Release of stress proteins from Mesocestoides corti is a brefeldin A-inhibitable process: evidence for active export of stress proteins

Immunity and immune modulation elicited by the larval cestode Mesocestoides vogae and its products

Larval cestodes (metacestodes) induce long-lasting infections leading to considerable pathology in humans and livestock. Their survival is typically associated with Th2-biased immune responses and immunosuppressive effects and depends on the parasite's ability to excrete/secrete antigens with immunoregulatory properties. Here, Mesocestoides vogae, a natural parasite of mice, is proposed as a new model species for the identification and characterization of cestode-derived immunomodulatory factors. We followed the kinetics of immune parameters after infection with M. vogae or exposure to their excretory/secretory (ES) products in a permissive strain of mice. Besides, a dominant IL-10 production and accumulation of macrophages and eosinophils expressing mRNA for Fizz-1, YM1 and Arg-1, mice showed minimal IFN-γ and transient IL-4 production at early time points with a complete loss at later stages of infection. We found that serum-free ES products without host contamination directly induced M2 macrophages and suppressed IFN-γ production in vivo and in vitro. This study highlights the use of the M. vogae as a cestode infection model and its ES products as a valuable tool for the identification of new therapeutic targets for the control of larval cestodiasis.

Recent advances in Echinococcus genomics and stem cell research

Alveolar and cystic echinococcosis, caused by the metacestode larval stages of the tapeworms Echinococcus multilocularis and Echinococcus granulosus, respectively, are life-threatening diseases and very difficult to treat. The introduction of benzimidazole-based chemotherapy, which targets parasite β-tubulin, has significantly improved the life-span and prognosis of echinococcosis patients. However, benzimidazoles show only parasitostatic activity, are associated with serious adverse side effects and have to be administered for very long time periods, underlining the need for new drugs. Very recently, the nuclear genomes of E. multilocularis and E. granulosus have been characterised, revealing a plethora of data for gaining a deeper understanding of host-parasite interaction, parasite development and parasite evolution. Combined with extensive transcriptome analyses of Echinococcus life cycle stages these investigations also yielded novel clues for targeted drug design. Recent years also witnessed significant advancements in the molecular and cellular characterisation of the Echinococcus 'germinative cell' population, which forms a unique stem cell system that differs from stem cells of other organisms in the expression of several genes associated with the maintenance of pluripotency. As the only parasite cell type capable of undergoing mitosis, the germinative cells are central to all developmental transitions of Echinococcus within the host and to parasite expansion via asexual proliferation. In the present article, we will briefly introduce and discuss recent advances in Echinococcus genomics and stem cell research in the context of drug design and development. Interestingly, it turns out that benzimidazoles seem to have very limited effects on Echinococcus germinative cells, which could explain the high recurrence rates observed after chemotherapeutic treatment of echinococcosis patients. This clearly indicates that future efforts into the development of parasitocidal drugs should also target the parasite's stem cell system.

Pediatric Sepsis - Part V: Extracellular Heat Shock Proteins: Alarmins for the Host Immune System

Heat shock proteins (HSPs) are molecular chaperones that facilitate the proper folding and assembly of nascent polypeptides and assist in the refolding and stabilization of damaged polypeptides. Through these largely intracellular functions, the HSPs maintain homeostasis and assure cell survival. However, a growing body of literature suggests that HSPs have important effects in the extracellular environment as well. Extracellular HSPs are released from damaged or stressed cells and appear to act as local "danger signals" that activate stress response programs in surrounding cells. Importantly, extracellular HSPs have been shown to activate the host innate and adaptive immune response. With this in mind, extracellular HSPs are commonly included in a growing list of a family of proteins known as danger-associated molecular patterns (DAMPs) or alarmins, which trigger an immune response to tissue injury, such as may occur with trauma, ischemia-reperfusion injury, oxidative stress, etc. Extracellular HSPs, including Hsp72 (HSPA), Hsp27 (HSPB1), Hsp90 (HSPC), Hsp60 (HSPD), and Chaperonin/Hsp10 (HSPE) are especially attractrive candidates for DAMPs or alarmins which may be particularly relevant in the pathophysiology of the sepsis syndrome.

Differential release and phagocytosis of tegument glycoconjugates in neurocysticercosis: implications for immune evasion strategies

Neurocysticercosis (NCC) is an infection of the central nervous system (CNS) by the metacestode of the helminth Taenia solium. The severity of the symptoms is associated with the intensity of the immune response. First, there is a long asymptomatic period where host immunity seems incapable of resolving the infection, followed by a chronic hypersensitivity reaction. Since little is known about the initial response to this infection, a murine model using the cestode Mesocestoides corti (syn. Mesocestoides vogae) was employed to analyze morphological changes in the parasite early in the infection. It was found that M. corti material is released from the tegument making close contact with the nervous tissue. These results were confirmed by infecting murine CNS with ex vivo–labeled parasites. Because more than 95% of NCC patients exhibit humoral responses against carbohydrate-based antigens, and the tegument is known to be rich in glycoconjugates (GCs), the expression of these types of molecules was analyzed in human, porcine, and murine NCC specimens. To determine the GCs present in the tegument, fluorochrome-labeled hydrazides as well as fluorochrome-labeled lectins with specificity to different carbohydrates were used. All the lectins utilized labeled the tegument. GCs bound by isolectinB4 were shed in the first days of infection and not resynthesized by the parasite, whereas GCs bound by wheat germ agglutinin and concavalinA were continuously released throughout the infectious process. GCs bound by these three lectins were taken up by host cells. Peanut lectin-binding GCs, in contrast, remained on the parasite and were not detected in host cells. The parasitic origin of the lectin-binding GCs found in host cells was confirmed using antibodies against T. solium and M. corti. We propose that both the rapid and persistent release of tegumental GCs plays a key role in the well-known immunomodulatory effects of helminths, including immune evasion and life-long inflammatory sequelae seen in many NCC patients.

Neurocysticercosis (NCC) is a disease caused by the larval form of a tapeworm parasite that preferentially migrates to the brain. It is characterized by a long asymptomatic period thought to result from the parasite's ability to evade host immunity. To date, the mechanisms of host–parasite interaction before symptoms develop remain unknown. In this study we evaluate by multiple immunofluorescent techniques distinct stages of the infection, making use of a murine model that closely resembles the disease process observed in humans. We discovered that the array of molecules secreted by the parasite varies according to the phase of infection studied. Early in infection, the parasite permanently sheds distinct molecules, allowing a rapid establishment in the brain. As the infection ensues, the continuous release of different molecules appears to facilitate the persistence of the parasite by downregulating molecules involved in its recognition and destruction. Loss of such molecules when the parasite dies after drug treatment may explain sudden inflammatory responses in patients. Characterization of these molecules will lead to advances in our understanding of the complex immunoregulatory mechanisms used by parasites and to new approaches for therapeutic strategies.

Heat shock response and acute lung injury

All cells respond to stress through the activation of primitive, evolutionarily conserved genetic programs that maintain homeostasis and assure cell survival. Stress adaptation, which is known in the literature by a myriad of terms, including tolerance, desensitization, conditioning, and reprogramming, is a common paradigm found throughout nature, in which a primary exposure of a cell or organism to a stressful stimulus (e.g., heat) results in an adaptive response by which a second exposure to the same stimulus produces a minimal response. More interesting is the phenomenon of cross-tolerance, by which a primary exposure to a stressful stimulus results in an adaptive response whereby the cell or organism is resistant to a subsequent stress that is different from the initial stress (i.e., exposure to heat stress leading to resistance to oxidant stress). The heat shock response is one of the more commonly described examples of stress adaptation and is characterized by the rapid expression of a unique group of proteins collectively known as heat shock proteins (also commonly referred to as stress proteins). The expression of heat shock proteins is well described in both whole lungs and in specific lung cells from a variety of species and in response to a variety of stressors. More importantly, in vitro data, as well as data from various animal models of acute lung injury, demonstrate that heat shock proteins, especially Hsp27, Hsp32, Hsp60, and Hsp70 have an important cytoprotective role during lung inflammation and injury.

Periplasmic localization of a GroES homologue in Escherichia coli transformed with groESx cloned from Legionella-like endosymbionts in Amoeba proteus

Escherichia coli MC4100 transformed with a groE homologous operon cloned from X-bacteria accumulated large amounts of the gene product when cultured at 30 or 37 degrees C. Heat shock for 10-30 min at 42 degrees C or ethanol (5%) shock for 2 h increased GroESx levels to about twice that in E. coli grown at 30 degrees C. The subcellular localization of GroESx in transformed E. coli was determined by several subcellular fractionation methods, by the analysis of extracted proteins in SDS polyacrylamide gels and by assays of marker enzymes. The GroESx protein was detected in both the periplasmic and cytoplasmic extracts and a large amount of the protein was accumulated in the periplasm. The GroEL protein and recombinant beta-galactosidase were exclusively localized in the cytoplasmic fraction, eliminating the possibility that periplasmic GroESx might be due to simple overproduction. N-terminal amino acid sequencing confirmed that the protein resolved on a 2-D gel was GroESx. This work represents the first report of the periplasmic location of GroES homologues in E. coli.

Plasma membrane expression of heat shock protein 60 in vivo in response to infection

Heat shock protein 60 (hsp60) is constitutively expressed in the mitochondria of eukaryotic cells. However, it has been identified in other subcellular compartments in several disease states and in transformed cells, and it is an immunogenic molecule in various infectious and autoimmune diseases. To better understand the factors that influence expression of hsp60 in normal cells in vivo, we analyzed its cellular and subcellular distribution in mice infected with the intracellular bacterium Listeria monocytogenes. Western blotting of subcellular fractionated spleen cells showed that although endogenous hsp60 was restricted to the mitochondria in noninfected animals, it was associated with the plasma membrane as a result of infection. The low levels of plasma membrane-associated hsp60 seen in the livers in noninfected animals subsequently increased during infection. Plasma membrane hsp60 expression did not correlate with bacterial growth, being most evident during or after bacterial clearance and persisting at 3 weeks postinfection. Using flow cytometry, we determined that Mac-1(+), T-cell receptor gammadelta(+), and B220(+) cells represented the major Hsp60(+) populations in spleens of infected mice. By contrast, B220(+) cells were the predominant hsp60(+) population in livers of infected mice. Of the immune cells analyzed, the kinetic profile of the gammadelta T-cell response most closely matched that of hsp60 expression in both the spleen and liver. Collectively, these findings show that during infection hsp60 can be localized to the plasma membrane of viable cells, particularly antigen-presenting cells, providing a means by which hsp60-reactive lymphocytes seen in various infectious disease and autoimmune disorders may be generated and maintained.

Heat-shock proteins, molecular chaperones, and the stress response: evolutionary and ecological physiology

Molecular chaperones, including the heat-shock proteins (Hsps), are a ubiquitous feature of cells in which these proteins cope with stress-induced denaturation of other proteins. Hsps have received the most attention in model organisms undergoing experimental stress in the laboratory, and the function of Hsps at the molecular and cellular level is becoming well understood in this context. A complementary focus is now emerging on the Hsps of both model and nonmodel organisms undergoing stress in nature, on the roles of Hsps in the stress physiology of whole multicellular eukaryotes and the tissues and organs they comprise, and on the ecological and evolutionary correlates of variation in Hsps and the genes that encode them. This focus discloses that (a) expression of Hsps can occur in nature, (b) all species have hsp genes but they vary in the patterns of their expression, (c) Hsp expression can be correlated with resistance to stress, and (d) species' thresholds for Hsp expression are correlated with levels of stress that they naturally undergo. These conclusions are now well established and may require little additional confirmation; many significant questions remain unanswered concerning both the mechanisms of Hsp-mediated stress tolerance at the organismal level and the evolutionary mechanisms that have diversified the hsp genes.

Development of an Animal Model for Neurocysticercosis: Immune Response in the Central Nervous System Is Characterized by a Predominance of γδ T Cells

Neurocysticercosis is the most common parasitic disease of the central nervous system worldwide. It is caused by the metacestode form of the helminth Taenia solium. Study of the immune response in the human brain has been limited by the chronic progression of the disease, the influence of corticosteroid treatment, and the scarcity of patients who undergo surgical intervention. To better understand the immune response and associated pathology in neurocysticercosis, a mouse model was developed by intracranial infection of BALB/c mice with Mesocestoides corti, a cestode organism related to T. solium. The immune response reveals the presence of abundant inflammatory infiltrates appearing as early as 2 days postinfection in extraparenchymal regions. In contrast, infiltration of immune cells into parenchymal tissue is significantly delayed. There is a natural progression of innate (neutrophils and macrophages), early induced (NK cells and γδ T cells), and adaptive immune responses (αβ T cells and B cells) in infected mice. γδ T cells are the predominant T cell population. A cell-mediated Th1 pathway of cytokine expression is evident in contrast to the previously described Th2 phenotype induced in the periphery.

Immune responses to stress proteins: applications to infectious disease and cancer

Heat shock proteins, or stress proteins have been identified as part of a highly conserved cellular defence mechanism mediated by multiple, distinct gene families and corresponding gene products. As intracellular chaperones, stress proteins participate in many essential biochemical pathways of protein maturation and function active during times of stress and during normal cellular homeostasis. In addition to their well-characterized role as protein chaperones, stress proteins are now realized to possess another important biological property: immunogenicity. Stress proteins are now understood to play a fundamental role in immune surveillance of infection and malignancy and this body of basic research has provided a framework for their clinical application. As key targets of both humoral and cellular immunity during infection, stress proteins have accordingly received considerable research interest as prophylactic vaccines for infectious disease applications. The unique and potent immunostimulatory properties of stress proteins have similarly been applied to the development of new approaches to cancer therapy, including both protein and gene-based modalities.

Activity-dependent neurotrophic factor (ADNF). An extracellular neuroprotective chaperonin?

To understand and intervene in neuronal cell death, intensive investigations have been directed at the discovery of intracellular and extracellular factors that provide natural neuroprotection. This goal has fundamental importance for both rational strategies for the treatment of neurodegenerative diseases and also the delineation of molecular mechanisms that regulate nervous system differentiation and growth. We have discovered a potential interface among these fields of research with activity-dependent neurotrophic factor (ADNF), a protein containing sequence homologies to intracellular stress proteins that is found in the extracellular milieu of astroglial cells incubated with the neuropeptide vasoactive intestinal peptide (VIP). Femtomolar concentrations of ADNF and a short peptide sequence derived from it (a peptidergic active site) protected neurons from death associated with a broad range of toxins, including those related to Alzheimer's disease, the human immunodeficiency virus, excito-toxicity, and electrical blockade. Because the activity of the protein was mimicked by a short peptide fragment, this peptide is now proposed as a lead compound for drug development against neurodegeneration.

Elevated levels of Legionella pneumophila stress protein Hsp60 early in infection of human monocytes and L929 cells correlate with virulence

Legionella pneumophila 2064 was selectively radiolabelled in mouse L929 cells and human monocytes to identify proteins expressed early in the course of infection. Polypeptide profiles (sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography) of adherent or intracellular bacteria indicated that a 60-kDa stress protein (Hsp60) was preferentially synthesized. Hsp60 synthesis was not induced by medium alone. The synthesis of many polypeptides, including OmpS (major outer membrane protein), diminished over the 1-h period postinfection. However, by 17 h postinfection OmpS and Hsp60 were the dominant proteins synthesized by 2064. To establish whether induction of Hsp60 was a correlate of virulence, an isogenic avirulent strain (2064M) of 2064 was isolated following selection on a nonpermissive medium. 2064M did not exhibit a stress response when adherent or intracellular in L929 cells or in human monocytes and failed to abrogate phagosome-lysosome fusion. When grown in vitro, 2064M exhibited no deficiencies in the heat shock response and its polypeptide profile resembled that of 2064. Immunogold electron microscopy was used to localize Hsp60 in L. pneumophila-infected L929 cells. There was an increase in the number of gold particles associated with phagosomes for phagosomes harboring single 2064 bacteria compared with those harboring 2064M. Moreover, by 1 h postinfection, a sixfold increase in the number of gold spheres associated with the membranes of phagosomes was observed for phagosomes harboring 2064 compared with those harboring 2064M. These studies indicate that virulent, but not NaCl-tolerant avirulent, strains of L. pneumophila respond to host-cell-associated environmental signals early in the course of infection. This response includes increased synthesis and possibly extracellular secretion of Hsp60 concomitant with repression of the expression of other genes, including ompS.

How schistosomes profit from the stress responses they elicit in their hosts

Results obtained with the model Trichobilharzia ocellata-Lymnaea stagnalis have confirmed the hypothesis that the physiological effects evoked by schistosomes in their snail host--castration and giant growth--are brought about by them interfering with the neuroendocrine systems (NES) regulating the physiological processes concerned. As soon as differentiating cercariae are present in the daughter sporocysts a factor can be detected in the haemolymph of the snail host, called schistosomin, which acts both at the central and the peripheral parts of the NES involved in regulation of reproduction and growth. Schistosomin appears to be a host-derived factor, which is probably released by cells of the internal defence system, the haemocytes, and by connective tissue cells, the telo-glial cells. It meets the criteria of having a cytokine-like function although its molecular structure does not show sequence homology with any of the vertebrate-type cytokines identified to date. Its cytokine nature explains why schistosomin can interfere with different neuroendocrine regulatory systems both at the central and peripheral--target--level, namely after binding to its own receptor. Schistosomin is probably not only responsible for the effects exerted by the parasite on female reproduction but also for those on male reproduction and on growth so that energy and space become available for the continuous production of cercariae. The nature of the humoral cercarial factor, which induces schistosomin release, is as yet unknown. Based on its hydrophobic character and on the fact that it can pass through the wall of the daughter sporocyst, it is supposed to be a diffusible molecule or a protonephridial excretion product. It does not seem to be a vertebrate-type steroid, an ecdysteroid or an eicosanoid. Results obtained in vitro have indicated that schistosomin might have a suppressive effect on haemocyte activity. Plasma from snails 5-6 weeks post-exposure showed a tendency to inhibit phagocytic activity of haemocytes from non-infected snails, that is preparatory to the escape and migration of cercariae. Once shedding has started this effect of schistosomin is overrruled by a strong activation of haemocyte activity coinciding with the tissue damage that the cercariae cause in the host. The cercariae escape from being attacked by masking their surface coat with host molecules. As the physiological effects caused by schistosomes resemble those observed during stress in mammals, experiments were carried out to find out whether schistosomin is also released in non-parasitized snails during stress resulting in an inhibiting effect on reproduction.(ABSTRACT TRUNCATED AT 400 WORDS)