The role of chemokines in controlling granulomatous inflammation in Schistosoma mansoni infection

Schistosomiasis Mansoni-Recruited Eosinophils: An Overview in the Granuloma Context

Eosinophils are remarkably recruited during schistosomiasis mansoni, one of the most common parasitic diseases worldwide. These cells actively migrate and accumulate at sites of granulomatous inflammation termed granulomas, the main pathological feature of this disease. Eosinophils colonize granulomas as a robust cell population and establish complex interactions with other immune cells and with the granuloma microenvironment. Eosinophils are the most abundant cells in granulomas induced by Schistosoma mansoni infection, but their functions during this disease remain unclear and even controversial. Here, we explore the current information on eosinophils as components of Schistosoma mansoni granulomas in both humans and natural and experimental models and their potential significance as central cells triggered by this infection.

Protein undernutrition reduces the efficacy of praziquantel in a murine model of Schistosoma mansoni infection

Background

Undernutrition and schistosomiasis are public health problems and often occur in low and middle-income countries. Protein undernutrition can alter the host-parasite environment system and aggravate the course of schistosomiasis. This study aimed to assess the impact of a low-protein diet on the efficacy of praziquantel.

Methodology/Principal findings

Thirty-day-old mice were fed with a low-protein diet, and 40 days later, they were individually infected with fifty Schistosoma mansoni cercariae. A 28-day-treatment with praziquantel at 100 mg/kg for five consecutive days followed by distilled water begins on the 36^th day post-infection. Mice were sacrificed on the 64^th day post-infection. We determined the parasitological burden, liver and intestine histomorphometry, liver injury, and immunomodulation parameters. Praziquantel treatment of infected mice fed with a standard diet (IN-PZQ) resulted in a significant reduction of worm and egg burdens and a normalization of iron and calcium levels. The therapy also improved schistosomiasis-induced hepatopathy and oxidative stress. The anti-inflammatory and immunomodulatory activities of praziquantel were also significant in these mice. When infected mice receiving the low-protein diet were treated with praziquantel (ILP-PZQ), the body weight loss and hepatomegaly were not alleviated, and the worm and liver egg burdens were significantly higher than those of IN-PZQ mice (P < 0.001). The treatment did not reduce the increased activities of ALT and γ-GGT, the high malondialdehyde concentration, and the liver granuloma volume. The iron and calcium levels were not ameliorated and differed from those of IN-PZQ mice (P < 0.001 and P < 0.05). Moreover, in these mice, praziquantel treatment did not reverse the high level of IL-5 and the low mRNA expression of CCL3/MIP-1α and CXCL-10/IP-10 induced by S. mansoni infection.

Conclusion/Significance

These results demonstrated that a low-protein diet reduced the schistosomicidal, antioxidant, anti-inflammatory, and immunomodulatory activities of praziquantel.

Almost 90% of people requiring schistosomiasis preventive chemotherapy in 2018 lived in sub-Saharan Africa. Besides, 205.3 million children under five years suffer and die of undernutrition in low- and middle-income countries. The physiopathology of schistosomiasis mansoni involves liver damage, oxidative stress, and perturbation of the immune response. These disturbances are intensified by undernutrition. Praziquantel is used to treat schistosomiasis, but its efficacy on the comorbidity of S. mansoni infection and undernutrition has not been investigated. We conducted this study to assess the effectiveness of praziquantel on S. mansoni infection in mice fed with a low-protein diet. We recorded growth retardation, hepatomegaly, and high worm and egg burdens in mice fed with a low-protein diet and treated with PZQ. Moreover, the treatment did not reverse the liver function injury, oxidative stress, high iron level, and low calcium level. The proinflammatory cytokine IL-5 was still high, and the gene expression of some macrophage-associated chemokines was reduced. Therefore, this study demonstrated that in a murine model of a low-protein diet, the efficacy of praziquantel on S. mansoni infection was reduced. It also underlines the importance of targeting protein deficiency and malnutrition in populations living in schistosomiasis endemic areas for efficient disease control.

Pathological and immunological evaluation of different regimens of praziquantel treatment in a mouse model of Schistosoma mansoni infection

Background

One of the considerable challenges of schistosomiasis chemotherapy is the inefficacy of praziquantel (PZQ) at the initial phase of the infection. Immature schistosomes are not susceptible to PZQ at the curative dose. Here, we investigated the efficacy of different PZQ regimens administered during the initial stage of Schistosoma mansoni infection in mice.

Methodology/Principal findings

Two months-old mice were individually infected with 80 S. mansoni cercariae and divided into one infected-untreated control group (IC) and four PZQ-treated groups: PZQ at 100 mg/kg/day for five consecutive days (group PZQ1), PZQ at 100 mg/kg/day for 28 days (group PZQ2), PZQ at 18 mg/kg/day for 28 days (group PZQ3) and a single dose of PZQ at 500 mg/kg (group PZQ4). The treatment started on day one post-infection (p.i), and each group of mice was divided into two subgroups euthanized on day 36 or 56 p.i, respectively. We determined the mortality rate, the parasitological burden, the hepatic and intestinal granulomas, the serum levels of Th-1, Th-2, and Th-17 cytokines, and gene expression. The treatment led to a significant (p < 0.001) reduction of worm burden and egg counts in the intestine and liver in groups PZQ2 and PZQ3. On 56th day p.i, there was a significant reduction (p < 0.001) of the number and volume of the hepatic granulomas in groups PZQ2 and PZQ3 compared to group PZQ1 or PZQ4. Moreover, in group PZQ3, the serum levels of IFN-γ, TNF-α, IL-13, and IL-17 and their liver mRNA expressions were significantly reduced while IL-10 and TGF-β gene expression significantly increased. The highest mortality rate (81.25%) was recorded in group PZQ2.

Conclusion/Significance

This study revealed that the administration of PZQ at 18 mg/kg/day for 28 consecutive days was the optimal effective posology for treating S. mansoni infection at the initial stage in a murine model.

CCR5 and CCR5Δ32 in bacterial and parasitic infections: Thinking chemokine receptors outside the HIV box

The CCR5 molecule was reported in 1996 as the main HIV-1 co-receptor. In that same year, the CCR5Δ32 genetic variant was described as a strong protective factor against HIV-1 infection. These findings led to extensive research regarding the CCR5, culminating in critical scientific advances, such as the development of CCR5 inhibitors for the treatment of HIV infection. Recently, the research landscape surrounding CCR5 has begun to change. Different research groups have realized that, since CCR5 has such important effects in the chemokine system, it could also affect other different physiological systems. Therefore, the effect of reduced CCR5 expression due to the presence of the CCR5Δ32 variant began to be further studied. Several studies have investigated the role of CCR5 and the impacts of CCR5Δ32 on autoimmune and inflammatory diseases, various types of cancer, and viral diseases. However, the role of CCR5 in diseases caused by bacteria and parasites is still poorly understood. Therefore, the aim of this article is to review the role of CCR5 and the effects of CCR5Δ32 on bacterial (brucellosis, osteomyelitis, pneumonia, tuberculosis and infection by Chlamydia trachomatis) and parasitic infections (toxoplasmosis, leishmaniasis, Chagas disease and schistosomiasis). Basic information about each of these infections was also addressed. The neglected role of CCR5 in fungal disease and emerging studies regarding the action of CCR5 on regulatory T cells are briefly covered in this review. Considering the "renaissance of CCR5 research," this article is useful for updating researchers who develop studies involving CCR5 and CCR5Δ32 in different infectious diseases.

Schistosoma mansoni PCR+ -infected individuals in the Sudan present elevated systemic levels of chemokines when compared to uninfected and egg+ cohorts

Infections with Schistosoma mansoni remain a major health problem in the Sudan where endemic communities, such as those in Kassala and Khartoum states, continue to face severe social-economic difficulties. Our previous immunoepidemiological findings revealed different immune [cytokine and S. mansoni egg (SEA) antibody] profiles in individuals with active infections (eggs in stool n = 110), individuals positive for S. mansoni via polymerase chain reaction (PCR) using sera (SmPCR⁺ n = 63) and those uninfected (Sm uninf). As antibody responses to eggs and worms are known to change during infection, we have expanded the profiling further by determining levels of adult worm (SWA) antibodies and nine chemokines in the serum of each individual in the three different cohorts. With the exception of C-C motif chemokine ligand (CCL)2, all measured chemokines were significantly higher in SmPCR⁺ individuals when compared to the egg⁺ group and in addition they also presented elevated levels of SWA-specific immunoglobulin (Ig)G2. Multivariable regression analysis further revealed that infection per se was strongly linked to SWA-specific IgG3 levels and CCL5 was strongly associated with a SmPCR⁺ diagnostic state. In the absence of PCR diagnostics that recognize juvenile worms or schistosomulae motives, identifying schistosome-specific traits should provide better insights into current prevalence rates in endemic communities and, in doing so, take into consideration PCR⁺ non-egg⁺ individuals in current treatment programmes.

Systemic Cytokine and Chemokine Profiles in Individuals With Schistosoma mansoni Infection and Low Parasite Burden

Intestinal schistosomiasis, caused by the parasitic trematode Schistosoma mansoni, is a chronic disease and the prolonged and continuous exposure to S. mansoni antigens results in a deviation of the host's immune response. For diagnosis, the Kato-Katz (KK) method is recommended, however, this method showed low accuracy in areas of low endemicity. This study aimed to characterize the cytokine and chemokine profile of individuals with an extremely low parasite load (<4 eggs per gram of feces), e.g., individuals who were detected by alternative parasitological methods, such as the saline gradient and/or Helmintex®. In order to search for immunological markers for infection, the immunological profile in serum samples of these individuals was then compared with patients detected with the KK method and with a higher parasite load and with individuals repetitively negative by extensive stool exams. The study was conducted in Northern Minas Gerais in a rural area of the Municipality of Januária. Serum samples of a total of 139 parasitologically well-characterized individuals were assessed for the following immunological markers by commercially available immunoassays: TNF-α, IL-1β, IL-6, IL-17A, IL-5, IL-10, IL-13, IL-33, IL-27, CCL3, CCL5, CXCL10, CCL11, and CCL17. As a result, there were no significant differences in concentrations or frequencies for immunological markers between egg-negative individuals or individuals with ultra-low (<4 epg) or low (4-99 epg) parasite loads. However, we found significant correlations between egg counts and eosinophil counts and between egg counts and IL-1β or TNF-α concentrations. The most striking alterations were found in individuals with the highest parasite load (≥100 epg). They had significantly higher TNF-α concentrations in serum when compared with individuals with a low parasite load (4-99 epg) and CCL17 concentrations were significantly elevated when compared with egg-negative individuals. Radar diagrams of frequencies for cytokine and chemokine responders in each infection group confirmed a distinct profile only in the infection group with highest parasite loads (≥100 epg).

Host Regulators of Liver Fibrosis During Human Schistosomiasis

Liver fibrosis is a wound-healing process purposely aimed at restoring organ integrity after severe injury caused by autoimmune reactions, mechanical stress or infections. The uncontrolled solicitation of this process is pathogenic and a pathognomonic feature of diseases like hepatosplenic schistosomiasis where exacerbated liver fibrosis is centrally positioned among the drivers of the disease morbidity and mortality. Intriguingly, however, liver fibrosis occurs and progresses dissimilarly in schistosomiasis-diseased individuals with the same egg burden and biosocial features including age, duration of residence in the endemic site and gender. This suggests that parasite-independent and currently poorly defined host intrinsic factors might play a defining role in the regulation of liver fibrosis, the hallmark of morbidity, during schistosomiasis. In this review, we therefore provide a comprehensive overview of all known host candidate regulators of liver fibrosis reported in the context of human schistosomiasis.

Schistosome-Induced Fibrotic Disease: The Role of Hepatic Stellate Cells

Hepatic fibrosis is a common pathology in various liver diseases. Hepatic stellate cells (HSCs) are the main cell type responsible for collagen deposition and fibrosis formation in the liver. Schistosomiasis is characterised by granulomatous fibrosis around parasite eggs trapped within the liver and other host tissues. This response is facilitated by the recruitment of immune cells and the activation of HSCs. The interactions between HSCs and schistosome eggs are complex and diverse, and a better understanding of these interactions could lead to improved resolution of fibrotic liver disease, including that associated with schistosomiasis. Here, we discuss recent advances in HSC biology and the role of HSCs in hepatic schistosomiasis.

Plasma levels of innate immune mediators are associated with liver fibrosis in low parasite burden Schistosoma mansoni-infected individuals

In the murine model, it was demonstrated that pro-inflammatory cytokines and chemokines are essential to the formation and modulation of Schistosoma-induced granulomatous inflammation. However, the relationship of these immune mediators and disease severity is hard to be established in naturally infected individuals. The current study evaluates the association between plasma concentrations of MIF, sTNF-R1, CCL3, CCL7 and CCL24 and schistosomiasis morbidity in Schistosoma mansoni-infected patients with a low parasite burden. For this propose, 97 S. mansoni-infected individuals were subjected to abdominal ultrasound analysis and clinical examination. Among them, 88 had plasma concentration of immune mediators estimated by ELISA assay. Multivariate linear regression models were used to evaluate the relationship between the plasma concentration of immune mediators and the variables investigated. Although most individuals presented low parasite burden, over 30% of them showed signs of fibrosis defined by ultrasound measurements and 2 patients had a severe form of schistosomiasis. No association between parasite burden and the plasma levels of chemokine/cytokines or disease severity was observed. There was a positive association between plasma concentration of CCL4, sTNF-R1, CCL3 and MIF with gall bladder thickness and/or with portal vein thickness that are liver fibrosis markers. In contrast, no association was found between CCL7 plasma concentrations with any of the schistosomiasis morbidity parameters evaluated. The data showed that CCL24, sTNFR1, MIF and CCL3 can be detected in plasma of S. mansoni-infected individuals and their concentration would be used as prognostic makers of Schistosoma-induced liver fibrosis, even in individuals with low parasite burden.

The role of CCR5 in Chagas disease - a systematic review

Chagas disease is an infection caused by the protozoan Trypanosoma cruzi. The clinical manifestations result from the chronic forms of the disease: indeterminate, cardiac, digestive or mixed. The pathogenesis of this disease is related to the genetic variability of both the parasite and the host with polymorphisms of genes involved in immune response possibly being involved in the variable clinical course. Cytokines play a key role in regulating immune response, in particular chemokines exert a crucial role in the control of leukocyte migration during the host's response to infectious processes. Furthermore, inflammatory cytokines and chemokines have been implicated in the generation of inflammatory infiltrates and tissue damage. The involvement of the CC Chemokine Receptor 5 (CCR5) in leukocyte migration to sites of inflammation has been elucidated and this receptor has been investigated in Chagas disease. Here we review the role of CCR5 in T. cruzi infection as well as its importance in the pathogenesis of the Chagas disease.

Macrophages are critical to the maintenance of IL-13-dependent lung inflammation and fibrosis

The roles of macrophages in type 2-driven inflammation and fibrosis remain unclear. Here, using CD11b-diphtheria toxin receptor (DTR) transgenic mice and three models of interleukin 13 (IL-13)-dependent inflammation, fibrosis, and immunity, we show that CD11b(+) F4/80(+) Ly6C(+) macrophages are required for the maintenance of type 2 immunity within affected tissues but not secondary lymphoid organs. Direct depletion of macrophages during the maintenance or resolution phases of secondary Schistosoma mansoni egg-induced granuloma formation caused a profound decrease in inflammation, fibrosis, and type 2 gene expression. Additional studies with CD11c-DTR and CD11b/CD11c-DTR double-transgenic mice suggested that macrophages but not dendritic cells were critical. Mechanistically, macrophage depletion impaired effector CD4(+) T helper type 2 (Th2) cell homing and activation within the inflamed lung. Depletion of CD11b(+) F4/80(+) Ly6C(+) macrophages similarly reduced house dust mite-induced allergic lung inflammation and suppressed IL-13-dependent immunity to the nematode parasite Nippostrongylus brasiliensis. Consequently, therapeutic strategies targeting macrophages offer a novel approach to ameliorate established type 2 inflammatory diseases.

Immunological Profile in Individuals with Schistosomal Myeloradiculopathy

BACKGROUND

Schistosomal myeloradiculopathy (SMR) is the most serious ectopic presentation of Schistosoma mansoni infection. The pathogenesis occurs mainly via the host inflammatory response to the eggs of the parasite that are stuck in the central nervous system, and the diagnosis is generally made by the exclusion of other neurological diseases.

OBJECTIVE

We aimed to evaluate the immune status of SMR patients and to identify a marker for SMR diagnosis.

METHODS

We enrolled 15 patients with a presumptive diagnosis of SMR, and the control groups included 17 patients with myelopathy associated with human T cell lymphotropic virus type 1 (HTLV-1) and 11 with other neurological disorders. The determination of soluble egg antigen-specific IgE and the levels of cytokines from Th1, Th2, Th17 and T-regulatory cell profiles and the chemokines MIP-1a and RANTES were measured in the cerebrospinal fluid (CSF) and serum using an ELISA technique.

RESULTS

We observed that SMR leads to an increase in IgE levels in the CSF compared to serum, and the levels of IL-13 and MIP-1α were significantly higher in the CSF and serum of the SMR patients than in the patients with HTLV-1-associated myelopathy. The levels of MIP-1α and RANTES were higher in the CSF than in the serum of the SMR group. The ratio between levels of IL-13, MIP-1α and RANTES over IL-10 was positive in the CSF of the SMR patients.

CONCLUSIONS

These results indicate that S. mansoni-specific IgE in the CSF is a promising marker for the diagnosis of SMR and that the cytokines and chemokines associated with the Th2 profile may be important factors in the immunopathogenesis of SMR.

Protective Potential of Antioxidant Enzymes as Vaccines for Schistosomiasis in a Non-Human Primate Model

Schistosomiasis remains a major cause of morbidity in the world. The challenge today is not so much in the clinical management of individual patients, but rather in population-based control of transmission in endemic areas. Despite recent large-scale efforts, such as integrated control programs aimed at limiting schistosomiasis by improving education and sanitation, molluscicide treatment programs and chemotherapy with praziquantel, there has only been limited success. There is an urgent need for complementary approaches, such as vaccines. We demonstrated previously that anti-oxidant enzymes, such as Cu-Zn superoxide dismutase (SOD) and glutathione S peroxidase (GPX), when administered as DNA-based vaccines induced significant levels of protection in inbred mice, greater than the target 40% reduction in worm burden compared to controls set as a minimum by the WHO. These results led us to investigate if immunization of non-human primates with antioxidants would stimulate an immune response that could confer protection as a prelude study for human trials. Issues of vaccine toxicity and safety that were difficult to address in mice were also investigated. All baboons in the study were examined clinically throughout the study and no adverse reactions occurred to the immunization. When our outbred baboons were vaccinated with two different formulations of SOD (SmCT-SOD and SmEC-SOD) or one of GPX (SmGPX), they showed a reduction in worm number to varying degrees, when compared with the control group. More pronounced, vaccinated animals showed decreased bloody diarrhea, days of diarrhea, and egg excretion (transmission), as well as reduction of eggs in the liver tissue and in the large intestine (pathology) compared to controls. Specific IgG antibodies were present in sera after immunizations and 10 weeks after challenge infection compared to controls. Peripheral blood mononuclear cells, mesenteric, and inguinal node cells from vaccinated animals proliferated and produced high levels of cytokines and chemokines in response to crude and recombinant antigens compared with controls. All together, these data demonstrate the potential of antioxidants as a vaccine in a non-human primate model.

A boswellic acid-containing extract ameliorates schistosomiasis liver granuloma and fibrosis through regulating NF-κB signaling in mice

Boswellic acid (BA)-containing extracts such as BSE have anti-inflammatory and immunomodulatory activity. In chronic schistosomiasis, the hepatic granuloma and fibrosis induced by egg deposition in the liver is the most serious pathological manifestations. However, little is known regarding the role of BAs in Schistosoma japonicum (S. japonicum) egg-induced liver granuloma and fibrosis. In order to investigate the effect of a water-soluble complex preparation of BSE, BSE-CD, on S. japonicum egg-induced liver pathology, liver granuloma and fibrosis were induced by infecting C57BL/6 mice with 18-22 cercariae of S. japonicum. S. japonicum cercariae infected mice were injected with BSE-CD at the onset of egg granuloma formation (early phase BSE-CD treatment after 4 weeks infection) or after the formation of liver fibrosis (late phase BSE-CD treatment after 7 weeks infection). Our data show that treatment of infected mice with BSE-CD significantly reduced both the extent of hepatic granuloma and fibrosis. Consistent with an inhibition of NF-κB signaling as evidenced by reduced IκB kinase (IKK) activation, the mRNA expression of VEGF (vascular endothelial growth factor, VEGF), TNF-α (tumor necrosis factor-alpha TNF-α) and MCP-1 (monocyte chemotactic protein 1, MCP-1) was decreased. Moreover, immunohistochemical analysis (IHC) revealed that the content of α-SMA in liver tissue of BSE-CD treated mice was dramatically decreased. Our findings suggest that BSE-CD treatment attenuates S. japonicum egg-induced hepatic granulomas and fibrosis, at least partly due to reduced NF-κB signaling and the subsequently decreased expression of VEGF, TNF-α, and MCP-1. Suppression of the activation of hepatic stellate cells (HSC) may also be involved in the therapeutic efficacy of BSE-CD.

Cellular and chemokine-mediated regulation in schistosome-induced hepatic pathology

In hepatic schistosomiasis, pathology arises when schistosome eggs become lodged in the host liver, evoking an interleukin 4 (IL-4)- and IL-13-mediated dominant CD4(+) Th2 immune response. This response leads to the development of granulomas and fibrosis, with eosinophils, neutrophils, macrophages, hepatic stellate cells, and lymphocytes all identified as major cellular contributors to these events. This review outlines the cellular and molecular mechanisms of hepatic schistosomiasis, with an emphasis on the major cellular components and their release of chemokines. The differences between Schistosoma mansoni- and Schistosoma japonicum-induced hepatic granuloma are also discussed. This comprehensive overview of the processes associated with hepatic schistosomiasis may provide new insights into improved treatment for both schistosomiasis and other granulofibrotic diseases.

The schistosoma granuloma: friend or foe?

Infection of man with Schistosoma species of trematode parasite causes marked chronic morbidity. Individuals that become infected with Schistosomes may develop a spectrum of pathology ranging from mild cercarial dermatitis to severe tissue inflammation, in particular within the liver and intestines, which can lead to life threatening hepatosplenomegaly. It is well established that the etiopathology during schistosomiasis is primarily due to an excessive or unregulated inflammatory response to the parasite, in particular to eggs that become trapped in various tissue. The eggs forms the foci of a classical type 2 granulomatous inflammation, characterized by an eosinophil-rich, CD4⁺ T helper (Th) 2 cell dominated infiltrate with additional infiltration of alternatively activated macrophages (M2). Indeed the sequela of the type 2 perioval granuloma is marked fibroblast infiltration and development of fibrosis. Paradoxically, while the granuloma is the cause of pathology it also can afford some protection, whereby the granuloma minimizes collateral tissue damage in the liver and intestines. Furthermore, the parasite is exquisitely reliant on the host to mount a granulomatous reaction to the eggs as this inflammatory response facilitates the successful excretion of the eggs from the host. In this focused review we will address the conundrum of the S. mansoni granuloma acting as both friend and foe in inflammation during infection.

A boswellic acid-containing extract attenuates hepatic granuloma in C57BL/6 mice infected with Schistosoma japonicum

Granuloma formation has been shown to be induced and elicited by schistosome egg antigens, and it finally develops into fibrosis in intestine and the liver. Hepatic fibrosis is the main cause of increased morbidity and mortality in humans infected with schistosomes. Boswellic acid (BA)-containing extracts such as extracts of the oleogum resin from Boswellia serrata (BSE) have anti-inflammatory and immunomodulatory activity. However, little is known about the role of such extracts in schistosome egg-induced granulomatous inflammation. In order to investigate the effect of a watersoluble cyclodextrin complex preparation of BSE (BSE-CD) on Schistosoma japonicum (S. japonicum) egg-induced liver granuloma, mice infected with S. japonicum cercariae were injected with BSE-CD during egg granuloma formation. The data showed that BSE-CD significantly reduced the size of liver granuloma and levels of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST); however, BSE-CD treatment had no effect on worm load and egg burden. The data also showed that BSE-CD significantly decreased the expression of leukotriene B(4) (LTB(4)) and prostaglandin E(2) (PGE(2)), as well as the expression of matrix metallopeptidase 9 (MMP-9) in liver both on the mRNA and protein level. Thus, BSE-CD can significantly attenuate S. japonicum egg-induced hepatic granuloma, which may be partly dependent on the downregulation of some biochemical mediators.

Cytokine and Chemokine Profile in Individuals with Different Degrees of Periportal Fibrosis due to Schistosoma mansoni Infection

Periportal fibrosis in schistosomiasis has been associated to the host immune response to parasite antigens. We evaluated the immune response in S. mansoni infected individuals with different degrees of periportal fibrosis. Cytokine and chemokines were measured in serum and in supernatants of PBMC cultures stimulated with the soluble adult worm (SWAP) or egg (SEA) antigens, using a sandwich ELISA. The levels of IL-5 in response to SEA were higher in individuals with moderate to severe fibrosis (310.9 pg/mL) compared to individuals without fibrosis (36.8 pg/mL; P = 0.0418). There was also a higher production of TNF-α in cultures stimulated with SWAP in patients with insipient fibrosis (1446 pg/mL) compared to those without fibrosis (756.1 pg/mL; P = 0.0319). The serum levels of IL-13 and MIP-1α were higher in subjects without fibrosis than in those with moderate to severe fibrosis. However a positive association between serum levels of IL-13, TNF-α, MIP-1α, and RANTES and S. mansoni parasite burden was found. From these data we conclude that IL-5 and TNF-α may participate in liver pathology in schistosomiasis. The positive association between IL-13, TNF-α, MIP-1α, and RANTES with parasite burden, however, might predict the development of liver pathology.

Granulocytes in helminth infection -- who is calling the shots?

Helminths are parasitic organisms that can be broadly described as “worms” due to their elongated body plan, but which otherwise differ in shape, development, migratory routes and the predilection site of the adults and larvae. They are divided into three major groups: trematodes (flukes), which are leaf-shaped, hermaphroditic (except for blood flukes) flatworms with oral and ventral suckers; cestodes (tapeworms), which are segmented, hermaphroditic flatworms that inhabit the intestinal lumen; and nematodes (roundworms), which are dioecious, cylindrical parasites that inhabit intestinal and peripheral tissue sites. Helminths exhibit a sublime co-evolution with the host´s immune system that has enabled them to successfully colonize almost all multicellular species present in every geographical environment, including over two billion humans. In the face of this challenge, the host immune system has evolved to strike a delicate balance between attempts to neutralize the infectious assault versus limitation of damage to host tissues. Among the most important cell types during helminthic invasion are granulocytes: eosinophils, neutrophils and basophils. Depending on the specific context, these leukocytes may have pivotal roles in host protection, immunopathology, or facilitation of helminth establishment. This review provides an overview of the function of granulocytes in helminthic infections.

Experimental infection with Schistosoma mansoni in CCR5-deficient mice is associated with increased disease severity, as CCR5 plays a role in controlling granulomatous inflammation

The plasma level of the chemokine CCL3 is elevated in patients with chronic severe schistosomiasis mansoni. We have previously shown that CCL3(-/-) mice with experimental infection showed diminished pathology and worm burden compared to those of wild-type (WT) mice. To elucidate further the role of CC chemokines during schistosomiasis mansoni infection, we evaluated the course of infection in C57BL/6J mice deficient in CCR5, one of the receptors for CCL3. The CCR5 deficiency proved to be remarkably deleterious to the host, since mortality rates reached 70% at 14 weeks postinfection in CCR5(-/-) mice and 19% in WT mice. The increased lethality was not associated with an increased parasite burden, since similar numbers of eggs and adult worms were found in mice from both groups. Liver granulomas of chronically infected CCR5(-/-) mice were larger and showed greater numbers of cells and collagen deposition than liver granulomas from WT mice. This was associated with higher levels of production of intereleukin-5 (IL-5), IL-13, CCL3, and CCL5 in infected CCR5(-/-) mice than in infected WT mice. Moreover, at 8 weeks after infection, just before changes in pathology and mortality, the numbers of FoxP3-positive cells were lower in liver granulomas of CCR5(-/-) mice than in WT mice. In conclusion, the CCR5 deletion is deleterious to mice infected with Schistosoma mansoni, and this is associated with enhanced fibrosis and granulomatous inflammation.

Immunopathogenesis of human schistosomiasis

Schistosomiasis continues to be a significant cause of parasitic morbidity and mortality worldwide. This review considers the basic features of the pathology and clinical outcomes of hepatointestinal and genitourinary schistosomiasis, presents an overview of the numerous studies on animal models that have clarified many of the immunopathological features, and provides insight into our current understanding of the immunopathogenesis and genetic control of human schistosomiasis. In murine schistosomiasis, pathology is induced by a CD4(+) Th2 driven granulomatous response directed against schistosome eggs lodged in the host liver. The Th2 cytokines IL-4 and IL-13 drive this response, whereas IL-10, IL13Ralpha2, IFN-gamma and a subset of regulatory T-cells act to limit schistosome induced pathology. A variety of cell types including hepatic stellate cells, alternatively activated macrophages and regulatory T-cells have also been implicated in the pathogenesis of schistosomiasis. Current knowledge suggests the immunopathogenic mechanisms underlying human schistosomiasis are likely to be similar. The review also considers the future development of anti-pathology schistosome vaccines. As fibrosis is an important feature of many other diseases such as Crohn's disease and sarcoidosis, a comprehensive understanding of the cellular and molecular mechanisms involved in schistosomiasis may also ultimately contribute to the development an effective disease intervention strategy for other granulofibrotic diseases.

Common promoter deletion is associated with 3.9-fold differential transcription of ovine CCR5 and reduced proviral level of ovine progressive pneumonia virus

Chemokine (C-C motif) Receptor 5 (CCR5) is a chemokine receptor that regulates immune cell recruitment in inflammation and serves as a coreceptor for human immunodeficiency virus (HIV). A human CCR5 coding deletion (termed delta-32) results in strong resistance to HIV infection, and sequence variants in CCR5 regulatory regions have been implicated in delayed progression to acquired immune deficiency syndrome. Both ovine progressive pneumonia virus (OPPV), also known as maedi-visna, and HIV are macrophage-tropic lentiviruses, have similar genomic structures, and cause lifelong persistent host infection, suggesting CCR5 may have a role in regulating OPPV provirus levels. Therefore, the ovine CCR5 genomic sequence was determined, and sequence variants were obtained from the open reading frame and surrounding regulatory sites. One CCR5 variant contained a 4-base deletion within a binding site for octamer transcription factors in the promoter region. A test for differential transcription from each allele in heterozygous animals showed a 3.9-fold transcription difference (P < 0.0001). OPPV proviral levels were also measured in 351 naturally exposed Rambouillet, Polypay and Columbia sheep. Deletion homozygotes showed reduced OPPV proviral levels among these animals (P < 0.01). The association of this CCR5 promoter deletion with OPPV levels will need to be validated in additional populations before the deletion can be recommended for widespread use in marker-assisted selection. However, because of the large impact on transcription and because CCR5 has roles in inflammation, recruitment of effector cells, and cell-mediated immunity, this deletion may play a role in the control of infections of many diverse pathogens of sheep.