Influence of physicochemical parameters on the spatial distribution of snail species that are intermediate hosts of human schistosomes in the Senegal River Delta.

The objective of this work was to identify possible correlations between physicochemical parameters (water temperature, water flow velocity, electrical conductivity, dissolved oxygen, salinity, pH, nitrates, and phosphates) and the spatial distribution in the Senegal River delta of snail species that are intermediate hosts of human schistosomes. Eight water points (ME1 to ME4, NE1 and NE2, TA1 and TA2) were selected in the villages of Menguègne Boye, Ndellé Boye, and Thilla for biweekly monitoring of these snails and the physicochemical parameters of the water. The results show that the spatial distribution of the snail populations is related to pH, dissolved oxygen (mg/l), conductivity, temperature (̊C), and water flow velocity (m/s).

Role of environmental parameters on the density of intermediate host snails of human schistosoma during the year in the commune of Richard-Toll, Senegal.

The implementation and expansion of development projects (dams and irrigation schemes) in the Senegal River valley have led to a significant proliferation of snails. We conducted a one-year (2014) study project, monitoring their density in the commune of Richard Toll, to assess the role of environmental parameters on mollusc population dynamics. Four species involved in the transmission of human schistosomiasis were found: Bulinus globosus, B. truncatus, B. senegalensis, and Biomphalaria pfeifferi. Among the intermediate hosts, B. truncatus is the most abundant species, followed by B. globosus. Snail density depends on the nature of the water point but also on environmental parameters such as vegetation. This study showed that vegetation, water level (flood), and flow velocity influence the dynamics of the snail populations that are intermediate hosts of human schistosomes.

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.

[Spatiotemporal distribution of tuberculosis cases in the city of Saint-Louis Senegal from 2008-2011]. / Répartition spatio-temporelle des cas de tuberculose dans la ville de Saint-Louis du Sénégal entre 2008-2011.

BACKGROUND: We studied the incidence of tuberculosis in the health district of Saint-Louis, Senegal over a period of 4years (2008-2011). One thousand three hundred and eighty-six cases were identified, producing an annual standardized incidence ratio of 129 cases per 100,000 inhabitants. RESULTS: Men in the 15-24-year old age group were more likely to be affected, and diagnosis was more common in the second half of the year. Treatment compliance was excellent (96%), and the cure rate of patients with a TB-positive microscopic examination was 95%. The overall treatment failure rate was 1% and the 6-month morality was 2%. Seropositivity, measured in volunteer patients (48%) was 3%. CONCLUSION: A spatial and temporal map of tuberculosis in the city of Saint-Louis, Senegal has been established. A cluster appears to be very likely in Guet Ndar, a particularly dense population zone in a fishing area. There is also a possible secondary cluster at Pikine.

Criteres echographiques predictifs d'hypertension portale due a Schistosoma mansoni dans une zone d'endemie recente

Les premiers cas de bilharziose a Schistosoma mansoni ont ete depistes dans la vallee du fleuve Senegal il y a dix ans. Aujourd'hui; le niveau d'endemie est tel que certains villages presentent des prevalences superieures a 90 p. 100. Le diagnostic de schistosomose n'est parfois porte qu'au stade d'hypertension portale (rupture de varices oesophagiennes). L'endoscopie est l'examen de reference pour detecter la presence de varices oesophagiennes; mais son application sur le terrain est delicate. C'est pourquoi leur recherche par echographie; acte non invasif; est d'un grand interet. Cette etude a recherche chez 101 sujets de la region de Richard-Toll l'existence de signes d'hypertension portale; simultanement par fibroscopie digestive et par echographie. Elle a montre que moins de 10 ans apres la description du premier cas de bilharziose; il existait deja des formes compliquees d'hypertension portale dans la region. Cette etude a egalement cherche a etablir un score echographique permettant de predire l'existence d'une hypertension portale. Les items retenus ont ete l'epaississement de la paroi des vaisseaux portes; le diametre de la veine porte et de la veine splenique et l'aspect collabe ou non de la veine splenique pendant l'inspiration. Au cours de l'etude; l'echelle de score ainsi etablie a semble etre un bon temoin predictif du developpement de varices oesophagiennes. L'echographie represente un examen utile pour le depistage des formes compliquees de schistosomoses susceptibles de representer un moyen simple de surveillance des populations residant en zone d'endemie recente et intense de schistosomose

Methylated CpG-containing plasmid activates the immune system.

Bacterial DNA differs from mammalian DNA by the presence of unmethylated cytosine-phosphate-guanosine (CpG) motifs. The immunostimulatory properties of a DNA vaccine have been suspected to be associated with these motifs. The aim of this study was to assess the inactivation of the immunostimulatory potential of a plasmid after methylation of its CpG motifs. We constructed two identical non-coding plasmids, and one of these was de novo methylated on its CG sequences. A single administration of recombinant antigen with methylated or unmethylated CpG-containing plasmid was performed in mice. As expected, only unmethylated CpG-containing plasmid enhanced the specific immune response. However, a study of in vivo activation of Langerhans' cells and analysis of mRNA synthesis indicated that both the plasmids promoted cell emigration and cytokine induction. These data highlight that a methylated CpG-containing plasmid is not inert and carries immunomodulatory properties. The results further emphasize the necessity to definitively identify the mode of action of plasmids used for DNA vaccination.

Schistosomiasis co-infection in humans influences inflammatory markers in uncomplicated Plasmodium falciparum malaria.

Malaria and schistosomiasis are the two major parasite diseases present in developing countries. The epidemiological co-infection with schistosomiasis could influence the development of the physiological reaction associated with Plasmodium falciparum infection in human. Most studies have demonstrated the association of circulating levels of interferon-gamma (IFN-gamma), tumour necrosis factor-a (TNF-alpha), interleukin-10 (IL-10), transforming growth factor (TGF-beta) and soluble Tumour Necrosis Factor Receptors (sTNF-RI and sTNF-RII) with the morbidity of malaria. In the present study, we showed that Schistosoma haematobium co-infection influences, in an age-dependent manner, the unbalance between pro- and anti-inflammatory circulating cytokines that play a key role during malaria infection. Indeed, children co-infected by S. haematobium have higher levels of IFN-gamma and sTNF-RII than children infected only by P. falciparum. In contrast, co-infected adults presented a significant increase of IFN-gamma, IL-10, TGF-beta, sTNF-RI and sTNF-RII rates and IL-10/TNF-alpha ratio. Taken together, this study indicates that schistosomiasis co-infection can unbalance the regulation of inflammatory factors in uncomplicated P. falciparum malaria. The possible consequences of the schistosomiasis co-infection for age-dependent malaria morbidity are discussed.

Adjuvant activity of free Bordetella pertussis filamentous haemagglutinin delivered by mucosal routes.

The development of safe and potent mucosal adjuvants remains a major objective in vaccinology. The potential usefulness of filamentous haemagglutinin (FHA) of Bordetella pertussis as an adjuvant was assessed in a mouse model. The glutathione-S-transferase of Schistosoma mansoni (Sm28GST) was used for intranasal administration, while the gut-resistant keyhole limpet haemocyanin (KLH) was administrated by the oral route. For both antigens, coadministration with FHA increased antigen-specific immunoglobulin titres. This adjuvant effect did not require chemical cross-linking or direct interaction between FHA and the antigen tested. FHA also behaved as an adjuvant by the subcutaneous route, indicating that its adjuvanticity is not restricted to binding to mucosal surfaces. The FHA-induced adjuvanticity was also observed in mice with high anti-FHA antibody titres as a result of antipertussis vaccination, indicating that pre-existing anti-FHA antibodies do not impair FHA adjuvanticity. No mRNA coding for proinflammatory cytokines was induced in the lungs after intranasal FHA administration. However, an increase in the levels of mRNAs coding for B7-1, transforming growth factor (TGF)-beta and major histocompatibility complex (MHC)-II was detected in the lungs after FHA administration. Although the molecular mechanisms of the FHA-induced adjuvanticity remain to be elucidated, the data presented here indicate that this adhesin, already assessed for human use as a pertussis vaccine constituent, represents a promising adjuvant to improve the humoral immune response when given by mucosal routes.

Failure of a recombinant Schistosoma bovis-derived glutathione S-transferase to protect cattle against experimental Fasciola hepatica infection.

The potential of a recombinant Schistosoma bovis 28-kDa glutathione S-transferase (rSb28GST) to protect cattle against Fasciola hepatica was tested in a vaccination trial. Thirty two calves were randomly divided into four groups of eight animals. Calves of the three vaccine groups received two intramuscular injections at 3 weeks interval, of 0.250mg rSb28GST in either aluminium hydroxide (Al(OH)(3)), Quil A, or PBS emulsified in an equal volume of Freund's complete adjuvant (FCA).Animals of the control group received injections of Al(OH)(3)/PBS only. All animals were challenged orally with a total of 360 metacercariae of F. hepatica, spread over 6 weeks. All groups of vaccinated animals produced measurable IgG antibody titers to rSb28GST after vaccination. Animals immunised with FCA adjuvanted vaccine had the highest and more durable antibody titers and only sera from this group recognised an approximately 24kDa protein band from F. hepatica, that is thought to be a F. hepatica GST. Despite a good antibody response differences in cumulative faecal egg output between the groups were not statistically significant. In addition, no significant difference was found between groups in terms of total worm numbers or percentage of immature flukes recovered at necropsy. In conclusion, the recombinant S. bovis 28kDa GST was not found to adequately protect cattle against experimental F. hepatica challenge, using either aluminium hydroxide, Quil A or FCA as adjuvant.

Malaria co-infection in children influences antibody response to schistosome antigens and inflammatory markers associated with morbidity.

The epidemiological coexistence of schistosomiasis and malaria is frequently observed in developing countries. Co-infection with malaria in children could influence the development of acquired immunity associated with the resistance or the pathology of schistosomiasis. In the present study, performed during May to June 1996 in Senegal, the humoral immune response to Schistosoma haematobium 28 kDa glutathione S-transferase (Sh28GST) vaccinal antigen and to soluble egg antigens (SEA) has been evaluated in individuals infected by S. haematobium. Specific immunoglobulin G3 (IgG3) and IgE responses were significantly higher in co-infected children with Plasmodium falciparum compared with children infected with S. haematobium only. In addition, circulating levels of interferon-gamma (IFN-gamma), interleukin-10 (IL-10), and soluble tumor necrosis factor receptor II (sTNF-RII), 3 parameters associated with schistosomiasis morbidity, were significantly increased in co-infected children. Taken together, this study indicated that malaria co-infection can both influence the acquired specific immune response to schistosome antigens and unbalance the regulation of inflammatory factors closely involved in schistosomiasis pathology.

Transplacental transfer of schistosomal circulating anodic antigens in cows.

The present work investigated the transplacental passage of circulating anodic schistosome antigens (CAA) and the production of foetal antibodies in response to antigenic stimulation in Schistosoma mattheei infected cows. Three groups were available: six calves born to non-infected cows received colostrum from a pool from non-infected cows (group 1), six calves born to non-infected cows (group 2) and six calves born to infected cows (group 3) received colostrum from a pool from infected cows. Schistosoma-specific IgG1 antibody and CAA levels were measured in the colostrum pools, the sera collected from the cows, and the sera collected from the calves at birth, after intake of colostrum and at day 30. The specific IgG1 antibody levels were significantly higher in the sera from cows of group 3. In four cows of group 3 high CAA levels were detected. The specific IgG1 antibody levels were 0.646 and 0.176 OD for the infected and non-infected colostrum pool, respectively, and the CAA levels were 5667 and 2557 pg CAA/mL, respectively. At birth high levels of specific IgG1 antibody and CAA were detected in 4 calves of group 3; levels in the other two calves were negligible. After intake of colostrum, specific IgG1 antibody levels of group 1 increased slightly at day 1 to become again insignificant at day 30. In group 2 specific IgG1 antibody levels increased significantly between days 0 and 1, to decrease, although not significantly, at day 30. Finally, in group 3 the delta OD values increased at day 1 and remained high until day 30. After intake of colostrum the CAA level increased very slightly for groups 1 and 2 to become again undetectable at day 30. In group 3 a nonsignificant decrease in CAA levels was observed at day 1 followed by a further significant decrease to reach low levels at day 30. The suggested intrauterine antigenic stimulation may be important not only for generating immune responses to natural early infections, but also for enhancing the immunogenicity and efficacy of vaccines administered to newborns.

The influence of colostrum on early Schistosoma mattheei infections in calves.

The study investigated whether the susceptibility of calves to an early Schistosoma mattheei infection may be modified by intake of colostrum from infected cows. Twelve calves born to non-infected mothers were randomly divided into 2 groups of 6. The animals from group 1 were fed colostrum originating from a pool collected from non-infected cows, the calves from group 2 received colostrum from a pool collected from cows infected with S. mattheei. One month after birth all calves were infected by exposure to 1000 cercariae of a local strain of S. mattheei, and perfused 12 weeks later to determine the worm- and tissue egg counts. IgG(H+L), IgG1, IgG2 and IgA levels against soluble adult worm antigen preparation of S. bovis (SWAP bovis) were analysed in both colostrum pools and in the serum from the calves collected during the study before and after receiving colostrum, then on days 7, 30, 73 and 122. Faecal egg counts were determined from day 73 onwards. The IgG(H+L), IgG1 and IgA levels of the positive colostrum pool were higher than those of the negative pool. Calves of group 2 showed significantly higher levels of IgG(H+L) and IgG1 until day 73, to reach equal levels at necropsy. Calves of group 2 showed significant reductions of 42, 28 and 42% in total worm counts, female worm counts, and tissue egg counts, respectively, and a reduction of 25% in cumulative faecal egg counts. These findings indicate that there was a significant impact of colostrum on the parasitological and serological course of early S. mattheei infections.

Features of the antibody response attributable to plasmid backbone adjuvanticity after DNA immunization.

DNA vaccination induces antigen-specific immune responses with characteristics distinct from other vaccination modes. In the present study, the contribution of the plasmid backbone adjuvant effect to the quality of the DNA-raised antibody response was investigated. For this purpose, three intradermal primings were compared in mice using: (1) the recombinant Schistosoma haematobium glutathione S-transferase antigen (rSh28GST): (2) rSh28GST supplemented with a non-coding plasmid; and (3) a Sh28GST-encoding plasmid. In contrast to immunization with the protein, DNA immunization elicited a very stable antibody (Ab) response over a prolonged period of time. This feature was attributed to the plasmid backbone, because co-administration of the non-coding plasmid with rSh28GST allowed the maintenance of the specific Ab response. A strong anamnestic Ab response was induced after intradermal boost with rSh28GST only in the mice primed with pMSh. This indicated that the selective ability of DNA vaccination to induce memory humoral response was independent of the plasmid backbone. In contrast the plasmid backbone was found to strongly participate in the preferential IgG2a Ab production observed. These results suggest that, following DNA immunization, the Th1-biased profile and the maintenance of the long-lived Ab response could be attributed to an adjuvant effect of the plasmid backbone during priming, whereas the strength of B-cell memory was independent of this effect.

Medullary gnathostomiasis in a white patient: use of immunodiagnosis and magnetic resonance imaging.

A 48-year-old French diplomat presented with a sensory-motor paraparesis of rapid onset, leading to paraplegia. Successive magnetic resonance image scans showed lesions of the thoracic spinal cord that were at different levels from one examination to the next. Specific anti-gnathostome antibodies were detected by means of enzyme-linked immunosorbent assay and Western blot test in both plasma and cerebrospinal fluid. Albendazole treatment prevented disease progression, but only partial regression of the neurologic symptoms was obtained.

Gender-dependent specific immune response during chronic human Schistosomiasis haematobia.

The cellular and humoral acquired immune responses to Schistosoma haematobium 28 kD gluthathione S-Transferase (Sh28GST) antigen were evaluated in a Senegalese population chronically infected with S. haematobium parasite. We show a gender-dependent immune response in adult individuals presenting similar intensities of infection. Indeed, the specific IgA response and production of TGF-beta and IL-10 were found significantly higher in females compared to males. In addition, we showed that this profile was combined with a weak production of Th1-related cytokines (TNFalpha and IFNgamma) and was associated with an absence of proliferation to the antigen. A significantly higher Nuclear Matrix Protein 41/7 secretion, an apoptosis marker, was specifically observed in mononuclear blood cell cultures of females suggesting that a specific cell death process was engaged in a gender-dependent manner. This specific profile could be associated with the so-called T helper type-3 (Th3) immune response specifically promoting the production of IgA and would be developed upon the down-regulation of the specific Type-1 response by a probable cell death mechanism. This gender-dependent immune regulation, which may be under the influence of nonimmunological factors like sexual hormones, may be related to the chronicity of the infection.

Vaccine strategies against schistosomiasis: from concepts to clinical trials.

Schistosomiasis, the second major parasitic disease in the world after malaria, affects 200 million people. Vaccine strategies represent an essential component of the control of this chronic debilitating disease where the deposition of millions of eggs in the tissues is the main cause of pathology. Research developed in our laboratory over the last 20 years has led to the identification of novel effector mechanisms, pointing for the first time to the protective role of Th2 responses and of IgE antibodies now supported by seven studies in human populations. The identification and molecular cloning of a target antigen, a glutathione S-transferase (GST), has made it possible to demonstrate its vaccine potential in several animal species (rodents, cattle, primates) and to establish consistently the capacity of vaccination to reduce female worm fecundity and egg viability through the production of neutralizing antibodies (IgA and IgG). Following promising preclinical studies, clinical trials (phase I and II) have been undertaken using Schistosoma haematobium GST, Sh28GST. High titers of neutralizing antibodies were produced (IgG3 and IgA) together with Th2 cytokines, consistently with the concepts developed from experimental models. With these results we are on the way towards a feasible approach of vaccine development against a major human parasitic disease.

Immunostimulatory effect of IL-18-encoding plasmid in DNA vaccination against murine Schistosoma mansoni infection.

In vivo delivery of DNA encoding antigens is a simple tool to induce immune responses against pathogens. This approach to vaccination also offers the possibility to codeliver plasmids encoding immunomodulatory molecules in order to drive immune responses towards optimal protective effects. In the murine model of Schistosoma mansoni infection, vaccination inducing a Th1 profile has been shown to be protective. In this study, we used a plasmid encoding the Th1-promoting cytokine IL-18, since we observed that percutaneous infection of Balb/c mice strongly induced the production of IL-18 mRNA in the skin. Intradermal injection of the IL-18-encoding plasmid prior to infection did not interfere with parasite migration through the skin although it led to a local and transient cellular infiltration. When the IL-18-encoding plasmid was codelivered with a S. mansoni glutathione S-transferase (Sm28GST)-encoding plasmid, a 30-fold increase of antigen-specific IFN-gamma secretion by spleen cells was observed in comparison to spleen cells from mice that had received only the Sm28GST-encoding plasmid. This immunostimulatory effect was related to a significant protective effect (28% reduction in egg laying and 23% reduction in worm burden) which was attributed to a cooperative effect between both plasmids. Therefore, this study shows that codelivery of an IL-18-encoding plasmid with an antigen-encoding plasmid can stimulate specific cellular responses and induce protective effects against S. mansoni infection.

[Predictive ultrasonographic criteria for portal hypertension due to Schistosoma mansoni in a recently established endemiz zone]. / Critères echographiques prédictifs d'hypertension portale due à Schistosoma mansoni dans une zone d'endémie récente.

The first cases of Schistosoma mansoni infection were reported in the Senegal River Basin ten years ago. Today endemicity is so high that prevalence rates exceed 90 p. 100 in some areas. Schistosomiasis sometimes goes undiagnosed until the occurrence of portal hypertension with rupture of esophageal varices. Endoscopy is the gold standard for detection of esophageal varices but it is impractical in remote areas. Ultrasonography has been proposed as a non-invasive alternative. The purpose of this study is to describe the results of simultaneous endoscopic and ultrasonographic assessment in 101 subjects from the Richard-Toll area of the Senegal River Basin. Findings showed that severe forms of schistosomiasis complicated by portal hypertension were already present in the region less 10 years after description of the first case. This study also proposes a diagnostic score for portal hypertension based on ultrasonographic findings. The features included in this score are thickening of portal vessel walls, portal vessel diameter, and collapsed appearance of the splenic vein during inspiration. In our hands this score allowed reliable prediction of the development of esophageal varices. Ultrasonography is a good tool for identifying severe forms of schistosomiasis. It should be useful for routine screening in recently established endemic zones.

Interleukin-18 modulates immune responses induced by HIV-1 Nef DNA prime/protein boost vaccine.

Many different HIV-1 vaccine strategies have been developed, but as yet none has been completely successful. Promising results from combined DNA prime/protein boost vaccines have been reported. Specific immune responses generated by DNA vaccines can be modulated by the co-delivery of genes coding for cytokines. In this study, we have used the intradermal route by needle injection of a plasmid coding for the HIV-1 Nef accessory protein. We show that DNA prime/protein boost vaccine combinations increase the humoral and cellular immune responses against HIV-1 Nef and that the co-injection of DNA encoding Interleukin-18 (IL-18) modulates the specific immune response towards a Th1 type.