Studies with tryptophan metabolites in vitro: Kynurenine metabolism in liver homogenates of normal and Schistosoma mansoni-infested mice

The conversion of kynurenine into kynurenic acid and anthranilic acid in both normal and Schistosoma mansoni-infested mouse liver was investigated. It was found that in the S. mansoni-infested mouse liver there is probably a deficiency of pyridoxal phosphate that resulted in an inhibition of kynurenine transaminase and a low production of kynurenic acid. Deoxypyridoxine and its phosphorylated derivative inhibited kynurenine transaminase in the normal liver in a pattern qualitatively similar to that observed with infested liver. The lowered concentration of pyridoxal phosphate in the infested liver is discussed in view of the possibility of two combined mechanisms: (a) an antimetabolite being secreted by the infesting worms or present in its eggs that partially inhibited the phosphorylation of pyridoxal, and (b) concentration of pyridoxal phosphate by the worms, resulting in a lowered concentration of the cofactor in the host tissue.     

Unique T Cells with Unconventional Cytokine Profiles Induced in the Livers of Mice during Schistosoma mansoni Infection

During infection with Schistosoma, serious hepatic disorders are induced in the host. The liver possesses unique immune systems composed of specialized cells that differ from those of other immune competent organs or tissues. Host immune responses change dramatically during Schistosoma mansoni infection; in the early phase, Th1-related responses are induced, whereas during the late phase Th2 reactions dominate. Here, we describe unique T cell populations induced in the liver of mice during the period between Th1- and Th2-phases, which we term the transition phase. During this phase, varieties of immune cells including T lymphocytes increase in the liver. Subsets of CD4⁺ T cells exhibit unique cytokine production profiles, simultaneously producing both IFN-γ and IL-13 or both IFN-γ and IL-4. Furthermore, cells triply positive for IFN-γ, IL-13 and IL-4 also expand in the S. mansoni-infected liver. The induction of these unique cell populations does not occur in the spleen, indicating it is a phenomenon specific to the liver. In single hepatic CD4⁺ T cells showing the unique cytokine profiles, both T-bet and GATA-3 are expressed. Thus, our studies show that S. mansoni infection triggers the induction of hepatic T cell subsets with unique cytokine profiles.     

Involvement of IL-18 in the Expansion of Unique Hepatic T Cells with Unconventional Cytokine Profiles during Schistosoma mansoni Infection

Infection with schistosomes invokes severe fibrotic granulomatous responses in the liver of the host. Schistosoma mansoni infection induces dramatic fluctuations in Th1 or Th2 cytokine responses systemically; Th1 reactions are provoked in the early phase, whilst Th2 responses become dominant after oviposition begins. In the liver, various unique immune cells distinct from those of conventional immune competent organs or tissues exist, resulting in a unique immunological environment. Recently, we demonstrated that S. mansoni infection induces unique CD4⁺ T cell populations exhibiting unconventional cytokine profiles in the liver of mice during the period between Th1- and Th2-phases, which we term the transition phase. They produce both IFN-γ and IL-4 or both IFN-γ and IL-13 simultaneously. Moreover, T cells secreting triple cytokines IFN-γ, IL-13 and IL-4 were also induced. We term these cells Multiple Cytokine Producing Hepatic T cells (MCPHT cells). During the transition phase, when MCPHT cells increase, IL-18 secretion was up-regulated in the liver and sera. In S. mansoni-infected IL-18-deficient mice, expansion of MCPHT cells was curtailed. Thus our data suggest that IL-18 produced during S. mansoni infection play a role in the expansion of MCPHT cells.     

Schistosoma mansoni: Effect of dietary zinc supplement on egg granuloma in Swiss mice treated with praziqantel

Schistosomiasis is one of the most important parasitic diseases in Egypt and chemotherapy is considered the most effective method of control. This study was conducted to assess the effectiveness of zinc administration against Schistosoma mansoni infection by evaluating the activities of arylesterase and paraoxonase (PON1) enzymes, and the degree of liver damage.One hundred and twenty albino mice were divided into two groups; one was an infected control and the other a treated group which was further subdivided into three according to the praziquantel and zinc supplementation given. Blood and liver samples, collected 10 weeks post-infection, were subjected to parasitological, histopathological, and enzyme assays, and immunological studies. The results showed that dietary zinc supplementation led to marked reduction in worm load, and egg deposition in the liver and intestine.Histopathological examination showed marked reduction in the number and diameter of hepatic granulomas in the treated groups. The activity of arylesterase and PON1 enzymes were partially restored in infected animals receiving zinc. IL-10 mRNA expression was higher in the treated groups than in the infection control group. In conclusion, zinc administration could be a promising adjuvant therapy for S. mansoni infection.     

Bile duct hyperplasia in mice infected with Schistosoma mansoni

Schistosoma mansoni releases large amounts of proline into the hepatoenteric circulation. Because proline release has been linked to bile duct hyperplasia in fascioliasis, the current investigation tested the possibility that such hyperplasia might occur in schistosomiasis. The lumenal perimeter and wall thickness in bile ducts was compared between infected and uninfected mice. In those harboring 5 week old S. mansoni infections there was a 180% increase in the lumenal perimeter of the duct (P<0.001) and a 580% increase in the thickness of the duct wall (P<0.001). These results tend to support data linking proline to bile duct and liver fibroblast proliferation.     

Green tea (Camellia sinesis) ameliorates female Schistosoma mansoni-induced changes in the liver of Balb/C mice

This study was designed to assess the effect of green tea, an aqueous extract of Camellia sinensis, on the oxidative stress, antioxidant defense system and liver pathology of Schistosoma mansoni-infected mice. Green tea at concentration of 3% (w/v) was given orally to treated mice as sole source of drinking water from the end of the 4th week to the end of 10th week post-infection; untreated mice were allowed to drink normal water. The data of the studied S. mansoni-infected mice exhibited a suppression of hepatic total antioxidant capacity, superoxide dismutase (SOD), catalase (CAT) activity and glutathione content. The liver lipid peroxidation was deleteriously elevated in S. mansoni-infected mice. The hepatic total protein content, AST and ALT activities were profoundly decreased in the S. mansoni-infected mice. Most hepatocytes were damaged and showed abnormal microscopic appearance with aggressive necrosis. Both total protein and glycogen levels have been greatly reduced as indicated by histochemical examination. The treatment of S. mansoni-infected mice with green tea succeeded to suppress oxidative stress by decreasing the lipid peroxides but failed to significantly enhance the antioxidant defense system and deteriorated changes owing to liver damage and necrosis. In consistence with biochemical data, histopathological and histochemical data indicated that treatment of S. mansoni-infected mice with green tea could ameliorate hepatocytes thus reduce cellular necrosis and partially restore both total protein and glycogen levels. Thus, the study concluded that the green tea suppresses the oxidative stress through its constituent with free radicals scavenging properties rather than through the endogenous antioxidant defense system.     

Schistosoma mansoni: Role in vivo of complement in primary infection of mice

The role of complement in the control of the primary Schistosoma mansoni infection in mice was investigated in vivo. The number of recovered adult schistosomes 6–7 weeks postinfection was used as a parasitological criterion of immunity. No significant difference in the worm burden was observed between C5-sufficient and C5-deficient mice. In contrast, when cobra venom factor (CVF) was injected into normal or C5-deficient mice 24 hr before challenge, a significant increase of the worm burden was noticed in comparison to the untreated mice. These results indicated that, although C5 and probably the late complement components are not essential for the control of the primary infection, the alternative pathway and some of its components are involved. In fact, the injection of C3 2 hr before infection of CVF-treated mice completely restored the immunity. A role for C3, in association with effector cells, in the nonspecific immunity occurring in the first hours after a primary S. mansoni infection is suggested.     

Schistosoma mansoni and Fasciola hepatica: Cross-resistance in mice

Cross-resistance in Schistosoma mansoni and Fasciola hepatica infections were studied in mice. A primary infection of S. mansoni, 7 to 28 days old, did not stimulate a significant level of resistance to heterologous challenge with F. hepatica. In contrast, in older S. mansoni infections (54–65 days old) there was a significant level of resistance to a challenge with F. hepatica. The F. hepatica worm burden was reduced by 34.0 to 72.5% in separate experiments. Challenge infection with F. hepatica did not influence the number of S. mansoni in primary infections. No heterologous resistance to S. mansoni was found in mice with 7- and 23-day-old F. hepatica infections. However, primary infections with F. hepatica, 28, 32, 42, and 50 days old, conferred significant resistance to a heterologous challenge with S. mansoni. The established schistosome worm burden was reduced by 41.5 to 50.4%. In no case was the primary F. hepatica burden reciprocally influenced by challenge infection with S. mansoni.     

Interactions between eosinophils and antibodies: In vivo protective role against rat schistosomiasis

An original protocol of cell transfer from Schistosoma mansoni-infected rats to normal recipient rats is used to investigate the protective role of phagocytic cell populations, described as effector cells in vitro, against a challenge infection with S. mansoni. Nonadherent, eosinophil-enriched and -adherent, macrophage-rich cell preparations, injected via intradermal and subcutaneous routes at the precise site of exposure to cercariae, were able to significantly protect the recipient rats. The time-course study of this protective effect according to the time after infection of donor rats revealed that eosinophils were the major cell population involved in the early phase of infection (4 to 5 weeks), whereas macrophages could also be incriminated thereafter. A rosette assay using anti-immunoglobulin-coated erythrocytes indicated a sequence of the various antibody isotypes under study (IgG₁, IgG_2a, IgE) on the eosinophil surface, during the course of infection. As previously shown in vitro, cytophilic antibodies seemed to participate in the protective effect of eosinophils, since eosinophil-enriched cells from normal rats, sensitized in vitro with immune complexes present in infected rat serum, could also confer significant protection. These observations establish therefore the relevance between our previous in vitro studies and rat resistance to a challenge infection with S. mansoni, underlining the major role played by the interaction between antibodies and phagocytic cells (eosinophils and macrophages).     

Schistosoma mansoni: circulating antigens and immune complexes in infected mice.

Circulating schistosome antigens (CSA) and circulating immune complexes (CIC) were investigated during the course of Schistosoma mansoni infection in mice. The radioimmunoprecipitation-polyethylene glycol (PEG) assay (RIPEGA) with [¹²⁵I]anti-S. mansoni antibodies or [¹²⁵I] anti-antigen “4” antibodies detected, respectively, total CSA and antigen “4” in serum and in 3% polyethylene glycol-precipitated CIC from infected mice. Complement fixation test and [¹²⁵I] C_1q-binding test revealed, respectively, an anticomplementary activity and the presence of C_1q-binding CIC. All these substances appeared in infected mice at approximately the same period, i.e., between the 40th- and the 55th- day postinfection. No correlation was observed between the detection of anticomplementary active substances and C_1q-binding CIC. In contrast, a close relationship was noticed between CSA and complement-activating material during the course of the infection. This suggests that substances with anticomplementary activity in serum from infected mice could be one or various CSA. A close correlation was also observed between C_1q-binding CIC and free or “complexed” antigen “4.” This observation supports well the possibility that antigen “4” is one of the major complexed circulating antigen present in schistosomiasis. The immunoglobulins G₁, G_2a, M, and A were also characterized in 3% PEG-precipitated CIC from infected mice during the period in which we detected C_1q-binding CIC. The roles played by specific S. mansoni CIC in either schistosomal nephropathy or protective mechanisms to a challenge infection in mice are discussed.     

Ginger (Zingiber Officinale)-derived nanoparticles in Schistosoma mansoni infected mice: Hepatoprotective and enhancer of etiological treatment

BackgroundNanotechnology has been manufactured from medicinal plants to develop safe, and effective antischistosmal alternatives to replace today’s therapies. The aim of the study is to evaluate the prophylactic effect of ginger-derived nanoparticles (GNPs), and the therapeutic effect of ginger aqueous extract, and GNPs on Schistosoma mansoni (S. mansoni) infected mice compared to praziquantel (PZQ), and mefloquine (MFQ).Methodology/principal findingsEighty four mice, divided into nine different groups, were sacrificed at 6^th, 8^th, and 10^th week post-infection (PI), with assessment of parasitological, histopathological, and oxidative stress parameters, and scanning the worms by electron microscope. As a prophylactic drug, GNPs showed slight reduction in worm burden, egg density, and granuloma size and number. As a therapeutic drug, GNPs significantly reduced worm burden (59.9%), tissue egg load (64.9%), granuloma size, and number at 10^th week PI, and altered adult worm tegumental architecture, added to antioxidant effect. Interestingly, combination of GNPs with PZQ or MFQ gave almost similar or sometimes better curative effects as obtained with each drug separately. The highest therapeutic effect was obtained when ½ dose GNPs combined with ½ dose MFQ which achieved 100% reduction in both the total worm burden, and ova tissue density as early as the 6^th week PI, with absence of detected eggs or tissue granuloma, and preservation of liver architecture.Conclusions/significanceGNPs have a schistosomicidal, antioxidant, and hepatoprotective role. GNPs have a strong synergistic effect when combined with etiological treatments (PZQ or MFQ), and significantly reduced therapeutic doses by 50%, which may mitigate side effects and resistance to etiological drugs, a hypothesis requiring further research. We recommend extending this study to humans.     

Schistosomiasis mansoni, haematobia, and japonica in hamsters: liver granuloma measurements

Differences in the granulomatous response of hamsters infected with Schistosoma mansoni, Schistosoma haematobium, or Schistosoma japonicum were studied by measuring granulomas formed around eggs in the livers at 1, 3, 5, 11, and 19 week intervals after patency of the infections. For each species, the mean diameters of both granulomas containing only 1 egg and granulomas selected at random were determined. The mean volume of single egg granulomas in S. mansoni-infected hamsters was greater than in those with other species at all time intervals studied. The decrease in single egg granuloma size with time occurred more gradually in S. mansoni infections. The mean volume of granulomas measured at random was greatest in S. japoracum-infected animals at 1, 3, and 11 weeks after patency; was greatest in S. haematobium-iufected. hamsters at 5 and 19 weeks; and was least in S. mansoni-infected hamsters at all time periods. During the 19 week period following patency, the mean volume of randomly measured granulomas increased with time in S. haematobium infections, decreased gradually in S. mansoni infections, and decreased markedly in S. japonicum infections. Multi-egg granulomas represented 2–6% of all granulomas measured in S. mansoni infections, 38–68% in S. haematobium infections, and 20–53% in S. japonicum infections. An estimated proportion of the liver occupied by granulomas, i.e., a lesion-to-tissue ratio, was computed. There was no consistent difference in this ratio among the 3 species when the data were grouped in comparable intervals of mean number of eggs per g of liver. The lesion-to-tissue ratio increased with increasing numbers of eggs per g of liver. The host response of hamsters to these 3 species of schistosomes differed markedly even at comparable levels of eggs per g of liver. This study provides further evidence of an intrinsic qualitative difference in the eggs of the 3 species. The species of eggs present in tissues apparently has greater influence on the host response than does the quantity of eggs present.     

Increased immunogenicity and protection of recombinant Sm14 antigens by heat-killed Cutibacterium acnes in BALB/c mice infected with Schistosoma mansoni

After many years of the excessive use of praziquantel against Schistosoma mansoni (S. mansoni), it has already led to the development of drug resistance. While schistosomiasis is still affecting millions of people every year, vaccination may be one realistic alternative way to control the disease. Currently, S. mansoni 14-kDa fatty acid-binding protein (Sm14) has shown promising results as a vaccine antigen. Yet, the use of an adjuvant may be necessary to further increase the effectiveness of the vaccine. Herein, we investigated the potential of using heat-killed Cutibacterium acnes (C. acnes) as an adjuvant for recombinant Sm14 (rSm14). Immunization of mice with C. acnes-adjuvanted rSm14 showed increased humoral immune responses, compared with mice immunized with rSm14 alone. Additionally, C. acnes-adjuvanted rSm14 vaccination provided higher protection to mice against S. mansoni infection and liver injuries. These results suggest that C. acnes increases the immunogenicity of rSm14, which leads to better protection against S. mansoni infection. Therefore, heat-killed C. acnes may be a promising adjuvant to use with rSm14.     

Biomphalaria alexandrina in Egypt: Past, present and future

The African species of Biomphalaria appeared as a result of the relatively recent west-to-east trans-Atlantic dispersal of the Biomphalaria glabrata-like taxon. In Egypt, Biomphalaria alexandrina is the intermediate host for Schistosoma mansoni. Biomphalaria alexandrina originated in the area between Alexandria and Rosetta and has historically been confined to the Nile Delta. Schistosoma mansoni reached Egypt via infected slaves and baboons from the Land of Punt through migrations that occurred as early as the Vth Dynasty. The suggestion of the presence of Schistosoma mansoni infection in Lower Egypt during Pharaonic times is discussed despite the fact that that there is no evidence of such infection in Egyptian mummies. It is only recently that Biomphalaria alexandrina colonized the Egyptian Nile from the Delta to Lake Nasser. This change was likely due to the construction of huge water projects, the development of new water resources essential for land reclamation projects and the movement of refugees from the Suez Canal zone to the Delta and vice versa. The situation with respect to Biomphalaria in Egypt has become complicated in recent years by the detection of Biomphalaria glabrata and a hybrid between both species; however, follow-up studies have demonstrated the disappearance of such species within Egypt. The National Schistosoma Control Program has made great strides with respect to the eradication of schistosoma; however, there has unfortunately been a reemergence of Schistosoma mansoni resistant to praziquantel. There are numerous factors that may influence the prevalence of snails in Egypt, including the construction of water projects, the increase in reclaimed areas, global climate change and pollution. Thus, continued field studies in addition to the cooperation of several scientists are needed to obtain an accurate representation of the status of this species. In addition, the determination of the genome sequence for Biomphalaria alexandrina and the use of modern technology will allow for the study of the host–parasite relationship at a molecular level.     

Schistosoma mansoni Infection in Ugandan Men Is Associated with Increased Abundance and Function of HIV Target Cells in Blood,but Not the Foreskin: A Cross-sectional Study

Background Schistosoma mansoni infection has been associated with an increased HIV prevalence in humans and SHIV incidence in primate models. We hypothesized that immune activation from this gastrointestinal mucosa infection would increase highly HIV-susceptible CD4 T cell subsets in the blood and the foreskin through common mucosal homing.Conclusions/Significance S. mansoni infection was associated with an increased frequency of highly HIV-susceptible Th1, Th17 and Th22 cell subsets in the blood, but these T cell immune differences did not extend to the foreskin. S. mansoni induced changes in T cell immunology mediated through the common mucosal immune system are not likely to increase HIV susceptibility in the foreskin.     

Schistosoma co-infection protects against brain pathology but does not prevent severe disease and death in a murine model of cerebral malaria

Co-infections of helminths and malaria parasites are common in human populations in most endemic areas. It has been suggested that concomitant helminth infections inhibit the control of malaria parasitemia but down-modulate severe malarial disease. We tested this hypothesis using a murine co-infection model of schistosomiasis and cerebral malaria. C57BL/6 mice were infected with Schistosoma mansoni and 8-9 weeks later, when Schistosoma infection was patent, mice were co-infected with Plasmodium berghei ANKA strain. We found that a concomitant Schistosoma infection increased parasitemia at the beginning of the P. berghei infection. It did not protect against P. berghei-induced weight loss and hypothermia, and P. berghei-mono-infected as well as S. mansoni-P. berghei-co-infected animals showed a high case fatality between days 6 and 8 of malarial infection. However, co-infection significantly reduced P. berghei-induced brain pathology. Over 40% of the S. mansoni-P. berghei-co-infected animals that died during this period were completely protected against haemorrhaging, plugging of blood vessels and infiltration, indicating that mortality in these animals was not related to cerebral disease. Schistosoma mansoni-P. berghei-co-infected mice had elevated plasma concentrations of IL-5 and IL-13 and on day 6 lower levels of IFN-γ, IL-10, monocyte chemoattractant protein-1 (MCP-1) and monokine induced by IFN-γ (MIG) than P. berghei-mono-infected mice. We conclude that in P. berghei infections, disease and early death are caused by distinct pathogenic mechanisms, which develop in parallel and are differentially influenced by the immune response to S. mansoni. This might explain why, in co-infected mice, death could be induced in the absence of brain pathology.     

Establishment of a continuous cell line from fibrotic schistosomal granulomas in mice livers

Summary A continuous murine cell line (GRX) was obtained from fibrotic granulomas induced in C3H/HeN mice liver by experimental infection withSchistosoma mansoni. This anchorage-dependent line produces composite connective tissue/extracellular matrix, displays morphological characteristics of myofibroblasts, and can, under appropriate conditions, accumulate fat droplets. GRX cells produce viral particles of retrovirus type. We consider GRX cell line to be representative of liver connective tissue cells, responsible for fibroplasia in liver fibrotic and granulomatous reactions. This research was supported by Centre National de la Recherche Scientifique, France; Financiadora de Estudos e Projetos (FINEP), Brasil; and Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq), Brasil.     

Adoptive suppression of granuloma formation by T lymphocytes and by lymphoid cells sensitive to cyclophosphamide.

Egg-induced granulomas formed in mice with chronic Schistosoma mansoni infection are smaller than those which develop during early (8-week) infection. Adoptive transfer of spleen cells from chronically infected mice (15–25 week), which displayed modulated granulomas, to 6-week-infected recipients effectively suppressed active granuloma formation in the recipients by 8 weeks after infection. Pretreatment of these suppressive spleen cells with anti-Thy 1.2 serum and complement eliminated their suppressive capacity. Administration of cyclophosphamide (CY) (20 mg/kg, 3 times/week for 3 weeks) to 12- to 15-week-infected mice reversed modulation of granuloma formation resulting in larger granulomas at 15 weeks. This abrogation of suppression was reflected in the spleens of the CY-treated mice, as seen by the inability of their spleen cells to adoptively transfer suppression to 6-week-infected mice. This regimen of CY treatment did not significantly alter anti-schistosome egg antigen hemagglutinating antibody titers. It is reasoned that the modulation of granuloma formation observed during chronic schistosomiasis mansoni is in part dependent upon a T lymphocyte and a CY-sensitive spleen cell.     

Schistosoma mansoni and Fasciola hepatica: Cross-resistance in mice with single-sex schistosome infections

Primary Schistosoma mansoni single-sex infections in mice, i.e., either male only or female only, did not stimulate any detectable level of heterologous resistance to challenge with Fasciola hepatica after 22 to 76 days, while statistically significant resistance to a challenge with F. hepatica was demonstrated in the presence of patent mixed-sex S. mansoni infections. Simultaneous infections with S. mansoni and F. hepatica induced a statistically significant reduction in the number of schisto-some worms established, i.e., the burden being reduced by 40.1 and 43.9%, respectively. There was no reduction of the F. hepatica worm burden. Similar features could be observed with a time interval of 48 hr between the S. mansoni infection and the F. hepatica challenge, i.e., the schistosome burden being reduced by 34.2 and 45.6%, respectively. Furthermore, simultaneous infections with S. mansoni and F. hepatica induced a statistically significant reduction of the egg production capacity per paired female schistosome worm as compared with that of the S. mansoni control group. Tissue egg counts of the various intestinal sections were reduced by 92.8–99.6%.     

Studies with tryptophan metabolites in vitro. Kynurenine metabolism in kidneys of mice infested with Schistosoma mansoni

The conversion in vitro of kynurenine into kynurenic acid and anthranilic acid in both normal kidneys and those obtained from mice infested with Schistosoma mansoni was investigated. Normal mouse kidneys seem to possess an excess of functional pyridoxal phosphate over those obtained from infested mice. Kynureninase and kynurenine transaminase in the latter kidneys are more easily inhibited by deoxypyridoxal phosphate and tartar emetic, indicating low stores of active pyridoxal phosphate. The possible implication of these findings in relation to the role of the kidneys in producing abnormal patterns of tryptophan metabolism and possibly contributing to the production of bladder tumours in bilharzial patients is discussed.