TNF controls the infiltration of dendritic cells into the site of <Emphasis Type="Italic">Leishmania major</Emphasis> infection

TNF-negative C57BL/6 (B6.TNF^−/−) mice are highly susceptible to Leishmania (L.) major infection and succumb rapidly to fatal leishmaniasis. A T helper type 1 (Th1) cell-mediated immune response is central for protective anti-leishmanial immunity. Therefore, the observed susceptibility of B6.TNF^−/− mice to L. major parasites could be caused by a deficiency in mounting a Th1 response. Analysis of infected footpads revealed, that B6.TNF^−/− mice exhibited a substantially diminished formation of DCs at the site of infection. Furthermore, Th1 cytokines such as IFN-γ were reduced in footpads of infected B6.TNF^−/− mice. Cutaneous reconstitution of B6.TNF^−/− mice with either bone marrow derived DCs (BM-DCs) or recombinant TNF simultaneous to infection resulted in an increased expression of cytokines such as IFN-γ and in an enhanced presence of Leishmania-antigen in skin draining lymph nodes. In addition, the individual time of survival was doubled. In conclusion we demonstrate that the expression of dermal TNF is necessary to provide an environment that initiates a local inflammatory response, but is not sufficient to induce protective immunity.     

The protective Th1 response in mice is induced in the T-cell zone only three weeks after infection with <Emphasis Type="Italic">Leishmania major</Emphasis> and not during early T-cell activation

The protozoan parasite Leishmania spp. causes clinical pictures ranging in severity from spontaneously healing skin ulcers to systemic disease. The immune response associated with healing involves the differentiation of IFNγ-producing Th1 cells, whereas the non-healing phenotype is associated with IL4-producing Th2 cells. The widespread assumption has been that the T-cell differentiation that leads to a healing or non-healing phenotype is established at the time of T-cell activation early after infection. By selectively analyzing the expression of cytokine genes in the T-cell zones of lymph nodes of resistant (Th1) C57BL/6 mice and susceptible (Th2) BALB/c mice during an infection with Leishmania major in vivo, we show that the early T-cell response does not differ between C57BL/6 mice and BALB/c mice. Instead, Th1/Th2 polarization appears suddenly 3 weeks after infection. At the same time point, the number of parasites increases in lymph nodes of both mouse strains, but about 100-fold more in susceptible BALB/c mice. We conclude that the protective Th1 response in C57BL/6 mice is facilitated by the capacity of their innate effector cells to keep parasite numbers at low levels.     

Role of <Emphasis Type="Italic">Mycobacterium vaccae</Emphasis> in the protection induced by first generation <Emphasis Type="Italic">Leishmania</Emphasis> vaccine against murine model of leishmaniasis

Various Leishmania antigens showed to induce protection when used with IL-12 as an adjuvant in an animal model of leishmaniasis. Limitations in using IL-12 justify searching for an appropriate adjuvant to accelerate induction of a Th1-type immune response and protection. In this study, the role of Mycobacterium vaccae as an adjuvant mixed with either autoclaved Leishmania major (ALM) or freeze–thawed-killed L. major (KLM) in increasing protection in susceptible and resistant mice was studied. Nineteen groups of BALB/c and 19 groups of C57BL/6 mice, ten mice per group, were immunized three times in 45 days interval with different doses of either KLM or ALM alone or mixed with either BCG or different doses of M. vaccae. Immunized groups of mice and PBS-injected control group were challenged with 2 × 10⁶ promastigotes of L. major at the base of the tail. The evolution of the lesion was monitored, and the size of the lesion was measured and recorded weekly. Anti-Leishmania total IgG Ab was titrated before and after challenge. The results showed that immunization of either susceptible or resistant mice with KLM or ALM mixed with low dose of M. vaccae increased protection defined by significantly smaller ulcer size in immunized mice compared with the PBS-injected control group.     

Cytokine responses in mice infected with<Emphasis Type="Italic"> Clonorchis sinensis</Emphasis>

FVB and BALB/c mice show different morbidity, development of Clonorchis sinensis, and pathological changes following C. sinensis infection. FVB mice are susceptible and BALB/c mice are relatively more resistant to C. sinensis infection. To investigate the relationship between cytokine reaction and susceptibility to C. sinensis infection in FVB and BALB/c mice, we described both the patterns and kinetics of Th1 cytokines and Th2 cytokines in spleen cell culture. Interleukin (IL)-4 and IL-10 cytokine production in the culture supernatants of the concanavalin-A-stimulated spleen cells increased at 2–3 weeks post-infection in both strains. IL-5 production increased between 2 and 5 weeks post-infection in both strains, and reached a peak level at 2 weeks post-infection in BALB/c mice and 4 weeks post-infection in FVB mice. In contrast, gamma interferon (IFN-) production decreased between 2 and 4 weeks in both strains. IL-2 production increased slightly in BALB/c mice following infection, but was unchanged in FVB mice. IL-4 production over preinfection levels was significantly higher in FVB mice, whereas IFN-, IL-2, and IL-10 production were significantly higher in BALB/c mice. The levels of serum immunoglobulin E (IgE) and blood eosinophils in both mouse strains significantly increased between 3 and 6 weeks postinfection. Serum IgE levels were significantly higher in FVB mice than in BALB/c mice. The results of this study suggest that susceptibility to C. sinensis infection is associated with Th2 cytokine production, especially IL-4 which is predominant in relatively susceptible FVB mice.     

Treatment with IP-10 induces host-protective immune response by regulating the T regulatory cell functioning in <Emphasis Type="Italic">Leishmania</Emphasis><Emphasis Type="Italic">donovani</Emphasis>-infected mice

Visceral leishmaniasis (VL), caused by the protozoan parasite, Leishmania donovani, is characterized by an infection in the liver and spleen. The failure of the first-line drugs has led to the development of new strategies for combating VL. Recently, our group has shown that interferon-γ-inducible protein (IP)-10, a CXC chemokine, renders protection against VL. In the present study, we have elucidated the mechanism by which IP-10 renders protection in in vivo L. donovani infection. We observed that IP-10–treated parasitized BALB/c mice showed a strong host-protective T helper cell (Th) 1 immune response along with marked decrease in immunosuppressive cytokines, tumor growth factor (TGF)-β, and interleukin (IL)-10 secreting CD4⁺ T cells. This IP-10-mediated decrease in immunosuppressive cytokines was correlated with the reduction in the elevated frequency of CD4⁺CD25⁺ T regulatory (Treg) cells along with the reduced TFG-β production from these Treg cells in Leishmania-infected mice. This reduction in TGF-β production was due to effective modulation of TGF-β signaling by IP-10, which reduced the immunosuppressive activity of Treg cells. Thus, these findings put forward a detailed mechanistic insight into IP-10-mediated regulation of the Treg cell functioning during experimental VL, which might be helpful in combating Leishmania-induced pathogenesis.     

<Emphasis Type="Italic">Toxoplasma gondii</Emphasis>: expression and characterization of a recombinant protein containing SAG1 and GRA2 in <Emphasis Type="Italic">Pichia pastoris</Emphasis>

Toxoplasma gondii is an obligate intracellular protozoan which infects most species of warm-blooded animals and causes toxoplasmosis. Previous immunological and immunization studies have demonstrated the potential role of T. gondii antigens SAG1 and GRA2 as a vaccine candidate. In the present study, we have cloned, expressed, and purified a recombinant protein SAG1–GRA2 in Pichia pastoris. Results showed that P. pastoris was a robust system producing a large amount of highly purified and biological activity protein. BALB/c mice immunized with SAG1–GRA2 elicited stronger humoral and cellular responses in comparison to control groups. This immunization resulted in an enhanced Th1 immune response as measured by IgG2a antibody production and increased splenocyte IFN-γ production, whereas no IL-4 was detected. After a lethal challenge with the highly virulent T. gondii RH strain, a prolonged survival time in SAG1–GRA2-immunized mice was observed in comparison to control groups. Our data demonstrate that SAG1–GRA2 triggered a protective response against toxoplasmosis. Therefore, SAG1–GRA2 protein might be a good candidate for the further development of a multiantigenic vaccine.     

Complement C3 is required for the progression of cutaneous lesions and neutrophil attraction in<Emphasis Type="Italic"> Leishmania major</Emphasis> infection

To elucidate the role of complement-mediated uptake in Leishmania major infection in vivo, transgenic BALB/c mice that express the cobra venom factor (CVF) under control of the 1-antitrypsin promoter were infected. CVF expression in these mice leads to a continuous activation and subsequent consumption of complement C3 in the serum. In contrast to susceptible non-transgenic BALB/c mice, CVF-transgenic mice are highly resistant to L. major infection and show a significantly reduced parasite dissemination. Transient depletion of C3 in wild-type BALB/c mice delays progression of lesions for some days. Both CVF-transgenic and non-transgenic mice exhibit similar T cell responses upon infection. However, in CVF-transgenic mice, no infiltration of neutrophils, which were the prominent infiltrating cells at the site of infection in normal susceptible mice, could be detected. We conclude that C3 cleavage is required for the attraction of neutrophils that participate in parasite dissemination.     

Immunogenic characterization of the chimeric surface antigen 1 and 2 (SAG1/2) of <Emphasis Type="Italic">Toxoplasma gondii</Emphasis> expressed in the yeast <Emphasis Type="Italic">Pichia pastoris</Emphasis>

In this study, we successfully expressed a chimerical surface antigen 1 and 2 (SAG1/2) of Toxoplasma gondii in Pichia pastoris. Eighty human serum samples, including 60 from confirmed cases of toxoplasmosis, were tested against the purified recombinant SAG1/2 in Western blots. Results of Western blots targeted at Toxoplasma IgG and IgM showed that the recombinant SAG1/2 reacted with all sera from the toxoplasmosis cases but none with the Toxoplasma-negative serum samples. These results showed that the P. pastoris-derived recombinant SAG1/2 was sensitive and specific and suitable for use as antigen for detecting anti-Toxoplasma antibodies. To further investigate the immunological characteristic of the recombinant protein, the recombinant SAG1/2 was injected subcutaneously into BALB/c mice, and their serum was tested against total protein lysate of T. gondii. Mice immunized with the recombinant SAG1/2 reacted specifically with the native SAG1 and SAG2 of T. gondii. Significant proliferation of splenocytes stimulated with tachyzoite total protein lysate was observed in vaccinated BALB/c mice but not in those from negative control mice. Specific production of IFN-γ, the Th1-type cytokines, was also found in stimulated splenocytes from vaccinated mice. These results show that the chimeric protein recombinant SAG1/2 can elicit a Th1-associated protection against T. gondii infections in mice. Finally, vaccinated mice were significantly protected against lethal challenge with live T. gondii RH strain tachyzoites (P < 0.005), and their survival time increased significantly compared to the negative control.     

Murine immune response induced by Leishmania major during the implantation of paraffin tablets

We carried out a model of chronic inflammation using a subcutaneous paraffin tablet in mice experimentally infected with Leishmania major. It was previously reported that the parasite load following paraffin implantation occurred at a peak of 21 days in both BALB/c and C57BL/6 mice. At the present study, we have investigated what cytokines and chemokines are directly related to the parasite load in C57BL/6 mice. All mice were divided in four groups: mice implanted with paraffin tablets; mice experimentally infected with L. major; mice implanted with paraffin tablets and experimentally infected with L. major; and mice submitted only to the surgery were used for the Real-Time Polymerase Chain Reaction (RT-PCR) controls. Fragments of skin tissue and the tissue surrounding the paraffin tablets (inflammatory capsule) were collected for histopathology and RT-PCR studies. By 21 days, a diffuse chronic inflammatory reaction was mainly observed in the deep dermis where macrophages parasitized with Leishmania amastigotes were also found. RT-PCR analysis has shown that BALB/c mice showed strong IL-4 and IL-10 mRNA expression than controls with very little expression of IFN-γ. In contrast, both IFN-γ and IL-10 mRNA was found in higher levels in C57BL/6 animals. Moreover, in C57BL/6 mice the expression of chemokines mRNA of CCL3/MIP-1α was more highly expressed than CCL2/MCP-1. We conclude that the Th1 immune response C57BL/6 did not change to a Th2 response, even though C57BL/6 animals presented higher parasitism than BALB/c mice 21 days after infection and paraffin implantation.     

Cellular immune responses in <Emphasis Type="Italic">Echinostoma caproni</Emphasis> experimentally infected mice

The Echinostoma caproni–mice system is extensively used as an experimental model for the study of the factors involved in the establishment of chronic intestinal helminth infections. Although several parameters of the immunobiology of the host–parasite system have been studied in detail, the current knowledge of the cellular responses in these infections is still scarce. In the present paper, we analyze the kinetics of the circulating CD3⁺ and CD19⁺ cell populations and the different T-cell phenotype profiles in mice experimentally infected with E. caproni. Whereas the CD3⁺ populations remained stable during the complete experiment, a marked increase in CD19⁺ cells was observed from 4 weeks post-infection and beyond. Similarly, a marked increase in CD8⁺ cell populations was observed in the 2 week post-infection. Our results show that E. caproni infection in mice alters the peripheral lymphoid cell populations, which may be important to determine the course of the infection. In this sense, CD8⁺ cells can be essential in relation to their role as a source of IFN-γ.     

In vitro and in vivo efficacies of amlodipine against <Emphasis Type="Italic">Listeria monocytogenes</Emphasis>

Listeria monocytogenes causes suppurative gastritis in BALB/c mice. We investigated the effect of the antihypertensive drug amlodipine (Aml) on the growth of L. monocytogenes in vitro and in vivo. Aml showed noteworthy inhibitory action (minimum inhibitory concentration, MIC₉₀ 32 μg/ml) against Listeria strains and demonstrated cidal (minimum bactericidal concentration, MBC 64 μg/ml) activity. Aml administered orally at 2.5 μg/g in female BALB/c mice for 7 days, commencing 4 days before oral challenge (1 × 10⁸ CFU/ml with L. monocytogenes ATCC 51774), significantly reduced bacterial counts in the stomach (P < 0.01), liver (P < 0.01), and spleen (P < 0.05), and decreased (P < 0.05) gastric lesions, neutrophilic infiltration, edema, vascular degeneration, and necrosis of gastric tissues. It caused the down-regulation of expression of inflammatory cytokines (IFN-γ, IL-1β, and TNF-α) compared to drug-free control. Aml may be used in the presence of an antibiotic as adjunct therapy that boosts the host immunity against Listeria. Further, QSAR studies might contribute in manipulating it as a lead compound for the synthesis of new, more effective non-antibiotics (helper compounds), perhaps devoid of side-effects, that could be recommended as compassionate therapy for listeriosis.     

Comparative evaluation of immunization with recombinant protein and plasmid DNA vaccines of fusion antigen ROP2 and SAG1 from <Emphasis Type="Italic">Toxoplasma gondii</Emphasis> in mice: cellular and humoral immune responses

The aim of this work was to evaluate immune responses in BALB/c mice vaccinated subcutaneously by recombinant protein, or intramuscularly by plasmid DNA with fusion antigen of rhoptry protein 2 (ROP2) and major surface protein 1 (SAG1) from Toxoplasma gondii (T. gondii). BALB/c mice were immunized with one of three different antigen formulations respectively, which were rROP2-SAG1, pcROP2-SAG1, and pcROP2-SAG1 boosted with rROP2-SAG1. The production of IgG, IgG subclasses, lymphoproliferation, and level of gamma interferon (IFN-γ) were detected after vaccination. The animals vaccinated with rROP2-SAG1 quickly developed specific anti-TLA (T. gondii lysate antigen) antibodies, which continued to rise after immunization. However, production of IgG against TLA in mice vaccinated with pcROP2-SAG1 was relatively slow and maintained a high level after reaching plateau. There are more vigorous specific lymphoproliferative responses observed in mice of group rROP2-SAG1 than in pcROP2-SAG1. Immune responses in mice of group pcROP2-SAG1 boosted with rROP2-SAG1 were similar to the protein immunization group. Three immunization procedures resulted in a similar level of IFN-γ production. Our results indicate that BALB/c mice vaccinated by three immunization procedures induce similar humoral and cellular immunity against infection of T. gondii. Mice immunized with recombinant protein rROP2-SAG1 produce more humoral immune responses than mice immunized with other antigen formulations.     

Cloning,expression, and characterization of <Emphasis Type="Italic">Schistosoma japonicum</Emphasis> tegument protein phosphodiesterase-5

The tegument proteins of schistosomes are regarded as potential vaccine candidates and drug targets to control schistosomiasis. Nucleotide pyrophosphatase/phosphodiesterase-5 (NPP-5), which belongs to a multigene family of nucleotide pyrophosphatase/phosphodiesterases (NPPs), is important in the hydrolysis of pyrophosphate or phosphodiester bonds in nucleotides and their derivatives. In the present study, SjNPP-5, identified as one of the tegument proteins of Schistosoma japonicum in our previous proteomic studies, was cloned on a fragment of 1,371 bp and expressed as a recombinant protein of 69 kDa. Real-time RT-PCR analysis showed that SjNPP-5 was up-regulated at 21–42 days, and the expression level in 42-day-old male worms was almost nine times higher than that in females. Western blot analysis revealed that rSjNPP-5 had good antigenicity. Immunofluorescence analysis found that SjNPP-5 was a membrane-associated antigen mainly distributed on the surface of the male adult worm of S. japonicum. BALB/c mice vaccinated with rSjNPP-5 three times showed a 29.90% worm reduction (P < 0.05) and a 26.21% egg count reduction (P > 0.05). Immunization with rSjNPP-5 induced a mixed Th1/Th2 response in which Th1 was dominant. The response was characterized by a reduced IgG1/IgG2a ratio and elevated production of cytokines IFN-γ and IL-4. This study suggested that SjNPP-5 may be important in schistosome development, and further investigations are required to fully understand the function of this molecule.     

Pathological and immunological findings in placentas from pregnant BALB/c mice infected with <Emphasis Type="Italic">Neospora caninum</Emphasis> at early and late stages of gestation

Neospora caninum is transmitted from a cow to its foetus by vertical transmission and the timing of infection in gestation is an important factor in determining the disease outcome. Few studies have explored the role of the placenta in the outcome of N. caninum infection during pregnancy. Here, we described the N. caninum presence, parasite load, local immune response, and histopathological lesions at the materno-foetal interface after infection of BALB/c mice at early and late stages of gestation. In mice infected at early gestation, N. caninum DNA was detected in foetoplacentary units 7 days post-infection (PI) and in the placenta, but not in viable foetuses on day 14 PI, indicating that the parasite was multiplying primarily in the placental tissues without reaching the foetus. Moreover, parasite DNA was detected in resorptions, suggesting that foetal death could be a consequence of infection. An increase in IFN-γ, TNF-α and IL-10 expression was observed in N. caninum PCR-positive placentas, which could favour N. caninum foetal transmission and be harmful to both the placenta and the foetus. Histopathological analysis revealed necrosis affecting both the maternal and foetal sides of the placenta. At late gestation, transmission occurred rapidly following infection (day 3 PI), but parasite were rarely found. In addition, an increase in cytokine expression was observed in spleen and placental tissues from infected animals, while a downregulation in IL-4 expression was only observed in the spleen. Finally, necrosis in the placenta was limited to the maternal side, suggesting that the parasite is mainly multiplying in the placental tissue at this stage. Thus, the results of the present study indicate that the placenta may be actively involved in N. caninum pathogenesis.     

In vitro anthelmintic activity of the essential oils of <Emphasis Type="BoldItalic">Zanthoxylum zanthoxyloides</Emphasis> and <Emphasis Type="BoldItalic">Newbouldia laevis</Emphasis> against <Emphasis Type="BoldItalic">Strongyloides ratti</Emphasis>

The need for new anthelmintic with no chemical residues is becoming urgent. In a program aiming at the evaluation of plant as sources of new active molecules, the anthelmintic activities of the essential oils (EOs) obtained from either Zanthoxylum zanthoxyloides seeds or Newbouldia laevis leaves were evaluated against Strongyloides ratti by analyzing the results of two in vitro bioassays. These two plants and their tested parts were retained after an ethnopharmacology survey that confirmed their use by small-scale farmers for treatment of small ruminants affected by digestive helminths. The plants were harvested in Benin, and their EO were obtained by hydrodistillation. The EO yield of extraction was 0.65% (w/w) of for Z. zanthoxyloides seeds and 0.05% (w/w) for N. laevis. The chemical compositions of the two EOs were analyzed by gas chromatography coupled with mass spectrometry. The major constituents of the EO from Z. zanthoxyloides consisted of the following compounds: γ-terpinene (18 %), undecane (15 %), valencene (8.3 %), decanal (8.3 %), and 3-carene (6.7 %). In contrast, the major constituents of the EO from N. laevis leaves consisted of the following compounds: β-caryophyllene (36 %) and eugenol (5.8 %). An egg-hatching inhibition (EHI) assay was developed and a larval migration inhibition assay was used on S. ratti to examine the effects of the EOs and to evidence their inhibitory concentrations (IC₅₀ and IC₉₀) values on this nematode. Furthermore, the toxicity of the two EOs on Vero cell line was evaluated. When tested on S. ratti egg hatching, the two EOs resulted in similar IC₅₀ values (19.5 and 18.2 μg/ml for Z. zanthoxyloides and N. laevis, respectively), which were about sevenfold higher than that of the control (thiabendazole, IC₅₀ = 2.5 μg/ml). Larval migration was inhibited at similar concentrations for: Z. zanthoxyloides (IC₅₀ = 46 μg/ml), N. laevis (IC₅₀ = 51 μg/ml), and the control [levamisole (IC₅₀ = 36 μg/ml)]. No cytotoxicity was found on Vero cells because both EOs had IC₅₀ values higher than 50 μg/ml. Therefore, we have concluded that the EOs from two plants, used in folk medicine, may contain compounds with anthelmintic activity and could be used as improved traditional medicines or, at least, as food additives in a combined treatment for the control of helminth infections.     

Detection of <Emphasis Type="BoldItalic">Cryptosporidium parvum</Emphasis> and <Emphasis Type="BoldItalic">Cryptosporidium hominis</Emphasis> in human patients in Cairo,Egypt

Cryptosporidium is a significant cause of diarrheal disease in developing and industrialized nations. Cryptosporidium hominis and Cryptosporidium parvum are the main agents of cryptosporidiosis in humans. In Egypt, very little is known about genetic structure of Cryptosporidium spp. Therefore, this study was designed to examine samples from sporadic cases of cryptosporidiosis in Egyptians in order to identify the species involved in infection as well as the transmission dynamics and distribution of the parasite in the Great Cairo area. A total of 391 human faecal samples were collected, between May 2008 and March 2009, from ten public hospitals in Great Cairo. Initial screening by immunochromatographic detection kit “the Stick Crypto-Giardia; Operon” showed 23 possible positive cases. Twenty of them were confirmed by microscopic examination. PCR was performed by amplification of the oocyst wall protein (COWP) gene where 18 out of 23 samples were positive, one not detected by microscopy. Cryptosporidium genotyping was performed by RFLP analysis of PCR products of the diagnosis PCR. Only 15 samples rendered a digestion pattern. The genotyping distribution was nine cases showing C. hominis genotype, three showing C. parvum genotype and three showing mixed infection by C. hominis and C. parvum. The data showed an elevated prevalence of C. hominis (80.0%), the most anthroponotic species, suggesting a human–human transmission. Furthermore, the presence of up to 40% of samples infected with C. parvum shows that further investigations are required to determine the subgenotypes of C. parvum to clarify the mode of transmission in order to improve the control measures.     

Effect of A2 gene on infectivity of the nonpathogenic parasite <Emphasis Type="Italic">Leishmania tarentolae</Emphasis>

Several species of protozoan parasites of the genus Leishmania are pathogenic to mammals and cause a wide spectrum of pathologies in human. However, the genus includes some species which infect reptiles. Leishmania tarentolae is a lizard pathogen absolutely nonpathogenic to mammals. Recent studies have shown that among some major virulence factors, A2 is absent in this species. First identified as an amastigote-specific gene in Leishmania donovani, A2 has been proved to play a major role in parasite virulence and visceralization capability. In this study, we have transfected A2 episomally into L. tarentolae and evaluated its effect on infectivity and survival of the parasites, in vitro and in vivo. During infection of in vitro-cultured intraperitoneal macrophages of BALB/c mice, A2-expressing L. tarentolae parasites demonstrated significantly higher level of infectivity in days 3 and 4 post-infection in comparison with the wild-type strain as control. Furthermore, in vivo infection showed that A2 has significantly increased the ability of L. tarentolae to survive in the liver of BALB/c mice. Altogether, our results show that A2 is functional in L. tarentolae, although through an unknown mechanism, and loss of A2 has been one of the factors partly contributing to the loss of virulence of L. tarentolae.     

Small-scale to large-scale and back: larval trematodes in <Emphasis Type="BoldItalic">Lymnaea stagnalis</Emphasis> and <Emphasis Type="BoldItalic">Planorbarius corneus</Emphasis> in Central Europe

We examined the small-scale temporal and spatial variability in composition and structure of larval trematode communities in Lymnaea stagnalis and Planorbarius corneus in two fish ponds in the Czech Republic and compared the patterns of richness and similarity to continental and regional trematode faunas of these hosts. The levels of parasitism in the populations of both hosts were high, the former parasitized predominantly by allogenic species maturing in a wide range of birds and the latter infected by relatively more species completing their life cycles in micromammals. Communities in both hosts exhibited a congruent pattern of seasonal change in overall infection rates and community composition with lower levels of infection in spring. Both temporal and spatial variation was closely related to the structure of snail populations, and no significant differentiation of community composition with respect to pond was observed. Comparisons with large-scale inventories revealed overall congruent patterns of decreased richness and similarity and increased variability at the smaller scales in both host–parasite systems. The relative compositional homogeneity of larval communities in both snail hosts irrespective of scale suggests that historical data at small to medium regional scales may provide useful estimates of past richness and composition of larval trematode communities in these snail hosts.     

Transgenic Expression of CXCR3 on T Cells Enhances Susceptibility to Cutaneous Leishmania major Infection by Inhibiting Monocyte Maturation and Promoting a Th2 Response

Cutaneous leishmaniasis, caused mainly by Leishmania major, an obligate intracellular parasite, is a disfiguring disease characterized by large skin lesions and is transmitted by a sand fly vector. We previously showed that the chemokine receptor CXCR3 plays a critical role in mediating resistance to cutaneous leishmaniasis caused by Leishmania major. Furthermore, T cells from L. major-susceptible BALB/c but not L. major-resistant C57BL/6 mice fail to efficiently upregulate CXCR3 upon activation. We therefore examined whether transgenic expression of CXCR3 on T cells would enhance resistance to L. major infection in susceptible BALB/c mice. We generated BALB/c and C57BL/6 transgenic mice, which constitutively overexpressed CXCR3 under a CD2 promoter, and then examined the outcomes with L. major infection. Contrary to our hypothesis, transgenic expression of CXCR3 (CXCR3^Tg) on T cells of BALB/c mice resulted in increased lesion sizes and parasite burdens compared to wild-type (WT) littermates after L. major infection. Restimulated lymph node cells from L. major-infected BALB/c-CXCR3^Tg mice produced more interleukin-4 (IL-4) and IL-10 and less gamma interferon (IFN-γ). Cells in draining lymph nodes from BALB/c-CXCR3^Tg mice showed enhanced Th2 and reduced Th1 cell accumulation associated with increased neutrophils and inflammatory monocytes. However, monocytes displayed an immature phenotype which correlated with increased parasite burdens. Interestingly, transgenic expression of CXCR3 on T cells did not impact the outcome of L. major infection in C57BL/6 mice, which mounted a predominantly Th1 response and spontaneously resolved their infection similar to WT littermates. Our findings demonstrate that transgenic expression of CXCR3 on T cells increases susceptibility of BALB/c mice to L. major.     

Monoassociation with probiotic <Emphasis Type="Italic">Lactobacillus delbrueckii</Emphasis> UFV-H2b20 stimulates the immune system and protects germfree mice against <Emphasis Type="Italic">Listeria monocytogenes</Emphasis> infection

In the present study, we investigated the protective effects of Lactobacillus delbrueckii UFV-H2b20 on the resistance to Listeria monocytogenes infection in gnotobiotic mice. Germfree mice or monoassociated mice were infected with L. monocytogenes, and the microbiological and immunological responses were evaluated after 1, 3, and 5 days of infection. Monoassociation with L. delbrueckii was capable of protecting mice against death caused by L. monocytogenes and induced a faster clearance of the bacteria in the liver, spleen, and peritoneal cavity at days 1, 3, and 5 post-infection. Also, monoassociated mice displayed less liver injury than germfree mice. The production of TNF-α in the serum, peritoneal cavity, and gut was augmented in monoassociated mice. Likewise, the levels of IFN-γ found on supernatants of spleen cells cultures were higher after the monoassociation. In addition, increased production of nitric oxide in peritoneal cell cultures supernatants and in serum was observed in mice that received L. delbrueckii. The monoassociation with L. delbrueckii induced higher production of IL-10 in the mucosal immune system. We conclude that monoassociation with L. delbrueckii UFV-H2b20 protects mice from death caused by L. monocytogenes infection by favoring effector responses while preventing their immunopathological consequences.