Proteomic analysis of Toxocara canis excretory and secretory (TES) proteins

Toxocara canis-originated recombinant C-type lectin improves the disability scores of experimental autoimmune encephalomyelitis in murine in vivo models

BACKGROUND

The recombinant C-type lectin protein (r-CTL) derived from Toxocara canis larvae is thought to play a role in promoting regulatory T cell-dominant immune responses in toxocariasis. This study aimed to highlight the therapeutic potential of the r-CTL protein in improving the disability scores of EAE by enhancing the Foxp3+-CD25+ T cells population.

METHODS

The r-CTL was expressed in prokaryotic systems and purified using Ni-NTA spin columns. Balb/C57 mice were divided into six groups, with EAE induced in four of them, excluding the healthy control group and the group receiving only r-CTL treatment. Group I (n = 10) received r-CTL treatment post EAE induction, Group II (n = 10) underwent EAE induction only, Group III (n = 5) received treatment with E. coli lysate proteins containing E. coli BL21 and plasmid pET32a without r-CTL after EAE induction, Group IV (n = 5) received sterile PBS after EAE induction, Group V (n = 5) served as the healthy control group, and Group VI (n = 5) received only r-CTL treatment.

RESULTS

The study's findings revealed that r-CTL treatment significantly decreased disability scores in EAE-induced mice. There was a notable increase in the population of CD4+, CD25+, FOXP3+ regulatory T cells following r-CTL treatment. The gene expression levels of IL-10, FOXP3, and GATA3 were significantly elevated in the r-CTL treated group, while the expression of T-bet and RORγ genes was reduced. Treatment with r-CTL significantly mitigated cell infiltration and demyelination in both the spinal cord and brain.

CONCLUSION

In conclusion, the observed improvements in disability scores in the EAE mouse model suggest that r-CTL protein could be a potential new treatment approach worth further investigation.

Analysis of Seroreactivity and Seropositivity in Balb/c Mice Experimentally Infected with Toxocara canis Using Two Recombinant (rTc-CTL-1 and rTES-120) Antigens

INTRODUCTION

Toxocarosis in human beings is currently diagnosed by serological assay based on the detection of antibodies against Toxocara antigens. Toxocara canis larvae do not reach the adult stage in paratenic hosts like humans and mice. Therefore experimental infection in mice, which mimics the biology of human infection, might be relevant to get a better understanding of human toxocarosis.

METHODS

Two recombinant antigens viz. rTc-CTL-1 and rTES-120 were developed by expression of respective genes in Escherichia coli. The Balb/c mice were divided into 3 groups; Group I and group II (n = 8 mice each) were infected orally with 100 and 1000 T. canis embryonated eggs, respectively and Group III, mice served as uninfected control mice. The serum samples were obtained from all mice at 0, 7, 14, 28, 45, 60, 90, 120 and 150 days post infection (dpi) were tested by indirect ELISA for detecting seroreactivity to Toxocara and at 28 dpi sera of mice was used for confirming seropositivity of toxocarosis in experimentally infected mice.

RESULTS

The rTc-CTL-1 antigen based ELISA showed the antibody response in both the infected groups were increased from 7 dpi, reached maximum at 28 dpi, then gradually declined but it was maintained up to 150 dpi where as the rTES-120 antigen based ELISA detected antibody only at 28 dpi with a maximum at 60 dpi, then moderately declined but it was observed up to 150 dpi. The antibody response of group II mice were significantly higher than the group I mice throughout the observation period when compared to control group (P < 0.01). Statistical analysis showed a highly significant difference in the antibody response between the group I and group II mice from 14 to 150 dpi with rTc-CTL-1 ELISA and from 28 to 150 dpi with rTES-120 based ELISA (P < 0.01). The seropositivity in mice sera samples at 28 dpi using rTc-CTL-1 based ELISA revealed 87.5% in group I and 100% in group II mice were positive. The rTES-120 ELISA revealed 12.5% in group I and 25% in group II mice were positive. Statistically highly significant difference in the seropositivity between the recombinant antigens (P < 0.01) was observed, but, there was no significant difference between the infected group of mice.

CONCLUSION

It was concluded that rTc-CTL-1 antigen based ELISA detect antibody in early infections compared to rTES-120 ELISA and also the antibody response was directly proportional to the dosage of infective eggs. The diagnostic efficacy of rTc-CTL-1 antigen based ELISA was better when compared to rTES-120 antigen based ELISA.

Proteomic analysis of extracellular vesicles and extracellular vesicle-depleted excretory-secretory products of Toxocara canis and Toxocara cati larval cultures

Toxocara canis and Toxocara cati are parasitic nematodes in the order Ascaridida, which inhabit the small intestines of dogs and cats, respectively, as adults. Although often nonpathogenic as adults, nematodes within this genus are capable of causing widespread disease throughout the host while in a larval stage, during which time larvae migrate throughout the body in a process termed larva migrans. Larvae are also capable of surviving within host tissues in an encysted arrested stage, without immune clearance by the host. The ability of larvae to survive within host tissues during migration and encystment may be attributed to immunomodulatory molecules released by the excretory cells of larvae in excretory-secretory (ES) products. ES products of parasites contain a variety of molecules, including proteins, lipids, and extracellular vesicles (EVs). Toxocara excretory-secretory (TES) products have been studied to some degree, with proteomic analysis of TES proteins described previously; however, investigation of the EVs within TES is lacking, despite the suggested role for these molecules in host interaction and potential immunomodulation. To further characterize the protein cargo within EVs in TES, EVs were isolated from larval cultures of T. canis and T. cati via ultrafiltration, with concurrent collection of EV-depleted TES filtrate for additional study. Isolated EVs and EV-depleted TES from both T. canis and T. cati were submitted for proteomic analysis by liquid chromatography tandem mass spectrometry (LC-MS/MS). Proteomic identification results revealed 140 proteins across all samples, with 16 shared by all samples, and 76 total proteins shared between T. canis and T. cati, present within EVs and EV-depleted TES. There were 17 proteins shared exclusively by EV samples, and 15 were shared exclusively between EV-depleted TES samples. Many shared proteins were associated with the host immune response. Several proteins were specific to either T. canis or T. cati, highlighting the potential use of these proteins as diagnostic tools in the differentiation of etiologic agents in cases of toxocariasis. The results of this study build upon previously reported proteomic evaluations of TES, contributing new information in regards to newly identified proteins, EV protein cargo within TES, and potential immunomodulatory functions of these proteins.

Proteomics analysis reveals the differential protein expression of female and male adult Toxocara canis using Orbitrap Astral analyzer

BACKGROUND

Toxocara canis, the most prevalent helminth in dogs and other canines, is one of the socioeconomically important zoonotic parasites, particularly affecting pediatric and adolescent populations in impoverished communities. However, limited information is available regarding the proteomes of female and male adult T. canis. To address this knowledge gap, we performed a comprehensive proteomic analysis to identify the proteins with differential abundance (PDAs) and gender-specifically expressed proteins between the two sexes adult T. canis.

METHODS

The comparative proteomic analysis was carried out by the Orbitrap mass spectrometry (MS) with asymmetric track lossless (Astral) analyzer. The difference analysis was conducted using t-test and the proteins verification was achieved through parallel reaction monitoring (PRM). The potential biological functions of identified adult T. canis proteins and PDAs were predicted by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. The domain, transcription factor and subcellular localization of the identified proteins and PDAs were analyzed by InterPro, AnimalTFDB 4.0 and Cell-mPLOC 2.0 databases, respectively.

RESULTS

A total of 8565 somatic proteins of adult T. canis were identified. Compared to male adult, 682 up-regulated PDAs and 844 down-regulated PDAs were identified in female adult with P-values < 0.05 and |log2FC| > 1, including 139 proteins exclusively expressed in female and 272 proteins exclusively expressed in male. The GO annotation analysis using all PDAs revealed that the main biological processes, cellular components and molecular functions corresponded to aminoglycan metabolic process, extracellular region and protein tyrosine phosphatase activity, respectively. The KEGG analysis using all PDAs showed that the pathways were mainly associated with adipocytokine signaling pathway, proximal tubule bicarbonate reclamation and PPAR signaling pathway.

CONCLUSIONS

This study reveals the differential protein expression between female and male adult T. canis, providing valuable resource for developing the novel intervention strategies against T. canis infection in humans and animals, especially from the perspective of sexual development and reproduction.

Comparison of extracellular vesicle isolation methods for the study of exosome cargo within Toxocara canis and Toxocara cati excretory secretory (TES) products

Toxocara is a genus of nematodes, which infects a variety of hosts, principally dogs and cats, with potential zoonotic risks to humans. Toxocara spp. larvae are capable of migrating throughout the host tissues, eliciting eosinophilic and granulomatous reactions, while surviving for extended periods of time, unchanged, in the host. It is postulated that larvae are capable of altering the host's immune response through the release of excretory-secretory products, containing both proteins and extracellular vesicles (EVs). The study of EVs has increased exponentially in recent years, largely due to their potential use as a diagnostic tool, and in molecular therapy. To this end, there have been multiple isolation methods described for the study of EVs. Here, we use nanoparticle tracking to compare the yield, size distribution, and % labelling of EV samples acquired through various reported methods, from larval cultures of Toxocara canis and T. cati containing Toxocara excretory-secretory products (TES). The methods tested include ultracentrifugation, polymer precipitation, magnetic immunoprecipitation, size exclusion chromatography, and ultrafiltration. Based on these findings, ultrafiltration produces the best results in terms of yield, expected particle size, and % labelling of sample. Transmission electron microscopy confirmed the presence of EVs with characteristic cup-shaped morphology. These findings can serve as a guide for those investigating EVs, particularly those released from multicellular organisms, such as helminths, for which few comparative analyses have been performed.

Potential roles of Toxocara canis larval excretory secretory molecules in immunomodulation and immune evasion

Toxocara canis larvae invade various tissues of different vertebrate species without developing into adults in paratenic host. The long-term survival of the larvae despite exposure to the well-armed immune response is a notable achievement. The larvae modulate the immune response to help the survival of both the host and the larvae. They skew the immune response to type 2/regulatory phenotype. The outstanding ability of the larvae to modulate the host immune response and to evade the immune arms is attributed to the secretion of Toxocara excretory-secretory products (TESPs). TESPs are complex mixture of differing molecules. The present review deals with the molecular composition of the TESPs, their interaction with the host molecules, their effect on the innate immune response, the receptor recognition, the downstream signals the adaptive immunity and the repair of tissues. This review also addresses the role of TESPs molecules in the immune evasion strategy and the potential effect of the induced immunomodulation in some diseases. Identification of parasite components that influence the nematode-host interactions could enhance understanding the molecular basis of nematode pathogenicity. Furthermore, the identification of helminths molecules with immunomodulatory potential could be used in immunotherapies for some diseases.

Comorbidities involving parasitic diseases: A look at the benefits and complications

Parasitic infections acquired by the population cause substantial morbidity worldwide, with individuals from developing countries being most affected. Some parasites remain in the host for long periods, settling in different organs, manipulating the flow of nutrients and metabolites, and influencing the immune response, favoring their adaptation. The host attempts to counteract the metabolic and immunological alterations and the possible damage caused by infection. These metabolic and immunological changes experienced by the host can influence the progression of other existing morbidities or those that will be acquired in the future. Cancer and metabolic diseases are also frequent causes of morbidity in the world population. The large numbers of individuals affected by cancer and metabolic diseases and the high prevalence of morbidity caused by parasitic diseases favor the development of comorbidity involving these pathologies. This review provides an overview of major advances in research on cancer and metabolic diseases associated with parasitic infections. Information about hosts and parasites such as alterations of the immune response, metabolism and adaptation mechanisms of the parasites, and parasitic molecules with therapeutic potential is provided, as well as the beneficial results or complications related to the comorbidities discussed herein. We emphasize the need to conduct additional studies addressing comorbidities associated with parasitic infections to improve the understanding of the impact of this association on the progression of morbidities, as well as the possibility of the therapeutic use of and therapeutic approaches involving parasites.

Functional Diversity of the Excretory/Secretory Proteins of Nematode Parasites

INTRODUCTION

Parasites release a wide array of protein as excretory and secretory products (ESPs). Irrespective of their mode of propagation, ESPs are found to be secreted or excreted by both naturally occurring and laboratory-cultivated parasites. Mass spectrometry-based approaches have been extensively used to identify and characterize the ESP constituents. ESPs are involved in various cellular activities such as immune modulation, proteolysis, inhibition of proteases and protection of cells against oxidants. Specifically, their role in host immune evasion by down-regulation of pro-inflammatory cytokines and up-regulation of anti-inflammatory cytokines attracts scientific attention. A thorough investigation of functional diversity of ESPs may be helpful in planning control strategies against many parasites.

METHODS

This review focuses on diversity of ES proteins, various approaches to identify them and discusses about the biochemical and functional aspects of such proteins.

RESULTS

The diverse array of proteins secreted or excreted (a, GST-1, acetylcholinesterase, GAPDH) by the parasites are also described emphasizing their role in cellular physiology.

CONCLUSION

Finally, it concludes by citing some of these proteins as potential therapeutic agents against helminth challenge.

Antigenic Proteins from the Excretory-Secretory Products of Toxocara canis Larvae and Evaluation of Their Potential for Immunodiagnostics of Larval Toxocarosis

BACKGROUND

Larval toxocarosis is a zoonosis caused by larvae of Toxocara canis and T. cati, a gastrointestinal nematode of canids and felids, respectively. Diagnosis is usually performed by ELISA IgG using Toxocara excretory-secretory products as an antigen. Due to laboriousness of isolation of the products and subsequent process of standardization of antigenic compounds, routine use of this method is limited and can produce inaccurate diagnostical results. The purpose of this study was to discover new specific antigenic proteins that could be used in routine serological methods of larval toxocarosis.

MATERIALS AND METHODS

Toxocara excretory-secretory products were collected and separated by SDS-PAGE. Proteins from the gel were electro-transferred to a membrane and incubated with mouse sera. Antigenic proteins were analyzed using the liquid chromatography-tandem mass spectrometry approach. Selected proteins were prepared in recombinant form and tested with mice and human sera by ELISA and Western blot.

RESULTS

A total of four recombinant protein antigens were prepared (rTc-TES-26, rTc-ASA, rTc-PDP, and rTc-ASP). They were analyzed by ELISA and Western blot using mice and human sera. For all sera, three of the four recombinant antigens correlated with Toxocara excretory-secretory products in ELISA analysis. By Western blot, the infection was confirmed in all experimentally infected mice and two out of seven human patients.

CONCLUSION

Combination of the presented methods and analyses represents a possible method of effective identification of Toxocara protein antigens for the purpose of routine serodiagnosis.

Excretory/secretory proteins of adult Toxocara canis induce changes in the expression of proteins involved in the NOD1-RIP2-NF-κB pathway and modulate cytokine production in mouse macrophages

Dog roundworm (Toxocara canis) is the major causative agent of toxocarosis, a parasitic disease of both veterinary and medical importance. Knowledge gaps in fundamental and applied aspects hinder the control of this important zoonotic disease. To have a better understanding of Toxocara infection and host immune responses, mouse macrophages were exposed to excretory/secretory (ES) proteins released by adult worms of T. canis in vitro. The messenger RNA transcription and protein expression of nucleotide-binding oligomerization domain-containing protein 1 (NOD1), receptor interacting protein 2 (RIP2) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) in macrophages were analysed using quantitative real-time PCR (qRT-PCR) and Western blot. The levels of tumour necrosis factor alpha (TNF-ɑ), interleukin-1 beta (IL-1β) and IL-6 released by the stimulated macrophages were analysed using enzyme-linked immunosorbent assay. It was found that 20 μg/mL ES proteins of adult T. canis induced the expression of NOD1, RIP2 and NF-κB in mouse macrophages at both transcriptional and translational levels after 9 h of incubation in vitro. Incubation with 20 μg/mL ES proteins also modulated the production of pro-inflammatory cytokines TNF-ɑ, IL-1β and IL-6 by the macrophages. Taken together, ES proteins of adult T. canis appeared to be able to affect the macrophage NOD1-RIP2-NF-κB signalling pathway, which might play a role in regulating the production of proinflammatory cytokines. Further investigation of these aspects should lead to a better understanding of immune recognition of and modulation by Toxocara canis in host animals.

Monitoring of parasitic diseases of dogs

During the study, dogs were diagnosed with the following helminthic diseases: toxocariasis, echinococcosis, uncinariosis, trichuriasis, capillariosis, dipilidiosis, which took the form of mono and mixed invasions. The aim of this study was to identify the intensity of helminth infestation of dogs of different ages and methods of keeping. Materials and methods. Experimental studies were conducted during 2018–2020 on the basis of the laboratory “Innovative technologies and safety and quality of livestock products” and “Veterinary Pharmacy” of the Department of Veterinary Examination, Microbiology, Zoohygiene and Safety and Quality of Livestock Products; epizootology and parasitology of the Faculty of Veterinary Medicine of Sumy National Agrarian University. In cities and villages, faecal samples were taken from dogs, taking into account the method of keeping (tethered or untethered) and their use (office, hunting, decorative, etc.), which were placed in airtight containers, labeled samples and sent to the laboratory for the research. The object of clinical and laboratory research were dogs aged one to seven years, admitted to veterinary clinics in the period from 2018 to 2020, with suspected helminthic diseases. Testing of dogs was performed by collecting medical history and clinical examination. Results. According to the results of the research, it was established that among helminthic diseases during 2018–2020 the following diseases were registered: toxocariasis, cestodes, uncinariosis of dogs. Among the blood-parasitic diseases for the period 2018–2020 were diagnosed with heartworm disease, babesiosis of dogs. Among ectoparathyroidism, the laboratory diagnosed demodectic mange, otodectosis, canine sarcoptosis, and carnivorous syphonepterosis. A total of 513 surveys were conducted in 2018, of which 80 were positive; for 2019–509, of which positive – 58; for 2020 – 488, of which 62 are positive. Conclusions. Intestinal helminthiasis has been found to account for the lowest proportion (11 %) of carnivorous parasitic diseases compared to blood parasitic diseases (19 %) and ectoparasitosis (70 %), but they are of great interest for study because of their significant epidemiological significance and may be the cause of disease in humans. It has been proven that helminthic diseases of dogs run as mixed invasion, and a minority of cases 31.7 % of cases run as mono invasion. Of the total number of patients with helminthic diseases, 73.4 % of the total number of animals were accompanied by other diseases of infectious and non-infectious ethology

Human Toxocariasis: 2010 to 2020 Contributions from Brazilian Researchers

This is a review of the published contributions made by Brazilian researchers between 2010 and 2020 on the natural history of human toxocariasis and the effects of human toxocariasis on nonhuman paratenic hosts.

The production of excretory-secretory molecules from Heligmosomoides polygyrus bakeri fourth stage larvae varies between mixed and single sex cultures

Background

Excretory-secretory (ES) products are crucial in maintaining helminths in the host. Consequently, the proteins of ES are potential vaccine molecules and potential therapeutic agents for autoimmune diseases. Heligmosomoides polygyrus bakeri, a gastrointestinal parasite of mice, is a model of hookworm infection in humans. ES produced by both sexes of H. polygyrus bakeri L4 stage cultured separately shows different immunomodulatory properties than ES obtained when both sexes are cultured together. Accordingly, the objective of this study was to identify and compare the excretory-secretory molecules from single-sex and mixed cultures.

Methods

The composition of ES of male and female L4 stage nematodes in the presence (cultured together) or absence (cultured alone) of the opposite sex was examined. Proteins were identified using mass spectrometry. The functions of identified proteins were explored with Blast2GO.

Results

A total of 258 proteins derived from mixed larval culture in the presence of sex pheromones were identified, 160 proteins from pure female cultures and 172 from pure male cultures. Exposure of nematodes to the sex pheromones results in abundant production of proteins with immunomodulatory properties such as Val proteins, acetylcholinesterases, TGF-β mimic 9 and HpARI. Proteins found only in ES from mixed larval cultures were TGF-β mimics 6 and 7 as well as galectin.

Conclusions

The presence of the opposite sex strongly influences the composition of ES products, probably by chemical (pheromone) communication between individuals. However, examination of the composition of ES from various conditions gives an opportunity for searching for new potentially therapeutic compounds and anthelminthics as well as components of vaccines. Manipulation of the nematode environment might be important for the studies on the immunomodulatory potential of nematodes.

Toxocara canis Differentially Affects Hepatic MicroRNA Expression in Beagle Dogs at Different Stages of Infection

Toxocara canis is a neglected zoonotic parasite, which threatens the health of dogs and humans worldwide. The molecular mechanisms that underlie the progression of T. canis infection remain mostly unknown. MicroRNAs (miRNAs) are small non-coding RNAs that have been identified in T. canis; however, the regulation and role of miRNAs in the host during infection remain incompletely understood. In this study, we determined hepatic miRNA expression at different stages of T. canis infection in beagle dogs. Individual dogs were infected by 300 embryonated T. canis eggs, and their livers were collected at 12 hpi (hours post-infection), 24 hpi, and 36 dpi (days post-infection). The expression profiles of liver miRNAs were determined using RNA-sequencing. Compared to the control groups, 9, 16, and 34 differentially expressed miRNAs (DEmiRNAs) were detected in the livers of infected dogs at the three infection stages, respectively. Among those DEmiRNAs, the novel-294 and cfa-miR-885 were predicted to regulate inflammation-related genes at the initial stage of infection (12 hpi). The cfa-miR-1839 was predicted to regulate the target gene TRIM71, which may influence the development of T. canis larvae at 24 hpi. Moreover, cfa-miR-370 and cfa-miR-133c were associated with immune response at the final stage of infection (36 dpi). Some immunity-related Gene Ontology terms were enriched particularly at 24 hpi. Likewise, Kyoto Encyclopedia of Genes and Genomes pathway analysis showed that many significantly enriched pathways were involved in inflammation and immune responses. The expression level of nine DEmiRNAs was validated using quantitative real-time PCR (qRT-PCR). These results show that miRNAs play critical roles in the pathogenesis of T. canis during the hepatic phase of parasite development. Our data provide fundamental information for further investigation of the roles of miRNAs in the innate/adaptive immune response of dogs infected by T. canis.

Proteomic Insights into the Biology of the Most Important Foodborne Parasites in Europe

Foodborne parasitoses compared with bacterial and viral-caused diseases seem to be neglected, and their unrecognition is a serious issue. Parasitic diseases transmitted by food are currently becoming more common. Constantly changing eating habits, new culinary trends, and easier access to food make foodborne parasites' transmission effortless, and the increase in the diagnosis of foodborne parasitic diseases in noted worldwide. This work presents the applications of numerous proteomic methods into the studies on foodborne parasites and their possible use in targeted diagnostics. Potential directions for the future are also provided.

Proteomic analysis of soluble protein extract of adult Toxocara cati

Toxocara cati is a cat roundworm and the causative agent of toxocariasis as a cosmopolitan zoonotic disease. As no information has been reported so far, identification of T. cati proteins can be useful for the development of new diagnostic strategies. This study was conducted to identify the major proteins in the adult T. cati tegument using bi-dimensional electrophoresis (2-DE) and shotgun proteomics. A total proteins were identified, among them the metabolic enzymes were the largest group, including: Enolase, triose phosphate isomerase, fructose-bisphosphate aldolase, aldehyde dehydrogenase. The other important protein groups recognized in T. cati, belong to the HSP-family, the structure and motor proteins, such as actin. The role of these proteins have been implicated in parasite-host interactions and modulating cellular immune response, immune regulation in evasion mechanisms of the host immune response. Characterizing T. cati adult proteins play a key role not only in host-parasite interactions, but also in the discovery of drug targets, subunit vaccines against toxocariasis, immunodiagnostic kits for toxocariasis and the identification of novel immuno-modulators that can form the next generation of therapeutic possibilities for inflammatory diseases.

Excretory/Secretory Metabolome of the Zoonotic Roundworm Parasite Toxocara canis

Toxocariasis is a zoonotic disease affecting humans that is predominantly caused by Toxocara canis and T. cati, primarily parasites of dogs and cats, respectively. Toxocara generally establishes long-term infections by co-opting its host's physiological processes, while at the same time exploiting the nutritional environment. Adult stage T. canis reside in the gut of the definitive canine host where they employ a suite of strategies to combat intestinal immune responses by actively producing and releasing excretory-secretory products (ESPs). The protein component of T. canis ESPs has been widely studied, but characterisation of the non-protein ESP complement remains neglected. To characterize the secreted metabolome of Toxocara ESPs and to shed light on the parasite's metabolic processes, we profiled the ESPs of T. canis using both gas chromatography (GC) and liquid chromatography (LC) mass spectrometry approaches. We successfully identified 61 small molecules, including 41 polar metabolites, 14 medium-long chain fatty acids (MLCFAs) and six short chain fatty acids (SCFAs). We identified talose, stearic acid and isovalerate as the major compounds belonging to the polar, MLCFA and SCFA chemical classes, respectively. Most of the 61 identified metabolites appear to have been produced by T. canis via three distinct metabolic pathways - fatty acid, amino acid and carbohydrate metabolism. The majority of the identified ESPs have known biological properties, especially as immunomodulators. However, there is limited/no information on the biological roles or applications of 31 ESP biomolecules, suggesting that these may have novel activities that merit further investigation.

Toxocara "omics" and the promises it holds for medicine and veterinary medicine

Toxocariasis is one of the most neglected worldwide zoonoses that is caused by larval nematode parasites of the genus Toxocara, Toxocara canis, and to a lesser extent, Toxocara cati, whose migration mechanism is still largely unknown. Fortunately, some advanced tools have been employed, such as genomics, transcriptomics, and proteomics, to better understand the molecular biology and regulatory mechanisms of Toxocara. Using genomics and transcriptomics, we can identify a large number of genes that participate in the development of Toxocara and the interaction of parasites and their hosts and can predict the functions of unknown genes by comparing them with other relevant species. Using proteomics, we can identify somatic proteins and excretory and secretory (ES) proteins that perform specific biological functions in tissue degradation, pathogen invasion, immune evasion or modulation. These "omics" techniques also can contribute enormously to the development of new drugs, vaccines and diagnostic tools for toxocariasis. In a word, by utilizing "omics", we can better understand the Toxocara and toxocariasis. In this review, we summarized the representative achievements in Toxocara and the interaction between Toxocara spp. and their hosts based on expressed sequence tags (ESTs), microarray gene expression, next-generation sequencing (NGS) technologies and liquid chromatography-tandem mass spectrometry (LC-MS/MS), hoping to better understand the molecular biology of Toxocara, and contribute to new progress in the application areas of new drugs, vaccines and diagnostic tool for toxocariasis in the future.

Serodiagnostic methods for diagnosing larval toxocariasis

Toxocariasis is a human infection primarily caused by larvae of Toxocara canis from dogs, and also by T. cati from cats. Children have a more significant risk of acquiring the infection due to their closer contact with pets, and greater chances of ingesting soil. Diagnosis of toxocariasis is based on clinical, epidemiological, and serological data. Indirect IgG ELISA is a widely used serodiagnostic method for toxocariasis, with native T. canis TES most commonly used as the antigen. Western blots, using the same antigen, can be used to confirm positive ELISA findings to reduce false-positive results. Improvements in Toxocara serodiagnosis include the use of recombinant TES antigens, simpler and more rapid assay formats, and IgG4 subclass detection. Also, incorporation of recombinant T. cati TES protein increases the diagnostic sensitivity. Development of antigen detection tests using polyclonal and monoclonal antibodies, nanobodies, or aptamers can complement the antibody detection assays, and enhance the effectiveness of the serodiagnosis.

Secretome of the carcinogenic helminth Spirocerca lupi reveals specific parasite proteins associated with its different life stages

Spirocerca lupi is a parasitic and carcinogenic nematode of canids distributed in tropical and subtropical regions around the world. The excretion-secretion proteins (PES) of S. lupi have been suggested to play a role in the pathogenesis of its infection. We aimed to identify the PES of different stages of S. lupi and search for proteins that would be useful for diagnostic, therapeutic and vaccination purposes as well as understand their functions. A nano-UPLC mass spectrometry de novo analysis was performed on proteins collected from cultures of S. lupi L3 larvae, L4 females, adult females and adult males from naturally infected hosts. A total of 211 proteins were identified in all cultures. Accordingly, 117, 130, 99 and 116 proteins were detected in L3 larva, L4 females, adult females and adult males, respectively, with a strong correlation in the biological replicates (Pearson coefficients > 0.73). Fourty-four proteins were detected in all developmental stages, 64 were stage-specific and 49 were exclusively identified in L4 females. Cell compartment enrichment analysis revealed that proteins common to all stages were cytoplasmatic (p < 9.x10^-6), whereas L4 unique proteins were in collagen trimers, and macromolecular complexes (p < 0.00001). Functional enrichment analysis of proteins showed significant enrichment in lipid metabolism in L3-unique proteins (p<0.00005), in mannose metabolism and protein de-glycosylation for L4-unique proteins (p < 0.00004), and in phosphorus metabolism in proteins shared by all stages (p <  2.1 x10^-9). Interestingly, annexin 6, associated with cancer in humans, was detected in all life stages, but in a larger abundance in L4 females and adults. These findings indicate that S. lupi establishes complex interactions with its hosts by an arsenal of proteins expressed in different patterns in each life stage which influence the pathogenesis and oncogenesis of S. lupi and may be used as potential targets for diagnostic assays, drug targets or vaccine candidates.

Serum metabolomic alterations in Beagle dogs experimentally infected with Toxocara canis

Background

Toxocara canis, a globally distributed roundworm, can cause debilitating disease in dogs and humans; however, little is known about the metabolomic response of the hosts to T. canis infection. There is an increasing need to understand the metabolic mechanisms underlying the pathogenesis of T. canis infection in dogs. Here, we examined the metabolomic changes in Beagle dogsʼ serum following T. canis infection using LC-MS/MS.

Results

The metabolic profiles of Beagle dogsʼ serum were determined at 12 h, 24 h, 10 d and 36 d after oral infection with 300 infectious T. canis eggs by LC-MS/MS. We tested whether the T. canis-associated differentially abundant metabolites could distinguish the serum of infected dogs from controls, as measured by the area under the receiver operating characteristic (ROC) curve (AUC). The differentially expressed metabolites were further evaluated by principal components analysis and pathway enrichment analysis. A total of 5756 and 5299 ions were detected in ESI+ and ESI− mode, respectively. ROC curve analysis revealed nine and five metabolite markers, at 12 hpi and 24 hpi to 36 dpi, respectively, with potential diagnostic value for toxocariasis. The levels of taurocholate, estradiol, prostaglandins and leukotriene were significantly changed. Primary bile acid biosynthesis pathway, steroid hormone biosynthesis pathway and biosynthesis of unsaturated fatty acids pathway were significantly altered by T. canis infection.

Conclusions

These findings show that T. canis infection can induce several changes in the dog serum metabolome and that the metabolic signature associated with T. canis infection in dogs has potential for toxocariasis diagnosis.

Reactivity of recombinant Toxocara canis TES-30/120 in experimentally infected mice

AIM

While the use of recombinant antigens is being widely investigated in the diagnosis of human toxocariasis, relatively little attention has been given to animal diagnostic models. For this reason, this study aimed to investigate the diagnosis potential of Toxocara canis TES-30 and TES-120 recombinant antigens in mice, the animal model for toxocariasis studies.

METHODS AND RESULTS

Serum samples obtained from mice infected with T. canis or Toxocara cati were tested by indirect ELISA using T. canis TES-30 and TES-120 recombinant antigens produced in Escherichia coli. 90% of the samples reacted with rTES-30, whereas there was almost no reactivity with rTES-120.

CONCLUSION

Despite rTES-120 being a good antigen for diagnosis in humans, it could not reproduce its reactivity in this animal model. As rTES-30 has good reactivity in mice, it is a valuable tool for diagnosis.

High throughput LC-MS/MS-based proteomic analysis of excretory-secretory products from short-term in vitro culture of Haemonchus contortus

Parasitic nematodes of humans, animals and plants have a major, adverse impact on global health and agricultural production worldwide. To cope with their surrounding environment in and the immune attack from the host, excretory-secretory (ES) proteins are released by nematodes to orchestrate or regulate parasite-host interactions. In the present study, we characterised the ES products from short-term (12 h) in vitro culture of different developmental stages/sexes of Haemonchus contortus (one of the most important parasitic nematodes of livestock animals worldwide) using a high throughput tandem mass-spectrometry, underpinned by the most recent genomic dataset. In total, 878 unique proteins from key developmental stages/sexes (third-stage and fourth-stage larvae, and female and male adults) were identified and quantified with high confidence. Bioinformatic analyses showed noteworthy ES protein alterations during the transition from the free-living to the parasitic phase, especially for proteins which are likely involved in nutrient digestion and acquisition as well as parasite-host interactions, such as proteolytic cascade-related peptidases, glycoside hydrolases, C-type lectins and sperm-coating protein/Tpx/antigen 5/pathogenesis related-1/Sc7 (= SCP/TAPS) proteins. Our findings provide an avenue to better explore interactive processes between the host and this highly significant parasitic nematode, to underpin the search for novel drug and vaccine targets. SIGNIFICANCE: The present study represents a comprehensive proteomic analysis of the secretome of key developmental stages/sexes of H. contortus maintained in short-term in vitro culture. High throughput LC-MS/MS analysis of ES products allowed the identification of a large repertoire of proteins (secretome) and the establishment of a new proteomic database for H. contortus. The secretome of H. contortus undergoes substantial changes during the nematode's transition from free-living to parasitic stages, suggesting a constant adaptation to different environments outside of and within the host animal. Understanding the host-parasite relationship at the molecular level could assist significantly in the development of intervention strategies (i.e. novel drugs and vaccines) against H. contortus and related nematodes.

Somatic proteome of Haemonchus contortus

Currently, there is a dearth of proteomic data to underpin fundamental investigations of parasites and parasitism at the molecular level. Here, using a high throughput LC-MS/MS-based approach, we undertook the first reported comprehensive, large-scale proteomic investigation of the barber's pole worm (Haemonchus contortus) - one of the most important parasitic nematodes of livestock animals worldwide. In total, 2487 unique H. contortus proteins representing different developmental stages/sexes (i.e. eggs, L3s and L4s, female (Af) and male (Am) adults) were identified and quantified with high confidence. Bioinformatic analyses of this proteome revealed substantial alterations in protein profiles during the life cycle, particularly in the transition from the free-living to the parasitic phase, and key groups of proteins involved specifically in feeding, digestion, metabolism, development, parasite-host interactions (including immunomodulation), structural remodelling of the body wall and adaptive processes during parasitism. This proteomic data set will facilitate future molecular, biochemical and physiological investigations of H. contortus and related nematodes, and the discovery of novel intervention targets against haemonchosis.

The somatic proteins of Toxocara canis larvae and excretory-secretory products revealed by proteomics

Toxocariasis is a widespread helminth infection of dogs and cats, caused by Toxocara canis and Toxocara cati larvae, respectively. Toxocara spp. can cause zoonotic infections in humans by invading tissues and organs causing pathology. Toxocara spp. larvae release excretory-secretory molecules (TES) into the body of their host that are fundamental to the host-parasite interaction and could be used as targets for novel diagnostics and vaccines. In the present study, we identified 646 T. canis proteins from TES and larval extract using 1D-SDS PAGE followed by mass spectrometry. A wide range of proteins was identified that may play a role both in the induction of the host immune response and host pathology, and in parasite metabolism and survival. Among these proteins there are potential candidates for novel diagnostics and vaccines for dogs and cats toxocariases.