Active immunization of mice with Schistosoma mansoni worm membrane antigens enhances efficacy of praziquantel

Can antibody conjugated nanomicelles alter the prospect of antibody targeted therapy against schistosomiasis mansoni?

BACKGROUND

CLA (conjugated linoleic acid)-mediated activation of the schistosome tegument-associated sphingomyelinase and consequent disruption of the outer membrane might allow host antibodies to access the apical membrane antigens. Here, we investigated a novel approach to enhance specific antibody delivery to concealed surface membrane antigens of Schistosoma mansoni utilising antibody-conjugated-CLA nanomicelle technology.

METHODOLOGY/PRINCIPAL FINDINGS

We invented and characterised an amphiphilic CLA-loaded whey protein co-polymer (CLA-W) as an IV injectable protein nanocarrier. Rabbit anti-Schistosoma mansoni infection (anti-SmI) and anti-Schistosoma mansoni alkaline phosphatase specific IgG antibodies were purified from rabbit sera and conjugated to the surface of CLA-W co-polymer to form antibody-conjugated-CLA-W nanomicelles (Ab-CLA-W). We investigated the schistosomicidal effects of CLA-W and Ab-CLA-W in a mouse model of Schistosoma mansoni against early and late stages of infection. Results showed that conjugation of nanomicelles with antibodies, namely anti-SmI, significantly enhanced the micelles' schistosomicidal and anti-pathology activities at both the schistosomula and adult worm stages of the infection resulting in 64.6%-89.9% reductions in worm number; 72.5-94% and 66.4-85.2% reductions in hepatic eggs and granulomas, respectively. Treatment induced overall improvement in liver histopathology, reducing granuloma size and fibrosis and significantly affecting egg viability. Indirect immunofluorescence confirmed CLA-W-mediated antigen exposure on the worm surface. Electron microscopy revealed extensive ultrastructural damage in worm tegument induced by anti-SmI-CLA-W.

CONCLUSION/SIGNIFICANCE

The novel antibody-targeted nano-sized CLA delivery system offers great promise for treatment of Schistosoma mansoni infection and control of its transmission. Our in vivo observations confirm an immune-mediated enhanced effect of the schistosomicidal action of CLA and hints at the prospect of nanotechnology-based immunotherapy, not only for schistosomiasis, but also for other parasitic infections in which chemotherapy has been shown to be immune-dependent. The results propose that the immunodominant reactivity of the anti-SmI serum, Schistosoma mansoni fructose biphosphate aldolase, SmFBPA, merits serious attention as a therapeutic and vaccine candidate.

Immunomics-Guided Antigen Discovery for Praziquantel-Induced Vaccination in Urogenital Human Schistosomiasis

Despite the enormous morbidity attributed to schistosomiasis, there is still no vaccine to combat the disease for the hundreds of millions of infected people. The anthelmintic drug, praziquantel, is the mainstay treatment option, although its molecular mechanism of action remains poorly defined. Praziquantel treatment damages the outermost surface of the parasite, the tegument, liberating surface antigens from dying worms that invoke a robust immune response which in some subjects results in immunologic resistance to reinfection. Herein we term this phenomenon Drug-Induced Vaccination (DIV). To identify the antigenic targets of DIV antibodies in urogenital schistosomiasis, we constructed a recombinant proteome array consisting of approximately 1,000 proteins informed by various secretome datasets including validated proteomes and bioinformatic predictions. Arrays were screened with sera from human subjects treated with praziquantel and shown 18 months later to be either reinfected (chronically infected subjects, CI) or resistant to reinfection (DIV). IgG responses to numerous antigens were significantly elevated in DIV compared to CI subjects, and indeed IgG responses to some antigens were completely undetectable in CI subjects but robustly recognized by DIV subjects. One antigen in particular, a cystatin cysteine protease inhibitor stood out as a unique target of DIV IgG, so recombinant cystatin was produced, and its vaccine efficacy assessed in a heterologous Schistosoma mansoni mouse challenge model. While there was no significant impact of vaccination with adjuvanted cystatin on adult worm numbers, highly significant reductions in liver egg burdens (45-55%, P<0.0001) and intestinal egg burdens (50-54%, P<0.0003) were achieved in mice vaccinated with cystatin in two independent trials. This study has revealed numerous antigens that are targets of DIV antibodies in urogenital schistosomiasis and offer promise as subunit vaccine targets for a drug-linked vaccination approach to controlling schistosomiasis.

Effect of Praziquantel on Schistosoma mekongi Proteome and Phosphoproteome

Schistosoma mekongi causes schistosomiasis in southeast Asia, against which praziquantel (PZQ) is the only treatment option. PZQ resistance has been reported, thus increasing the requirement to understand mechanism of PZQ. Herein, this study aimed to assess differences in proteome and phosphoproteome of S. mekongi after PZQ treatment for elucidating its action. Furthermore, key kinases related to PZQ effects were predicted to identify alternative targets for novel drug development. Proteomes of S. mekongi were profiled after PZQ treatment at half maximal inhibitory concentration and compared with untreated worms. A total of 144 proteins were differentially expressed after treatment. In parallel, immunohistochemistry indicated a reduction of phosphorylation, with 43 phosphoproteins showing reduced phosphorylation, as identified by phosphoproteomic approach. Pathway analysis of mass spectrometric data showed that calcium homeostasis, worm antigen, and oxidative stress pathways were influenced by PZQ treatment. Interestingly, two novel mechanisms related to protein folding and proteolysis through endoplasmic reticulum-associated degradation pathways were indicated as a parasiticidal mechanism of PZQ. According to kinase–substrate predictions with bioinformatic tools, Src kinase was highlighted as the major kinase related to the alteration of phosphorylation by PZQ. Interfering with these pathways or applying Src kinase inhibitors could be alternative approaches for further antischistosomal drug development.

Co-administration of silymarin elevates the therapeutic effect of praziquantel through modulation of specific antibody profiles, Th1/Th2/Tregs cytokines and down-regulation of fibrogenesis in mice with Mesocestoides vogae (Cestoda) infection

Silymarin (SIL) represents a natural mixture of polyphenols showing an array of health benefits. The present study, carried out on a model cestode infection induced by Mesocestoides vogae tetrathyridia in the ICR strain of mice, was aimed at investigating the impact of SIL as adjunct therapy on the activity of praziquantel (PZQ) in relation to parasite burden, immunity and liver fibrosis within 20 days post-therapy. In comparison with PZQ alone, co-administration of SIL and PZQ stimulated production of total IgG antibodies to somatic and excretory-secretory antigens of metacestodes and modified the expression patterns of immunogenic molecules in both antigenic preparations. The combined therapy resulted in the elevation of IFN-γ and a decline of TNF-α and TGF-β1 in serum as compared to untreated group; however, SIL attenuated significantly the effect of PZQ on IL-4 and stimulated PZQ-suppressed phagocytosis of peritoneal macrophages. In the liver, SIL boosted the effect of PZQ on gene expression of the same cytokines in a similar way as was found in serum, except for down-regulation of PZQ-stimulated TNF-α. Compared to PZQ therapy, the infiltration of mast cells into liver after SIL co-administration was nearly abolished and correlated with suppressed activities of genes for collagen I, collagen III and α-SMA. In conclusion, co-administration of SIL modified the effects of PZQ therapy on antigenic stimulation of the immune system and modulated Th1/Th2/Tregs cytokines. In liver this was accompanied by reduced fibrosis, which correlated with significantly higher reduction of total numbers of tetrathyridia after combined therapy as compared with PZQ treatment.

Immunofluorescent Localization of Proteins in Schistosoma mansoni

Immunofluorescence allows the detection, visualization, and localization of proteins by using the ability of antibodies to firmly bind to specific antigens. Proteins must be accessible to thorough interaction with the specific antibodies. Different immune evasion mechanisms of parasites are directed to hamper or prevent access of antibodies to critical proteins or virulence factors. The blood fluke Schistosoma mansoni would not survive a day in the host blood capillaries if antibodies were able to readily bind to proteins located at the surface and mediate its attrition and demise by the complement system and/or the FcγR- or FcαR-bearing leukocytes. The worm surface is the area of parasite-host interaction and the route to critical nutrients, but is selectively permeable, allowing access of nutrient molecules but not host antibodies. Gentle procedures, which, however, are not commonly in use in vivo, are required to increase the permeability of the parasite outer membrane shield to just allow access of specific antibodies and identify and localize the proteins at the apical surface. Robust methods involving acetone, methanol, and Triton X-100 treatment lead to disintegration of the dual lipid bilayer cover with exposure of the proteins located in the tegument beneath. Internal proteins may not be accessed except following cryostat or paraffin sectioning. Accordingly, vaccine-induced specific antibodies to the apical surface or tegument proteins are unable to harm intact parasites. Specific antibodies to surface membrane proteins may only add to the action of administered or endo schistosomicides via acceleration of killing and interference with repair of severely and lightly impacted parasites, respectively. Therefore, careful immunofluorescent localization of S. mansoni proteins is important for devising the different control strategies against infection.

Immunization with adult Schistosoma mansoni tegument, treated with sub-curative praziquantel, partially protects mice against the infection

The tegument of schistosomes is a source of many potential anti-Schistosoma vaccine molecules. This work aimed to assess the protective effects of the adult Schistosoma mansoni tegument treated (TT) with sub-curative praziquantel (PZQ), whether in vivo (in vivo TT) or in vitro (in vitro TT), in murine schistosomiasis. In vitro TT and in vivo TT showed great similarity, and they differed from untreated tegument antigen (Teg) in terms of quantity and quality of protein bands on SDS-PAGE. Two immunization trials were performed, each with 50 mice, divided randomly into five groups of 10 mice each: (1) uninfected control mice (UC), (2) infected mice given phosphate buffer saline + adjuvant (PBS + adjuvant), (3) infected, Teg vaccinated, (4) infected, in vivo TT vaccinated, and (5) infected, in vitro TT vaccinated. All the immunizations with antigens induced mixed Th1/Th2 immune responses, as indicated by significantly high (P < 0.001) specific IgG2a and IgG1 levels, with Th1 predominating, as shown by a diminished IgG1/IgG2a ratio, as well as a high serum concentration of IFN-γ, an absence of IL-4 and increased IL-10. In vitro TT gave the most pronounced response. With respect to reduction of total worm burden, relative to PBS + adjuvant mice, in vitro TT achieved the highest significant (P < 0.001) results, followed by in vivo TT and Teg (51.8-57.04%, 44.6-50.2% and 35.2-39.3%, respectively). In scanning electron microscopy studies, all the tested antigens caused tegumental changes in adult worms, with the worst occurring with in vitro TT, such as retracted ventral sucker, an effect on the gynaecophoric canal, and changes to tubercles. In conclusion, in vitro TT, which is cheap to prepare, could be a potential vaccine against S. mansoni.

Drug-induced exposure of Schistosoma mansoni antigens SmCD59a and SmKK7

Background

Schistosomiasis is a serious health problem especially in developing countries and affects more than 243 million people. Only few anthelmintic drugs are available up to now. A major obstacle for drug treatment is the different developmental stages and the varying host compartments during worm development. Anthelmintic drugs have been tested mainly on adult schistosomes or freshly transformed cercariae. Knowledge concerning the larval stages is lacking.

Methodology/Principal Findings

In this study, we used in vitro-grown schistosomula (aged between 2 to 14 days) to investigate drug effects of the three anthelmintics praziquantel, artemether, and oxamniquine. Further, we analyzed the antibody accessibility of two exemplary schistosome antigens SmCD59a and SmKK7, before and after drug treatment. Our results demonstrated that praziquantel applied at a concentration of 1 μM inhibited development of all life stages. Application of 10 μM praziquantel led to dramatic morphological changes of all schistosomula. Artemether at 1 and 10 μM had differential effects depending on whether it was applied to 2-day as compared to 7- and 14-day schistosomula. While 2-day schistosomula were not killed but inhibited from further development, severe morphological damage was seen in 7- and 14-day schistosomula. Oxamniquine (1 and 10 μM) led to severe morphological impairment in all life stages. Analyzing the accessibility of the antigens SmCD59a and SmKK7 before drug treatment showed no antibody binding on living intact schistosomula. However, when schistosomula were treated with anthelmintics, both antigens became exposed on the larvae. Oxamniquine turned out to be most effective in promoting antibody binding to all schistosomula stages.

Conclusion

This study has revealed marked differences in anthelmintic drug effects against larvae. Drug treatment increases surface antigen presentation and renders larvae accessible to antibody attack.

Schistosomiasis is one of the major parasitic diseases in developing countries and still causes 200,000 deaths per year. Mass drug administration programs with praziquantel, the drug of choice against schistosomiasis, are currently undertaken in Sub-Saharan Africa. Praziquantel, although efficient against adult worms, fails to cure early infection. The complex developmental stages of schistosomes and migration through varying host compartments with different local drug concentration are a challenge for drug treatment. After infecting their mammalian host, schistosomula traverse through skin and the vasculature of lung, liver and intestines. During their migration, they develop from larvae to paired adults in approximately 4 to 5 weeks. So far, drug effects have been analyzed on adult worms or freshly transformed schistosomula only. Information about the effects on the larval stages is lacking. We were able to transfer the larval development of the first three weeks into the culture dish. This tool can be used for the analysis of drug effects against schistosomula and for investigation of the accessibility, expression and localization of antigens. Rendering the parasite’s larvae vulnerable to the host’s immune system by increasing antigen presentation is an important aspect of drug activity. We demonstrate on in vitro-cultured Schistosoma mansoni larvae, that SmCD59a and SmKK7, as examples for hidden antigens, become accessible to antibodies following drug treatment.

Clinical and experimental assessment of the effects of a new topical treatment with praziquantel in the management of rosacea

BACKGROUND

Rosacea is a common, chronic, and inflammatory skin disease. The burden imposed by this condition requires that new topical treatments be sought to enlarge the arsenal of drugs available in order to better manage this disease.

OBJECTIVES

This study was conducted to carry out an in vitro/in vivo evaluation of the antimicrobial activity of 3% praziquantel (PZQ) ointment and to determine its efficacy and safety in the treatment of rosacea.

METHODS

Patients with rosacea (n = 65) participated in a 16-week, randomized, single-blind pilot study of the effects of twice-daily monotherapy with 3% PZQ ointment vs. placebo (vehicle ointment). Efficacy was assessed clinically using the Investigator's Global Assessment Scale (IGAS) and the Clinical Erythema Assessment Scale (CEAS). Patients' quality of life was also determined using the Dermatology Life Quality Index (DLQI). The antimicrobial potential of 3% PZQ ointment was assessed by agar diffusion assay.

RESULTS

Scores on the IGAS and CEAS showed PZQ ointment to have a statistically significant therapeutic advantage over the placebo treatment (P < 0.001). At week 16, the PZQ group demonstrated a statistically significant greater reduction in CEAS score than the placebo group (P < 0.001). Analysis of CEAS scores showed that 41.9% of patients in the PZQ group and 18.2% of those in the placebo group achieved a CEAS score equivalent to a rating of "none". Mean scores on the DLQI at baseline and at the end of the study were, respectively, 15.8 and 4.1 in the praziquantel group. The PZQ-treated group also experienced a statistically significant improvement in comparison with the placebo group at week 16 (P < 0.001). The inhibitory zone indicating the extent of antimicrobial activity of 3% PZQ ointment ranged from 6 mm to 17 mm. No serious treatment-related adverse events occurred in either treatment group.

CONCLUSIONS

Use of 3% PZQ ointment twice daily for 12 weeks resulted in significantly better effects than a placebo treatment in improving rosacea and the patient's quality of life.

Immunization with tegument nucleotidases associated with a subcurative praziquantel treatment reduces worm burden following Schistosoma mansoni challenge

Schistosomiasis is a debilitating disease caused by flatworm parasites of the Schistosoma genus and remains a high public health impact disease around the world, although effective treatment with Praziquantel (PZQ) has been available since the 1970s. Control of this disease would be greatly improved by the development of a vaccine, which could be combined with chemotherapy. The sequencing of the Schistosoma mansoni transcriptome and genome identified a range of potential vaccine antigens. Among these, three nucleotidases from the tegument of the parasite, presumably involved in purinergic signaling and nucleotide metabolism, were proposed as promising vaccine candidates: an alkaline phosphatase (SmAP), a phosphodiesterase (SmNPP-5) and a diphosphohydrolase (SmNTPDase). Herein, we evaluate the potential of these enzymes as vaccine antigens, with or without subcurative PZQ treatment. Immunization of mice with the recombinant proteins alone or in combination demonstrated that SmAP is the most immunogenic of the three. It induced the highest antibody levels, particularly IgG1, associated with an inflammatory cellular immune response characterized by high TNF-α and a Th17 response, with high IL-17 expression levels. Despite the specific immune response induced, immunization with the isolated or combined proteins did not reduce the worm burden of challenged mice. Nonetheless, immunization with SmAP alone or with the three proteins combined, together with subcurative PZQ chemotherapy was able to reduce the worm burden by around 40%. The immunogenicity and relative exposure of SmAP to the host immune system are discussed, as key factors involved in the apparently synergistic effect of SmAP immunization and subcurative PZQ treatment.

Pharmacodynamics of mefloquine and praziquantel combination therapy in mice harbouring juvenile and adult Schistosoma mansoni

Praziquantel (PZQ) is currently the only drug widely used for the treatment of schistosomiasis, but the antimalarial drug mefloquine (Mef) possesses interesting antischistosomal properties. Combination therapy with these two drugs has been suggested as a strategy for transmission control, as PZQ is active against adult worms and Mef is active against schistosomula. To examine the efficacy of combination therapy, Schistosoma mansoni-reinfected mice were separated into seven groups: untreated (I), treated with PZQ in doses of 200 mg/kg (II) or 1,000 mg/kg (III), treated with Mef in doses of 200 mg/kg (IV) or 400 mg/kg (V); each dose was divided equally and given on two consecutive days. Group VI was treated with doses of PZQ + Mef as in groups II and IV, respectively, while group VII was treated with PZQ + Mef as in groups III and V, respectively. PZQ + Mef at the reduced doses of 200 mg/kg each enhanced the therapeutic efficacy over the reduced PZQ dose alone as shown by a very high reduction in the total numbers of mature worms (95% vs. 49%), immature worms (96% vs. 29%) and the complete eradication of immature females, mature females and immature eggs. The reduction in worm burden was associated with the healing of hepatic granulomatous lesions and the normalisation of all liver enzymes. Therefore, the use of Mef with PZQ is more effective than PZQ alone and should be considered for clinical trials in humans as a potential treatment regimen to prevent treatment failures in areas with high rates of schistosomiasis.

Biochemical characterization and differential expression of a 16.5-kilodalton tegument-associated antigen from the liver fluke Fasciola hepatica

A cDNA encoding a 16.5-kDa protein termed FhTP16.5 was identified by immunoscreening of a cDNA library from Fasciola hepatica adult flukes using pooled sera from rabbits infected with F. hepatica for 4 weeks. Quantitative reverse transcriptase PCR (qPCR) analysis revealed that FhTP16.5 is not expressed in unembryonated eggs. It is poorly expressed in miracidia and highly expressed at the juvenile and adult stages; however, significant differences were found between the expression levels of FhTP16.5 in juveniles versus adult flukes. Recombinant FhTP16.5 was expressed at high levels in Escherichia coli, purified by affinity chromatography, and used to raise anti-FhTP16.5 polyclonal antibodies in rabbits. Immunoblot analysis using the anti-FhTP16.5 IgG antibody identified FhTP16.5 in crude and tegumental extracts and in excretory-secretory products of F. hepatica. The protein was not detected in crude extracts of Schistosoma mansoni or Schistosoma japonicum. Antibodies to FhTP16.5 were detected in the sera of rabbits at 3 to 12 weeks of F. hepatica infection as well as in the sera of humans with chronic fascioliasis; these findings suggest that FhTP16.5 could be a good antigen for serodiagnosis of fascioliasis. Immunohistochemistry demonstrated that FhTP16.5 localizes to the surface of the tegument of various developmental stages and in parenchymal tissues of the adult fluke. Such specific localization makes FhTP16.5 an attractive target for immunoprophylaxis or chemotherapy.

The use of pentoxifylline as adjuvant therapy with praziquantel downregulates profibrogenic cytokines, collagen deposition and oxidative stress in experimental schistosomiasis mansoni

This study investigates the possible use of pentoxifylline (PTX), with antifibrotic and anti-inflammatory properties, as adjuvant in treatment of schistosomal liver fibrosis through determination of some profibrogenic cytokines, oxidative stress and collagen deposition. Animals were classified into seven groups: normal control (i), Schistosoma mansoni-infected untreated (ii), infected treated with praziquantel (PZQ) curative, 1000mg/kg (iii) or sub curative, 200mg/kg dose (iv), infected treated with PTX alone (10mg/kg/day; 5days/wk) for 8weeks starting from the 2nd to the 10th week post infection (v), or in addition to curative (vi) or sub curative dose of PZQ (vii). Serum transforming growth factor-β1 (TGF-β1), tumor necrosis factor-α (TNF-α), matrix metalloproteinases-2 (MMP-2) and hepatic hydroxyproline (Hyp) content, glutathione related antioxidant enzymes and malondialdehyde (MDA) were determined. Results showed that S. mansoni infection produced remarkable elevations in the serum levels of TGF-β1, TNF-α, MMP-2 and the hepatic contents of Hyp, glutathione reductase (GR), MDA with significant reduction in reduced glutathione (GSH), glutathione peroxidase (GPx), glutathione-S-transferase (GST) and superoxide dismutase (SOD) when compared with their corresponding normal controls. Treatment of infected mice with PTX in addition to PZQ curative rather than its sub curative dose produced the best results evidenced by complete normalization in the previously mentioned serum and hepatic parameters.

CONCLUSION

PTX could attenuate liver fibrosis in early stages of S. mansoni infection through downregulation of profibrogenic cytokines, oxidative stress and collagen deposition.

Development and characterization of polyspecific anti-mitochondrion antibodies for proteomics studies on in toto tissue homogenates

We describe the characterization of polyclonal antibodies directed against the whole mitochondrial subproteome, as obtained by hyperimmunization of rabbits with an organelle fraction purified from human skeletal muscle and lysed by sonication. After 2-DE separations with either blue native electrophoresis or IPG as first dimension and blotting, the polyspecific antibodies detect 113 proteins in human muscle mitochondria, representative of all major biochemical pathways and oxidative phosphorylation (OXPHOS) complexes, and cross-react with 28 proteins in rat heart mitochondria. Using as sample cryosections of human muscle biopsies lysed in urea/thiourea/CHAPS, the mitochondrial subproteome can be detected against the background of contractile proteins. When comparing with controls samples from mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes patients, immunoblotting shows in the latter a drastic reduction for the subunits of OXPHOS complex I as well as an increase of several enzymes, including ATP synthase. This finding is the first evidence at the proteomic level of massive up-regulation in a number of metabolic pathways by which the affected tissues try to compensate for the deficit in the OXPHOS machinery.

Can schistosomiasis really be consigned to history without a vaccine?

Recently, considerable enthusiasm has been expressed for expanding and combining control efforts for neglected tropical diseases (NTDs). While these efforts are laudable, the drugs in question require repeated mass administration for indefinite periods of time, and their use to achieve eradication is fraught with challenges. Mass drug administration is unlikely to be effective in isolation, and should not proceed without concurrent control methods, such as vaccines. Schistosomiasis is one of the most important NTDs, and one whose effective control is unlikely in the absence of improved sanitation and a vaccine. Recent advances in biotechnologies have enhanced antigen discovery and new molecules that show promise as recombinant vaccines are being reported. Funding bodies supporting research into the control of schistosomiasis should invest not only in mass drug administration but also in the development of new control strategies, including the development of vaccines.

Pharmacodynamics of pentoxifylline and/or praziquantel in murine schistosomiasis mansoni

Pentoxifylline (PTX) was proved to exert both anti-inflammatory and anti-fibrotic effects, and was used therapeutically in this experimental model to investigate its role alone or with praziquantel (PZQ) in Schistosoma mansoni-infected mice, and to explore its impact on the tissue expression of transforming growth factor-beta1 (TGF-beta1). S. mansoni-infected mice were divided into seven groups: Control untreated (I), treated with curative dose of PZQ, 500 mg/kg/day for 2 consecutive days (II), or subcurative dose, 100 mg/kg/day for 2 consecutive days (III), treated with PTX (10 mg/kg/day for 5 days/wk) alone for 4 weeks (IV) or in addition to subcurative dose of PZQ (V), and treated with PTX alone for 8 weeks (VI) or in addition to subcurative dose of PZQ (VII). All animals were killed 10 weeks post infection. Parasitological assessment of worm burden, tissue egg load and oogram pattern was carried out. The degree of granulomatous fibrosis and eosinophilic cell population was quantified in Sirius-red-stained sections and tissue transforming growth factor beta-1 expression was estimated immunohistochemically. Serum ALAT and GGT, as well as hepatic content of reduced GSH, were measured. The results revealed the highest percent of worm reduction and dead ova in groups (II) and (VII) accompanied by significant diminution in granulomatous parameters, collagen content and TGF-beta1 tissue expression. Moreover, treatments with PTX and/or PZQ ameliorated the liver functions. In conclusion, prolonged treatment with PTX has a potent anti-fibrogenic role especially when used in the early stages of infection, with limited toxic effects on schistosome worms and eggs. Thus, PTX can be used as an adjuvant therapeutic tool with anti-helminthic drugs in the treatment of human schistosomiasis.

Distribution of 28.5 kDa antigen in the tegument of adult Fasciola gigantica

Monoclonal antibody (MoAb) specific to 28.5 kDa tegumental antigen (TA) was used to localize this antigen in various tissues of adult Fasciola gigantica by means of indirect immunofluorescence, immunoperoxidase and immunogold techniques. The indirect immunofluorescence and immunoperoxidase detections revealed that this antigen was concentrated in the tegument particularly in its outer rim, tegumental cells and their processes, epithelial linings of the oral sucker and the proximal part of digestive tract. It was also detected at a moderate concentration in spermatogenic cells in the testes, cells of Mehlis' gland, oocytes within the ovary, and ovum within the egg of adult parasites. At TEM level, the immunogold detection showed deposit of gold particles specifically in G(2) tegumental granules and on the surface membrane. Thus, this antigen is expressed in the tegument and associated structures of adult parasites, and it could be a major component of the G(2) granules which are shown to fuse with the surface membrane and contribute material to replace the casted-off membrane. This process is a part of membrane turnover that prevents the parasite from being attacked by the host immune effector cells.

Altered immunoglobulin isotype profile and anti-immature worm surface immunoglobulins in mice harboring a praziquantel-resistant Schistosoma mansoni isolate

After placement in mice of PZQ-sensitive and -insensitive S. mansoni isolates obtained from villagers responding and not responding to PZQ, parasitological criteria reflecting their biological development and also the host anti-immature worm immunoglobulin isotypes were examined 8 and 10 weeks post infection. Hepatic granuloma diameter, hepatic histopathological changes and immunolocalization of IgG and IgM on the surface of PZQ-sensitive and -resistant worms were also examined 10 weeks post infection. Data showed that parasitological criteria were not significantly different between mice infected with the PZQ-sensitive and -insensitive S. mansoni isolates. As regards serum immunoglobulins, in mice infected with the PZQ-insensitive S. mansoni isolate, IgG and IgG1 were significantly (p<0.05) lower 8 and 10 weeks post infection, respectively (1.41+/-0.07 and 1.08+/-0.10 and 1.35+/-0.06 and 1.09+/-0.07) than in mice infected with the PZQ-sensitive S. mansoni isolate (1.73+/-0.15 and 1.38+/-0.10 and 1.73+/-0.17 and 1.54+0.21) after the same observation periods. IgM level was nearly the same while IgE was lower than that recorded in mice infected with the PZQ-sensitive S. mansoni isolate. IgG immunofluorescence was also lower (60%+/-6.78) on the surface of resistant worms than that of sensitive worms (66.6%+/-5.27); meanwhile, hepatic granuloma diameter was significantly larger (296.5+/-3.0 vs 283.6+/-4.0) in mice infected with the PZQ-insensitive S. mansoni isolate with higher percentage of intact eggs. Differences in the immunogenic make up of PZQ-sensitive and -insensitive S. mansoni isolates qualitatively and/or quantitatively favoring a certain Th cell subpopulation response could be the underlying reason for such differences recorded in the host immunoglobulin isotype response and also the egg-induced hepatic histopathological changes.

Pre-exposure of cattle to drug-abbreviated Fasciola hepatica infections: the effect upon subsequent challenge infection and the early immune response

In this study we examined whether juvenile liver flukes are capable of stimulating protective immune responses in cattle. Four experimental groups of cattle were studied as follows: group A, a positive control, received a primary infection on day 0 and a secondary infection 28 days later; group B also received two infections but the primary infection was terminated by drug treatment on day 5; group C, received infections on days 0, 5 and 10 which were terminated by drug treatments on days 1, 6 and 11 and then a secondary infection on day 28; group D received an infection only on day 28. Juvenile flukes appear to induce protective responses because: (a) group B animals had significantly lower levels of gamma-GT (P<0.05) than group D; (b) both groups B and C exhibited lower parenchymal phase GLDH levels (P=0.006 and 0.041, respectively); and (c) both groups B and C had lower secondary phase eosinophilia (P=0.002 and 0.02, respectively) than those in group D. Sera taken from groups A-C contained antibodies reacting to a variety of proteins in adult fluke somatic antigen and excretory-secretory preparations, particularly to proteins of 52-60, 68-72 and 82-96 kDa. After secondary challenge the antibody responses of group A to these proteins declined while reactivity to proteins of 28-30 kDa increased. Antibody responses to the 28-30 kDa proteins were not detected in groups B-D until 3 weeks later than those observed in group A. Antibody responses to Fasciola hepatica cathepsin L proteases, which are known to induce protection, were monophasic, of the IgG1 isotype only and were not observed prior to secondary challenge in any of the four groups. In contrast, the response to another protective antigen fraction, a high molecular sized haem protein, was of a mixed IgG1/IgG2 nature and was detected within 14 days of primary infection. However, no significant difference in antibody titres to either protein preparation was observed after the secondary infection when groups B and C were compared to group D.

Heterogeneities in anti-schistosome humoral responses following chemotherapy

Schistosomiasis is a major public health problem in Africa, the Middle East, Asia and South America. The main control strategy is to treat infected people with anthelmintic drugs, principally the safe and relatively cheap drug praziquantel. Several treatment re-infection studies in humans have shown that praziquantel can have long-term effects beyond a transient reduction of infection intensity. These long-term effects include the altering of schistosome-specific immune responses in humans, which is associated with resistance to re-infection. Differences have been observed in treatment-induced immunological changes between individuals and between populations. This article discusses the contributions of host- and parasite-related heterogeneities to post-treatment humoral responses in humans infected with Schistosoma mansoni and Schistosoma haematobium and considers the practical implications of such heterogeneity for schistosome immuno-epidemiology studies.

Antibody responses to the fucosylated LacdiNAc glycan antigen in Schistosoma mansoni-infected mice and expression of the glycan among schistosomes

Infections of animals with parasitic worms, such as Schistosoma mansoni, induce humoral immune responses to carbohydrate antigens, raising the possibility that such antigens might be useful targets for the development of vaccines and new diagnostic approaches. Here we describe the identification of fucosylated LacdiNAc (LDNF) [GalNAc beta 1-4(Fuc alpha 1-3)GlcNAc-R] as a new carbohydrate antigen in S. mansoni that induces humoral immune responses in infected mice. The presence of antibodies was determined by ELISA using a neoglycoconjugate synthesized to express LDNF sequences. Sera from S. mansoni-infected, but not uninfected, mice contain IgM, IgG, IgA, and IgE antibodies to LDNF. The IgG antibodies are primarily of the IgG1 and IgG3 subclasses, with no detectable levels of the complement-fixing IgG2a and IgG2b isotypes. An IgM monoclonal antibody, designated SMLDNF1, was generated from the spleens of S. mansoni-infected mice, and the antibody exhibits specific recognition of LDNF sequences, but not other fucosylated glycans tested. Immunocytochemical analysis demonstrates that LDNF antigens are localized on the tegumental surface of adult S. mansoni. Western blot analysis indicates that LDNF sequences are expressed on numerous high-molecular-weight glycoproteins from the three major human schistosome species, as well as the bird schistosome Trichobilharzia ocellata. The identification of LDNF antigen on the tegumental glycoproteins of schistosomes and the ability to synthesize LDNF conjugates should aid in the development of glycan-based vaccines and immunodiagnostic tests for schistosomiasis and in determining the role(s) of the glycans in worm development and pathogenesis.

Changes in specific anti-egg antibody levels following treatment with praziquantel for Schistosoma haematobium infection in children

Fifty-seven children 6-15 years old resident in a Schistosoma haematobium endemic area in eastern Zimbabwe were treated with praziquantel at 40 mg/kg body weight. Levels of IgA, IgE, IgG1, IgG2, IgG3, IgG4, and IgM antibodies against soluble egg antigen (SEA) were assayed by ELISA before treatment and at 18 and 36 weeks following treatment. Prevalence of infection (as determined by urine egg counts) was 65% before treatment, all children were confirmed egg negative six weeks after treatment, and reinfection prevalence was 4% at 18 weeks and 21% at 36 weeks after treatment. At 18 weeks after treatment, there was a massive increase in IgG1 levels and significant increases in IgE and IgG4 levels and significant decreases in IgA and IgG2 levels. Similar patterns occurred at 36 weeks after treatment. Egg positive children showed a more marked increase in IgG1 and (for older children) a more marked decrease in IgG2 levels. There were no other effects of age or sex. IgA and IgG1 levels fell significantly between 18 and 36 weeks following treatment but not to pretreatment levels. The results show that specific anti-egg antibody responses are highly sensitive to the effects of praziquantel treatment. A possible consequence is that the susceptibility of children to infection with S. haematobium is altered by chemotherapy; this requires further investigation.

Genotoxic activity of praziquantel

Praziquantel is a synthetic drug with a remarkable activity against parasites, particularly treamatodes and cestodes. Initial genotoxicity tests used a spectrum of endpoints including tests in bacteria, yeasts, mammalian cells and Drosophila and each one gave negative results. Effects on reproductive cells of mice were negative as well. However, host mediated studies in mice and humans were contradictory and a comutagenic effect with several mutagens and carcinogens was found. Later studies, including monitoring in humans and pigs have shown that Praziquantel induces a greater frequency of hyperploid lymphocytes as well as structural chromosomal aberrations, but not in all the individuals treated. In vitro studies have demonstrated that Praziquantel can induce micronuclei in syrian hamster embryonic (SHE) cells and in lymphocytes of some individuals. The same was found about structural chromosomal aberrations. Fetal death and fetal resorption were found when Praziquantel was administered in high doses to pregnant rats between the 6th and 10th day of gestation. Due to its efficiency as a parasiticide, Praziquantel is in use in Latin-American, Asiatic, African and East-European countries where infections by trematodes and cestodes are frequent. However, the extensive use of Praziquantel in multiple reinfections, in non-infected and non-diagnosed individuals for prevention, in higher doses or repeated doses for cysticercosis treatment and in individuals exposed to environmental mutagens, in conjunction with new findings about its metabolism and genotoxic properties, make it necessary to further evaluate the potential of this drug not only to be mutagenic per se, but to contribute in the development of neoplasm.

Immunisation of sheep by drug-abbreviated infections of Ostertagia circumcincta and Trichostrongylus colubriformis against field challenge of gastro-intestinal nematodes

A very high level of protection was achieved against homologous (up to 97%) and heterologous (up to 87%) infections in 12-month-old Romney sheep immunised with oxfendazole-abbreviated infections of Ostertagia circumcincta and Trichostrongylus colubriformis. No significant protection occurred following ivermectin-abbreviated infections. None of the immunised sheep showed an increase in antibody level against excretory-secretory antigen of T. colubriformis infective larvae. The immunisation procedures did not cause a decrease in wool production, or liveweight gains compared with non-immunised controls.

Schistosome resistance to praziquantel: Fact or artifact?

Praziquantel is the current drug of choice for human schistosomiasis. Recent reports from laboratory and field studies concerning reduced praziquantel efficacy against Schistosoma mansoni have generated some controversy. The prevailing question is whether the emergence of strains of schistosome resistant to praziquantel is a fact, or an artifact resulting from erroneous field or laboratory experimentation. In this article, Padraic Fallon, Liang-feng Tao, Magdi Ismail and James Bennett examine the available evidence for schistosome resistance to praziquantel. Contributory factors to the schistosomicidal activity of praziquantel, which may interfere with evaluation of drug efficacy or resistance, are also considered.

Temporal differences in praziquantel- and oxamniquine-induced tegumental damage to adult Schistosoma mansoni: implications for drug-antibody synergy

A temporal study of the effects on the tegument of Schistosoma mansoni adult worm following in vivo praziquantel and oxamniquine treatment was performed. Drug-induced damage to the tegument, exposure of surface antigens and attachment of host antibody occurred rapidly, within 1 h, following praziquantel treatment. Oxamniquine-treated worms required 4-8 days for these effects to be apparent. The 2 drugs differed in the degree and sites of damage on the worm surface. The administration of 2 different polyspecific rabbit sera with drug significantly increased the efficacy of praziquantel when administered with the drug, but not when given 6-9 days after drug treatment. In contrast, only 1 serum was synergistic with oxamniquine when administered with drug and both sera were synergistic when given 6-9 days after drug treatment. The effect of immune killing of drug-treated worms is discussed.