Comparison of immune responses of Schistosoma mansoni-infected mice with distinct chronic forms of the disease

Cytokine patterns in experimental schistosomiasis mansoni infected mice treated with silymarin

The purpose of this study was to determine cytokine patterns in experimental schistosomiasis mansoni infected mice treated with silymarin. The study was conducted upon 100 mice that were divided into five groups; 20 each: uninfected control group, Schistosoma mansoni infected untreated mice (infected control), infected mice treated with praziquantel (PZQ), infected mice treated with silymarin and infected mice treated with both praziquantel and silymarin. 10 mice from each group were sacrificed at 10th and 18th weeks post infection respectively. Histopathological investigations were performed. Liver sections were stained with hematoxylin-eosin and Masson's trichrome stain to evaluate changes of granuloma sizes and numbers. Serum levels of the cytokines (TNF-α, IFN-γ, IL-4 and TGF-β1) were assessed in the sera of all groups by immunoassay. The measured levels of cytokines (IFN-γ, IL-4, TNF-α, TGF-β1) were found to be significantly increased in infected mice compared to normal control. At the same time, treated groups with silymarin alone or combined with PZQ showed significant decrease in IL-4, TNF-α and TGF-β1 levels compared to infected control. On the other hand, there was a significant increase in IFN-γ level observed in all treated groups compared to infected control. In addition, the histopathological examination of the liver in the group treated with PZQ showed a reduction in the number of livers eggs granuloma at all periods of sacrification compared with the infected untreated group. However, there was more decrease in granulomas diameter in both silymarin treated group or combined with PZQ at all periods of sacrification when compared to infected untreated group. In conclusion; treatment with silymarin combined with PZQ in murine schistosomiasis could reduce hepatic fibrosis by their action on the production of pro-inflammatory cytokines.

Immunological and parasitological parameters in Schistosoma mansoni-infected mice treated with crude extract from the leaves of Mentha x piperita L

Schistosomiasis is a chronic disease caused by an intravascular trematode of the genus Schistosoma. Praziquantel is the drug used for treatment of schistosomiasis; nevertheless failure of treatment has been reported. Consequently, the identification of new effective schistosomicidal compounds is essential to ensure the effective control of schistosomiasis in the future. In this work we investigated the immunomodulatory and antiparasitic effects of the crude leaves extract of Mentha x piperita L. (peppermint) on murine Schistosomiasis mansoni. Female Balb/c mice were infected each with 50 S. mansoni cercariae and divided into three experimental groups: (I) untreated; (II) treated daily with M. x piperita L. (100mg/kg) and III) treated on 1/42/43 days post-infection with Praziquantel (500mg/kg). Another group with uninfected and untreated mice was used as a control. Subsequently, seven weeks post-infection, S. mansoni eggs were counted in the feces, liver and intestine. Worms were recovered by perfusion of the hepatic portal system and counted. Sera levels of IL-10, IL-5, IL-13, IFN-γ, IgG1, IgE and IgG2a were assayed by ELISA. Animals treated with a daily dose of M. x piperita L. showed increased sera levels of IL-10, IFN-γ, IgG2a and IgE. Besides, M. x piperita L. treatment promoted reduction in parasite burden by 35.2% and significant decrease in egg counts in the feces and intestine.

Low transformation growth factor-β1 production and collagen synthesis correlate with the lack of hepatic periportal fibrosis development in undernourished mice infected with Schistosoma mansoni

Undernourished mice infected (UI) submitted to low and long-lasting infections by Schistosoma mansoni are unable to develop the hepatic periportal fibrosis that is equivalent to Symmers’ fibrosis in humans. In this report, the effects of the host’s nutritional status on parasite (worm load, egg viability and maturation) and host (growth curves, biology, collagen synthesis and characteristics of the immunological response) were studied and these are considered as interdependent factors influencing the amount and distribution of fibrous tissue in hepatic periovular granulomas and portal spaces. The nutritional status of the host influenced the low body weight and low parasite burden detected in UI mice as well as the number, viability and maturation of released eggs. The reduced oviposition and increased number of degenerated or dead eggs were associated with low protein synthesis detected in deficient hosts, which likely induced the observed decrease in transformation growth factor (TGF)-β1 and liver collagen. Despite the reduced number of mature eggs in UI mice, the activation of TGF-β1 and hepatic stellate cells occurred regardless of the unviability of most miracidia, due to stimulation by fibrogenic proteins and eggshell glycoproteins. However, changes in the repair mechanisms influenced by the nutritional status in deficient animals may account for the decreased liver collagen detected in the present study.

Regulation of the development of the hepatic B cell compartment during Schistosoma mansoni infection

During infection with the helminth parasite Schistosoma mansoni, Ab regulates hepatic inflammation, and local production of Ig in the liver appears to play a role in this process. Exploring the development of the B cell response during infection, we found that parasite-specific IgG1-secreting plasma cells appeared first in the hepatic and mesenteric lymph nodes (LNs) and then at later times in the spleen, liver, and bone marrow. The LN B cell population peaked between weeks 10 and 12 of infection, and then contracted at a time that coincided with the expansion of the hepatic IgG1(+) B cell compartment, suggesting that B cells migrate from LNs to liver. CXCL9 and -16 expression in the liver increased during the time frame of B cell recruitment. Expression of the CXCL16 receptor CXCR6 was increased on B cells within the hepatic LNs, but not the mesenteric LNs. CXCR3, the receptor for CXCL9, was broadly expressed on IgG1(+) B cells in LNs and liver during infection. Increased hepatic expression of CXCL9 and -16 failed to occur if the IL-10R was blocked in vivo, an intervention associated with decreased liver B cell infiltration and the development of severe disease. Hepatic LN IgG1(+) cells migrated toward CXCL9 and -16 in vitro and to the liver in a pertussis toxin-sensitive fashion. Our data suggest that the coordinated expression of CXCL9 and -16 in the liver and of CXCR6 and CXCR3 on responding B cells within the hepatic LNs underpins establishment of the hepatic B cell infiltrate during chronic schistosomiasis.

Blockade of B7-H1 (programmed death ligand 1) enhances humoral immunity by positively regulating the generation of T follicular helper cells

T follicular helper (T(FH)) cells are critical initiators in the development of T cell-dependent humoral immunity and the generation of protective immunity. We demonstrate that T(FH) cell accumulation and Ab production are negatively regulated by B7-H1 (programmed death ligand 1) in response to both helminth infection and active immunization. Following immunization of B7-H1(-/-) mice with keyhole limpet hemocyanin or helminth Ags, there is a profound increase in induction of T(FH) cells as a result of increased cell cycling and decreased apoptosis relative to wild-type mice. The increase in T(FH) cells in the absence of B7-H1 was associated with significant elevations in Ag-specific Ig response. Cotransfer experiments in vivo demonstrated that B7-H1 expression on B cells was required for negatively regulating T(FH) cell expansion and production of Ag-specific Ig. Treatment of immunized wild-type mice with anti-B7-H1 or anti-programmed death 1 mAbs, but not anti-B7-DC, led to a significant expansion of the T(FH) cell population and an enhanced Ag-specific Ig response. Our results demonstrate that the coinhibitory B7-H1/programmed death 1 pathway can limit the expansion of T(FH) cells and constrain Ag-specific Ig responses. This finding has direct implications for investigations examining the feasibility of therapeutically manipulating this pathway and reveals new insights into the regulation of the humoral immune response.

Repeated infections with Schistosoma mansoni and liver fibrosis in undernourished mice

The mouse model of schistosomal periportal fibrosis (Symmers' "pipestem" fibrosis), that develops in 30-50% of the infected animals, is not reproduced in undernourished mice. Host nutritional status is likely to be a variable that may influence the outcome and progression of infection, since it interferes with the dynamics of connective tissue changes occurring in chronic hepatic schistosomiasis. Re-infections increase the occurrence of periportal liver fibrosis in well-nourished animals, but it is not known how undernourished mice would behave being repeatedly re-infected. So, 21-day-old male albino Swiss mice were individually exposed to 30 cercariae (percutaneous route) of the BH strain of Schistosoma mansoni, 4 weeks after being on a low-protein diet. Control animals were fed on a commercial balanced chow for mice. The nutritional status was evaluated by body weight gain and measurement of food intake. Mice were divided into four groups: A1 (undernourished, single infected), A2 (well-nourished, single infected), B1 (undernourished, re-infected), B2 (well-nourished, re-infected). The primary infection was performed 4 weeks after ingesting the respective diet. Re-infections started 45 days later, with exposure to 15 cercariae, at 15 day intervals. Mice were sacrificed 18 weeks after the primary exposure. The livers were submitted to morphological (gross and microscopic pathology), morphometric (percentage of fibrosis; granuloma size; volume and numerical densities) by using semi-automatic morphometry, and biochemical (quantification of collagen as hydroxyproline) studies. Worm burdens and hepatic egg counting were also recorded. Values for body weight gains were always lower in undernourished mice, the effects of re-infection being minimal on this regard. Liver and spleen weights were higher in well-nourished mice (either single infected or re-infected) and mainly related to the type of ingested diet. A greater number of re-infected well-nourished mice developed periportal fibrosis, but undernourished re-infected animals did not reproduce this lesion. The percentage of fibrosis and hepatic collagen content were higher in well-nourished mice, but differences between single infected and re-infected groups were not statistically significant.

Long-term feeding a high-fat diet causes histological and parasitological effects on murine schistosomiasis mansoni outcome

This study investigated whether long-term feeding a high-fat diet (HFC) has an effect on schistosomiasis mansoni outcome compared to standard chow diet (SC). Swiss Webster female mice (3 wk old) fed each diet over 5 months, and then were infected with 50 Schistosoma mansoni cercariae. Their nutritional status was assessed by monitoring growth rates twice a week and measuring serum levels of lipoproteins. Mice were euthanised 63 days after infection. Parasitological and liver histological analyses were performed. The levels of TC, HDL-C and LDL-C, fecal and tissue schistosome eggs were statistically different (p<0.05) between groups. Livers from HFC mice showed exudative, exudative/exudative-productive, exudative-productive and productive granulomas, some degree of hepatic steatosis and focal necrosis. Mice fed normal-chow did not present productive granulomas and hepatic steatosis. The morphometric evaluation of hepatic granulomas did not reach statistical significance (p>0.05) between diets assayed. The high-fat diet for long-term produces effects on schistosomiasis mansoni outcome.

Dynamic changes of liver in cirrhosis model of rabbits

AIM: To establish a relatively simple and feasible rabbit model of liver cirrhosis and analyze the dynamic changes of function and histopathology of cirrhotic liver.

METHODS: Twenty-four New Zealand rabbits were divided into two groups, of which twenty were received subcutaneous injection of carbon tetrachloride (CCl₄) along with gastric infusion of edible ethanol for eight weeks. Animals in control group were fed with regular water and injected subcutaneously with the same quantity of olive oil. The development of hepatic fibrosis was recorded by Masson's trichrome method fortnightly. Blood samples were collected to measure the blood protein and enzymes fortnightly.

RESULTS: After treatment with CCl₄, hepatic fibrosis was aggravated with time went by. As compared with those in normal controls, the levels of aspartate transaminase (AST) and alanine aminotransferase (ALT) in the experimental groups were increased significantly (AST: 983.5 ± 116.7 nkat/L vs 650.1 ± 133.4 nkat/L, P = 0.03; ALT: 1867.1 ± 200.1 nkat/L vs 883.5 ± 116.7 nkat/L, P = 0.01), while the level of gamma-glutamyl transpeptidase (GGT) was decreased (100.1 ± 33.3 nkat/L vs 366.7 ± 50.1 nkat/L, P = 0.01) at the end of 8 wk. Typical features of liver cirrhosis and the formation of false lobe were observed at the end of 8 wk.

CONCLUSION: Rabbit models of liver cirrhosis, with a low mortality and high success rate, can be established by combination of CCl₄ and ethanol in a relatively short time.

Characterization of the vascular changes in schistosomal portal (pipestem) fibrosis of mice

Mice chronically infected with Schistosoma mansoni develop one of two anatomical forms of hepatic lesions: severe, periportal (pipestem) fibrosis or milder, isolated granulomas. The pathogenesis of periportal fibrosis is poorly understood. In this work we compared mice with either periportal fibrosis or isolated granulomas to identify specific markers of severe pathology. BALB/c or Swiss Webster mice were infected with 30 cercarie, once or six times, and liver biopsies were performed to classify the animals into two pathological groups 16 weeks later. Sixty percent of the animals sacrificed at 20 or 24 weeks had periportal fibrosis, 15-20% had isolated granulomas and the remainder had indeterminate pathology. There was no correlation between frequency of infections or egg burden (eggs/gliver) at 20 and 24 weeks post-infection and the development of periportal fibrosis. Livers with periportal fibrosis at 20 or 24 weeks of infection were characterized by larger areas of fibrotic tissue and greater vascularization compared to livers of mice with isolated granulomas. Plastic casts of the portal vein system showed marked changes in vascular structure in mice with periportal fibrosis, including collateral vessels sprouting from the main portal branches, amputation of the more delicate peripheral ramifications, and distortions of the medium and small branches. Vascular changes were not observed in mice with isolated granulomas. These results suggest that the interaction between schistosome eggs and portal vascular changes is of paramount importance in the development of pipestem fibrosis.