Immunobiology 215 (2010) 1011

Congenital exposure to Schistosoma mafuture immune response and the disease

Ahmad A. Othmana,, Zeinab S. Shoheiba, Em

a

identication of activated hepatic stellate cells (HSCs) using antibody against glial brillary acidic protein (GFAP).

et al. 2006). The principal events precipitating chronicmorbidity during infection with Schistosoma mansoni(S. mansoni) develop as a result of schistosome eggs that

ARTICLE IN PRESS

infection; PBS, phosphate buffered saline; RT-PCR, reverse tran-

scription polymerase chain reaction; TGF-b, transforming growthfactor beta; S. mansoni, Schistosoma mansoni.Corresponding author at: Parasitology Department, Tanta Facultylodge in the liver, gut, and other organs causinggranulomatous inammation that ends in brosis and

0171-2985/$ - see front matter r 2009 Elsevier GmbH. All rights reserved.

doi:10.1016/j.imbio.2009.04.004

of Medicine, Tanta, Egypt. Fax: +20 2 40 3407734.

E-mail address: ahmed_ali44@hotmail.com (A.A. Othman).In conclusion, congenital exposure to S. mansoni seems to ameliorate the immunopathological changes in futurepostnatal infections.r 2009 Elsevier GmbH. All rights reserved.

Keywords: Congenital exposure; Cytokines; GFAP; Hepatic stellate cells; Immune response; Liver brosis; Schistosoma mansoni

Introduction

Schistosomiasis is a water-borne parasitic disease thatplagues many tropical and subtropical regions all overthe world, aficting over 200 million people (Gryseels

Abbreviations: BSA, bovine serum albumin; GFAP, glial brillary

acidic protein; HRP, horseradish peroxidase; HSCs, hepatic stellate

cells; IL-12, interleukin-12; MoAb, monoclonal antibody; p.i., post-bDepartment of Pathology, Faculty of Medicine, Tanta University, Tanta, EgyptcDepartment of Medical Parasitology, Faculty of Medicine, Suez Canal University, Ismailia, Egypt

Received 19 February 2009; received in revised form 28 March 2009; accepted 1 April 2009

Abstract

Schistosomiasis mansoni is a widespread parasitic infection that may lead to several serious complications, such ashepatic periportal brosis and portal hypertension, mainly due to deposition of schistosome eggs in the tissues.However, people in endemic areas infrequently exhibit severe pathology and complications; this may be explained, inpart, by modulation of the disease in indigenous populations by in utero exposure to the parasite. This studyinvestigated the differences between mice born to Schistosoma mansoni-infected mothers and those born to non-infected ones in subsequent postnatal schistosomal infections. We found that the intensity of infection, evidenced byhepatic egg load, was much reduced in mice born to infected mothers. No difference was found as regards total andSchistosoma-specic immunoglobulin levels except for total IgG. The levels of gene expression of two regulatorycytokines, namely interleukin-12 (IL-12) and transforming growth factor beta (TGF-b) were found to be signicantlyincreased in prenatally exposed animals. Moreover, liver brosis was signicantly decreased in animals born to infectedmothers as revealed by histopathological and histochemical examination as well as by immunohistochemicalDepartment of Medical Parasitology, Faculty of Medicine, Tanta University, Tanta, Egypt12

nsoni infection: Impact on theoutcome

an M. Saiedb, Rasha H. Solimanc

www.elsevier.de/imbio

mouse 3 weeks post-infection (p.i.). Age-matched

ARTICLE IN PRESSunobitissue damage. Although these egg-induced granulomaseffectively sequester toxic egg products, they lead tosevere hepatic brosis and portal hypertension (Wilsonet al. 2007).Clinical observations in schistosomiasis-endemic

areas show that major complications of Schistosomainfection develop in approximately 412% of thepopulation, while the majority of infected people remainasymptomatic or exhibit mild non-specic symptoms(Tachon and Borojevic 1978). Also, indigenous peoplerarely manifest acute or toxaemic symptoms, whereasindividuals from non-endemic areas usually did (Caldaset al. 2008). One possible reason for the presence orabsence of severe pathology is prenatal exposure toschistosomiasis that modulates the future immuneresponse later in life (Malhotra et al. 1997). This notionhas been suggested by many authors and has beenexplored in experimental models (Camus et al. 1976;Montesano et al. 1999; King 2001).Fibrosis is the ultimate sequel of chronic hepatic

schistosomiasis. A characteristic type of periportalbrosis occurs, which may lead to presinusoidal portalhypertension and esophageal varices (Stavitsky 2004).Apparently, hepatic stellate cells (HSCs) play a majorrole in the process of brous tissue formation in theliver. They are responsible for synthesis of componentsof extra-cellular matrix and several types of collagen(Parola and Robino 2001). These cells reside in theDisses spaces of the liver sinusoids, and they constitutea minor cell type, roughly 58% of the total liver cells(Maubach et al. 2006). Following chronic injury, HSCsdifferentiate into myobroblast-like cells, acquiringcontractile and brogenic properties (Zhang et al.2006). For immunohistochemical identication ofHSCs, traditional antibodies against desmin (Yokoiet al. 1984), vimentin, and a-smooth muscle actin(Baroni et al. 1996) were used. More recently, glialbrillary acidic protein (GFAP), which is traditionallyused as a marker for astrocytes of the brain, wasestablished as a marker for HSCs (Lim et al. 2008).Fibrosis is a complex process that is poorly understood,but several immunological and non-immunologicaldeterminants are suggested, and the role of cytokinesin this context is central (Alves-Oliveira et al. 2006).Cytokines play a crucial role in the evolution and

regulation of Schistosoma-induced immunopathology.In murine models, immune responses to schistosomeantigens manifest a striking shift from a moderate Th1to a robust Th2-dominated response. Fibrosis and muchof the pathology is primarily mediated by Th2 while Th1responses are presumed to be protective (Reiman et al.2006). However, recent evidence suggests that maintain-ing a balanced and controlled Th1 or Th2 response iscritical in the case of schistosomiasis for protectivegranuloma formation without excessive pathology

A.A. Othman et al. / Imm102(Wilson et al. 2007). Transforming growth factor betauninfected female mice were also mated with male mice.After delivery, offspring were divided into two maingroups: group I included 20 offspring born to non-infected mothers (infected control group), and group IIincluded 20 offspring born to S. mansoni-infectedmothers. Ten mice were left uninfected and served asthe non-infected control for immunological parametersand immunohistochemical staining (group N). Groups Iand II were then infected subcutaneously withS. mansoni cercariae 60710 cercariae/animal. Miceof both groups were breast-fed, and were 8-week old atthe time of infection.At 12 weeks p.i., animals of groups I, II, and N were

sacriced. Serum samples were collected from mice ofeach group for detection of total and specic anti-(TGF-b) is secreted ubiquitously by many cell types,including activated T cells and activated macrophages(Miyazono et al. 1994). The bioactivity of TGF-b isoften bidirectional, depending on target cells or coex-isting mediators (Tsutsui and Kamiyama 1999). How-ever, its role in Schistosoma-induced inammation andbrosis remains controversial.The aim of the present study was to evaluate the effect

of experimental congenital exposure to schistosomiasismansoni on the subsequent postnatal infection. Weassessed the intensity of infection, extent of brosis, aswell as several immunological parameters in mice bornto Schistosoma-infected mothers in comparison to thoseborn to non-infected ones.

Materials and methods

Parasite

Laboratory bred Biomphalaria alexandrina snails werepurchased from the Schistosome Biological SupplyProgram, Theodore Bilharz Research Institute (Giza,Egypt). After exposure to light for at least 4 h,S. mansoni cercariae shed from the snails were used toinfect the experimental animals of the study.

Animals and experimental design

Laboratory bred and parasite free Swiss albino mice(2025 g in weight) were used in this study. Mice werepurchased from Theodore Bilharz Research Institute(Giza, Egypt) and were housed and infected inaccordance with the institutional guidelines. Eight weeksold (n 10) female mice were infected with 200cercariae of S. mansoni by subcutaneous injection asdescribed by Peters and Warren (1969). Each of 10female mice was individually mated with a normal male

ology 215 (2010) 101112Schistosoma antibodies. The liver of each mouse was

put in the incubator at 37 1C for 6 h. Each test tube was

substrate. Sera giving absorbance values higher than

R35-72) rat MoAb. Following addition of the test

ARTICLE IN PRESSunobiolosamples and standards and washing, HRP-conjugatedanti-mouse IgE (1 chain-specic, clone R35-118) ratMoAb and biotin-labeled anti-mouse polyclonal IgGwere added to each well. The reaction was readthe cut-off value ( mean absorbance of wells withserum from control mice+3 SD) were consideredpositive. Results were expressed in optical densities(ODs).

Estimation of total IgE and IgGCapture ELISA was used to determine the levels of

total IgG and IgE in mouse sera based on protocolsdetailed by the manufacturer (Pharmingen). Wells ofpolystyrene plates were coated with antimurine poly-clonal IgG and antimurine IgE (1 chain-specic, cloneshaken then 0.1ml of the digest was examined micro-scopically for counting S. mansoni eggs. The total eggcount in 1 g liver tissue was then calculated (Cheever1968).

Evaluation of humoral factors

Estimation of S. mansoni-specic IgE and IgGSoluble antigens from S. mansoni adult worms

(SAWA) were prepared as described (El Ridi et al.1993). In indirect ELISA, wells of polystyrene plates(Costar, Cambridge, MA, USA) were coated with500 ng soluble schistosome antigens, blocked with 1%bovine serum albumin (BSA) in 0.05M phosphatebuffered saline (PBS) pH 7.1, washed with PBS/0.05%Tween 20 (washing buffer), and incubated with 100 mlserum diluted in washing buffer. Specic, horseradishperoxidase (HRP)-labelled rat monoclonal antibody(MoAb) to mouse IgG and IgE were purchased fromPharmingen (San Diego, CA, USA), and used diluted1:1000 in washing buffer. HRP-labelled streptavidin(Boehringer-Mannheim, Mannheim, Germany) wasused diluted 1:5000. Reactivity was estimated spectro-photometrically at 492 nm after adding o-phenylenedia-mine (Sigma Chemical Co., St. Louis, MO, USA)immediately removed and divided into three portionsfor parasitological, immunological, histopathological,and immunohistochemical studies.

Parasitological study

Liver egg load was estimated in groups I and II. Onegram from each liver was weighed, and then put in a testtube containing 2ml of 5% KOH and left overnight atroom temperature. The second day, all test tubes were

A.A. Othman et al. / Immspectrophotometrically, and the serum levels of IgGrecommended by the manufacturer.

Estimation of levels of IL-12 and TGF-b mRNAexpression by semi-quantitative real-time PCR

Liver samples [10 randomly selected from groups Iand II, and 5 randomly selected from group N] weretaken and processed for RNA extraction (MagNA Purecompact Nucleic Acid isolation kit I, Roche Diagnos-tics, GmbH, Mannheim, Germany) according to themanufacturers recommendations. First strand cDNAwas synthesized from total RNA using TranscriptorFirst Strand cDNA Synthesis Kit (Roche, Germany)according to the manufacturers instructions.Determination of IL-12 and TGF-b mRNA expres-

sion by semi-quantitative reverse transcription polymer-ase chain reaction (RT-PCR) was carried out usingb-globin as the internal gene control. PCR was carriedout using Roche LightCycler real-time PCR system.Briey, in a 1.5ml reaction tube on ice, the followingcomponents were added in the same order they arementioned: 13 ml sterile H2O, PCR-grade, 2 ml Light-Cycler RT-PCR reaction mix SYBR Green I, 1.6 mlMgCl2 stock solution (nal concentration 5mM), 2 mlcytokine primer mix (nal concentration 0.5 mM)and 0.4 ml LightCycler RT-PCR enzyme mix, giving atotal volume of 19 ml. The components were mixedgently then pipetted into pre-cooled LightCycler capil-lary. One microliter of the cytokine RNA template wasadded giving a nal volume of 20 ml. The primersequences for IL-12 and TGF-b used in the study wereas follows:IL-12p40 (sense 50-GATGCTGGCCAGTACACC-30),

IL-12p40 (antisense 50-TCCAGCACGACCTCAATG-30),TGF-b (sense 50-CTACTACGCCAAGGAGGTC-30),TGF-b (antisense 50-TGACCCGCAGAGAGGCTA-T-30) (Techau et al. 2007). The optimal conditions forPCR amplication were: an initial incubation at 95 1Cfor 30 s, 45 cycles of denaturation at 95 1C, annealing at55 1C (10 s), and extension at 72 1C (13 s). The geneexpression for measured cytokines and b-globin wasmeasured in copies/ml. For each cytokine, the amountof RT-PCR product was normalized (as a ratio) to thevalues obtained for b-globin, as an internal standard foreach sample.

Histopathological, histochemical, andimmunohistochemical study

All the studied specimens were xed in 10% formalinand subsequently embedded in parafn, then submittedto

Haematoxylin and eosin (H&E) staining for histo-and IgE were calculated from a standard curve as

gy 215 (2010) 101112 103pathological examination. The composition of the

Statistical analysis

Data were presented as means7standard deviation.The probability of signicant differences among dualmeans of groups was determined by Students t-test.Fishers exact test was used for evaluating GFAPexpression. Differences were considered non-signicantwhen (P40.05), signicant (Po0.05), and highlysignicant (Po0.001). The statistical analyses wereprocessed according to the conventional procedures

increased in mice born to infected mothers (group II)

ARTICLE IN PRESSunobiology 215 (2010) 101112104with 0 indicating the absence of positive staining; 1indicating the presence of mild staining +; 2indicating the presence of moderate staining ++;3 indicating the presence of intense staining+++; and 4 indicating the presence of verydistinct brownish cytoplasmic reaction to GFAPwere considered positive. A semi-quantitative evalua-tion was performed in order to estimate the numberof GFAP-positive HSCs using scores from 0 to 4,granulomas was assessed and the granulomas wereclassied into three types (brous, cellular, andbrocellular) according to the predominant compo-nent (Costa-Silva et al. 2002).Massons trichrome staining to highlight broticchanges and to conrm the type of granuloma. Theprocedure of Massons trichrome stain was per-formed according to Jones (2002).Immunohistochemistry was done for demonstrationof activated hepatic stellate cells using antibodyagainst glial brillary acidic protein. Immunohisto-chemical staining was performed on 35 mm sectionsfrom randomly selected 10 parafn blocks from eachof the infected groups and 5 blocks from group N,using the UltraVision Detection System (Anti-Polyvalent, HRP/DAB Ready-to-Use, Cat. #TP-015-HD, Lab Vision, USA). The procedure of immunos-taining was conducted according to the manufac-turers protocol. Briey, sections were deparafnizedwith xylene and rehydrated with graded alcoholseries. Antigen retrieval was done by immersing thesections in 10mmol/l citrate buffer (pH 6.0) for10min at 100 1C in microwave. Endogenous perox-idase activity was blocked with hydrogen peroxideblock for 10min. After thorough washing of thesections with phosphate buffered saline, incubationwas done for 10min with Ultra V block to preventnon-specic background staining, followed by rinsingthe sections with PBS. Subsequently, an overnightincubation of the sections with antibody againstGFAP (Ab-4 rabbit polyclonal antibody, Cat. #RB-087-R7 Ready-to-Use, Lab Vision, USA) was doneat room temperature in a humidity chamber. Thesections were then washed with PBS and incubatedwith biotinylated goat anti-polyvalent (secondaryantibody) for 10min at room temperature followedby washing with PBS, then incubated with streptavi-din peroxidase solution for 10min at room tempera-ture, then rinsed with PBS. The reaction productswere visualized using 3-30-diamino-benzidine-tetra-hydrochloride (DAB), and the sections were thencounterstained with Mayers haematoxylin, dehy-drated in alcohol and mounted in DPX. Sectionsfrom the brain of a mouse were used as positivecontrols, while negative controls were prepared byomission of the primary antibody. Cells showing a

A.A. Othman et al. / Immintense staining ++++ (Gibelli et al. 2008).aPercent reduction was calculated according to the formula [(group Icompared to mice born to non-infected mothers (group I),and non-infected animals (group N), Po0.001.

Table 1. Liver egg count (mean7SD) recovered from miceborn to non-infected mothers (group I) and mice born to

infected mothers (group II).

Group Egg count Reduction (%)a P-value

Group I (n 20) 46807191.3 Group II (n 20) 28307412.5 39.5 o0.001

meangroup II mean)/group I mean] 100.using Statistical Program of Social Sciences (SPSS)software for windows, version 10.0.

Results

Hepatic egg load

Results of liver egg load are shown in Table 1. Therewas highly signicant reduction in the mean numbers ofliver egg count in mice born to infected mothers (groupII) compared to infected control mice (group I). Themean liver egg count in group I at 12 weeks p.i. was(46807191.3) compared to group II (28307412.5),Po0.001.

Antibody response

Results of antibody response 12 weeks p.i. aredemonstrated in Fig. 1. There were no signicantdifferences between groups I and II regarding totalIgE, Schistosoma-IgE and Schistosoma-IgG. On theother hand, highly signicant increase in total IgG levelwas observed in group II compared to group I,Po0.001.

Cytokine mRNA expression

Fig. 2 shows levels of mRNA expression of themeasured cytokines. In the liver homogenates, levels ofIL-12 and TGF-b mRNA expression were signicantlyPo0.001 (signicant reduction).

ARTICLE IN PRESSunobiTotal IgG

0

2

4

6

8

10

12

14

mg/

dl

Group NGroup IGroup II

Total IgE

3

4

5

/ml

Group NGroup IGroup II

A.A. Othman et al. / ImmHistopathological and histochemical ndings

Histopathological examination revealed the presenceof granulomatous reactions within the portal tracts.Each granuloma was formed around a Schistosomaovum and was composed of cellular collection ofeosinophils, histiocytes, lymphocytes, and plasma cells.Peripheral broblasts with variable amounts of collagendeposition were seen in brocellular and brous types.Percentages of the different types of granulomas in thestudied groups are illustrated in Fig. 3. In group I, thebrous granulomas were the most prevalent type(Fig. 4A), whereas in group II, the brocellular typepredominated (Fig. 4B). The brotic changes within thegranulomas were highlighted by the Massons trichromestain (Fig. 4C and D).

0

1

2IU

00.10.20.30.40.50.60.70.8

abso

rban

ce (4

92nm

) Group I Group II

Sch- IgG Sch- IgE

Fig. 1. Values of total IgG, total IgE, Schistosoma-IgG (Sch-

IgG), and Schistosoma-IgE (Sch-IgE) in infected control mice

(group I) compared to mice born to infected mothers (group

II) expressed in means7SD. Signicant elevation in total IgGlevel is observed in group II compared to group I (n 20).Po0.001.IL-12

00.5

11.5

22.5

33.5

4Group NGroup IGroup II

TGF-

1

2

3

4

5Group N

Group I

Group II

ology 215 (2010) 101112 105Immunohistochemical evaluation of GFAPexpression

In the normal control group (group N), very fewscattered HSCs showing faint positivity for GFAP weredetected. In both infected groups, GFAP-positive HSCsappeared in two locations: (a) sinusoidal (parenchymal)HSCs, which appeared as thin irregular positive bandsalong the sinusoids with a dislocated nucleus and (b)mesenchymal HSCs located in the hepatic lobule closeto the portal tracts, within the portal tracts, and withinthe granulomas. Immunohistochemical localization ofGFAP in both groups revealed that group I showedhigher GFAP expression in comparison to group II bothin sinusoidal (Fig. 5A and B) and mesenchymal (Fig. 5Cand D) HSCs, indicating a more active and moreextensive brotic process in group I compared to group II.GFAP expression in the infected groups is illustrated inTable 2. The predominant grades of GFAP expressionin group I were grades 3 and 4, while in group II thepredominant grades were grades 1 and 2. The differencebetween both groups was statistically signicant(Po0.05).

0

Fig. 2. Cytokine mRNA expression levels in liver tissues 12

weeks p.i. Vertical bars represent the mean (7SD) of theseresults for each group (group N, n 5, groups I and II,n 10). Signicant increase in levels of IL-12 and TGF-bmRNA was found in mice born to infected mothers (group II),

Po0.001.

ARTICLE IN PRESS

0%

unobiGroup I (infected control group)

8.20%

29.4

A.A. Othman et al. / Imm106Discussion

Schistosomiasis remains a major cause of morbidity intropical and subtropical countries (Engels et al. 2002). Itis quite intriguing that in endemic areas few people

62.40%

Cellular fibrocellular fibrous

Fig. 3. Comparison between group I (infected control) and group

different types of granulomas. Group I granulomas are mainly of

predominate.

Fig. 4. Photomicrographs of schistosomal hepatic granulomas: (A) a

most of them are of the brous variety arrows in infected contro

prenatally exposed mice group II. The granulomas are brocell

granuloma in group I (Massons trichrome 400), and (D) littletrichrome 400).Group II (born to infected mothers)

32.30%27.30%

ology 215 (2010) 101112develop severe pathology and sequelae, while themajority show asymptomatic or mild pathology. In-tensity and duration of the infection are majordeterminants, but other factors are also involved. Theseinclude genetic background of the host, nutritional

40.40%

Cellular fibrocellular fibrous

II (born to infected mothers) regarding the percentages of the

the brous type while in group II brocellular granulomas

large number of granulomas formed around Schistosoma ova,

l group I (H&E 100), (B) fewer granulomas arrows inular (H&E 100), (C) extensive brotic changes within thebrotic changes within the granuloma in group II (Massons

ARTICLE IN PRESSunobiA.A. Othman et al. / Immstatus, parasite strain differences, and frequency ofinfection. Maternal infection status in that offspring ofthe infected mothers may be primed to mount amodulated type of response at rst infection has beenproposed by many authors in order to explain theindividual differences (Butterworth and Thomas 1999).

Fig. 5. Hepatic immunohistochemical staining for GFAP: (A) sect

expression located in sinusoidal HSCs arrow (immunoperoxidase G

II showing grade 2 GFAP expression located in sinusoidal HSCs

group I showing grade 3 GFAP expression located in both mesenchy

400), and (D) section from group II showing grade 2 G(immunoperoxidase GFAP 400).

Table 2. GFAP expression in the infected groups.

Groups GFAP expression

Grade 0

GFAP staining

Grade 1

GFAP staining (+)

Gr

GF

N % N % N

Group I (n 10) 0 0 1 10 2Group II (n 10) 0 0 5 50 4

There is a signicant difference between both groups, Po0.05.ology 215 (2010) 101112 107Epidemiology provides some evidence: individuals whomove from non-endemic to endemic areas, such asmigrants, travelers, or military personnel, often expressmore severe acute and chronic schistosomiasis com-pared to those who grew up within endemic areas (Nashet al. 1982).

ion from infected control group I showing grade 4 GFAP

FAP 400), (B) section from prenatally exposed mice grouparrow (immunoperoxidase GFAP 400), (C) section frommal arrow and sinusoidal HSCs (immunoperoxidase GFAP

FAP expression located in mesenchymal HSCs arrow

ade 2

AP staining (++)

Grade 3

GFAP staining

(+++)

Grade 4

GFAP staining

(++++)

% N % N %

20 4 40 3 30

40 1 10 0 0

ARTICLE IN PRESSunobiIn the present study, mice born to infected mothersshowed signicant reduction in liver egg count com-pared to infected control animals. Reduction in adultworm count may provide an explanation for thesendings. Attallah et al. (2006) demonstrated that adultworm count was signicantly reduced in the offspring ofSchistosoma-infected mothers compared to mice born tonon-infected ones, but no explanation was offered. Weassume that the situation is perhaps similar to that ofconcomitant immunity in which continuous antigenicstimulation (by the presence of some adult worms)stimulates protective immune response against furtherinfections. Early stimulation of the immune system by inutero exposure to schistosomiasis may, therefore,provide quite strong protective immunity against initialpostnatal infections. In sum, congenital exposure toSchistosoma infection seems to reduce the intensity ofinfection in subsequent postnatal exposure.As regards the humoral immune response, no

signicant differences were noted in the levels ofSchistosoma-specic IgG and IgE, as well as total IgEbetween mice born to infected mothers and infectedcontrol animals. In contrast, total IgG level wassignicantly increased in prenatally exposed mice.Attallah et al. (2006) found that Schistosoma-specicIgG levels were lower in prenatally exposed micecompared to control. However, IgG levels were mea-sured earlier in the course of infection than in our study.The increase in total IgG levels in our study should beinterpreted with caution, for different classes ofIgG serve different functions: whereas IgG2 class isconsidered to confer immunity (Dunne et al. 1995;Noya et al. 1995), IgG4 are blocking antibodiesthat may block IgE-mediated effects (Noya et al. 1995;King 2001), and may play a role in immunologicaltolerance in prenatally sensitized individuals (Caldaset al. 2008). Although IgE levels are correlated withresistance to infection especially after treatment (Sattiet al. 1996), no difference was noted in our studybetween both infected groups as regards total andspecic IgE levels.Interleukin-12 (IL-12) is a heterodimer composed of

two disulde-linked polypeptide chains that are pro-ducts of two distinct genes. It plays a pivotal role inpromoting cell-mediated immune response. It promotesthe differentiation of uncommitted T helper cells to theTh1 subset (Trinchieri and Scott 1999). A major actionof IL-12 is its ability to induce the production of IFN-g,doing so synergistically in combination with IL-2. Themajor producers of IL-12 are the dendritic cells andmacrophages (Gately et al. 1998).In our study, expression levels of IL-12 were

signicantly increased in mice born to infected motherscompared to those born to non-infected ones. Few dataare available regarding the role of IL-12 in schistoso-

A.A. Othman et al. / Imm108miasis, but all point out a benecial effect (Wilson et al.2007). Vaccination of mice with parasite eggs and IL-12inhibits the Th1 to Th2 shift and results in ameliorationof hepatosplenic pathology following infection (Wynnet al. 1995). Similarly, mice lacking IL-12 develop avigorous Th2 response that is detrimental during thechronic phase of infection and display signicantmortality by 1215 weeks post-infection (Hoffmannet al. 2000). The high levels of IL-12 may account in partfor the ameliorated liver pathology and brosis noted inour experiment.Transforming growth factor-b (TGF-b) is a pleio-

tropic cytokine that is involved in a number ofbiological processes. It induces collagen and bronectinproduction by broblasts. Further, it inhibits manyproducts of lymphocyte function including T-cell pro-liferation, and plays a critical role in T-cell homeostasis(Gorelik and Flavell 2000). It is produced by specialsubset of CD4+ T helper cells, sometimes called Th3(Chatila 2005). Its role in Schistosoma-induced pathol-ogy and brosis is unclear especially in humans. Someauthors believe that during hepatic brogenesis, TGF-bhas a pivotal role in initiation and progression ofdifferentiation of HSCs into myobroblasts (Gressnerand Weiskirchen 2006; Chu et al. 2007). On the otherhand, de Jesus et al. (2004) did not nd differences inTGF-b levels in patients with different degrees ofhepatic brosis. Others suggested that TGF-b is aregulatory cytokine which provides an effective mechan-ism of control of the progression of brosis inassociation with IL-10 (Kitani et al. 2003; Hesse et al.2004). Moreover, an experimental study has demon-strated that brosis and much of the pathology ofschistosomiasis is mediated by Th2 cytokines especiallyIL-13, and not by TGF-b (Kaviratne et al. 2004).We found that TGF-b mRNA expression levels were

signicantly higher in mice born to infected motherscompared to infected control. This may account forreduced pathology and brosis observed in our study,and this is probably related to its inhibitory effect onT-cell proliferation. The brogenic activity of TGF-bmight be offset by its immunoregulatory function.Furthermore, IFN-g suppresses the brogenic activityof TGF-b by down-regulating the expression of itsreceptors (Zhang et al. 2004). Thus, increased IL-12 mayhave attenuated the brogenesis stimulated by TGF-b.Presumably, other regulatory mechanisms may beinvolved, such as CD4+CD25+ T regulatory cells,since these cells increase in experimental Schistosoma-induced hepatic granulomas from 12% at 8 weeks to88% at 16 weeks during the course of infection, and theyameliorate liver pathology in experimentally infectedmice (Singh et al. 2005). However, this assumptionremains to be tested.Fibrosis is the main culprit in Schistosoma-induced

pathology. The hepatic stellate cells (HSCs) play a

ology 215 (2010) 101112major role in this process, and there has recently been

ARTICLE IN PRESSunobiunprecedented interest in this cell (and its activatedform) as a prognostic indicator of progression of liverbrosis, as well as a potential target for therapeuticintervention (Moreira 2007). In addition, multiplestudies have demonstrated a positive correlation be-tween the severity of hepatic brosis and the number ofactivated stellate cells present in the liver (Russo et al.2005). However, the different stimuli that initiate andperpetuate HSC activation in chronic liver diseases arepoorly understood. Remarkably, HSCs affect adverselythe hepatic microcirculation. When activated, theytransform into myobroblasts that contract aroundthe hepatic sinusoids, increasing the vascular resistanceand contributing to portal hypertension (Friedman2000).In our study, histopathological and histochemical

examination revealed that most granulomas werebrocellular in prenatally exposed offspring, whereasmost were brous in infected control group. In addition,cellular granulomas were more abundant in prenatallyexposed mice. Evident reduction in the activity of HSCswas observed in mice born to infected motherscompared to infected control group as demonstratedby immunohistochemical staining for GFAP. Previousanimal studies did demonstrate smaller-sized granulo-mas in offspring of infected mothers compared tocontrol (Hang et al. 1974; Montesano et al. 1999;Attallah et al. 2006), but this is the rst time, to the bestof our knowledge, to demonstrate the direct effect ofmaternal infection on HSC activity in schistosomiasis.The reduced size of granulomas observed by manyauthors and in our experiment (data not shown), and thereduction in brosis in congenitally exposed mice maybe attributed to attenuated Th2 response. The latter maybe due to, at least in part, an increase in counter-regulatory cytokines such as IL-12 and TGF-b.Furthermore, recent research stresses the role of freeoxygen radicals as activators of HSCs (Loguercio andFederico 2003). As the overall liver inammation wasexpected to decrease in congenitally exposed micedue to decreased egg deposition and granuloma forma-tion, less free oxygen radicals would be produced withattenuated stimulation of HSCs compared to infectedcontrol mice.Perinatal immunological sensitization may occur by

transplacental and/or transmammary passage of schis-tosome antigens (Carlier et al. 1980), anti-idiotypicantibodies (Montesano et al. 1999), or immune com-plexes (Uhr et al. 1957). Attallah et al. (2006) havealready detected Schistosoma antigens in the tissues ofoffspring born to infected mothers particularly in theliver and kidneys. In addition, several authors suggestedthat cellular hypersensitivity to S. mansoni antigen couldin part be transmitted in milk of infected mothers totheir infants (Eissa et al. 1989; Santoro et al. 1977).

A.A. Othman et al. / ImmPresumably, exposure to parasite antigen very early inthe development of the immune system results inimmunological tolerance. The antigens can be no longerrecognized as totally foreign. On initial postnatalexposure, the primed immune system may be moreprone to develop less striking shift from Th1 to Th2responses as seen in truly immunologically naveindividuals (Caldas et al. 2008). A more balancedT-cell response may be responsible for improvedimmunopathological processes and perhaps better hostparasite interaction in indigenous populations.These results can be relevant to humans since many

children are indeed born to infected mothers in endemicareas. Unfortunately, no human studies have directlyshown that in utero exposure to schistosomiasis affectsthe subsequent outcome of the disease. However, vastamount of empirical evidence exists. For example,children in Schistosoma-endemic areas rarely manifestacute manifestations such as acute dermatitis orkatayama fever. These children are born to motherswho had schistosomiasis during their pregnancy, and areprobably already primed for many anti-schistosomeresponses at the time of their rst exposure to cercariae(Caldas et al. 2008). Interestingly, congenital transmis-sion of Schistosoma japonicum to the offspring whenthe mother acquires the infection during pregnancy was conrmed in pigs (Willingham et al. 1999), and inhumans (Kikuchi 1957). If this proves to be true forhuman schistosomiasis mansoni, this will add to thecomplexity of the situation, and might provide astronger background for immunomodulation in subse-quent infections.Not surprisingly, the inuence of in utero exposure to

infections has been suggested in other chronic parasiticdiseases. For example, in laria-endemic areas fetusesare exposed to substantial amount of larial antigen.Exposure to antigens at this stage of developmentpromotes tolerance by the immune system (Hightoweret al. 1993). Thus, a child born to a microlaremicmother is 2.9 times more likely to become microlaremicthan a child born to an amicrolaremic mother.Likewise, many individuals in endemic areas areasymptomatic microlaremics (Kumar 1997). The samepattern is found in malaria-endemic areas wherenon-endemic individuals react differently than indigen-ous people (Rasheed et al. 1995). Moreover, transpla-cental transfer of Opisthorchis felineus antigens in thehyperendemic foci of infection does not prevent super-infection, but does prevent the acute phase of diseaseand signicantly mitigates the organic lesions in thechronic phase in spite of a very high intensity ofinfection (Ozeretskovskaia 2000). One recent studydemonstrated that experimental maternal infectionwith Opisthorchis viverrini affected worm fecundityand worm load in acquired postnatal infections ofthe offspring with the same parasite (Intapan and

ology 215 (2010) 101112 109Maleewong 2006).

109117.

Camus, D., Carlier, Y., Bina, J.C., Borojevic, R., Prata, A.,

ARTICLE IN PRESSunobiCapron, A., 1976. Sensitization to Schistosoma mansoni

antigen in uninfected children born to infected mothers.

J. Infect. Dis. 134, 405408.

Carlier, Y., Nzeyimana, H., Bout, D., Capron, A., 1980.

Evaluation of circulating antigens by a sandwich radio-

immunoassay, and of antibodies and immune complexes, in

Schistosoma mansoni infected African parturients and their

newborn children. Am. J. Trop. Med. Hyg. 29, 7481.

Chatila, T.A., 2005. Role of regulatory T cells in human

diseases. J. Allergy Clin. Immunol. 116, 949959.

Cheever, A.W., 1968. Conditions affecting the accuracy of

potassium hydroxide digestion in techniques for counting

S. mansoni eggs in tissues. Bull. World Health Organ. 39,

328331.

Chu, D., Luo, Q., Li, C., Gao, Y., Yu, L., Wei, W., Wu, Q.,In conclusion, prenatal exposure to S. mansoniinfection affects the immune response and the diseaseoutcome in the future postnatal infections; the intensityof the infection as well as the immunopathologicalchanges are moderated in congenitally exposed hosts.These ndings warrant further investigations regardingthe underlying mechanisms of immunomodulation hereand in other parasitic infections, and they may also beapplicable to other Th2-dominated diseases, such asallergy and bronchial asthma. Finally, these results maygive us insight for prevention and control strategies inschistosomiasis, and perhaps in other chronic infectiousdiseases as well.

References

Alves-Oliveira, L.F., Moreno, E.C., Gazzinelli, G., Martins-

Filho, A.O., Silveira, A.M.S., Gazzinelli, A., Malaquias,

L.C.C., LoVerde, P., Martins Leite, P., Correa-Oliveira, R.,

2006. Cytokine production associated with periportal

brosis during chronic schistosomiasis mansoni in humans.

Infect. Immun. 74, 12151221.

Attallah, A.M., Abbas, A.T., Dessouky, M.I., El-emshaty,

H.M., Elsheikha, H.M., 2006. Susceptibility of neonate

mice born to Schistosoma mansoni-infected and noninfected

mothers to subsequent S. mansoni infection. Parasitol. Res.

99, 137145.

Baroni, G.S., DAmbrosio, L., Curto, P., Casini, A., Mancini,

R., Jezequel, A.M., Benedetti, A., 1996. Interferon gamma

decreases hepatic stellate cell activation and extracellular

matrix deposition in rat liver brosis. Hepatology 23,

11891199.

Butterworth, A.E., Thomas, J.E.P., 1999. Schistosomiasis. In:

Weatherall, D.J., Ledingham, T.G.G., Warell, D.A. (Eds.),

Oxford Textbook of Medicine, third ed., vol. 1, Section 7.

Oxford University Press Inc., New York, pp. 970981.

Caldas, I.R., Campi-Azevedo, A.C., Alves-Oliveira, L.F.,

Silveira, A.M.S., Oliveira, R.C., Gazzinelli, G., 2008.

Human schistosomiasis mansoni: immune responses during

acute and chronic phases of the infection. Acta Trop. 108,

A.A. Othman et al. / Imm110Shen, J., 2007. Paeoniorin inhibits TGF-beta1-mediatedcollagen production by Schistosoma japonicum soluble egg

antigen in vitro. Parasitology 134, 16111621.

Costa-Silva, M., Rodrigues-Silva, R., Hulstijn, M., Neves, R.H.,

de Souza Panasco, M., Lenzi, H.L., Machado-Silva, J.R.,

2002. Natural Schistosoma mansoni infection in Nectomys

squamipes: histopathological and morphometric analysis in

comparison to experimentally infected N. squamipes and

C3H/He mice. Mem. Inst. Oswaldo Cruz 97, 129142.

de Jesus, A.R., Magalhaes, A., Miranda, D.G., Miranda,

R.G., Araujo, M.I., de Jesus, A.A., Silva, A., Santana,

L.B., Pearce, E., Carvalho, E.M., 2004. Association of type

2 cytokines with hepatic brosis in human schistosomiasis

mansoni infection. Infect. Immun. 72, 33913397.

Dunne, D.W., Hagan, P., Abath, F.G.C., 1995. Prospects for

immunological control of schistosomiasis. Lancet 345,

14881491.

Eissa, A.M., Saad, M.A., Abd-Elghaffar, A.K., El-Sharkaway,

I.M., Kamal, K.A., 1989. Transmission of lymphocyte

responsiveness to schistosomal antigens by breast feeding.

Trop. Geogr. Med. 41, 208212.

El Ridi, R., Abdel Tawab, N., Guirguis, N., 1993. Schistosoma

mansoni: identication and protective capacity of adult

worm antigens recognized by T lymphocytes of outbred

Swiss mice immunized with irradiated cercariae. Exp.

Parasitol. 76, 265277.

Engels, D., Chitsulo, L., Montresor, A., Savioli, L., 2002. The

global epidemiological situation of schistosomiasis and new

approaches to control and research. Acta Trop. 82, 139146.

Friedman, S.L., 2000. Molecular regulation of hepatic brosis,

an integrated cellular response to tissue injury. J. Biol.

Chem. 275, 22472250.

Gately, M.K., Renzetti, L.M., Magram, J., Stern, A.S.,

Adorini, L., Gubler, U., Presky, D.H., 1998. The inter-

leukin-12/interleukin-12 receptor system: role in normal

and pathological immune responses. Annu. Rev. Immunol.

16, 495521.

Gibelli, N.E.M., Tannuri, U., de Mello, E.S., 2008. Immuno-

histochemical studies of stellate cells in experimental

cholestasis in newborn and adult rats. Clinics 63, 689694.

Gorelik, L., Flavell, R.A., 2000. Abrogation of TGF-bsignaling in T cells leads to spontaneous T cell differentia-

tion and autoimmune disease. Immunity 12, 171181.

Gressner, A.M., Weiskirchen, R., 2006. Modern pathogenetic

concepts of liver brosis suggest stellate cells and TGF-b asmajor players and therapeutic targets. J. Cell. Mol. Med.

10, 7699.

Gryseels, B., Polman, K., Clerinx, J., Kestens, L., 2006.

Human schistosomiasis. Lancet 368, 11061118.

Hang, L.M., Boros, D.L., Warren, K.S., 1974. Induction of

immunological hyporesponsiveness to granulomatous hy-

persensitivity in Schistosoma mansoni infection. J. Infect.

Dis. 130, 515522.

Hesse, M., Piccirillo, C.A., Belkaid, Y., Prufer, J., Mentink-

Kane, M., Leusink, M., Cheever, A.W., Shevach, E.M.,

Wynn, T.A., 2004. The pathogenesis of schistosomiasis is

controlled by cooperating IL-10-producing innate effector

and regulatory T cells. J. Immunol. 172, 31573166.

Hightower, A.W., Lammie, P.J., Eberhard, M.L., 1993.

Maternal larial infection a persistent risk factor for

ology 215 (2010) 101112microlaraemia in offspring? Parasitol. Today 9, 418421.

ARTICLE IN PRESSunobiHoffmann, K.F., Cheever, A.W., Wynn, T.A., 2000. IL-10 and

the dangers of immune polarization: excessive type 1 and

type 2 cytokine responses induce distinct forms of lethal

immunopathology in murine schistosomiasis. J. Immunol.

164, 64066416.

Intapan, P.M., Maleewong, W., 2006. Opisthorchis viverrini:

inuence of maternal infection in hamsters on offspring

infected with homologous parasite and their IgG antibody

response. Exp. Parasitol. 113, 6774.

Jones, M.L., 2002. Connective tissues and stains. In: Bancroft,

J.D., Gamble, M. (Eds.), Theory and Practice of Histolo-

gical Techniques, fth ed. Churchill Livingstone, Edin-

burgh, pp. 139162 (Chapter 9).

Kaviratne, M., Hesse, M., Leusink, M., Cheever, A.W.,

Davies, S.J., McKerrow, J.H., Wakeeld, L.M., Letterio,

J.J., Wynn, T.A., 2004. IL-13 activates a mechanism of

tissue brosis that is completely TGF-beta independent. J.

Immunol. 173, 40204029.

Kikuchi, S., 1957. Studies on placental infection of Schistoso-

ma japonicum. Sogo Igaku 14, 537554.

King, C.L., 2001. Initiation and regulation of disease in

schistosomiasis. In: Mahmoud, A.F. (Ed.), Schistosomiasis.

Tropical Medicine: Science and Practice, vol. 3. Imperial

College Press, UK, pp. 213256.

Kitani, A., Fuss, I., Nakamura, K., Kumaki, T., Usui, T.,

Strober, W., 2003. Transforming growth factor (TGF)-b1-producing regulatory T cells induce Smad mediated

interleukin 10 secretion that facilitates coordinated im-

munoregulatory activity and amelioration of (TGF)-b1-mediated brosis. J. Exp. Med. 198, 11791188.

Kumar, A., 1997. Do offspring of larial infected mothers

have a greater risk of becoming microlaraemic? Acta

Trop. 64, 219223.

Lim, M.C., Maubach, G., Zhuo, L., 2008. Glial brillary

acidic protein splice variants in hepatic stellate cells

expression and regulation. Mol. Cells 25, 376384.

Loguercio, C., Federico, A., 2003. Oxidative stress in viral and

alcoholic hepatitis. Free Radical Biol. Med. 34, 110.

Malhotra, I., Ouma, J., Wamachi, A., Kioko, J., Mungai, P.,

Omollo, A., Elson, L., Koech, D., Kazura, J.W., King,

C.L., 1997. In utero exposure to helminth and mycobacter-

ial antigens generates cytokine responses similar to that

observed in adults. J. Clin. Invest. 99, 17591766.

Maubach, G., Lim,M.C.C., Zhang, C.Y., Zhuo, L., 2006. GFAP

promoter directs lacZ expression specically in a rat hepatic

stellate cell line. World J. Gastroenterol. 12, 723730.

Miyazono, K., Dijke, P.T., Ichijo, H., Heldin, H., 1994.

Receptors for transforming growth factor-b. Adv. Immu-nol. 55, 181220.

Montesano, M.A., Colley, D.G., Eloi-Santos, S., Freenan,

G.L., Secor, W.E., 1999. Neonatal idiotypic exposure alters

subsequent cytokine, pathology, and survival patterns in

experimental Schistosoma mansoni infections. J. Exp. Med.

189, 637645.

Moreira, R.K., 2007. Hepatic stellate cells and liver brosis.

Arch. Pathol. Lab. Med. 131, 17281734.

Nash, T.E., Cheever, A.W., Ottesen, E.A., Cook, J.A., 1982.

Schistosome infections in humans: perspectives and recent

ndings. In: NIH Conference. Ann. Intern. Med. 97,

A.A. Othman et al. / Imm740754.Noya, O., Fermin, Z., Alarcon de Noya, B., Losada, S.,Colmenares, C., Hermoso, T., 1995. Humoral immune

response of children with chronic schistosomiasis. Isotype

recognition of adult worm antigens. Parasite Immunol. 17,

319328.

Ozeretskovskaia, N.N., 2000. Organ pathology in chronic

tissue-dwelling helminthic infections: role of blood and

tissue eosinophilia, immunoglobulinemia E, G4, and

immune response-inducing factors. Med. Parazitol. (Mosk).

69, 914.

Parola, M., Robino, G., 2001. Oxidative stress-

related molecules and liver brosis. J. Hepatol. 35,

297306.

Peters, P.A., Warren, K.S., 1969. A rapid method of infecting

mice and other laboratory animals with S. mansoni:

subcutaneous injection. J. Parasitol. 55, 558.

Rasheed, F.N., Bulmer, J.N., De Francisco, A., Jawla,

M.F.B., Jakobsen, P.H., Jepson, A., Greenwood, B.M.,

1995. Relationships between maternal malaria and malarial

immune responses in mothers and neonates. Parasite

Immunol. 17, 110.

Reiman, R.M., Thompson, R.W., Feng, C.G., Hari, D.,

Knight, R., Cheever, A.W., Rosenberg, H.F., Wynn, T.A.,

2006. Interleukin-5 (IL-5) augments the progression of liver

brosis by regulating IL-13 activity. Infect. Immun. 74,

14711479.

Russo, M.W., Firpi, R.J., Nelson, D.R., Schoonhoven, R.,

Shrestha, R., Fried, M.W., 2005. Early hepatic stellate cell

activation is associated with advanced brosis after liver

transplantation in recipients with hepatitis C. Liver

Transplant. 11, 12351241.

Santoro, F., Borojevic, R., Bout, D., Tachon, P., Bina, J.C.,

Capron, A., 1977. Motherchild relationship in human

schistosomiasis mansoni. Am. J. Trop. Med. Hyg. 26,

11641168.

Satti, M.Z., Lind, P., Vennervald, B.J., Sulaiman, S.M.,

Daffalla, A.A., Ghalib, H.W., 1996. Specic immunoglo-

bulin measurements related to exposure and resistance to

Schistosoma mansoni infection in Sudanese canal cleaners.

Clin. Exp. Immunol. 106, 4554.

Singh, K.P., Gerard, H.C., Hudson, A.P., Reddy, T.R., Boros,

D.L., 2005. Retroviral Foxp3 gene transfer ameliorates

liver granuloma pathology in Schistosoma mansoni infected

mice. Immunology 114, 410417.

Stavitsky, A.B., 2004. Regulation of granulomatous inam-

mation in experimental models of schistosomiasis. Infect.

Immun. 72, 112.

Tachon, P., Borojevic, R., 1978. Motherchild relation in

human schistosomiasis mansoni: skin test and cord blood

reactivity to schistosomal antigens. Trans. R. Soc. Trop.

Med. Hyg. 72, 605609.

Techau, M.E., Johansen, M.V., Aasted, B., Lind, P., Ornbjerg,

N., Oswald, I.P., 2007. Cytokine mRNA proles in pigs

exposed prenatally and postnatally to Schistosoma japoni-

cum. Vet. Res. 38, 2536.

Trinchieri, G., Scott, P., 1999. Interleukin-12: basic principles

and clinical applications. Curr. Top. Microbiol. Immunol.

238, 5778.

Tsutsui, N., Kamiyama, T., 1999. Transforming growth factor

ology 215 (2010) 101112 111b-induced failure of resistance to infection with blood-

stages Plasmodium chabaudi in mice. Infect. Immun. 67,

23062311.

Uhr, J.W., Slavin, S.B., Pappenheimer, A.M., 1957. Delayed

hypersensitivity. II. Induction of hypersensitivity in guinea

pigs by means of antigenantibody complexes. J. Exp. Med.

105, 1124.

Willingham, A.L., Johansen, M.V., Bgh, H.O., Ito, A.,

Anderssen, J., Lindberg, R., Christensen, N.., Nansen, P.,

1999. Short report: congenital transmission of Schistosoma

japonicum in pigs. Am. J. Trop. Med. Hyg. 60, 311312.

Wilson, M.S., Mentink-Kane, M.M., Pesce, J.H., Ramalingam,

T., Thompson, R., Wynn, T.A., 2007. Immunopathology of

schistosomiasis. Immunol. Cell Biol. 85, 148154.

Wynn, T.A., Cheever, A.W., Jankovic, D., Poindexter, R.W.,

Caspar, P., Lewis, F.A., Sher, A., 1995. An IL-12-based

vaccination method for preventing brosis induced by

schistosome infection. Nature 376, 594596.

Yokoi, Y., Namihisa, T., Kuroda, H., Komatsu, I., Miyazaki,

A., Watanabe, S., Usui, K., 1984. Immunocytochemical

detection of desmin in fat-storing cells (Ito cells). Hepatol-

ogy 4, 709714.

Zhang, B.B., Jiao, Y.W., Cai, W.M., Tao, J., Liu, R.H., 2004.

Inuence of interferon gamma treatment on expression of

TGF-beta 1 and its receptors in liver brosis of mice with

Schistosoma japonicum. Zhongguo Ji Sheng Chong Xue Yu

Sheng Chong Bing Za Zhi 22, 340343.

Zhang, L.J., Zheng, W.D., Shi, M.N., Wang, X.Z., 2006.

Effects of interleukin-10 on activation and apoptosis of

hepatic stellate cells in brotic rat liver. World J. Gastro-

enterol. 12, 19181923.

ARTICLE IN PRESSA.A. Othman et al. / Immunobiology 215 (2010) 101112112

Congenital exposure to Schistosoma mansoni infection: Impact on the future immune response and the disease outcomeIntroductionMaterials and methodsParasiteAnimals and experimental designParasitological studyEvaluation of humoral factorsEstimation of S. mansoni-specific IgE and IgGEstimation of total IgE and IgG

Estimation of levels of IL-12 and TGF-beta mRNA expression by semi-quantitative real-time PCRHistopathological, histochemical, and immunohistochemical studyStatistical analysis

ResultsHepatic egg loadAntibody responseCytokine mRNA expressionHistopathological and histochemical findingsImmunohistochemical evaluation of GFAP expression

DiscussionReferences