Human eosinophils modulate peripheral blood mononuclear cell response to Schistosoma mansoni adult worm antigen in vitro.

High numbers of eosinophils are observed in parasitic infections and allergic diseases, where they are proposed to be terminally differentiated effector cells that play beneficial role in host defence, or cause harmful inflammatory response. Eosinophils have been associated with killing of schistosomulae in vitro, but there is growing evidence that eosinophils can play additional immuno-regulatory role. Here, we report results of a study that examines peripheral blood mononuclear cell (PBMC) cytokine responses to Schistosoma mansoni adult worm antigen (SWA) when stimulated alone or enriched with autologous eosinophils. Production of the Th-2 type cytokines interleukin (IL)-4, IL-5 and IL-13 was lower (P = 0·017, 0·018 and <0·001, respectively) in PBMC + eosinophil cultures than in PBMC-only cultures stimulated with SWA. Substantial levels of IL-13, IL-10, interferon gamma and tumour necrosis factor alpha were recorded in cultures of eosinophils, but none of these cytokines showed significant association with the observed eosinophil-induced drop in cytokine responses of PBMC. Transwell experiments suggested that the observed effect is due to soluble mediators that downmodulate production of Th-2 type cytokines. This study shows that eosinophils may down-modulate schistosome-specific Th-2 type cytokine responses in S. mansoni-infected individuals. The mechanism of this immune modulation remains to be elucidated.

A late IL-33 response after exposure to Schistosoma haematobium antigen is associated with an up-regulation of IL-13 in human eosinophils.

IL-33, a proposed alarmin, stimulates innate immune cells and Th2 cells to produce IL-13 and is rapidly upregulated upon antigen exposure in murine helminth infection. The human IL-33 response to helminth antigen was analysed in Malians infected with Schistosoma haematobium by disrupting parasite integrity via chemotherapy. Plasma IL-33 was measured pretreatment, and 24 h and 9 weeks post-treatment. At 24 h post-treatment, IL-33 levels were low. Nine week post-treatment IL-33 levels were elevated and were associated with an increase in intracellular IL-13 in eosinophils. Up-regulation of intracellular IL-13 in eosinophils was also associated with eosinophil expression of ST2L, the IL-33 receptor. IL-33 may play an important downstream role in the human response to schistosome adult worm antigen exposure.

Molecular characterisation of kappa-5, a major antigenic glycoprotein from Schistosoma mansoni eggs.

The major immunopathological consequences of infection with Schistosoma mansoni, a T helper type 2 response and granuloma formation leading to fibrotic tissue damage, are caused by the egg stage of the parasite. Three antigens of S. mansoni eggs, termed IPSE/alpha-1, omega-1 and kappa-5, have been found to be the primary targets of the egg-directed antibody response of the host. Here, we report on the isolation, cloning and characterisation of kappa-5. Apart from an uncharacterised mRNA sequence in S. japonicum, no significant similarities of kappa-5 to known sequences from other species were found. In contrast to IPSE/alpha-1 and omega-1, which have been found only in eggs, kappa-5 was present in miracidia as well as in eggs at the mRNA and protein levels. In eggs, isoforms of kappa-5 were observed with both three and four fully occupied N-glycosylation sites, while in miracidia only one isoform with four N-glycans could be detected. Interestingly, in Western blots sera from S. mansoni-infected Africans were reactive against kappa-5 with IgE and IgG isotype antibodies, but against IPSE/alpha-1 and omega-1 only with IgG antibodies. The further characterisation of kappa-5 as one of the three major egg antigens should help to better understand the immunology and immunopathology of schistosomiasis.

Hepatosplenomegaly associated with chronic malaria exposure: evidence for a pro-inflammatory mechanism exacerbated by schistosomiasis.

In sub-Saharan Africa, chronic hepatosplenomegaly, with palpable firm/hard organ consistency, is common, particularly among school-aged children. This morbidity can be caused by long-term exposure to malaria, or by Schistosoma mansoni, and it is exacerbated when these two occur together. Although immunological mechanisms probably underlie the pathogenic process, these mechanisms have not been identified, nor is it known whether the two parasites augment the same mechanisms or induce unrelated processes that nonetheless have additive or synergistic effects. Kenyan primary schoolchildren, living in a malaria/schistosomiasis co-transmission area, participated in cross-sectional parasitological and clinical studies in which circulating immune modulator levels were also measured. Plasma IL-12p70, sTNF-RII, IL-10 and IL-13 levels correlated with relative exposure to malaria, and with hepatosplenomegaly. Soluble-TNF-RII and IL-10 were higher in children infected with S. mansoni. Hepatosplenomegaly caused by chronic exposure to malaria was clearly associated with increased circulating levels of pro-inflammatory mediators, with higher levels of regulatory modulators, and with tissue repair cytokines, perhaps being required to control the inflammatory response. The higher levels of regulatory modulators amongst S. mansoni infected children, compared to those without detectable S. mansoni and malarial infections, but exposed to malaria, suggest that S. mansoni infection may augment the underlying inflammatory reaction.

Intestinal polyparasitism in a rural Kenyan community.

BACKGROUND: Polyparasitism seems to be a common feature in human populations in sub-Saharan Africa. However, very little is known about its epidemiological significance, its long term impact on human health or the types of interactions that occur between the different parasite species involved. OBJECTIVES: To determine the prevalence and co-occurrence of intestinal parasites in a rural community in the Kibwezi, Makueni district, Kenya. DESIGN: A cross sectional study. SETTING: Kiteng'ei village, Kibwezi, Makueni district, between May and September 2006. SUBJECTS: One thousand and forty five who comprised of 263 adult males, 271 adult females > 15 years of age and 232 boys, and 279 girls <15 years of age. INTERVENTIONS: All infected members of the community were offered Praziquantel (at dosages of 40 mg/kg body weight) for Schistosomiasis and Albendazole (600 mg) for soil transmitted helminths. RESULTS: A total of ten intestinal parasite species (five protozoan and five helminth parasite species) were present in this community and polyparasitsm was common in individuals 5-24 years of age with no gendar related differences. Most of the infections were mild. The protozoan parasites of public health significance present were Entamoeba histolytica and Giardia lamblia with prevalence of 12.6% and 4.2%, respectively. The helminth parasites of public health significance in the locality were Schistosoma mansoni with a prevalence of 28%, and hookworms prevalence of 10%. About 53% of the study population harboured intestinal parasite infections, with 31% of the infected population carrying single parasite species infections, and 22% harbouring two or more intestinal parasite species per individual. Significant positive associations (p values <0.05) were observed between S. mansoni and hookworms, hookworms and Hymenolepis. nana and Entamoeba histolytica and Entamoeba coli. CONCLUSION: Intestinal polyparasitism was common in the Kiteng'ei community, particularly in individuals aged of 5-24 years old. An integrated control programme of approach would be recommended for the control of S. mansoni, hookworms and Entamoeba histolytica for this community.

Parasitic worms and inflammatory diseases.

The debate on whether infection precipitates or prevents autoimmunity remains a contentious one. Recently the suggestion that some unknown microbe can be at the origin of some chronic inflammatory diseases has been countered by accumulating evidence that decreasing infection rates might have an important role to play in the rising prevalence of autoimmune disorders. The 'Hygiene Hypothesis' was initially postulated to explain the inverse correlation between the incidence of infections and the rise of allergic diseases, particularly in the developed world. Latterly, the Hygiene Hypothesis has been extended to also incorporate autoimmune diseases in general. Amongst the various infectious agents, a particular emphasis has been put on the interaction between parasitic worms and humans. Worm parasites have co-evolved with the mammalian immune system for many millions of years and during this time, they have developed extremely effective strategies to modulate and evade host defences and so maintain their evolutionary fitness. It is therefore reasonable to conclude that the human immune system has been shaped by its relationship with parasitic worms and this may be a necessary requirement for maintaining our immunological health. Fully understanding this relationship may lead to novel and effective treatments for a host of deleterious inflammatory reactions.

Characterization of immunoglobulin binding by schistosomes.

Although controversial, schistosomes are believed to cloak themselves in antibody through non-specific interactions with the immunoglobulin (Ig) molecule. The acquisition of host Ig by the schistosome may mask its foreign status and/or interfere with Fc-dependent functions. We report experiments aimed at characterizing the interaction between Ig-Fc and paramyosin, a schistosome Fc-receptor previously reported to bind human IgG. We show that certain Ig classes, in particular murine IgG2b and IgG3, are not only able to bind recombinant paramyosin, but also associate with other parasite proteins. The Fc region of IgG contains four hydrophobic patches, two of which are known to interact with distinct molecules: one in the Cgamma2-Cgamma3 interdomain region bound by protein G, mannose binding lectin (MBL), and the neonatal Fc-receptor (FcRn), and one at the top of the Cgamma2 domain bound by phagocytic FcgammaRs and C1q. We provisionally discounted the involvement of these regions, since IgG binding by paramyosin did not inhibit FcgammaR-mediated NADPH respiratory bursts, and protein G was unable to block IgG binding to paramyosin. Given their apparent low affinity, we postulate hydrogen bonding between reactive residues in a hydrophobic patch at the bottom of the Cgamma3 domain and negatively charged Glu or Asp amino acids in paramyosin.

Comparative epidemiology of Chlamydia trachomatis infection among men attending sexually transmitted disease clinics with and without indication for testing.

Understanding the epidemiology of Chlamydia trachomatis infection in men without indication for testing (without symptoms, signs, or a report of sexual contact with an infected partner) is of crucial importance to reduce the heavy burden of this infection, particularly because this group of men is not usually offered testing in different clinical settings. Using electronic medical records of two STD clinics in Connecticut, 2000-02, this study identified the risk factors of C. trachomatis infection in men with and without indication for testing. In both groups, men who were younger than 30, African-American, or had a prior history of C. trachomatis infection were significantly more likely to be infected. Since a system for routine reproductive health care of young men does not currently exist, health-care providers need to promote an increased awareness of C. trachomatis infection among their male patients who are at increased risk of infection.

Condom effectiveness for prevention of Chlamydia trachomatis infection.

BACKGROUND/OBJECTIVES: A growing body of evidence is increasingly demonstrating the effectiveness of condoms for sexually transmitted infection (STI) prevention. The purpose of the present analysis was to provide a disease specific estimate for the effectiveness of condoms in preventing Chlamydia trachomatis infection while controlling for known exposure to infection. METHODS: Condom effectiveness for C trachomatis was estimated using a medical record database from a public sexually transmitted disease clinic (n = 1455). Clients were classified as having known exposure to C trachomatis if they presented to the clinic as a contact to an infected partner. RESULTS: Among clients with known exposure, 13.3% of consistent condom users were diagnosed with C trachomatis infection compared to 34.4% of inconsistent condom users (adjusted odds ratio = 0.10; 95% CI: 0.01 to 0.83). Among clients with unknown exposure, there was no observed protective effect of condoms. CONCLUSIONS: This study provides further evidence that condoms are effective in preventing C trachomatis infection by reporting a disease specific estimate and restricting analyses to individuals with known exposure.

Hepatosplenic morbidity in two neighbouring communities in Uganda with high levels of Schistosoma mansoni infection but very different durations of residence.

Peri-portal fibrosis can be a serious sequelae of Schistosoma mansoni infection. Age or duration of exposure have been identified as important risk factors, but their relative importance cannot be easily separated. Here, we have compared two cohorts, aged 6-50 years and resident for ten years or since birth, from two neighbouring villages (Booma and Bugoigo) on the eastern shore of Lake Albert, Uganda. Parasitological measurements were similar, whereas the prevalence of peri-portal fibrosis was 5-fold higher in Booma. Data from the cohorts were pooled to assess the relative contribution of age and duration of residency on the risk of disease. Amongst adults, duration of residency was the critical risk factor--individuals aged 17-31 years resident for more 22 years had an almost 12-fold increased risk of fibrosis than those resident for less than 15 years. Height-standardised Splenic Vein Diameter (SVD), Portal Vein Diameter (PVD), Para-sternal Liver Length (PLL) and Spleen Length (SL) values were all higher in Booma, and each organometric parameter except PLL increased with the severity of fibrosis. Our results clearly demonstrate that duration of exposure is a critical risk factor for the development of peri-portal fibrosis and its sequelae in adults. This parameter should therefore be a routine measurement during epidemiological surveys of S. mansoni.

Efficacy and side effects of praziquantel treatment in a highly endemic Schistosoma mansoni focus at Lake Albert, Uganda.

The aim of the study was to assess the efficacy and side effects following single and repeated (6 weeks apart) praziquantel treatment (40 mg/kg) in a Schistosoma mansoni-endemic focus with long-standing transmission at Lake Albert in Uganda between December 1996 and January 1997. The results were based on 482 individuals, randomly representing all age and both gender groups. The cure rate following the first and second treatments was 41.9% and 69.1%, respectively. The cure rate was higher in adults than in children, irrespective of intensity of infection. In addition, the cure rate declined markedly with increasing intensity of infection. The reduction in intensity of infection was marked, being 97.7% and 99.6% after the first and second treatments, respectively. A pre- and post-treatment symptom questionnaire revealed a broad range of side effects, including abdominal pain and diarrhoea. However, no serious or long-lasting complications affecting compliance were observed. The marked reductions in faecal egg excretion and the acceptable level of side effects point to a single praziquantel treatment (40mg/kg) as the strategy of choice in such a highly endemic S. mansoni focus.

Defective in vivo induction of functional type 2 cytokine responses in aged mice.

Aged mice have various defects in their immune system. We report that following in vivo challenge with type 2 cytokine-inducing Schistosoma mansoni eggs, aged mice fail to produce type 2 cytokines and also have impaired antigen-specific antibody production. Using two separate type 2 cytokine-dependent in vivo models, the synchronous pulmonary schistosome egg granuloma model and infection with the gastro-intestinal nematode Nippostrongylus brasiliensis, aged mice were shown to have a dramatically impaired capacity to elicit a functional type 2 response, i. e. respectively, impaired pulmonary granulomas and delayed rejection of intestinal worms. Aged mice did not develop eosinophilia and had impaired production of antigen specific IgE. Defective induction of type 2 responses was associated with negligible IL-2 and elevated IFN-gamma production by cells from aged mice. Naive aged mice had increased numbers of Th1, Th2 and Tc1 cells compared to young animals. In vivo type 2 challenge increased the frequencies of Th1 and Tc1 cells and reducing Th2 cell numbers in aged mice. These data demonstrate that a consequence of ageing is a profound in vivo defect in the capacity to elicit type 2 cytokine responses and such an impairment in type 2 responsiveness may account for the increased incidence of various type 1 cytokine-mediated diseases in aged individuals.

Expression of interleukin-9 leads to Th2 cytokine-dominated responses and fatal enteropathy in mice with chronic Schistosoma mansoni infections.

Mice infected with Schistosoma mansoni develop Th2 cytokine-mediated granulomatous pathology that is focused on the liver and intestines. In this study, transgenic mice constitutively expressing IL-9 were infected with S. mansoni and the outcome of infection was determined. Eight weeks after infection, transgenic mice with acute infections had a moderate increase in Th2 cytokine production but were overtly normal with respect to parasite infection and pathological responses. Transgenic mice with chronic infections died 10 weeks after infection, with 86% of transgenic mice dead by week 12 of infection, compared to 7% mortality in infected wild-type mice. Stimulation of mesenteric lymph node cells from infected transgenic mice with parasite antigen elicited elevated interleukin-4 (IL-4) and IL-5 production and reduced gamma interferon and tumor necrosis factor alpha production compared to the responses in wild-type mice. Morbid transgenic mice had substantial enlargement of the ileum, which was associated with muscular hypertrophy, mastocytosis, eosinophilia, goblet cell hyperplasia, and increased mucin expression. We also observed that uninfected transgenic mice exhibited alterations in their intestines. Although there was hepatic mastocytosis and eosinophilia in infected transgenic mice, there was no hepatocyte damage. Death of transgenic mice expressing IL-9 during schistosome infection was primarily associated with enteropathy. This study highlights the pleiotropic in vivo activity of IL-9 and demonstrates that an elevated Th2 cytokine phenotype leads to death during murine schistosome infection.

Immune responses during the acute stages of infection with the intestinal trematode Echinostoma caproni.

This study investigated the nature of the immune response of C57BL/6 mice infected with the trematode Echinostoma caproni. To determine the preferential development of either a Th1 or Th2 cytokine pattern during early stages of infection, cytokine production by spleen and mesenteric lymph node (MLN) cells during the first 3 weeks of infection was followed. Whereas spleen cells failed to respond to antigen stimulation, MLN cells produced IFN-gamma and to a lesser extent IL-4. IL-5 levels were elevated throughout the period studied. The humoral response was consistent with a Th1 cytokine pattern as antigen-specific IgG2a antibodies were preferentially developed. We investigated whether IFN-gamma is critical for establishment of E. caproni infection. Worm burden in infected mice treated with a single injection of anti-IFN-gamma mAb was significantly reduced compared to that of animals treated with a control antibody.

Elevated type 1, diminished type 2 cytokines and impaired antibody response are associated with hepatotoxicity and mortalities during Schistosoma mansoni infection of CD4-depleted mice.

During murine Schistosoma mansoni infections parasite eggs evoke a type 2 cytokine-dependent and CD4(+) T cell-mediated granulomatous response in the liver. In this study CD4(+) T cell-depleted CBA / Ca mice developed hepatic steatosis and had high mortalities during early acute schistosome infection. CD4-depleted mice had smaller liver granulomas and reduced hepatic fibrosis. The hepatocytotoxicity was characterized by microvesicular steatosis and neutrophil infiltration. The livers of depleted mice had similar levels of apoptosis as control infected mice but had a marked increase in lipid peroxidation indicative of their livers being under oxidative stress. CD4-depleted mice had impaired egg excretion and exacerbated intestinal pathology. A type 1 cytokine-dominated response was present in infected CD4-depleted mice and relatively reduced production of type 2 cytokines. Antibody responses to parasite antigens were also substantially reduced. Transfer of immune serum or IgG significantly delayed mortalities in depleted mice and prevented hepatocyte damage. Although biasing the cytokine dichotomy to a type 1-dominated response during murine schistosome infection is desirable with respect to certain pathological processes, i. e. it will reduce the granulomatous inflammation and hepatic fibrosis, these effects contribute to fatal pathology if there is reduced protective type 2 cytokines and a defect in antibody responses.

Paramyosin is a major target of the human IgA response against Schistosoma japonicum.

Human resistance and susceptibility to schistosomiasis is associated with age and specific antibody isotype responses against worm (SWAP) and egg (SEA) antigens. In a cross-sectional study of 176 individuals infected with Schistosoma japonicum in the Philippines, strikingly similar isotype response patterns against SWAP and SEA was observed when compared to other endemic areas. Interestingly, IgA titres to SWAP correlated with older age among S. japonicum-infected individuals (n = 176, P < 0.01), suggesting a role for this isotype in protective immunity. To identify the molecular targets of human IgA, 17 high-IgA/SWAP responders were identified from the said population. IgA antibodies from the majority (14/17) of these individuals recognized a band of 97 kDa (Sj97), comigrating in immunoblots with the myofibrillar protein paramyosin. The antigen was confirmed as paramyosin by expressed sequence tag (EST)-analysis of four clones obtained by screening an adult S. japonicum cDNA library with pooled IgA antisera and mouse antiparamyosin polyclonal antibodies. The identification of paramyosin as a major target of human IgA raises its potential as a vaccine candidate that targets mucosal immune responses. Since this antigen is exposed on the parasite surface only during the lung stages, we propose that human IgA contributes to parasite attrition during schistosome migration in the lungs.

Nitric oxide and the Th2 response combine to prevent severe hepatic damage during Schistosoma mansoni infection.

During infection with Schistosoma mansoni, NO production increases following the deposition of parasite eggs in the liver. In wild-type C57BL/6 mice, NO levels peak during the sixth week of infection and are subsequently down-regulated. Inducible NO synthase (iNOS) mRNA was found in diseased liver tissue along with TNF-alpha and IFN-gamma, which are known promoters of iNOS expression. Mice treated with aminoguanidine, a selective inhibitor of iNOS, exhibited cachexia and exacerbated liver pathology, suggesting that NO limits hepatocyte damage when the liver is first exposed to eggs. Hepatic iNOS is up-regulated in SCID mice, indicating that NO production is part of an innate response. Studies with infected highly susceptible IL-4-/- mice revealed that prolonged NO production is in itself deleterious and that a major function of the Th2 response, which is severely compromised in the absence of IL-4, is to regulate NO production. In these animals, plasma NO levels are high compared with those in infected wild-type mice and remain elevated until death. Nevertheless, the underlying importance of NO is illustrated by the finding that aminoguanidine treatment leads to more severe liver disease and reduced time to death in infected IL-4-/- mice.