Activation of the NF κ B Pathway Enhances AhR Expression in Intestinal Caco-2 Cells.

Recent data suggest that apart from its well-known role in the regulation of xenobiotic metabolizing enzymes, AhR is also involved in inflammation. However, the influence of inflammation on AhR expression remains unknown. Here, we demonstrated that proinflammatory conditions induced by either PMA or IL-1 ß enhance AhR expression in Caco-2 cells. This was associated with an increase in AhR promoter activity. By means of directed mutagenesis experiments and the use of proteasome inhibitors, we demonstrated that inflammation-induced AhR expression involved the NF κ B pathway but not AP-1. Moreover, conditioned media from PMA-treated Caco-2 cells were also able to induce AhR expression, and this induction was repressed by anti-IL-1 ß blocking antibodies. Similar results were obtained with conditioned media from PMA-treated THP-1 cells. Taken together, these data suggest that AhR could be involved in vivo in an inflammatory loop. AhR was recently suspected to be implicated in inflammatory bowel disease. Our results support this hypothesis and suggest that AhR could be a new target for inflammatory bowel disease patient management.

[Experimental infection of goats with Schistosoma bovis and S. curassoni: comparative pathogenic effects]. / Infestation expérimentale de caprins par Schistosoma bovis et S. curassoni: effets pathogènes comparés.

Specific mortality and morbidity have been quantified in goats experimentally infected with Schistosoma bovis or S. curassoni strains from Niger. The study involved nine animals followed during 380 days after infection with, respectively, 1,800 or 2,400 cercariae. S. bovis was significatively more pathogenic than S. curossoni in terms of mortality, weight loss and packed cell volume decrease. In addition, the intensity of clinical symptoms was significatively and positively correlated to the levels of fecal egg excretion. Compared to non-infected controls, a growth differential of, respectively, 1,600 and 880 grams per month should incite to consider S. bovis and S. curassoni as parasites of serious economical impact in sahelian countries.

The influence of mating system, demography, parasites and colonization on the population structure of Biomphalaria pfeifferi in Madagascar.

Current evolutionary forces and historical processes interact to shape the distribution of neutral genetic variability within and among populations. Focusing on the genetics of recently introduced organisms offers a good opportunity to understand the relative importance of these factors. This study concerns variation at 8 polymorphic microsatellite loci in 30 populations of Biomphalaria pfeifferi. The sampling area spans most of the species' range in Madagascar where it was probably introduced recently. Extremely low variation was found within all populations studied, which may partly result from high selfing rates. However, this cannot account for the variance of variation across populations, which is better explained by habitat openness (that reflects environmental stochasticity), the prevalence of the parasitic trematode Schistosoma mansoni and historical demography (colonization and subsequent bottlenecks). Large global differentiation was also observed, suggesting that current gene flow among populations is limited to small distances, within watersheds and to few individuals. Our data set also allowed us to test several hypotheses regarding colonization, based on bottleneck and admixture tests. The observed pattern requires at least two independent introductions from slightly differentiated genetic sources in the western part of Madagascar. Another introduction, from a very different genetic origin, should also be postulated to explain the genetic composition of eastern populations. That this introduction occurred recently suggests that the colonization of Madagascar by B. pfeifferi is an ongoing process.

A spatial and temporal approach to microevolutionary forces affecting population biology in the freshwater snail Biomphalaria pfeifferi.

The limitations of both population demography and genetics highlight the need to combine these approaches when inferring the influence of demographic processes and modes of migration on genetic structure. The aim of this study was to use spatiotemporal genetic and demographic surveys to reveal the microevolutionary forces acting on the metapopulation dynamics of the freshwater snail Biomphalaria pfeifferi. We also analyzed the consequences of population turnover on temporal genetic differentiation, an aspect that has been little explored. Genetic drift was revealed by both the demographic survey, which indicated severe bottlenecks or extinction during the rainy (resp. dry) season in open (resp. closed) habitats, and the genetic approach, which indicated high selfing rates and strong temporal differentiation. Genetic reassignments and temporal differentiation both confirmed the results of the demographic survey, which suggests that migration occurs in closed (resp. open) habitats during the hot and dry (resp. rainy) season, and indicated that source-sink functioning may be envisaged. A propagule pool mode of colonization was inferred in the open habitats during the rainy season and a migrant pool in the closed habitats during the dry season. Our study also suggests that selection might be inferred from patterns of neutral genetic markers when recombination is limited.

Evolutionary relationships and biogeography of Biomphalaria (Gastropoda: Planorbidae) with implications regarding its role as host of the human bloodfluke, Schistosoma mansoni.

The wide geographic distribution of Schistosoma mansoni, a digenetic trematode and parasite of humans, is determined by the occurrence of its intermediate hosts, freshwater snails of the genus Biomphalaria (Preston 1910). We present phylogenetic analyses of 23 species of Biomphalaria, 16 Neotropical and seven African, including the most important schistosome hosts, using partial mitochondrial ribosomal 16S and complete nuclear ribosomal ITS1 and ITS2 nucleotide sequences. A dramatically better resolution was obtained by combining the data sets as opposed to analyzing each separately, indicating that there is additive congruent signal in each data set. Neotropical species are basal, and all African species are derived, suggesting an American origin for the genus. We confirm that a proto-Biomphalaria glabrata gave rise to all African species through a trans-Atlantic colonization of Africa. In addition, genetic distances among African species are smaller compared with those among Neotropical species, indicating a more recent origin. There are two species-rich clades, one African with B. glabrata as its base, and the other Neotropical. Within the African clade, a wide-ranging tropical savannah species, B. pfeifferi, and a Nilotic species complex, have both colonized Rift Valley lakes and produced endemic lacustrine forms. Within the Neotropical clade, two newly acquired natural hosts for S. mansoni (B. straminea and B. tenagophila) are not the closest relatives of each other, suggesting two separate acquisition events. Basal to these two species-rich clades are several Neotropical lineages with large genetic distances between them, indicating multiple lineages within the genus. Interesting patterns occur regarding schistosome susceptibility: (1) the most susceptible hosts belong to a single clade, comprising B. glabrata and the African species, (2) several susceptible Neotropical species are sister groups to apparently refractory species, and (3) some basal lineages are susceptible. These patterns suggest the existence of both inherent susceptibility and resistance, but also underscore the ability of S. mansoni to adapt to and acquire previously unsusceptible species as hosts. Biomphalaria schrammi appears to be distantly related to other Biomphalaria as well as to Helisoma, and may represent a separate or intermediate lineage.

Bulinus species on Madagascar: molecular evolution, genetic markers and compatibility with Schistosoma haematobium.

Of the four species of Bulinus found on Madagascar, three species: B. obtusispira, B. liratus and B. bavayi are endemic while the fourth, B. forskalii, is probably a recent introduction from the African mainland. The evolutionary relationships of these species with Bulinus species from Africa were studied by phylogenetic analysis of DNA sequence variation at two mitochondrial loci: cytochrome oxidase subunit I (COI) and large ribosomal subunit (LSU) or 16S. The observed levels of nucleotide divergence within Bulinus were substantial but may underestimate the true levels as there was evidence of 'saturation' of transitional substitutions at both loci. A putative secondary structure model for the sequenced segment of the 16S was developed. Subsequent phylogenetic analysis using transversional changes only for both loci, showed that there were contrasting levels of divergence within the four species groups. B. obtusispira was consistently placed within the B. africanus group, appearing ancestral to this group and was closest to the basal node within Bulinus. Together with B. bavayi, the two species appear to have been isolated on Madagascar for a long time, contrasting with both B. liratus and B. forskalii that appear more recent colonisers; however, estimate of exact times of divergence is problematic. A PCR-RFLP assay was developed to enable identification and discrimination of B. obtusispira and B. liratus using discriminatory variation within the COI. To enable population genetic analysis within B. obtusispira, microsatellite markers were developed using an enrichment method and 8 primer pairs are reported. Laboratory infection experiments using Madasgacan S. haematobium from the Mahabo area showed that certain populations of B. obtusispira, B. liratus and B. bavayi were compatible.

The WHO collaborating centre for research and control of schistosomiasis at Niamey, Niger

The Centre de Recherche sur les Meningites et les Schistosomes (CERMES) is a research institute depending on the Organisation de Coordination et de Cooperation pour la lutte contre les Grandes Endemies - a West African Organisation for Public Health - devoted to the studies on schistosomiasis and meningitis. The staff includes 32 persons with 11 scientists and one financial officer. The activities of the CERMES involving schistosomiasis concern three research units: (a) ecology of human and animal schistosomiasis transmission: the CERMES defined the different patterns of schistosomiasis transmission in Niger (involving African dry savana); in this field, we have shown, (i) the existence of important variability in conditions of transmission of S. haematobium and, (ii) natural hybridization between parasite species of the ruminants (s. bovis and S. curassoni) and genetic interaction between human and animal parasites; (b) definition of morbidity indicators usable for rapid assessment methods, for appraisal of the severity of the disease and for the evaluation of the efficiency of control methods; we have established the correlation between ultrasonographic data and some cheap and sample field indicators; (c) immune response and protective immunity by recombinant glutathion S-transferase (Sm28, Sb28 and Sh28) in homologous and heterologous animal including goats, sheep and non human primates (Erythocebus patas). In Niger, we participate in all control programs against schistosomiasis to define control strategies, to supervise operations and to participate in their evaluation with external experts. International collaborations constitute a frame including four laboratories in Africa and six labotatories in developed countries (Europe and USA).

Comparison of human and murine isolates of Schistosoma mansoni from Richard-Toll, Senegal, by isoelectric focusing.

Studies on human and murine isolates of Schistosoma mansoni, from Richard-Toll, Senegal, were carried out by isoelectric focusing in polyacrylamide gels. Seven enzyme systems; lactate dehydrogenase (LDH), malate dehydrogenase (MDH), glucose-6-phosphate dehydrogenase (G6PD), acid phosphatase (AcP), hexokinase (HK), glucose phosphate isomerase (GPI), and phosphoglucomutase (PGM), were used to compare the two isolates. All systems tested, apart from LDH, were found to be polymorphic for both isolates. Interestingly, one phenotype is more frequent than the remainder. The results show that there is no significant genetic variation between the S. mansoni isolates from man and the rodents, Arvicanthis niloticus and Mastomys huberti.

Intraspecific diversity of Schistosoma haematobium in west Africa: chronobiology of cercarial emergence.

Cercarial emergence patterns were used to analyse the intraspecific variability within and between nine populations of Schistosoma haematobium collected along a transect line from the north to the South of the Ivory Coast (Africa) and using Bulinus truncatus or Bulinus globosus as intermediate snail hosts. Statistical comparison demonstrated the existence of a chronobiological polymorphism and the existence of three homogeneous groups of S. haematobium isolates with mean shedding times of the cercariae decreasing from the North to the South. The chronobiological variability observed was not correlated with the species of Bulinus (B. truncatus vs. B. globosus) implicated in the parasite transmission but with the climatic and vegetal features of the transmission area. S. haematobium from shaded sites of the forest zone (South) showed cercarial emergence patterns significantly earliest than that of S. haematobium from open sites of the savanna zone (North). Differences in sensitivity to light intensity could characterize the existence of eco-geographical races of S. haematobium one of the forest, the other from the savanna.

The WHO Collaborating Centre for Research and Control of Schistosomiasis at Niamey, Niger.

The Centre de Recherche sur les Méningites et les Schistosomes (CERMES) is a research institute depending on the Organisation de Coordination et de Coopération pour la lutte contre les Grandes Endémies--a West African Organization for Public Health--devoted to the studies on schistosomiasis and meningitis. The staff includes 32 persons with 11 scientists and one financial officer. The activities of the CERMES involving schistosomiasis concern three research units: (a) ecology of human and animal schistosomiasis transmission; the CERMES defined the different patterns of schistosomiasis transmission in Niger (involving African dry savana); in this field, we have shown, (i) the existence of important variability in conditions of transmission of S. haematobium and, (ii) natural hybridization between parasitic species of the ruminants (S. bovis and S. curassoni) and genetic interaction between human and animal parasites; (b) definition of morbidity indicators usable for rapid assessment methods, for appraisal of the severity of the disease and for the evaluation of the efficiency of control methods; we have established the correlation between ultrasonographic data and some cheap and simple field indicators; (c) immune response and protective immunity induced by recombinant glutathion S-transferase (Sm28, Sb28 and Sh28) in homologous and heterologous animal models including goats, sheep and non human primates (Erythrocebus patas). In Niger, we participate in all control programs against schistosomiasis to define control strategies, to supervise operations and to participate in their evaluation with external experts. International collaborations constitute a frame including four laboratories in Africa and six laboratories in developed countries (Europe and USA).

PIP: The Centre de Recherche sur les Meningites et les Schistosomoses (CERMES), a research center in Niamey, Niger, affiliated with a West African public health organization, conducts studies in the areas of parasitology, epidemiology, and immunology. Significant variability in factors related to transmission of Schistosoma haematobium have been noted. Experimental research on the Schistosoma-bulinid compatibility and field surveys of the geographic distribution and role of snails in transmission have been essential to the design of parasite control interventions in West Africa. A CERMES-sponsored project, supported by the European Community, is examining urinary schistosomiasis control in the Niger river valley and the impact of treatment on ultrasonically visualized urologic lesions. The Experimental Vaccine Unit seeks to improve the route of administration and choice of adjuvant and to propose a vaccine protocol for field testing. Recombinant proteins have been found to alter the development of the parasite either by inducing a reduction in the parasite burden or an inhibition of the fecundity of the parasite.

Microsatellites and the genetics of highly selfing populations in the freshwater snail Bulinus truncatus.

Hermaphrodite tropical freshwater snails provide a good opportunity to study the effects of mating system and genetic drift on population genetic structure because they are self-fertile and they occupy transient patchily distributed habitats (ponds). Up to now the lack of detectable allozyme polymorphism prevented any intrapopulation studies. In this paper, we examine the consequences of selfing and bottlenecks on genetic polymorphism using microsatellite markers in 14 natural populations (under a hierarchical sampling design) of the hermaphrodite freshwater snail Bulinus truncatus. These population genetics data allowed us to discuss the currently available mutation models for microsatellite sequences. Microsatellite markers revealed an unexpectedly high levels of genetic variation with < or = 41 alleles for one locus and gene diversity of 0.20-0.75 among populations. The values of any estimator of Fis indicate high selfing rates in all populations. Linkage disequilibria observed at all loci for some populations may also indicate high levels of inbreeding. The large extent of genetic differentiation measured by Fst, Rst or by a test for homogeneity between genic distributions is explained by both selfing and bottlenecks. Despite a limited gene flow, migration events could be detected when comparing different populations within ponds.

The genetical and environmental determination of phally polymorphism in the freshwater snail Bulinus truncatus.

In some species of self-fertile pulmonate snails, two sexual morphs co-occur in natural populations: regular individuals and aphallic individuals that cannot transmit sperm to other snails. Purely aphallic populations therefore reproduce obligatorily by selfing. Understanding the evolution of aphally and selfing in these snails requires a precise knowledge of phally determination. In this paper, we investigate the genetic and environmental determination of aphally in Bulinus truncatus by a survey of the family (offspring) aphally ratio of 233 individuals originating from seven natural populations and a study of the reaction norm of the family aphally ratio to temperature using 60 individuals from 10 selfed lineages of one population. Our results indicate a high genetic variability for the determination of aphally between populations and within some populations, associated with a high level of genetic determination. Our second experiment indicates a significant temperature and lineage effect though no interaction between these two effects. We discuss our results in the framework of threshold models developed for dimorphic traits with polygenic inheritance. We propose that the sexual morph of an individual at a given temperature is determined by a temperature threshold value depending on both the individual genotype and probabilistic processes.

Vaccination of patas monkeys experimentally infected with Schistosoma haematobium using a recombinant glutathione S-transferase cloned from S. mansoni.

The capacity of a recombinant glutathione S-transferase from Schistosoma mansoni (rSm28GST) to vaccinate primates (Erythrocebus patas) against a heterologous infection with Schistosoma haematobium has been tested. Two injections of the purified molecule with Muramyl-Di-Peptide (MDP) as adjuvant resulted in a high level antibody response in the five immunized animals and in a significant reduction in worm fecundity compared to the controls which received adjuvant alone. Mean levels of daily egg excretion in urine an faeces were reduced by respectively 55% and 74% although perfusion revealed that worm burdens were similar in both groups. The protective effect was long lasting since it was maintained up to the end of the experiment, 42 weeks after infection. Hatching rates and the numbers of intra-uterine eggs were also significantly affected by the vaccination. Tissue eggs were also drastically diminished in the urogenital system (-80%) but the reduction was not statistically significant. One animal was not protected by the immunization. There was a good correlation between parasitological data and the intensity of bladder lesions assessed by microscopic examination. Polypoid formations together with an intense exudation of the lamina propria were frequently seen in the controls but rarely in the vaccinated group where formation of scar tissue was predominant. These results underline the vaccine potential of the recombinant Sm28GST as a possible valuable prophylactic tool for the control of egg-induced pathology and transmission of African schistosomes.

Vaccination of goats against the trematode Schistosoma bovis with a recombinant homologous schistosome-derived glutathione S-transferase.

We assayed the vaccine potentialities of a recombinant S. bovis-derived glutathione S-transferase (rSb28GST), member of a molecular family already shown to have protective capacities in the S. mansoni and S. japonicum models. Injection of the rSb28GST in Freund's Complete Adjuvant resulted in good specific IgG responses allowing all the animals to display high antibody titres on the day of experimental challenge with S. bovis cercariae. No statistically significant differences were observed in the faecal egg output. Although tissue egg counts in vaccinated animals were lower than in controls, the difference was not statistically significant, apart from the number of eggs trapped in the liver (P < 0.05). Likewise, PCV values remained parallel between the two groups. However, immunized goats gained 1.4 kg of body weight throughout the experiment whereas controls lost 1.2 kg (P < 0.05). In addition, the mean worm burden, assessed by perfusion 20 weeks after infection, was significantly reduced by 48% in the vaccinated group, the sex ratio being unaffected. It appears that a recombinant homologous protein can affect, in a natural host, the course of an experimental infection with a local strain of S. bovis, by affecting worm viability but not fecundity. These results also point to the striking differences in the effect of vaccination according to animal species. Because it has the capacity to prevent growth impairment due to schistosome pathogenicity, the molecule can be proposed as a valuable tool in the development of vaccine-based control programs in endemic areas.

[Arguments for the modification of the genome (introgression) of the human parasite Schistosoma haematobium by genes from S. bovis, in Niger]. / Arguments en faveur d'une modification du génome (introgression) du parasite humain Schistosoma haematobium par des gènes de S. bovis, au Niger.

Characterization of schistosome populations from human in eastern Niger, through intra-uterine egg morphology of female parasites and phenotopic analyses of worms observed for acid phosphatase using electrophoretic separation, renders results that suggest an intogression of S. haematobium from man by genes of S. bovis, a parasite of domestic livestock. The origin of this introgression, that could implicate S. curassoni as well, another livestock parasite that hybridize with S. bovis, is discussed.

Experimental host-induced selection in Schistosoma mansoni strains from Guadeloupe and comparison with natural observations.

Allelic frequency variation at the malate dehydrogenase (E.C.1.1.1.37) polymorphic locus (Mdh-1) was analysed during several successive generations in four strains of Schistosoma mansoni from Guadeloupe, maintained experimentally on mice. A rapid evolution of the frequency of the Mdh-1a allele is interpreted as being the result of an interaction between experimental drift and selection induced by the murine laboratory host. These experimental results are compared to the genetic structures observed among the corresponding natural populations of S. mansoni in Guadeloupe (West Indies). They strengthen the hypothesis of a natural host-induced selection by the murine host (Rattus rattus), which, in Guadeloupe, plays the role of host reservoir for this human schistosome.

Pattern of cercarial emergence of Schistosoma curassoni from Niger and comparison with three sympatric species of schistosomes.

The emergence pattern of Schistosoma curassoni cercariae from Bulinus umbilicatus, whose adult worms parasitize bovine, caprine, and ovine ungulates in Niger, is of a circadian type with a mean emission time at 0855 hr +/- 1 hr 6 min, characteristic of the schistosome species parasitizing domestic or wild cattle. The comparison of this cercarial emergence pattern with those of the other 3 sympatric species of schistosomes (Schistosoma haematobium, Schistosoma bovis, and Schistosoma mansoni) shows a significant difference between the chronobiology of the cercariae infective for human and those infective for bovine hosts. This difference may improve epidemiological surveys based on snail prevalences by allowing the distinction between bulinids infected with human and bovine parasites.