A mucosally administered recombinant fusion protein vaccine against schistosomiasis protecting against immunopathology and infection

Intranasal immunization of mice with chimera of Salmonella Typhi protein elicits protective intestinal immunity

Development of safe, highly effective and affordable enteric fever vaccines is a global health priority. Live, oral typhoid vaccines induce strong mucosal immunity and long-term protection, but safety remains a concern. In contrast, efficacy wears off rapidly for injectable, polysaccharide-based vaccines, which elicit poor mucosal response. We previously reported Salmonella Typhi outer membrane protein, T2544 as a potential candidate for bivalent (S. Typhi and S. Paratyphi A) vaccine development. Here, we show that intranasal immunization with a subunit vaccine (chimera of T2544 and cholera toxin B subunit) induced strong systemic and intestinal mucosal immunity and protection from S. Typhi challenge in a mouse model. CTB-T2544 augmented gut-homing receptor expression on lymphocytes that produced Th1 and Th17 cytokines, secretory IgA in stool that inhibited bacterial motility and epithelial attachment, antibody recall response and affinity maturation with increased number of follicular helper T cells and CD4+ central and effector memory cells.

Phosphoproteomics analysis of male and female Schistosoma mekongi adult worms

Schistosoma mekongi is one of the major causative agents of human schistosomiasis in Southeast Asia. Praziquantel is now the only drug available for treatment and there are serious concerns about parasite resistance to it. Therefore, a dataset of schistosome targets is necessary for drug development. Phosphorylation regulates signalling pathways to control cellular processes that are important for the parasite's growth and reproduction. Inhibition of key phosphoproteins may reduce the severity of schistosomiasis. In this research, we studied the phosphoproteomes of S. mekongi male and female adult worms by using computational and experimental approaches. Using a phosphoproteomics approach, we determined that 88 and 44 phosphoproteins were male- and female-biased, respectively. Immunohistochemistry using anti-phosphoserine antibodies demonstrated phosphorylation on the tegument and muscle of male S. mekongi worms and on the vitelline gland and gastrointestinal tract of female worms. This research revealed S. mekongi sex-dependent phosphoproteins. Our findings provide a better understanding of the role of phosphorylation in S. mekongi and could be integrated with information from other Schistosoma species to facilitate drug and vaccine development.

Treatment with P28GST, a schistosome-derived enzyme, after acute colitis induction in mice: Decrease of intestinal inflammation associated with a down regulation of Th1/Th17 responses

Background

P28GST, a 28Kd glutathione S-transferase enzymatic protein derived from a schistosome helminth prevents experimental colitis when administered subcutaneously in the presence of adjuvant by decreasing pro-inflammatory Th1/Th17 response. Given the antioxidant properties of P28GST, we evaluated its anti-inflammatory potential when administered locally after colitis induction in the absence of adjuvant.

Methods

Colitis was induced in BALB/c mice by rectal administration of TNBS, followed by two intraperitoneal injections of P28GST at day 1 and day 2. Mice were sacrificed 48h after TNBS administration and evaluated for macroscopic and histological scores, myeloperoxidase (MPO) quantification and cytokine messenger RNA expression in the colonic tissues.

Results

Both clinical and histological scores significantly decreased in mice treated with P28GST at 5 or 50μg/kg when compared to vehicle- treated mice. A significant reduction of MPO was detected in colonic tissues from P28GST–treated mice, similarly to mice treated with methylprednisolone as the reference treatment. Pro-inflammatory cytokines TNF, IL-1β, and IL-6, mRNA as well as serum levels were down-regulated in mice colonic tissues treated with P28GST at 5 or 50μg/kg. In addition, a significant decrease of mRNA expression levels of T-bet, and ROR-γ, respective markers of Th1 and Th17 cells was observed. Whereas no significant effect was detected on Gata3 mRNA, a marker of Th2 cells, the Arg/iNOS mRNA levels significantly increased in P28GST-treated mice, suggesting the induction of M2 macrophages.

Conclusions

These findings provide evidence that P28GST injected locally after colitis induction induces a potent decrease of colitis inflammation in mice, associated to downregulation of Th1/Th17 response, and induction of anti-inflammatory alternatively activated macrophages.

Safety and efficacy of the rSh28GST urinary schistosomiasis vaccine: A phase 3 randomized, controlled trial in Senegalese children

Background

Urinary schistosomiasis, the result of infection by Schistosoma haematobium (Sh), remains a major global health concern. A schistosome vaccine could represent a breakthrough in schistosomiasis control strategies, which are presently based on treatment with praziquantel (PZQ). We report the safety and efficacy of the vaccine candidate recombinant 28-kDa glutathione S-transferase of Sh (rSh28GST) designated as Bilhvax, in a phase 3 trial conducted in Senegal.

Methods and findings

After clearance of their ongoing schistosomiasis infection with two doses of PZQ, 250 children aged 6–9 years were randomized to receive three subcutaneous injections of either rSh28GST/Alhydrogel (Bilhvax group) or Alhydrogel alone (control group) at week 0 (W0), W4, and W8 and then a booster at W52 (one year after the first injection). PZQ treatment was given at W44, according to previous phase 2 results. The primary endpoint of the analysis was efficacy, evaluated as a delay of recurrence of urinary schistosomiasis, defined by a microhematuria associated with at least one living Sh egg in urine from baseline to W152. During the 152-week follow-up period, there was no difference between study arms in the incidence of serious adverse events. The median follow-up time for subjects without recurrence was 22.9 months for the Bilhvax group and 18.8 months for the control group (log-rank p = 0.27). At W152, 108 children had experienced at least one recurrence in the Bilhvax group versus 112 in the control group. Specific immunoglobulin (Ig)G1, IgG2, and IgG4, but not IgG3 or IgA titers, were increased in the vaccine group.

Conclusions

While Bilhvax was immunogenic and well tolerated by infected children, a sufficient efficacy was not reached. The lack of effect may be the result of several factors, including interference by individual PZQ treatments administered each time a child was found infected, or the chosen vaccine-injection regimen favoring blocking IgG4 rather than protective IgG3 antibodies. These observations contrasting with results obtained in experimental models will help in the design of future trials.

Trial registration

ClinicalTrials.gov NCT 00870649

Vaccines represent an attractive tool in the fight against schistosomiasis. Pre-clinical immunization studies with the schistosome enzyme 28 kDa glutathione S-transferase (28GST) have shown a significant reduction of schistosome egg production and subsequent pathology. The objective of the present phase 3 trial was to assess the efficacy and safety of vaccination with the recombinant 28GST of Schistosoma haematobium (rSh28GST) named Bilhvax, in infected school children. After Praziquantel treatment before inclusion and three administrations of rSh28GST at one month interval as primo-vaccination, subjects received a boost injection one year after the first administration. The efficacy was evaluated as a delay of recurrence of urinary schistosomiasis. While immunological analysis showed that Bilhvax induced a consistent immune response characterized by antibodies able to inhibit 28GST enzymatic activity, the efficacy endpoint was not reached. This lack of significant effect may be due to the negative conjunction of a too challenging recurrence criterion associated with safety measures ensuring repeated PZQ treatment. The control of these main factors will be essential for the subsequent trials and must provide evidence of the Bilhvax efficacy as a safe vaccine against uro-genital schistosomiasis.

Immunomodulation with Enterotoxins for the Generation of Secretory Immunity or Tolerance: Applications for Oral Infections

The heat-labile enterotoxins, such as cholera toxin (CT), and the labile toxins types I and II (LT-I and LT-II) of Escherichia coli have been extensively studied for their immunomodulatory properties, which result in the enhancement of immune responses. Despite superficial similarity in structure, in which a toxic A subunit is coupled to a pentameric binding B subunit, different toxins have different immunological properties. Administration of appropriate antigens admixed with or coupled to these toxins by oral, intranasal, or other routes in experimental animals induces mucosal IgA and circulating IgG antibodies that have protective potential against a variety of enteric, respiratory, or genital infections. These include the generation of salivary antibodies that may protect against colonization with mutans streptococci and the development of dental caries. However, exploitation of these adjuvants for human use requires an understanding of their mode of action and the separation of their desirable immunomodulatory properties from their toxicity. Recent findings have revealed that adjuvant action is not critically dependent upon the enzymic activity of the A subunits, and that the isolated B subunits may exert different effects on cells of the immune system than do the intact toxins. Interaction of the toxins with immunocompetent cells is not exclusively dependent upon their conventional ganglioside receptors. Immunomodulatory effects have been observed on dendritic cells, macrophages, CD4+ and CD8+ T-cells, and B-cells. Numerous factors—including the precise form of the toxin adjuvant, properties of the antigen, whether and how they are coupled, route of administration, and species of animal model—affect the outcome, whether this is enhanced humoral and cellular immunity, or specific induced tolerance toward the antigen.

An overview on different aspects of hypodermosis: Current status and future prospects

Livestock plays a vital role in economic development of a nation and is being used in agriculture for draft power, production of farmyard manure as well as milk and meat production. Bovine hypodermosis is the top culprit among all parasitic infections across the world. Hypodermosis is an endemic disease in the mountainous areas/plain areas and is regularly observed in the northern hemisphere of the globe affecting cattle, deer, yaks and buffaloes. There is a wide variation in geographical distribution of Hypoderma spp. during the years 1945-2015. The manuscript includes a geospatial study that tries to maps the global distribution of hypodermosis in different areas of the world in order to detect hotspots or endemic areas that may be a potential source for disease spread. This information's are very useful to predict the potential high risk areas that are prone to disease outbreak. The present review aims to evaluate the global distribution, molecular discrimination, diagnostics and vaccination of hypodermosis, focusing on its current status and future perspectives towards the management of the disease and its control strategies.

The schistosome glutathione S-transferase P28GST, a unique helminth protein, prevents intestinal inflammation in experimental colitis through a Th2-type response with mucosal eosinophils

Intestinal helminth parasites are potent inducers of T helper type 2 (Th2) response and have a regulatory role, notably on intestinal inflammation. As infection with schistosomes is unlikely to provide a reliable treatment of inflammatory bowel diseases, we have investigated the beneficial effect of a schistosome enzymatic protein, the 28-kDa glutathione S-transferase (P28GST), on the modulation of disease activity and immune responses in experimental colitis. Our results showed that immunization with recombinant P28GST is at least as efficient as established schistosome infection to reduce colitis lesions and expression of pro-inflammatory cytokines. Considering underlying mechanisms, the decrease of inflammatory parameters was associated with the polarization of the immune system toward a Th2 profile, with local and systemic increases of interleukin (IL)-13 and IL-5. Dense eosinophil infiltration was observed in the colons of P28GST-immunized rats and mice. Depletion of eosinophils by treatment with an anti-Siglec-F monoclonal antibody and use of IL-5-deficient mice led to the loss of therapeutic effect, suggesting the crucial role for eosinophils in colitis prevention by P28GST. These findings reveal that immunization with P28GST, a unique recombinant schistosome enzyme, ameliorates intestinal inflammation through eosinophil-dependent modulation of harmful type 1 responses, representing a new immuno-regulatory strategy against inflammatory bowel diseases.

Protective immunity against Naegleria fowleri infection on mice immunized with the rNfa1 protein using mucosal adjuvants

The free-living amoeba, Naegleria fowleri, causes a fatal disease called primary amoebic meningoencephalitis (PAM) in humans and experimental animals. Of the pathogenic mechanism of N. fowleri concerning host tissue invasion, the adherence of amoeba to hose cells is the most important. We previously cloned the nfa1 gene from N. fowleri. The protein displayed immunolocalization in the pseudopodia, especially the food-cups structure, and was related to the contact-dependent mechanism of the amoebic pathogenicity in N. fowleri infection. The cholera toxin B subunit (CTB) and Escherichia coli heat-labile enterotoxin B subunit (LTB) have been used as potent mucosal adjuvants via the parenteral route of immunization in most cases. In this study, to examine the effect of protective immunity of the Nfa1 protein for N. fowleri infection with enhancement by CTB or LTB adjuvants, intranasally immunized BALB/c mice were infected with N. fowleri trophozoites for the development of PAM. The mean time to death of mice immunized with the Nfa1 protein using LTB or CTB adjuvant was prolonged by 5 or 8 days in comparison with that of the control mice. In particular, the survival rate of mice immunized with Nfa1 plus CTB was 100% during the experimental period. The serum IgG levels were significantly increased in mice immunized with Nfa1 protein plus CTB or LTB adjuvants. These results suggest that the Nfa1 protein, with CTB or LTB adjuvants, induces strong protective immunity in mice with PAM due to N. fowleri infection.

The immunobiology of myiasis infections--whatever happened to vaccination?

The current state of myiasis vaccine technologies are reviewed mainly in the primary research genera of Lucilia and Hypoderma. The importance of myiasis flies as primary causes of morbidity and mortality in agricultural species and man has not diminished despite the existence of good control strategies. However, the development of vaccines against myiasis infections has been relatively quiescent for more than 10 years despite the rapid development of genomic and proteomic analysis and of skills in data interpretation. The value of vaccine research in an era of chemical primacy is analysed. In fact, recent findings of drug resistance and the impact of animal welfare concerns should mean a renewed interest in alternative controls. The reasons that this has not been true to date are explored and new possibilities discussed.

Immunization with the recombinant Cholera toxin B fused to Fimbria 2 protein protects against Bordetella pertussis infection

This study examined the immunogenic properties of the fusion protein fimbria 2 of Bordetella pertussis (Fim2)—cholera toxin B subunit (CTB) in the intranasal murine model of infection. To this end B. pertussis Fim2 coding sequence was cloned downstream of the cholera toxin B subunit coding sequence. The expression and assembly of the fusion protein into pentameric structures (CTB-Fim2) were evaluated by SDS-PAGE and monosialotetrahexosylgaglioside (GM1-ganglioside) enzyme-linked immunosorbent assay (ELISA). To evaluate the protective capacity of CTB-Fim2, an intraperitoneal or intranasal mouse immunization schedule was performed with 50 μg of CTB-Fim2. Recombinant (rFim2) or purified (BpFim2) Fim2, CTB, and phosphate-buffered saline (PBS) were used as controls. The results showed that mice immunized with BpFim2 or CTB-Fim2 intraperitoneally or intranasally presented a significant reduction in bacterial lung counts compared to control groups (P < 0.01 or P < 0.001 , resp.). Moreover, intranasal immunization with CTB-Fim2 induced significant levels of Fim2-specific IgG in serum and bronchoalveolar lavage (BAL) and Fim2-specific IgA in BAL. Analysis of IgG isotypes and cytokines mRNA levels showed that CTB-Fim2 results in a mixed Th1/Th2 (T-helper) response. The data presented here provide support for CTB-Fim2 as a promising recombinant antigen against Bordetella pertussis infection.

Receptor Binding by Cholera Toxin B-Subunit and Amino Acid Modification Improves Minimal Peptide Immunogenicity

We increase our understanding of augmenting a cellular immune response, by using an HIV-1 protease-derived epitope (PR_75–84), and variants thereof, coupled to the C-terminal, of the B subunit of cholera toxin (CTB). Fusion proteins were used for immunizations of HLA-A0201 transgenic C57BL/6 mice. We observed different capacities to elicit a cellular immune response by peptides with additions of five to ten amino acids to the PR epitope. There was a positive correlation between the magnitude of the elicited cellular immune response and the capacity of the fusion protein to bind GM-1. This binding capacity is affected by its ability to form natural pentamers of CTB. Our results suggest that functional CTB pentamers containing a foreign amino acid-modified epitope is a novel way to overcome the limited cellular immunogenicity of minimal peptide antigens. This way of using a functional assay as readout for improved cellular immunogenicity might become highly valuable for difficult immunogens such as short peptides (epitopes).

Functionally fused antibodies--a novel adjuvant fusion system

Antibodies capable of recognizing key molecular targets isolated e.g. by phage display technology have been used in the pursuit of new and improved therapies for prevalent human diseases. These approaches often take advantage of non-immunogenic antibody fragments to achieve specific toxin-, radioactivity- or effector-domain delivery. There is now a growing interest in using anti-idiotypic antibodies or other antigen mimics to induce potent immune responses against antigen structures in question. We have earlier reported on the functional rescue of antibodies that are active when fused to the phage, but inactive as soluble protein [Jensen, K.B., Larsen, M., Pedersen, J.S., Christensen, P.A., Alvarez-Vallina, L., Goletz, S., Clark, B.F. and Kristensen, P. (2002) Functional improvement of antibody fragments using a novel phage coat protein III fusion system. Biochem. Biophys. Res. Commun. 298, 566-73.]. The rescue was accomplished by maintaining the fusion between the antibody fragment and portions of the filamentous bacteriophage coat protein 3, as present in the original antibody-displaying phage. In the present study, we have applied this system in an attempt to improve immunogenicity of anti-idiotypic antibodies isolated by phage display. Here we demonstrate that by preserving linkage between phage antibody and the N-terminal domain of phage coat protein 3, we induce multimerization of the antibody fragments, and improve their immunogenicity. This immunization approach allows induction of anti-idiotypic antibodies in mice, and facilitates the use of antibodies that are non-functional as non-fused soluble protein.

Current status of vaccines for schistosomiasis

Schistosomiasis, caused by trematode blood flukes of the genus Schistosoma, is recognized as the most important human helminth infection in terms of morbidity and mortality. Infection follows direct contact with freshwater harboring free-swimming larval (cercaria) forms of the parasite. Despite the existence of the highly effective antischistosome drug praziquantel (PZQ), schistosomiasis is spreading into new areas, and although it is the cornerstone of current control programs, PZQ chemotherapy does have limitations. In particular, mass treatment does not prevent reinfection. Furthermore, there is increasing concern about the development of parasite resistance to PZQ. Consequently, vaccine strategies represent an essential component for the future control of schistosomiasis as an adjunct to chemotherapy. An improved understanding of the immune response to schistosome infection, both in animal models and in humans, suggests that development of a vaccine may be possible. This review considers aspects of antischistosome protective immunity that are important in the context of vaccine development. The current status in the development of vaccines against the African (Schistosoma mansoni and S. haematobium) and Asian (S. japonicum) schistosomes is then discussed, as are new approaches that may improve the efficacy of available vaccines and aid in the identification of new targets for immune attack.

Experimental vaccines in animal models for schistosomiasis

Considerable morbidity and mortality results from the affliction of an estimated 200 million people worldwide by several species of schistosomes; 779 million are exposed to the disease in 74 different countries. Even though anti-parasitic drugs and other control measures, including public hygiene and snail control are available, the advent of an effective vaccine still remains the most potentially powerful means for the control of this disease. The putative vaccine could be administered to small children prior to the time when their contact with infected water is maximal, so as to prevent severe infection in the subsequent years. This review attempts to summarize the status of schistosome vaccine development with special emphasis on functionally important vaccine candidates. The importance of utilizing both murine and nonhuman primate models as a prerequisite for clinical trials is discussed.

Vaccine potential of inclusion bodies containing cysteine proteinase of Fasciola hepatica in calves and lambs experimentally challenged with metacercariae of the fluke

Despite intensive research efforts, progress in the development of effective anti-Fasciola hepatica vaccine has not been satisfactory. However, it has been found that cysteine proteinases of F. hepatica are very important candidates for a vaccine antigen because of their role in fluke biology and in the host-parasite relationship. In our previous experiments we found that recombinant cysteine proteinase which we have cloned from adult F. hepatica (CPFhW) can protect rats against the liver fluke infection when administered intramuscularly or when given intranasally in the form of cDNA. In the present experiments we aimed to evaluate the protectivity of the mucosal vaccination in calves and lambs with inclusion bodies containing recombinant CPFhW using different vaccination doses and various sites of antigen delivery. Female calves vaccinated intranasally with two doses of 300 microg of the recombinant CPFhW showed 54.2% protection against the subsequent challenge of 400 metacercariae (mc). Flukes which developed in vaccinated calves showed a reduction of reproductive potential. Male Corriedale lambs vaccinated at the age of 4 months demanded three doses of the antigen to gain 56.5% of protection to a challenge with 250 mc of F. hepatica. Vaccinated animals showed significantly lower blood eosinophil counts. No correlation was found between serum and mucosal IgG or IgA reacting with F. hepatica ES antigens and the protection level.

Enteral vaccination of rats against Fasciola hepatica using recombinant cysteine proteinase (cathepsin L1)

Cysteine proteinases released by Fasciola hepatica play a key role in parasite feeding, migration through host tissues and in immune evasion. Hence, a recombinant cysteine proteinase (CPFhW) expressed as inclusion bodies in Escherichia coli was used for enteral vaccination of rats against fasciolosis. We managed to activate this proteinase and found it to have cathepsin L1-like substrate preference. Enteral vaccination of rats induced a 78-80% protection against challenge with fluke metacercariae (mc). The immunised rats showed clear immunological response. The challenge with mc caused a remarkable infiltration of eosinophils into the peritoneal cavity of both the vaccinated rats and challenge control rats. However, CD8+ and CD4+ lymphocytes appeared in significantly higher numbers in the peritoneal fluid of vaccinated rats than in controls.

Heteropentameric cholera toxin B subunit chimeric molecules genetically fused to a vaccine antigen induce systemic and mucosal immune responses: a potential new strategy to target recombinant vaccine antigens to mucosal immune systems

Noninvasive mucosal vaccines are attractive alternatives to parenteral vaccines. Although the conjugation of vaccine antigens with the B subunit of cholera toxin (CTB) is one of the most promising strategies for vaccine delivery to mucosal immune systems, the molecule cannot tolerate large-protein fusion, as it severely impairs pentamerization and loses affinity for GM1-ganglioside. Here we report a new strategy, in which steric hindrance between CTB-antigen fusion subunits is significantly reduced through the integration of unfused CTB "molecular buffers" into the pentamer unit, making them more efficiently self-assemble into biologically active pentamers. In addition, the chimeric protein took a compact configuration, becoming small enough to be secreted, and one-step affinity-purified proteins, when administered through a mucosal route, induced specific immune responses in mice. Since our results are not dependent on the use of a particular expression system or vaccine antigen, this strategy could be broadly applicable to bacterial enterotoxin-based vaccine design.

Schistosomes: the road from host-parasite interactions to vaccines in clinical trials

Insights over recent years into the interactions between helminths, including schistosomes, and the immune system have generated new concepts in immunology and significant advances in vaccine strategies. Here, we report recent advances that substantially increase our understanding of the nature of the host innate and adaptive responses to schistosomes and on strategies elaborated by the parasite to manipulate such responses. We also describe the long road that has allowed us to move from the identification of an anti-schistosome vaccine candidate, a 28kDa glutathione-S-transferase, to its recent evaluation in human clinical trials.

Novel binding site identified in a hybrid between cholera toxin and heat-labile enterotoxin: 1.9 A crystal structure reveals the details

A hybrid between the B subunits of cholera toxin and Escherichia coli heat-labile enterotoxin has been described, which exhibits a novel binding specificity to blood group A and B type 2 determinants. In the present investigation, we have determined the crystal structure of this protein hybrid, termed LCTBK, in complex with the blood group A pentasaccharide GalNAcalpha3(Fucalpha2)Galbeta4(Fucalpha3)GlcNAcbeta, confirming not only the novel binding specificity but also a distinct new oligosaccharide binding site. Binding studies revealed that the new specificity can be ascribed to a single mutation (S4N) introduced into the sequence of Escherichia coli heat-labile enterotoxin. At a resolution of 1.9 A, the new binding site is resolved in excellent detail. Main features include a complex network of water molecules, which is well preserved by the parent toxins, and an unexpectedly modest contribution to binding by the critical residue Asn4, which interacts with the ligand only via a single water molecule.

Current status and future prospects for a vaccine against schistosomiasis

Schistosomiasis remains an intractable problem in many parts of the world. Whereas the schistosome parasites cause little in the way of disease, their eggs become trapped in tissues of the host and elicit powerful and potentially damaging immune responses that are responsible for the pathology. Despite nearly four decades of effort there is still no effective vaccine against schistosomiasis, although a single vaccine candidate is undergoing clinical trials at present. Animal models have revealed much about disease progression and pathology. However, problems remain in identifying appropriate protective antigens to elicit immune responses that will attack the parasite but will not cross-react with egg antigens and thus increase the chance of developing severe chronic disease in individuals that have already been infected. This review summarizes the life-cycle of the parasite, current knowledge of pathogenesis and acquired immunity based on animal studies and observations in humans and the status of efforts in the vaccine development field.

Antioxidant enzymes in intramolluscan Schistosoma mansoni and ROS-induced changes in expression

Killing of intramolluscan schistosomes by host haemocytes is mediated by reactive oxygen metabolites. Hence, defence against oxidative damage is essential for the parasite to survive. In this study, expression of three key antioxidant enzymes, superoxide dismutase (EC 1.15.1.1), glutathione peroxidase (EC 1.11.1.9) and glutathione-S-transferase (EC 2.5.1.18) was determined in Schistosoma mansoni miracidia, sporocysts and cercariae. Stage-dependent expression of these enzymes was shown to be regulated at the transcriptional level. Second, the influence on enzyme expression of reactive oxygen species (ROS) and of haemocytes from schistosome-resistant and -susceptible host snails was determined. Generation of ROS by xanthine/xanthine oxidase resulted in increased transcript levels for all three enzymes. Addition of hydrogen peroxide induced a significantly increased expression of GPx and SOD but not GST. Snail haemocytes induced an up-regulation of SOD and GPx at 12 and 18 h post-exposure, respectively. Susceptible haemocytes elicited a stronger induction of transcript expression than resistant haemocytes. After 36-48 h, SOD remained up-regulated in sporocysts encapsulated by haemocytes from susceptible hosts, whereas a down-regulation of SOD and GPx occurred in schistosomes encapsulated by haemocytes from resistant snails. These observations indicate that schistosomes express elevated levels of antioxidant enzymes in interaction with haemocytes from susceptible snail hosts in which they survive. On the other hand, haemocytes of resistant snails may interfere with reactive oxygen detoxification via down-regulation of schistosome antioxidant enzymes, thus shifting the balance towards parasite killing.

Cloning, expression and partial characterization of a Haemaphysalis longicornis and a Rhipicephalus appendiculatus glutathione S-transferase

The ticks Haemaphysalis longicornis and Rhipicephalus appendiculatus are important parasites worldwide. The current method for control of cattle ticks involves the use of chemicals. Nevertheless, parasite resistance is an ever increasing global problem. Glutathione S-transferases (GSTs) play a central role in detoxication of xenobiotic and endogenous compounds. Several authors have noted that an increase in GST activity is associated with resistance to insecticides and acaricides. In the present study, we report the cloning and expression of GST cDNAs from H. longicornis and R. appendiculatus. In addition, we determine the effect of three acaricides (ethion, deltamethrin and diazinon) on the enzymatic activity of rGSTs.

Mucosal immunisation and adjuvants: a brief overview of recent advances and challenges

Mucosal immunisation may be used both to prevent mucosal infections through the activation of anti-microbial immunity and to treat selected autoimmune, allergic or infectious-immunopathological disorders through the induction of antigen-specific tolerance. The development of mucosal vaccines, whether for prevention of infectious diseases or for immunotherapy, requires antigen delivery and adjuvant systems that can efficiently help to present vaccine or immunotherapy antigens to the mucosal immune system. Promising advances have recently been made in the design of more efficient mucosal adjuvants based on detoxified bacterial toxin derivatives or CpG motif-containing DNA, and perhaps even more striking progress has been done in the use of virus-like particles as mucosal delivery systems for vaccines and of cholera toxin B subunit as antigen vector for immunotherapeutic tolerance induction. However, it is a memento that two recently developed mucosal vaccines for human use against rotavirus diarrhoea and influenza were withdrawn after a short period in the market because of adverse reactions among the vaccinees, thus emphasising the difficult and challenging task also for mucosal immunisation of combining vaccine and adjuvant efficacy with safety and acceptability.