Characterization of Angiostrongylus cantonensis excretory-secretory proteins as potential diagnostic targets

Immunoblotting Identification of Diagnostic Antigens of Paragonimus westermani Type 1 for the Detection of Human Pulmonary Paragonimiasis in North East India

Human pulmonary paragonimiasis, an emerging concern in North East India, frequently masquerades as pulmonary tuberculosis due to clinical and radiological similarities, leading to diagnostic challenges. This research aimed to harness the immunoblotting technique to discern immunodiagnostic protein antigens from both adult worm and excretory-secretory (ES) extracts of the prevalent Paragonimus westermani type 1 in Arunachal Pradesh, North East India. We studied the time kinetics of immunoreactive patterns in relation to the duration of infection in rodent models. Immunoblot analyses were also conducted using sera from ELISA-positive patients confirmed with paragonimiasis, facilitating the selection of antigenic extracts with diagnostic potential. Further, ES protein antigens were subjected to 2D immunoblot analysis and immunoreactive protein spots identified using MALDI-TOF MS. The immunoreactivity patterns of ES antigens with sera of paragonimiasis-positive patients were detailed, and specific immunoreactive protein antigens were pinpointed using peptide mass fingerprinting (MALDI-TOF). This work underscores the enhanced diagnostic accuracy when combining ELISA with immunoblotting for pulmonary paragonimiasis in regions like North East India, marked by co-existing helminth infections.

IgE antibody responses in cerebrospinal fluids relate to the brain pathologic injury of hosts with Angiostrongylus cantonensis infection

BACKGROUND

The immunoglobulin E (IgE) response to Angiostrongylus cantonensis infection increases in the host. This study analyzed the IgG and IgE responses detected in different body fluids of A. cantonensis-infected mice.

METHODS

BALB/c (high susceptibility), CBA (medium), and C57BL/6 and C57BL/10 (resistance) strain mice were used in this study. The levels of IgM, IgG, and IgE in the serum and cerebrospinal fluid (CSF) from infected mice were compared. A. cantonensis-reactive antigens from BALB/c and C57BL/6 mice CSF were also analyzed.

RESULTS

Antibodies against fifth-stage larvae (L5) antigens increased in mice CSF, particularly IgE, relate to worm rejection and the susceptibility of different mouse strains. The increased IgE level in BALB/c mice CSF is lower than that from others, suggesting IgE response in brain is more important than that in serum. Anti-L5 and anti-excretory/secretory (ES) antigen IgE and IgG responses in CSF were analyzed. In addition, the antibody-dependent eosinophil-mediated cytotoxicity induced by anti-excretory/secretory (ES) antigen antibodies may be the reason of severe brain inflammation in infected BALB/c mice. IgE and IgG antibodies against a 105 kDa protein of L5 antigen was detected at week 3 post-infection in C57BL/6 mice and week 5 post-infection in BALB/c mice. We suggest that 105 kDa protein is related with the antibody response of A. cantonensis-infected mice.

CONCLUSION

We found that IgE antibodies in mice CSF against L5 antigens related to worm rejection in mice brains. This study may help to identify specific angiostrongyliasis markers that can be applied for clinical diagnosis and treatment in future.

Angiostrongilus cantonensis an Atypical Presenilin: Epitope Mapping, Characterization, and Development of an ELISA Peptide Assay for Specific Diagnostic of Angiostrongyliasis

Background: Angiostrongyliasis, the leading cause universal of eosinophilic meningitis, is an emergent disease due to Angiostrongylus cantonensis (rat lungworm) larvae, transmitted accidentally to humans. The diagnosis of human angiostrongyliasis is based on epidemiologic characteristics, clinical symptoms, medical history, and laboratory findings, particularly hypereosinophilia in blood and cerebrospinal fluid. Thus, the diagnosis is difficult and often confused with those produced by other parasitic diseases. Therefore, the development of a fast and specific diagnostic test for angiostrongyliasis is a challenge mainly due to the lack of specificity of the described tests, and therefore, the characterization of a new target is required. Material and Methods: Using bioinformatics tools, the putative presenilin (PS) protein C7BVX5-1 was characterized structurally and phylogenetically. A peptide microarray approach was employed to identify single and specific epitopes, and tetrameric epitope peptides were synthesized to evaluate their performance in an ELISA-peptide assay. Results: The data showed that the A. cantonensis PS protein presents nine transmembrane domains, the catalytic aspartyl domain [(XD (aa 241) and GLGD (aa 332–335)], between TM6 and TM7 and the absence of the PALP and other characteristics domains of the class A22 and homologous presenilin (PSH). These individualities make it an atypical sub-branch of the PS family, located in a separate subgroup along with the enzyme Haemogonchus contournus and separated from other worm subclasses. Twelve B-linear epitopes were identified by microarray of peptides and validated by ELISA using infected rat sera. In addition, their diagnostic performance was demonstrated by an ELISA-MAP4 peptide. Conclusions: Our data show that the putative AgPS is an atypical multi-pass transmembrane protein and indicate that the protein is an excellent immunological target with two (PsAg3 and PsAg9) A. costarisencis cross-reactive epitopes and eight (PsAg1, PsAg2, PsAg6, PsAg7, PsAg8, PsAg10, PsAg11, PsAg12) apparent unique A. cantonensis epitopes. These epitopes could be used in engineered receptacle proteins to develop a specific immunological diagnostic assay for angiostrongyliasis caused by A. cantonensis.

Development of a Multiplex Bead Assay To Detect Immunoglobulin G Antibodies to Babesia duncani in Human Serum

Babesia duncani is the causative agent of babesiosis in the western United States. The indirect fluorescent antibody (IFA) assay is the diagnostic test of choice for detection of B. duncani-specific antibodies. However, this test requires parasitized red blood cells harvested from infected hamsters, and test results are often difficult to interpret. To simplify serological testing for B. duncani, a proteomics approach was employed to identify candidate immunodiagnostic antigens. Several proteins were identified by electrospray ionization mass spectrometric analysis, and four recombinant protein constructs were expressed and used in a multiplex bead assay (MBA) to detect B. duncani-specific antibodies. Two antigens, AAY83295.1 and AAY83296.1, performed well with high sensitivities and specificities. AAY83295.1 had a higher sensitivity (100%) but lower specificity (89%) than AAY83296.1, which had a sensitivity of 90% and a specificity of 96%. Combining these two antigens did not improve the performance of the assay. This MBA could be useful for diagnosis, serosurveillance, and blood donor screening for B. duncani infection.

Abdominal angiostrongyliasis in the Americas: fifty years since the discovery of a new metastrongylid species, Angiostrongylus costaricensis

Angiostrongylus costaricensis is a zoonotic parasitic nematode described for the first time in 1971 by Pedro Morera and Rodolfo Céspedes in Costa Rica. This parasite causes an infection known as abdominal angiostrongyliasis, affecting mainly school-aged children and young adults. Infection with A. costaricensis has been associated with a myriad of rodent and mollusk species in the Americas and the Caribbean, as its natural hosts and reservoirs. In this commemorative review, we highlight the extensive research collected through a 50-year journey, which includes ecological, pathological, and molecular studies on A. costaricensis and its implicated disease. We also identify major knowledge gaps in its evolutionary history, the ecological role of imported and invasive mollusk species, and immune response. We propose that the advent of -omics analyses will allow us to gather novel information regarding A. costaricensis biology and infection dynamics, as well as to promote the design of much-needed sensitive and specific diagnostic tools.

3-Hydroxybenzaldehyde and 4-Hydroxybenzaldehyde enhance survival of mouse astrocytes treated with Angiostrongylus cantonensis young adults excretory/secretory products

Background

Methods

Results

Conclusions

Angiostrongylus spp. (Nematoda; Metastrongyloidea) of global public health importance

Human angiostrongyliasis is an important foodborne zoonosis, caused by the infection with Angiostrongylus costaricensis and Angiostrongylus cantonensis. These two species have a significant public health impact in different areas of the world. Angiostrongyliasis is re-emerging and expanding to urban settings rising significant concerns regarding the control of these infections. This review focuses on aspects such as life cycle, epidemiology, clinical manifestations, diagnostics, food safety and control of illness caused especially by A. cantonensis.

Excretory/secretory products of Angiostrongylus cantonensis fifth-stage larvae induce endoplasmic reticulum stress via the Sonic hedgehog pathway in mouse astrocytes

BACKGROUND

Angiostrongylus cantonensis is an important food-borne zoonotic parasite. Humans are non-permissive hosts, and this parasite develops into fifth-stage larvae (L5) in the brain and subarachnoid cavity and then induces eosinophilic meningitis and eosinophilic meningoencephalitis. Excretory/secretory products (ESPs) are valuable targets for the investigation of host-parasite interactions. These products contain a wide range of molecules for penetrating defensive barriers and avoiding the immune response of the host. Endoplasmic reticulum (ER) stress has been found to be associated with a wide range of parasitic infections and inflammation. ER stress can increase cell survival via the activation of downstream signalling. However, the mechanisms of ER stress in A. cantonensis infection have not yet been clarified. This study was designed to investigate the molecular mechanisms of ER stress in astrocytes after treatment with the ESPs of A. cantonensis L5.

RESULTS

The results demonstrated that A. cantonensis infection activated astrocytes in the mouse hippocampus and induced the expression of ER stress-related molecules. Next, the data showed that the expression of ER stress-related molecules and the Ca²⁺ concentration were significantly increased in activated astrocytes after treatment with the ESPs of L5 of A. cantonensis. Ultimately, we found that ESPs induced GRP78 expression via the Sonic hedgehog (Shh) signalling pathway.

CONCLUSIONS

These findings suggest that in astrocytes, the ESPs of A. cantonensis L5 induce ER stress and that the Shh signalling pathway plays an important role in this process.

Application of Recombinant Angiostrongylus cantonensis Galectin-2 Protein for Serodiagnosis of Human Angiostrongyliasis by Immunoblotting

Angiostrongyliasis is a foodborne disease caused by a zoonotic nematode, Angiostrongylus cantonensis, which produces eosinophilic meningitis or meningoencephalitis (EOM) in humans. Definitive diagnosis is rarely possible because worms are almost never recovered from patients. Human disease can be diagnosed by clinical symptoms and serological tests. Presently, diagnosis is performed by serological detection of antibodies against specific somatic antigens (molecular mass 29-31 kDa) extracted from female worms. The life cycle of A. cantonensis must be maintained in the laboratory to provide a source of this diagnostic antigen. Here, we cloned and expressed recombinant A. cantonensis galectin-2 (rAcGal2) corresponding to a 31-kDa antigenic peptide. Recombinant protein was purified and used in immunoblot tests, which showed reactions with human serum panels consisting of six confirmed angiostrongyliasis and 24 clinically diagnosed cases of EOM-associated with angiostrongyliasis, 160 samples from patients with other parasitic infections, and 30 samples from normal healthy subjects. Accuracy, sensitivity, specificity, and positive and negative predictive values were 95.0%, 93.3%, 95.3%, 75.7%, and 98.9%, respectively. The test was nonreactive with sera of human gnathostomiasis and cysticercosis, two diseases that could present similar neurological symptoms. Recombinant AcGal2 has potential as a diagnostic antigen and could replace native parasite antigens in further development of an angiostrongyliasis serodiagnostic test kit.

Gene Expression in the Salivary Gland of Rhipicephalus (Boophilus) microplus Fed on Tick-Susceptible and Tick-Resistant Hosts

The success of cattle tick fixation largely depends on the secretion of substances that alter the immune response of the host. The majority of these substances are expressed by the parasite salivary gland and secreted in tick saliva. It is known that hosts can mount immune responses against ticks and bovine European breeds, and bovine industrial crossbreeds are more susceptible to infestations than are Bos indicus cattle. To identify candidates for the development of novel control strategies for the cattle tick Rhipicephalus (Boophilus) microplus, a salivary gland transcriptome analysis of engorged females fed on susceptible or resistant hosts was performed. Using RNA-Seq, transcriptomes were de novo assembled and produced a total of 235,451 contigs with 93.3% transcriptome completeness. Differential expression analysis identified 137 sequences as differentially expressed genes (DEGs) between ticks raised on tick-susceptible or tick-resistant cattle. DEGs predicted to be secreted proteins include innexins, which are transmembrane proteins that form gap junction channels; the transporters Na⁺/dicarboxylate, Na⁺/tricarboxylate, and phosphate transporter and a putative monocarboxylate transporter; a phosphoinositol 4-phosphate adaptor protein; a cysteine-rich protein containing a trypsin inhibitor-like (TIL) domain; a putative defense protein 3 containing a reeler domain; and an F-actin-uncapping protein LRRC16A with a CARMIL_C domain; these genes were upregulated in ticks fed on tick-susceptible cattle. DEGs predicted to be non-secreted proteins included a small heat shock protein and the negative elongation factor B-like, both acting in a coordinated manner to increase HSP transcript levels in the salivary glands of the ticks fed on tick-susceptible cattle; the 26S protease regulatory subunit 6B and another chaperone with similarity to calnexin, also upregulated in ticks fed on tick-susceptible cattle; an EF-hand calcium binding protein and a serine carboxypeptidase (SCP), both involved in the blood coagulation cascade and upregulated in ticks fed on tick-susceptible cattle; and two ribosomal proteins, the 60S acidic ribosomal protein P2 and the 60S ribosomal protein L19. These results help to characterize cattle tick salivary gland gene expression in tick-susceptible and tick-resistant hosts and suggest new putative targets for the control of tick infestations, as those genes involved in the mechanism of stress response during blood feeding.

Unraveling oxidative stress response in the cestode parasite Echinococcus granulosus

Cystic hydatid disease (CHD) is a worldwide neglected zoonotic disease caused by Echinococcus granulosus. The parasite is well adapted to its host by producing protective molecules that modulate host immune response. An unexplored issue associated with the parasite's persistence in its host is how the organism can survive the oxidative stress resulting from parasite endogenous metabolism and host defenses. Here, we used hydrogen peroxide (H₂O₂) to induce oxidative stress in E. granulosus protoescoleces (PSCs) to identify molecular pathways and antioxidant responses during H₂O₂ exposure. Using proteomics, we identified 550 unique proteins; including 474 in H₂O₂-exposed PSCs (H-PSCs) samples and 515 in non-exposed PSCs (C-PSCs) samples. Larger amounts of antioxidant proteins, including GSTs and novel carbonyl detoxifying enzymes, such as aldo-keto reductase and carbonyl reductase, were detected after H₂O₂ exposure. Increased concentrations of caspase-3 and cathepsin-D proteases and components of the 26S proteasome were also detected in H-PSCs. Reduction of lamin-B and other caspase-substrate, such as filamin, in H-PSCs suggested that molecular events related to early apoptosis were also induced. We present data that describe proteins expressed in response to oxidative stress in a metazoan parasite, including novel antioxidant enzymes and targets with potential application to treatment and prevention of CHD.

Proteomic analysis of excretory-secretory products from young adults of Angiostrongylus cantonensis

BACKGROUND

Angiostrongyliasis is caused by the nematode Angiostrongylus cantonensis and can lead to eosinophilic meningitis and meningoencephalitis in humans. The young adult worms play central pathogenic roles in the central nervous system (CNS); however, the underlying mechanism is unclear. Excretory-secretory products (ESPs) are good investigation targets for studying the relationship between a host and its parasite.

OBJECTIVES

We aimed to profile, identify, and characterise the proteins in the ESPs of A. cantonensis young adults.

METHODS

The ESPs of young adult worms were collected from culture medium after incubation ranging from 24 to 96 h. Proteomic and bioinformatics analyses were performed to characterise the ESPs.

FINDINGS

A total of 51 spots were identified, and the highly expressed proteins included two protein disulphide isomerases, one calreticulin, and three uncharacterised proteins. Subsequently, approximately 254 proteins were identified in the ESPs of A. cantonensis young adults via liquid chromatography-mass spectrometry (LC-MS/MS) analysis, and these were further classified according to their characteristics and biological functions. Finally, we identified the immunoreactive proteins from a reference map of ESPs from A. cantonensis young adults. Approximately eight proteins were identified, including a protein disulphide isomerase, a putative aspartic protease, annexin, and five uncharacterised proteins. The study established and identified protein reference maps for the ESPs of A. cantonensis young adults.

MAIN CONCLUSIONS

The identified proteins may be potential targets for the development of diagnostic or therapeutic agents for human angiostrongyliasis.

Cysteine proteases as digestive enzymes in parasitic helminths

We briefly review cysteine proteases (orthologs of mammalian cathepsins B, L, F, and C) that are expressed in flatworm and nematode parasites. Emphasis is placed on enzyme activities that have been functionally characterized, are associated with the parasite gut, and putatively contribute to degrading host proteins to absorbable nutrients [1–4]. Often, gut proteases are expressed as multigene families, as is the case with Fasciola [5] and Haemonchus [6], presumably expanding the range of substrates that can be degraded, not least during parasite migration through host tissues [5]. The application of the free-living planarian and Caenorhabditis elegans as investigative models for parasite cysteine proteases is discussed. Finally, because of their central nutritive contribution, targeting the component gut proteases with small-molecule chemical inhibitors and understanding their utility as vaccine candidates are active areas of research [7].

Heterologous expression of three antigenic proteins from Angiostrongylus cantonensis: ES-7, Lec-5, and 14-3-3 in mammalian cells

Angiostrongylus cantonensis is a parasitic nematode and the main causative agent of human cerebral eosinophilic meningoencephalitis (EoM). A definitive diagnosis of EoM usually requires serologic or molecular analysis of the patient's clinical sample. Currently, a 31 kDa antigen is used in immunological tests for this purpose, however as a crude antigen preparation it may present cross-reactivity with other helminthic infections, especially echinococcosis. Heterologous expression studies using prokaryotic systems failed on producing antigenic proteins. The aim of this study was to express and purify three recombinant glycoproteins representing A. cantonensis antigens: ES-7, Lec-5, and 14-3-3, in Chinese hamster ovary (CHO) cells and ES-7 in human embryonic kidney (HEK) cells to develop a source of specific antigens to be used in the diagnosis of angiostrongyliasis. The potential diagnostic value of these three proteins was subsequently characterized in one- and two-dimensional electrophoresis and Western blot to dot blot analyses, with Angiostrongylus-positive sera, normal human sera (NHS), and a pool of Echinococcus-positive sera (included as a specificity control) used for detection. In addition, recognition of these three proteins following treatment with N-glycosidase F was examined. The ES-7 proteins that were expressed in HEK and CHO cells, and the Lec-5 protein that was expressed in CHO cells, were specifically recognized by A. cantonensis-positive sera in the 2D electrophoresis analysis. This recognition was shown to be dependent on the presence of glycidic portions, making mammalian cells a very promising source of heterologous expression antigenic proteins from Angiostrongylus.

Tissue-specific transcriptomes of Anisakis simplex (sensu stricto) and Anisakis pegreffii reveal potential molecular mechanisms involved in pathogenicity

Background

Larval stages of the sibling species of parasitic nematodes Anisakis simplex (sensu stricto) (s.s.) (AS) and Anisakis pegreffii (AP) are responsible for a fish-borne zoonosis, known as anisakiasis, that humans aquire via the ingestion of raw or undercooked infected fish or fish-based products. These two species differ in geographical distribution, genetic background and peculiar traits involved in pathogenicity. However, thus far little is known of key molecules potentially involved in host-parasite interactions. Here, high-throughput RNA-Seq and bioinformatics analyses of sequence data were applied to the characterization of the whole sets of transcripts expressed by infective larvae of AS and AP, as well as of their pharyngeal tissues, in a bid to identify transcripts potentially involved in tissue invasion and host-pathogen interplay.

Results

Approximately 34,000,000 single-end reads were generated from cDNA libraries for each species. Transcripts identified in AS and AP encoded 19,403 and 10,424 putative peptides, respectively, and were classified based on homology searches, protein motifs, gene ontology and biological pathway mapping. Differential gene expression analysis yielded 226 and 339 transcripts upregulated in the pharyngeal regions of AS and AP, respectively, compared with their corresponding whole-larvae datasets. These included proteolytic enzymes, molecules encoding anesthetics, inhibitors of primary hemostasis and virulence factors, anticoagulants and immunomodulatory peptides.

Conclusions

This work provides the scientific community with a list of key transcripts expressed by AS and AP pharyngeal tissues and corresponding annotation information which represents a ready-to-use resource for future functional studies of biological pathways specifically involved in host-parasite interplay.

Electronic supplementary material

The online version of this article (10.1186/s13071-017-2585-7) contains supplementary material, which is available to authorized users.

Stimulation of IL-1β and IL-6 through NF-κB and sonic hedgehog-dependent pathways in mouse astrocytes by excretory/secretory products of fifth-stage larval Angiostrongylus cantonensis

BACKGROUND

Angiostrongylus cantonensis is an important causative agent of eosinophilic meningitis and eosinophilic meningoencephalitis in humans. Previous studies have shown that the Sonic hedgehog (Shh) signaling pathway may reduce cell apoptosis by inhibiting oxidative stress in A. cantonensis infection. In this study, we investigated the relationship between cytokine secretion and Shh pathway activation after treatment with excretory/secretory products (ESP) of fifth-stage larval A. cantonensis (L5).

RESULTS

The results showed that IL-1β and IL-6 levels in mouse astrocytes were increased. Moreover, ESP stimulated the protein expression of Shh pathway molecules, including Shh, Ptch, Smo and Gli-1, and induced IL-1β and IL-6 secretion. The transcription factor nuclear factor-κB (NF-κB) plays an important role in inflammation, and it regulates the expression of proinflammatory genes, including cytokines and chemokines, such as IL-1β and TNF-α. After ESP treatment, NF-κB induced IL-1β and IL-6 secretion in astrocytes by activating the Shh signaling pathway.

CONCLUSIONS

Overall, the data presented in this study showed that ESP of fifth-stage larval A. cantonensis stimulates astrocyte activation and cytokine generation through NF-κB and the Shh signaling pathway.

Anti-apoptotic effects of Sonic hedgehog signalling through oxidative stress reduction in astrocytes co-cultured with excretory-secretory products of larval Angiostrongylus cantonensis

Angiostrongylus cantonensis, the rat lungworm, is an important aetiologic agent of eosinophilic meningitis and meningoencephalitis in humans. Co-culturing astrocytes with soluble antigens of A. cantonensis activated the Sonic hedgehog (Shh) signalling pathway and inhibited the apoptosis of astrocytes via the activation of Bcl-2. This study was conducted to determine the roles of the Shh signalling pathway, apoptosis, and oxidative stress in astrocytes after treatment with excretory-secretory products (ESP) from A. cantonensis fifth-stage larvae. Although astrocyte viability was significantly decreased after ESP treatment, the expression of Shh signalling pathway related proteins (Shh, Ptch-1 and Gli-1) was significantly increased. However, apoptosis in astrocytes was significantly decreased after activation of the Shh signalling pathway. Moreover, superoxide and hydrogen superoxide levels in astrocytes were significantly reduced after the activation of Shh pathway signalling due to increasing levels of the antioxidants catalase and superoxide dismutase. These findings indicate that the anti-apoptotic effects of the Shh signalling pathway in the astrocytes of mice infected with A. cantonensis are due to reduced levels of oxidative stress caused by the activation of antioxidants.

Perusal of parasitic nematode 'omics in the post-genomic era

The advent of high-throughput, next-generation sequencing methods combined with advances in computational biology and bioinformatics have greatly accelerated discovery within biomedical research. This "post-genomics" era has ushered in powerful approaches allowing one to quantify RNA transcript and protein abundance for every gene in the genome - often for multiple conditions. Herein, we chronicle how the post-genomics era has advanced our overall understanding of parasitic nematodes through transcriptomics and proteomics and highlight some of the important advances made in each major nematode clade. We primarily focus on organisms relevant to human health, given that nematode infections significantly impact disability-adjusted life years (DALY) scores within the developing world, but we also discuss organisms of veterinary importance as well as those used as laboratory models. As such, we envision that this review will serve as a comprehensive resource for those seeking a better understanding of basic parasitic nematode biology as well as those interested in targets for vaccination and pharmacological intervention.

Proteomic Analysis of the Excretory and Secretory Proteins of Haemonchus contortus (HcESP) Binding to Goat PBMCs In Vivo Revealed Stage-Specific Binding Profiles

Haemonchus contortus is a parasitic gastrointestinal nematode, and its excretory and secretory products (HcESPs) interact extensively with the host cells. In this study, we report the interaction of proteins from HcESPs at different developmental stages to goat peripheral blood mononuclear cells (PBMCs) in vivo using liquid chromatography-tandem mass spectrometry. A total of 407 HcESPs that interacted with goat PBMCs at different time points were identified from a H. contortus protein database using SEQUEST searches. The L4 and L5 stages of H. contortus represented a higher proportion of the identified proteins compared with the early and late adult stages. Both stage-specific interacting proteins and proteins that were common to multiple stages were identified. Forty-seven interacting proteins were shared among all stages. The gene ontology (GO) distributions of the identified goat PBMC-interacting proteins were nearly identical among all developmental stages, with high representation of binding and catalytic activity. Cellular, metabolic and single-organism processes were also annotated as major biological processes, but interestingly, more proteins were annotated as localization processes at the L5 stage than at the L4 and adult stages. Based on the clustering of homologous proteins, we improved the functional annotations of un-annotated proteins identified at different developmental stages. Some unnamed H. contortus ATP-binding cassette proteins, including ADP-ribosylation factor and P-glycoprotein-9, were identified by STRING protein clustering analysis.

Angiostrongylus cantonensis: a review of its distribution, molecular biology and clinical significance as a human pathogen

Angiostrongylus cantonensis is a metastrongyloid nematode found widely in the Asia-Pacific region, and the aetiological agent of angiostrongyliasis; a disease characterized by eosinophilic meningitis. Rattus rats are definitive hosts of A. cantonensis, while intermediate hosts include terrestrial and aquatic molluscs. Humans are dead-end hosts that usually become infected upon ingestion of infected molluscs. A presumptive diagnosis is often made based on clinical features, a history of mollusc consumption, eosinophilic pleocytosis in cerebral spinal fluid, and advanced imaging such as computed tomography. Serological tests are available for angiostrongyliasis, though many tests are still under development. While there is no treatment consensus, therapy often includes a combination of anthelmintics and corticosteroids. Angiostrongyliasis is relatively rare, but is often associated with morbidity and sometimes mortality. Recent reports suggest the parasites' range is increasing, leading to fatalities in regions previously considered Angiostrongylus-free, and sometimes, delayed diagnosis in newly invaded regions. Increased awareness of angiostrongyliasis would facilitate rapid diagnosis and improved clinical outcomes. This paper summarizes knowledge on the parasites' life cycle, clinical aspects and epidemiology. The molecular biology of Angiostrongylus spp. is also discussed. Attention is paid to the significance of angiostrongyliasis in Australia, given the recent severe cases reported from the Sydney region.

Development of a Luminex Bead Based Assay for Diagnosis of Toxocariasis Using Recombinant Antigens Tc-CTL-1 and Tc-TES-26

The clinical spectrum of human disease caused by the roundworms Toxocara canis and Toxocara cati ranges from visceral and ocular larva migrans to covert toxocariasis. The parasite is not typically recovered in affected tissues, so detection of parasite-specific antibodies is usually necessary for establishing a diagnosis. The most reliable immunodiagnostic methods use the Toxocara excretory-secretory antigens (TES-Ag) in ELISA formats to detect Toxocara-specific antibodies. To eliminate the need for native parasite materials, we identified and purified immunodiagnostic antigens using 2D gel electrophoresis followed by electrospray ionization mass spectrometry. Three predominant immunoreactive proteins were found in the TES; all three had been previously described in the literature: Tc-CTL-1, Tc-TES-26, and Tc-MUC-3. We generated Escherichia coli expressed recombinant proteins for evaluation in Luminex based immunoassays. We were unable to produce a functional assay with the Tc-MUC-3 recombinant protein. Tc-CTL-1 and Tc-TES-26 were successfully coupled and tested using defined serum batteries. The use of both proteins together generated better results than if the proteins were used individually. The sensitivity and specificity of the assay for detecting visceral larval migrans using Tc-CTL-1 plus Tc-TES-26 was 99% and 94%, respectively; the sensitivity for detecting ocular larval migrans was 64%. The combined performance of the new assay was superior to the currently available EIA and could potentially be employed to replace current assays that rely on native TES-Ag.

Proteomic analysis identification of antigenic proteins in Gnathostoma spinigerum larvae

Gnathostoma spinigerum is the causative agent of human gnathostomiasis. The advanced third stage larva (AL3) of this nematode can migrate into the subcutaneous tissues, including vital organs, often producing severe pathological effects. This study performed immuno-proteomic analysis of antigenic spots, derived from G. spinigerum advanced third stage larva (GSAL3) and recognized by human gnathostomiasis sera, using two-dimensional (2-DE) gel electrophoresis based-liquid chromatography/tandem mass spectrometry (LC/MS-MS), and followed by the aid of a database search. The crude GSAL3 extract was fractionated using IPG strips (pH 3-11NL) and followed by SDS-PAGE in the second dimension. Each gel was stained with colloidal Coomassie blue or was electro-transferred onto a nitrocellulose membrane and probed with gnathostomiasis human sera by immunoblotting. Individual Coomassie-stained protein spots corresponding to the antigenic spots recognized by immunoblotting were excised and processed using LC/MS-MS. Of the 93 antigenic spots excised, 87 were identified by LC/MS-MS. Twenty-seven protein types were found, the most abundant being Ascaris suum37. Six spots showed good quality spectra, but could not be identified. This appears to be the first attempt to characterize antigenic proteins from GSAL3 using a proteomic approach. Immuno-proteomics shows promise to assist the search for candidate proteins for diagnosis and vaccine/drug design and may provide better understand of the host-parasite relationship in human gnathostomiasis.

Draft genome of neurotropic nematode parasite Angiostrongylus cantonensis, causative agent of human eosinophilic meningitis

Angiostrongylus cantonensis is a bursate nematode parasite that causes eosinophilic meningitis (or meningoencephalitis) in humans in many parts of the world. The genomic data from A. cantonensis will form a useful resource for comparative genomic and chemogenomic studies to aid the development of diagnostics and therapeutics. We have sequenced, assembled and annotated the genome of A. cantonensis. The genome size is estimated to be ∼260 Mb, with 17,280 genomic scaffolds, 91X coverage, 81.45% for complete and 93.95% for partial score based on CEGMA analysis of genome completeness. The number of predicted genes of ≥300 bp was 17,482. A total of 7737 predicted protein-coding genes of ≥50 amino acids were identified in the assembled genome. Among the proteins of known function, kinases are the most abundant followed by transferases. The draft genome contains 34 excretory-secretory proteins (ES), a minimum of 44 Nematode Astacin (NAS) metalloproteases, 12 Homeobox (HOX) genes, and 30 neurotransmitters. The assembled genome size (260 Mb) is larger than those of Pristionchus pacificus, Caenorhabditis elegans, Necator americanus, Caenorhabditis briggsae, Trichinella spiralis, Brugia malayi and Loa loa, but smaller than Haemonchus contortus and Ascaris suum. The repeat content (25%) is similar to H. contortus. The GC content (41.17%) is lower compared to P. pacificus (42.7%) and H. contortus (43.1%) but higher compared to C. briggsae (37.69%), A. suum (37.9%) and N. americanus (40.2%) while the scaffold N50 is 42,191. This draft genome will facilitate the understanding of many unresolved issues on the parasite and the disorder it causes.

Activation of Sonic Hedgehog Leads to Survival Enhancement of Astrocytes via the GRP78-Dependent Pathway in Mice Infected with Angiostrongylus cantonensis

Angiostrongylus cantonensis infection may cause elevation of ROS and antioxidants in the CSF of infected mice. Astrocytes may protect the surrounding neurons from oxidative stress-induced cell death by secreting Sonic hedgehog (Shh) via the PI3-K/AKT/Bcl-2 pathway. This study was conducted to determine the role of the Shh signaling pathway in A. cantonensis-infected BABL/c mice by coculturing astrocytes with living fifth-stage larvae or soluble antigens. The Shh pathway was activated with corresponding increases in the level of the Shh. Glial fibrillary acidic protein (GFAP) and Shh were increased in astrocyte cocultured with living fifth-stage larvae or soluble antigens. The survival of astrocytes pretreated with Shh was significantly elevated in cocultures with the antigens but reduced by its inhibitor cyclopamine. The expression of GRP78 and Bcl-2 was significantly higher in astrocytes pretreated with recombinant Shh. These findings suggest that the expression of Shh may inhibit cell death by activating Bcl-2 through a GRP78-dependent pathway.

Secreted proteomes of different developmental stages of the gastrointestinal nematode Nippostrongylus brasiliensis

Hookworms infect more than 700 million people worldwide and cause more morbidity than most other human parasitic infections. Nippostrongylus brasiliensis (the rat hookworm) has been used as an experimental model for human hookworm because of its similar life cycle and ease of maintenance in laboratory rodents. Adult N. brasiliensis, like the human hookworm, lives in the intestine of the host and releases excretory/secretory products (ESP), which represent the major host-parasite interface. We performed a comparative proteomic analysis of infective larval (L3) and adult worm stages of N. brasiliensis to gain insights into the molecular bases of host-parasite relationships and determine whether N. brasiliensis could indeed serve as an appropriate model for studying human hookworm infections. Proteomic data were matched to a transcriptomic database assembled from 245,874,892 Illumina reads from different developmental stages (eggs, L3, L4, and adult) of N. brasiliensis yielding∼18,426 unigenes with 39,063 possible isoform transcripts. From this analysis, 313 proteins were identified from ESPs by LC-MS/MS-52 in the L3 and 261 in the adult worm. Most of the proteins identified in the study were stage-specific (only 13 proteins were shared by both stages); in particular, two families of proteins-astacin metalloproteases and CAP-domain containing SCP/TAPS-were highly represented in both L3 and adult ESP. These protein families are present in most nematode groups, and where studied, appear to play roles in larval migration and evasion of the host's immune response. Phylogenetic analyses of defined protein families and global gene similarity analyses showed that N. brasiliensis has a greater degree of conservation with human hookworm than other model nematodes examined. These findings validate the use of N. brasiliensis as a suitable parasite for the study of human hookworm infections in a tractable animal model.

A 24-48 h fed Amblyomma americanum tick saliva immuno-proteome

BACKGROUND

Multiple tick saliva proteins, the majority of which are unknown, confer tick resistance in repeatedly infested animals. The objective of this study was to identify the 24-48 h fed Amblyomma americanum tick saliva immuno-proteome. The 24-48 h tick-feeding phase is critical to tick parasitism as it precedes important events in tick biology, blood meal feeding and disease agent transmission. Fed male, 24 and 96 h fed female phage display cDNA expression libraries were biopanned using rabbit antibodies to 24 and 48 h fed A. americanum female tick saliva proteins. Biopanned immuno-cDNA libraries were subjected to next generation sequencing, de novo assembly, and bioinformatic analysis.

RESULTS

More than 800 transcripts that code for 24-48 h fed A. americanum immuno-proteins are described. Of the 895 immuno-proteins, 52% (464/895) were provisionally identified based on matches in GenBank. Of these, ~19% (86/464) show high level of identity to other tick hypothetical proteins, and the rest include putative proteases (serine, cysteine, leukotriene A-4 hydrolase, carboxypeptidases, and metalloproteases), protease inhibitors (serine and cysteine protease inhibitors, tick carboxypeptidase inhibitor), and transporters and/or ligand binding proteins (histamine binding/lipocalin, fatty acid binding, calreticulin, hemelipoprotein, IgG binding protein, ferritin, insulin-like growth factor binding proteins, and evasin). Others include enzymes (glutathione transferase, cytochrome oxidase, protein disulfide isomerase), ribosomal proteins, and those of miscellaneous functions (histamine release factor, selenoproteins, tetraspanin, defensin, heat shock proteins).

CONCLUSIONS

Data here demonstrate that A. americanum secretes a complex cocktail of immunogenic tick saliva proteins during the first 24-48 h of feeding. Of significance, previously validated immunogenic tick saliva proteins including AV422 protein, calreticulin, histamine release factor, histamine binding/lipocalins, selenoproteins, and paramyosin were identified in this screen, supporting the specificity of the approach in this study. While descriptive, this study opens opportunities for in-depth tick feeding physiology studies.

Proteomic profile of Ortleppascaris sp.: A helminth parasite of Rhinella marina in the Amazonian region

•

We have characterized somatic proteins of a helminth parasite of a synanthropic amphibian from Amazonian region.

•

As37, an immunoreactive antigen considered a target for antihelminthic vaccines was found.

•

We found virulence factors which are evolutionarily conserved and are potential factors for anti-parasitic interventions.

•

This study brings a new approach for host–parasite research by using a amphibian as an animal model.

Ortleppascaris sp. is a helminth that, in its larval stage, infects the liver parenchyma of the amphibian Rhinella marina, resulting in severe physiological and pathological changes. This study used a proteomic approach to determine the overall profile of proteins expressed in a somatic extract from the nematodes to investigate the relationship between the parasite and its host. A total of 60 abundant proteins were selected from the two-dimensional electrophoresis, identified by peptide mass fingerprinting, and grouped based on their Gene Ontology by the biological processes in which they are potentially involved. Important helminthic derivatives, such as the immunoreactive As37 antigen, guanylyl cyclases, proteolytic enzymes, and other proteins conserved among different parasites, were identified through homology. This study represents a new approach to helminth-related proteomic studies using an amphibian animal model. Furthermore, this study identified protein markers that are important to the host–parasite relationship and the viability, development, infectivity, and virulence of helminths.

High throughput sequencing of the Angiostrongylus cantonensis genome: a parasite spreading worldwide

Angiostrongylus cantonensis is a parasitic nematode of rodents and a leading aetiological agent of eosinophilic meningitis in humans. Definitive diagnosis is difficult, often relying on immunodiagnostic methods which utilize crude antigens. New immunodiagnostic methods based on recombinant proteins are being developed, and ideally these methods would be made available worldwide. Identification of diagnostic targets, as well as studies on the biology of the parasite, are limited by a lack of molecular information on Angiostrongylus spp. available in databases. In this study we present data collected from DNA random high-throughput sequencing together with proteomic analyses and a cDNA walking methodology to identify and obtain the nucleotide or amino acid sequences of unknown immunoreactive proteins. 28 080 putative ORFs were obtained, of which 3371 had homology to other deposited protein sequences. Using the A. cantonensis genomic sequences, 156 putative ORFs, matching peptide sequences obtained from previous proteomic studies, were considered novel, with no homology to existing sequences. Full-length coding sequences of eight antigenic target proteins were obtained. In this study we generated not only the complete nucleotide sequences of the antigenic protein targets but also a large amount of genomic data which may help facilitate future genomic, proteomic, transcriptomic or metabolomic studies on Angiostrongylus.

Transcriptome profiling of the fifth-stage larvae of Angiostrongylus cantonensis by next-generation sequencing

Angiostrongylus cantonensis is an important zoonotic nematode. It is the causative agent of eosinophilic meningitis and eosinophilic meningoencephalitis in humans. However, information of this parasite at the genomic level is very limited. In the present study, the transcriptomic profiles of the fifth-stage larvae (L5) of A. cantonensis were investigated by next-generation sequencing (NGS). In the NGS database established from the larvae isolated from the brain of Sprague–Dawley rats, 31,487 unique genes with a mean length of 617 nucleotides were assembled. These genes were found to have a 46.08 % significant similarity to Caenorhabditis elegans by BLASTx. They were then compared with the expressed sequence tags of 18 other nematodes, and significant matches of 36.09–59.12 % were found. Among these genes, 3,338 were found to participate in 124 Kyoto Encyclopedia of Genes and Genomes pathways. These pathways included 1,514 metabolisms, 846 genetic information processing, 358 environmental information processing, 264 cellular processes, and 91 organismal systems. Analysis of 30,816 sequences with the gene ontology database indicated that their annotations included 5,656 biological processes (3,364 cellular processes, 3,061 developmental processes, and 3,191 multicellular organismal processes), 7,218 molecular functions (4,597 binding and 3,084 catalytic activities), and 4,719 cellular components (4,459 cell parts and 4,466 cells). Moreover, stress-related genes (112 heat stress and 33 oxidation stress) and genes for proteases (159) were not uncommon. This study is the first NGS-based study to set up a transcriptomic database of A. cantonensis L5. The results provide new insights into the survival, development, and host–parasite interactions of this blood-feeding nematode.

The mRNA level of the galectin-10 of Angiostrongylus cantonensis induced by reactive oxygen stress

Galectin plays an important role in host-parasite interactions. In this study, we identified a novel gene encoding galectin-10 (AcGal-10) from the cDNA library of Angiostrongylus cantonensis and characterized its biological role in the parasite. Sequence and phylogeny analysis showed that AcGal-10 is related to other galectin family members with the conserved loci (H(84)-D(86)-R(88)-V(96)-N(98)-W(105)-E(108)-R(110)). The mRNA level of AcGal-10 was expressed in reactive oxygen stress radicals. We have identified two proteins of A. cantonensis galectin-10 gene, one of which was reported (AcGAL10-W) and the others is AcGAL-10-M. In addition, recombinant AcGal-10 (rAcGal-10) was constructed into the pGEX-4T-1 plasmid, purified, and finally confirmed by SDS-PAGE and LC-MS. Hemagglutination assay showed that the minimum concentration of rAcGAL10-W and rAcGAL10-M required for the hemagglutination of BALB/c mice erythrocyte was 25 μg/mL, and the carbohydrate-binding ability showed no difference between rAcGAL10-W and rAcGAL10-M. The mRNA levels of AcGal-10 were indeed expressed higher after stimulation with H(2)O(2) and recombinant A. cantonensis galectin-10. A mutation of AcGal-10 was also found, but there was no significant difference compared with the wild type. Furthermore, we also confirmed that recombinant AcGal-10 plays a role in the activation of the microglia. In conclusion, the report here showed that AcGal-10 may be an important molecule related to infection of A. cantonensis.

Interface Molecules of Angiostrongylus cantonensis: Their Role in Parasite Survival and Modulation of Host Defenses

Angiostrongylus cantonensis is a nematode parasite that causes eosinophilic meningoencephalitis in humans. Disease presents following the ingestion of third-stage larvae residing in the intermediate mollusk host and disease manifests as an acute inflammation of the meninges characterized by eosinophil infiltrates which release a battery of proinflammatory and cytotoxic agents in response to the pathogen. As a mechanism of neutralizing these host defenses, A. cantonensis expresses different molecules with immunomodulatory properties that are excreted or secreted (ES). In this paper we discuss the role of ES proteins on disease exacerbation and their potential use as therapeutic targets.