Molecular cloning and characterisation of in vitro immune response against astacin-like metalloprotease Ace-MTP-2 from Ancylostoma ceylanicum

Salmon louse labial gland enzymes: implications for host settlement and immune modulation

Salmon louse (Lepeophtheirus salmonis) is a skin- and blood-feeding ectoparasite, infesting salmonids. While feeding, labial gland proteins from the salmon louse may be deposited on the Atlantic salmon (Salmo salar) skin. Previously characterized labial gland proteins are involved in anti-coagulation and may contribute to inhibiting Atlantic salmon from mounting a sufficient immune response against the ectoparasite. As labial gland proteins seem to be important in the host-parasite interaction, we have, therefore, identified and characterized ten enzymes localized to the labial gland. They are a large group of astacins named L. salmonis labial gland astacin 1-8 (LsLGA 1-8), one serine protease named L. salmonis labial gland serine protease 1 (LsLGSP1), and one apyrase named L. salmonis labial gland apyrase 1 (LsLGAp1). Protein domain predictions showed that LsLGA proteins all have N-terminal ShK domains, which may bind to potassium channels targeting the astacins to its substrate. LsLGA1 and -4 are, in addition, expressed in another gland type, whose secrete also meets the host-parasite interface. This suggests that LsLGA proteins may have an anti-microbial function and may prevent secondary infections in the wounds. LsLGAp1 is predicted to hydrolyze ATP or AMP and is, thereby, suggested to have an immune dampening function. In a knockdown study targeting LsLGSP1, a significant increase in IL-8 and MMP13 at the skin infestation site was seen under LsLGSP1 knockdown salmon louse compared to the control, suggesting that LsLGSP1 may have an anti-inflammatory effect. Moreover, most of the identified labial gland proteins are expressed in mature copepodids prior to host settlement, are not regulated by starvation, and are expressed at similar or higher levels in lice infesting the salmon louse-resistant pink salmon (Oncorhynchus gorbuscha). This study, thereby, emphasizes the importance of labial gland proteins for host settlement and their immune dampening function. This work can further contribute to anti-salmon louse treatment such as vaccine development, functional feed, or gene-edited salmon louse-resistant Atlantic salmon.

Hookworms dynamically respond to loss of Type 2 immune pressure

The impact of the host immune environment on parasite transcription and fitness is currently unknown. It is widely held that hookworm infections have an immunomodulatory impact on the host, but whether the converse is true remains unclear. Immunity against adult-stage hookworms is largely mediated by Type 2 immune responses driven by the transcription factor Signal Transducer and Activator of Transcription 6 (STAT6). This study investigated whether serial passage of the rodent hookworm Nippostrongylus brasiliensis in STAT6-deficient mice (STAT6 KO) caused changes in parasites over time. After adaptation to STAT6 KO hosts, N. brasiliensis increased their reproductive output, feeding capacity, energy content, and body size. Using an improved N. brasiliensis genome, we found that these physiological changes corresponded with a dramatic shift in the transcriptional landscape, including increased expression of gene pathways associated with egg production, but a decrease in genes encoding neuropeptides, proteases, SCP/TAPS proteins, and transthyretin-like proteins; the latter three categories have been repeatedly observed in hookworm excreted/secreted proteins (ESPs) implicated in immunosuppression. Although transcriptional changes started to appear in the first generation of passage in STAT6 KO hosts for both immature and mature adult stages, downregulation of the genes putatively involved in immunosuppression was only observed after multiple generations in this immunodeficient environment. When STAT6 KO-adapted N. brasiliensis were reintroduced to a naive WT host after up to 26 generations, this progressive change in host-adaptation corresponded to increased production of inflammatory cytokines by the WT host. Surprisingly, however, this single exposure of STAT6 KO-adapted N. brasiliensis to WT hosts resulted in worms that were morphologically and transcriptionally indistinguishable from WT-adapted parasites. This work uncovers remarkable plasticity in the ability of hookworms to adapt to their hosts, which may present a general feature of parasitic nematodes.

Helminth-derived biomacromolecules as therapeutic agents for treating inflammatory and infectious diseases: What lessons do we get from recent findings?

Despite the tremendous progress in healthcare sectors, a number of life-threatening infectious, inflammatory, and autoimmune diseases are continuously challenging mankind throughout the globe. In this context, recent successes in utilizing helminth parasite-derived bioactive macromolecules viz. glycoproteins, enzymes, polysaccharides, lipids/lipoproteins, nucleic acids/nucleotides, and small organic molecules for treating various disorders primarily resulted from inflammation. Among the several parasites that infect humans, helminths (cestodes, nematodes, and trematodes) are known as efficient immune manipulators owing to their explicit ability to modulate and modify the innate and adaptive immune responses of humans. These molecules selectively bind to immune receptors on innate and adaptive immune cells and trigger multiple signaling pathways to elicit anti-inflammatory cytokines, expansion of alternatively activated macrophages, T-helper 2, and immunoregulatory T regulatory cell types to induce an anti-inflammatory milieu. Reduction of pro-inflammatory responses and repair of tissue damage by these anti-inflammatory mediators have been exploited for treating a number of autoimmune, allergic, and metabolic diseases. Herein, the potential and promises of different helminths/helminth-derived products as therapeutic agents in ameliorating immunopathology of different human diseases and their mechanistic insights of function at cell and molecular level alongside the molecular signaling cross-talks have been reviewed by incorporating up-to-date findings achieved in the field.

The Immune Response to Nematode Infection

Nematode infection is a major threat to the health of humans, domestic animals and wildlife. Nematodes vary in their effect on the host and in the mechanisms underlying immunity but the general features are becoming clear. There is considerable variation among individuals in resistance to infection and much of this variation is due to genetic variation in the immune response. The major histocompatibility complex has a strong influence on resistance to infection but other genes are collectively more important. Resistant individuals produce more IgA, eosinophils, IgE and mast cells than susceptible individuals and this is a consequence of stronger type 2 (Th2) immune responses. A variety of factors promote Th2 responses including genetic background, diet, molecules produced by the parasite and the location of the infection. A variety of cells and molecules including proteins, glycolipids and RNA act in concert to promote responses and to regulate the response. Nematodes themselves also modulate the host response and over 20 parasite-derived immunomodulatory molecules have been identified. Different species of nematodes modulate the immune response in different ways and probably use multiple molecules. The reasons for this are unclear and the interactions among immunomodulators have still to be investigated.

Structural and evolutionary insights into astacin metallopeptidases

The astacins are a family of metallopeptidases (MPs) that has been extensively described from animals. They are multidomain extracellular proteins, which have a conserved core architecture encompassing a signal peptide for secretion, a prodomain or prosegment and a zinc-dependent catalytic domain (CD). This constellation is found in the archetypal name-giving digestive enzyme astacin from the European crayfish Astacus astacus. Astacin catalytic domains span ∼200 residues and consist of two subdomains that flank an extended active-site cleft. They share several structural elements including a long zinc-binding consensus sequence (HEXXHXXGXXH) immediately followed by an EXXRXDRD motif, which features a family-specific glutamate. In addition, a downstream SIMHY-motif encompasses a "Met-turn" methionine and a zinc-binding tyrosine. The overall architecture and some structural features of astacin catalytic domains match those of other more distantly related MPs, which together constitute the metzincin clan of metallopeptidases. We further analysed the structures of PRO-, MAM, TRAF, CUB and EGF-like domains, and described their essential molecular determinants. In addition, we investigated the distribution of astacins across kingdoms and their phylogenetic origin. Through extensive sequence searches we found astacin CDs in > 25,000 sequences down the tree of life from humans beyond Metazoa, including Choanoflagellata, Filasterea and Ichtyosporea. We also found < 400 sequences scattered across non-holozoan eukaryotes including some fungi and one virus, as well as in selected taxa of archaea and bacteria that are pathogens or colonizers of animal hosts, but not in plants. Overall, we propose that astacins originate in the root of Holozoa consistent with Darwinian descent and that the latter genes might be the result of horizontal gene transfer from holozoan donors.

The Role of Nuclear Factor Kappa B (NF-κB) in the Immune Response against Parasites

The immune system consists of various cells, organs, and processes that interact in a sophisticated manner to defend against pathogens. Upon initial exposure to an invader, nonspecific mechanisms are raised through the activation of macrophages, monocytes, basophils, mast cells, eosinophils, innate lymphoid cells, or natural killer cells. During the course of an infection, more specific responses develop (adaptive immune responses) whose hallmarks include the expansion of B and T cells that specifically recognize foreign antigens. Cell to cell communication takes place through physical interactions as well as through the release of mediators (cytokines, chemokines) that modify cell activity and control and regulate the immune response. One regulator of cell states is the transcription factor Nuclear Factor kappa B (NF-κB) which mediates responses to various stimuli and is involved in a variety of processes (cell cycle, development, apoptosis, carcinogenesis, innate and adaptive immune responses). It consists of two protein classes with NF-κB1 (p105/50) and NF-κB2 (p100/52) belonging to class I, and RelA (p65), RelB and c-Rel belonging to class II. The active transcription factor consists of a dimer, usually comprised of both class I and class II proteins conjugated to Inhibitor of κB (IκB). Through various stimuli, IκB is phosphorylated and detached, allowing dimer migration to the nucleus and binding of DNA. NF-κB is crucial in regulating the immune response and maintaining a balance between suppression, effective response, and immunopathologies. Parasites are a diverse group of organisms comprised of three major groups: protozoa, helminths, and ectoparasites. Each group induces distinct effector immune mechanisms and is susceptible to different types of immune responses (Th₁, Th₂, Th₁₇). This review describes the role of NF-κB and its activity during parasite infections and its contribution to inducing protective responses or immunopathologies.

Hookworm infections: Reappraising the evidence for a role of Neutrophils in light of NETosis

In Hookworm infection, neutrophils have long had the image of the villain, being recruited to the site of larval migration because of damage but participating themselves in tissue injury. With recent developments in neutrophil biology, there is an increasing body of evidence for the role of neutrophils as effector cells in hookworm immunity. In particular, their ability to release extracellular traps, or neutrophil extracellular traps (NETs), confer neutrophils a larvicidal activity. Here, we review recent evidence in this nascent field and discuss the avenue for future research on NETs/hookworm interactions.

Insights into the functional expansion of the astacin peptidase family in parasitic helminths

Helminths secrete a plethora of proteins involved in parasitism-related processes such as tissue penetration, migration, feeding and immunoregulation. Astacins, a family of zinc metalloproteases belonging to the peptidase family M12, are one of the most abundantly represented protein families in the secretomes of helminths. Despite their involvement in virulence, very few studies have addressed the role of this loosely defined protein group in parasitic helminths. Herein, we have analysed the predicted proteomes from 154 helminth species and confirmed the expansion of the astacin family in several nematode taxa. The astacin domain associated with up to 110 other domains into 145 unique domain architectures, where CUB and ShK constitute the principal and nearly independent bi-domain frameworks. The presence of co-existing domains suggests promiscuous adaptable functions to several roles. These activities could be related either to substrate specificity or to higher-order functions, such as anti-angiogenesis and immunomodulation, where the astacin domain would play an accessory role. Furthermore, some phylogenetically restricted mutations in the astacin domain affected residues located at the active cleft and binding sub-pockets, suggesting adaptation to different substrate specificities. Altogether, these findings suggest the astacin domain is a highly adaptable module that fulfils multiple proteolytic needs of the parasitic lifestyle. This study contributes to the understanding of helminth-secreted astacins and, ultimately, provides the foundation to guide future investigations about the role of this diverse family of proteins in host-parasite interactions.

Immunoproteomic Analysis of Dirofilaria repens Microfilariae and Adult Parasite Stages

Dirofilariarepens is a parasitic nematode causing a vector-borne zoonotic infection (dirofilariosis), considered an emerging problem in human and veterinary medicine. Currently, diagnosis is based on the detection of the adult parasite and microfilariae in the host tissues. However, the efficacy of tests relying on microfilariae detection is limited by microfilariae periodic occurrence. Therefore, a new reliable and affordable serological diagnostic method is needed. Better characteristic of the parasite biology and its interaction with host immune system should help to achieve this goal. This study analyzes adult and microfilariae proteomes, and the use of one-dimensional electrophoresis (1-DE) and two-dimensional electrophoresis (2-DE) proteomics, immunoproteomics, and LC-MS/MS mass spectrometry allowed us to identify 316 potentially immunogenic proteins (75 belong to adult stage, 183 to microfilariae, and 58 are common for both). Classified by their ontology, the proteins showed important similarities and differences between both parasite stages. The most frequently identified proteins are structural, metabolic, and heat shock proteins. Additionally, real-time PCR analysis of some immunogenic targets revealed significant differences between microfilariae and adult life stages. We indicated molecules involved in parasite-host interactions and discussed their importance in parasite biology, which may help to reveal potential diagnostic antigens or select drug and vaccine targets.

Regulation of human THP-1 macrophage polarization by Trichinella spiralis

Trichinella spiralis is a foodborne zoonotic nematode, which causes trichinellosis. During the infection, parasite evades the host immune responses by direct and indirect (through excretory-secretory products) contact with host immune cells. One of the main targets for immunomodulation induced by helminths are macrophages. In this study, we examined whether direct contact of different stages of T. spiralis can affect the polarization of human THP-1 macrophages. Co-culture of adult parasite stage and cells in direct contact without LPS addition had a significant impact on TNFα levels. Interestingly, in settings with the addition of LPS, the levels of IL-1β and TNFα significantly increased in adult parasite and newborn larvae (NBL) but not for muscle larvae (ML). While we tested muscle larvae ESP products to compare its effect with whole ML parasite, we detect an increase of pro-inflammatory cytokines like IL-1β and TNFα in no LPS conditions. Whereas, muscle larvae ESP significantly suppressed the inflammatory response measured by IL-1β, TNFα, and IL-6 levels and anti-inflammatory IL-10 compared to LPS control. Our findings indicate the anti-inflammatory potential of T. spiralis muscle larvae excretory-secretory products and propose signaling pathways which might be engaged in the mechanism of how muscle larvae ESP affect human macrophages.

Soil-Transmitted Helminth Vaccines: Are We Getting Closer?

Parasitic helminths infect over one-fourth of the human population resulting in significant morbidity, and in some cases, death in endemic countries. Despite mass drug administration (MDA) to school-aged children and other control measures, helminth infections are spreading into new areas. Thus, there is a strong rationale for developing anthelminthic vaccines as cost-effective, long-term immunological control strategies, which, unlike MDA, are not haunted by the threat of emerging drug-resistant helminths nor limited by reinfection risk. Advances in vaccinology, immunology, and immunomics include the development of new tools that improve the safety, immunogenicity, and efficacy of vaccines; and some of these tools have been used in the development of helminth vaccines. The development of anthelminthic vaccines is fraught with difficulty. Multiple lifecycle stages exist each presenting stage-specific antigens. Further, helminth parasites are notorious for their ability to dampen down and regulate host immunity. One of the first significant challenges in developing any vaccine is identifying suitable candidate protective antigens. This review explores our current knowledge in lead antigen identification and reports on recent pre-clinical and clinical trials in the context of the soil-transmitted helminths Trichuris, the hookworms and Ascaris. Ultimately, a multivalent anthelminthic vaccine could become an essential tool for achieving the medium-to long-term goal of controlling, or even eliminating helminth infections.

Twenty-five-year research progress in hookworm excretory/secretory products

Hookworm infection is a major public health problem that threatens about 500 million people throughout tropical areas of the world. Adult hookworms survive for many years in the host intestine, where they suck blood, causing iron deficiency anemia and malnutrition. Numerous molecules, named excretory/secretory (ES) products, are secreted by hookworm adults and/or larvae to aid in parasite survival and pathobiology. Although the molecular cloning and characterization of hookworm ES products began 25 years ago, the biological role and molecular nature of many of them are still unclear. Hookworm ES products, with distinct structures and functions, have been linked to many essential events in the disease pathogenesis. These events include host invasion and tissue migration, parasite nourishment and reproduction, and immune modulation. Several of these products represent promising vaccine targets for controlling hookworm disease and therapeutic targets for many inflammatory diseases. This review aims to summarize our present knowledge about hookworm ES products, including their role in parasite biology, host-parasite interactions, and as vaccine and pharmaceutical targets and to identify research gaps and future research directions in this field.

Identification of proteins from the secretory/excretory products (SEPs) of the branchiuran ectoparasite Argulus foliaceus (Linnaeus, 1758) reveals unique secreted proteins amongst haematophagous ecdysozoa

BACKGROUND

It is hypothesised that being a blood-feeding ectoparasite, Argulus foliaceus (Linnaeus, 1758), uses similar mechanisms for digestion and host immune evasion to those used by other haematophagous ecdysozoa, including caligid copepods (e.g. sea louse). We recently described and characterised glands associated with the feeding appendages of A. foliaceus using histological techniques. The work described in the present study is the first undertaken with the objective of identifying and partially characterising the components secreted from these glands using a proteomic approach.

METHODS

Argulus foliaceus parasites were sampled from the skin of rainbow trout (Oncorhynchus mykiss), from Loch Fad on the Isle of Bute, Scotland, UK. The proteins from A. foliaceus secretory/excretory products (SEPs) were collected from the supernatant of artificial freshwater conditioned with active adult parasites (n = 5-9 per ml; n = 560 total). Proteins within the SEPs were identified and characterised using LC-ESI-MS/MS analysis. Data are available via ProteomeXchange with identifier PXD016226.

RESULTS

Data mining of a protein database translated from an A. foliaceus dataset using ProteinScape allowed identification of 27 predicted protein sequences from the A. foliaceus SEPs, each protein matching the criteria of 2 peptides with at least 4 contiguous amino acids. Nine proteins had no matching sequence through OmicsBox (Blast2GO) analysis searches suggesting that Argulus spp. may additionally have unique proteins present in their SEPs. SignalP 5.0 software, identified 13 proteins with a signal sequence suggestive of signal peptides and supportive of secreted proteins being identified. Notably, the functional characteristics of identified A. foliaceus proteins/domains have also been described from the salivary glands and saliva of other blood-feeding arthropods such as ticks. Identified proteins included: transporters, peroxidases, metalloproteases, proteases and serine protease inhibitors which are known to play roles in parasite immune evasion/induction (e.g. astacin), immunomodulation (e.g. serpin) and digestion (e.g. trypsin).

CONCLUSIONS

To our knowledge, the present study represents the first proteomic analysis undertaken for SEPs from any branchiuran fish louse. Here we reveal possible functional roles of A. foliaceus SEPs in digestion and immunomodulation, with a number of protein families shared with other haematophagous ectoparasites. A number of apparently unique secreted proteins were identified compared to other haematophagous ecdysozoa.

Cytokine production and signalling in human THP-1 macrophages is dependent on Toxocara canis glycans

The effect of Toxocara canis antigens on cytokine production by human THP-1 macrophages was studied in vitro. Toxocara Excretory–Secretory products (TES) and recombinant mucins (Tc-MUC-2, Tc-MUC-3, Tc-MUC-4, and Tc-MUC-5) as well as deglycosylated forms of these antigens were used in the study. TES products stimulated macrophages to produce the innate proinflammatory IL-1β, IL-6, and TNF-α cytokines regardless of the presence of glycans. Recombinant mucins induced glycan-dependent cytokine production. Sugar moieties led to at least 3-fold higher production of regulatory IL-10 as well as proinflammatory cytokines. The presence of glycans on mucins also affected the downstream signalling pathways in stimulated cells. The most prominent difference was noted in AKT and AMPK kinase activation. AKT phosphorylation was observed in cells stimulated with glycosylated mucins, whereas treatment with deglycosylated antigens led to AMPK phosphorylation. MAP kinase family members such as JNK and p38 and c-Jun transcription factor were phosphorylated in both cases what suggests that toll-like receptor signalling may be involved in mucin-treated macrophages. This pathway is however modified by other signalling molecules as only mucins containing intact sugars significantly induced the production of cytokines.

Modulation of Host Immunity by Helminths: The Expanding Repertoire of Parasite Effector Molecules

Helminths are extraordinarily successful parasites due to their ability to modulate the host immune response. They have evolved a spectrum of immunomodulatory molecules that are now beginning to be defined, heralding a molecular revolution in parasite immunology. These discoveries have the potential both to transform our understanding of parasite adaptation to the host and to develop possible therapies for immune-mediated disease. In this review we will summarize the current state of the art in parasite immunomodulation and discuss perspectives on future areas for research and discovery.

New Data on Human Macrophages Polarization by Hymenolepis diminuta Tapeworm-An In Vitro Study

Helminths and their products can suppress the host immune response to escape host defense mechanisms and establish chronic infections. Current studies indicate that macrophages play a key role in the immune response to pathogen invasion. They can be polarized into two distinct phenotypes: M1 and M2. The present paper examines the impact of the adult Hymenolepis diminuta (HD) tapeworm and its excretory/secretory products (ESP) on THP-1 macrophages. Monocytes were differentiated into macrophages and cultured with a living parasite or its ESP. Our findings indicate that HD and ESP have a considerable impact on human THP-1 macrophages. Macrophages treated with parasite ESP (with or without LPS) demonstrated reduced expression of cytokines (i.e., IL-1α, TNFα, TGFβ, IL-10) and chemokines (i.e., IL-8, MIP-1α, RANTES, and IL-1ra), while s-ICAM and CxCL10 expression rose after ESP stimulation. In addition, inflammatory factor expression rose significantly when macrophages were exposed to living parasites. Regarding induced and repressed pathways, significant differences were found between HD and ESP concerning their influence on the phosphorylation of ERK1/2, STAT2, STAT3, AMPKα1, Akt 1/2/3 S473, Hsp60, and Hck. The superior immunosuppressive properties of ESP compared to HD were demonstrated with lower levels of IL-1β, TNF-α, IL-6, IL-23, and IL-12p70 following stimulation. The presence of HD and its ESP were found to stimulate mixed M1/M2 macrophage phenotypes. Our findings indicate new molecular mechanisms involved in the response of human macrophages to tapeworm infection, this could be a valuable tool in understanding the mechanisms underlying the processes of immune regulation during cestodiasis.

Vaccination with a cocktail of Ancylostoma ceylanicum recombinant antigens leads to worm burden reduction in hamsters

Hookworms, a group to which Ancylostoma ceylanicum belongs, are gastrointestinal nematodes that infect more than 700 million people around the world. They are a leading cause of anemia in developing countries. In order to effectively prevent hookworm infections research is conducted to develop an effective vaccine using recombinant antigens of the parasite. The aim of this study was to examine the influence of the hosts' on protection against ancylostomiasis and the shaping of the humoral immune response among Syrian hamsters after immunization with a cocktail of five A. ceylanicum recombinant antigens. Ace-ASP-3, Ace-ASP-4, Ace-APR-1, Ace-MEP-6 and Ace-MEP-7 were obtained in the pET expression system. Immunization with a vaccine cocktail resulted in a 33.5% worm burden reduction. The immunogenicity of the recombinant proteins were determined using ELISA. Statistical analysis showed that vaccinated hamsters developed stronger humoral responses to four of five recombinant antigens (the exception being Ace-ASP-3) compared to hamsters from the control group.

Toxocara canis glycans influence antigen recognition by mouse IgG1 and IgM antibodies

The impact of sugar moieties of Toxocara canis glycoprotein antigens on their recognition by infected mouse antibodies was investigated in this study. Native TES and recombinant Toxocara mucins generated in Pichia pastoris yeast as well as their deglycosylated forms were used in ELISA. TES and recombinant mucins were equally recognized by T. canis infected mouse IgG1 antibodies. IgM immunoglobulins predominantly recognized TES antigens. Among mucins recognition of Tc-MUC-4 was the most significant. Deglycosylation of antigens resulted in significant loss of IgM and IgG1 reactivity to TES, mucins, Tc-MUC-3 and Tc-MUC-4. The presence of sugar moieties had no influence on IgE binding to native or recombinant T. canis antigens. Our results suggest that glycans are involved in epitope formation what should be taken into consideration in production of recombinant helminth antigens for diagnostic purposes.

Toxocara canis mucins among other excretory-secretory antigens induce in vitro secretion of cytokines by mouse splenocytes

The effect of Toxocara larval antigens on cytokine secretion by mouse splenocytes was studied in vitro. Recombinant mucins were produced in Pichia pastoris yeast, and Toxocara excretory-secretory (TES) antigens were collected from in vitro culture of L2 larvae. Tc-MUC-2, Tc-MUC-3, Tc-MUC-4, and Tc-MUC-5 were expressed as glycoproteins and were specifically recognized by Toxocara canis-infected dog serum antibodies. Mouse splenocytes stimulated with recombinant mucins produced IL-5, IL-6, and TGF-β. Cell stimulation with whole TES products was more effective and resulted in secretion of IL-4, IL-5, IL-6, IL-10, and TGF-β and downregulation of TNF-α production. IFN-γ and IL-17 secretion was noted only after ConA treatment. Cells originating from infected animals produced significantly smaller amounts of these two cytokines compared to control cells, which suggests that Th1 and Th17 response in infected mice is strongly inhibited. However, splenocyte stimulation with both TES and ConA upregulated the production of IFN-γ and IL-17. This shows that TES antigens have strong immunomodulatory properties and are able to induce a broad range of effects on murine immune cells.

Molecular cloning and analysis of Ancylostoma ceylanicum glutamate-cysteine ligase

Glutamate-cysteine ligase (GCL) is a heterodimer enzyme composed of a catalytic subunit (GCLC) and a modifier subunit (GCLM). This enzyme catalyses the synthesis of γ-glutamylcysteine, a precursor of glutathione. cDNAs of the putative glutamate-cysteine ligase catalytic (Ace-GCLC) and modifier subunits (Ace-GCLM) of Ancylostoma ceylanicum were cloned using the RACE-PCR amplification method. The Ace-gclc and Ace-gclm cDNAs encode proteins with 655 and 254 amino acids and calculated molecular masses of 74.76 and 28.51kDa, respectively. The Ace-GCLC amino acid sequence shares about 70% identity and 80% sequence similarity with orthologs in Loa loa, Onchocerca volvulus, Brugia malayi, and Ascaris suum, whereas the Ace-GCLM amino acid sequence has only about 30% sequence identity and 50% similarity to homologous proteins in those species. Real-time PCR analysis of mRNA expression in L3, serum stimulated L3 and adult stages of A. ceylanicum showed the highest level of Ace-GCLC and Ace-GCLM expression occurred in adult worms. No differences were detected among adult hookworms harvested 21 and 35dpi indicating expression of Ace-gclc and Ace-gclm in adult worms is constant during the course of infection. Positive interaction between two subunits of glutamate-cysteine ligase was detected using the yeast two-hybrid system, and by specific enzymatic reaction. Ace-GCL is an intracellular enzyme and is not exposed to the host immune system. Thus, as expected, we did not detect IgG antibodies against Ace-GCLC or Ace-GCLM on days 21, 60 and 120 of A. ceylanicum infection in hamsters. Furthermore, vaccination with one or both antigens did not reduce worm burdens, and resulted in no improvement of clinical parameters (hematocrit and hemoglobin) of infected hamsters. Therefore, due to the significant role of the enzyme in parasite metabolism, our analyses raises hope for the development of a successful new drug against ancylostomiasis based on the specific GCL inhibitor.

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.

Molecular cloning and expression of the cDNA sequence encoding a novel aspartic protease from Uncinaria stenocephala

Uncinaria stenocephala belongs to Ancylostomatidae family. Members of this family - hookworms - infect millions of people and animals worldwide. U. stenocephala is most pathogenic in dogs and other Canidae, which are the main hosts, and infection causes anemia or even death. So far no effective hookworm vaccine has been developed that is economically viable. Attempts to identify vaccine antigens have led to a group of aspartic proteases, which play a key role in parasite feeding, migration through host tissues and immune evasion. The cDNA of an aspartic protease from U. stenocephala was cloned using the RACE-PCR method. Computational analysis showed that the cDNA encodes a 447 amino acid protein with a molecular mass of 52kDa that shows high homology to aspartic proteases from related hookworms. Analysis identified 1 potential N-glycosylation site, 3 potential disulfide bonds and no O-glycosylation sites. The recombinant protein was expressed in Escherichia coli followed by purification and mouse immunization. Using raised anti-Us-APR-1(2) (Uncinaria stenocephala Aspartic protease-1) serum the presence of Us-APR-1 in the adult stage of U. stenocephala and the expression of homologous protease in L3 and adult stages of A. ceylanicum was confirmed. This analysis is the first phase of work exploring the biological role of Us-APR-1 in parasite-host interactions and raises hope for successful vaccine development against Uncinaria sp. and possibly Ancylostoma sp.