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, but Low Levels of IL-5, Are Associated with Hepatosplenic Disease in Human Schistosomiasis Mansoni1
*
Kenya Medical Research Institute,
Division of Vector Borne Diseases, Kenyan Ministry of Health, and
Department of Human Pathology, University of Nairobi, Nairobi, Kenya; and
§
Department of Pathology, Cambridge University, Cambridge, United Kingdom
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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, TNF, and circulating soluble TNF
receptor I (sTNFR-I), sTNFR-II, and sICAM-1. PBMC from the
hepatosplenic cases responded to in vitro Ag stimulation with
significantly higher levels of IFN- and TNF, but lower levels of
IL-5, compared with nonhepatosplenic controls matched for age and
infection intensity. Most of these correlations were confounded by
differences between geographical areas. However, principle component
analysis identified a high IFN- and TNF, and low IL-5 axis in the
data as the first principle component; this was significantly
associated with hepatosplenomegaly (p <
0.0005) even after controlling for area. High plasma levels of sTNFR-I
(p < 0.001), sTNFR-II,
(p < 0.0001), and sICAM-1
(p < 0.009) were also significantly
associated with hepatosplenomegaly, independently of area, in the case
of the soluble forms of both TNF receptors. These parameters were
negatively related to IL-5. These results suggest that proinflammatory
cytokines are involved in the hepatosplenic disease process in infected
individuals who have low anti-inflammatory Th2 responses and that
sTNFR may be a useful circulating marker for this disease process,
perhaps reflecting the level of TNF activity in hepatic tissues. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Most of the available information on the immune mechanisms underlying
the schistosome egg granuloma is derived from murine models and has
been interpreted in terms of the Th1/Th2 paradigm, which subdivides
CD4+ T cells on the basis of their characteristic patterns
of cytokine production (7). The granuloma is a cell-mediated,
CD4+ T cell-dependent response (8), controlled by a complex
pattern of often counter-regulating cytokines, chemotactic factors, and
cell adhesion factors, which successively initiate, maintain, and
immunomodulate the granuloma (7). Tissue egg deposition in S.
mansoni-infected mice initiates a switch of host cytokine
responses from those characteristic of a Th1 or Th0 to a Th2-like
pattern (9, 10, 11). Numerous experiments have demonstrated the central
role of IL-4 in murine schistosomiasis granuloma formation (12, 13, 14, 15) and
hepatic fibrosis (16), and the counteracting down-regulatory influence
of IFN- (15, 17, 18), which can be initiated by IL-12 (17, 18, 19).
Despite the antimorbidity effects of Th1 cytokines, TNF may also be an
important mediator of murine granuloma formation and hepatic fibrosis
(20, 21, 22, 23); part of the influence of TNF is associated with the
up-regulation of ICAM-1 expression (24).
The paucity of information on human anti-egg granulomatous
responses is such that it is difficult to judge how mechanisms
delineated in murine models are applicable to the human disease
process. In addition to differences that may occur between the
responses of any two host species to the same parasite, there are
particular differences between murine models and human infections. For
example: the Th1/Th2 subgrouping of human CD4+ T cells is
less well defined than in the mouse; human hepatosplenic
schistosomiasis develops at lower intensities of infection than it is
possible to achieve on the basis of number of worms per unit of host
body weight in the mouse; and human disease takes a number of years of
infection to develop (25), whereas murine infections are usually
studied over a few weeks or months. Relatively few studies of
Ag-specific cytokine expression and human hepatosplenic schistosomiasis
have been conducted. Of those that have been reported, only one (26)
examined hepatosplenic patients alongside infected, nonhepatosplenic
controls matched for age and intensity of infection, factors that
affect immune responses in endemic populations (27). Significant
associations between specific cytokine expression and human
hepatosplenic disease have yet to be established (28, 29, 30). Generally,
studies of inflammatory markers in sera or plasma from hepatosplenic
patients have also been uncontrolled, but have shown that infection
results in raised levels of TNF-
(31, 32, 33, 34), ICAM-1, and endothelial
leukocyte adhesion molecule (ELAM)-1 (35). In one study that was well
controlled, hepatosplenic patients had significantly raised levels of
serum TNF, but their peripheral blood monocytes released less TNF when
treated with mitogen (31).
In a case-control study, we examined TNF, IFN-, and IL-5 responses
of PBMC to in vitro stimulation with Con A as well as S.
mansoni worm and egg Ags in groups of S.
mansoni-infected patients, with and without hepatosplenomegaly,
who were carefully matched for age and intensity of infection. In
addition, in the same individuals, we measured plasma levels of
immunologically detectable TNF-, soluble TNF receptor I
(sTNFR-I),3 sTNFR-II, and
sICAM-1. The relationships between these parameters and their
associations with the presence or absence of hepatosplenomegaly were
analyzed.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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The patients in this study came from two areas of Kenya endemic for S. mansoni, Kambu and Kangundo, described in a previous paper (6). Both are almost exclusively populated by members of the same tribe (the Kamba) and have similar mean S. mansoni infection intensities but very different rates of hepatosplenomegaly (6).
The present study followed a case-control design: 20 patients from Kambu (a high morbidity area) with hepatosplenomegaly were each matched with two controls, one from Kambu and one from Kangundo (a low morbidity area), of the same age and with similar numbers of eggs in their stools but no detectable hepatosplenomegaly.
Organomegaly was assessed by palpation by an experienced clinician (G.G.M.). Palpable livers were measured in the midsternal and midclavicular lines. Palpable spleens were measured in the midclavicular and midaxillary lines. All hepatosplenic cases had both spleen and liver enlargement of at least 2 cm, while neither organ was palpable in the controls.
Ages were matched ± 1 yr, and egg counts ± 10% as
estimated from two Kato smears were prepared from a single stool.
Matches could not be found for all 20 cases: 19 were matched with
Kangundo controls and 17 with Kambu controls. Too few hepatosplenic
cases were found in Kangundo to balance the study with respect to area.
Characteristics of the patients in the study are summarized in Table I
.
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Isolation and stimulation of PBMC
PBMC were isolated from heparinized blood by density gradient
centrifugation on Histopaque 1077 (Sigma-Aldrich, Poole, Dorset, U.K.).
PBMC were washed in RPMI 1640 (ICN Flow Biomedicals, Thame,
Oxfordshire, U.K.) and resuspended at 1.5 x 106
cells/ml in Iscove’s medium (ICN Flow) supplemented with 5% AB serum
(final concentration), 100 U/ml penicillin, 100 µg/ml streptomycin,
and 20 mM L-glutamine. The cells were stimulated with
soluble worm Ag (SWA) and soluble egg Ag (SEA) prepared from respective
stages of the S. mansoni life cycle as previously described
(36). Cultures of 0.75 x 106 PBMC in 0.5 ml of
culture medium were stimulated with SWA and SEA at 10 µg/ml (final
concentration) in a total volume of 1 ml. Con A (Sigma) was used at 1
µg/ml. The Ags and mitogen used in the study were diluted from the
same batches, aliquoted, and stored at -20°C until required.
Cultures were maintained at 37°C in a humidified incubator with 5%
CO2 in air. Culture medium supernatants were collected
after 2 days for analysis of TNF and after 4 days for IFN- and IL-5.
After collection, the supernatants were stored in aliquots at
-20°C.
Cytokine and soluble receptor assays
IFN- and IL-5 were measured as marker cytokines for,
respectively, Th1- and Th2-type patterns of cytokine response. In
general, cytokine assays on PBMC culture supernatants were conducted as
previously described (37). The murine IL-5 dependent cell line B13
(American Type Culture Collection (ATCC), Rockville, MD) was used to
determine the levels of IL-5. The fibroblastic cell line L929 (ATCC)
was used to detect TNF in a rapid cytotoxicity assay. The B13 cell line
was regularly checked for IL-5 dependency, while L929 was checked for
TNF susceptibility. Briefly, 100 µl of B13 cells at 5 x
106 cells per ml were incubated with 100 µl of culture
supernatant in 96-well tissue culture plates in a humidified incubator
at 37°C in an atmosphere of 5% CO2 in air. After 3 days,
cytokine-dependent cell growth was assessed using the monotetrazolium
(MTT) colorimetric assay (38). To detect TNF, 100 µl of supernatant
was incubated with L929 cells at 2.5 x 105 cells per
ml in the presence of actinomycin D (2 µg/ml; Sigma-Aldrich) to a
final volume of 200 µl in 96-well tissue culture plates. After
overnight incubation, the medium was poured off and the cells were
stained with 100 µl of 0.5% crystal violet in methanol. The stain
was poured off, the plates were washed and then allowed to dry. One
hundred microliters of 10% acetic acid was used to solublize the
stain. Color release was read on a spectrophotometer at 540
nm.
To determine the levels of IFN- in supernatants, a capture ELISA was
used. Briefly, Maxisorp ELISA plates (Nunc; Life Technologies, Paisley,
U.K.) were coated with mouse anti-IFN- mAb (Interferon Sciences,
New Brunswick, NJ) in carbonate/bicarbonate buffer overnight. Plates
were then washed in PBS containing 0.05% Tween-20 (PBS-T) and blocked
with coating buffer containing 10% FCS. Culture supernatants were
added to the plates and incubated for 2 h at 37°C. IFN- was
detected by use of rabbit anti-human IFN- at 1:800 (Department
of Pathology, Cambridge University) and a goat anti-rabbit
peroxidase conjugate at 1:5000 (Dako, High Wycombe, Buckinghamshire,
U.K.). Finally, ABTS substrate (2, 2'-azino-bis [3-ethylbenzthiazoline
6-sulfonic acid] diammonium) was added, and the absorbance was
measured at a wavelength of 405 nm. Cytokine values for each test
sample were determined by interpolation from standard curves obtained
with recombinant cytokines that were included in each assay plate.
Assays of the plasma concentrations of immunologically detectable
TNF-, sTNFR-I, sTNFR-II, and sICAM-1 were all conducted using
commercially available sandwich ELISA assays (all from Genzyme
Diagnostics, Cambridge, MA) according to the manufacturer’s
instructions. Plasma samples from 10 healthy European donors, with no
history of schistosomiasis, were used as uninfected plasma controls in
these assays.
Statistical methods
The distributions of cytokine responses were highly skewed so that cytokine levels were categorized as either positive or negative (according to whether cytokine production of the stimulated cells was greater than the nonstimulated cells) for analysis by logistic regression.
Nonparametric tests (Kruskal-Wallis) on the raw data were used to
confirm the one-way analyses. Further analysis was performed on the
first principle component (MINITAB; Minitab, Inc., PA) derived from the
correlation matrix of the logarithms, log(.+1), of the six in vitro
Ag-stimulated PBMC cytokine production assays, TNF, IFN-, and IL-5
production after stimulation with either SWA or SEA. The first
principle component, which followed a reasonably normal distribution,
was analyzed by ANOVA.
The relationship between the PBMC cytokine responses and the circulating soluble receptors/sICAM-1 was examined using Spearman’s rank correlation coefficients.
Two "contrasts" between the groups, hepatosplenic cases vs nonhepatosplenic controls and Kambu vs Kangundo, were examined. These contrasts were somewhat confounded by the lack of hepatosplenic cases from Kangundo. The carefully balanced design with respect to age and intensity of infection (fecal egg counts) eliminated any influence of these variables on the analysis; the inclusion of these variables altered none of the conclusions, and they are considered no further in this report.
The significance in terms of the logistic regression models were tested
using 
2, the difference in deviance, which was
assumed to follow a 2 distribution under the null
hypothesis that the term was unimportant.
Logistic regression was performed using GLIM (Numerical Algorithms Group Ltd., Oxford, U.K.), while MINITAB was used for principle component calculation, analysis of variance and Kruskal-Wallis tests. Both software packages were run on Macintosh Quadra 800 microcomputers.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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The results of TNF and IL-5 bioassays and IFN- ELISA of PBMC
culture supernatants after stimulation with SEA, SWA, or Con A are
plotted in Figure 1 as geometric means
along with the 95% confidence intervals for each assay and each
morbidity group. The results of logistic regression on morbidity group
and geographical area are summarized in Table II. Little difference was seen between
the groups (or between morbidity or area contrasts) for any cytokine in
response to Con A. Hepatosplenic cases had higher TNF and IFN- but
lower IL-5 than the controls when cells were stimulated with either SWA
or SEA. These differences were significant by logistic regression
(Table II) in the case of TNF for both Ags, IFN- for SWA and IL-5
for SEA. The relationship between higher levels of SWA-stimulated
IFN- remained significant even when the possible influence of
different geographical areas was taken into account.
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shows the rank correlation
coefficient for the associations between the cytokine response to each
Ag/mitogen. From this comparison, it can be seen that TNF and IFN-
are positively correlated with each other, and both are negatively
correlated with IL-5.
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shows the correlation
coefficients between the first principle component and the SWA- and
SEA-stimulated PBMC responses (TNF, IFN-, IL-5) from which it was
derived. Since both of the IL-5 coefficients are positive, while those
for the TNF and IFN- are all negative, the first principle component
appears to correspond to a spectrum of response between Th1 and Th2.
The first principle component was considerably lower (i.e., more
"Th1-like") among the hepatosplenic cases than the nonhepatosplenic
controls (p < 0.0005 by ANOVA; Fig. 2), a difference that was undiminished
after controlling for differences between areas.
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Plasma from the same individuals in each morbidity group was
assayed in specific TNF- ELISA. These assays detected little or no
TNF- in any of the samples tested (data not shown). Serum levels of
the sTNFR-I and -II can be better markers for tissue TNF production
than serum levels of TNF itself, perhaps because of the instability or
short half-life of TNF (39). Therefore, the individuals from each
morbidity group were tested in ELISA to assess the levels of sTNFR-I
and sTNFR-II in their plasma. These results are shown in Figure 3 as geometric means for each soluble
receptor for each group along with their 95% confidence intervals.
Multiple regression analysis showed that both soluble receptors
remained significantly associated with hepatosplenomegaly after
controlling for differences between geographical areas (sTNFR-I:
F = 15.98 on 1 and 47 df, p
< 0.001; sTNFR-II: F = 31.45 on 1 and 48
df, p < 0.0001). All of the
schistosome-infected groups had significantly higher levels of sTNFR
compared with the uninfected European controls.
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, and IL-5 responses of PBMC to SWA, SEA, and Con A. Table V shows that there were statistically
significant positive relationships between all three circulating
soluble markers. No correlations between Con A-induced cytokines and
circulating sTNFR/sICAM-1 were found (results not shown).
However, the levels of all the circulating markers were found to be
generally positively correlated to Ag-induced IFN- and TNF responses
(often this was statistically significant), but negatively related to
IL-5 induced by the same Ags (Table V).
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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, and low levels of IL-5, produced
by PBMC stimulated specifically with schistosome Ags SWA and SEA, but
not with Con A, were significantly associated with the presence of
hepatosplenomegaly. These are the first statistically significant
relationships between Ag-specific cytokine responses and hepatosplenic
schistosomiasis to be reported from a study controlled for patient age
and intensity of infection. However, most of these relationships were
confounded by the difference between the two areas, Kangundo and Kambu.
The populations of these two areas suffer strikingly different levels
of hepatosplenic disease, despite having the same ethnic background and
similar intensities of infection (6). Environmental factors could
influence both the prevalence of the hepatosplenic manifestation of
schistosomiasis and immune responses. Such influences could be
important cofactors involved in a causal linking of elevated IFN-
and TNF with disease, or merely confounding factors, having an
independent effect on both cytokine profile and the occurrence of
hepatosplenic involvement. We have found that the high morbidity Kambu
area had a higher prevalence of malaria and that the population had a
poorer nutritional status (6, 40). It is worth noting that this study
was deliberately conducted outside of the malaria transmission season
and that blood smears were taken from all the individuals who
participated and none were found to have a detectable malaria
parasitaemia. Thus, while an active malaria infection is unlikely to be
a contributor to either the observed organomegaly or cytokine pattern,
the possibility of a previous history of malaria having an influence
cannot be eliminated by this study. A factor that might have contributed to the Kambu nonhepatosplenic controls being less significantly different from the Kambu hepatosplenic cases than were the Kangundo controls was that, on reexamination, some Kambu controls were found to have slight hepatosplenomegaly, which was not detected in the original physical examination used to define the subjects as being hepatosplenic or nonhepatosplenic. Reexamination of the Kangundo controls did not detect any low level hepatosplenic involvement. Thus, the differences in cytokine patterns between Kambu hepatosplenics and controls found in this study could have been underestimated.
Despite these or other factors that might have added "between area
differences" to any differences associated with the presence or
absence of hepatosplenic disease, the use of principle components
analysis clearly identified the relationship between Ag-specific
IFN- and TNF responses, on the one hand, and IL-5 responses, on the
other, as being significantly associated with the presence or absence
of hepatosplenomegaly, irrespective of geographical area.
Principle components analysis is a useful and commonly used technique
for condensing the information contained in a set of variables. It
rearranges the data into a series of new, independent variables the
first of which, the first principle component, is the linear
combination of the original variables, which retains the most
information about the whole data set. When applied to the Ag-specific
cytokine data, the coefficients of first principle component were
positive for the IL-5 variables, while those for the TNF and IFN-
variables were all negative, i.e., the analysis identified a broad
"Th1-Th2 axis" as the most prominent feature of the observed
cytokine profiles. Subsequent ANOVA on this first principle component
revealed that those with hepatosplenic disease gave a significantly
more "Th1-like" response than those from either of the two control
groups.
The identification of a broad cytokine axis associating IFN- and TNF
(which for convenience we have called "Th1-like") on the one hand
and IL-5 on the other is not surprising. Although TNF can be produced
by a number of different types of cells, TNF- is mainly produced by
activated macrophages (41). TNF is generally associated with Th1-like
responses, since Th1 cells can produce TNF directly and, by producing
IFN-, they enhance the production of TNF through its
macrophage-activating function (42). In addition, a number of Th2
cytokines have been shown to limit the expression and activity of Th1
cells. IL-4 is known to cause a reduction in the production of TNF,
possibly by regulating TNF gene expression (43).
Accumulated evidence from many studies, using a variety of mouse
models, strongly supports the hypothesis that Th2-type cytokine
responses, and IL-4 in particular, are critical in promoting the
schistosome egg granuloma. It has been shown that in vivo
neutralization of IL-4 suppresses egg granuloma formation, while
administration of rIL-4 enhances the granuloma response and decreases
Th1-like cytokine responses, including IFN- (12, 13, 14, 15). Anti-IL-4
treatment also significantly suppresses hepatic collagen formation and
expression of IL-5 and IL-13 mRNA in the liver (16). Neutralization of
endogenous IFN- has been shown usually to decrease murine granuloma
size (13, 15, 17, 44), while granuloma formation occurs normally in
IFN- knockout mice (18). Thus the observations reported here, that
in vitro stimulation with SEA and SWA induce PBMC from patients with
hepatosplenomegaly to produce more IFN- and less IL-5 than
nonhepatosplenic controls, would not be predicted from the
well-established association between Th2 cytokine responses, egg
granuloma formation, hepatic fibrosis, and portal hypertension seen in
the mouse. However, the significantly higher levels of Ag-induced TNF
in hepatosplenic patients can be more easily related to a number of
murine schistosomiasis studies. Anti-TNF serum reduced, and treatment
with TNF- increased, hepatic granuloma size in S.
mansoni-infected mice (20). Similarly, rTNF- has been shown to
reconstitute granuloma formation in S. mansoni-infected SCID
mice (21), and worm-induced TNF- has been shown to mediate the
immune priming necessary for hepatic granuloma formation after
injection of S. mansoni eggs into naive mice (23).
A particularly interesting S. mansoni-mouse model has been
described by Henderson and colleagues (45). In this model, CBA/J mice
chronically infected (10 to 20 wk in the mouse) with S.
mansoni, develop two distinct syndromes designated moderate
splenomegaly syndrome (MSS) and hypersplenomegaly syndrome (HSS), which
are similar to, respectively, the nonhepatosplenic (also termed
"intestinal") and hepatosplenic forms of schistosomiasis seen in
human populations. HSS occurs in about 20% of infected mice and is a
strikingly more severe form of the infection, characterized by massive
splenomegaly, ascites, thymic atrophy, severe anemia, and cachexia. In
addition, HSS mice suffer increased perioval and hepatic periportal
fibrosis (45). Recently, it has been shown that CBA/J mice that go on
to develop HSS fail to modulate the production of TNF- mRNA in their
livers and suffer greater liver fibrosis than MSS mice (22).
Interestingly, IL-4 knockout mice also suffer severe TNF--mediated
morbidity when infected with S. mansoni (46). As TNF- is
associated with the induction and maintenance of fibrotic reactions
(47, 48, 49), and as large amounts are produced by IFN- activated
macrophages (41), it is possible that chronically elevated levels of
IFN- and TNF (and low levels of counter-regulating Th2 cytokines)
might predispose some schistosome-infected individuals to the
development of hepatic fibrosis and hepatosplenic disease.
Some previous human studies have pointed toward the involvement of TNF in hepatosplenic schistosomiasis. In a well-controlled study, Zwingenberger and colleagues (31) found higher TNF levels in serum of patients with hepatosplenic disease compared with patients without organomegaly. Similar observations were made on Egyptian schistosomiasis patients who were not controlled for age and intensity of infection (33, 34). In addition, TNF secreted by nonstimulated monocytes and serum TNF was found to be elevated in S. haematobium-infected patients with carcinoma of the urinary bladder (32).
Our failure to detect significant levels of plasma TNF- may have
been because the methods used to separate PBMC for in vitro studies
were not optimal for the preservation of plasma TNF. However, in a
variety of infectious diseases, it has been shown that circulating
levels of TNF are increased only transiently in the early stages of
infection, while circulating concentrations of sTNFR remain elevated
for longer periods (39). Circulating levels of sTNFR-I or sTNFR-II have
been found to be more useful than circulating TNF for monitoring the
course of disease or morbidity in a variety of infections such as, for
example, leishmaniasis (50), tuberculosis (51), HIV infections, (52)
and rickettsiosis (53). In addition, circulating levels of sTNFR were
found to be useful indicators of disease activity and prognosis for
cancer (54) and rheumatoid arthritis (55). Here, we have found that
elevated plasma levels of sTNFR-I and sTNFR-II are strongly and
significantly correlated with the presence of hepatosplenic disease.
These correlations are significant, irrespective of geographical area,
and are supportive of the observation that elevated Ag-specific release
of TNF is a characteristic feature of the hepatosplenic form of human
schistosomiasis.
In experimental animal models, the administration of sTNFR can
neutralize the pathologic effects of TNF (56). TNFR:Fc has been shown
to neutralize the biologic activity of TNF- in mice (57) and in
human transplantation patients (58), and it reduces granuloma size in
murine schistosomiasis (24). It might have been expected, therefore,
that high levels of sTNFR would be negatively associated with
hepatosplenic disease, rather than the positive relationship found in
this study. However, it also appears that sTNFR can stabilize TNF-
and may facilitate its biologic activity (59). The positive
correlations shown in this study (Table V
) between circulating sTNFR
and in vitro TNF production by Ag-stimulated PBMC, in particular the
statistically significant correlation between the TNF response to SEA
and circulating sTNFR-I, suggest that sTNFR may be directly related to
up-regulated TNF and, therefore, may be acting as a circulating marker
for the local production of TNF in host tissues. It is interesting to
note that Josimovic-Alasevic and colleagues observed that elevated
concentrations of soluble 55 kDa IL-2R subunit are detectable in the
sera of hepatosplenic schistosomiasis patients (60).
In addition to proinflammatory cytokines and their antagonists, intercellular adhesion molecules may be important in the murine anti-egg granulomatous response. Elevated ICAM-1 expression is associated with murine acute phase granuloma formation (61). Anti-ICAM-1 Ab treatment suppresses murine S. mansoni egg granuloma formation, and injection of sTNFR:Fc down-regulates both granuloma formation and ICAM-1 expression (24). Secor and colleagues (35) have found that the circulating, soluble form of ICAM-1 was significantly higher in hepatosplenic Brazilian patients than in nonhepatosplenic infected individuals but, unfortunately, because of the age-distribution of infection intensity and morbidity in the study population, they were unable to directly match their subjects for age and intensity of infection. Our results support those of Secor and colleagues, in that circulating levels of sICAM-1 were significantly higher in Kenyan hepatosplenic patients than in the matched nonhepatosplenic controls, although this relationship fell just below the level of statistical significance when geographical area was taken into account.
In the present study, there was a consistent pattern of positive, often
statistically significant, correlations between Ag-induced TNF and
IFN- and circulating sTNFR-I/-II and sICAM-1; and there were
negative associations between these parameters and IL-5 (Table V). This
pattern, together with the relationship between these response patterns
and hepatosplenomegaly, strongly suggests a link, perhaps causal,
between Th1 responses to schistosome Ags, up-regulated proinflammatory
cytokines, and adhesion molecules, and the development of hepatosplenic
schistosomiasis.
A particular strength of this study design is that age and intensity of infection, which are important influences on immunologic responses in schistosome-infected populations, have been fully controlled for, thereby greatly increasing the chances of the identification of any immune correlations of hepatosplenic disease. However, the corollary is that the influence of these factors on morbidity cannot be assessed in this study, and therefore, caution should be exercized in extrapolating these results to the relationship between immunologic responses and hepatosplenic disease in older, perhaps less heavily infected individuals. Similarly, the current study groups were selected on the basis of hepatosplenomegaly rather than ultrasonography-detectable hepatic fibrosis, and it is important to acknowledge that the detailed relationship between these two aspects of schistosomiasis-associated morbidity remains largely undefined. We are, therefore, currently undertaking cross-sectional population studies, in addition to further case-control studies, to evaluate the relationship between immune responses, hepatosplenomegaly, and hepatic fibrosis. Cross-sectional studies of schistosomiasis endemic populations will complement the case-control study design, as no preselection of study subjects is involved, and therefore, the influences on both age and intensity of infection can be examined by multiple regression analysis.
The immune correlates of schistosomiasis-associated hepatosplenic disease reported in this study appear to contrast with the established role of Th2 responses in murine granuloma formation and hepatosplenic morbidity. The S. mansoni egg is a powerful stimulus to Th2-type cytokine responses. However, in evolutionary terms, it would be unfortunate if the predominant response of the natural host (man) to a common parasite was an entirely immunopathologic one. Indeed, most schistosome-infected individuals in endemic regions do not develop severe hepatosplenic disease. This being so, it is possible that a dominant Th2-like response to the egg may actually represent a normal, relatively nonpathologic, anti-inflammatory response in human schistosomiasis. In that case, it would be the minority of infected individuals, with a poor Th2 response, who fail to regulate their proinflammatory responses and consequently risk suffering severe hepatosplenic disease. While this conclusion is necessarily speculative, it does underline the need for further, carefully controlled studies of the interactions between human immune responses and schistosomiasis-induced hepatosplenic disease.
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Acknowledgments |
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Footnotes |
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2 Address correspondence and reprint requests to David W. Dunne, Division of Microbiology and Parasitology, Department of Pathology, Cambridge University, Tennis Court Road, Cambridge, CB2 IQP, U.K. E-mail address:
3 Abbreviations used in this paper: sTNFR-I, soluble TNF receptor I; SWA, S. mansoni soluble worm Ag; SEA, S. mansoni soluble egg Ag; ANOVA, analysis of variance; MSS, moderate splenomegaly syndrome; HSS, hypersplenomegaly syndrome.
Received for publication August 26, 1997. Accepted for publication October 23, 1997.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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 L. E. Bazzone, P. M. Smith, L. I. Rutitzky, M. G. Shainheit, J. F. Urban, T. Setiawan, A. M. Blum, J. V. Weinstock, and M. J. Stadecker Coinfection with the Intestinal Nematode Heligmosomoides polygyrus Markedly Reduces Hepatic Egg-Induced Immunopathology and Proinflammatory Cytokines in Mouse Models of Severe Schistosomiasis Infect. Immun., November 1, 2008; 76(11): 5164 - 5172. [Abstract] [Full Text] [PDF]
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S. Wilson, F. M. Jones, J. K. Mwatha, G. Kimani, M. Booth, H. C. Kariuki, B. J. Vennervald, J. H. Ouma, E. Muchiri, and D. W. Dunne Hepatosplenomegaly Is Associated with Low Regulatory and Th2 Responses to Schistosome Antigens in Childhood Schistosomiasis and Malaria Coinfection Infect. Immun., May 1, 2008; 76(5): 2212 - 2218. [Abstract] [Full Text] [PDF]
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 N. BERHE, B. L. HALVORSEN, T. E. GUNDERSEN, B. MYRVANG, S. G. GUNDERSEN, and R. BLOMHOFF REDUCED SERUM CONCENTRATIONS OF RETINOL AND {alpha}-TOCOPHEROL AND HIGH CONCENTRATIONS OF HYDROPEROXIDES ARE ASSOCIATED WITH COMMUNITY LEVELS OF S. MANSONI INFECTION AND SCHISTOSOMAL PERIPORTAL FIBROSIS IN ETHIOPIAN SCHOOL CHILDREN Am J Trop Med Hyg, May 1, 2007; 76(5): 943 - 949. [Abstract] [Full Text] [PDF]
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H. M. COUTINHO, T. LEENSTRA, L. P. ACOSTA, L. SU, B. JARILLA, M. A. JIZ, G. C. LANGDON, R. M. OLVEDA, S. T. MCGARVEY, J. D. KURTIS, et al. PRO-INFLAMMATORY CYTOKINES AND C-REACTIVE PROTEIN ARE ASSOCIATED WITH UNDERNUTRITION IN THE CONTEXT OF SCHISTOSOMA JAPONICUM INFECTION. Am J Trop Med Hyg, October 1, 2006; 75(4): 720 - 726. [Abstract] [Full Text] [PDF]
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L. F. Alves Oliveira, E. C. Moreno, G. Gazzinelli, O. A. Martins-Filho, A. M. S. Silveira, A. Gazzinelli, L. C. C. Malaquias, P. LoVerde, P. M. Leite, and R. Correa-Oliveira Cytokine Production Associated with Periportal Fibrosis during Chronic Schistosomiasis Mansoni in Humans Infect. Immun., February 1, 2006; 74(2): 1215 - 1221. [Abstract] [Full Text] [PDF]
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A. E. EZEAMAMA, J. F. FRIEDMAN, L. P. ACOSTA, D. C. BELLINGER, G. C. LANGDON, D. L. MANALO, R. M. OLVEDA, J. D. KURTIS, and S. T. MCGARVEY HELMINTH INFECTION AND COGNITIVE IMPAIRMENT AMONG FILIPINO CHILDREN Am J Trop Med Hyg, May 1, 2005; 72(5): 540 - 548. [Abstract] [Full Text] [PDF]
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L. I. Rutitzky, H. J. Hernandez, Y.-S. Yim, D. E. Ricklan, E. Finger, C. Mohan, I. Peter, E. K. Wakeland, and M. J. Stadecker Enhanced Egg-Induced Immunopathology Correlates With High IFN-{gamma} in Murine Schistosomiasis: Identification of Two Epistatic Genetic Intervals J. Immunol., January 1, 2005; 174(1): 435 - 440. [Abstract] [Full Text] [PDF]
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A. Ribeiro de Jesus, A. Magalhaes, D. Gonzalez Miranda, R. Gonzalez Miranda, M. I. Araujo, A. Almeida de Jesus, A. Silva, L. B. Santana, E. Pearce, and E. M. Carvalho Association of Type 2 Cytokines with Hepatic Fibrosis in Human Schistosoma mansoni Infection Infect. Immun., June 1, 2004; 72(6): 3391 - 3397. [Abstract] [Full Text] [PDF]
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S. Joseph, F. M. Jones, G. Kimani, J. K. Mwatha, T. Kamau, F. Kazibwe, J. Kemijumbi, N. B. Kabatereine, M. Booth, H. C. Kariuki, et al. Cytokine Production in Whole Blood Cultures from a Fishing Community in an Area of High Endemicity for Schistosoma mansoni in Uganda: the Differential Effect of Parasite Worm and Egg Antigens Infect. Immun., February 1, 2004; 72(2): 728 - 734. [Abstract] [Full Text] [PDF]
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M. Booth, J. K. Mwatha, S. Joseph, F. M. Jones, H. Kadzo, E. Ireri, F. Kazibwe, J. Kemijumbi, C. Kariuki, G. Kimani, et al. Periportal Fibrosis in Human Schistosoma mansoni Infection Is Associated with Low IL-10, Low IFN-{gamma}, High TNF-{alpha}, or Low RANTES, Depending on Age and Gender J. Immunol., January 15, 2004; 172(2): 1295 - 1303. [Abstract] [Full Text] [PDF]
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C. Eboumbou Moukoko, N. El Wali, O. K. Saeed, Q. Mohamed-Ali, J. Gaudart, A. J. Dessein, and C. Chevillard No Evidence for a Major Effect of Tumor Necrosis Factor Alpha Gene Polymorphisms in Periportal Fibrosis Caused by Schistosoma mansoni Infection Infect. Immun., October 1, 2003; 71(10): 5456 - 5460. [Abstract] [Full Text] [PDF]
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A. C. La Flamme, A. S. MacDonald, C. R. Huxtable, M. Carroll, and E. J. Pearce Lack of C3 Affects Th2 Response Development and the Sequelae of Chemotherapy in Schistosomiasis J. Immunol., January 1, 2003; 170(1): 470 - 476. [Abstract] [Full Text] [PDF]
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S. Henri, C. Chevillard, A. Mergani, P. Paris, J. Gaudart, C. Camilla, H. Dessein, F. Montero, N.-E. M. A. Elwali, O. K. Saeed, et al. Cytokine Regulation of Periportal Fibrosis in Humans Infected with Schistosoma mansoni: IFN-{gamma} Is Associated with Protection Against Fibrosis and TNF-{alpha} with Aggravation of Disease J. Immunol., July 15, 2002; 169(2): 929 - 936. [Abstract] [Full Text] [PDF]
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A. S. MacDonald, M. I. Araujo, and E. J. Pearce Immunology of Parasitic Helminth Infections Infect. Immun., February 1, 2002; 70(2): 427 - 433. [Full Text] [PDF]
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A. C. La Flamme, E. A. Patton, and E. J. Pearce Role of Gamma Interferon in the Pathogenesis of Severe Schistosomiasis in Interleukin-4-Deficient Mice Infect. Immun., December 1, 2001; 69(12): 7445 - 7452. [Abstract] [Full Text] [PDF]
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 L. I. Rutitzky, H. J. Hernandez, and M. J. Stadecker Th1-polarizing immunization with egg antigens correlates with severe exacerbation of immunopathology and death in schistosome infection PNAS, October 16, 2001; (2001) 231258498. [Abstract] [Full Text] [PDF]
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M. I. Araujo, S. K. Bliss, Y. Suzuki, A. Alcaraz, E. Y. Denkers, and E. J. Pearce Interleukin-12 Promotes Pathologic Liver Changes and Death in Mice Coinfected with Schistosoma mansoni and Toxoplasma gondii Infect. Immun., March 1, 2001; 69(3): 1454 - 1462. [Abstract] [Full Text] [PDF]
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A. C. La Flamme, E. A. Patton, B. Bauman, and E. J. Pearce IL-4 Plays a Crucial Role in Regulating Oxidative Damage in the Liver During Schistosomiasis J. Immunol., February 1, 2001; 166(3): 1903 - 1911. [Abstract] [Full Text] [PDF]
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K. F. Hoffmann, A. W. Cheever, and T. A. Wynn 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., June 15, 2000; 164(12): 6406 - 6416. [Abstract] [Full Text] [PDF]
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H. Asahi, A. Osman, R. M. Cook, P. T. LoVerde, and M. J. Stadecker Schistosoma mansoni Phosphoenolpyruvate Carboxykinase, a Novel Egg Antigen: Immunological Properties of the Recombinant Protein and Identification of a T-Cell Epitope Infect. Immun., June 1, 2000; 68(6): 3385 - 3393. [Abstract] [Full Text] [PDF]
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P. W. Mola, I. O. Farah, T. M. Kariuki, M. Nyindo, R. E. Blanton, and C. L. King Cytokine Control of the Granulomatous Response in Schistosoma mansoni-Infected Baboons: Role of Exposure and Treatment Infect. Immun., December 1, 1999; 67(12): 6565 - 6571. [Abstract] [Full Text] [PDF]
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C. Cetre, C. Pierrot, C. Cocude, S. Lafitte, A. Capron, M. Capron, and J. Khalife Profiles of Th1 and Th2 Cytokines after Primary and Secondary Infection by Schistosoma mansoni in the Semipermissive Rat Host Infect. Immun., June 1, 1999; 67(6): 2713 - 2719. [Abstract] [Full Text] [PDF]
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L. I. Rutitzky, H. J. Hernandez, and M. J. Stadecker Th1-polarizing immunization with egg antigens correlates with severe exacerbation of immunopathology and death in schistosome infection PNAS, November 6, 2001; 98(23): 13243 - 13248. [Abstract] [Full Text] [PDF]
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