Protective immune responses against Schistosoma mansoni infection by immunization with functionally active gut-derived cysteine peptidases alone and in combination with glyceraldehyde 3-phosphate dehydrogenase

Differential protective impact of peptide vaccine formulae targeting the lung- and liver-stage of challenge Schistosoma mansoni infection in mice

The study aimed to elicit protective immune responses against murine schistosomiasis mansoni at the parasite lung- and liver stage. Two peptides showing amino acid sequence similarity to gut cysteine peptidases, which induce strong memory immune effectors in the liver, were combined with a peptide based on S. mansoni thioredoxin peroxidase (TPX), a prominent lung-stage schistosomula excretory-secretory product, and alum as adjuvant. Only one of the 2 cysteine peptidases-based peptides in a multiple antigenic peptide construct (MAP-3 and MAP-4) appeared to adjuvant protective immune responses induced by the TPX peptide in a MAP form. Production of TPX MAP-specific IgG1 serum antibodies, and increase in lung interleukin-1 (IL-1), uric acid, and reactive oxygen species (ROS) content were associated with significant (P < 0.05) 50 % reduction in recovery of lung-stage larvae. Increase in lung triglycerides and cholesterol levels appeared to provide the surviving worms with nutrients necessary for a stout double lipid bilayer barrier at the parasite-host interface. Surviving worms-released products elicited memory responses to the MAP-3 immunogen, including production of specific IgG1 antibodies and increase in liver IL-33 and ROS. Reduction in challenge worm burden recorded 45 days post infection did not exceed 48 % associated with no differences in parasite egg counts in the host liver and small intestine compared to unimmunized adjuvant control mice. Alum adjuvant assisted the second peptide, MAP-4, in production of IgG1, IgG2a, IgG2b and IgA specific antibodies and increase in liver ROS, but with no protective potential, raising doubt about the necessity of adjuvant addition. Accordingly, different vaccine formulas containing TPX MAP and 1, 2 or 3 cysteine peptidases-derived peptides with or without alum were used to immunize parallel groups of mice. Compared to unimmunized control mice, significant (P < 0.05 to < 0.005) 22 to 54 % reduction in worm burden was recorded in the different groups associated with insignificant changes in parasite egg output. The results together indicated that a schistosomiasis vaccine able to entirely prevent disease and halt its transmission still remains elusive.

GLYCOLYTIC ENZYMES AS VACCINES AGAINST SCHISTOSOMIASIS: TESTING SCHISTOSOMA MANSONI PHOSPHOGLYCERATE MUTASE IN MICE

Schistosomiasis is a globally burdensome parasitic disease caused by flatworms (blood flukes) in the genus Schistosoma. The current standard treatment for schistosomiasis is the drug praziquantel, but there is an urgent need to advance novel interventions such as vaccines. Several glycolytic enzymes have been evaluated as vaccine targets for schistosomiasis, and data from these studies are reviewed here. Although these parasites are canonically considered to be intracellular, proteomic analysis has revealed that many schistosome glycolytic enzymes are additionally found at the host-interactive surface. We have recently found that the intravascular stage of Schistosoma mansoni (Sm) expresses the glycolytic enzyme phosphoglycerate mutase (PGM) on the tegumental surface. Live parasites display PGM activity, and suppression of PGM gene expression by RNA interference diminishes surface enzyme activity. Recombinant SmPGM (rSmPGM) can cleave its glycolytic substrate, 3-phosphoglycerate and can both bind to plasminogen and promote its conversion to an active form (plasmin) in vitro, suggesting a moonlighting role for this enzyme in regulating thrombosis in vivo. We found that antibodies in sera from chronically infected mice recognize rSmPGM. We also tested the protective efficacy of rSmPGM as a vaccine in the murine model. Although immunization generates high titers of anti-SmPGM antibodies (against both recombinant and native SmPGM), no significant differences in worm numbers were found between vaccinated and control animals.

Schistosoma mansoni vaccine candidates identified by unbiased phage display screening in self-cured rhesus macaques

Schistosomiasis, a challenging neglected tropical disease, affects millions of people worldwide. Developing a prophylactic vaccine against Schistosoma mansoni has been hindered by the parasite's biological complexity. In this study, we utilized the innovative phage-display immunoprecipitation followed by a sequencing approach (PhIP-Seq) to screen the immune response of 10 infected rhesus macaques during self-cure and challenge-resistant phases, identifying vaccine candidates. Our high-throughput S. mansoni synthetic DNA phage-display library encoded 99.6% of 119,747 58-mer peptides, providing comprehensive coverage of the parasite's proteome. Library screening with rhesus macaques' antibodies, from the early phase of establishment of parasite infection, identified significantly enriched epitopes of parasite extracellular proteins known to be expressed in the digestive tract, shifting towards intracellular proteins during the late phase of parasite clearance. Immunization of mice with a selected pool of PhIP-Seq-enriched phage-displayed peptides from MEG proteins, cathepsins B, and asparaginyl endopeptidase significantly reduced worm burden in a vaccination assay. These findings enhance our understanding of parasite-host immune responses and provide promising prospects for developing an effective schistosomiasis vaccine.

Increased hepatic interleukin-1, arachidonic acid, and reactive oxygen species mediate the protective potential of peptides shared by gut cysteine peptidases against Schistosoma mansoni infection in mice

BACKGROUND

Multiple antigen peptide (MAP) construct of peptide with high homology to Schistosoma mansoni cathepsin B1, MAP-1, and to cathepsins of the L family, MAP-2, consistently induced significant (P < 0.05) reduction in challenge S. mansoni worm burden. It was, however, necessary to modify the vaccine formula to counteract the MAP impact on the parasite egg counts and vitality, and discover the mechanisms underlying the vaccine protective potential.

METHODOLOGY

Outbred mice were immunized with MAP-2 in combination with alum and/or MAP-1. Challenge infection was performed three weeks (wks) after the second injection. Blood and liver pieces were obtained on an individual mouse basis, 23 days post-infection (PI), a time of S. mansoni development and feeding in the liver before mating. Serum samples were examined for the levels of circulating antibodies and cytokines. Liver homogenates were used for assessment of liver cytokines, uric acid, arachidonic acid (ARA), and reactive oxygen species (ROS) content. Parasitological parameters were evaluated 7 wks PI.

PRINCIPAL FINDINGS

Immunization of outbred mice with MAP-2 in combination with alum and/or MAP-1 elicited highly significant (P < 0.005) reduction of around 60% in challenge S. mansoni worm burden and no increase in worm eggs' loads or vitality, compared to unimmunized or alum pre-treated control mice. Host memory responses to the immunogens are expected to be expressed in the liver stage when worm feeding and cysteine peptidases release start to be active. Serum antibody and cytokine levels were not significantly different between control and vaccinated mouse groups. Highly significant (P < 0.05 - <0.0001) increase in liver interleukin-1, ARA, and ROS content was recorded in MAP-immunized compared to control mice.

CONCLUSION/SIGNIFICANCE

The findings provided an explanation for the gut cysteine peptidases vaccine-mediated reduction in challenge worm burden and increase in egg counts.

Glyceraldehyde-3-phosphate dehydrogenase affects the growth of Schistosoma japonicum schistosomula

This study was conducted to evaluate the effect of glyceraldehyde-3-phosphate dehydrogenase from Schistosoma japonicum (SjGAPDH) on the growth of schistosomula. Quantitative reverse transcription PCR and immunohistochemical analysis were performed to analyze the mRNA levels and immune localization of SjGAPDH. RNA interference experiments were conducted to further examine the role of SjGAPDH in the schistosomula growth of S. japonicum. The results demonstrated that SjGAPDH mRNA was expressed during all stages of S. japonicum development, with its expression gradually increasing over time. SjGAPDH was mainly distributed on the surface and in some parenchymal cells of S. japonicum. Double-stranded RNA-mediated GAPDH knockdown reduced SjGAPDH expression by approximately 59%. Light microscopic observations revealed that the size, length, width, volume, and area of schistosomula in the SjGAPDH interference group were significantly lower than those in the enhanced green fluorescent protein control group. These findings indicate that SjGAPDH may affect the growth of S. japonicum schistosomula and could be a useful target for treating schistosomiasis.

De Novo Design of Cathepsin B1 Inhibitors as Potential Anti-Schistosomal Agents Using Computational Studies

Background

Schistosomiasis is the world’s second most devastating disease after malaria and the leading cause of disease and mortality for more than 200 million people in developing countries. Cysteine proteases, in particular SmCB1, are the most well-researched biological targets for this disorder.

Objective

To apply computational techniques to design new antischistosomal agents against SmCB1 protein with favorable pharmacokinetic properties.

Methods

The smCB1 receptor-based pharmacophore model was created and used to screen 567,000 fragments from the Enamine library. The best scoring fragments have been linked to build novel compounds that were subjected to molecular docking, MM-GBSA free energy estimation, ADME prediction, and molecular dynamics.

Results

A seven-point pharmacophore hypothesis ADDDRRR was created. The developed hypothesis was used to screen 1.3 M fragment conformations. Among them, 23,732 fragments matched the hypothesis and screened against the protein. The top 50 fragments were used to design new 7745 compounds using the Breed ligand panel which were subjected to docking and MMGBSA binding energy. This led to the identification of 10 compounds with better docking scores (−8.033– −7.483 kcal/mol) and lower-bound free energies (−58.49 – −40.02 kcal/mol) compared to the reference bound ligand. Most of the designed compounds demonstrated good drug-like properties. Concerning Molecular dynamics (MD) simulation results, a low root mean square deviation (RMSD) range (0.25–1.2 Å) was found for the top 3 complexes which indicated their stability.

Conclusion

We identified compounds that could be potential candidates in the search for novel Schistosoma mansoni inhibitors by targeting SmCB1 utilizing various computational tools. Three newly designed compounds namely breed 1, 2, and 3 showed promising affinity to the target as well as favorable drug-like properties which might be considered potential anti-schistosomal agents.

Different panel of toll-like receptors expression during chronic Schistosoma mansoni infection in experimental animals

BACKGROUND

Many studies have reported the immunomodulatory effect of helminths to avoid the lethal immunopathology. During schistosomiasis, the immune response is orchestrated by toll-like receptors (TLRs). Modulating TLRs can alter the function of antigen presentation cells with the shift of the host's Th1 response to a dominant regulatory Th2 response. The objective of our study was to clarify which TLRs are related to the immune response of chronic Schistosoma infection.

METHODS

The study animals were divided into two groups; group I: uninfected mice; control group and group II: Schistosoma mansoni infected mice. mRNA expression of TLR2, 3, 4, 7, and 9 in different organs (liver, large intestine, and spleen) were assessed on day 90 post-infection.

RESULTS

TLR gene expression has changed depending on the tissue studied as the mRNA level of TLR2, TLR7, and TLR9 were significantly upregulated in all examined organs while TLR3 expression showed only significant upregulation in the liver of infected mice. On the other hand, TLR4 expression was significantly upregulated in the liver while significantly downregulated in the large intestine.

CONCLUSION

This study provides a better understanding of TLRs profile in different organs against S. mansoni parasites during the chronic phase of infection.

Pathological and immunological evaluation of different regimens of praziquantel treatment in a mouse model of Schistosoma mansoni infection

Background

One of the considerable challenges of schistosomiasis chemotherapy is the inefficacy of praziquantel (PZQ) at the initial phase of the infection. Immature schistosomes are not susceptible to PZQ at the curative dose. Here, we investigated the efficacy of different PZQ regimens administered during the initial stage of Schistosoma mansoni infection in mice.

Methodology/Principal findings

Two months-old mice were individually infected with 80 S. mansoni cercariae and divided into one infected-untreated control group (IC) and four PZQ-treated groups: PZQ at 100 mg/kg/day for five consecutive days (group PZQ1), PZQ at 100 mg/kg/day for 28 days (group PZQ2), PZQ at 18 mg/kg/day for 28 days (group PZQ3) and a single dose of PZQ at 500 mg/kg (group PZQ4). The treatment started on day one post-infection (p.i), and each group of mice was divided into two subgroups euthanized on day 36 or 56 p.i, respectively. We determined the mortality rate, the parasitological burden, the hepatic and intestinal granulomas, the serum levels of Th-1, Th-2, and Th-17 cytokines, and gene expression. The treatment led to a significant (p < 0.001) reduction of worm burden and egg counts in the intestine and liver in groups PZQ2 and PZQ3. On 56th day p.i, there was a significant reduction (p < 0.001) of the number and volume of the hepatic granulomas in groups PZQ2 and PZQ3 compared to group PZQ1 or PZQ4. Moreover, in group PZQ3, the serum levels of IFN-γ, TNF-α, IL-13, and IL-17 and their liver mRNA expressions were significantly reduced while IL-10 and TGF-β gene expression significantly increased. The highest mortality rate (81.25%) was recorded in group PZQ2.

Conclusion/Significance

This study revealed that the administration of PZQ at 18 mg/kg/day for 28 consecutive days was the optimal effective posology for treating S. mansoni infection at the initial stage in a murine model.

Protective immune potential of multiple antigenic peptide (MAP) constructs comprising peptides that are shared by several cysteine peptidases against Schistosoma mansoni infection in mice

In vaccine trials, Schistosoma mansoni cathepsin B1 (SmCB1), helminth cathepsins of the L family (e.g., SmCL3), and papain consistently induce highly significant reductions in challenge worm burden and egg viability, but generated no additive protective effects when used in combination. The protective capacity of the cysteine peptidases is associated with modest (SmCB1) and poor (cathepsins L) production of cytokines and antibodies, essentially of the type 2 axis, and is only marginally reduced upon use of proteolytically inactive enzymes. In this work, peptides shared by SmCB1, cathepsins of the L family, papain and other allergens were selected, synthesized as tetrabranched multiple antigen peptide constructs (MAP-1 and MAP-2), and used in two independent experiments to immunize outbred mice, in parallel with papain. The two peptides elicited significant (P <  0.05) reduction in challenge worm burden when compared to unimmunized mice, albeit lower than that achieved by papain. Protection was associated with modest serum type 2 cytokines and antibody levels in MAP-, and papain-immunized mice. Immunization with papain also elicited a reduction in parasite egg load, viability, and granuloma numbers in liver and intestine. MAP-1 and MAP-2 immunogens displayed some opposite effects- MAP-1 leading to higher egg numbers with poor vitality, whereas MAP-2 immunization yielded fewer eggs. Cysteine peptidase thus appear to carry peptides that elicit opposing outcomes, highlighting the difficulty of reaching fully fledged protection, unless a vaccine is based on carefully selected peptides and combined with an effective adjuvant.

Evaluation of Streptococcus uberis Surface Proteins as Vaccine Antigens to Control S. uberis Mastitis in Dairy Cows

There is no effective vaccine against Streptococcus uberis mastitis in dairy cows. Objectives of this study were (1) to extract S. uberis surface proteins (SUSP) and determine immunoreactivity in vitro and (2) immunogenicity and efficacy in vivo. SUSP was extracted from S. uberis, and their immunoreactivity was tested by western blot. In total, 26 Jersey dairy cows were randomly divided into four groups. Groups 1, 2, and 3 were vaccinated subcutaneously with 4 mg, 1 mg, and 100 μg of SUSP, respectively, with Freund's incomplete adjuvant. Group 4 (control) was injected with placebo. S. uberis UT888 was infused into two contralateral quarters of each cow during early lactation. Somatic cell count (SCC), bacteria count in milk, and mastitis were monitored. Our results show that SUSP contains multiple protein bands, that ranged from 10 to 100 kDa. All vaccinates showed an increased anti-SUSP IgG antibody. The SCC of all experimentally infected quarters increased after challenge but slightly decreased after day 3 with no significant difference among groups. Milk bacterial count was significantly (p < 0.05) reduced in high and medium doses vaccinated groups than low and control groups. In conclusion, SUSP vaccine is immunogenic and showed a promising efficacy to control bovine S. uberis mastitis.

A comprehensive and critical overview of schistosomiasis vaccine candidates

A digenetic platyhelminth Schistosoma is the causative agent of schistosomiasis, one of the neglected tropical diseases that affect humans and animals in numerous countries in the Middle East, sub-Saharan Africa, South America and China. Several control methods were used for prevention of infection or treatment of acute and chronic disease. Mass drug administration led to reduction in heavy-intensity infections and morbidity, but failed to decrease schistosomiasis prevalence and eliminate transmission, indicating the need to develop anti-schistosome vaccine to prevent infection and parasite transmission. This review summarizes the efficacy and protective capacity of available schistosomiasis vaccine candidates with some insights and future prospects.

Structure determination and analyses of the GAPDH from the parasite Schistosoma mansoni, the first one from a platyhelminth

The enzyme Glyceraldehyde-3-Phosphate Dehydrogenase from Schistosoma mansoni (SmGAPDH) is characterized as a therapeutical target for schistosomiasis. In this context, we report here the experimental structure, structural analyses and comparisons of SmGAPDH, the first one from a Platyhelminth. The enzyme was expressed, purified and assayed for crystallization, what allowed the obtainment of crystals of sufficient quality to collect X-ray diffraction data up to 2.51 Å resolution. SmGAPDH is the only GAPDH to present the sequence NNR (its residues 114-116) which leads to (especially R116) a hydrogen bond network that possibly reflects on the flexibility of residues to interact with the adenine part of NAD⁺, speculated to be important for differential drug design.

T Cell Peptides Derived from Invasive Stages of Schistosoma mansoni as Potential Schistosomiasis Vaccine

Schistosomiasis is a parasitic disease that affects 143 million people in endemic countries. This work analyzed overexpressed sequences from the cercaria phase to the early schistosomulum phase using bioinformatics tools to predict host interaction and selected proteins for predicting T cell epitopes. The final peptides were chemically synthesized, and their toxicity was evaluated in vitro. Peptides were formulated in the Adjuvant Adaptation (ADAD) vaccination system and injected into BALB/c mice that were challenged with S. mansoni cercariae to assess protection and immunogenicity. A total of 39 highly expressed S.mansoni proteins were identified as being of potential interest. Three T cell peptides predicted to bind MHC mouse and human class II were synthesized and formulated for vaccination. SmGSP and SmIKE reduced the number of eggs trapped in the liver by more than 50% in challenged BALB/c mice. The liver of mice vaccinated with either SmGSP or SmTNP had a significantly reduced affected liver surface. Transcriptome-based T cell peptides elicit partial protection and could be candidates for a multiantigen vaccine.

Arachidonic Acid Is a Safe and Efficacious Schistosomicide, and an Endoschistosomicide in Natural and Experimental Infections, and Cysteine Peptidase Vaccinated Hosts

Blood flukes of the genus Schistosoma are covered by a protective heptalaminated, double lipid bilayer surface membrane. Large amounts of sphingomyelin (SM) in the outer leaflet form with surrounding water molecules a tight hydrogen bond barrier, which allows entry of nutrients and prevents access of host immune effectors. Excessive hydrolysis of SM to phosphoryl choline and ceramide via activation of the parasite tegument-associated neutral sphingomyelinase (nSMase) with the polyunsaturated fatty acid, arachidonic acid (ARA) leads to parasite death, via allowing exposure of apical membrane antigens to antibody-dependent cell-mediated cytotoxicity (ADCC), and accumulation of the pro-apoptotic ceramide. Surface membrane nSMase represents, thus, a worm Achilles heel, and ARA a valid schistosomicide. Several experiments conducted in vitro using larval, juvenile, and adult Schistosoma mansoni and Schistosoma haematobium documented ARA schistosomicidal potential. Arachidonic acid schistosomicidal action was shown to be safe and efficacious in mice and hamsters infected with S. mansoni and S. haematobium, respectively, and in children with light S. mansoni infection. A combination of praziquantel and ARA led to outstanding cure rates in children with heavy S. mansoni infection. Additionally, ample evidence was obtained for the powerful ARA ovocidal potential in vivo and in vitro against S. mansoni and S. haematobium liver and intestine eggs. Studies documented ARA as an endogenous schistosomicide in the final mammalian and intermediate snail hosts, and in mice and hamsters, immunized with the cysteine peptidase-based vaccine. These findings together support our advocating the nutrient ARA as the safe and efficacious schistosomicide of the future.

Adjuvanted Schistosoma mansoni-Cathepsin B With Sulfated Lactosyl Archaeol Archaeosomes or AddaVax™ Provides Protection in a Pre-Clinical Schistosomiasis Model

Schistosomiasis threatens 800 million people worldwide. Chronic pathology manifests as hepatosplenomegaly, and intestinal schistosomiasis caused by Schistosoma mansoni can lead to liver fibrosis, cirrhosis, and blood in the stool. To assist the only FDA-approved drug, praziquantel, in parasite elimination, the development of a vaccine would be of high value. S. mansoni Cathepsin B (SmCB) is a well-documented vaccine target for intestinal schistosomiasis. Herein, we test the increased efficacy and immunogenicity of SmCB when combined with sulfated lactosyl archaeol (SLA) archaeosomes or AddaVax™ (a squalene based oil-in-water emulsion). Both vaccine formulations resulted in robust humoral and cell mediated immune responses. Impressively, both formulations were able to reduce parasite burden greater than 40% (WHO standard), with AddaVax™ reaching 86.8%. Additionally, SmCB with both adjuvants were able to reduce granuloma size and the amount of larval parasite hatched from feces, which would reduce transmission. Our data support SmCB as a target for S. mansoni vaccination; especially when used in an adjuvanted formulation.

Specific Antibodies and Arachidonic Acid Mediate the Protection Induced by the Schistosoma mansoni Cysteine Peptidase-Based Vaccine in Mice

Several reports have documented the reproducible and considerable efficacy of the cysteine peptidase-based schistosomiasis vaccine in the protection of mice and hamsters against infection with Schistosoma mansoni and Schistosomahaematobium, respectively. Here, we attempt to identify and define the protection mechanism(s) of the vaccine in the outbred CD-1 mice-S. mansoni model. Mice were percutaneously exposed to S. mansoni cercariae following immunization twice with 0 or 10 μg S. mansoni recombinant cathepsin B1 (SmCB1) or L3 (SmCL3). They were examined at specified intervals post infection (pi) for the level of serum antibodies, uric acid, which amplifies type 2 immune responses and is an anti-oxidant, lipids, in particular, arachidonic acid (ARA), which is an endoschistosomicide and ovocide, as well as uric acid and ARA in the lung and liver. Memory IgG1, IgG2a, and IgG2b antibodies to the cysteine peptidase immunogen were detectable at and following day 17 pi. Serum, lung, and liver uric acid levels in immunized mice were higher than in naïve and unimmunized mice, likely as a consequence of cysteine peptidase-mediated catabolic activity. Increased circulating uric acid in cysteine peptidase-immunized mice was associated with elevation in the amount of ARA in lung and liver at every test interval, and in serum starting at day 17 pi. Together, the results suggest the collaboration of humoral antibodies and ARA schistosomicidal potential in the attrition of challenge S. mansoni (p < 0.0005) at the liver stage, and ARA direct parasite egg killing (p < 0.005). The anti-oxidant and reactive oxygen species-scavenger properties of uric acid may be responsible for the cysteine peptidase vaccine protection ceiling. This article represents a step towards clarifying the protection mechanism of the cysteine peptidase-based schistosomiasis vaccine.

Mechanism by which the combination of SjCL3 and SjGAPDH protects against Schistosoma japonicum infection

A vaccine is an important method to control schistosomiasis. Molecules related to lung-stage schistosomulum are considered potential vaccine candidates. We previously showed that glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and cathepsin L3 (CL3) displayed differential expression in the lung-stage schistosomula of Schistosoma japonicum cocultured with host cells. In the present study, we prepared the two proteins and detected the protective effects of SjGAPDH by immunizing mice with this protein alone and in combination with SjCL3 with or without Freund's adjuvant. Then, we investigated the possible mechanisms underlying S. japonicum infection. The results showed that vaccination of adjuvanted SjGAPDH decreased the worm burden (37.8%) and egg load (38.1%), and the combination of adjuvanted SjGAPDH and SjCL3 further decreased the worm burden (65.6%) and egg load (70.9%) during Schistosoma japonicum infection. However, the immunization of a combination of adjuvant-free SjGAPDH and SjCL3 displayed a lower protective effect (< 15%) than those of the adjuvanted SjCL3, the adjuvanted SjGAPDH, and a combination of adjuvanted SjGAPDH and SjCL3. Flow cytometric results showed that the frequency of regulatory T cells (Tregs) was lower (P < 0.05) in the group with adjuvanted SjGAPDH and SjCL3 (2.61%) than the remaining groups. The enzyme-linked immunosorbent assay (ELISA) results indicated that except for the uninfected and infected control groups, the remaining groups displayed a Th1-type shift in immune responses. These results showed the immunization of SjGAPDH resulted in partial protection (approximately 38%); inoculation with a combination of SjCL3 and SjGAPDH in Freund's adjuvant resulted in a high immunoprotective effect (> 65%) against Schistosoma japonicum infection in mice, which was possibly caused by the reduced percentage of Tregs and a Th1-type shift in immune responses; and SjCL3 has no adjuvant-like effect, dissimilar to SmCL3.

An immunoinformatics approach for the design of a multi-epitope subunit vaccine for urogenital schistosomiasis

Discovery of T and B memory cells capable of eliciting long-term immunity against schistosomiasisis is important for people in endemic areas. Changes in schistosomes environment due to developmental cycle, induces up-regulation of Heat Shock Proteins (HSPs) which assist the parasite in coping with the hostile conditions associated with its life cycle. This study therefore focused on exploring the role of HSPs in urogenital schistosomiasis to develop new multi-epitope subunit vaccine against the disease using immunoinformatic approaches. The designed subunit vaccine was subjected to in silico antigenicity, immunogenicity, allergenicity and physicochemical parameters analysis. A 3D structure of the vaccine construct was predicted, followed by disulphide engineering for stability, codon adaptation and in silico cloning for proper expression and molecular protein–protein docking of vaccine construct in the vector against toll-like receptor 4 receptor, respectively. Consequently, a 493 amino acid multi-epitope vaccine construct of antigenicity probability of 0.91 was designed. This was predicted to be stable, non-allergenic in nature and safe for human use.

Schistosoma mansoni glyceraldehyde-3-phosphate dehydrogenase enhances formation of the blood-clot lysis protein plasmin

Schistosomes are intravascular blood flukes that cause the parasitic disease schistosomiasis. In agreement with Schistosoma mansoni (Sm) proteomic analysis, we show here that the normally intracellular glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is also found at the parasite surface; live worms from all intravascular life stages display GAPDH activity. Suppressing GAPDH gene expression using RNA interference significantly lowers this live worm surface activity. Medium in which the worms are cultured overnight displays essentially no activity, showing that the enzyme is not shed or excreted but remains associated with the worm surface. Immunolocalization experiments confirm that the enzyme is highly expressed in the parasite tegument (skin). Surface activity in schistosomula amounts to ∼8% of that displayed by equivalent parasite lysates. To address the functional role of SmGAPDH, we purified the protein following its expression in Escherichiacoli strain DS113. The recombinant protein displays optimal enzymatic activity at pH 9.2, shows robust activity at the temperature of the parasite's hosts, and has a Michaelis-Menten constant for glyceraldehyde-3-phosphate (GAP) of 1.4 mM±0.24. We show that recombinant SmGAPDH binds plasminogen (PLMG) and promotes PLMG conversion to its active form (plasmin) in a dose response in the presence of tissue plasminogen activator. Since plasmin is a key mediator of thrombolysis, our results support the hypothesis that SmGAPDH, a host-interactive tegumental protein that can enhance PLMG activation, could help degrade blood clots around the worms in the vascular microenvironment and thus promote parasite survival in vivoThis article has an associated First Person interview with the first author of the paper.

Characteristics and function of cathepsin L3 from Schistosoma japonicum

Schistosomiasis is still prevalent and seriously endangering the health of people and livestock in many countries. There have been great efforts to develop vaccines against schistosomiasis for prolonged protection in epidemic areas. Molecules from lung-stage schistosomula have been regarded as potential vaccine candidates against schistosomiasis. Our previous work has shown that cathepsin L3 from Schistosoma japonicum (SjCL3) is expressed in lung-stage schistosomula, but its role is not well known. In the present study, we characterized SjCL3 and detected its effect as a possible vaccine in vivo and in vitro. From the results of quantitative PCR (qPCR) and western blot, SjCL3 was present throughout the lifecycle of the worm, and its relative expressed level was higher in the liver eggs and adult worms than other stages. Additionally, immunofluorescence assay showed that SjCL3 was mainly concentrated in the eggshell, alimentary canal, and musculature of worms. Compared with the adjuvant group, the immunization of SjCL3 in mice resulted in a 28.9% decrease in worm burden and a 29.2% reduction in egg number in the host liver. In antibody-dependent cell-mediated cytotoxicity (ADCC) insecticidal experiments in vitro, the existence of SjCL3 could in part suppress adherence between macrophages and worm. The above results indicated that the immunization of SjCL3 could induce limited immune protection against S. japonicum infection in mice, and this protease played a role in breaking the process of ADCC, which was beneficial to the survival of worms.

T Lymphocyte-Mediated Liver Immunopathology of Schistosomiasis

The parasitic worms, Schistosoma mansoni and Schistosoma japonicum, reside in the mesenteric veins, where they release eggs that induce a dramatic granulomatous response in the liver and intestines. Subsequently, infection may further develop into significant fibrosis and portal hypertension. Over the past several years, uncovering the mechanism of immunopathology in schistosomiasis has become a major research objective. It is known that T lymphocytes, especially CD4⁺ T cells, are essential for immune responses against Schistosoma species. However, obtaining a clear understanding of how T lymphocytes regulate the pathological process is proving to be a daunting challenge. To date, CD4⁺ T cell subsets have been classified into several distinct T helper (Th) phenotypes including Th1, Th2, Th17, T follicular helper cells (Tfh), Th9, and regulatory T cells (Tregs). In the case of schistosomiasis, the granulomatous inflammation and the chronic liver pathology are critically regulated by the Th1/Th2 responses. Animal studies suggest that there is a moderate Th1 response to parasite antigens during the acute stage, but then, egg-derived antigens induce a sustained and dominant Th2 response that mediates granuloma formation and liver fibrosis. In addition, the newly discovered Th17 cells also play a critical role in the hepatic immunopathology of schistosomiasis. Within the liver, Tregs are recruited to hepatic granulomas and exert an immunosuppressive role to limit the granulomatous inflammation and fibrosis. Moreover, recent studies have shown that Tfh and Th9 cells might also promote liver granulomas and fibrogenesis in the murine schistosomiasis. Thus, during infection, T-cell subsets undergo complicated cross-talk with antigen presenting cells that then defines their various roles in the local microenvironment for regulating the pathological progression of schistosomiasis. This current review summarizes a vast body of literature to elucidate the contribution of T lymphocytes and their associated cytokines in the immunopathology of schistosomiasis.

Proteomic analysis of adult Schistosoma mekongi somatic and excretory-secretory proteins

Schistosoma mekongi is a causative agent of human schistosomiasis. There is limited knowledge of the molecular biology of S. mekongi and very few studies have examined drug targets, vaccine candidates and diagnostic biomarkers for S. mekongi. To explore the biology of S. mekongi, computational as well as experimental approaches were performed on S. mekongi males and females to identify excretory-secretory (ES) proteins and proteins that are differentially expressed between genders. According to bioinformatic prediction, the S. mekongi ES product was approximately 4.7% of total annotated transcriptome sequences. The classical secretory pathway was the main process to secrete proteins. Mass spectrometry-based quantification of male and female adult S. mekongi proteins was performed. We identified 174 and 156 differential expression of proteins in male and female worms, respectively. The dominant male-biased proteins were involved in actin filament-based processes, microtubule-based processes, biosynthetic processes and homeostatic processes. The major female-biased proteins were related to biosynthetic processes, organelle organization and signal transduction. An experimental approach identified 88 proteins in the S. mekongi secretome. The S. mekongi ES proteins mainly contributed to nutrient uptake, essential substance supply and host immune evasion. This research identifies proteins in the S. mekongi secretome and provides information on ES proteins that are differentially expressed between S. mekongi genders. These findings will contribute to S. mekongi drug and vaccine development. In addition, the study enhances our understanding of basic S. mekongi biology.

Effects of regulatory T cells on glyceraldehyde-3-phosphate dehydrogenase vaccine efficacy against Schistosoma japonicum

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a candidate subunit vaccine that induces protective immunity and elicits partial resistance to Schistosoma japonicum upon mouse and livestock vaccination. This study aimed to evaluate the effect of regulatory T cells (Tregs), which were defined as CD4⁺CD25⁺Foxp3⁺ cells, on the efficacy of a GAPDH vaccine against S. japonicum. BALB/c female mice were randomly divided into five groups as follows: normal, infected control, anti-CD25 monoclonal antibody (anti-CD25 mAb), GAPDH group, and co-treated with anti-CD25 mAb and GAPDH group. The worm reduction and liver egg reduction rates in the GAPDH group were 32.46% and 35.43%, respectively, which increased to 60.09% and 58.78%, respectively, after anti-CD25 mAb administration. Compared with those in the infected control group, the percentage of Tregs in the spleen decreased significantly when GAPDH and anti-CD25 mAb were used either alone or in combination. Furthermore, secretions associated with the Th1 response increased in splenocytes of the anti-CD25 mAb group, whereas the Th1 and Th2 responses increased in splenocytes of the GAPDH and co-treated groups. Compared to that in the infected control group, granuloma diameter in the GAPDH and co-treated groups increased slightly, but there were no significant differences among the groups. Our results indicate that the protective effect of the GAPDH vaccines can be improved by decreasing Tregs and enhancing the Th1- and Th2-type immune responses. Therefore, anti-CD25 mAb and GAPDH might exert synergistic effects to clear parasites by decreasing the frequency of Tregs and increasing the Th1- and Th2-type immune responses.

Activity of serine proteases from Fasciola hepatica eggs in relation to pH and temperature

This study was conducted to analyse the serine protease of Fasciola hepatica eggs by specific substrates and inhibitors, and investigation of the effects of pH and temperature on proteases’ activity and stability. Adult worms were isolated from infected livers. After homogenisation, their protein levels were measured with the Bradford method. Total proteolytic activity of the Fasciola hepatica extract was evaluated with azocasein substrate at pH values from 2 to 12. N-benzoyl–arginine–p-nitroanilide (BApNA) trypsin and N-succinyl-alanine-alanine-prolin-phenylalanine-p-nitroanilide (SAAPFpNA) chymotrypsin substrates were used to measure specific protease activities. The effect of protease inhibitors phenylmethane sulfonyl fluoride (PMSF), pepsin, and ethylenediaminetetraacetic acid (EDTA) on these enzymes was evaluated. Estimation of optimum temperature and pH was performed in the temperature range of 10–90 °C and pH values from 2–12. The optimum pH activities for trypsin and chymotrypsin were at alkaline pH and for total proteolytic activity at acidic pH. The results using protease inhibitors showed that the eggs had serine protease activity. The optimum temperature activity of trypsin and chymotrypsin was 50 °C. These proteases were stable up to 40 °C. Due to the importance of pH and temperature in life cycle of Fasciola hepatica, these findings can be used for induction of some modifications in pH and preventing the activity of the enzyme for decrement of the efficacy of embryonic development and egg hatching of this zoonotic parasite.

The Effects of pH and Temperature on Cysteine Protease (Cathepsin B) Activity in Miracidia and Eggs of Fasciola hepatica

BACKGROUND

Fascioliasis is a worldwide zoonotic disease caused by the trematodes Fasciola hepatica in humans and animals. Proteases are essential for the survival of parasites and have important activities such as penetration, tissue migration, and egg hatching. This study was conducted to analyze cysteine protease of the miracidia and eggs of F. hepatica, and to assess the effects of pH and temperature on the proteases activity and stability.

METHODS

Adults F. hepatica were isolated from infected livers and were morphologically identified in 2018. Eggs collected from the adults and incubated in distilled water at 28 °C for 16 d to produce miracidia. The extract was collected from miracidia and eggs. A substrate for cathepsin B (Z-Arg-Arg-Pna) was used to assess the enzyme activity at different (2-12) pH levels. After homogenization, protein level was measured with Bradford method. Estimation of optimum temperature and pH was performed in the temperature range of 10-90 ° C and pH values from 2-12.

RESULTS

The highest activity of the miracidia and eggs enzyme extracts for Z-Arg-Arg-pNA was at pH 4. The miracidia extract was most stable at neutral pH and the eggs extract was most stable in acidic pH. The optimum temperature activity for both stages was 40 °C. These proteases were stable up to 40 °C.

CONCLUSION

Upon the importance of pH and temperature in the life cycle of F. hepatica, the current findings can be used for induction of some modifications in pH and preventing the activity of the enzymes for decrement of the efficacy of miracidia penetration into the intermediate snails and egg hatching of this zoonotic parasite.

Comparative study of excretory-secretory proteins released by Schistosoma mansoni-resistant, susceptible and naïve Biomphalaria glabrata

BACKGROUND

Schistosomiasis is a harmful neglected tropical disease caused by infection with Schistosoma spp., such as Schistosoma mansoni. Schistosoma must transition within a molluscan host to survive. Chemical analyses of schistosome-molluscan interactions indicate that host identification involves chemosensation, including naïve host preference. Proteomic technique advances enable sophisticated comparative analyses between infected and naïve snail host proteins. This study aimed to compare resistant, susceptible and naïve Biomphalaria glabrata snail-conditioned water (SCW) to identify potential attractants and deterrents.

METHODS

Behavioural bioassays were performed on S. mansoni miracidia to compare the effects of susceptible, F1 resistant and naïve B. glabrata SCW. The F1 resistant and susceptible B. glabrata SCW excretory-secretory proteins (ESPs) were fractionated using SDS-PAGE, identified with LC-MS/MS and compared to naïve snail ESPs. Protein-protein interaction (PPI) analyses based on published studies (including experiments, co-expression, text-mining and gene fusion) identified S. mansoni and B. glabrata protein interaction. Data are available via ProteomeXchange with identifier PXD015129.

RESULTS

A total of 291, 410 and 597 ESPs were detected in the susceptible, F1 resistant and naïve SCW, respectively. Less overlap in ESPs was identified between susceptible and naïve snails than F1 resistant and naïve snails. F1 resistant B. glabrata ESPs were predominately associated with anti-pathogen activity and detoxification, such as leukocyte elastase and peroxiredoxin. Susceptible B. glabrata several proteins correlated with immunity and anti-inflammation, such as glutathione S-transferase and zinc metalloproteinase, and S. mansoni sporocyst presence. PPI analyses found that uncharacterised S. mansoni protein Smp_142140.1 potentially interacts with numerous B. glabrata proteins.

CONCLUSIONS

This study identified ESPs released by F1 resistant, susceptible and naïve B. glabrata to explain S. mansoni miracidia interplay. Susceptible B. glabrata ESPs shed light on potential S. mansoni miracidia deterrents. Further targeted research on specific ESPs identified in this study could help inhibit B. glabrata and S. mansoni interactions and stop human schistosomiasis.

A comprehensive review of omics and host-parasite interplays studies, towards control of Opisthorchis viverrini infection for prevention of cholangiocarcinoma

Opisthorchis viverrini infection, opisthorchiasis, is a food-borne trematodiasis that is the main cause of cholangiocarcinoma, a bile duct cancer, in the Lower Mekong sub-region of Lao PDR, Cambodia, Vietnam, and Thailand. Despite extensive research on opisthorchiasis, the eradication of this disease has yet to be achieved. One of the major reasons for this failure is due to the multi-host life cycle of the parasite, which requires complex medical and public health interventions to eradicate. Another reason is due to a lack of knowledge of not only the interactions between the parasite and the human immune system, but also the interactions between the parasite and its various hosts during its complicated life cycle. Recent advances in various high-throughput omics technologies has allowed for the identification of key biomolecules crucial to the processes of parasitic transmission, and the identification of novel drug and/or vaccine targets. In this paper, omics studies dealing with O. viverrini host-parasite biology will be reviewed. In particular, there will be a focus on the strategies O. viverrini uses to trigger, evade, and manipulate the host's defense systems. Recently-identified biological molecules with potential as targets for interventions will also be reviewed. The results obtained from these omics approaches to analyzing O. viverrini and host interactions will be of great importance in the future when developing effective and sustainable medical and public health models for the prevention and control of opisthorchiasis and opisthorchiasis-induced CCA.

Anti-CTLA-4 monoclonal antibody improves efficacy of the glyceraldehyde-3-phosphate dehydrogenase protein vaccine against Schistosoma japonicum in mice

Schistosomiasis is a devastating disease caused by Schistosoma infection. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) has emerged as a candidate vaccine component against Schistosoma japonicum, but only confers partial protection. Cytotoxic T lymphocyte antigen-4 (CTLA-4) regulates T cell activation and shows negative effects on vaccine-induced immune protection; however, its potential influence on the protective effects of a GAPDH vaccine against S. japonicum and the underlying mechanism remain unclear. In this study, we established a mouse model of S. japonicum infection, and the mice were randomly divided into uninfected, infected control, anti-CTLA-4 monoclonal antibody (anti-CTLA-4 mAb), GAPDH, and GAPDH combined with anti-CTLA-4 mAb groups to compare the protective effects against infection and the consequent tissue damage. The worm reduction rate in the GAPDH-treated infected mice was 26.58%, which increased to 54.61% when combined with anti-CTLA-4 mAb. The frequency of regulatory T cells (Tregs) was significantly higher in the anti-CTLA-4 mAb group and was lower in the GAPDH group. However, both anti-CTLA-4 mAb and GAPDH elevated the levels of the cytokines IFN-γ, IL-2, IL-4, and IL-5 in the spleens of infected mice, and their combination further enhanced cytokine production. The diameter of egg granuloma in the anti-CTLA-4 mAb group and combined treatment group increased significantly compared to that of the other groups. These results suggest that anti-CTLA-4 mAb can be used as an adjuvant to enhance the immune protection of the GAPDH vaccine via inducing the Th1 immune response, although this comes at the cost of enhanced body injury.

Parasitic Infections and Cancer: A Status Report

There are many tropical parasitic infections that are still present public health problem in tropical medicine. Of interest, some diseases are proved for the relationship with carcinogenesis. Many cancers are proved for the etiopathogenesis due to parasitic infections. The well-known tropical parasitic infections that can induce carcinogenesis are opisthorchiasis, clonorchiasis, and schistosomiasis. To prevent parasitic infection related cancer is an important consideration in clinical oncology. The standard practice is the prevention of the infection, but the hope is the development of the new vaccines for cancer prevention. Here, the authors briefly review on the current status on the cancer vaccines against the three important tropical diseases that can result in cancers, opisthorchiasis, clonorchiasis, and schistosomiasis.

A secreted schistosome cathepsin B1 cysteine protease and acute schistosome infection induce a transient T helper 17 response

The natural history of schistosome infection in the mammalian host is determined by CD4⁺ T helper responses mounted against different parasite life cycle stages. A T helper 2 (T_H2) response to schistosome eggs is required for host survival and establishment of chronic infection. However, a T_H2 cell-derived cytokine also contributes to an immune milieu that is conducive to schistosome growth and development. Thus, the same responses that allow for host survival have been co-opted by schistosomes to facilitate parasite development and transmission, underscoring the significance of CD4⁺ T cell responses to both worms and eggs in the natural history of schistosome infection. Here we show that a cathepsin B1 cysteine protease secreted by schistosome worms not only induces T_H2 responses, but also T_H1 and T_H17 responses, by a mechanism that is dependent on the proteolytic activity of the enzyme. Further investigation revealed that, in addition to the expected T_H1 and T_H2 responses, acute schistosome infection also induces a transient T_H17 response that is rapidly down-regulated at the onset of oviposition. T_H17 responses are implicated in the development of severe egg-induced pathology. The regulation of worm-induced T_H17 responses during acute infection could therefore influence the expression of high and low pathology states as infection progresses.

Schistosomiasis, a neglected tropical disease caused by parasites of the genus Schistosoma, is prevalent throughout the developing world, with more than 230 million people infected. Left untreated, schistosome infection may cause relatively mild disease with some morbidity, or, in a minority of cases, result in severe pathology and death. These variable outcomes are recapitulated in animal models, where the natural history of schistosome infection is profoundly influenced by the responses of host CD4⁺ T helper cells. Type 2 CD4⁺ T cell (T_H2) responses, which allow for host survival by limiting pathology, have ironically also been co-opted by schistosomes to promote parasite development. On the other hand, T_H17 responses have been implicated in the development of severe pathology, in both experimentally infected animals and naturally infected humans. Here we show that a schistosome proteolytic enzyme (SmCB1), produced in the parasite gut and released into the bloodstream, induces both T_H2 and T_H17 responses by a mechanism that requires the enzyme’s inherent proteolytic activity. Further investigation revealed that acute schistosome infection also induces a transient T_H17 response that is rapidly down-regulated once parasite egg-laying commences. Regulation of T_H17 responses during early infection may help determine whether mild or severe pathology develops as the infection progresses.

Role of T lymphocytes and papain enzymatic activity in the protection induced by the cysteine protease against Schistosoma mansoni in mice

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Papain use deciphered the protection mechanism(s) of the schistosomiasis vaccine.

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Papain stimulation of innate immunity induced parasite egg attrition.

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Papain enzymatic and non-enzymatic sites activated T cells and innate immunity.

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IgG1 antibodies and liver uric acid and ARA levels correlated with protection.

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Identification of type 2 immunity-inducing cysteine peptidases motifs is required.

Papain, an experimental model protease, was used to decipher the protective mechanism(s) of the cysteine peptidase-based schistosomiasis vaccine. To examine the role of T lymphocytes, athymic nude (nu/nu) and immunocompetent haired (nu/+) mice were subcutaneously (sc) injected with 50 µg active papain two days before percutaneous exposure to 100 cercariae of Schistosoma mansoni. Highly significant (P < 0.005) reductions in worm burden required competent T lymphocytes, while significant increases (P < 0.05) of >80% in dead parasite ova in the small intestine were independent of T cell activity and likely relied on the innate immune axis. To investigate the role of enzymatic activity, immunocompetent mice were sc injected with 50 µg active or E-64-inactivated papain two days before exposure to cercariae. The reductions in worm burden were highly significant (P < 0.0001), reaching >65% and 40% in active and inactivated papain-treated mice, respectively. Similar highly significant (P < 0.0001) decreases of 85% in the viability of parasite ova in the small intestine occurred in both active and inactivated papain-treated mice. These findings indicated that immune responses elicited by one or more papain structural motifs are necessary and sufficient for induction of considerable parasite and egg attrition. Correlates of protection included IgG1-dominated antibody responses and increases in the levels of uric acid and arachidonic acid in the lung and liver upon parasite migration in these sites. Identification of the shared patterns or motifs in cysteine peptidases and evaluation of their immune protective potential will pave the way to the development of a safe, efficacious, storage-stable, and cost-effective schistosomiasis vaccine.

Serine proteases in schistosomes and other trematodes

Trematodes, also known as flukes, are phylogenetically ancient parasitic organisms. Due to their importance as human and veterinary parasites, their proteins have been investigated extensively as drug and vaccine targets. Among those, proteases, as crucial enzymes for parasite survival, are considered candidate molecules for anti-parasitic interventions. Surprisingly however, trematode serine proteases, in comparison with other groups of proteases, are largely neglected. Genes encoding serine proteases have been identified in trematode genomes in significant abundance, but the biological roles and biochemical functions of these proteases are poorly understood. However, increasing volumes of genomic and proteomic studies, and accumulated experimental evidence, indicate that this class of proteases plays a substantial role in host-parasite interactions and parasite survival. Here, we discuss in detail serine proteases at genomic and protein levels, and their known or hypothetical functions.

Schistosome vaccines: problems, pitfalls and prospects

Human schistosomiasis caused by parasitic flatworms of the genus Schistosoma remains an important public health problem in spite of concerted efforts at control. An effective vaccine would be a useful addition to control strategies that currently rely on chemotherapy, but such a product is not imminent. In this review, likely causes for the lack of progress are first considered. These include the strategies used by worms to evade the immune response, concepts that have misdirected the field, an emphasis on internal antigens, and the use of the laboratory mouse for vaccine testing. On a positive note, recent investigations on self-cure by the rhesus macaque offer the most promising context for vaccine development. The identification of proteins at the parasite-host interface, especially those of the esophageal glands involved in blood processing, has provided an entirely new category of vaccine candidates that merit evaluation.

Analysis of the interactome of Schistosoma mansoni histone deacetylase 8

BACKGROUND

Histone deacetylase 8 from Schistosoma mansoni (SmHDAC8) is essential to parasite growth and development within the mammalian host and is under investigation as a target for the development of selective inhibitors as novel schistosomicidal drugs. Although some protein substrates and protein partners of human HDAC8 have been characterized, notably indicating a role in the function of the cohesin complex, nothing is known of the partners and biological function of SmHDAC8.

METHODOLOGY/PRINCIPAL FINDINGS

We therefore employed two strategies to characterize the SmHDAC8 interactome. We first used SmHDAC8 as a bait protein in yeast two-hybrid (Y2H) screening of an S. mansoni cDNA library. This allowed the identification of 49 different sequences encoding proteins. We next performed co-immunoprecipitation (Co-IP) experiments on parasite extracts with an anti-SmHDAC8 antibody. Mass spectrometry (MS) analysis allowed the identification of 160 different proteins.

CONCLUSIONS/SIGNIFICANCE

SmHDAC8 partners are involved in about 40 different processes, included expected functions such as the cohesin complex, cytoskeleton organization, transcriptional and translational regulation, metabolism, DNA repair, the cell cycle, protein dephosphorylation, proteolysis, protein transport, but also some proteasome and ribosome components were detected. Our results show that SmHDAC8 is a versatile deacetylase, potentially involved in both cytosolic and nuclear processes.

Protection against Schistosoma haematobium infection in hamsters by immunization with Schistosoma mansoni gut-derived cysteine peptidases, SmCB1 and SmCL3

We examined the immunogenicity and protective potential of SmCB1 and SmCL3 cysteine peptidases, alone and in combination, in hamsters challenged with S. haematobium. For each of two independent experiments, eight Syrian hamsters were immunized twice with a three week-interval with 0 (controls), 20 µg SmCB1, 20 µg SmCL3, or 10 µg SmCB1 plus 10 µg SmCL3, and then percutaneously exposed eight weeks later to 100 S. haematobium cercariae. Hamsters from each group were assessed for humoral and whole blood culture cytokine responses on day 10 post challenge infection, and examined for parasitological parameters 12 weeks post infection. At day 10 post-infection we found that SmCB1 and SmCL3 elicited low antibody titres and weak but polarized cytokine type 2 responses. Nevertheless, both cysteine peptidases, alone or in combination, evoked reproducible and highly significant reduction in challenge worm burden (>70%, P < 0.02) as well as a significant reduction in worm egg counts and viability. The data support our previous findings and show that S. mansoni cysteine peptidases SmCB1 and SmCL3 are efficacious adjuvant-free vaccines that induce protection in mice and hamsters against both S. mansoni and S. haematobium.

Physiological functions and pathogenic potential of uric acid: A review

Uric acid is synthesized mainly in the liver, intestines and the vascular endothelium as the end product of an exogenous pool of purines, and endogenously from damaged, dying and dead cells, whereby nucleic acids, adenine and guanine, are degraded into uric acid. Mentioning uric acid generates dread because it is the established etiological agent of the severe, acute and chronic inflammatory arthritis, gout and is implicated in the initiation and progress of the metabolic syndrome. Yet, uric acid is the predominant anti-oxidant molecule in plasma and is necessary and sufficient for induction of type 2 immune responses. These properties may explain its protective potential in neurological and infectious diseases, mainly schistosomiasis. The pivotal protective potential of uric acid against blood-borne pathogens and neurological and autoimmune diseases is yet to be established.