Analysis of the 5q31 33 locus shows an association between single nucleotide polymorphism variants in the IL-5 gene and symptomatic infection with the human blood fluke, Schistosoma japonicum

Frequency distribution of cytokine and associated transcription factor single nucleotide polymorphisms in Zimbabweans: Impact on schistosome infection and cytokine levels

Cytokines mediate T-helper (TH) responses that are crucial for determining the course of infection and disease. The expression of cytokines is regulated by transcription factors (TFs). Here we present the frequencies of single nucleotide polymorphisms (SNPs) in cytokine and TF genes in a Zimbabwean population, and further relate SNPs to susceptibility to schistosomiasis and cytokine levels. Individuals (N = 850) were genotyped for SNPs across the cytokines IL4, IL10, IL13, IL33, and IFNG, and their TFs STAT4, STAT5A/B, STAT6, GATA3, FOXP3, and TBX21 to determine allele frequencies. Circulatory levels of systemic and parasite-specific IL-4, IL-5, IL-10, IL-13, and IFNγ were quantified via enzyme-linked immunosorbent assay. Schistosoma haematobium infection was determined by enumerating parasite eggs excreted in urine by microscopy. SNP allele frequencies were related to infection status by case-control analysis and logistic regression, and egg burdens and systemic and parasite-specific cytokine levels by analysis of variance and linear regression. Novel findings were i) IL4 rs2070874*T’s association with protection from schistosomiasis, as carriage of ≥1 allele gave an odds ratio of infection of 0.597 (95% CIs, 0.421–0.848, p = 0.0021) and IFNG rs2069727*G’s association with susceptibility to schistosomiasis as carriage of ≥1 allele gave an odds ratio of infection of 1.692 (1.229–2.33, p = 0.0013). Neither IL4 rs2070874*T nor IFNG rs2069727*G were significantly associated with cytokine levels. This study found TH2-upregulating SNPs were more frequent among the Zimbabwean sample compared to African and European populations, highlighting the value of immunogenetic studies of African populations in the context of infectious diseases and other conditions, including allergic and atopic disease. In addition, the identification of novel infection-associated alleles in both TH1- and TH2-associated genes highlights the role of both in regulating and controlling responses to Schistosoma.

Genome-Wide Association Study Identifies New Risk Loci for Progression of Schistosomiasis Among the Chinese Population

Schistosoma japonicum infections, which lead to local inflammatory responses to schistosome eggs trapped in host tissues, can result in long-term, severe complications. The development of schistosomiasis may result from a complex interaction between the pathogenic, environmental, and host genetic components. Notably, the genetic factors that influence the development of schistosomiasis complications are poorly understood. Here we performed a genome-wide association study on multiple schistosomiasis-related phenotypes of 637 unrelated schistosomiasis patients in the Chinese population. Among three indicators of liver damage, we identified two novel, genome-wide significant single-nucleotide polymorphisms (SNPs) rs34486793 (P = 1.415 × 10^-8) and rs2008259 (P = 6.78 × 10^-8) at locus 14q32.2 as well as a gene, PMEPA1, at 20q13.31 (index rs62205791, P = 6.52 × 10^-7). These were significantly associated with serum levels of hyaluronic acid (HA). In addition, RASIP1 and MAMSTR at 19q13.33 (index rs62132778, P = 1.72 × 10^-7) were significantly associated with serum levels of aspartate aminotransferase (AST), and TPM1 at 15q22.2 (index rs12442303, P = 4.39 × 10^-7) was significantly associated with serum levels of albumin. In schistosomiasis clinical signs, ITIH4 at 3p21.1 (index rs2239548) was associated with portal vein diameter (PVD) class, an indicator of portal hypertension, and OGDHL at 10q11.23 (index rs1258172) was related to ascites grade. We also detected an increased expression of these six genes in livers of mice with severe schistosomiasis. Summary data-based Mendelian randomization analyses indicated that ITIH4, PMEPA1 and MAMSTR were pleiotropically associated with PVD class, HA and AST, respectively.

Associations of IL13 gene polymorphisms and immune factors with Schistosoma haematobium infection in schoolchildren in four schistosomiasis-endemic communities in Ghana

BACKGROUND

Schistosomiasis remains a major public health issue with over 90% of the prevalence rates recorded in Sub-Saharan Africa. In this study, the relationships between different interleukin gene polymorphisms (IL-13-591A/G, IL-13-1055C/T, IL-13-1258A/G) and Schistosoma haematobium infection levels were evaluated; as well as the host plasma antibodies and cytokine profiles associated with schistosomiasis infection.

METHODOLOGY

A total of 469 school children aged 6 to 19 years from four schistosomiasis-endemic communities in Ghana were involved. Single urine and stool samples were obtained from each pupil, processed via sedimentation and Kato-Katz, and examined via microscopy for Schistosoma and soil-transmitted helminth (STH) eggs. Next, venous blood samples were drawn from 350 healthy pupils, and used to measure antibody and plasma cytokine levels by ELISA. Single nucleotide polymorphisms in the IL-13 gene were genotyped on 71 selected blood samples using the Mass Array technique.

PRINCIPAL FINDINGS AND CONCLUSION

The overall prevalence of urinary schistosomiasis was 21.11%. Community-level prevalences were 17.12%, 32.11%, 20.80%, and 15.32% for Asempaneye, Barikumah, Eyan Akotoguah, and Apewosika respectively. Generally, higher S. haematobium infection prevalence and intensity were recorded for participants with genotypes bearing the IL13-1055C allele, the IL13-591A, and the IL13-1258A alleles. Also, higher S. haematobium infection prevalence was observed among participants in the 12-14-year age group with the IL13-1055C, IL13-591A, and IL13-1258A alleles. Interestingly, higher STH prevalence was also observed among participants with the IL13-1055C, IL13-591A, and IL13-1258A alleles. Furthermore, the age-associated trends of measured antibodies and cytokines of S. haematobium-infected school-children depicted a more pro-inflammatory immune profile for pupils aged up to 1l years, and an increasingly anti-inflammatory profile for pupils aged 12 years and above. This work provides insight into the influence of IL-13 gene polymorphisms on S. haematobium, and STH infections, in school-aged children (SAC).

Associations of interleukin-4 and interleukin-4 receptor loci with esophageal squamous cell carcinoma susceptibility

Some functional polymorphisms in immune-regulating genes could affect the development of esophageal squamous cell carcinoma (ESCC). We enrolled 721 patients with ESCC and 1,208 healthy controls to explore the roles of rs2227282 (C > G) and rs2243283 (C > G) loci in the interleukin-4 (IL4) gene and rs1801275 loci in the interleukin-4 receptor (IL4R) gene for the occurrence of ESCC. As for IL4, the single nucleotide polymorphism rs2227282 (C > G) conferred an overall decreased risk for ESCC (adjusted P = 0.005, power = 0.816 in GG vs. CC genetic models). A stratification analysis of IL4 rs2227282 (C > G) and rs2243283 (C > G) and IL4R rs1801275 (A > G) loci with the ESCC risk revealed that the IL4 rs2243283 (C > G) polymorphism was a protective factor for the susceptibility to ESCC in some subgroups (women: power = 0.932 in CG vs. CC and 0.956 in CG/GG vs. CC; subjects aged ≥63 years: power = 0.844 in CG/GG vs. CC; never-smokers: power = 0.893 in CG vs. CC and 0.882 in CG/GG vs. CC; never-drinkers: power = 0.904 in CG vs. CC and 0.862 in CG/GG vs. CC). We also investigated the association of IL4 rs2227282 and rs2243283 and IL4R rs1801275 loci with the lymph node status. However, a null relationship was found. In conclusion, the present study highlighted that IL4 rs2227282 (C > G) and rs2243283 (C > G) loci are protective factors for the occurrence of ESCC.

The Genetics of Human Schistosomiasis Infection Intensity and Liver Disease: A Review

Schistosomiasis remains the fourth most prevalent parasitic disease affecting over 200 million people worldwide. Control efforts have focussed on the disruption of the life cycle targeting the parasite, vector and human host. Parasite burdens are highly skewed, and the majority of eggs are shed into the environment by a minority of the infected population. Most morbidity results from hepatic fibrosis leading to portal hypertension and is not well-correlated with worm burden. Genetics as well as environmental factors may play a role in these skewed distributions and understanding the genetic risk factors for intensity of infection and morbidity may help improve control measures. In this review, we focus on how genetic factors may influence parasite load, hepatic fibrosis and portal hypertension. We found 28 studies on the genetics of human infection and 20 studies on the genetics of pathology in humans. S. mansoni and S. haematobium infection intensity have been showed to be controlled by a major quantitative trait locus SM1, on chromosome 5q31-q33 containing several genes involved in the Th2 immune response, and three other loci of smaller effect on chromosomes 1, 6, and 7. The most common pathology associated with schistosomiasis is hepatic and portal vein fibroses and the SM2 quantitative trait locus on chromosome six has been linked to intensity of fibrosis. Although there has been an emphasis on Th2 cytokines in candidate gene studies, we found that four of the five QTL regions contain Th17 pathway genes that have been included in schistosomiasis studies: IL17B and IL12B in SM1, IL17A and IL17F in 6p21-q2, IL6R in 1p21-q23 and IL22RA2 in SM2. The Th17 pathway is known to be involved in response to schistosome infection and hepatic fibrosis but variants in this pathway have not been tested for any effect on the regulation of these phenotypes. These should be priorities for future studies.

Candidate gene family-based and case-control studies of susceptibility to high Schistosoma mansoni worm burden in African children: a protocol

Background: Approximately 25% of the risk of Schistosoma mansoni is associated with host genetic variation. We will test 24 candidate genes, mainly in the T _h2 and T _h17 pathways, for association with S. mansoni infection intensity in four African countries, using family based and case-control approaches. Methods: Children aged 5-15 years will be recruited in S. mansoni endemic areas of Ivory Coast, Cameroon, Uganda and the Democratic Republic of Congo (DRC). We will use family based (study 1) and case-control (study 2) designs. Study 1 will take place in Ivory Coast, Cameroon, Uganda and the DRC. We aim to recruit 100 high worm burden families from each country except Uganda, where a previous study recruited at least 40 families. For phenotyping, cases will be defined as the 20% of children in each community with heaviest worm burdens as measured by the circulating cathodic antigen (CCA) assay. Study 2 will take place in Uganda. We will recruit 500 children in a highly endemic community. For phenotyping, cases will be defined as the 20% of children with heaviest worm burdens as measured by the CAA assay, while controls will be the 20% of infected children with the lightest worm burdens. Deoxyribonucleic acid (DNA) will be genotyped on the Illumina H3Africa SNP (single nucleotide polymorphisms) chip and genotypes will be converted to sets of haplotypes that span the gene region for analysis. We have selected 24 genes for genotyping that are mainly in the Th2 and Th17 pathways and that have variants that have been demonstrated to be or could be associated with Schistosoma infection intensity.   Analysis: In the family-based design, we will identify SNP haplotypes disproportionately transmitted to children with high worm burden. Case-control analysis will detect overrepresentation of haplotypes in extreme phenotypes with correction for relatedness by using whole genome principal components.

Candidate gene family-based and case-control studies of susceptibility to high Schistosoma mansoni worm burden in African children: a protocol

Background: Approximately 25% of the risk of Schistosoma mansoni is associated with host genetic variation. We will test 24 candidate genes, mainly in the T _h2 and T _h17 pathways, for association with S. mansoni infection intensity in four African countries, using family based and case-control approaches. Methods: Children aged 5-15 years will be recruited in S. mansoni endemic areas of Ivory Coast, Cameroon, Uganda and the Democratic Republic of Congo (DRC). We will use family based (study 1) and case-control (study 2) designs. Study 1 will take place in Ivory Coast, Cameroon, Uganda and the DRC. We aim to recruit 100 high worm burden families from each country except Uganda, where a previous study recruited at least 40 families. For phenotyping, cases will be defined as the 20% of children in each community with heaviest worm burdens as measured by the circulating cathodic antigen (CCA) assay. Study 2 will take place in Uganda. We will recruit 500 children in a highly endemic community. For phenotyping, cases will be defined as the 20% of children with heaviest worm burdens as measured by the CAA assay, while controls will be the 20% of infected children with the lightest worm burdens. Deoxyribonucleic acid (DNA) will be genotyped on the Illumina H3Africa SNP (single nucleotide polymorphisms) chip and genotypes will be converted to sets of haplotypes that span the gene region for analysis. We have selected 24 genes for genotyping that are mainly in the Th2 and Th17 pathways and that have variants that have been demonstrated to be or could be associated with Schistosoma infection intensity.   Analysis: In the family-based design, we will identify SNP haplotypes disproportionately transmitted to children with high worm burden. Case-control analysis will detect overrepresentation of haplotypes in extreme phenotypes with correction for relatedness by using whole genome principal components.

Feasibility Analysis of Interleukin-13 as a Target for a Therapeutic Vaccine

BACKGROUND

The development of therapeutic vaccines requires thorough knowledge of potential hazards associated with long-term inactivation of self-proteins. Among potential targets, interleukin 13 (IL-13) merits consideration, as monoclonal antibodies disrupting IL-13 signaling are proving to be exceedingly effective in common conditions such as atopic dermatitis.

OBJECTIVE

Given the mass publication of scientific data, an appraisal of safety aspects is challenging.

METHODS

We here provide a three-fold approach to survey clinically relevant information on off-target effects, both adverse and beneficial, that may potentially be encountered in patients undergoing long-term IL-13 inactivation. First, we review non-clinical data in vivo and in vitro. Second, we summarize safety data accumulating from patients dosed with anti-IL-13 drugs. Third, we exploit human mutation data as well as emerging large-scale genetic datasets (global exome data from 60,000 patients) to obtain information on any association of IL-13-inactivating genetic variants with disease states. In addition, we: (1) dissect the precise efficacy signals obtained with various drugs targeting IL-13 and/or IL-4, and (2) summarize unintended, but potentially beneficial effects of prolonged IL-13 inactivation on several functional systems.

RESULTS

Prolonged repression of IL-13 in several thousand patients so far has not uncovered any non-redundant functions of IL-13 in immune defense. Furthermore, missense mutations in the key genes IL-13, IL-13Rα1, IL-13Rα2, IL-4, IL-4Rα are common, while no case reports have been published on any immune deficiency or increased risk of neoplastic disease associated with such mutations, suggesting that these genes do not harbor non-redundant roles in adult outbred humans. In terms of efficacy, data from clinically used drugs strongly suggest that targeting IL-13 only, as opposed to IL-13 and IL-4, may be effective in eczema while being more selective. Importantly, several lines of evidence suggest that inhibition of IL-13 may in fact harbor potentially beneficial effects on non-targeted systems, including glucose metabolism, hepatic fibrosis, and atherosclerosis, suggesting that respective outcomes should be systematically captured in patients dosed with IL-13 interfering drugs. Collectively, available evidence suggests that IL-13 may fulfill safety requirements required for the target of a therapeutic vaccine.

Association of IL-13 rs20541 and rs1295686 variants with symptomatic asthma in a Saudi Arabian population

OBJECTIVE

Interleukin 13 (IL-13) plays a critical pro-inflammatory role in asthma. Several single nucleotide polymorphisms (SNPs) are associated with asthma susceptibility in specific populations; however, further replicative studies in other ethnic groups are mandatory.

METHODS

The association between IL-13 SNPs rs762534, rs20541, rs1295686, and rs1800925 (risk alleles A, A, T, and A, respectively) and asthma predisposition in a Saudi Arabian cohort was examined via a case-control cross-sectional study.

RESULTS

The frequencies of alleles between asthmatics and control populations were significantly different for rs20541 and rs1295686 SNPs (p < 0.001), whereas the frequencies of genotypes between asthmatics and controls were significantly different only for rs20541. The association of the risk (minor) alleles with asthma was examined using the dominant genetic model. Individuals with at least one copy of the risk alleles A (for rs20541) and T (for rs1295686) had significantly greater odds of being asthmatic (OR = 2.13, 95% CI = 1.39-3.26, p < 0.0001; OR = 1.69, 95% CI = 1.12-2.54, p = 0.008) relative to their most common homozygous genotypes. On the other hand, the minor A alleles for rs762534 and rs1800925 were not significantly associated with asthma risk. Regarding haplotype association analysis, individuals with at least one copy of the minor "risk" allele for both rs20541 and rs1295686 (CATG and CATA, respectively) had greater odds of being asthmatic relative to CGCG haplotype; however, this trend was not statistically significant (p > 0.3).

CONCLUSIONS

IL-13 minor T and A alleles for rs1295686 and rs20541, respectively, were associated with significantly higher risk of asthma in the Saudi Arabian population.

Histologic Findings and Inflammatory Reactions After Long-term Colonization of Helicobacter felis in C57BL/6 Mice

Background:

The Helicobacter felis (H. felis) mouse model has been developed for the research regarding pathogenesis of chronic gastritis and gastric cancer. The aim of this study was to investigate long-term H. felis colonization in the stomachs of C57BL/6 mice and subsequent histologic findings and inflammatory reactions including pro-inflammatory cytokines.

Methods:

Twenty-three female C57BL/6 mice at 4 weeks of age were gavaged with H. felis, and 13 control mice served as vehicle only. The mice were sacrificed at 4, 24, and 52 weeks after inoculation. The infection status and degree of inflammation were determined by culture and histopathology. The level of gastric mucosal myeloperoxidase (MPO), tumor necrosis factor alpha (TNF-α), and interleukin-1beta (IL-1β) were measured by ELISA.

Results:

The overall infection rate was 100%, as determined by the culture and histology. At 4, 24, and 52 weeks, the neutrophil and monocyte scores were significantly higher in infected mice than in control mice. At 24 weeks after inoculation, most of the infected mice showed mucosal atrophy with or without metaplasia, and a few showed focal dysplasia. Adenocarcinoma was observed in one mouse at 52 week post-infection. Gastric mucosal MPO and IL-1β levels were significantly higher in infected mice than those in control mice at 24 and 52 weeks. However, the expression of gastric mucosal TNF-α was not significantly different between the infected and control mice at any time-point.

Conclusions:

Long-term H. felis-infection in C57BL/6 mice provoked a severe inflammatory reaction and it progressed into atrophy, metaplasia, dysplasia and cancer. IL-1β might play an important role in the inflammatory response of mice to Helicobacter species.

Host determinants of reinfection with schistosomes in humans: a systematic review and meta-analysis

Background

Schistosomiasis is still a major public health burden in the tropics and subtropics. Although there is an effective chemotherapy (Praziquantel) for this disease, reinfection occurs rapidly after mass drug administration (MDA). Because the entire population do not get reinfected at the same rate, it is possible that host factors may play a dominant role in determining resistance or susceptibility to reinfection with schistosomes. Here, we systematically reviewed and meta-analyzed studies that reported associations between reinfection with the principal human-infecting species (S. mansoni, S. japonicum and S. haematobium) and host socio-demographic, epidemiological, immunological and genetic factors.

Methodology/Principal Findings

PubMed, Scopus, Google Scholar, Cochrane Review Library and African Journals Online public databases were searched in October 2013 to retrieve studies assessing association of host factors with reinfection with schistosomes. Meta-analysis was performed to generate pooled odds ratios and standardized mean differences as overall effect estimates for dichotomous and continuous variables, respectively. Quality assessment of included studies, heterogeneity between studies and publication bias were also assessed. Out of the initial 2739 records, 109 studies were included in the analyses, of which only 32 studies with 37 data sets were eligible for quantitative data synthesis. Among several host factors identified, strong positive association was found with age and pre-treatment intensity, and only slightly for gender. These factors are major determinants of exposure and disease transmission. Significant positive association was found with anti-SWA IgG4 level, and a negative overall effect for association with IgE levels. This reconfirmed the concept that IgE/IgG4 balance is a major determinant of protective immunity against schistosomiasis. Other identified determinants were reported by a small number of studies to enable interpretation.

Conclusions

Our data contribute to the understanding of host-parasite interaction as it affects reinfection, and is a potential tool to guide planning and tailoring of community interventions to target high-risk groups.

One of the major challenges of schistosomiasis control is that disease prevalence reverts to baseline levels after mass drug administration due to high rate of reinfection. Host factors play a major role in determining resistance or susceptibility to reinfection with schistosomiasis and other diseases. We systematically searched and analyzed studies that identified potential host determinants of reinfection with schistosomes. Among demographic variables, age but not gender was strongly associated with reinfection with schistosomes. Pretreatment infection intensity was also identified as a major determinant of reinfection. Positive association with IgG4 levels and negative association with IgE levels reconfirmed the notion that IgE/IgG4 balance is the major factor controlling protective immunity against schistosomiasis. Other factors were reported by few studies to allow correct inferences. These results contribute to our understanding of host-parasite relationship as it affects reinfection, and will be useful for planning and targeting the limited resources for intervention on high-risk groups.

Pulmonary vascular disease associated with parasitic infection--the role of schistosomiasis

Parasitic diseases have been known to cause pulmonary vascular lesions. Schistosomiasis is the most common parasitic disease associated with pulmonary arterial hypertension, although other trematodes have been implicated. Systematic evaluation of and interest in this problem have been rekindled because of the current availability of pulmonary arterial hypertension treatment.

Association analysis of polymorphisms in IL-3, IL-4, IL-5, IL-9, and IL-13 with Graves' disease

BACKGROUND

Graves' disease (GD) is a common autoimmune disorder with genetic predisposition. There is strong evidence that the Chr.5q31-33 region, which contains the immune response cytokine genes [interleukin (IL)-3, IL-4, IL-5, IL-9, and IL-13], is linked to autoimmune thyroid disorders in Chinese and Japanese populations. The aim of the present study is to elucidate whether the single nucleotide polymorphisms (SNP) and the interaction of variants in the 5 genes are associated with the development of GD and Graves' ophthalmopathy (GO).

MATERIALS AND METHODS

GD patients (no.=751), with 190 of GO patients and healthy control subjects (no.=748) were included in this study. Six SNP [rs40401 (IL-3), rs2070874 (IL-4), rs2069812 (IL-5), rs1859430 (IL-9), rs2069868 (IL-9), and rs20541 (IL-13)] were genotyped by SNPstream Genotyping System.

RESULTS

There was a significant increase of C allele of rs40401 in GD [odds ratio (OR)=1.18 [95% confidence interval (CI): 1.02-1.36], pallele=0.028] and GO [OR=1.30 (95%CI: 1.04-1.63), pallele=0.022] patients compared with those in the controls. The C allele of the rs2069812 was also significantly associated with GD [OR=1.22 (95%CI: 1.04-1.44), pallele=0.015] and GO [OR=1.45 (95%CI: 1.13-1.86), pallele=0.003] patients. Haplotype analysis showed a predominant increase of the 2 SNP (rs40401-rs2069812, CC) and all the 6 SNP (CCCCCC) haplotype in GD (OR=1.70, OR=3.70, respectively) and even stronger in GO (OR=2.18, OR=7.01, respectively) patients.

CONCLUSIONS

The results suggested that the polymorphism of IL-3 (rs40401) and IL-5 (rs2069812) were associated with GD and GO susceptibility in Chinese population. The interaction of 6-locus from the 5 genes might confer higher risk for GD and GO than single risk allele.

Schistosomiasis in the People's Republic of China: the era of the Three Gorges Dam

The potential impact of the Three Gorges Dam (TGD) on schistosomiasis transmission in China has invoked considerable global concern. The TGD will result in changes in the water level and silt deposition downstream, favoring the reproduction of Oncomelania snails. Combined with blockages of the Yangtze River's tributaries, these changes will increase the schistosomiasis transmission season within the marshlands along the middle and lower reaches of the Yangtze River. The changing schistosome transmission dynamics necessitate a comprehensive strategy to control schistosomiasis. This review discusses aspects of the epidemiology and transmission of Schistosoma japonicum in China and considers the pathology, clinical outcomes, diagnosis, treatment, immunobiology, and genetics of schistosomiasis japonica together with an overview of current progress in vaccine development, all of which will have an impact on future control efforts. The use of synchronous praziquantel (PZQ) chemotherapy for humans and domestic animals is only temporarily effective, as schistosome reinfection occurs rapidly. Drug delivery requires a substantial infrastructure to regularly cover all parts of an area of endemicity. This makes chemotherapy expensive and, as compliance is often low, a less than satisfactory control option. There is increasing disquiet about the possibility that PZQ-resistant schistosomes will develop. Consequently, as mathematical modeling predicts, vaccine strategies represent an essential component in the future control of schistosomiasis in China. With the inclusion of focal mollusciciding, improvements in sanitation, and health education into the control scenario, China's target of reducing the level of schistosome infection to less than 1% by 2015 may be achievable.

Familial aggregation of human helminth infection in the Poyang lake area of China with a focus on genetic susceptibility to schistosomiasis japonica and associated markers of disease

Human helminthiases are common in China, especially in rural areas where sanitation conditions are poor. Soil-transmitted helminths (STHs) are predominantly found in the southern provinces. Schistosoma japonicum is also endemic to southern China. Here we review the prevalence of helminth infections and polyparasitism in China, and discuss the interactions between helminth parasites in the co-infected host. It is clear that STHs are more prevalent in rural China than previously suggested emphasizing the need for systematic control of STHs. Further, the need for improved sanitation and hygiene conditions to prevent parasite transmission is highlighted. We provide supporting evidence for human genetic susceptibility to both single helminth infection and polyparasitism, and suggest that susceptibility to helminths infections may not be independent of one or the other. We demonstrate an association between single nucleotide polymorphism (SNP) variants in IL-5 and symptomatic S. japonicum infection and discuss the potential role of IL-5 in other helminth infections. Fundamental to disease and morbidity control is adequate and effective diagnosis and surveillance of disease. We discuss the role of sICAM-1 and TNFR-I and -II as candidate markers for schistosome-induced hepatomegaly and fibrosis, and their potential for assessing disease stage and progression in schistosomiasis.

Conquering 'snail fever': schistosomiasis and its control in China

Schistosomiasis japonica is a serious parasitic disease and a major health risk for more than 60 million people living in the tropical and subtropical zones of south China. The disease is a zoonosis and its cause, the parasitic trematode Schistosoma japonicum, has a range of mammalian reservoirs, making control efforts difficult. Current control programs are heavily based on community chemotherapy with a single dose of the highly effective drug praziquantel. However, vaccines (for use in bovines and in humans) in combination with other control strategies are needed to eliminate the disease. In this review, we provide an overview of the transmission, clinical features, pathogenesis, diagnosis, treatment, genetics and susceptibility, epidemiology, and prospects for control of schistosomiasis japonica in China. The threat posed by the Three Gorges Dam may undermine control efforts because it will change the local ecology and associated schistosomiasis transmission risks over the next decade and beyond.

Immunopathogenesis of human schistosomiasis

Schistosomiasis continues to be a significant cause of parasitic morbidity and mortality worldwide. This review considers the basic features of the pathology and clinical outcomes of hepatointestinal and genitourinary schistosomiasis, presents an overview of the numerous studies on animal models that have clarified many of the immunopathological features, and provides insight into our current understanding of the immunopathogenesis and genetic control of human schistosomiasis. In murine schistosomiasis, pathology is induced by a CD4(+) Th2 driven granulomatous response directed against schistosome eggs lodged in the host liver. The Th2 cytokines IL-4 and IL-13 drive this response, whereas IL-10, IL13Ralpha2, IFN-gamma and a subset of regulatory T-cells act to limit schistosome induced pathology. A variety of cell types including hepatic stellate cells, alternatively activated macrophages and regulatory T-cells have also been implicated in the pathogenesis of schistosomiasis. Current knowledge suggests the immunopathogenic mechanisms underlying human schistosomiasis are likely to be similar. The review also considers the future development of anti-pathology schistosome vaccines. As fibrosis is an important feature of many other diseases such as Crohn's disease and sarcoidosis, a comprehensive understanding of the cellular and molecular mechanisms involved in schistosomiasis may also ultimately contribute to the development an effective disease intervention strategy for other granulofibrotic diseases.

Detecting the effects of selection at the population level in six bovine immune genes

BACKGROUND

The capacity of a species or population to respond to and survive novel infectious disease challenge is one of the most significant selective forces shaping genetic diversity and the period following animal domestication was likely one of the most important in terms of newly emerging diseases. Inter-specific genome-wide comparison has suggested that genes, including cluster of differentiation 2 (CD2), ADP-ribosyltransferase 4 (ART4), tyrosine kinase binding protein (TYROBP) and interleukins IL2, IL5, IL13, may have undergone positive selection during the evolution of the bovine lineage. Past adaptive change implies that more recent variation may have also been subject to selective forces.

RESULTS

In this paper, we re-sequence each of these genes in cattle cohorts from Europe, Africa and Asia to investigate patterns of polymorphism at the population level. Patterns of diversity are higher within Bos indicus suggesting different demographic history to that of Bos taurus. Significant coding polymorphism was observed within each of the cell-surface receptors. In particular, CD2 shows two divergent haplotypes defined by a series of six derived nonsynonymous substitutions that are significantly clustered on the extracellular surface of the protein and give significant values for Fay and Wu's H, strongly suggesting a recent adaptive history. In contrast, the signaling molecules (especially IL13) display outlying allele frequency spectra which are consistent with the effects of selection, but display negligible coding polymorphism.

CONCLUSION

We present evidence suggestive of recent adaptive history in bovine immune genes; implying some correspondence between intra- and inter-specific signals of selection. Interestingly, three signaling molecules have negligible nonsynonymous variation but show outlying test statistics in contrast to three receptors, where it is protein sequence diversity that suggests selective history.