Therapeutic Potential of Natural Products in the Treatment of Schistosomiasis.

It is estimated that 250 million people worldwide are affected by schistosomiasis. Disease transmission is related to the poor sanitation and hygiene habits that affect residents of impoverished regions in tropical and subtropical countries. The main species responsible for causing disease in humans are Schistosoma Mansoni, S. japonicum, and S. haematobium, each with different geographic distributions. Praziquantel is the drug predominantly used to treat this disease, which offers low effectiveness against immature and juvenile parasite forms. In addition, reports of drug resistance prompt the development of novel therapeutic approaches. Natural products represent an important source of new compounds, especially those obtained from plant sources. This review compiles data from several in vitro and in vivo studies evaluating various compounds and essential oils derived from plants with cercaricidal and molluscicidal activities against both juvenile and adult forms of the parasite. Finally, this review provides an important discussion on recent advances in molecular and computational tools deemed fundamental for more rapid and effective screening of new compounds, allowing for the optimization of time and resources.

Association of Cardiac Galectin-3 Expression, Myocarditis, and Fibrosis in Chronic Chagas Disease Cardiomyopathy.

Chronic Chagas disease cardiomyopathy, caused by Trypanosoma cruzi infection, is a major cause of heart failure in Latin America. Galectin-3 (Gal-3) has been linked to cardiac remodeling and poor prognosis in heart failure of different etiologies. Herein, we investigated the involvement of Gal-3 in the disease pathogenesis and its role as a target for disease intervention. Gal-3 expression in mouse hearts was evaluated during T. cruzi infection by confocal microscopy and flow cytometry analysis, showing a high expression in macrophages, T cells, and fibroblasts. In vitro studies using Gal-3 knockdown in cardiac fibroblasts demonstrated that Gal-3 regulates cell survival, proliferation, and type I collagen synthesis. In vivo blockade of Gal-3 with N-acetyl-d-lactosamine in T. cruzi-infected mice led to a significant reduction of cardiac fibrosis and inflammation in the heart. Moreover, a modulation in the expression of proinflammatory genes in the heart was observed. Finally, histological analysis in human heart samples obtained from subjects with Chagas disease who underwent heart transplantation showed the expression of Gal-3 in areas of inflammation, similar to the mouse model. Our results indicate that Gal-3 plays a role in the pathogenesis of experimental chronic Chagas disease, favoring inflammation and fibrogenesis. Moreover, by demonstrating Gal-3 expression in human hearts, our finding reinforces that this protein could be a novel target for drug development for Chagas cardiomyopathy.

Bone marrow-derived cells migrate to the liver and contribute to the generation of different cell types in chronic Schistosoma mansoni infection.

The main pathogenic event caused by Schistosoma mansoni infection is characterized by a granulomatous inflammatory reaction around parasite eggs and fibrosis in the liver. We have previously shown that transplantation of bone marrow cells (BMC) promotes a reduction in liver fibrosis in chronically S. mansoni-infected mice. Here we investigated the presence and phenotype of bone marrow-derived cells in livers of S. mansoni-infected mice. During the chronic phase of infection, C57BL/6 mice had an increased number of circulating mesenchymal stem cells and endothelial progenitor cells in the peripheral blood when compared to uninfected controls. In order to investigate the fate of BMC in the liver, we generated bone marrow chimeric mice by transplanting BMC from transgenic green fluorescent protein (GFP) mice into lethally irradiated wild-type C57BL/6 mice. S. mansoni-infected chimeric mice did not demonstrate increased mortality and developed similar liver histopathological features, when compared to wild-type S. mansoni-infected mice. GFP(+) bone marrow-derived cells were found in the liver parenchyma, particularly in periportal regions. CD45(+)GFP(+) cells were found in the granulomas. Flow cytometry analysis of digested liver tissue characterized GFP(+) cells as lymphocytes, myeloid cells and stem cells. GFP(+) cells were also found in areas of collagen deposition, although rare GFP(+) cells expressed the myofibroblast cell marker α-SMA. Additionally GFP(+) endothelial cells (co-stained with von Willebrand factor) were frequently observed, while BMC-derived hepatocytes (GFP(+) albumin(+) cells) were sparsely found in the liver of chimeric mice chronically infected with S. mansoni. In conclusion, BMC are recruited to the liver during chronic experimental infection with S. mansoni and contribute to the generation of different cell types involved, not only in disease pathogenesis, but possibly in liver regeneration and repair.

Early transplantation of bone marrow mononuclear cells promotes neuroprotection and modulation of inflammation after status epilepticus in mice by paracrine mechanisms.

Status epilepticus (SE) is a severe clinical manifestation of epilepsy associated with intense neuronal loss and inflammation, two key factors involved in the pathophysiology of temporal lobe epilepsy. Bone marrow mononuclear cells (BMMC) attenuated the consequences of pilocarpine-induced SE, including neuronal loss, in addition to frequency and duration of seizures. Here we investigated the effects of BMMC transplanted early after the onset of SE in mice, as well as the involvement of soluble factors produced by BMMC in the effects of the cell therapy. Mice were injected with pilocarpine for SE induction and randomized into three groups: transplanted intravenously with 1 × 10(7) BMMC isolated from GFP transgenic mice, injected with BMMC lysate, and saline-treated controls. Cell tracking, neuronal counting in hippocampal subfields and cytokine analysis in the serum and brain were performed. BMMC were found in the brain 4 h following transplantation and their numbers progressively decreased until 24 h following transplantation. A reduction in hippocampal neuronal loss after SE was found in mice treated with live BMMC and BMMC lysate when compared to saline-treated, SE-induced mice. Moreover, the expression of inflammatory cytokines IL-1ß, TNF-α, IL-6 was decreased after injection of live BMMC and to a lesser extent, of BMMC lysate, when compared to SE-induced controls. In contrast, IL-10 expression was increased. Analysis of markers for microglia activation demonstrated a reduction of the expression of genes related to type 1-activation. BMMC transplantation promotes neuroprotection and mediates anti-inflammatory effects following SE in mice, possibly through the secretion of soluble factors.

Transplantation of bone marrow mononuclear cells decreases seizure incidence, mitigates neuronal loss and modulates pro-inflammatory cytokine production in epileptic rats.

Approximately 30% of patients with mesial temporal lobe epilepsy do not respond to treatment with antiepileptic drugs. We have previously shown that transplantation of mononuclear bone marrow cells (BMC) has an anticonvulsant effect in acute epilepsy. Here, we used pilocarpine to induce epilepsy in rats and studied the effects of BMC injected intravenously either at the onset of seizures or after 10 months of recurrent seizures. BMC effectively decreased seizure frequency and duration. In addition, decreased levels of proinflammatory cytokines (TNF-α, IL-1ß and IL-6) and increased levels of anti-inflammatory cytokine (IL-10) were observed in the brain and serum of BMC-treated rats. Transplants performed at seizure-onset protected against pilocarpine-induced neuronal loss and gliosis and stimulated the proliferation of new neurons in epileptic rats. Our data demonstrate that BMC transplantation has potent therapeutic effects and could be a potential therapy for clinically intractable epilepsies.

Reduction of galectin-3 expression and liver fibrosis after cell therapy in a mouse model of cirrhosis.

BACKGROUND AIMS: Cirrhosis, end-stage liver disease, is caused by different mechanisms of injury, associated with persistent inflammation. Galectin-3 is an important regulator of fibrosis that links chronic inflammation to fibrogenesis. We investigated the role of bone marrow cell (BMC) transplantation in chronic inflammation and hepatic fibrosis. METHODS: Liver cirrhosis was induced by administration of carbon tetrachloride and ethanol to wild-type C57BL/6 or bone marrow chimeric mice. Bone marrow chimeras were generated by lethal irradiation and transplantation with BMC obtained from green fluorescent protein (GFP(+) )donors. Wild-type cirrhotic mice were transplanted with BMC without irradiation. Livers from chimeras and cirrhotic transplanted mice were obtained for evaluation of inflammation, fibrosis and regulatory factors [galectin-3, matrix metallopeptidase (MMP)-9, tissue inhibitor of metalloproteinase (TIMP)-1 and transforming growth factor (TGF)-ß]. RESULTS: The development of cirrhosis was associated with increased expression of galectin-3 by F4/80(+) cells and intense migration of BMC to the liver. Furthermore, when transplanted after the establishment of cirrhosis, BMC also migrated to the liver and localized within the fibrous septa. Two months after BMC therapy, cirrhotic mice had a significant reduction in liver fibrosis and expression of type I collagen. We did not find any difference in levels of TGF-ß, TIMP-1 and MMP-9 between saline and BMC groups. However, the numbers of inflammatory cells, phagocytes and galectin-3(+) cells were markedly lower in the livers of cirrhotic mice treated with BMC. CONCLUSIONS: Our results demonstrate an important role for BMC in the regulation of liver fibrosis and that transplantation of BMC can accelerate fibrosis regression through modulatory mechanisms.

Phagocytosis is inhibited by autophagic induction in murine macrophages.

Recent studies have demonstrated that communication takes place between the autophagic and phagocytic pathways, indicating that the convergence of these two pathways plays an important role in the innate immune response against intracellular microbes. The present study investigated the effect of autophagic induction on the phagocytic capacity of murine macrophages. Autophagy induced by physiological and pharmacological means was shown to reduce the phagocytic capacity of murine macrophages, regardless of cell origin or the nature of the phagocytosed particles themselves. This autophagic inhibitory effect on phagocytosis was shown to be an early and reversible event that results in no loss of cell viability. Furthermore, the data presented herein demonstrate that the induction of autophagy does not affect a macrophage's capacity to recognize and bind to particles, indicating that autophagy does not inhibit the particle recognition process, even though particle internalization is suppressed. The findings herein support the notion that phagocytosis and autophagy may be interdependent and complementary processes.

Generation of three control iPS cell lines for sickle cell disease studies by reprogramming erythroblasts from individuals without hemoglobinopathies.

Sickle cell disease (SCD) is one of the most prevalent and severe monogenetic disorders. Previously, we generated iPS cell lines from SCD patients. Here, we generated iPS cell lines from three age-, ethnicity- and gender-matched healthy individuals as control cell lines. Cell reprogramming was performed using erythroblasts expanded from PBMC by a non-integrative method. SCD-iPSC controls expressed pluripotency markers, presented a normal karyotype, were able to differentiate into the three germ layers in embryoid body spontaneous differentiation and confirmed to be integration-free. The cell lines generated here may be used as matched healthy controls for SCD studies.

IGF-1 overexpression improves mesenchymal stem cell survival and promotes neurological recovery after spinal cord injury.

BACKGROUND: Survival and therapeutic actions of bone marrow-derived mesenchymal stem cells (BMMSCs) can be limited by the hostile microenvironment present during acute spinal cord injury (SCI). Here, we investigated whether BMMSCs overexpressing insulin-like growth factor 1 (IGF-1), a cytokine involved in neural development and injury repair, improved the therapeutic effects of BMMSCs in SCI. METHODS: Using a SCI contusion model in C57Bl/6 mice, we transplanted IGF-1 overexpressing or wild-type BMMSCs into the lesion site following SCI and evaluated cell survival, proliferation, immunomodulation, oxidative stress, myelination, and functional outcomes. RESULTS: BMMSC-IGF1 transplantation was associated with increased cell survival and recruitment of endogenous neural progenitor cells compared to BMMSC- or saline-treated controls. Modulation of gene expression of pro- and anti-inflammatory mediators was observed after BMMSC-IGF1 and compared to saline- and BMMSC-treated mice. Treatment with BMMSC-IGF1 restored spinal cord redox homeostasis by upregulating antioxidant defense genes. BMMSC-IGF1 protected against SCI-induced myelin loss, showing more compact myelin 28 days after SCI. Functional analyses demonstrated significant gains in BMS score and gait analysis in BMMSC-IGF1, compared to BMMSC or saline treatment. CONCLUSIONS: Overexpression of IGF-1 in BMMSC resulted in increased cell survival, immunomodulation, myelination, and functional improvements, suggesting that IGF-1 facilitates the regenerative actions of BMMSC in acute SCI.

Galectin-3 Knockdown Impairs Survival, Migration, and Immunomodulatory Actions of Mesenchymal Stromal Cells in a Mouse Model of Chagas Disease Cardiomyopathy.

Therapies based on transplantation of mesenchymal stromal cells (MSC) hold promise for the management of inflammatory disorders. In chronic Chagas disease cardiomyopathy (CCC), caused by chronic infection with Trypanosoma cruzi, the exacerbated immune response plays a critical pathophysiological role and can be modulated by MSC. Here, we investigated the role of galectin-3 (Gal-3), a beta-galactoside-binding lectin with several actions on immune responses and repair process, on the immunomodulatory potential of MSC. Gal-3 knockdown in MSC did not affect the immunophenotype or differentiation potential. However, Gal-3 knockdown MSC showed decreased proliferation, survival, and migration. Additionally, when injected intraperitoneally into mice with CCC, Gal-3 knockdown MSC showed impaired migration in vivo. Transplantation of control MSC into mice with CCC caused a suppression of cardiac inflammation and fibrosis, reducing expression levels of CD45, TNFα, IL-1ß, IL-6, IFNγ, and type I collagen. In contrast, Gal-3 knockdown MSC were unable to suppress the immune response or collagen synthesis in the hearts of mice with CCC. Finally, infection with T. cruzi demonstrated parasite survival in wild-type but not in Gal-3 knockdown MSC. These findings demonstrate that Gal-3 plays a critical role in MSC survival, proliferation, migration, and therapeutic potential in CCC.

Intramyocardial transplantation of cardiac mesenchymal stem cells reduces myocarditis in a model of chronic Chagas disease cardiomyopathy.

INTRODUCTION: New therapeutic options are necessary for patients with chronic Chagas disease, a leading cause of heart failure in Latin American countries. Stem cell therapy focused on improving cardiac function is a promising approach for treating heart disease. Here, we evaluated the therapeutic effects of cardiac mesenchymal stem cells (CMSCs) in a mouse model of chronic Chagas disease. METHODS: CMSCs were isolated from green fluorescent protein (GFP) transgenic C57BL/6 mouse hearts and tested for adipogenic, osteogenic, chondrogenic, endothelial, and cardiogenic differentiation potentials evaluated by histochemical and immunofluorescence techniques. A lymphoproliferation assay was performed to evaluate the immunomodulatory activity of CMSCs. To investigate the therapeutic potential of CMSCs, C57BL/6 mice chronically infected with Trypanosoma cruzi were treated with 106 CMSCs or saline (control) by echocardiography-guided injection into the left ventricle wall. All animals were submitted to cardiac histopathological and immunofluorescence analysis in heart sections from chagasic mice. Analysis by quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) was performed in the heart to evaluate the expression of cytokines involved in the inflammatory response. RESULTS: CMSCs demonstrated adipogenic, osteogenic, and chondrogenic differentiation potentials. Moreover, these cells expressed endothelial cell and cardiomyocyte features upon defined stimulation culture conditions and displayed immunosuppressive activity in vitro. After intramyocardial injection, GFP+ CMSCs were observed in heart sections of chagasic mice one week later; however, no observed GFP+ cells co-expressed troponin T or connexin-43. Histopathological analysis revealed that CMSC-treated mice had a significantly decreased number of inflammatory cells, but no reduction in fibrotic area, two months after treatment. Analysis by qRT-PCR demonstrated that cell therapy significantly decreased tumor necrosis factor-alpha expression and increased transforming growth factor-beta in heart samples. CONCLUSIONS: We conclude that the CMSCs exert a protective effect in chronic chagasic cardiomyopathy primarily through immunomodulation.

Transplantation of adipose tissue mesenchymal stem cells in experimental chronic chagasic cardiopathy.

BACKGROUND: Chagas disease, caused by the protozoan Trypanosoma cruzi, is a major cause of heart failure in Latin America. Tissue therapy has been investigated as a possible therapeutic option for patients with cardiovascular disease. OBJECTIVE: This study evaluated the effects of therapy with mesenchymal stem cells in an experimental model of chronic Chagasic cardiomyopathy. METHODS: C57BL/6 mice were infected with 1000 trypomastigotes from the Colombian strain of T. cruzi and, after six months of infection, were treated with mesenchymal human stem cells from adipose tissue (STAT) or with Dulbecco/Vogt modified Eagle's minimal essential medium - DMEM (control). The treated group received two intraperitoneal injections of STAT (1x10(6) cells/dose), with a month interval between the two doses. Before and after the first and second months of treatment, the chagasic and normal control animals underwent cardiopulmonary exercise testing and electrocardiography. All animals were sacrificed under anesthesia after two months of treatment for histopathological analysis of the heart. RESULTS: No improvement was observed in arrhythmias and cardiovascular function in the group of animals treated with STAT; however, sections of mice hearts in this group revealed a significant reduction in the number of inflammatory cells (p<0.0001) and areas of fibrosis (p<0.01) in comparison with chagasic animals treated with DMEM. CONCLUSION: Thus, it is concluded that administration of intraperitoneal STAT can reduce inflammation and fibrosis in the heart of mice chronically infected with T. cruzi; however, there were no effects on the cardiac function two months after transplantation.

Transplante de células mesenquimais de tecido adiposo na cardiopatia chagásica crônica experimental / Transplantation of adipose tissue mesenchymal stem cells in experimental chronic chagasic cardiopathy

FUNDAMENTO: A doença de Chagas, causada pelo protozoário Trypanosoma cruzi, é uma das mais importantes causas de insuficiência cardíaca na América Latina. A terapia celular vem sendo investigada como uma possível opção terapêutica para pacientes com doenças cardiovasculares. OBJETIVO: O objetivo deste estudo foi avaliar os efeitos da terapia com células-tronco mesenquimais em um modelo experimental de cardiomiopatia chagásica crônica. MÉTODOS: Camundongos C57BL/6 foram infectados com 1000 tripomastigotas da cepa Colombiana de T. cruzi e, após seis meses de infecção, foram tratados com células-tronco mesenquimais derivadas de tecido adiposo humano (CTTAs) ou com meio DMEM (controle). O grupo tratado recebeu duas injeções intraperitoneais de CTTAs (1x106 células / dose), com um mês de intervalo entre as duas doses. Antes e após 1 e 2 meses de tratamento, os animais chagásicos e controles normais foram submetidos à eletrocardiograma e teste ergoespirométrico. Todos os animais foram sacrificados sob anestesia após 2 meses de tratamento, para análise histopatológica do coração. RESULTADOS: Não foi observada melhora de arritmias e da função cardiovascular no grupo tratado com CTTAs, porém secções de corações de camundongos deste grupo apresentaram uma redução significativa do número de células inflamatórias (p < 0,0001) e da área de fibrose (p < 0,01) em comparação com animais chagásicos tratados com DMEM. CONCLUSÃO: Deste modo, conclui-se que a administração de CTTAs por via intraperitoneal é capaz de reduzir inflamação e fibrose no coração de camundongos cronicamente infectados por T. cruzi, porém não teve efeitos na função cardíaca dois meses após o transplante.

BACKGROUND: Chagas disease, caused by the protozoan Trypanosoma cruzi, is a major cause of heart failure in Latin America. Tissue therapy has been investigated as a possible therapeutic option for patients with cardiovascular disease. OBJECTIVE: This study evaluated the effects of therapy with mesenchymal stem cells in an experimental model of chronic Chagasic cardiomyopathy. METHODS: C57BL/6 mice were infected with 1000 trypomastigotes from the Colombian strain of T. cruzi and, after six months of infection, were treated with mesenchymal human stem cells from adipose tissue (STAT) or with Dulbecco/Vogt modified Eagle's minimal essential medium - DMEM (control). The treated group received two intraperitoneal injections of STAT (1x10(6) cells/dose), with a month interval between the two doses. Before and after the first and second months of treatment, the chagasic and normal control animals underwent cardiopulmonary exercise testing and electrocardiography. All animals were sacrificed under anesthesia after two months of treatment for histopathological analysis of the heart. RESULTS: No improvement was observed in arrhythmias and cardiovascular function in the group of animals treated with STAT; however, sections of mice hearts in this group revealed a significant reduction in the number of inflammatory cells (p<0.0001) and areas of fibrosis (p<0.01) in comparison with chagasic animals treated with DMEM. CONCLUSION: Thus, it is concluded that administration of intraperitoneal STAT can reduce inflammation and fibrosis in the heart of mice chronically infected with T. cruzi; however, there were no effects on the cardiac function two months after transplantation.

Changes induced in Biomphalaria glabrata (Say, 1818) following trials for artificial stimulation of its internal defense system.

Biomphalaria glabrata can react through different pathways to Schistosoma mansoni miracidium penetration, according to the degree of resistance/susceptibility presented by different snail strains, which is a genetically determined character, resistance being the dominant feature. However, it has been observed that previous susceptible snail strain may change its reactive behavior along the course of infection, exhibiting later a pattern of cercarial shedding and histopatopathological picture compatible with high resistance. Such observation suggests the possibility of B. glabrata to develop a sort of adaptative immunity face a schistosome infection. To explore on this aspect, the present investigation looked for the behavior of S. mansoni infection in B. glabrata previously subjected to different means of artificial stimulation of its internal defense system. Snails previously inoculated with irradiated miracídia (Group I); treated with S. mansoni antigens (Group II) or with a non-related parasite antigen (Group III) were challenged with 20 viable S. mansoni miracidia, and later looked for cercarial shedding and histopathologic changes at different times from exposition. Nodules of hemocyte accumulations were found at the site of antigen injection. These nodules resembled solid granulomas, and were larger and more frequent in snails injected with S. mansoni products as compared to those injected with Capillaria hepatica. However, the presence of such granulomas did not avoid the S. mansoni challenge infection from developing in a similar way as that seen in controls. The data are indicative that hemocytes are able to proliferate locally when stimulated, such capacity also remaining localized, not being shared by the population of hemocytes located elsewhere within the snail body.

A contribution to the pathobiology of Biomphalaria glabrata hemocytes.

This study attempts to investigate the relationship between the hemocytes in the two compartments: circulating peripheral lymph and the connective tissues. The hemocytes are compared with the vertebrate macrophages and constitute the principal line of defense against external aggression. The hemocytes were counted in circulating hemolymph and their phagocytic capability was evaluated in Schistosoma mansoni-infected Biomphalaria glabrata and the results were compared with those obtained from normal intact control snails. Although the number of circulating hemocytes revealed a mild increase in snails at the 6th week of infection, the overall findings were similar and pointed out that the cells in the two compartments are not functionally connected. However, the hemocytes found within the connective tissues of infected snails showed definite ultrastructural differences in the number and disposition of cytoplasmic prolongations and organelles in comparison with the hemocytes from non-infected snails. Histochemically, the staining for acid phosphatase activity served as a marker to hemocytes, sometimes being found in extracellular material at the foci of parasite-hemocyte interactions.

Células derivadas da medula óssea no reparo de lesões causadas por infecções parasitárias em camundongos quiméricos / Derived bone marrow cells to repair damage caused by parasitic infections in chimeric mice

A contribuição das células de medula óssea na regeneração de tecidos não hematopoiéticos tem sido intensamente investigada desde a descoberta de células-tronco multipotentes neste órgão. Estudos prévios tem demonstrado que células derivadas da medula óssea podem contribuir para a formação de novos hepatócitos e cardiomiócitos. No presente estudo avaliamos a participação endógena das células-tronco de medula óssea no processo de reparo de lesões teciduais na fase crônica da doença de Chagas e esquistossomose experimentalmente induzidas. Para isso, camundongos quiméricos de medula óssea foram gerados após irradiação com dose letal e posterior reconstituição com células de medula óssea provenientes de camundongos transgênicos para a proteína fluorescente verde (GFP)...

he contribution of bone marrow cells in non-hematopoietic tissue regeneration has been intensely investigated since the discovery of multipotent stem cells in this organ. Previous studies have shown that bone marrow derived cells may contribute to the formation of new hepatocytes and cardiomyocytes. In the present study, we evaluated the participation of endogenous bone marrow stem cells in the repair of tissue injury in experimentally induced chronic phases of Chagas disease and schistosomiasis. For this purpose, chimeric mice were generated from bone marrow after a lethal irradiation dose and subsequent reconstitution with bone marrow cells from green fluorescent protein (GFP) transgenic mice...

A contribution to the pathobiology of Biomphalaria glabrata hemocytes

This study attempts to investigate the relationship between the hemocytes in the two compartments: circulating peripheral lymph and the connective tissues. The hemocytes are compared with the vertebrate macrophages and constitute the principal line of defense against external aggression. The hemocytes were counted in circulating hemolymph and their phagocytic capability was evaluated in Schistosoma mansoni-infected Biomphalaria glabrata and the results were compared with those obtained from normal intact control snails. Although the number of circulating hemocytes revealed a mild increase in snails at the 6th week of infection, the overall findings were similar and pointed out that the cells in the two compartments are not functionally connected. However, the hemocytes found within the connective tissues of infected snails showed definite ultrastructural differences in the number and disposition of cytoplasmic prolongations and organelles in comparison with the hemocytes from non-infected snails. Histochemically, the staining for acid phosphatase activity served as a marker to hemocytes, sometimes being found in extracellular material at the foci of parasite-hemocyte interactions.

Changes induced in Biomphalaria glabrata (Say, 1818) following trials for artificial stimulation of its internal defense system

Biomphalaria glabrata can react through different pathways to Schistosoma mansoni miracidium penetration, according to the degree of resistance/susceptibility presented by different snail strains, which is a genetically determined character, resistance being the dominant feature. However, it has been observed that previous susceptible snail strain may change its reactive behavior along the course of infection, exhibiting later a pattern of cercarial shedding and histopatopathological picture compatible with high resistance. Such observation suggests the possibility of B. glabrata to develop a sort of adaptative immunity face a schistosome infection. To explore on this aspect, the present investigation looked for the behavior of S. mansoni infection in B. glabrata previously subjected to different means of artificial stimulation of its internal defense system. Snails previously inoculated with irradiated miracídia (Group I); treated with S. mansoni antigens (Group II) or with a non-related parasite antigen (Group III) were challenged with 20 viable S. mansoni miracidia, and later looked for cercarial shedding and histopathologic changes at different times from exposition. Nodules of hemocyte accumulations were found at the site of antigen injection. These nodules resembled solid granulomas, and were larger and more frequent in snails injected with S. mansoni products as compared to those injected with Capillaria hepatica. However, the presence of such granulomas did not avoid the S. mansoni challenge infection from developing in a similar way as that seen in controls. The data are indicative that hemocytes are able to proliferate locally when stimulated, such capacity also remaining localized, not being shared by the population of hemocytes located elsewhere within the snail body.