora-specific antibodies in bovine sera, bovine foetal fluids, ovine and caprine sera

Neospora caninum is a cyst-forming coccidian parasite recently identified as a cause of abortion in cattle. The epidemiology of neosporosis is poorly understood, partly because accurate diagnosis of infection is difficult. In this paper we describe the development of a multiple antigen-based enzyme-linked immunosorbent assay (ELISA) to detect antibodies to N. caninum in sera from cattle, sheep and goats as well as from bovine foetal fluids. A water-soluble fraction (wsf) of sonicated NC-1 strain tachyzoites was used as the antigen in the ELISA. Minimum optical density (OD) values that were considered to be Neospora antibody-positive, that is, the cut-off OD values were determined separately for bovine maternal sera, bovine foetal fluids, ovine sera and caprine sera; they were 0.40, 0.17, 0.23 and 0.41 OD, respectively. The ELISA gave a high signal/noise ratio, giving good sensitivity and specificity, correlating well with the indirect fluorescent antibody test (IFAT) currently used to diagnose Neospora infection in cattle, sheep and goats. In both the ELISA and immunoblot analysis using the same antigen, there was no significant cross-reactivity with sera from cattle, sheep or goats that had been infected with Toxoplasma gondii. The ELISA also showed no cross-reactivity in sera from cattle infected with Sarcocystis cruzi, Babesia divergens, B. bovis and B. bigemina. The wsf fraction of sonicated N. caninum tachyzoites used in this ELISA can be easily prepared and may be more sensitive than a single antigen ELISA, whilst still retaining good specificity.