Host Immune Response In Order Research Articles

Current research on the interaction between Helicobacter pylori and macrophages.

Helicobacter pylori (H. pylori) is a gram-negative bacteria with a worldwide infection rate of 50%, known to induce gastritis, ulcers and gastric cancer. The interplay between H. pylori and immune cells within the gastric mucosa is pivotal in the pathogenesis of H. pylori-related disease. Following H. pylori infection, there is an observed increase in gastric mucosal macrophages, which are associated with the progression of gastritis. H. pylori elicits macrophage polarization, releases cytokines, reactive oxygen species (ROS) and nitric oxide (NO) to promote inflammatory response and eliminate H. pylori. Meanwhile, H. pylori has developed mechanisms to evade the host immune response in order to maintain the persistent infection, including interference with macrophage phagocytosis and antigen presentation, as well as induction of macrophage apoptosis. Consequently, the interaction between H. pylori and macrophages can significantly impact the progression, pathogenesis, and resolution of H. pylori infection. Moreover, macrophages are emerging as potential therapeutic targets for H. pylori-associated gastritis. Therefore, elucidating the involvement of macrophages in H. pylori infection may provide novel insights into the pathogenesis, progression, and management of H. pylori-related disease.

Abstract P3080: S100A8/9 Is A Key Regulator For Normal Heart Function During Pseudomonas Aeruginosa Infection

Rationale: P. aeruginosa ( P.a ) infection can cause severe pneumonia in ICU patients that leads to cardiac inflammation and cardiac dysfunction. Growing evidence indicates that a large number of neutrophils are recruited to the site of P.a. infection and releases S100A8/9 into the microenvironment. S100A8/9 has been shown to activate both the immune system (TLR4/RAGE) and has bactericidal properties. Often, hyperactivation of the inflammatory responses by S100A8/9 causes cardiac inflammation and dysfunction. Thus, we hypothesize that excessive production of S100A8/9 restrict bacterial growth and enhances the host immune response in order to control the infection and preserve heart function. Objective: To identify the mechanism of S100A8/9 mediated cardiac inflammation and cardiac dysfunction during P. aeruginosa infection. Methods and Results: To investigate the role of S100A8/9 in cardiac inflammation and cardiac dysfunction, we infected wild type (WT) and S100A8/9KO mice with P.a. intranasally. We monitored bodyweight at 24h intervals and measured weight loss, survival, and bacterial burden in the lungs and heart. We performed multicolor flow cytometry on BAL cells and heart cells for immune cell phenotyping and ELISA for cytokine levels. Also, we measured cardiac electric activity (EKG) and heart function (echocardiography). We found that bacterial burden in the lungs and heart was higher in S100A8/9KO mice than in WT, which correlated with increased mortality. We found severe cardiac electrical abnormalities (second-degree AV block) in S100A8/9KO mice and left ventricular dysfunction. However, there was no significant difference in the BALF immune cell phenotypes of both S100A8/9KO and WT infected mice. Finally, the S100A8/9 inhibitor enhanced the survival of P.a. infected mice. Conclusion: Our data demonstrate that neutrophil recruitment and release of S100A8/9 is critical to control bacterial growth in the lungs, however, uncontrolled neutrophil accumulation leads to excessive production of S100A8/9. Hyperactivation of the immune system by excessive S100A8/9 leads to systemic inflammation and bacterial dissemination of the heart. Furthermore, our studies revealed that blocking S100A8/9 receptor binding enhances the survival of mice during P.a. infection.

The Ecto-5'nucleotidase/CD73 Mediates Leishmania amazonensis Survival in Macrophages.

Endogenous nucleotides produced by various group of cells under inflammatory conditions act as potential danger signals in vivo. Extracellularly released nucleotides such as ATP are rapidly hydrolyzed to adenosine by the coordinated ectonucleotidase activities of CD39 and CD73. Leishmania is an obligate intracellular parasite of macrophages and capable of modulating host immune response in order to survive and multiply within host cells. In this study, the activity of CD73 induced by Leishmania amazonensis in infected macrophages has been investigated and correlated with parasite survival and infection in vitro. For this, the expression of CD39 and CD73, by flow cytometry, in murine peritoneal macrophages infected with metacyclic promastigotes of L. amazonensis has been analyzed. Our results showed that L. amazonensis-infected macrophages, unlike LPS-treated macrophages, increased CD73 expression. It was also noted that when CD73 enzymatic activity was blocked by α, β-methyleneadenosine 5′-diphosphate sodium salt (APCP), macrophage parasitism was significantly decreased. Interestingly, these effects were not associated with the production of TNF-α, IL-10, or nitric oxide (NO). Together, these data demonstrate that L. amazonensis induces a regulatory phenotype in macrophages, which by activating the CD39/CD73 pathway allows parasite survival through the action of immunomodulatory adenosine receptors.

Inhibition of Type III Interferon Expression in Intestinal Epithelial Cells-A Strategy Used by Coxsackie B Virus to Evade the Host's Innate Immune Response at the Primary Site of Infection?

Increasing evidence highlights the importance of the antiviral activities of the type III interferons (IFNλs; IL-28A, IL-28B, IL29, and IFNλ4) in the intestine. However, many viruses have developed strategies to counteract these defense mechanisms by preventing the production of IFNs. Here we use infection models, a clinical virus isolate, and several molecular biology techniques to demonstrate that both type I and III IFNs induce an antiviral state and attenuate Coxsackievirus group B (CVB) replication in human intestinal epithelial cells (IECs). While treatment of IECs with a viral mimic (poly (I:C)) induced a robust expression of both type I and III IFNs, no such up-regulation was observed after CVB infection. The blunted IFN response was paralleled by a reduction in the abundance of proteins involved in the induction of interferon gene transcription, including TIR-domain-containing adapter-inducing interferon-β (TRIF), mitochondrial antiviral-signaling protein (MAVS), and the global protein translation initiator eukaryotic translation initiation factor 4G (eIF4G). Taken together, this study highlights a potent anti-Coxsackieviral effect of both type I and III IFNs in cells located at the primary site of infection. Furthermore, we show for the first time that the production of type I and III IFNs in IECs is blocked by CVBs. These findings suggest that CVBs evade the host immune response in order to successfully infect the intestine.

Attaching and effacing pathogens: the effector ABC of immune subversion.

The innate immune response resembles an essential barrier to bacterial infection. Many bacterial pathogens have, therefore, evolved mechanisms to evade from or subvert the host immune response in order to colonize, survive and multiply. The attaching and effacing pathogens enteropathogenic Escherichia coli, enterohaemorrhagic E. coli, Escherichiaalbertii and Citrobacter rodentium are Gram-negative extracellular gastrointestinal pathogens. They use a type III secretion system to inject effector proteins into the host cell to manipulate a variety of cellular processes.Over the last decade, considerable progress was made in identifying and characterizing the effector proteins of attaching and effacing pathogens that are involved in the inhibition of innate immune signaling pathways, in determining their host cell targets and elucidating the mechanisms they employ. Their functions will be reviewed here.

A204 ANALYSIS AND CHARACTERIZATION OF THE EXCRETED AND SECRETED PRODUCTS OF PARASITIC HELMINTHS AS IMMUNOMODULATORS OF INFLAMMATORY BOWEL DISEASE

Abstract Background Parasitic helminths are known for their exceptional ability to modulate the host immune response in order to favour their survival. The excretory/secretory products (ESP), from Trichuris and Ascaris species are of keen interest for inflammatory bowel disease (IBD). Crohn’s disease and ulcerative colitis patients have benefitted from the administration of ova of T. suis in clinical trials, whereby symptoms were remediated through the ingestion of parasite ova, which subsequently hatch in the intestine. Our previous work has demonstrated the ability of T. suis ESP to downregulate secretion of inflammatory cytokines (TNF-α, IL-12) and increase the secretion of anti-inflammatory cytokines (IL-10) in murine bone marrow-derived macrophages. Aims This research aims to unveil the mechanisms of immune modulation by parasitic helminths in the context of IBD. We aim to characterize the cellular response in vitro, as well as the systemic response in vivo, in order to better characterize the scope of immune modulation that occurs with treatment. Methods Human peripheral blood mononuclear cell (PBMC) monocytes were purified and treated with helminth-derived products. The products were removed, and fresh media was added containing lipopolysaccharide (LPS) to stimulate cells. Supernatants were collected for cytokine analysis and cells were lysed and frozen. Mice were given 3% DSS or regular water for five days, and subsequently administered treatment with helminth-derived products, or a PBS control, once daily by intraperitoneal injection for 3–4 days. Weights were measured daily. On day 9 mice were sacrificed, colons lengths were measured, and spleens were collected for further analysis. Results We found that human PBMC monocytes treated with the ESP from T. suis and A. suum had decreased secretion of inflammatory cytokines (TNFα) and increased secretion of anti-inflammatory cytokines (IL-10). Additionally, we found that heminth products from A. suum had the ability to reverse the symptoms of weight loss and colon shrinking in DSS-mice compared to the control. Specifically, mice with DSS-induced colitis treated with metabolites increased their weight more than the PBS control (P < 0.0001) and had a longer colon compared to the PBS control (P < 0.001). Conclusions Taken together, these data generate an interest for intestinal helminth products as immunomodulators regarding treatment for patients suffering from inflammatory bowel disease (IBD). Funding Agencies NSERC and FRQNT

Oncolytic bacteria: past, present and future

More than a century ago, independent groups raised the possibility of using bacteria to selectively infect tumours. Such treatment induces an immune reaction that can cause tumour rejection and protect the patient against further recurrences. One of the first holistic approximations to use bacteria in cancer treatment was performed by William Coley, considered the father of immune-therapy, at the end of XIX century. Since then, many groups have used different bacteria to test their antitumour activity in animal models and patients. The basis for this reactivity implies that innate immune responses activated upon bacteria recognition, also react against the tumour. Different publications have addressed several aspects of oncolytic bacteria. In the present review, we will focus on revisiting the historical aspects using bacteria as oncolytic agents and how they led to the current clinical trials. In addition, we address the molecules present in oncolytic bacteria that induce specific toxic effects against the tumors as well as the activation of host immune responses in order to trigger antitumour immunity. Finally, we discuss future perspectives that could be considered in the different fields implicated in the implementation of this kind of therapy in order to improve the current use of bacteria as oncolytic agents.

Исследование антивирусной активности Глутоксима при инфицировании клеточной линии фибробластов вирусом везикулярного стоматита

New strategy for the treatment of animal infectious diseases is based upon the modulation of the host immune response in order to enhance the clearance of infectious agents and reduce the damaging effects of inflammation in the tissues. The modern approach to the use of immunomodulators (IMD) in veterinary practice consists in the usage of such drugs, which are not only immunomodulating, but also have antiviral, antioxidant, anti-inflammatory, hemostimulating and/or other important properties. The aim of the study was to identify possible antiviral activity of known IMD Glutoxim (GLT) during infection of diploid fibroblast cell lines M-8 and M-22 with vesicular stomatitis virus (VSV). Materials and methods: VSV, strain Indiana, was used. Antiviral activity of GLT investigated: 1) at doses recommended for experiments in vitro: 1, 4 and 8 µg/ml; 2) at low doses: 0,1; 0,25 and 0,5 µg/ml. GLT was added to the cell monolayer according to preventive (for 24 hours prior to VSV infection of cells) and treatment (unanimous with VSV infection) protocols. The antiviral activity of GLT was assessed by the following criteria: ability of the drug to prevent the development of virus cytopathic action, to inhibit the reproduction of VSV, and by expessing virucidal action. Results: GLT in doses recommended for in vitro experiments (1, 4, 8 µg/ml) did not delay the development of a specific virus-induced cytopathic action. The VSV titers in infected cells in the presence of GLT did not differ from those in the control cell lines infected with VSV without the addition of GLT. The latter had no virucidal effect against the VSV. Inoculation of GLT into the cell culture at low doses of 0.1, 0.25 and 0.5 mg/ml led to a significant (more than 100-fold) inhibition of VSV replication 24 hours after infection of cells. At later stages, 40 and 48 hours following infection, the antiviral effect of GLT was not detected. Thus, we established that GLT possesses antiviral effect in vitro, which is manifested 24 hours following infection of diploid fibroblast cell lines with VSV.

Life history adjustments to intestinal inflammation in a gut nematode.

Many parasitic nematodes establish chronic infections. This implies a finely tuned interaction with the host immune response in order to avoid infection clearance. Although a number of immune interference mechanisms have been described in nematodes, how parasites adapt to the immune environment provided by their hosts remains largely unexplored. Here, we used the gastrointestinal nematode Heligmosomoides polygyrus to investigate the plasticity of life history traits and immunomodulatory mechanisms in response to intestinal inflammation. We adopted an experimental model of induced colitis and exposed worms to intestinal inflammation at two different developmental stages (larvae and adults). We found that H. polygyrus responded to intestinal inflammation by up-regulating the expression of a candidate gene involved in the interference with the host immune response. Worms infecting mice with colitis also had better infectivity (earlier adult emergence in the intestinal lumen and higher survival) compared with worms infecting control hosts, suggesting that H. polygyrus adjusted its life history schedule in response to intestinal inflammation.

Parasitic Nematode Immunomodulatory Strategies: Recent Advances and Perspectives

More than half of the described species of the phylum Nematoda are considered parasitic, making them one of the most successful groups of parasites. Nematodes are capable of inhabiting a wide variety of niches. A vast array of vertebrate animals, insects, and plants are all identified as potential hosts for nematode parasitization. To invade these hosts successfully, parasitic nematodes must be able to protect themselves from the efficiency and potency of the host immune system. Innate immunity comprises the first wave of the host immune response, and in vertebrate animals it leads to the induction of the adaptive immune response. Nematodes have evolved elegant strategies that allow them to evade, suppress, or modulate host immune responses in order to persist and spread in the host. Nematode immunomodulation involves the secretion of molecules that are capable of suppressing various aspects of the host immune response in order to promote nematode invasion. Immunomodulatory mechanisms can be identified in parasitic nematodes infecting insects, plants, and mammals and vary greatly in the specific tactics by which the parasites modify the host immune response. Nematode-derived immunomodulatory effects have also been shown to affect, negatively or positively, the outcome of some concurrent diseases suffered by the host. Understanding nematode immunomodulatory actions will potentially reveal novel targets that will in turn lead to the development of effective means for the control of destructive nematode parasites.

Subversion of the Immune Response by Rabies Virus.

Rabies has affected mankind for several centuries and is one of the oldest known zoonoses. It is peculiar how little is known regarding the means by which rabies virus (RABV) evades the immune response and kills its host. This review investigates the complex interplay between RABV and the immune system, including the various means by which RABV evades, or advantageously utilizes, the host immune response in order to ensure successful replication and spread to another host. Different factors that influence immune responses—including age, sex, cerebral lateralization and temperature—are discussed, with specific reference to RABV and the effects on host morbidity and mortality. We also investigate the role of apoptosis and discuss whether it is a detrimental or beneficial mechanism of the host’s response to infection. The various RABV proteins and their roles in immune evasion are examined in depth with reference to important domains and the downstream effects of these interactions. Lastly, an overview of the means by which RABV evades important immune responses is provided. The research discussed in this review will be important in determining the roles of the immune response during RABV infections as well as to highlight important therapeutic target regions and potential strategies for rabies treatment.

Modulation of Cell Sialoglycophenotype: A Stylish Mechanism Adopted by Trypanosoma cruzi to Ensure Its Persistence in the Infected Host.

Trypanosoma cruzi, the etiological agent of Chagas disease exhibits multiple mechanisms to guarantee its establishment and persistence in the infected host. It has been well demonstrated that T. cruzi is not able to synthesize sialic acids (Sia). To acquire the monosaccharide, the parasite makes use of a multifunctional enzyme called trans-sialidase (Tc-TS). Since this enzyme has no analogous in the vertebrate host, it has been used as a target in drug therapy development. Tc-TS preferentially catalyzes the transfer of Sia from the host glycoconjugates to the terminal β-galactopyranosyl residues of mucin-like molecules present on the parasite’s cell surface. Alternatively, the enzyme can sialylate/re-sialylate glycoconjugates expressed on the surface of host cells. Since its discovery, several studies have shown that T. cruzi employs the Tc-TS activity to modulate the host cell sialoglycophenotype, thus favoring its perpetuation in the infected vertebrate. In this review, we summarize the dynamic of host/parasite sialoglycophenotype modulation, highlighting its role in the subversion of host immune response in order to promote the establishment of persistent chronic infection.

G1-4A, a Polysaccharide from Tinospora cordifolia Inhibits the Survival of Mycobacterium tuberculosis by Modulating Host Immune Responses in TLR4 Dependent Manner.

Rapid emergence of drug resistance in Mycobacterium tuberculosis (MTB) is a major health concern and demands the development of novel adjunct immunotherapeutic agents capable of modulating the host immune responses in order to control the pathogen. In the present study, we sought to investigate the immunomodulatory effects of G1-4A, a polysaccharide derived from the Indian medicinal plant Tinospora cordifolia, in in-vitro and aerosol mouse models of MTB infection. G1-4A treatment of MTB infected RAW264.7 macrophages significantly induced the surface expression of MHC-II and CD-86 molecules, secretion of proinflammatory cytokines (TNF-α, IL-β, IL-6, IL-12, IFN-γ) and nitric oxide leading to reduced intracellular survival of both drug sensitive (H37Rv) as well as multi drug resistant strains (Beijing and LAM) of MTB, which was partially attributed to G1-4A induced NO production in TLR4-MyD88 dependent manner. Similarly, bacillary burden was significantly reduced in the lungs of MTB infected BALB/c mice treated with G1-4A, with simultaneous up-regulation of the expression of TNF-α, INF-γ and NOS2 in the mouse lung along with increased levels of Th1 cytokines like IFN-γ, IL-12 and decreased levels of Th2 cytokine like IL-4 in the serum. Furthermore, combination of G1-4A with Isoniazid (INH) exhibited better protection against MTB compared to that due to INH or G1-4A alone, suggesting its potential as adjunct therapy. Our results demonstrate that modulation of host immune responses by G1-4A might improve the therapeutic efficacy of existing anti-tubercular drugs and provide an attractive strategy for the development of alternative therapies to control tuberculosis.

The Leishmania-Macrophage Interactions: Role of E-NTPDases and Purinergic Signaling

Leishmaniasis comprises a group of diseases caused by protozoan parasites of the genus Leishmania . The transmission occurs by the bite of phlebotomine female sand flies of the genera Phlebotomus and Lutzomyia. In the mammalian host, these parasites infect and proliferate mainly into the macrophages, avoiding the harmful effects of the innate inflammatory response. It has been reported in several works that purinergic signaling, including purine receptors P1 and P2, are dynamically modulated during both the development and activation of cells from the immune system to achieve homeostasis or combat infections as well as harmful damage. Many pathogens are able to subvert the host immune response in order to promote the success or maintenance of infection. This subversion can be related to the influence of pathogens on purinergic signaling leading to decreased levels of the pro-inflammatory molecule ATP and increased levels of the immunosuppressive molecule adenosine. This scenario can be produced as the final product of the joint activity of E-NTPDases and 5’-ecto-nucleotidases. Thus, this review will discuss the cellular and molecular events occurring during the interaction of Leishmania and macrophages focusing on the purinergic signaling pathways and their relationships with E-NTPDases from pathogenic species of Leishmania .

Immune Responses toHaemonchus Contortusin Sheep

Sheep, called as ‘museum of parasites’, is susceptible to many nematodes. Among the nematodes, Haemonchus contortus is an important voracious blood sucking helminth, which causes alteration in pH of abomasum and blood parameters like PCV. The host produces some immune mechanism against H. contortus to limit the pathogenic effect produced by the parasite. However, the parasite escapes the host immune response in order to survive within the host, which is called ‘evasion’ mechanism.

Human blood monocytes support persistence, but not replication of the intracellular pathogen C. pneumoniae.

BackgroundIntracellular pathogens have devised various mechanisms to subvert the host immune response in order to survive and replicate in host cells. Here, we studied the infection of human blood monocytes with the intracellular pathogen C. pneumoniae and the effect on cytokine and chemokine profiles in comparison to stimulation with LPS.ResultsMonocytes purified from peripheral blood mononuclear cells by negative depletion were infected with C. pneumoniae. While immunofluorescence confirmed the presence of chlamydial lipopolysaccharide (LPS) in the cytoplasm of infected monocytes, real-time PCR did not provide evidence for replication of the intracellular pathogen. Complementary to PCR, C. pneumoniae infection was confirmed by an oligonucleotide DNA microarray for the detection of intracellular pathogens. Raman microspectroscopy revealed different molecular fingerprints for infected and non-infected monocytes, which were mainly due to changes in lipid and fatty acid content. Stimulation of monocytes with C. pneumoniae or with LPS induced similar profiles of tumor necrosis factor-alpha (TNF-α) and interleukin (IL)-6, but higher levels of IL-1β, IL-12p40 and IL-12p70 for C. pneumoniae which were statistically significant. C. pneumoniae also induced release of the chemokines MCP-1, MIP-1α and MIP-1β, and CXCL-8, which correlated with TNF-α secretion.ConclusionInfection of human blood monocytes with intracellular pathogens triggers altered cytokine and chemokine pattern as compared to stimulation with extracellular ligands such as LPS. Complementing conventional methods, an oligonucleotide DNA microarray for the detection of intracellular pathogens as well as Raman microspectroscopy provide useful tools to trace monocyte infection.Electronic supplementary materialThe online version of this article (doi:10.1186/s12865-014-0060-1) contains supplementary material, which is available to authorized users.

LprG-mediated surface expression of lipoarabinomannan is essential for virulence of Mycobacterium tuberculosis.

Mycobacterium tuberculosis employs various virulence strategies to subvert host immune responses in order to persist and cause disease. Interaction of M. tuberculosis with mannose receptor on macrophages via surface-exposed lipoarabinomannan (LAM) is believed to be critical for cell entry, inhibition of phagosome-lysosome fusion, and intracellular survival, but in vivo evidence is lacking. LprG, a cell envelope lipoprotein that is essential for virulence of M. tuberculosis, has been shown to bind to the acyl groups of lipoglycans but the role of LprG in LAM biosynthesis and localization remains unknown. Using an M. tuberculosis lprG mutant, we show that LprG is essential for normal surface expression of LAM and virulence of M. tuberculosis attributed to LAM. The lprG mutant had a normal quantity of LAM in the cell envelope, but its surface was altered and showed reduced expression of surface-exposed LAM. Functionally, the lprG mutant was defective for macrophage entry and inhibition of phagosome-lysosome fusion, was attenuated in macrophages, and was killed in the mouse lung with the onset of adaptive immunity. This study identifies the role of LprG in surface-exposed LAM expression and provides in vivo evidence for the essential role surface LAM plays in M. tuberculosis virulence. Findings have translational implications for therapy and vaccine development.

The frustrated host response to Legionella pneumophila is bypassed by MyD88-dependent translation of pro-inflammatory cytokines.

Many pathogens, particularly those that require their host for survival, have devised mechanisms to subvert the host immune response in order to survive and replicate intracellularly. Legionella pneumophila, the causative agent of Legionnaires' disease, promotes intracellular growth by translocating proteins into its host cytosol through its type IV protein secretion machinery. At least 5 of the bacterial translocated effectors interfere with the function of host cell elongation factors, blocking translation and causing the induction of a unique host cell transcriptional profile. In addition, L. pneumophila also interferes with translation initiation, by preventing cap-dependent translation in host cells. We demonstrate here that protein translation inhibition by L. pneumophila leads to a frustrated host MAP kinase response, where genes involved in the pathway are transcribed but fail to be translated due to the bacterium-induced protein synthesis inhibition. Surprisingly, few pro-inflammatory cytokines, such as IL-1α and IL-1β, bypass this inhibition and get synthesized in the presence of Legionella effectors. We show that the selective synthesis of these genes requires MyD88 signaling and takes place in both infected cells that harbor bacteria and neighboring bystander cells. Our findings offer a perspective of how host cells are able to cope with pathogen-encoded activities that disrupt normal cellular process and initiate a successful inflammatory response.

Identification of Brucella abortus virulence proteins that modulate the host immune response

Brucellosis is an important zoonotic disease of almost worldwide distribution. One significant immune phenomenon of this disease is the ability of the pathogen to hide and survive in the host, establishing long lasting chronic infections. Brucella was found to have the ability to actively modulate the host immune response in order to establish chronic infections, but the mechanism by which the pathogen achieves this remains largely unknown. In our screening for protective antigens of Brucella abortus, 3 proteins (BAB1_0597, BAB1_0917, and BAB2_0431) were found to induce significantly higher levels of gamma interferon (IFNγ) in splenocytes of PBS immunized mice than those immunized with S19. This finding strongly implied that these three proteins inhibit the production of IFNγ. Previous studies have shown that LPS, PrpA, and Btp1/TcpB are three important immunomodulatory molecules with the capacity to interfere with host immune response. They have been shown to have the ability to inhibit the secretion of IFNγ, or to increase the production of IL-10. Due to the role of these proteins in virulence and immunomodulation, they likely offer significant potential as live, attenuated Brucella vaccine candidates. Understanding the mechanisms by which these proteins modulate the host immune responses will deepen our knowledge of Brucella virulence and provide important information on the development of new vaccines against Brucellosis.

Cytokine Gene Expression in the Tissues of Dogs Infected by Leishmania infantum

Canine leishmaniosis (CanL) caused by the protozoan parasite Leishmania infantum is a chronic systemic disease that is endemic in certain parts of the world. The domestic dog is the most important reservoir of L. infantum and is the main source of infection for other animals and for the human population. The aim of this study was to evaluate and compare the level of expression of genes encoding particular cytokines (interleukin [IL]-12, interferon [IFN]-γ, IL-2 and IL-4) in different tissues and organs of 53 adult dogs with or without clinical signs of leishmaniosis and after treatment for the disease. Asymptomatic dogs showed high expression of genes encoding IL-4 in blood leucocytes and of genes encoding IL-12 and IL-2 in lymph nodes. Blood leucocytes from symptomatic dogs had a mixed Th1 and Th2 cytokine gene expression profile, but lymph nodes from these animals had dominant IL-2 and IFN-γ gene expression, while bone marrow appeared to be unresponsive. The predominance of IL-4 gene expression in the blood of asymptomatic dogs may favour parasite replication, while the balance between Th1 and Th2 cytokine gene expression in the blood of symptomatic dogs may be important in reducing parasite replication and delaying the dissemination of Leishmania to other organs. The drugs used to treat CanL do not completely eliminate the parasite, so the high expression of the gene encoding IL-4 in blood leucocytes and the high expression of IL-12 and IL-4 mRNA in lymph nodes may reflect the persistence of residual Leishmania amastigotes. L. infantum appears able to regulate the host immune response in order to ensure its survival, but also to prevent the host from succumbing to infection. This guarantees its transmission and the completion of its life cycle.