Generating a detailed protein profile of Fasciola hepatica during the chronic stage of infection in cattle

Age-Associated Resilience Against Ischemic Injury in Mice Exposed to Transient Middle Cerebral Artery Occlusion

Ischemic stroke is the leading cause of death and disability. Although stroke mainly affects aged individuals, animal research is mostly one on young rodents. Here, we examined the development of ischemic injury in young (9-12-week-old) and adult (72-week-old) C57BL/6 and BALB/c mice exposed to 30 min of intraluminal middle cerebral artery occlusion (MCAo). Post-ischemic reperfusion did not differ between young and adult mice. Ischemic injury assessed by infarct area and blood-brain barrier (BBB) integrity assessed by IgG extravasation analysis was smaller in adult compared with young mice. Microvascular viability and neuronal survival assessed by CD31 and NeuN immunohistochemistry were higher in adult than young mice. Tissue protection was associated with stronger activation of cell survival pathways in adult than young mice. Microglial/macrophage accumulation and activation assessed by F4/80 immunohistochemistry were more restricted in adult than young mice, and pro- and anti-inflammatory cytokine and chemokine responses were reduced by aging. By means of liquid chromatography-mass spectrometry, we identified a hitherto unknown proteome profile comprising the upregulation of glycogen degradation-related pathways and the downregulation of mitochondrial dysfunction-related pathways, which distinguished post-ischemic responses of the aged compared with the young brain. Our study suggests that aging increases the brain's resilience against ischemic injury.

Omics tools enabling vaccine discovery against fasciolosis

In the past decade significant advances in our understanding of liver fluke biology have been made through in-depth interrogation and analysis of evolving Fasciola hepatica and Fasciola gigantica omics datasets. This information is crucial for developing novel control strategies, particularly vaccines necessitated by the global spread of anthelmintic resistance. Distilling them down to a manageable number of testable vaccines requires combined rational, empirical, and collaborative approaches. Despite a lack of clear outstanding vaccine candidate(s), we must continue to identify salient parasite-host interacting molecules, likely in the secretory products, tegument, or extracellular vesicles, and perform robust trials especially in livestock, using present and emerging vaccinology technologies to discover that elusive liver fluke vaccine. Omics tools are bringing this prospect ever closer.

Fasciola hepatica Gastrodermal Cells Selectively Release Extracellular Vesicles via a Novel Atypical Secretory Mechanism

The liver fluke, Fasciola hepatica, is an obligate blood-feeder, and the gastrodermal cells of the parasite form the interface with the host’s blood. Despite their importance in the host–parasite interaction, in-depth proteomic analysis of the gastrodermal cells is lacking. Here, we used laser microdissection of F. hepatica tissue sections to generate unique and biologically exclusive tissue fractions of the gastrodermal cells and tegument for analysis by mass spectrometry. A total of 226 gastrodermal cell proteins were identified, with proteases that degrade haemoglobin being the most abundant. Other detected proteins included those such as proton pumps and anticoagulants which maintain a microenvironment that facilitates digestion. By comparing the gastrodermal cell proteome and the 102 proteins identified in the laser microdissected tegument with previously published tegument proteomic datasets, we showed that one-quarter of proteins (removed by freeze–thaw extraction) or one-third of proteins (removed by detergent extraction) previously identified as tegumental were instead derived from the gastrodermal cells. Comparative analysis of the laser microdissected gastrodermal cells, tegument, and F. hepatica secretome revealed that the gastrodermal cells are the principal source of secreted proteins, as well as showed that both the gastrodermal cells and the tegument are likely to release subpopulations of extracellular vesicles (EVs). Microscopical examination of the gut caeca from flukes fixed immediately after their removal from the host bile ducts showed that selected gastrodermal cells underwent a progressive thinning of the apical plasma membrane which ruptured to release secretory vesicles en masse into the gut lumen. Our findings suggest that gut-derived EVs are released via a novel atypical secretory route and highlight the importance of the gastrodermal cells in nutrient acquisition and possible immunomodulation by the parasite.

Interaction of melatonin and Bmal1 in the regulation of PI3K/AKT pathway components and cellular survival

The circadian rhythm is driven by a master clock within the suprachiasmatic nucleus which regulates the rhythmic secretion of melatonin. Bmal1 coordinates the rhythmic expression of transcriptome and regulates biological activities, involved in cell metabolism and aging. However, the role of Bmal1 in cellular- survival, signaling, its interaction with intracellular proteins, and how melatonin regulates its expression is largely unclear. Here we observed that melatonin increases the expression of Bmal1 and both melatonin and Bmal1 increase cellular survival after oxygen glucose deprivation (OGD) while the inhibition of Bmal1 resulted in the decreased cellular survival without affecting neuroprotective effects of melatonin. By using a planar surface immunoassay for PI3K/AKT signaling pathway components, we revealed that both melatonin and Bmal1 increased phosphorylation of AKT, ERK-1/2, PDK1, mTOR, PTEN, GSK-3αβ, and p70S6K. In contrast, inhibition of Bmal1 resulted in decreased phosphorylation of these proteins, which the effect of melatonin on these signaling molecules was not affected by the absence of Bmal1. Besides, the inhibition of PI3K/AKT decreased Bmal1 expression and the effect of melatonin on Bmal1 after both OGD in vitro and focal cerebral ischemia in vivo. Our data demonstrate that melatonin controls the expression of Bmal1 via PI3K/AKT signaling, and Bmal1 plays critical roles in cellular survival via activation of survival kinases.

Proteomic identification of galectin-11 and -14 ligands from Fasciola hepatica

Fasciola hepatica is a globally distributed zoonotic trematode that causes fasciolosis in livestock, wildlife, ruminants and humans. Fasciolosis causes a significant economic impact on the agricultural sector and affects human health. Due to the increasing prevalence of triclabendazole resistance in F. hepatica, alternative treatment methods are required. Many protein antigens have been trialled as vaccine candidates with low success, however, the tegument of F. hepatica is highly glycosylated and the parasite-derived glycoconjugate molecules have been identified as an important mediator in host-parasite interactions and as prime targets for the host immune system. Galectin-11 (LGALS-11) and galectin-14 (LGALS-14) are two ruminant-specific glycan-binding proteins, showing upregulation in the bile duct of sheep infected with F. hepatica, which are believed to mediate host-parasite interaction and innate immunity against internal parasites. For the first known time, this study presents the ligand profile of whole worm and tegument extracts of F. hepatica that interacted with immobilised LGALS-11 and LGALS-14. LGALS-14 interacted with a total of 255 F. hepatica proteins. The protein which had the greatest interaction was identified as an uncharacterised protein which contained a C-type lectin domain. Many of the other proteins identified were previously trialled vaccine candidates including glutathione S-transferase, paramyosin, cathepsin L, cathepsin B, fatty acid binding protein and leucine aminopeptidase. In comparison to LGALS-14, LGALS-11 interacted with only 49 F. hepatica proteins and it appears to have a much smaller number of binding partners in F. hepatica. This is, to our knowledge, the first time host-specific lectins have been used for the enrichment of F. hepatica glycoproteins and this study has identified a number of glycoproteins that play critical roles in host-parasite interactions which have the potential to be novel vaccine candidates.

The importance of extracellular vesicle purification for downstream analysis: A comparison of differential centrifugation and size exclusion chromatography for helminth pathogens

BACKGROUND

Robust protocols for the isolation of extracellular vesicles (EVs) from the rest of their excretory-secretory products are necessary for downstream studies and application development. The most widely used purification method of EVs for helminth pathogens is currently differential centrifugation (DC). In contrast, size exclusion chromatography (SEC) has been included in the purification pipeline for EVs from other pathogens, highlighting there is not an agreed research community 'gold standard' for EV isolation. In this case study, Fasciola hepatica from natural populations were cultured in order to collect EVs from culture media and evaluate a SEC or DC approach to pathogen helminth EV purification.

METHODOLOGY/PRINCIPAL FINDINGS

Transmission electron and atomic force microscopy demonstrated that EVs prepared by SEC were both smaller in size and less diverse than EV resolved by DC. Protein quantification and Western blotting further demonstrated that SEC purification realised a higher EV purity to free excretory-secretory protein (ESP) yield ratio compared to DC approaches as evident by the reduction of soluble free cathepsin L proteases in SEC EV preparations. Proteomic analysis further highlighted DC contamination from ESP as shown by an increased diversity of protein identifications and unique peptide hits in DC EVs as compared to SEC EVs. In addition, SEC purified EVs contained less tegumental based proteins than DC purified EVs.

CONCLUSIONS/SIGNIFICANCE

The data suggests that DC and SEC purification methods do not isolate equivalent EV population profiles and caution should be taken in the choice of EV purification utilised, with certain protocols for DC preparations including more free ES proteins and tegumental artefacts. We propose that SEC methods should be used for EV purification prior to downstream studies.

Time-of-Day Dependent Neuronal Injury After Ischemic Stroke: Implication of Circadian Clock Transcriptional Factor Bmal1 and Survival Kinase AKT

Occurrence of stroke cases displays a time-of-day variation in human. However, the mechanism linking circadian rhythm to the internal response mechanisms against pathophysiological events after ischemic stroke remained largely unknown. To this end, temporal changes in the susceptibility to ischemia/reperfusion (I/R) injury were investigated in mice in which the ischemic stroke induced at four different Zeitgeber time points with 6-h intervals (ZT0, ZT6, ZT12, and ZT18). Besides infarct volume and brain swelling, neuronal survival, apoptosis, ischemia, and circadian rhythm related proteins were examined using immunohistochemistry, Western blot, planar surface immune assay, and liquid chromatography-mass spectrometry tools. Here, we present evidence that midnight (ZT18; 24:00) I/R injury in mice resulted in significantly improved infarct volume, brain swelling, neurological deficit score, neuronal survival, and decreased apoptotic cell death compared with ischemia induced at other time points, which were associated with increased expressions of circadian proteins Bmal1, PerI, and Clock proteins and survival kinases AKT and Erk-1/2. Moreover, ribosomal protein S6, mTOR, and Bad were also significantly increased, while the levels of PRAS40, negative regulator of AKT and mTOR, and phosphorylated p53 were decreased at this time point compared to ZT0 (06:00). Furthermore, detailed proteomic analysis revealed significantly decreased CSKP, HBB-1/2, and HBA levels, while increased GNAZ, NEGR1, IMPCT, and PDE1B at midnight as compared with early morning. Our results indicate that nighttime I/R injury results in less severe neuronal damage, with increased neuronal survival, increased levels of survival kinases and circadian clock proteins, and also alters the circadian-related proteins.

Advances in Fasciola hepatica research using 'omics' technologies

The liver fluke Fasciola hepatica is an economically important pathogen of livestock worldwide, as well as being an important neglected zoonosis. Parasite control is reliant on the use of drugs, particularly triclabendazole, which is effective against multiple parasite stages. However, the spread of parasites resistant to triclabendazole has intensified the pursuit for novel control strategies. Emerging 'omics' technologies are helping advance our understanding of liver fluke biology, specifically the molecules that act at the host-parasite interface and are central to infection, virulence and long-term survival within the definitive host. This review discusses the technological sequencing advances that have facilitated the unbiased analysis of liver fluke biology, resulting in an extensive range of 'omics' datasets. In addition, we highlight the 'omics' studies of host responses to F. hepatica infection that, when combined with the parasite datasets, provide the opportunity for integrated analyses of host-parasite interactions. These extensive datasets will form the foundation for future in-depth analysis of F. hepatica biology and development, and the search for new drug or vaccine interventions.

A novel ex vivo immunoproteomic approach characterising Fasciola hepatica tegumental antigens identified using immune antibody from resistant sheep

A more thorough understanding of the immunological interactions between Fasciola spp. and their hosts is required if we are to develop new immunotherapies to control fasciolosis. Deeper knowledge of the antigens that are the target of the acquired immune responses of definitive hosts against both Fasciola hepatica and Fasciola gigantica will potentially identify candidate vaccine antigens. Indonesian Thin Tail sheep express a high level of acquired immunity to infection by F. gigantica within 4weeks of infection and antibodies in Indonesian Thin Tail sera can promote antibody-dependent cell-mediated cytotoxicity against the surface tegument of juvenile F. gigantica in vitro. Given the high protein sequence similarity between F. hepatica and F. gigantica, we hypothesised that antibody from F. gigantica-infected sheep could be used to identify the orthologous proteins in the tegument of F. hepatica. Purified IgG from the sera of F. gigantica-infected Indonesian Thin Tail sheep collected pre-infection and 4weeks p.i. were incubated with live adult F. hepatica ex vivo and the immunosloughate (immunoprecipitate) formed was isolated and analysed via liquid chromatography-electrospray ionisation-tandem mass spectrometry to identify proteins involved in the immune response. A total of 38 proteins were identified at a significantly higher abundance in the immunosloughate using week 4 IgG, including eight predicted membrane proteins, 20 secreted proteins, nine proteins predicted to be associated with either the lysosomes, the cytoplasm or the cytoskeleton and one protein with an unknown cellular localization. Three of the membrane proteins are transporters including a multidrug resistance protein, an amino acid permease and a glucose transporter. Interestingly, a total of 21 of the 38 proteins matched with proteins recently reported to be associated with the proposed small exosome-like extracellular vesicles of adult F. hepatica, suggesting that the Indonesian Thin Tail week 4 IgG is either recognising individual proteins released from extracellular vesicles or is immunoprecipitating intact exosome-like extracellular vesicles. Five extracellular vesicle membrane proteins were identified including two proteins predicted to be associated with vesicle transport/ exocytosis (VPS4, vacuolar protein sorting-associated protein 4b and the Niemann-Pick C1 protein). RNAseq analysis of the developmental transcription of the 38 immunosloughate proteins showed that the sequences are expressed over a wide abundance range with 21/38 transcripts expressed at a relatively high level from metacercariae to the adult life cycle stage. A notable feature of the immunosloughates was the absence of cytosolic proteins which have been reported to be secreted markers for damage to adult flukes incubated in vitro, suggesting that the proteins observed are not inadvertent contaminants leaking from damaged flukes ex vivo. The identification of tegument protein antigens shared between F. gigantica and F. hepatica is beneficial in terms of the possible development of a dual purpose vaccine effective against both fluke species.

Changes in serum proteins after endotoxin administration in healthy and choline-treated calves

BACKGROUND

This study aimed to investigate the possible serum protein changes after endotoxin administration in healthy and choline-treated calves using proteomics. These results are expected to contribute to the understanding of the pathophysiological mechanisms of endotoxemia and the beneficial effect of choline administration in this clinical situation.

METHODS

Healthy-calves (n = 20) were divided into 4 groups: Control, Choline treated (C), Lipopolysaccharide administered (LPS), and LPS + C. Control calves received 0.9 % NaCl injection. Calves in C and LPS + C groups received choline chloride (1 mg/kg/iv). Endotoxin (LPS) was injected (2 μg/kg/iv) to the calves in LPS and LPS + C groups. Serum samples were collected before and after the treatments. Differentially expressed proteins (> 1.5 fold-change relative to controls) were identified by LC-MS/MS.

RESULTS

After LPS administration, 14 proteins increased, and 13 proteins decreased within 48 h as compared to controls. In the LPS group, there were significant increases in serum levels of ragulator complex protein (189-fold) and galectin-3-binding protein (10-fold), but transcription factor MafF and corticosteroid binding globulin were down regulated (≥ 5 fold). As compared with the LPS group, in LPS + C group, fibrinogen gamma-B-chain and antithrombin were up-regulated, while hemopexin and histone H4 were down-regulated. Choline treatment attenuated actin alpha cardiac muscle-1 overexpression after LPS.

CONCLUSIONS

LPS administration produces changes in serum proteins associated with lipid metabolism, immune and inflammatory response, protein binding/transport, cell adhesion, venous thrombosis, cardiac contractility and blood coagulation. The administration of choline is associated with changes in proteins which can be related with its beneficial effect in this clinical situation.

Exploring and Expanding the Fatty-Acid-Binding Protein Superfamily in Fasciola Species

The liver flukes Fasciola hepatica and F. gigantica infect livestock worldwide and threaten food security with climate change and problematic control measures spreading disease. Fascioliasis is also a foodborne disease with up to 17 million humans infected. In the absence of vaccines, treatment depends on triclabendazole (TCBZ), and overuse has led to widespread resistance, compromising future TCBZ control. Reductionist biology from many laboratories has predicted new therapeutic targets. To this end, the fatty-acid-binding protein (FABP) superfamily has proposed multifunctional roles, including functions intersecting vaccine and drug therapy, such as immune modulation and anthelmintic sequestration. Research is hindered by a lack of understanding of the full FABP superfamily complement. Although discovery studies predicted FABPs as promising vaccine candidates, it is unclear if uncharacterized FABPs are more relevant for vaccine formulations. We have coupled genome, transcriptome, and EST data mining with proteomics and phylogenetics to reveal a liver fluke FABP superfamily of seven clades: previously identified clades I-III and newly identified clades IV-VII. All new clade FABPs were analyzed using bioinformatics and cloned from both liver flukes. The extended FABP data set will provide new study tools to research the role of FABPs in parasite biology and as therapy targets.

Fasciola hepatica Surface Tegument: Glycoproteins at the Interface of Parasite and Host

Fasciola hepatica, commonly known as liver fluke, is a trematode that causes Fasciolosis in ruminants and humans. The outer tegumental coat of F. hepatica (FhTeg) is a complex metabolically active biological matrix that is continually exposed to the host immune system and therefore makes a good vaccine target. F. hepatica tegumental coat is highly glycosylated and helminth-derived immunogenic oligosaccharide motifs and glycoproteins are currently being investigated as novel vaccine candidates. This report presents the first systematic characterization of FhTeg glycosylation using lectin microarrays to characterize carbohydrates motifs present, and lectin histochemistry to localize these on the F. hepatica tegument. We discovered that FhTeg glycoproteins are predominantly oligomannose oligosaccharides that are expressed on the spines, suckers and tegumental coat of F. hepatica and lectin blot analysis confirmed the abundance of N- glycosylated proteins. Although some oligosaccharides are widely distributed on the fluke surface other subsets are restricted to distinct anatomical regions. We selectively enriched for FhTeg mannosylated glycoprotein subsets using lectin affinity chromatography and identified 369 proteins by mass spectrometric analysis. Among these proteins are a number of potential vaccine candidates with known immune modulatory properties including proteases, protease inhibitors, paramyosin, Venom Allergen-like II, Enolase and two proteins, nardilysin and TRIL, that have not been previously associated with F. hepatica. Furthermore, we provide a comprehensive insight regarding the putative glycosylation of FhTeg components that could highlight the importance of further studies examining glycoconjugates in host-parasite interactions in the context of F. hepatica infection and the development of an effective vaccine.

A prospective view of animal and human Fasciolosis

Fasciolosis, a food-borne trematodiasis, results following infection with the parasites, Fasciola hepatica and Fasciola gigantica. These trematodes greatly affect the global agricultural community, infecting millions of ruminants worldwide and causing annual economic losses in excess of US $3 billion. Fasciolosis, an important zoonosis, is classified by WHO as a neglected tropical disease with an estimated 17 million people infected and a further 180 million people at risk of infection. The significant impact on agriculture and human health together with the increasing demand for animal-derived food products to support global population growth demonstrate that fasciolosis is a major One Health problem. This review details the problematic issues surrounding fasciolosis control, including drug resistance, lack of diagnosis and the threat that hybridization of the Fasciola species poses to future animal and human health. We discuss how these parasites may mediate their long-term survival through regulation and modulation of the host immune system, by altering the host immune homeostasis and/or by influencing the intestinal microbiome particularly in respect to concurrent infections with other pathogens. Large genome, transcriptome and proteomic data sets are now available to support an integrated One Health approach to develop novel diagnostic and control strategies for both animal and human disease.

The helminth parasite proteome at the host-parasite interface - Informing diagnosis and control

Helminth parasites are a significant health burden for humans in the developing world and also cause substantial economic losses in livestock production across the world. The combined lack of vaccines for the major human and veterinary helminth parasites in addition to the development of drug resistance to anthelmintics in sheep and cattle mean that controlling helminth infection and pathology remains a challenge. However, recent high throughput technological advances mean that screening for potential drug and vaccine candidates is now easier than in previous decades. A better understanding of the host-parasite interactions occurring during infection and pathology and identifying pathways that can be therapeutically targeted for more effective and 'evolution proof' interventions is now required. This review highlights some of the advances that have been made in understanding the host-parasite interface in helminth infections using studies of the temporal expression of parasite proteins, i.e. the parasite proteome, and discuss areas for potential future research and translation.

Comparative transcriptome profiling approach to glean virulence and immunomodulation-related genes of Fasciola hepatica

BACKGROUND

Fasciola hepatica causes chronic liver disease, fasciolosis, leading to significant losses in the livestock economy and concerns for human health in many countries. The identification of F. hepatica genes involved in the parasite's virulence through modulation of host immune system is utmost important to comprehend evasion mechanisms of the parasite and develop more effective strategies against fasciolosis. In this study, to identify the parasite's putative virulence genes which are associated with host immunomodulation, we explored whole transcriptome of an adult F. hepatica using current transcriptome profiling approaches integrated with detailed in silico analyses. In brief, the comparison of the parasite transcripts with the specialised public databases containing sequence data of non-parasitic organisms (Dugesiidae species and Caenorhabditis elegans) or of numerous pathogens and investigation of the sequences in terms of nucleotide evolution (directional selection) and cytokine signaling relation were conducted.

RESULTS

NGS of the whole transcriptome resulted in 19,534,766 sequence reads, yielding a total of 40,260 transcripts (N₅₀ = 522 bp). A number of the parasite transcripts (n = 1,671) were predicted to be virulence-related on the basis of the exclusive homology with the pathogen-associated data, positive selection or relationship with cytokine signaling. Of these, a group of the virulence-related genes (n = 62), not previously described, were found likely to be associated with immunomodulation based on in silico functional categorisation, showing significant sequence similarities with various immune receptors (i.e. MHC I class, TGF-β receptor, toll/interleukin-1 receptor, T-cell receptor, TNF receptor, and IL-18 receptor accessory protein), cytokines (i.e. TGF-β, interleukin-4/interleukin-13 and TNF-α), cluster of differentiations (e.g. CD48 and CD147) or molecules associated with other immunomodulatory mechanisms (such as regulation of macrophage activation). Some of the genes (n = 5) appeared to be under positive selection (Ka/Ks > 1), imitating proteins associated with cytokine signaling (through sequence homologies with thrombospondin type 1, toll/interleukin-1 receptor, TGF-β receptor and CD147).

CONCLUSIONS

With a comparative transcriptome profiling approach, we have identified a number of potential immunomodulator genes of F. hepatica (n = 62), which are firstly described here, could be employed for the development of better strategies (including RNAi) in the battle against both zoonotically and economically important disease, fasciolosis.

Liver fluke vaccines in ruminants: strategies, progress and future opportunities

The development of a vaccine for Fasciola spp. in livestock is a challenge and would be advanced by harnessing our knowledge of acquired immune mechanisms expressed by resistant livestock against fluke infection. Antibody-dependent cell-mediated cytotoxicity directed to the surface tegument of juvenile/immature flukes is a host immune effector mechanism, suggesting that antigens on the surface of young flukes may represent prime candidates for a fluke vaccine. A Type 1 immune response shortly after fluke infection is associated with resistance to infection in resistant sheep, indicating that vaccine formulations should attempt to induce Type 1 responses to enhance vaccine efficacy. In cattle or sheep, an optimal fluke vaccine would need to reduce mean fluke burdens in a herd below the threshold of 30-54 flukes to ensure sustainable production benefits. Fluke infection intensity data suggest that vaccine efficacy of approximately 80% is required to reduce fluke burdens below this threshold in most countries. With the increased global prevalence of triclabendazole-resistant Fasciolahepatica, it may be commercially feasible in the short term to introduce a fluke vaccine of reasonable efficacy that will provide economic benefits for producers in regions where chemical control of new drug-resistant fluke infections is not viable. Commercial partnerships will be needed to fast-track new candidate vaccines using acceptable adjuvants in relevant production animals, obviating the need to evaluate vaccine antigens in rodent models.