Genomic evidence of contemporary hybridization between Schistosoma species

Hybridization between different species of parasites is increasingly being recognised as a major public and veterinary health concern at the interface of infectious diseases biology, evolution, epidemiology and ultimately control. Recent research has revealed that viable hybrids and introgressed lineages between Schistosoma spp. are prevalent across Africa and beyond, including those with zoonotic potential. However, it remains unclear whether these hybrid lineages represent recent hybridization events, suggesting hybridization is ongoing, and/or whether they represent introgressed lineages derived from ancient hybridization events. In human schistosomiasis, investigation is hampered by the inaccessibility of adult-stage worms due to their intravascular location, an issue which can be circumvented by post-mortem of livestock at abattoirs for Schistosoma spp. of known zoonotic potential. To characterise the composition of naturally-occurring schistosome hybrids, we performed whole-genome sequencing of 21 natural livestock infective schistosome isolates. To facilitate this, we also assembled a de novo chromosomal-scale draft assembly of Schistosoma curassoni. Genomic analyses identified isolates of S. bovis, S. curassoni and hybrids between the two species, all of which were early generation hybrids with multiple generations found within the same host. These results show that hybridization is an ongoing process within natural populations with the potential to further challenge elimination efforts against schistosomiasis.

Schistosomiasis is a chronic and debilitating major neglected tropical disease affecting both humans and livestock. Increasingly, zoonotic spillover of livestock infections, facilitated by hybridization between different Schistosoma species, is increasingly being recognised as a risk to human health. Multiple surveys conducted within endemic regions have found a high prevalence of these hybrid lineages. However, it is often unclear whether these lineages are derived from recent hybridization events, suggesting hybridization is ongoing and may be linked to anthropogenic environmental change, or simply indicators of introgression from ancient hybridization events. To understand the origin and evolution of these hybrid lineages, we produced a chromosomal-scale assembly of Schistosoma curassoni and performed whole-genome sequencing of 21 natural livestock-infective S. curassoni, S. bovis and hybridized schistosome isolates, including multi-stage sampling from the same hosts. Our analyses exclusively identified early generation hybrid lineages, including multiple unrelated generations within the same hosts, suggesting that these hybrids are viable and derived from multiple independent hybridization events.

Interleukin-13 rs1800925/-1112C/T promoter single nucleotide polymorphism variant linked to anti-schistosomiasis in adult males in Murehwa District, Zimbabwe

Background

Chronic schistosomiasis is predominantly induced through up-regulation of inflammatory cytokines such as interleukin (IL)-13. IL-13 may contribute to the disease outcomes by increasing eosinophil infiltration thereby promoting fibrosis. IL-13 may act as an immunosuppressive inflammatory cytokine that may promote carcinogenesis and also may offer protection against schistosomiasis thereby reducing risk of schistosome infections. Our study evaluated the frequency of the IL-13 rs1800925/-1112 C/ T promoter single nucleotide polymorphisms (SNPs) among schistosomiasis infected individuals and assessed the association of the variants on IL-13 cytokine levels. We also investigated IL-13 rs1800925 polymorphisms on prostate-specific antigen levels as an indicator for risk of prostate cancer development.

Methodology

The study was cross-sectional and included 50 schistosomiasis infected and 316 uninfected male participants residing in Murehwa District, Zimbabwe. IL-13 rs1800925 SNPs were genotyped by allele amplification refractory mutation system-polymerase chain reaction. Concentrations of serum prostate-specific antigens and plasma IL-13 were measured using enzyme-linked immunosorbent assay.

Results

Frequencies of the genotypes CC, CT and TT, were 20%, 58% and 22% in schistosomiasis infected, and 18.3%, 62.1% and 19.6% in uninfected participants with no statistical differences. There were significantly (p<0.05) higher IL-13 cytokine levels among both infected and uninfected participants with the genotypes CC and CT; median 92.25 pg/mL and 106.5 pg/mL, respectively, compared to TT variant individuals; 44.78 pg/mL. Within the schistosomiasis uninfected group, CC and CT variants had significantly (p<0.05) higher IL-13 levels; median 135.0 pg/mL and 113.6 pg/mL, respectively compared to TT variant individuals; 47.15 pg/mL. Within the schistosomiasis infected group, CC, CT and TT variant individuals had insignificant differences of IL-13 level. Using logistic regression, no association was observed between prostate-specific antigen levels, IL-13 cytokine levels and IL-13 rs1800925 variants (p>0.05).

Conclusion

IL-13 rs1800925 C variant individuals had the highest IL-13 cytokine levels among the schistosomiasis uninfected suggesting that they may be protective against Schistosoma infections. There was no association between IL-13 concentrations or IL-13 rs1800925 variants and risk of prostate cancer indicating that IL-13 levels and IL-13 rs10800925 may not be utilised as biomarker for risk of prostate cancer in schistosome infections.

Diverging patterns of introgression from Schistosoma bovis across S. haematobium African lineages

Hybridization is a fascinating evolutionary phenomenon that raises the question of how species maintain their integrity. Inter-species hybridization occurs between certain Schistosoma species that can cause important public health and veterinary issues. In particular hybrids between Schistosoma haematobium and S. bovis associated with humans and animals respectively are frequently identified in Africa. Recent genomic evidence indicates that some S. haematobium populations show signatures of genomic introgression from S. bovis. Here, we conducted a genomic comparative study and investigated the genomic relationships between S. haematobium, S. bovis and their hybrids using 19 isolates originating from a wide geographical range over Africa, including samples initially classified as S. haematobium (n = 11), S. bovis (n = 6) and S. haematobium x S. bovis hybrids (n = 2). Based on a whole genomic sequencing approach, we developed 56,181 SNPs that allowed a clear differentiation of S. bovis isolates from a genomic cluster including all S. haematobium isolates and a natural S. haematobium-bovis hybrid. All the isolates from the S. haematobium cluster except the isolate from Madagascar harbored signatures of genomic introgression from S. bovis. Isolates from Corsica, Mali and Egypt harbored the S. bovis-like Invadolysin gene, an introgressed tract that has been previously detected in some introgressed S. haematobium populations from Niger. Together our results highlight the fact that introgression from S. bovis is widespread across S. haematobium and that the observed introgression is unidirectional.

Hybridization is a fascinating evolutionary phenomenon that raises the question of how species maintain their integrity. Inter-species hybridization occurs between certain Schistosoma species that can cause important public health and veterinary issues. In particular hybrids between Schistosoma haematobium and S. bovis associated with humans and animals respectively are frequently identified in Africa. Recent genomic evidence indicates that some S. haematobium populations show signatures of genomic introgression from S. bovis. Here we conducted a comparative genomic study to assess the genomic diversity within S. haematobium and S. bovis species and genetic differentation at the genome scale between these two sister species over the African continent. We also investigated traces of possible ancient introgression from one species to another. We found that S. haematobium display low genetic diversity compared to S. bovis. We also found that most S. haematobium samples harbor signature of past introgression with S. bovis at some genomic positions. Our results strongly suggest that introgression occurred long time ago and that such introgression is unidirectional from S. bovis within S. haematobium. Such introgresssion event(s) result in diverging patterns of genomic introgression across S. haematobium lineages.

Down-regulation of microRNA-203-3p initiates type 2 pathology during schistosome infection via elevation of interleukin-33

The type 2 immune response is the central mechanism of disease progression in schistosomiasis, but the signals that induce it after infection remain elusive. Aberrant microRNA (miRNA) expression is a hallmark of human diseases including schistosomiasis, and targeting the deregulated miRNA can mitigate disease outcomes. Here, we demonstrate that efficient and sustained elevation of miR-203-3p in liver tissues, using the highly hepatotropic recombinant adeno-associated virus serotype 8 (rAAV8), protects mice against lethal schistosome infection by alleviating hepatic fibrosis. We show that miR-203-3p targets interleukin-33 (IL-33), an inducer of type 2 immunity, in hepatic stellate cells to regulate the expansion and IL-13 production of hepatic group 2 innate lymphoid cells during infection. Our study highlights the potential of rAAV8-mediated miR-203-3p elevation as a therapeutic intervention for fibrotic diseases.

Host regulation of liver fibroproliferative pathology during experimental schistosomiasis via interleukin-4 receptor alpha

Interleukin-4 receptor (IL-4Rα) is critical for the initiation of type-2 immune responses and implicated in the pathogenesis of experimental schistosomiasis. IL-4Rα mediated type-2 responses are critical for the control of pathology during acute schistosomiasis. However, type-2 responses tightly associate with fibrogranulomatous inflammation that drives host pathology during chronic schistosomiasis. To address such controversy on the role of IL-4Rα, we generated a novel inducible IL-4Rα-deficient mouse model that allows for temporal knockdown of il-4rα gene after oral administration of Tamoxifen. Interrupting IL-4Rα mediated signaling during the acute phase impaired the development of protective type-2 immune responses, leading to rapid weight loss and premature death, confirming a protective role of IL-4Rα during acute schistosomiasis. Conversely, IL-4Rα removal at the chronic phase of schistosomiasis ameliorated the pathological fibro-granulomatous pathology and reversed liver scarification without affecting the host fitness. This amelioration of the morbidity was accompanied by a reduced Th2 response and increased frequencies of FoxP3⁺ Tregs and CD1d^hiCD5⁺ Bregs. Collectively, these data demonstrate that IL-4Rα mediated signaling has two opposing functions during experimental schistosomiasis depending on the stage of advancement of the disease and indicate that interrupting IL-4Rα mediated signaling is a viable therapeutic strategy to ameliorate liver fibroproliferative pathology in diseases like chronic schistosomiasis.

Liver fibroproliferative diseases drive a considerable fraction of the overall human mortality. This is closely linked to the absence of efficient control measures against such diseases. Schistosomiasis, a chronic disease that affects humans, preferentially causes liver fibrosis and is responsible for devastating economic losses in developing nations where the disease is still endemic. Using reverse genetics, loss-of-function mouse models have helped uncover a protective role for Interleukin-4 receptor (IL-4Rα) in the host survival to experimental schistosomiasis. However, given the contributing role for this receptor in the etiology of some models of tissue fibrosis, its role during chronic schistosomiasis where the highly fibrotic liver of the infected individuals mediate the morbidity had not been properly addressed hitherto. Taking advantage of a third generation mouse model of inducible loss of a gene, we found a debilitating role for IL-4 receptor during chronic schistosomiasis as signaling via this receptor supported both liver inflammation and fibrosis. These findings demonstrate that although the host requires IL-4Rα to survive the acute phase of schistosomiasis, the more clinically relevant morbid phase of the disease is driven by the excessive utilization of this receptor. A therapeutic potential of blocking IL-4Rα to ameliorate liver fibroproliferative disease is therefore suggested.

Association Between Polymorphisms of the Mannose-Binding Lectin and Severity of Periportal Fibrosis in Schistosomiasis, in the Northeast of Brazil

AIMS

Mannose-binding lectin (MBL) is a protein synthesized by the liver and its immune response is associated with the development of liver fibrosis. We hypothesized that the polymorphisms in the Exon 1 region (52, 54, 57) and promoter regions (-550 H/L, -221 X/Y) of the MBL2 gene were associated with the severity of periportal fibrosis (PPF), and that these polymorphisms affect the MBL serum levels.

MATERIALS AND METHODS

In this cross-sectional study we genotyped these polymorphisms within the MBL2 gene in 229 Brazilian subjects infected with Schistosoma mansoni, with different patterns of PPF.

RESULTS

There was no association between the polymorphisms and haplotypes of the MBL2 gene and the advanced PPF pattern. The MBL levels were higher in individuals with advanced fibrosis. There was risk association among high-expression haplotypes of MBL, and a protection association between the A/O Exon 1 genotype and elevated MBL serum levels.

CONCLUSIONS

Our results suggest that polymorphism of Exon 1 and MBL haplotypes could potentially be used to predict the severity of advanced PPF in the Brazilian population.

The role of ST2 and ST2 genetic variants in schistosomiasis

BACKGROUND

Chronic schistosomiasis and its severe complication, periportal fibrosis, are characterized by a predominant T_h2 response. To date, specific single nucleotide polymorphisms in ST2 have been some of the most consistently associated genetic variants for asthma.

OBJECTIVE

We investigated the role of ST2 (a receptor for the T_h2 cytokine IL-33) in chronic and late-stage schistosomiasis caused by Schistosoma japonicum and the potential effect of ST2 genetic variants on stage of disease and ST2 expression.

METHODS

We recruited 947 adult participants (339 with end-stage schistosomiasis and liver cirrhosis, 307 with chronic infections without liver fibrosis, and 301 health controls) from a S japonicum-endemic area (Hubei, China). Six ST2 single nucleotide polymorphisms were genotyped. Serum soluble ST2 (sST2) was measured by ELISA, and ST2 expression in normal liver tissues, Hepatitis B virus-induced fibrotic liver tissues, and S japonicum-induced fibrotic liver tissues was measured by immunohistochemistry.

RESULTS

We found sST2 levels were significantly higher in the end-stage group (36.04 [95% CI, 33.85-38.37]) compared with chronic cases and controls (22.7 [95% CI, 22.0-23.4], P < 1E-10). In addition, S japonicum-induced fibrotic liver tissues showed increased ST2 staining compared with normal liver tissues (P = .0001). Markers rs12712135, rs1420101, and rs6543119 were strongly associated with sST2 levels (P = 2E-10, 5E-05, and 6E-05, respectively), and these results were replicated in an independent cohort from Brazil living in a S mansoni endemic region.

CONCLUSIONS

We demonstrate for the first time that end-stage schistosomiasis is associated with elevated sST2 levels and show that ST2 genetic variants are associated with sST2 levels in patients with schistosomiasis.

MicroRNAs Are Involved in the Regulation of Ovary Development in the Pathogenic Blood Fluke Schistosoma japonicum

Schistosomes, blood flukes, are an important global public health concern. Paired adult female schistosomes produce large numbers of eggs that are primarily responsible for the disease pathology and critical for dissemination. Consequently, understanding schistosome sexual maturation and egg production may open novel perspectives for intervening with these processes to prevent clinical symptoms and to interrupt the life-cycle of these blood-flukes. microRNAs (miRNAs) are key regulators of many biological processes including development, cell proliferation, metabolism, and signal transduction. Here, we report on the identification of Schistosoma japonicum miRNAs using small RNA deep sequencing in the key stages of male-female pairing, gametogenesis, and egg production. We identified 38 miRNAs, including 10 previously unknown miRNAs. Eighteen of the miRNAs were differentially expressed between male and female schistosomes and during different stages of sexual maturation. We identified 30 potential target genes for 16 of the S. japonicum miRNAs using antibody-based pull-down assays and bioinformatic analyses. We further validated some of these target genes using either in vitro luciferase assays or in vivo miRNA suppression experiments. Notably, suppression of the female enriched miRNAs bantam and miR-31 led to morphological alteration of ovaries in female schistosomes. These findings uncover key roles for specific miRNAs in schistosome sexual maturation and egg production.

Co-dispersal of the blood fluke Schistosoma japonicum and Homo sapiens in the Neolithic Age

The global spread of human infectious diseases is of considerable public health and biomedical interest. Little is known about the relationship between the distribution of ancient parasites and that of their human hosts. Schistosoma japonicum is one of the three major species of schistosome blood flukes causing the disease of schistosomiasis in humans. The parasite is prevalent in East and Southeast Asia, including the People's Republic of China, the Philippines and Indonesia. We studied the co-expansion of S. japonicum and its human definitive host. Phylogenetic reconstruction based on complete mitochondrial genome sequences showed that S. japonicum radiated from the middle and lower reaches of the Yangtze River to the mountainous areas of China, Japan and Southeast Asia. In addition, the parasite experienced two population expansions during the Neolithic agriculture era, coinciding with human migration and population growth. The data indicate that the advent of rice planting likely played a key role in the spread of schistosomiasis in Asia. Moreover, the presence of different subspecies of Oncomelania hupensis intermediate host snails in different localities in Asia allowed S. japonicum to survive in new rice-planting areas, and concurrently drove the intraspecies divergence of the parasite.

Regulatory networks, genes and glycerophospholipid biosynthesis pathway in schistosomiasis: a systems biology view for pharmacological intervention

Understanding network topology through embracing the global dynamical regulation of genes in an active state space rather than traditional one-gene-one trait approach facilitates the rational drug development process. Schistosomiasis, a neglected tropical disease, has glycerophospholipids as abundant molecules present on its surface. Lack of effective clinical solutions to treat pathogens encourages us to carry out systems-level studies that could contribute to the development of an effective therapy. Development of a strategy for identifying drug targets by combined genome-scale metabolic network and essentiality analyses through in silico approaches provides tantalizing opportunity to investigate the role of protein/substrate metabolism. A genome-scale metabolic network model reconstruction represents choline-phosphate cytidyltransferase as the rate limiting enzyme and regulates the rate of phosphatidylcholine (PC) biosynthesis. The uptake of choline was regulated by choline concentration, promoting the regulation of phosphocholine synthesis. In Schistosoma, the change in developmental stage could result from the availability of choline, hampering its developmental cycle. There are no structural reports for this protein. In order to inhibit the activity of choline-phosphate cytidyltransferase (CCT), it was modeled by homology modeling using 1COZ as the template from Bacillus subtilis. The transition-state stabilization and catalytic residues were mapped as 'HXGH' and 'RTEGISTT' motif. CCT catalyzes the formation of CDP-choline from phosphocholine in which nucleotidyltransferase adds CTP to phosphocholine. The presence of phosphocholine permits the parasite to survive in an immunologically hostile environment. This feature endeavors development of an inhibitor specific for cytidyltransferase in Schistosoma. Flavonolignans were used to inhibit this activity in which hydnowightin showed the highest affinity as compared to miltefosine.

[Expression characteristics of microRNA in mice with schistosomiasis and praziquantel treatment]

OBJECTIVE

To investigate the expression characteristics of miR-155 and miR-146a in mice with schistosomiasis and praziquantel (PZQ) treatment.

METHODS

Totally 40 BABL/c mice were divided into 4 groups: a normal group, a 6W infected group that were infected cutaneously with 10 Schistosoma japonicum cercariae for 6 weeks, a 12W infected group that were infected cutaneously with 10 Schistosoma japonicum cercariae for 12 weeks, and a praziquantel treated group that were infected cutaneously with 10 Schistosomajaponicum cercariae and intragastrically administered with PZQ (300 mg/kg/day) for 1 day in 6 weeks post-infection and continuing surviving 6 weeks. The animals were sacrificed in 6 weeks and 12 weeks post-infection respectively. The left front lobe of each liver was stained with hematoxylin-eosin (HE) to detect pathological lesions. The levels of mRNA expressions of miR-155, miR-146a and pro-inflammatory cytokines (TNF-alpha, IL-1beta and IL-6) in the liver tissue were determined by using quantitative real-time PCR.

RESULTS

The levels of mRNA expressions of miR-155, miR-146a and pro-inflammatory cytokines (TNF-alpha, IL-1beta and IL-6) in the 6W infected mice were significantly higher than those of the normal mice and of the 12W infected mice. Compared with the 12W infected mice, the inflammation response of liver egg granuloma in the PZQ-treated mice was ameliorated. Furthermore, there was a marked increase in the levels of mRNA expressions of miR-155, miR-146a and three pro-inflammatory cytokines in the PZQ-treated mice compared to the 12W infected mice.

CONCLUSION

miR-155 and miR-146a may play a role in schistosomiasis liver inflammation response and the inflammation regulation of praziquantel treatment.

Regulation of innate responses during pre-patent schistosome infection provides an immune environment permissive for parasite development

Blood flukes of the genus Schistosoma infect over 200 million people, causing granulomatous pathology with accompanying morbidity and mortality. As a consequence of extensive host-parasite co-evolution, schistosomes exhibit a complex relationship with their hosts, in which immunological factors are intimately linked with parasite development. Schistosomes fail to develop normally in immunodeficient mice, an outcome specifically dependent on the absence of CD4⁺ T cells. The role of CD4⁺ T cells in parasite development is indirect and mediated by interaction with innate cells, as repeated toll-like receptor 4 stimulation is sufficient to restore parasite development in immunodeficient mice in the absence of CD4⁺ T cells. Here we show that repeated stimulation of innate immunity by an endogenous danger signal can also restore parasite development and that both these stimuli, when administered repeatedly, lead to the regulation of innate responses. Supporting a role for regulation of innate responses in parasite development, we show that regulation of inflammation by neutralizing anti-TNF antibodies also restores parasite development in immunodeficient mice. Finally, we show that administration of IL-4 to immunodeficient mice to regulate inflammation by induction of type 2 responses also restores parasite development. These findings suggest that the type 2 response driven by CD4⁺ T cells during pre-patent infection of immunocompetent hosts is exploited by schistosomes to complete their development to reproductively mature adult parasites.

Induction and regulation of pathogenic Th17 cell responses in schistosomiasis

Schistosomiasis is a major tropical disease caused by trematode helminths in which the host mounts a pathogenic immune response against tissue-trapped parasite eggs. The immunopathology consists of egg antigen-specific CD4 T cell-mediated granulomatous inflammation that varies greatly in magnitude in humans and among mouse strains in an experimental model. New evidence, covered in this review, intimately ties the development of severe pathology to IL-17-producing CD4 T helper (Th17) cells, a finding that adds a new dimension to the traditional CD4 Th1 vs. Th2 cell paradigm. Most examined mouse strains, in fact, develop severe immunopathology with substantial Th17 as well as Th1 and Th2 cell responses; a solely Th2-polarized response is an exception that is only observed in low-pathology strains such as the C57BL/6. The ability to mount pathogenic Th17 cell responses is genetically determined and depends on the production of IL-23 and IL-1β by antigen presenting cells following recognition of egg antigens; analyses of several F2 progenies of (high × low)-pathology strain crosses demonstrated that quantitative trait loci governing IL-17 levels and disease severity vary substantially from cross to cross. Low pathology is dominant, which may explain the low incidence of severe disease in humans; however, coinfection with intestinal nematodes can also dampen pathogenic Th17 cell responses by promoting regulatory mechanisms such as those afforded by alternatively activated macrophages and T regulatory cells. A better understanding of the pathways conducive to severe forms of schistosomiasis and their regulation should lead to interventions similar to those presently used to manage other immune-mediated diseases.

Ficolin-2 levels and FCN2 genetic polymorphisms as a susceptibility factor in schistosomiasis

BACKGROUND

Human ficolin-2 (L-ficolins) encoded by the FCN2 gene are pattern-recognition proteins involved in innate immunity and are associated with several infectious diseases.

METHODS

A Nigerian cohort of 168 Schistosoma haematobium-infected individuals and 192 healthy controls were examined for functional single-nucleotide polymorphisms in the promoter region (-986G>A, -602G>A, -4A>G) and in exon 8 (+6424G>T) using real-time polymerase chain reaction.

RESULTS

The FCN2 -986A and -4G alleles were significantly associated with the occurrence of schistosomiasis (P = .0004 for -986G>A; P = .0001 for -4A>G). The heterozygous genotypes (P = .0006 for -986G>A; P = .0002 for -4A>G) were observed to be a risk factor for susceptibility to schistosomiasis, whereas the homozygous genotypes of major alleles (P = .0002 for -986G>A; P = .0001 for -4A>G) were observed to shield against schistosomiasis. The haplotype AGGG (P = .0002) was observed to be a risk factor for susceptibility to schistosomiasis compared with controls, and the haplotype GGAG (P = .04) was observed to confer protection compared with patients. Ficolin-2 serum level was significantly higher in controls (P < .005) and in controls with GGAG haplotypes (P < .0001).

CONCLUSIONS

Our findings demonstrate that FCN2 promoter variants (-986G>A and -4A>G) influence ficolin-2 serum levels and susceptibility to schistosomiasis.

Association of MICA gene polymorphisms with liver fibrosis in schistosomiasis patients in the Dongting Lake region

Major histocompatibility complex class I chain-related A (MICA) is a highly polymorphic gene located within the MHC class I region of the human genome. Expressed as a cell surface glycoprotein, MICA modulates immune surveillance by binding to its cognate receptor on natural killer cells, NKG2D, and its genetic polymorphisms have been recently associated with susceptibility to some infectious diseases. We determined whether MICA polymorphisms were associated with the high rate of Schistosoma parasitic worm infection or severity of disease outcome in the Dongting Lake region of Hunan Province, China. Polymerase chain reaction-sequence specific priming (PCR-SSP) and sequencing-based typing (SBT) were applied for high-resolution allele typing of schistosomiasis cases (N = 103, age range = 36.2-80.5 years, 64 males and 39 females) and healthy controls (N = 141, age range = 28.6-73.3 years, 73 males and 68 females). Fourteen MICA alleles and five short-tandem repeat (STR) alleles were identified among the two populations. Three (MICA*012:01/02, MICA*017 and MICA*027) showed a higher frequency in healthy controls than in schistosomiasis patients, but the difference was not significantly correlated with susceptibility to S. japonicum infection (Pc > 0.05). In contrast, higher MICA*A5 allele frequency was significantly correlated with advanced liver fibrosis (Pc < 0.05). Furthermore, the distribution profile of MICA alleles in this Hunan Han population was significantly different from those published for Korean, Thai, American-Caucasian, and Afro-American populations (P < 0.01), but similar to other Han populations within China (P > 0.05). This study provides the initial evidence that MICA genetic polymorphisms may underlie the severity of liver fibrosis occurring in schistosomiasis patients from the Dongting Lake region.

Study on differences in the pathology, T cell subsets and gene expression in susceptible and non-susceptible hosts infected with Schistosoma japonicum

More than 40 kinds of mammals in China are known to be naturally infected with Schistosoma japonicum (S. japonicum); Microtus fortis (M. fortis), a species of vole, is the only mammal in which the schistosomes cannot mature or cause significant pathogenic changes. In the current study, we compared the differences in pathology by Hematoxylin-eosin staining and in changes in the T cell subsets with flow cytometry as well as gene expression using genome oligonucleotide microarrays in the lung and liver, before challenge and 10 days post-infection with schistosomes in a S. japonicum-susceptible mouse model of infection, a non-susceptible rat model and the non-permissive host, M. fortis. The results demonstrated that S. japonicum promoted a more intensive immune response and more pathological lesions in M. fortis and rats than in mice. Hematoxylin-eosin staining revealed that the immune effector cells involved were mainly eosinophilic granulocytes supplemented with heterophilic granulocytes and macrophages. The analysis of splenic T cell subsets showed that CD4(+) T cell subsets and the CD4(+)/CD8(+) ratio were increased, while the CD8(+) T cell subsets decreased remarkably in rats; whereas the CD8(+) T cell subsets were increased, but the CD4(+)/CD8(+) ratio was decreased significantly in mice. The analysis of the pattern of gene expression suggested that some immune-associated genes and apoptosis-inducing genes up-regulated, while some development-associated genes were down-regulated in the infected M. fortis compared to the uninfected controls; the three different hosts have different response mechanisms to schistosome infection. The results of this study will be helpful for identifying the key molecules in the immune response to S. japonicum in M. fortis and for understanding more about the underlying mechanism of the response, as well as for elucidating the interaction between S. japonicum and its hosts.

AgNORs count and DNA ploidy in liver biopsies from patients with schistosomal liver cirrhosis and hepatocellular carcinoma

OBJECTIVES

Argyrophilic nucleolar organizer regions (AgNOR) proteins are a set of argyrophilic nucleolar proteins that accumulate in highly proliferating cells, whereas their expression is very low in nonproliferating cells. The present study aimed to investigate the potential of DNA flow cytometry (FCM) and AgNORs count in the assessment of cellular kinetics of liver cirrhosis and hepatocellular carcinoma.

DESIGN AND METHODS

Small-needle liver biopsies (217) were included and were taken from 84 patients with hepatocellular carcinoma (HCC) (one biopsy from tumor lesion and the other from residual nontumor) liver tissues. Only one biopsy was taken from 49 patients with liver cirrhosis. One part of biopsy was subjected to flow cytometry, and the other, to histopathology and AgNORs counting.

RESULTS

An aneuploidy was shown in 44.5% of liver cirrhosis and in 78.6% of tumor sites. Aneuploid HCC cases showed high AgNORs count compared with diploid cases (3.407+/-1.18 vs. 1.74+/-0.9). An extremely significant increase in AgNORs count in tumor lesion (P<0.001) was found compared with residual liver tissues, liver cirrhosis and normal liver (3.89+/-0.827, 1.49+/-0.52, 1.62+/-0.29, and 1.3+/-0.17, respectively). In liver cirrhosis, dysplasia showed a significant relationship with ploidy (P<0.001) and AgNORs count (P<0.05).

CONCLUSION

AgNORs count and DNA ploidy analysis of core biopsy specimens are useful in the assessment of cellular kinetics of liver cirrhosis and hepatocellular carcinoma.

[Dynamic changes in the expression of type VI collagen in mice with schistosomal liver fibrosis]

AIM

To clarify the dynamic changes in type VI procollagen mRNA expression and collagen content in mice with schistosomal liver fibrosis.

METHODS

Northern blot hybridization and immunohistochemical technique.

RESULTS

The expression of alpha 1(VI) procollagen mRNA measured by Northern blot hybridization in the liver of schistosome infected mice was elevated significantly at 8 wk post infection, peaked at 10 wk pi, slightly decreased at 12-16 wk pi, and sustained at high levels until 20 wk pi. Immunohistochemical assay revealed that the staining pattern of type VI collagen first appeared in the walls of central veins and liver sinusoids at 8 wk pi, then extended gradually to the egg granuloma and the portal tract, within and surrounding the egg granuloma to form dense reticular septum at the 12, 16 and 20 wk pi, respectively. The VI collagen content as indicated by the intensity of stain peaked at 16 wk pi.

CONCLUSION

Both the expression of alpha 1(VI) procollagen and the content of collagen VI were significantly increased in the liver of mice with early schistosomal fibrosis, suggesting that the type VI collagen detection might be of importance for evaluating the intensity of schistosomal liver fibrosis.

Nimbus (BgI): an active non-LTR retrotransposon of the Schistosoma mansoni snail host Biomphalaria glabrata

The freshwater snail Biomphalaria glabrata is closely associated with the transmission of human schistosomiasis. An ecologically sound method has been proposed to control schistosomiasis using genetically modified snails to displace endemic, susceptible ones. To assess the viability of this form of biological control, studies towards understanding the molecular makeup of the snail relative to the presence of endogenous mobile genetic elements are being undertaken since they can be exploited for genetic transformation studies. We previously cloned a 1.95kb BamHI fragment in B. glabrata (BGR2) with sequence similarity to the human long interspersed nuclear element (LINE or L1). A contiguous, full-length sequence corresponding to BGR2, hereafter-named nimbus (BgI), has been identified from a B. glabrata bacterial artificial chromosome (BAC) library. Sequence analysis of the 65,764bp BAC insert contained one full-length, complete nimbus (BgI) element (element I), two full-length elements (elements II and III) containing deletions and flanked by target site duplications and 10 truncated copies. The intact nimbus (BgI) contained two open-reading frames (ORFs 1 and 2) encoding the characteristic hallmark domains found in non-long terminal repeat retrotransposons belonging to the I-clade; a nucleic acid binding protein in ORF1 and an apurinic/apyrimidinic endonuclease, reverse transcriptase and RNase H in ORF2. Phylogenetic analysis revealed that nimbus (BgI) is closely related to Drosophila (I factor), mosquito Aedes aegypti (MosquI) and chordate ascidian Ciona intestinalis (CiI) retrotransposons. Nimbus (BgI) represents the first complete mobile element characterised from a mollusk that appears to be transcriptionally active and is widely distributed in snails of the neotropics and the Old World.

Genetic manipulation of schistosomes

In contrast to the situations with model organisms and parasitic protozoa, progress with gene manipulation with schistosomes has been delayed by impediments that include our inability to maintain the life cycle in vitro, absence of immortalized cell lines, large genome sizes, unavailability of drug resistance markers and other difficulties. However, in the past few years, tangible progress has been reported towards development of tools for gene manipulation and transgenesis of schistosomes, and there is reason to believe that the field is on the verge of transformation into an era where genetic manipulation is routine. Recent reports dealing with approaches and tools to manipulate the genome and gene expression in schistosomes are reviewed here.

Mendelian and complex genetics of susceptibility and resistance to parasitic infections

Uncovering the complex genetic basis of susceptibility and resistance to parasitic infectious diseases is an enormous challenge. It probably involves many different host genes, interacting with multiple parasite genetic and environmental factors. Several genes of interest have been identified by family and association studies in humans and by using mouse models, but more robust epidemiological studies and functional data are needed to authenticate these findings. With new technologies and statistical tools for whole-genome association analysis, the next few years are likely to see acceleration in the rate of gene discovery, which has the potential to greatly assist drug and vaccine development.

The interaction of Schistosoma haematobium and S. guineensis in Cameroon

Interactions between schistosomes are complex with some different species being able to mate and hybridize. The epidemiology of schistosomiasis in specific areas of South West Cameroon has evolved remarkably over 30 years as a result of hybridization between Schistosoma guineensis and S. haematobium. Morphological and biological data suggest that S. haematobium replaced S. guineensis in areas of Cameroon through introgressive hybridization. Data are reported on the use of single stranded conformational polymorphism (SSCP) analysis of the nuclear ribosomal second internal transcribed spacer (ITS2) of individual schistosomes from hybrid zones of Cameroon. The data show that since 1990 S. haematobium has completely replaced S. guineensis in Loum, with S. haematobium and the recombinants still present in 2000. This study illustrates the complexities of the dynamics between S. haematobium and S. guineensis in South West Cameroon.

Novel adenine adducts, N7-guanine-AFB1 adducts, and p53 mutations in patients with schistosomiasis and aflatoxin exposure

INTRODUCTION

The most frequent mutation in human hepatocellular carcinoma (HCC) in populations exposed to a high dietary intake of aflatoxin B1 (AFB1) is a mutation in codon 249 of the p53 gene. Schistosomiasis is known to cause p53 mutation. We hypothesized that the combination of schistosomiasis and aflatoxin B1 increases the incidence of p53 gene mutation.

METHODS

Liver tissue from 21 patients with schistosomiasis and 5 patients without schistosomiasis were analyzed for occurrence of mutations of the p53 gene and levels of N7-guanine-AFB1 adducts.

RESULTS

The presence of mutations in codon 249 of p53 gene was higher in patients infected with Schistosoma haematobium (S. haematobium) than in those infected with Schistosoma mansoni (S. mansoni) or a combination of both strains (p < 0.01), compared to control subjects. No mutations were detected in p53 gene in liver DNA from schistosomiasis-free patients. Significant amounts of N7-guanine-AFB1 adducts and novel adenine-adducts (p < 0.01) were detected in patients with schistosomiasis, mostly in patients infected with S. haematobium or a combination of both strains, compared to control subjects.

CONCLUSION

These data suggest that schistosomiasis and exposure to aflatoxin B1 act synergistically to increase the incidence of p53 gene mutation. The increase in p53 mutations may enhance progression of HCC at an early age in patients with schistosomiasis.

Implementation of Human Schistosomiasis Control: Challenges and Prospects

Schistosomiasis is a major disease of public health importance in humans occurring in over 70 countries of the tropics and sub-tropics. In this chapter, the history of the control of schistosomiasis is briefly discussed and current methods of control of schistosomiasis are reviewed; including mollusciciding, biological control of the intermediate snail hosts, the development of drugs to kill the adult worms, provision of clean water and health education, with a focus on the African situation. Since an effective vaccine against schistosomiasis is lacking, the emphasis today is placed on the drug praziquantel (PZQ). The marked reduction in the cost of PZQ together with the support of the Bill and Melinda Gates Foundation has enabled the drug to be used more widely in sub-Saharan Africa. Nevertheless, with the possibility of resistance to praziquantel emerging, the potential role of other drugs, such as artemether, in the control of schistosomiasis is examined. The World Health Organization (WHO) anticipates that at least 75% of all schoolchildren at risk of morbidity from schistosomiasis will be treated by 2010, with the aim of reversing morbidity. The importance of recent international initiatives such as the Schistosomiasis Control Initiative (SCI) working in Mali, Niger, Burkina Faso, Zambia, Tanzania and Uganda is recognised. There are benefits to integrating the control of schistosomiasis with other disease control programmes, such as gastrointestinal helminths and/or lymphatic filariasis (LF), since this markedly reduces the cost of delivery of the treatment. Countries that are situated on the perimeter of the distribution of schistosomiasis have either achieved or have made progress towards the elimination of the disease. For control programmes to be successful in areas such as sub-Saharan Africa, it is absolutely essential that these programmes are sustainable. Thus, it will be vital for Ministries of Health and Education to budget for the control of diseases of poverty in addition to school health, and to utilise funds from a range of sources, such as, government funds, pooled donor contributions, or bilateral and international agencies.

High-Throughput GoMiner, an 'industrial-strength' integrative gene ontology tool for interpretation of multiple-microarray experiments, with application to studies of Common Variable Immune Deficiency (CVID)

BACKGROUND

We previously developed GoMiner, an application that organizes lists of 'interesting' genes (for example, under-and overexpressed genes from a microarray experiment) for biological interpretation in the context of the Gene Ontology. The original version of GoMiner was oriented toward visualization and interpretation of the results from a single microarray (or other high-throughput experimental platform), using a graphical user interface. Although that version can be used to examine the results from a number of microarrays one at a time, that is a rather tedious task, and original GoMiner includes no apparatus for obtaining a global picture of results from an experiment that consists of multiple microarrays. We wanted to provide a computational resource that automates the analysis of multiple microarrays and then integrates the results across all of them in useful exportable output files and visualizations.

RESULTS

We now introduce a new tool, High-Throughput GoMiner, that has those capabilities and a number of others: It (i) efficiently performs the computationally-intensive task of automated batch processing of an arbitrary number of microarrays, (ii) produces a human-or computer-readable report that rank-orders the multiple microarray results according to the number of significant GO categories, (iii) integrates the multiple microarray results by providing organized, global clustered image map visualizations of the relationships of significant GO categories, (iv) provides a fast form of 'false discovery rate' multiple comparisons calculation, and (v) provides annotations and visualizations for relating transcription factor binding sites to genes and GO categories.

CONCLUSION

High-Throughput GoMiner achieves the desired goal of providing a computational resource that automates the analysis of multiple microarrays and integrates results across all of the microarrays. For illustration, we show an application of this new tool to the interpretation of altered gene expression patterns in Common Variable Immune Deficiency (CVID). High-Throughput GoMiner will be useful in a wide range of applications, including the study of time-courses, evaluation of multiple drug treatments, comparison of multiple gene knock-outs or knock-downs, and screening of large numbers of chemical derivatives generated from a promising lead compound.

Enhanced egg-induced immunopathology correlates with high IFN-gamma in murine schistosomiasis: identification of two epistatic genetic intervals

The genetic basis of dissimilar immunopathology development among mouse strains infected with Schistosoma mansoni is not known. We performed a multipoint parametric linkage analysis on a cohort of F(2) mice, offspring of brother-sister mating between (high pathology CBA x low pathology BL/6)F(1) mice, to examine whether the observed differences in the type of immune response or the extent of hepatic immunopathology are linked to any particular genomic intervals. The F(2) mice exhibited cytokine responses and immunopathologies that revealed a statistically significant correlation between prominent egg Ag-stimulated IFN-gamma production by mesenteric lymph node cells and hepatic egg granuloma size. Increased IFN-gamma production showed suggestive linkage to a dominant CBA locus on chromosome 1 and a recessive CBA locus on chromosome 5; significantly, there was an epistatic interaction between the two IFN-gamma loci. An additional locus with suggestive linkage to granuloma formation and a CBA-recessive mode of inheritance was mapped to centromeric chromosome 13. Our analysis identified the first three genetic regions that appear to influence the immunopathology in murine schistosomiasis; however, further congenic dissection studies will furnish a more precise understanding of the genetic control of this disease.

The immunobiology of Th1 polarization in high-pathology schistosomiasis

Schistosomiasis is a serious global helminthic disease, in which the main immunopathology consists of a granulomatous and fibrosing reaction against tissue-trapped parasite eggs. The severity of this inflammatory process, the product of a CD4(+) T-cell-mediated immune response against parasite egg antigens, is, however, markedly uneven, both in human patients and among mouse strains in an experimental model. Severe schistosomiasis is associated with persistently elevated pro-inflammatory T-helper-1 (Th1)-type cytokines, whereas milder pathology is present when Th2 cytokines dominate. This scenario is supported by the pronounced pathology resulting from the obliteration of pathways that facilitate Th2 differentiation and by the development of more intense lesions in mouse strains that fail to downregulate the Th1 response. Genetically prone high-pathology mice have a higher proportion of CD4(+) T cells in lymph nodes and granulomas, in which the Th1 phenotype is driven by interleukin-12; they also develop a dominant repertoire against peptide 234-246 of the major Sm-p40 egg antigen, utilizing a strikingly restricted T-cell receptor structure that involves Valpha11.3beta8. In turn, low-pathology mice exhibit enhanced CD4(+) T-cell apoptosis, which contributes to limit pathology. The definition of distinctive immune profiles associated with polar forms of schistosomiasis opens opportunities for targeted immuno-intervention in individuals suffering from or at risk of severe disease.

Interleukin-13 in the skin and interferon-gamma in the liver are key players in immune protection in human schistosomiasis

Immunity against schistosomes includes anti-infection immunity, which is mainly active against invading larvae in the skin, and anti-disease immunity, which controls abnormal fibrosis in tissues invaded by schistosome eggs. Anti-infection immunity is T-helper 2 (Th2) cell-dependent and is controlled by a major genetic locus that is located near the Th2 cytokine locus on chromosome 5q31-q33. Mutations in the gene encoding interleukin (IL)-13 that decrease or increase IL-13 production account, at least in part, for that genetic control. In contrast, protection against hepatic fibrosis is dependent on interferon (IFN)-gamma and is controlled by a major genetic locus that is located on 6q23, near the gene encoding the IFN-gamma receptor beta chain. Mutations that modulate IFN-gamma gene transcription are associated with different susceptibility to disease. These data indicate that IL-13 in the skin and IFN-gamma in the liver are key players in protective immunity against schistosomes. These roles relate to the high anti-fibrogenic activities of IFN-gamma and to the unique ability of IL-13 in Th2 priming in the skin and in the mobilization of eosinophils in tissues. The coexistence of strong IFN-gamma and IL-13-mediated immune responses in the same subject may involve the compartmentalization of the anti-schistosome immune response between the skin and the liver.

Hepatosplenic schistosomiasis: a review

BACKGROUND

Schistosomiasis is a granulomatous disease that is caused by infection with schistosomes. It is a major health threat in tropical and subtropical countries. Due to increased movement, all residents of the universe are at risk of contracting this infection. The infection goes through several stages, but the most life-threatening form and leading cause of mortality is hepatosplenic schistosomiasis (HSS). It is a chronic complication, which develops as a consequence of inflammatory response. This complication has not been adequately addressed or attended the and as a consequence most of patients presenting with this complication in our settings die.

OBJECTIVES

To review literature on hepatosplenic schistosomiasis, to give the state-of-the-art management of HSS, to give our own experience on management of this complication and hence impart knowledge to medical personnel on HSS.

DATA SOURCE

Literature is from Medline database and experience from gastroenterology clinics. Our own experience has been blended on top.

STUDY SELECTION AND DATA EXTRACTION

We have selected material, which have been verified and can be applicable in resource poor-countries, where this problem is a major health threat.

DATA SYNTHESIS

Based on published studies and meta-analyses and our own experience we have been able to draw conclusions on the current understanding of the subject.

CONCLUSION

Hepatosplenic schistosomiasis is a deadly complication and occurs mainly in poor countries. Regular reviews and updates of our knowledge is important to enable stakeholders of health sector understand the problem and develop strategies on its management.

Genome size estimates for two important freshwater molluscs, the zebra mussel (Dreissena polymorpha) and the schistosomiasis vector snail (Biomphalaria glabrata)

The haploid genome sizes of two important molluscs were assessed by Feulgen image analysis densitometry. The genome size of the zebra mussel (Dreissena polymorpha), a prolific invader of North American lakes, was estimated to be 1C = 1.70 ± 0.03 pg, and that of the freshwater snail Biomphalaria glabrata, the predominant intermediate vector of the human parasite Schistosoma mansoni, was estimated at 0.95 ± 0.01 pg. These estimates will be important in future efforts in molluscan genomics, which at present lags far behind work being carried out with vertebrate and arthropod models. B. glabrata in particular, which has one of the smallest known gastropod genomes, is recommended as a highly suitable target for future genome sequencing.Key words: densitometry, DNA content, DNA sequencing, Feulgen, image analysis, Great Lakes, invading species, molluscs, Schistosoma mansoni.

Chromosomal aberrations in benign and malignant bilharzia-associated bladder lesions analyzed by comparative genomic hybridization

BACKGROUND

Bilharzia-associated bladder cancer (BAC) is a major health problem in countries where urinary schistosomiasis is endemic. Characterization of the genetic alterations in this cancer might enhance our understanding of the pathogenic mechanisms of the disease but, in contrast to nonbilharzia bladder cancer, BAC has rarely been the object of such scrutiny. In the present study, we aimed to characterize chromosomal imbalances in benign and malignant post-bilharzial lesions, and to determine whether their unique etiology yields a distinct cytogenetic profile as compared to chemically induced bladder tumors.

METHODS

DNAs from 20 archival paraffin-embedded post-bilharzial bladder lesions (6 benign and 14 malignant) obtained from Sudanese patients (12 males and 8 females) with a history of urinary bilharziasis were investigated for chromosomal imbalances using comparative genomic hybridization (CGH). Subsequent FISH analysis with pericentromeric probes was performed on paraffin sections of the same cases to confirm the CGH results.

RESULTS

Seven of the 20 lesions (6 carcinomas and one granuloma) showed chromosomal imbalances varying from 1 to 6 changes. The most common chromosomal imbalances detected were losses of 1p21-31, 8p21-pter, and 9p and gain of 19p material, seen in three cases each, including the benign lesion.

CONCLUSION

Most of the detected imbalances have been repeatedly reported in non-bilharzial bladder carcinomas, suggesting that the cytogenetic profiles of chemical- and bilharzia-induced carcinomas are largely similar. However, loss of 9p seems to be more ubiquitous in BAC than in bladder cancer in industrialized countries.

Evolutionary relationships between trematodes and snails emphasizing schistosomes and paragonimids

Snails and digeneans have been associated for at least 200 million years. Their inter-relationships over such a time-span must have been complex and varied. Few studies have attempted to explore these relationships in the light of knowledge of the phylogeny of both host and parasite groups. Here we focus on two important families of digeneans, the Schistosomatidae and the Paragonimidae, for which molecular phylogenies are available. We investigate the types of evolutionary relationships between host and parasite, operating at different phylogenetic depths, that might explain current host specificity and distributions of both associates. Both families of parasites utilise a number of highly diverged gastropod families, indicating that host extensions have featured in their histories. However, schistosomatids and paragonimids show different patterns of association with their snail hosts. As befits the apparently more ancient group, schistosomatids utilise snails from across a wide phylogenetic range within the Gastropoda. The genus Schistosoma itself has experienced one long-range host switch between pulmonates and caenogastropods. By contrast, paragonimids are restricted to two superfamilies of caenogastropods. Despite these differences, modern schistosomatid species appear to be more host specific than are paragonimids and host additions, at the level of host family, are far less common among species of schistosomatids than among paragonimids. Some species of Paragonimus exhibit remarkably low levels of host specificity, with different populations utilising snails of different families. Existing knowledge relating to the phenomenon will be presented in the context of phylogenies of schistosomatids, paragonimids, and their snail hosts. Discussion focuses on the usefulness of current theories of snail-digenean coevolution for interpreting these findings. In the past, much emphasis has been placed on the idea that digeneans engage in a one-to-one arms race with their snail host. We consider that phylogenetic tracking rather than an arms-race relationship might be a common alternative. Not being bound by the restrictions imposed by an arms race, some digeneans might be able to extend to new host species more easily than the literature suggests. Switches into related host taxa are most likely. However, ecologically equivalent but unrelated gastropod hosts may also be exploited. Given the right ecological setting, digeneans are able to switch across considerable phylogenetic distances. Examples from the Paragonimidae and Schistosomatidae are given.

[Schistosoma reflexum in a female bovine fetus with synaptonemal complex abnormalities]

In this study we present mitotic- and meiotic investigations in an anatomical abnormal bovine fetus. The abnormality could be classified as "schistosoma reflexum", which was never described in fetuses in the literature. In the mitotical chromosome preparations from fibroblast cultures the examined fetus showed no chromosomal difference in comparison to the standard synaptonemal complexes (SC) which were prepared from the fetus at the age of 92 days post coitum. In the SCs from the abnormal fetus 43.75% of the investigated cells showed abnormalities such as "loop," "nonhomologue pairing" and "multivalency" in the pairing behavior of the chromosomes. In comparison, less than 5% of the cells in normal embryos showed such abnormalities.

[Selective pressure in host-parasite systems]

Selective pressures in host-parasite systems are the result of a continuous conflict between the divergent interests of each partner, on the long run. Whereas the fitness (lifetime reproductive success) of parasites is usually increased by a higher frequency of encounters with susceptible hosts and a better survival rate after infection, the fitness of hosts is increased by opposite processes, avoidance of encounters with infective stages and destruction of the parasites. These selective processes, often referred to as coevolution or arms races are in agreement with the Red Queen hypothesis of Van Valen, which assumes indefinite adaptive changes in both partners, in order to set up counter-measures against the weapons of "the other". Arms races in host-parasite systems thus suggest a gradualistic evolution, but this does not contradict the present day ideas on the tempo changes in the course of evolution (punctuated equilibria). Numerous factors, either genetic (evolutionary lag...), environmental (nutritional status...) or cultural (prevention, vaccination, therapy...) influence the severity of infections at an individual scale. The "terrain", which is a component of the individual phenotype, is thus at the cross-roads of genes, environment and culture. Humans must count more on their intelligence than on natural selection to prevent and cure infectious and parasitic diseases.

Sex chromosome differences among the three races (alpha, beta, gamma) of the snail intermediate host of Schistosoma mekongi, Neotricula aperta

Chromosome analyses were performed on three races (alpha, beta, gamma) of Neotricula aperta which were previously reported to show variation in the chromosome number and pairing in meiosis. We used an air-drying method, which was more reliable for chromosome preparations from fresh animal tissues than a squash method. Each of the races had the same number of chromosomes, 2n=33 for males, and 2n=34 for females. The sex determination system was XO type (male: 32+X, female: 32+XX). The sex chromosome of each race was distinct in its morphology, but not in its length. Karyotyping revealed that the X-chromosome of the alpha race was metacentric (M), whereas it was acrocentric (A) in the beta and the gamma races. An association between the X-chromosome and a small autosome in meiosis suggested that a neo-Y chromosome probably lies in the terminal region of the small autosome.

Deletion of p16 and p15 genes In schistosomiasis-associated bladder cancer (SABC)

Alterations of p16 and p15 genes have been reported in cancer cell lines and in certain malignant neoplasm. These genes are designated as candidate tumor suppressor genes because they encode proteins that function as negative cell cycle regulators at G(1)-S checkpoint. One hundred and sixty eight tumor tissue, 20 schistosomal tissue, and 50 normal tissue samples were examined. The status of p16 and p15 genes in these tissues was determined by the polymerase chain reaction and by sequencing the DNA fragments produced during PCR. In addition, the expression of p16 and p15 proteins was examined by Western blot analysis. p16 and p15 genes were detected in all normal and schistosomal tissues. Deletion of both p16 and p15 genes was observed in 72 and 36 bladder tumors, respectively. Twenty eight of the 72 cases that exhibited p16 deletions also displayed deletions of p15. Only eight cases showed loss of the p15 gene while retaining p16 gene, and p16 deletion with apparently intact p15 gene was identified in 44 cases. The present analysis also reveals that deletion in the two genes are associated with low-stage, low grade bladder cancer, schistosomiasis-associated bladder cancer (SABC) and squamous cell carcinoma type (SCC). No point mutations were identified in either gene. The expression of p16 and p15 proteins was undetectable in 75 and 38 bladder tumors, respectively, by Western blot analysis. Alteration of the p16 and p15 genes appears to be an early event in bladder cancer which occurs more frequently in SABC and SCC, and may play an important role in the development of schistosomal bladder cancer.

IL-4 regulates VIP receptor subtype 2 mRNA (VPAC2) expression in T cells in murine schistosomiasis

In murine schistosomiasis, granuloma T cells express VPAC2 mRNA, whereas there is none in splenocytes. This suggests that T cell VPAC2 mRNA is inducible. To address this issue, splenocytes from schistosome-infected mice were incubated with anti-CD3 to induce VPAC2 mRNA, which only appeared when cell cultures also contained anti-IL-4 mAb. Granuloma cells expressed VPAC2 mRNA. This natural expression decreased substantially when cells were cultured 3 days in vitro. However, granuloma cells cultured with anti-IL-4 mAb strongly expressed VPAC2 mRNA. IL-4 KO mice were examined to further address the importance of IL-4 in VPAC2 regulation. Splenocytes and dispersed granuloma cells from IL-4 KO animals had substantially more VPAC2 mRNA than those in wild-type controls. VPAC2 mRNA content decreased when cells were cultured with rIL-4. VPAC2 mRNA localized to CD4+ T cells. Th1 cell lines expressed VPAC2 mRNA much stronger than Th2 cells. Anti-IL-4 mAb increased VPAC2 mRNA expression in Th2 cells cultured in vitro. However, rIL-4 could not suppress VPAC2 mRNA expression in Th1 cells. Thus, VPAC2 is an inducible CD4+ T cell receptor, and IL-4 down-modulates VPAC2 mRNA expression in Th2 cells.

Loss of Y chromosome in bilharzial bladder cancer

Bilharzial bladder cancer is the most common malignant neoplasm in Egypt, also occurring with a high incidence in other regions of the Middle East and East Africa. In a previous study, using centromere probes specific for chromosomes 3, 4, 7-11, 16, and 17, we demonstrated that monosomy of chromosome 9 (48.4%), and numerical aberrations of chromosome 17 (19.4%) were the most common observed imbalances. The present study extends the establishment of the baseline cytogenetic profile of this type of malignancy. Interphase cytogenetics by fluorescence in situ hybridization with the use of a panel of centromere-associated DNA probes for chromosomes 1, 2, 5, 6, 12, 13/21, 14, 15, 18, 19, 20, X, and Y was performed on paraffin-embedded bladder specimens from 25 Egyptian patients affected with bilharzial bladder cancer. No numerical aberrations were detected in the 25 cases for chromosomes 1, 2, 5, 6, 12, 13/21, 14, 15, 18, 19, 20, and X. However, loss of chromosome Y was observed in 7 of the 17 male cases studied (41.2%). No significant correlation was observed between loss of the Y chromosome and any of the different clinicopathologic characteristics of these cases. These data suggest that loss of the Y chromosome is the second frequent event that can occur in bilharzial bladder cancer. A molecular genetic model of bilharzial bladder cancer is evolving.

[Genetic predisposition to bilharziasis in humans: research methods and application to the study of Schistosoma mansoni infection]

The development of genetic epidemiology methods using recent human genetic mapping information together with the growing availability of candidate genes has led to major advances in the identification of host genes in human schistosomiasis. Two phenotypes have been studied so far in the infection by Schistosoma mansoni: infection levels by the parasite as measured by the faecal egg counts, and the severe hepatic fibrosis caused by S. mansoni assessed by ultrasound examination. The first study was performed on Brazilian pedigrees and provided strong evidence for a major gene controlling infection levels by S. mansoni denoted as SM1 which was mapped to chromosome 5q31-q33. This region contains several candidate genes involved in the regulation of the Th1/Th2 response, and the direct role of polymorphisms located within these genes is under investigation. The second study conducted in Sudan also showed the presence of a major gene influencing the development of severe hepatic fibrosis due to S. mansoni infection denoted as SM2. This gene is not located in the 5q31-q33 region, but maps to chromosome 6q22-q23 and is closely linked to the IFN-gamma R1 gene encoding the receptor of the strongly anti-fibrogenic cytokine Interferon-gamma. These findings indicate that two distinct genetic loci control human predisposition to schistosomiasis, SM1 located in the 5q31-q33 region which is likely to play a role in the Th1/Th2 differentiation, and SM2 in 6q22-q23 influencing disease progression with a possible involvement in the regulation of IFN-gamma.

Relationship between schistosomiasis and bladder cancer

Carcinoma of the urinary bladder is the most common malignancy in the Middle East and parts of Africa where schistosomiasis is a widespread problem. Much evidence supports the association between schistosomiasis and bladder cancer: this includes the geographical correlation between the two conditions, the distinctive patterns of gender and age at diagnosis, the clinicopathological identity of schistosome-associated bladder cancer, and extensive evidence in experimentally infected animals. Multiple factors have been suggested as causative agents in schistosome-associated bladder carcinogenesis. Of these, N-nitroso compounds appear to be of particular importance since they were found at high levels in the urine of patients with schistosomiasis-associated bladder cancer. Various strains of bacteria that can mediate nitrosation reactions leading to the formation of N-nitrosamines have been identified in the urine of subjects with schistosomiasis at higher intensities of infection than in normal subjects. In experimental schistosomiasis, the activities of carcinogen-metabolizing enzymes are increased soon after infection but are reduced again during the later chronic stages of the disease. Not only could this prolong the period of exposure to activated N-nitrosamines, but also inflammatory cells, stimulated as a result of the infection, may induce the endogenous synthesis of N-nitrosamines as well as generating oxygen radicals. Higher than normal levels of host cell DNA damage are therefore anticipated, and they have indeed been observed in the case of alkylation damage, together with an inefficiency in the capacity of relevant enzymes to repair this damaged DNA. In experimental schistosomiasis, it was also found that endogenous levels of host cell DNA damage were related to the intensity of infection. All of these factors could contribute to an increased risk of bladder cancer in patients with schistosomiasis, and in particular, the gene changes observed may have potential for use as biomarkers in the early detection of bladder cancer that may assist in alleviating the problem.

Full results of the genome-wide scan which localises a locus controlling the intensity of infection by Schistosoma mansoni on chromosome 5q31-q33

Three hundred million individuals are at risk of infection by schistosomes, and thousands die each year of severe hepatic disease. Previous studies have shown that the intensity of infection by Schistosoma mansoni in a Brazilian population is controlled by a major gene, denoted as SM1. We report here the full results of a genome-wide search that was performed on this population to localise SM1. Two hundred and forty-six microsatellites were used for the primary map, and only one region in 5q31-q33 provided significant evidence of linkage. SM1 was subsequently mapped to this region, which contains several genes encoding cytokines or cytokine receptors which are involved in protection against schistosomes. Three additional regions, 1p22.2, 7q36 and 21q22-22-qter, yielded promising, although not significant, lod-score values. These regions contain candidate genes encoding cytokines or molecules relevant to anti-schistosome immunity.

Absence of linkage between MHC and a gene involved in susceptibility to human schistosomiasis

Six hundred million people are at risk of infection by Schistosoma mansoni. MHC haplotypes have been reported to segregate with susceptibility to schistosomiasis in murine models. In humans, a major gene related to susceptibility/resistance to infection by S. mansoni (SM1) and displaying the mean fecal egg count as phenotype was detected by segregation analysis. This gene displayed a codominant mode of inheritance with an estimated frequency of 0.20-0.25 for the deleterious allele and accounted for more than 50% of the variance of infection levels. To determine if the SM1 gene segregates with the human MHC chromosomal region, we performed a linkage study by the lod score method. We typed for HLA-A, B, C, DR and DQ antigens in 11 informative families from an endemic area for schistosomiasis in Bahia, Brazil, by the microlymphocytotoxicity technique. HLA-DR typing by the polymerase chain reaction with sequence-specific primers (PCR-SSP) and HLA-DQ were confirmed by PCR-sequence-specific oligonucleotide probes (PCR-SSOP). The lod scores for the different theta values obtained clearly indicate that there is no physical linkage between HLA and SM1 genes. Thus, susceptibility or resistance to schistosomiasis, as defined by mean fecal egg count, is not primarily dependent on the host's HLA profile. However, if the HLA molecule plays an important role in specific immune responses to S. mansoni, this may involve the development of the different clinical aspects of the disease such as granuloma formation and development of hepatosplenomegaly.

Analysis of granuloma formation in double cytokine-deficient mice reveals a central role for IL-10 in polarizing both T helper cell 1- and T helper cell 2-type cytokine responses in vivo

In response to i.v.-injected eggs of Schistosoma mansoni, normal mice develop a dominant type 2 response, whereas IL-10-deficient animals generate a mixed type 1/type 2 cytokine profile and show reduced pulmonary granuloma formation. IL-4-deficient mice, while displaying diminished type 2 responses and granulomatous inflammation, also do not fully default to a type 1 cytokine profile. Strikingly, mice doubly deficient in IL-4 and IL-10 are completely defective in pulmonary granuloma formation and develop a highly polarized type 1 cytokine pattern. In analogous fashion, mice deficient in both IL-12 and IL-10 generate highly exacerbated type 2 cytokine responses, whereas in wild-type animals, IL-12 depletion minimally effects egg-induced cytokine production. Together, these results argue first that IL-10 is an important endogenous down-regulator of type 2 as well as type 1 cytokine synthesis, and second, that its induction is critical for type 2 response polarization in vivo.

Alterations affecting the p53 control pathway in bilharzial-related bladder cancer

Bilharzial-related bladder carcinoma (BBC) is the most common malignant neoplasm in Egypt, also occurring with a high incidence in other regions of the Middle East and East Africa. The clinical and pathological features of BBC are different than those described for the conventional transitional cell carcinoma of the bladder, including the high incidence of squamous cell carcinoma reported in BBC and the fact that over 90% of BBC cases at presentation are advanced-stage tumors (P3 and P4). This study was conducted to better define the phenotypic alterations associated with BBC affecting the p53 cell cycle control pathway, including altered patterns of expression of downstream effector proteins such as mdm2 and p21/WAF1. A well-characterized cohort of 125 patients affected with bilharzial-related bladder tumors was studied. Tumors were classified as squamous carcinomas (n = 68), transitional cell carcinomas (n = 55), or adenocarcinomas (n = 2). The products encoded by TP53, mdm2, and p21/WAF1 genes were analyzed by immunohistochemistry. Furthermore, the patterns of expression of these molecules were correlated with the Ki67 proliferative index. In addition, the microanatomical distribution of programmed cell death was assessed in a subset of tumors, using the so-called terminal deoxynucleotidyl transferase-mediated nick end labeling method. p53 nuclear overexpression was identified in 25 (20%) of 125 cases. Nuclear overexpression of mdm2 was detected in 74 (59.2%) of 125 cases. There was a statistically significant association between coexpression of both p53 and mdm2 and detection of lymph node metastases (P = 0.04). p21/WAF1 expression was detected in 87 (72%) of 121 evaluable cases. A high Ki67 proliferative index was observed in 99 (86%) of 115 evaluable cases. There was a statistically significant association between high Ki67 proliferative index and mdm2-positive phenotype (P = 0.005) and deep muscle invasion (P3b; P = 0.026) as well as lymph node metastases (P = 0.039). Apoptosis was observed in terminally differentiated tumor cells identified in the superficial layers of well-differentiated squamous carcinoma or exfoliating cells in transitional lesions. However, only rare apoptotic tumor cells were found in basal or suprabasal layers as well as in the invasive elements of the neoplasms studied. These results suggest that the frequency of p53 nuclear overexpression in BBC is lower than that reported for conventional transitional cell carcinoma. Nevertheless, tumors with p53 alterations have a greater propensity to progress. The prominent number of cases displaying an mdm2-positive phenotype suggests that this may be an early incident in BBC and should be regarded as a potential oncogenic phenomenon. This is supported by the significant correlation between high Ki67 proliferative index and mdm2 overexpression. The association of an aggressive clinical course with the coexpression of both p53 and mdm2 products might be viewed as a cooperative effect that develops in tumor progression.

Involvement of inflammatory reactions and elevated cell proliferation in the development of bladder cancer in schistosomiasis patients

Schistosoma haematobium infection is strongly associated with urinary bladder cancer. Although numerous explanations have been proposed for this association, the nature of this relationship remains unresolved. This paper explores the hypothesis that inflammation and elevated cell proliferation play a major role in the development of bladder cancer in infected patients, possibly by increasing the level of genetic instability in the urothelium. The paper details in vivo and in vitro studies being done in our laboratories to test this hypothesis. These studies include population studies in which chromosomal breakage in the bladder of infected individuals is assayed using the micronucleus (MN) test on exfoliated urothelial cells. The approach also includes parallel studies in Vancouver with patients with long-term catheter drainage, a population with many similarities to schistosomiasis patients. In the in vitro studies we are co-incubating bladder cells with activated neutrophils or experimental conditions simulating inflammation. These studies show that inflammatory cells when activated can induce micronuclei in bladder cells and that this response is associated with loci on chromosome 11, a chromosome commonly altered during bladder carcinogenesis. A final approach being used is to assay chromosomal change (MN frequencies and numerical chromosome alterations) and level of proliferation (expression of proliferating cell nuclear antigen) in archival biopsies from schistosomiasis patients. Preliminary results show that a dysregulation of cell proliferation is occurring during cystitis in these patients. The extent to which this alteration affects the level of chromosomal breakage is yet to be determined.

The molecular epidemiology of parasites

The explosion of new techniques, made available by the rapid advance in molecular biology, has provided a battery of novel approaches and technology which can be applied to more practical issues such as the epidemiology of parasites. In this review, we discuss the ways in which this new field of molecular epidemiology has contributed to and corroborated our existing knowledge of parasite epidemiology. Similar epidemiological questions can be asked about many different types of parasites and, using detailed examples such as the African trypanosomes and the Leishmania parasites, we discuss the techniques and the methodologies that have been or could be employed to solve many of these epidemiological problems.

Further studies on genetic variation of hepatosplenic disease and modulation in murine schistosomiasis mansoni

The influence of genetic factors on the modulation of hepatosplenomegaly, portal venous pressure and granuloma size in chronic murine schistosomiasis mansoni was studied. Experiments with congenic mice confirmed previous observations that after 8 weeks of infection these disease manifestations are influenced by non-H-2 genes. During chronic infection (20 weeks compared to 8 weeks of infection), hepatosplenomegaly was minimally altered. Portal venous pressure was found to increase in 129/J and BALB/cJ mice, did not change in C57BL/6J and DBA/2J and decreased in CBA/CaJ mice. Simultaneous measurements of granuloma size delineated two groups: decrease of greater than 40%--C57BL/6J, DBA/2J and CBA/CaJ strains and decrease of less than or equal to 20%--129/J, BALB/cJ and C3H/HeJ mice. There was no consistent correlation between the magnitude or direction of alterations in portal pressure and granuloma size among the various strains studied. Furthermore, these alterations were independent of changes in parasite burden (adult worms or hepatic eggs). This amelioration of disease (modulation) was found to be influenced by a small number of non-H-2 genes.