High iNOS expression in macrophages in canine leishmaniasis is associated with low intracellular parasite burden

MicroRNA-194 regulates parasitic load and IL-1β-dependent nitric oxide production in the peripheral blood mononuclear cells of dogs with leishmaniasis

Domestic dogs are the primary urban reservoirs of Leishmania infantum, the causative agent of visceral leishmaniasis. In Canine Leishmaniasis (CanL), modulation of the host's immune response may be associated with the expression of small non-coding RNAs called microRNA (miR). miR-194 expression increases in peripheral blood mononuclear cells (PBMCs) of dogs with leishmaniasis with a positive correlation with the parasite load and in silico analysis demonstrated that the TRAF6 gene is the target of miR-194 in PBMCs from diseased dogs. Here, we isolated PBMCs from 5 healthy dogs and 28 dogs with leishmaniasis, naturally infected with L. infantum. To confirm changes in miR-194 and TRAF6 expression, basal expression of miR-194 and gene expression of TRAF6 was measured using qPCR. PBMCs from healthy dogs and dogs with leishmaniasis were transfected with miR-194 scramble, mimic, and inhibitor and cultured at 37° C, 5% CO2 for 48 hours. The expression of possible targets was measured: iNOS, NO, T-bet, GATA3, and FoxP3 were measured using flow cytometry; the production of cytokines IL-1β, IL-4, IL-6, IL-10, TNF-α, IFN-γ, and TGF-β in cell culture supernatants was measured using capture enzyme-linked immunosorbent assays (ELISA). Parasite load was measured using cytometry and qPCR. Functional assays followed by miR-194 inhibitor and IL-1β blockade and assessment of NO production were also performed. Basal miR-194 expression was increased in PBMC from dogs with Leishmaniasis and was negatively correlated with TRAF6 expression. The mimic of miR-194 promoted an increase in parasite load. There were no significant changes in T-bet, GATA3, or FoxP3 expression with miR-194 enhancement or inhibition. Inhibition of miR-194 increased IL-1β and NO in PBMCs from diseased dogs, and blockade of IL-1β following miR-194 inhibition decreased NO levels. These findings suggest that miR-194 is upregulated in PBMCs from dogs with leishmaniasis and increases parasite load, possibly decreasing NO production via IL-1β. These results increase our understanding of the mechanisms of evasion of the immune response by the parasite and the identification of possible therapeutic targets.

miR-148a regulation interferes in inflammatory cytokine and parasitic load in canine leishmaniasis

Canine leishmaniasis (CanL) is a severe public health threat. Infected animals mediate transmission of the Leishmania protozoan to humans via the sandfly's bite during a blood meal. CanL progression depends on the degree of suppression of the immune response, possibly associated with microRNAs (miR), which can modulate mRNA translation into proteins and (consequently) regulate cell function. Increased miR-148a in splenic leukocytes (SL) of dogs with CanL was observed in previous studies, and in silico analysis, identified possible pathways involved in immune response regulation that are affected by this miR. Therefore, we evaluated the involvement of miR-148a in the regulation of TNF-α, IL-6, IL-12, IL-1β, iNOS, MHCII, CD80, CD3, T-bet, and GATA-3 transcription factors and their relationship with parasite load in SL of dogs with CanL. Splenic leukocytes obtained from healthy and diseased dogs were transfected with miR-148a mimic and inhibitor oligonucleotides. After 48 hours, expression levels of MHCII, CD80, iNOS, CD3, T-bet, and GATA-3 were evaluated by flow cytometry, and concentrations of TNF-α, IL-12, IL-6, and IL-1β were measured in culture supernatants by capture enzyme-linked immunosorbent assays. Transfection of SL with miR-148a mimics decreased iNOS levels in cells and TNF-α, IL-6, and IL-12 in the supernatants of cultured SL from CanL dogs. Interestingly, transfection with miR-148a inhibitor decreased parasite load in SL cells. These results suggest a direct or not regulatory role of this miR in the immune response to Leishmania infantum infection. We conclude that miR-148a can modulate immune responses by regulating inflammatory cytokines during CanL. Our results contribute to understanding the complex host/parasite interaction in CanL and could assist the development of treatments.

Vitamins A and D and Zinc Affect the Leshmanicidal Activity of Canine Spleen Leukocytes

Canine leishmaniasis (CanL) is a chronic disease caused by Leishmania infantum, and the limitations of the current treatments have encouraged new alternatives, such as the use of immunomodulatory nutrients. The objective of this study was to determine the serum levels of vitamin A (retinol), vitamin D (25(OH)VD3), and zinc (Zn) in dogs with CanL and the effect of in vitro supplementation with the respective active forms ATRA, 1,25(OH)2VD3, and SZn on spleen leukocyte cultures. Serum retinol, 25(OH)VD3, and Zn were determined by HPLC, ELISA, and ICP-MS, respectively. Spleen leukocyte cultures were used for the detection of NO and ROS by flow cytometry; the IFN-γ, TNF-α, and IL-10 levels were determined by ELISA; and the parasite load was determined by microscopy. We detected low serum levels of retinol and Zn and high levels of 25(OH)VD3 in the CanL group. The in vitro supplementation of CanL spleen leukocytes with ATRA, 1,25(OH)2VD3, and SZn, in addition to a soluble leishmania antigen (SLA) treatment, increased the NO and ROS levels, while the treatments with only ATRA and SZn increased the TNF-a levels. Increased IL-10 and IFN-g levels were observed with the addition of SLA to the medium, although the addition of the three nutrients led to a reduction of the IL-10 levels, and the addition of 1,25(OH)2VD3 and SZn led to a reduction of IFN-g. A supplementation with 1,25(OH)2VD3 and SZn reduced the parasite load but only in the absence of SLA. We suggest that the nutrients we tested are involved in the leishmanicidal mechanism, showing a potential for investigation in future studies.

Immunohistochemical Characterization of Tumor-Associated Macrophages in Canine Lymphomas

Macrophages have been confirmed to play a significant role in the behavior of human lymphomas, albeit no consistent data are so far available in canine lymphomas. The present study characterizes the macrophages present in cases of canine nodal lymphoma and their relationship with the histological grade and the immunophenotype. Samples from the lymph nodes of 25 dogs diagnosed with lymphoma were selected. Immunohistochemistry was used to determine the tumor immunophenotype (CD3 and CD20 antibodies) and macrophage characterization (Iba1, MAC387, CD204, CD163 and iNOS antibodies). Macrophage counting was performed in 10 randomly selected, high-power fields per sample. Generalized linear models with Poisson distribution were used for statistical analysis. A significantly greater number of macrophages (Iba1+) were detected in high-grade and B-cell lymphomas. The highest amount of both M1 (iNOS+) and M2 (CD204+ and CD163+) subtypes were observed in B-cell lymphomas. High-grade lymphomas showed a greater number of CD204+ and CD163+ cells and recently recruited MAC387+ macrophages. The latter were most abundant in T than in B-cell lymphomas. In conclusion, a significant population of macrophages is present in canine lymphomas, which constitute a heterogeneous population that shows variations in the amount and immunohistochemical profile according to the histological grade and immunophenotype.

Combinatorial delivery of antigen and TLR agonists via PLGA nanoparticles modulates Leishmania major-infected-macrophages activation

Appropriate activation of macrophages is critical for the elimination of Leishmania parasites, which resides in this cell. Some species of Leishmania (L.) fails to stimulate macrophages and establish a chronic infection. To overcome this suppression and induce an innate immune response, the effect of PLGA-encapsulated soluble antigens of Leishmania (SLA) along with agonists of TLR1/2 (Pam3CSK4) and TLR7/8 (R848) nanoparticles (NPs) on activation of L. major-infected-macrophages were investigated and were compared with those of soluble formulations. SLA and R848 were encapsulated into the PLGA, while Pam3CSK4 adsorbed onto the surface of nanoparticles. The kinetics of pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) and iNOS genes expression were investigated by qPCR over 72 h. The parasite load was also quantified by qPCR. The results indicated that engulfment of L. major promastigotes does not induce any pro-inflammatory cytokines expression by macrophages; however, the infected-cells are capable of responding to the TLRs agonists, and a lesser extent, to the SLA stimulation. Encapsulation resulted in increased strength of the IL-1β, IL-6, TNF-α, and increased and prolonged time of iNOS expression. Also, encapsulation showed the leishmanicidal activity by decreasing parasite load in treated NPs formulations. Among the different combinations of the components, the triple (SLA-R848-Pam3CSK4) forms promoted the highest activation of macrophages, followed by dual SLA-Pam3CSK4 and SLA-R848 NPs. In conclusion, the findings of this study indicate that the addition of SLA in combination with TLR1/2 and TLR7/8 agonists either in NPs or in soluble forms overcome the suppression of L. major-infected macrophages. Moreover, encapsulation increases the strength and duration of the cytokines and iNOS expression, in parallel with decreasing parasite load, suggesting a longer availability or delivery of the NPs into the macrophages. These findings highlight the advantages of particulate therapeutic vaccine formulations.

Transcriptomic analyses reveal distinct response of porcine macrophages to Toxoplasma gondii infection

Toxoplasma gondii is an obligate protozoan parasite infecting diverse hosts. Studies have demonstrated that different hosts respond differently to Toxoplasma infection. Pigs are among the most susceptible hosts of T. gondii, but the host-pathogen interactions that shape the outcome of infection in pigs are completely unknown. Here, we used dual RNA-seq to profile the transcriptomic changes of porcine alveolar macrophages (PAMs) upon Toxoplasma infection. Our results indicated that PAMs initiated different responses to Toxoplasma infection compared with mouse macrophages. First, although infected PAMs upregulated numerous pro-inflammatory factors, IL-12, which plays critical roles in IL-12~IFN-γ-mediated immunity against Toxoplasma infection in mice, was found unchanged during PAM infection. Second, the gene encoding iNOS that is responsible for nitric oxide (NO) production was also not induced in infected PAMs. Consistently, there was no NO level change in PAMs after infection. Third, it seems like Toxoplasma infection inhibited apoptosis in PAMs. On the parasite side, the most obvious change is the upregulation of genes involved in metabolism and macromolecule synthesis, such as the type II fatty acid synthesis in the apicoplast. Together, these results revealed distinct responses of PAMs to Toxoplasma infection and provide novel insights into Toxoplasma-pig interactions.

Clinical and Immunological Response in Dogs Naturally Infected by L. infantum Treated with a Nutritional Supplement

Simple Summary

We evaluated the effects of a commercial nutraceutical supplementation in dogs naturally affected by Leishmania infantum. This nutraceutical supplement is proposed to be added to dog diet to foster physiological immune-response during chronic leishmaniasis. Parasite clearance is infrequently obtained by immune response in both the human and canine leishmaniasis. Pharmacological therapies frequently fail in the elimination of L. infantum that could have settled in deep organs, escaping immune responses and therapy. The conventional drug therapy improves clinical signs, reduces parasitemia as well as relapse of infection. This nutraceutical supplementation can improve the impaired immune response of the infected dogs to fight the disease.

Abstract

The use of nutraceuticals as immunomodulators in the treatment of visceral leishmaniasis has generated interest in the current approaches to treat the disease. In this clinical and immunological study, we investigated whether the administration of a nutritional supplement mediates the immune-modulatory response in canine leishmaniosis (CL) and improves the clinical outcome of the disease. With this purpose, we analysed T lymphocyte subsets in peripheral blood (PB) of 12 dogs naturally infected by Leishmania infantum, following treatment with a nutritional supplement. The regulatory T (Treg) cells and the T helper (Th) 1 population were specifically evaluated. The animals underwent complete clinical examination and blood sample collection for haematological, biochemical, serological and immunological analysis before treatment (T0), one month (T30) and 3 months (T90) after the onset of the nutraceutical supplementation. We observed that nutraceutical supplementation was associated with immunomodulation of Th1 response and significant clinical improvement of the animals. No side effects were observed. Therefore, a potential supportive role for the nutraceutical supplement during canine leishmaniasis is proposed.

Canine visceral leishmaniasis biomarkers and their employment in vaccines

The natural history of canine visceral leishmaniasis (CVL) has been well described, particularly with respect to the parasite load in different tissues and immunopathological changes according to the progression of clinical forms. The biomarkers evaluated in these studies provide support for the improvement of the tools used in developing vaccines against CVL. Thus, we describe the major studies using the dog model that supplies the rationale for including different biomarkers (tissue parasitism, histopathology, hematological changes, leucocytes immunophenotyping, cytokines patterns, and in vitroco-culture systems using purified T-cells subsets and macrophages infected with L. infantum) for immunogenicity and protection evaluations in phases I and II applied to pre-clinical and clinical vaccine trials against CVL. The search for biomarkers related to resistance or susceptibility has revealed a mixed cytokine profile with a prominent proinflammatory immune response as relevant for Leishmania replication at low levels as observed in asymptomatic dogs (highlighted by high levels of IFN-γ and TNF-α and decreased levels in IL-4, TGF-β and IL-10). Furthermore, increased levels in CD4⁺ and CD8⁺ T-cell subsets, presenting intracytoplasmic proinflammatory cytokine balance, have been associated with a resistance profile against CVL. In contrast, a polyclonal B-cell expansion towards plasma cell differentiation contributes to high antibody production, which is the hallmark of symptomatic dogs associated with high susceptibility in CVL. Finally, the different studies used to analyze biomarkers have been incorporated into vaccine immunogenicity and protection evaluations. Those biomarkers identified as resistance or susceptibility markers in CVL have been used to evaluate the vaccine performance against L. infantum in a kennel trial conducted before the field trial in an area known to be endemic for visceral leishmaniasis. This rationale has been a guiding force in the testing and selection of the best vaccine candidates against CVL and provides a way for the veterinary industry to register commercial immunobiological products.

Leishmania infantum-specific IFN-γ production in stimulated blood from cats living in areas where canine leishmaniosis is endemic

Background

Feline leishmaniosis caused by Leishmania infantum is considered a rare disease in endemic areas, whereas subclinical infections are common. Immune response plays a key role in driving the course of L. infantum infection in other host species; however, the feline cell-mediated immune response to L. infantum infection has not yet been investigated. The aim of this study was to determine the cell-mediated immune response specific to L. infantum by means of interferon (IFN)-γ release in whole blood assay from cats living in endemic areas (66 in Sicily and 113 in Catalonia) and to compare with antibody levels to L. infantum [enzyme-linked immunosorbent assay (ELISA) and immunofluorescence antibody test (IFAT)], blood parasite load and retroviral infections.

Results

Most cats (n = 140) were L. infantum antibody negative and only 22% (n = 39) were positive. Only 9 and 2% of tested cats had a feline immunodeficency virus (FIV) infection or a feline leukemia virus (FeLV) infection, respectively. Thirty-two cats out of 179 (18%) produced IFN-γ after stimulation with L. infantum soluble antigen (LSA) while the majority of cats (93%) produced IFN-γ after stimulation with concanavalin A (ConA). Six LSA-IFN-γ-producer cats were seropositive (three to ELISA and five to IFAT) but they were polymerase chain reaction (PCR) negative, while only one cat was antibody- and PCR-positive. Significant positive correlations were found between IFN-γ concentrations after stimulation with LSA and ConA, and between serology and PCR testing. No association was found between FIV status and LSA or ConA-IFN-γ production. Combining PCR, serology and specific IFN-γ concentration results, we found that 36% of cats studied were exposed to L. infantum.

Conclusions

As expected, cats from endemic areas produce IFN-γ after ex vivo blood stimulation with LSA and therefore are able to activate a cell-mediated adaptive immune response against the parasite that is variably associated with antibody or blood PCR positivity. The association of this assay to serological and molecular tests provides a better estimate of cat exposure to L. infantum.

Cytokine Effect of TLR3, TLR4, and TLR7 Agonists Alone or Associated with Leishmania infantum Antigen on Blood from Dogs

Activation of toll-like receptors (TLRs) has been shown to play an important role in leishmaniosis by enhancing the parasite specific immune responses to control infection. However, the role of TLR agonists has not been studied in detail in dogs. The aim of this study was to determine the effect of TLR3, TLR4, and TLR7 agonists (TLR3a, TLR4a, and TLR7a) alone or in combination with Leishmania infantum antigen (LSA) on TNF-α and IL-6 production in blood from dogs living in endemic areas of canine leishmaniosis (CanL). Twenty-four healthy dogs from Catalonia (n=14) and Ibizan hound dogs from the island of Mallorca (n=10) were enrolled. Whole blood with TLR3a, TLR4a, and TLR7a alone or combined with LSA were cultured separately, and IFN-γ, TNF-α, and IL-6 were measured by ELISA. A significant increase of TNF-α was found for all conditions studied compared to medium alone. Stimulation with TLR4a (p=0.0001) and TLR7a (p=0.005) presented a significantly marked increase in TNF-α and IL-6 production compared to TLR3a. Importantly, significantly higher TNF-α production was found in LSA+TLR4a (p=0.0001) stimulated blood and LSA+TLR7a (p=0.005) compared to LSA alone. All dogs showed higher TNF-α production after LSA+TLR7a compared to TLR7a (p=0.047) and LSA+TLR3a compared to TLR3a (p=0.052). These data indicate a marked inflammatory cytokine effect of TLR4a and TLR7a on blood from healthy dogs living in endemic areas of CanL. Additionally, LSA+TLR7a promoted a synergistic proinflammatory effect with TNF-α in all dogs. Those findings suggest an active role of TLRs in proinflammatory responses, which might be strongly involved in the process of disease resolution.

Biomarkers Associated With Leishmania infantum Exposure, Infection, and Disease in Dogs

Canine leishmaniosis (CanL) is a vector-borne disease caused by the protozoan Leishmania (Leishmania) infantum species [syn. L. (L.) infantum chagasi species in the Americas] which is transmitted by the bite of a female phlebotomine sand fly. This parasitosis is endemic and affect millions of dogs in Asia, the Americas and the Mediterranean basin. Domestic dogs are the main hosts and the main reservoir hosts for human zoonotic leishmaniosis. The outcome of infection is a consequence of intricate interactions between the protozoan and the immunological and genetic background of the host. Clinical manifestations can range from subclinical infection to very severe disease. Early detection of infected dogs, their close surveillance and treatment are essential to control the dissemination of the parasite among other dogs, being also a pivotal element for the control of human zoonotic leishmaniosis. Hence, the identification of biomarkers for the confirmation of Leishmania infection, disease and determination of an appropriate treatment would represent an important tool to assist clinicians in diagnosis, monitoring and in giving a realistic prognosis to subclinical infected and sick dogs. Here, we review the recent advances in the identification of Leishmania infantum biomarkers, focusing on those related to parasite exposure, susceptibility to infection and disease development. Markers related to the pathogenesis of the disease and to monitoring the evolution of leishmaniosis and treatment outcome are also summarized. Data emphasizes the complexity of parasite-host interactions and that a single biomarker cannot be used alone for CanL diagnosis or prognosis. Nevertheless, results are encouraging and future research to explore the potential clinical application of biomarkers is warranted.

Modulation of goat monocyte function by HCcyst-2, a secreted cystatin from Haemonchus contortus

Modulation and suppression of the host immune response by nematode parasites have been reported extensively and the cysteine protease inhibitor (cystatin) is identified as one of the major immunomodulator. In the present study, we cloned and produced recombinant cystatin protein from nematode parasite Haemonchus contortus (rHCcyst-2) and investigated its immunomodulatory effects on goat monocyte. rHCcyst-2 protein is biologically functional as shown by its ability to inhibit the protease activity of cathepsin L, cathepsin B and papain. Immunohistochemical test demonstrated that the native HCcyst-2 protein was predominantly localized at the body surface and internal surface of the worm's gut. We demonstrated that rHCcyst-2 could be distinguished by antisera from goats experimentally infected with H. contortus and could uptake by goat monocytes. The immunomodulatory effects of HCcyst-2 on cytokine secretion, MHC molecule expression, NO production and phagocytosis were observed by co-incubation of rHCcyst-2 with goat monocytes. The results showed that the interaction of rHCcyst-2 decreased the production of TNF-α, IL-1β and IL-12p40. However, it significantly increased the secretion of IL-10 in goat monocytes. After rHCcyst-2 exposure, the expression of MHC-II on goat monocytes was inhibited. Moreover, rHCcyst-2 could up-regulate the LPS induced NO production of goat monocytes. Phagocytotic assay by FITC-dextran internalization showed that rHCcyst-2 inhibited the phagocytosis of goat monocytes. Our findings provided potential target as immunoregulator, and will be helpful to illustrate the molecular basis of host–parasite interactions and search for new potential molecule as vaccine and drug target candidate.

Cellular apoptosis and nitric oxide production in PBMC and spleen from dogs with visceral leishmaniasis

Nitric oxide (NO) is involved in the death of the Leishmania parasite and regulation of apoptosis. We quantified the frequency of cells producing NO and its levels in the peripheral blood mononuclear cells (PBMC), leukocytes from spleen in Visceral Leishmaniasis (VL) symptomatic dogs and correlated NO levels with apoptosis and parasite load in the spleen. The percentage of NO+ cells and CD14+/NO+ was higher in PBMC and spleen cells in infected dogs than in controls. The levels of NO+ and CD14+/NO+ cells was higher in PBMC, but lower spleen of dogs infected than compared to control. Late apoptosis rates increased in PBMC and spleen of infected dogs compared to controls, and the NO levels and apoptosis not showed correlation. There was a positive correlation between the percentage of cells producing NO in the spleen and parasite load. The NO participates in the immune response in the canine VL, but it is not apoptosis inducer.

Clinical and immunopathological findings during long term follow-up in Leishmania infantum experimentally infected dogs

Canine Visceral Leishmaniasis (CVL) is caused by Leishmania infantum, which in the New World is transmitted by Lutzomyia longipalpis. While prospective clinical and immunological assessments of dogs experimentally challenged with L. infantum have been previously reported over a relatively short follow-up period, the long-term characterization of infected animals has not been performed to date. We evaluated dogs in a subclinical state for six years following experimental infection with L. infantum and Lu. longipalpis saliva, via an intradermal route, to characterize clinical, parasitological and immunological parameters arising from L. infantum experimental infection. We also assess these parameters in a group of naturally infected animals. The immune profiles of the experimentally and naturally infected animals exhibited increases of IFN-γ, IL-6 and IL-18, and decreases in TNF, IL-2, IL-8 and CXCL1, compared to controls. Our results indicate that over a six-year follow-up post-challenge, subclinically infected dogs presented low CVL clinical scores despite the persistence of Leishmania parasites in the lymph nodes, spleen and skin. Similarities observed among immune profiles in the context of experimental and natural infection seem to suggest that an enduring activation of the host immune response may lead to the control of parasite growth, thereby limiting disease severity.

Characterization of a secreted cystatin of the parasitic nematode Haemonchus contortus and its immune-modulatory effect on goat monocytes

BACKGROUND

Haemonchosis is a disease of the small ruminant caused by a nematode parasite Haemonchus contortus, and it is most important and alarming challenges to the small ruminant's production. The infection of the H. contortus could cause high economic losses worldwide. H. contortus is a blood feeding parasite which penetrates into the abomasal mucosa to feed the blood of the host and causing the anemia and decreased total plasma protein. Modulation and suppression of the immune response of the host by nematode parasites have been reported extensively, and the cysteine protease inhibitor (cystatin) is identified as one of the major immunomodulators.

METHODS

The recombinant protein of HCcyst-3 was expressed in a histidine-tagged fusion soluble form in Escherichia coli, and its inhibitory activity against cathepsin L, B, as well as papain, were identified by fluorogenic substrate analysis. Native HCcyst-3 protein was localized by an Immunohistochemical test. The immunomodulatory effects of HCcyst-3 on cytokine secretion, MHC molecule expression, NO production and phagocytosis were observed by co-incubation of rHCcyst-3 with goat monocytes.

RESULTS

We cloned and produced recombinant cystatin protein from H. contortus (rHCcyst-3) and investigated its immunomodulatory effects on goat monocyte. The rHCcyst-3 protein is biologically functional as shown by its ability to inhibit the protease activity of cathepsin L, cathepsin B, and papain. The immunohistochemical test demonstrated that the native HCcyst-3 protein was predominantly localized at the body surface and internal surface of the worm's gut. We demonstrated that rHCcyst-3 could be distinguished by antisera from goat experimentally infected with H. contortus and could uptake by goat monocytes. The results showed that the engagement of rHCcyst-3 decreased the production of TNF-α, IL-1β and IL-12p40. However, it significantly increased the secretion of IL-10 and TGF-β1 in goat monocytes. After rHCcyst-3 exposure, the expression of MHC-II on goat monocytes was restricted. Moreover, rHCcyst-3 could upregulate LPS induced NO production of goat monocytes. Phagocytotic assay by FITC-dextran internalization showed that rHCcyst-3 inhibited the phagocytosis of goat monocytes.

CONCLUSIONS

Our results suggested that the recombinant cystatin from H. contortus (rHCcyst-3) significantly modulated goat monocyte function in multiple aspects.

In situ CUTANEOUS CELLULAR IMMUNE RESPONSE IN DOGS NATURALLY AFFECTED BY VISCERAL LEISHMANIASIS

Thirty-eight dogs naturally affected by visceral leishmaniasis were recruited in Araçatuba, São Paulo State, Brazil - an endemic area for visceral leishmaniasis. The animals were distributed into one of two groups, according to their clinical and laboratory features, as either symptomatic or asymptomatic dogs. Correlations between clinical features and inflammatory patterns, cellular immune responses, and parasitism in the macroscopically uninjured skin of the ear were investigated. Histological skin patterns were similar in both groups, and were generally characterized by a mild to intense inflammatory infiltrate in the dermis, mainly consisting of mononuclear cells. There was no difference in the number of parasites in the skin (amastigotes/mm²) between the two groups. Concerning the characterization of the cellular immune response, the number of positive inducible nitric oxide synthase (iNOS⁺⁾ cells was higher in the dermis of symptomatic than in asymptomatic dogs (p = 0.0368). A positive correlation between parasite density and macrophages density (p = 0.031), CD4⁺ T-cells (p = 0.015), and CD8⁺ T-cells (p = 0.023) was observed. Furthermore, a positive correlation between density of iNOS⁺ cells and CD3⁺ T-cells (p = 0.005), CD4⁺ T-cells (p = 0.001), and CD8⁺ T-cells (p = 0.0001) was also found. The results showed the existence of a non-specific chronic inflammatory infiltrate in the dermis of dogs affected by visceral leishmaniasis, characterized by the presence of activated macrophages and T-lymphocytes, associated to cutaneous parasitism, independent of clinical status.

Heterogeneity of macrophages in canine histiocytic ulcerative colitis

Histiocytic ulcerative colitis (HUC) is a chronic enteropathy which most notably occurs in Boxer dogs and French bulldogs. The inflamed mucosa is hallmarked by large, foamy, periodic acid–Schiff (PAS)-positive macrophages infiltrating the colonic mucosa. As little is known about their origin and phenotype, an immunohistochemical study was performed using different macrophage markers. Generally, canine colonic macrophages showed high expression of ionised calcium-binding adaptor molecule 1 and MHC class II. In canine HUC, macrophages revealed up-regulation of lysozyme and L1 Ag but decreased CD163 expression compared with controls, suggesting them to be pro-inflammatory cells, whereas the healthy colonic mucosa was characterised by an anti-inflammatory macrophage phenotype. In addition, PAS reaction was used to discriminate macrophage subpopulations. PAS– macrophages displayed higher expression of L1 Ag and CD64, whereas PAS+ cells, which were only present in HUC patients, were characterised by increased expression of lysozyme, inducible nitric oxide synthase and CD204. This indicates PAS+ cells to be mature macrophages contributing to the inflammatory process, which are most likely maintained by differentiation of immature PAS– macrophages continuously recruited from blood monocytes. In summary, macrophage heterogeneity in canine HUC probably illustrates their different maturation states and functions compared with the healthy animals.

Insights on adaptive and innate immunity in canine leishmaniosis

Canine leishmaniosis (CanL) is caused by the parasite Leishmania infantum and is a systemic disease, which can present with variable clinical signs, and clinicopathological abnormalities. Clinical manifestations can range from subclinical infection to very severe systemic disease. Leishmaniosis is categorized as a neglected tropical disease and the complex immune responses associated with Leishmania species makes therapeutic treatments and vaccine development challenging for both dogs and humans. In this review, we summarize innate and adaptive immune responses associated with L. infantum infection in dogs, and we discuss the problems associated with the disease as well as potential solutions and the future direction of required research to help control the parasite.

Polymerase chain reaction detection and inducible nitric-oxide synthase expression of Leishmania major in mice inoculated by two different routes

Introduction:

Leishmania major needs a sensitive and specific method for proper diagnosis. This study aims to study the course and histopathology of L. major in certain tissues of experimentally infected BALB/c mice after subcutaneous (sc) and intraperitoneal (ip) inoculation.

Materials and Methods:

After infecting BALB/c mice using sc and ip inoculation, the histopathology was studied. The kinetoplastic DNA polymerase chain reaction (PCR) for its molecular detection and detect the inducible nitric-oxide synthase (iNOS) pattern during the first 3 months of infection.

Result:

PCR could detect the presence of L. major in all spleens, lymph nodes, and skin ulcers by both inoculation routes while (33%) and (42%) of livers were positive after sc and ip routes, respectively. Chronic inflammatory cell infiltrates with capsulitis was found in the spleen, lymph nodes, and liver. Granulomas were found in the spleen and liver. There was a statistically significant difference in iNOS expression along the experiment in the spleen and lymph nodes by both routes and in the liver by ip only. Apart from the liver, iNOS could not be detected on the 2^nd week postinfection and was high after 1 month for both routes in all samples; a moderate decrease at 2 months and the highest decrease were detected after 3 months.

Conclusions:

L. major inoculation by both routes produce visceral disease in mice, and kinetoplastic DNA PCR can detect its presence from the 2^nd week up to the 3^rd month postinfection. The iNOS expression was high at 1 and 2 months and remained throughout the 3 months of the experiment; which plays an important role in the disease course and control.

Leishmania infection in a population of dogs: an epidemiological investigation relating to visceral leishmaniasis control

Identification of factors associated with Leishmania infection in dogs is essential for targeting visceral leishmaniasis control actions. Thus, the present study analyzed some of these factors in a population of dogs in a Brazilian municipality, along with the limitations of control strategies implemented there. The association between the exposure variables and occurrences of infection was analyzed through logistic regression models. The disease control interventions were treated qualitatively. Out of the 755 animals examined, 13.6% (103/755) were seropositive. Of these, 23.3% (24/103) were asymptomatic and 76.7% (79/103) presented at least one clinical sign possibly associated with visceral leishmaniasis. With weak associations, purebred, shorthaired, over 5 years of age, male and large dogs were more prone to infection. The latter two variables formed the final regression model and the association with dog size was statistically significant. The control strategies developed presented limitations and a great number of seronegative dogs was culled. The data presented contribute towards better understanding of the dynamics of infection in canine visceral leishmaniasis and indicate that actions aimed towards adequate implementation of Visceral Leishmaniasis control program in Brazilian endemic areas should be prioritized.

Immunohistochemical characterisation of parasitic pneumonias of dolphins stranded in the Canary Islands

This is the first work that applies immunohistochemistry in the characterisation of the inflammatory infiltrate of verminous bronchopneumonia associated with lungworm parasites in stranded dolphins. Samples from three different species (Stenella coerulealba, Stenella frontalis and Delphinus delphis) stranded in the Canary Islands were used. The most common findings found in these animals varied from bronchitis to verminous bronchopneumonia with different degree of severity. The immunohistochemical study showed variable expressions of Lysozyme, MHC-II, iNOS and IgG. The main population presenting in the inflammatory infiltrates were CD3(+) lymphocytes. However, moderate number of Foxp3(+) lymphocytes was found in lymph nodes even though no Foxp3(+) cells were found in lung lesions in any of the samples analysed. This study revealed that lung lesions showed a chronic inflammatory infiltrate mainly composed by lymphocytes CD3(+). Deeper studies are needed in order to provide a more complete scope about the infiltrates involved in these types of lesions.

Overexpressed Macrophage Mannose Receptor Targeted Nanocapsules- Mediated Cargo Delivery Approach for Eradication of Resident Parasite: In Vitro and In Vivo Studies

PURPOSE

Since, Leishmania protozoans are obligate intracellular parasites of macrophages, an immunopotentiating macrophage-specific Amphotericin B (AB) delivery system would be ideally appropriate to increase its superiority for leishmaniasis treatment and to eliminate undesirable toxicity. Herein, we report AB entrapped mannose grafted chitosan nanocapsules (MnosCNc-AB) that results in effective treatment of visceral leishmaniasis, while also enhancing L. donovani specific T-cell immune responses in infected host.

METHODS

MnosCNc-AB were prepared via synthesized mannosylated chitosan deposition on interface of oil/water nanoemulsion intermediate and were characterized. J774A.1 macrophage uptake potential, antileishmanial activity and immunomodulatory profile were evaluated in hamster. Tissue localization, biodistribution and toxicity profile were also investigated.

RESULTS

MnosCNc-AB had nanometric size (197.8 ± 8.84 nm), unimodal distribution (0.115 ± 0.04), positive zeta potential (+31.7 ± 1.03 mV) and 97.5 ± 1.13% cargo encapsulation efficiency. Superior macrophage internalization of mannosylated chitosan nanocapsules compared to unmodified chitosan nanocapsules was observed by fluorescence-based assessment, further confirmed by rapid blood clearance and, greater localization and higher accumulation in macrophage rich liver and spleen. While, MnosCNc-AB mediated cargo distribution to kidney decreased. Augmented in vitro antileishmanial activity and in vivo pro-inflammatory mediator's expression were observed with MnosCNc-AB, led to significant reduction (∼90%) in splenic parasite burden.

CONCLUSIONS

Results demonstrated that mannose ligand grafted chitosan nanocapsules could improve selective delivery of AB into macrophages via interactions with overexpressed mannose receptors thus reduce undesirable toxicity. Study provides evidence for MnosCNc-AB potential to leishmaniasis therapeutics and presents valuable therapeutic strategies for combating chronic macrophage-resident microbial infections.

Canine Leishmania vaccines: still a long way to go

Dogs are the main reservoir host for zoonotic visceral leishmaniasis, a sand fly-borne disease caused by Leishmania infantum. In endemic areas, "susceptible" dogs suffer from a severe disease characterized by chronic polymorphic viscerocutaneous signs that manifest several months from the exposure, whereas "resistant" dogs can remain subclinically infected for years or lifelong. The protective immune response to Leishmania is cell-mediated; for visceralizing Leishmania species a mixed T helper (Th)1/Th2 response with a dominant Th1 profile is required for protection. The activation of the adaptive immune system in naturally resistant dogs is revealed by parasite-specific lymphoproliferation, delayed-type hypersensitivity, the production of interferon-γ and tumour necrosis factor-α cytokines, and enhanced macrophage leishmanicidal activity via nitric oxide. Hence, an effective canine Leishmania vaccine should induce strong and long-lasting Th1-dominated immunity to control both infection progression and the parasite transmissibility via the vector. Preclinical research in rodent models has evaluated the efficacy of several categories of Leishmania antigens including killed parasites, cell purified fractions, parasite protein components or subunits, single or multiple chimeric recombinant proteins, plasmid DNA and viral particles encoding parasite virulence factors. Promising antigen(s)/adjuvant combinations from each of the above categories have also been tested in dogs; they mostly resulted in limited or no protection in Phase I-II studies (designed to test vaccine safety, immunogenicity and laboratory-induced protection) in which vaccinated dogs were challenged by the artificial intravenous injection of high-load L. infantum promastigotes. The recombinant A2 antigen plus saponin conferred about 40% protection against infection by this challenge system and has been registered in Brazil as a canine vaccine (LeishTec(®)). An increasing number of efficacy studies have privileged the use of natural challenge consisting in the long-term exposure of vaccinated dogs in endemic settings (Phase III). A 2-year field model including regular assessments by a set of standard diagnostic markers useful for an accurate infection staging has been developed. Again, most of the vaccines tested by this system, which included several antigen categories and adjuvants, failed to protect against infection and disease. Only two vaccines, consisting of parasite purified fractions with saponin derivative adjuvants, showed to confer significant protection against disease and death under natural conditions, and have been registered as canine vaccines: FML-QuilA (Leishmune(®)) in Brazil, and LiESP/QA-21 (CaniLeish(®)) in Europe.

A randomised, double-blind, controlled efficacy trial of the LiESP/QA-21 vaccine in naïve dogs exposed to two leishmania infantum transmission seasons

Canine leishmaniasis is an important zoonosis caused by uncontrolled infection with Leishmania infantum, where an inappropriate immune response is not only responsible for permitting this intracellular parasite to multiply, but is also responsible for several of the pathological processes seen in this disease. Effective canine vaccines are therefore a highly desirable prevention tool. In this randomised, double-blinded, controlled trial, the efficacy of the LiESP/QA-21 vaccine (CaniLeish, Virbac, France) was assessed by exposing 90 naïve dogs to natural L. infantum infection during 2 consecutive transmission seasons, in two highly endemic areas of the Mediterranean basin. Regular PCR, culture, serological and clinical examinations were performed, and the infection/disease status of the dogs was classified at each examination. The vaccine was well-tolerated, and provided a significant reduction in the risk of progressing to uncontrolled active infection (p = 0.025) or symptomatic disease (p = 0.046), with an efficacy of 68.4% and a protection rate of 92.7%. The probability of becoming PCR positive was similar between groups, but the probability of returning to a PCR negative condition was higher in the vaccinated group (p = 0.04). In conclusion, we confirmed the interest of using this vaccine as part of a comprehensive control program for canine leishmaniasis, and validated the use of a protocol based on regular in-depth assessments over time to assess the efficacy of a canine leishmaniasis vaccine.

Canine leishmaniasis is caused by uncontrolled infection with Leishmania infantum. The dog is also the principle reservoir of this parasite which can infect humans. The key determinant of the outcome of infection is the ability of the dog's immune system to respond appropriately. This should be mainly cell-mediated immunity; the antibody responses often desired for viral or bacterial infections are not protective. Therefore, vaccines capable of inducing this cell-mediated immune profile are a desirable prevention tool. Previous studies with CaniLeish (consisting of the parasite's excreted-secreted proteins with an adjuvant) have demonstrated the ability of this vaccine to induce an appropriate immune profile and to protect against an intravenous challenge, as well as to reduce the risk of transmission of the parasite to the sandfly vector. This paper reports a study where vaccinated dogs were exposed to natural parasite transmission over two full seasons in two Mediterranean locations (one in Italy and one in Spain). Data from the unvaccinated control group confirmed that the levels of exposure were high. We demonstrated that the vaccine significantly reduces the risk of progressive infections and disease confirming the interest of using vaccination as part of a comprehensive control program for this disease.

Expression of inducible nitric oxide synthase in macrophages inversely correlates with parasitism of lymphoid tissues in dogs with visceral leishmaniasis

BACKGROUND

There are only a few studies reporting the role of nitric oxide metabolites for controlling macrophage intracellular parasitism, and these are controversial. Therefore, the present study aimed to evaluate the expression of inducible nitric oxide synthase (iNOS) in the lymph nodes and spleen of dogs affected by visceral leishmaniasis through immunohistochemistry and to determine its correlation with tissue parasite burden and serum interferon (IFN)-γ levels. Twenty-eight dogs were selected and assigned to one of two groups, symptomatic (n = 18) and asymptomatic (n = 10), according to clinical status and laboratory evaluation. A negative control group (n = 6) from a non-endemic region for visceral leishmaniasis was included as well.

RESULTS

Parasite density (amastigotes/mm2) was similar between clinical groups in the lymph nodes (P = 0.2401) and spleen (P = 0.8869). The density of iNOS⁺ cells was higher in infected dogs compared to controls (P < 0.05), without a significant difference in lymph node (P = 0.3257) and spleen (P = 0.5940) densities between symptomatic and asymptomatic dogs. A positive correlation was found between the number of iNOS⁺ cells in lymph nodes and interferon-γ levels (r = 0.3776; P = 0.0303), and there was a negative correlation between parasites and iNOS⁺ cell densities both in lymph nodes (r = -0.5341; P = 0.0034) and spleen (r = -0.4669; P = 0.0329).

CONCLUSION

The negative correlation observed between tissue parasitism and the expression of iNOS may be a reflection of NO acting on the control of parasites.

A potential link among antioxidant enzymes, histopathology and trace elements in canine visceral leishmaniasis

Canine visceral leishmaniasis (CVL) is a severe and fatal systemic chronic inflammatory disease. We investigated the alterations in, and potential associations among, antioxidant enzymes, trace elements and histopathology in CVL. Blood and tissue levels of Cu-Zn superoxide dismutase, catalase and glutathione peroxidase were measured in mixed-breed dogs naturally infected with Leishmania infantum chagasi, symptomatic (n = 19) and asymptomatic (n = 11). Serum levels of copper, iron, zinc, selenium and nitric oxide, and plasma lipid peroxidation were measured. Histological and morphometric analyses were conducted of lesions in liver, spleen and lymph nodes. We found lower blood catalase and glutathione peroxidase activity to be correlated with lower iron and selenium respectively. However, higher activity of Cu-Zn superoxide dismutase was not correlated with the increase in copper and decreased in zinc observed in infected animals compared to controls. Organ tissue was characterized by lower enzyme activity in infected dogs than in controls, but this was not correlated with trace elements. Lipid peroxidation was higher in symptomatic than in asymptomatic and control dogs and was associated with lesions such as chronic inflammatory reaction, congestion, haemosiderin and fibrosis. Systemic iron deposition was observed primarily in the symptomatic dogs showing a higher tissue parasite load. Dogs with symptomatic CVL displayed enhanced LPO and Fe tissue deposition associated with decreased levels of antioxidant enzymes. These results showed new points in the pathology of CVL and might open new treatment perspectives associated with antioxidants and the role of iron in the pathogenesis of CVL.

Primary vaccination with the LiESP/QA-21 vaccine (CaniLeish) produces a cell-mediated immune response which is still present 1 year later

Canine leishmaniasis, an important zoonotic disease of dogs, is the result of an ineffective and inappropriate immune response to infection with Leishmania infantum. It is widely accepted that the appropriate immune response is characterised by a T-helper (Th)1-dominated profile in an overall mixed Th1/Th2 response. The absence of a strong Th1 response is associated with progression to the clinical disease. Thus, there is a need for an effective vaccine that could modulate the immune response to a more appropriate profile against the parasite. In this study we measured the impact of the LiESP/QA-21 canine vaccine, recently launched commercially in Europe, on selected humoral and cellular immune markers for one year after a primary vaccination course. The humoral response to vaccination was characterised by a predominantly IgG2 profile. Vaccinated dogs developed long-lasting cell-mediated immune responses against L. infantum, specifically with a stronger ability of macrophages to reduce intracellular parasite burdens in co-culture with autologous lymphocytes compared to control dogs (p=0.0002), which was correlated with induction of inducible nitric oxide synthase (iNOS) and production of nitric oxide (NO) derivatives. These results confirm that vaccination with LiESP/QA-21 is capable of inducing an appropriate Th1-dominated immune profile which persists for a full year.

DL. Improvement in clinical signs and cellular immunity of dogs with visceral leishmaniasis using the immunomodulator P-MAPA

This study investigated the immunotherapeutic potential of the protein aggregate magnesium-ammonium phospholinoleate-palmitoleate anhydride immuno-modulator (P-MAPA) on canine visceral leishmaniasis. Twenty mongrel dogs presenting clinical symptoms compatible with leishmaniasis and diagnosis confirmed by the detection of anti-leishmania antibodies were studied. Ten dogs received 15 doses of the immunomodulator (2.0 mg/kg) intramuscularly, and 10 received saline as a placebo. Skin and peripheral blood samples were collected following administration of the immunomodulator. The groups were followed to observe for clinical signals of remission; parasite load in the skin biopsies using real-time PCR, the cytokines IL-2, IL-10 and IFN-γ in the supernatant of peripheral blood mononuclear cells stimulated in vitro with either total promastigote antigen or phytohemagglutinin measured by capture ELISA, and changes in CD4⁺ and CD8⁺ T cell subpopulations evaluated by flow cytometry. Comparison between the groups showed that treatment with the immunomodulator promoted improvement in clinical signs and a significant reduction in parasite load in the skin. In peripheral blood mononuclear cell cultures, supernatants showed a decrease in IL-10 levels and an increase in IL-2 and IFN-γ. An increase in CD8⁺ T cells was observed in peripheral blood. In addition, the in vitro leishmanicidal action of P-MAPA was investigated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and no leishmanicidal activity was detected. These findings suggest that P-MAPA has potential as an immunotherapeutic drug in canine visceral leishmaniasis, since it assists in reestablishing partial immunocompetence of infected dogs.

Expression of leptin and iNOS in oral melanomas in dogs

BACKGROUND

Oral melanoma (OM) in dogs is an aggressive malignancy, with clinical behavior resembling cutaneous melanomas in humans. Melanoma in humans is promoted by an inflammatory environment that is contributed to by leptin and inducible nitric oxide synthase (iNOS).

OBJECTIVE

To determine if the patterns of leptin and iNOS expression are similar in OM in dogs and cutaneous melanomas in humans.

ANIMALS

Twenty client-owned dogs.

METHODS

Retrospective case study. Immunostaining of the OM tumors from each dog was scored for percentage and intensity of leptin and iNOS expression. Mitotic index was used as an indicator of tumor aggression.

RESULTS

Leptin was detected in ≥75% of the tumor cells in specimens from 11 dogs. One tumor expressed leptin in ≤25% of the cells. The intensity of leptin expression was variable with 6, 9, and 5 cases exhibiting low-, moderate-, and high-intensity staining, respectively. OM with the lowest percentage of iNOS positive cells displayed the highest mitotic indices (P = .006, ANOVA).

CONCLUSIONS AND CLINICAL IMPORTANCE

The expression of leptin is a common finding in melanomas in dogs. These data suggest that the possibility of future clinical applications, such as measuring the concentrations of plasma leptin as a screening tool or leptin as a target for therapy. The relevance of iNOS is not as clear in dogs with OM, for which other directed therapeutics might be more appropriate.

Immunopathological study of parasitic cholangitis in cetaceans

This paper describes the immunophenotype of cellular inflammatory infiltrates in chronic cholangitis in six common dolphins (Delphinus delphis), four striped dolphins (Stenella coeruleoalba), three Atlantic spotted dolphins (Stenella frontalis) and one pygmy sperm whale (Kogia Breviceps) found stranded along the coasts of the Canary Islands (Spain). A panel of 5 antibodies previously tested in dolphins (anti-CD3, -IgG, -MHC class II, -S100 protein and -lysozyme) were used. The present work also reports cross reactivity with dolphin antigens of two antibodies not used to date in dolphins (anti-mouse iNOS and anti-mouse Foxp3). The most common type of cholangitis found was chronic granulomatous cholangitis, associated with the presence of the parasite Campula spp., or its eggs in bile ducts. The cellular composition of the hepatic inflammatory infiltrate associated to chronic parasitic cholangitis was closely similar to that found in the cortex of control lymph nodes, including the presence of S100(+) and MHC class II(+) dendritic-like cells in lymphoid follicles and interfollicular areas. Only occasional macrophages expressed iNOS, whereas Foxp3(+) lymphocytes were not found in any of the lesions described in the different types of cholangitis.

Use of a LiESP/QA-21 vaccine (CaniLeish) stimulates an appropriate Th1-dominated cell-mediated immune response in dogs

Canine leishmaniasis is an important zoonotic disease of dogs. The clinical outcome of infection is variable, with the efficiency of the immune response being the key determining factor. There is now a general consensus that a predominant Th1 immune profile in an overall mixed Th1/Th2 response is associated with resistance in dogs, and the absence of a strong Th1 influence is associated with a progression to clinical disease. As a result, there has been a growing demand for vaccines that can induce a specific, strong Th1 response. In this study, we measured the impact of a primary course of a newly available LiESP/QA-21 vaccine on selected humoral and cellular markers of the canine immune response during the onset of immunity. All vaccinated dogs developed a humoral response characterised by IgG2 production. More importantly, vaccinated dogs developed significantly stronger cell-mediated immunity responses than did control dogs. Vaccination induced specific cellular reactivity to soluble Leishmania antigens, with a Leishmania-specific lymphoproliferation (p = 0.0072), characterised by an increased population of T lymphocytes producing IFN-γ (p = 0.0021) and a significant ability of macrophages to reduce intracellular parasite burdens in vitro after co-culture with autologous lymphocytes (p = 0.0014). These responses were correlated with induction of the NOS pathway and production of NO derivatives, which has been shown to be an important leishmanicidal mechanism. These results confirm that vaccination with LiESP/QA-21 induces an appropriate Th1-profile cell-mediated response within three weeks of completing the primary course, and that this response effectively reduces the parasite load in pre-infected macrophages in vitro.

The dog is the principle reservoir of Leishmania infantum, a parasite spread from dog to dog by a sandfly vector. The reduction of canine leishmaniasis is therefore a key factor in the overall management of the epidemiology of this parasite. There is also a need for effective prevention on welfare grounds because of the clinical severity of this potentially fatal disease in dogs. The key factor determining the outcome of infection in dogs is the ability to mount a Th1-dominated immune response, because this is more effective against intracellular pathogens such as L. infantum. Until now, in Europe, only measures to reduce sandfly bites have been available, and for many years there has been a strong demand for a vaccine that provides specific and effective immunity. The recent launch of the first European canine leishmaniasis vaccine (CaniLeish) has provided a means to achieve this, but data on its impact on the dog's immune system are required. The data presented here demonstrate the specific stimulation of an effective Th1-dominated anti-L. infantum response within three weeks of the administration of the vaccine, and provides a basis for the understanding of the mode of action of this new tool.

Toll receptors type-2 and CR3 expression of canine monocytes and its correlation with immunohistochemistry and xenodiagnosis in visceral leishmaniasis

The aim of the present study was to investigate TLR2 expression in peripheral blood monocytes from dogs naturally infected with Leishmania (Leishmania) infantum to determine whether it correlates with CD11b/CD18 (CR3) expression, and to evaluate the potential of dogs as sources of infection using phlebotomine xenodiagnosis. Forty eight dogs were serologically diagnosed with L. infantum infection by indirect immunofluorescence antibody test (IFAT) and enzyme linked immunosorbent assay (ELISA). Parasitological exams from bone-marrow aspirates were positive by PCR analysis. All dogs were clinical defined as symptomatic. Ear skin tissue samples were obtained for immunohistochemistry (IHQ) analysis. The potential of these dogs as a source of infection using phlebotomine xenodiagnosis (XENO) was evaluated. Flow cytometry was carried out on peripheral blood mononuclear cells using superficial receptors including CD14, CD11b, TLR2 and MHCII. IHQ ear skin tissue parasite load and XENO where done where we found a strict correlation (r = 0.5373). Dogs with higher expression of MFI of CD11b inside CD14 monocytes were represented by dogs without parasite ear tissue load that were unable to infect phlebotomines (IHQ⁻/XENO⁻). Dogs with lower expression of MFI of CD11b inside CD14 monocytes were represented by dogs with parasite ear tissue load and able to infect phlebotomines (IHQ⁺/XENO⁺) (p = 0,0032). Comparable results were obtained for MFI of MHCII (p = 0.0054). In addition, considering the population frequency of CD11b⁺TLR2⁺ and CD11b⁺MHCII⁺, higher values were obtained from dogs with IHQ⁻/XENO⁻ than dogs with IHQ⁺/XENO⁺ (p = 0.01; p = 0.0048, respectively). These data, together with the TLR2 and NO assays results (CD11b⁺TLR2⁺ and NO with higher values for dogs with IHQ⁻/XENO⁻ than dogs with IHQ⁺/XENO⁺, led to the conclusion that IHQ⁻/XENO⁻ dogs are more resistant or could modulate the cellular immune response essential for Leishmania tissue clearance.

Molecular cloning and characterization of cystatin, a cysteine protease inhibitor, from Angiostrongylus cantonensis

Cystatins are thiol proteinase inhibitors ubiquitously present in mammalian body and serve various important physiological functions. In the present study, a novel cystatin molecule (AcCystatin) was cloned from a cDNA library of Angiostrongylus cantonensis fourth-stage larvae. The putative 14-kDa protein contained 120 residues with cystatin-conserved motifs known to interact with the active site of cysteine peptidases and showed high identities with cystatins from other nematodes. RT-PCR analysis revealed that the expression pattern of AcCystatin was equal at the time points of third-stage larvae, fourth-stage larvae, and adults of the parasite life cycle. The recombinant AcCystatin (rAcCystatin) expressed and purified from Escherichia coli has been demonstrated to possess an obvious inhibitory activity against cathepsin B and could significantly upregulate nitric oxide production from IFN-gamma activated RAW 264.7 macrophages. Sera from mice (non-permissive host) infected with A. cantonensis detected rAcCystatin by Western blot, while the sera from infected rats (permissive host) could not. The results implied that AcCystatin might be an immunoregulator in A. cantonensis infection.

Cytokine expression in dogs with natural Leishmania infantum infection

The aim of this study was to evaluate cytokine expression in 22 Leishmania infantum naturally infected dogs, in order to correlate this parameter with the clinical status of infected animals. After 4 and 8 months from the first diagnosis of Leishmania infection, clinical and laboratory examination of dogs was performed and peripheral blood mononuclear cells (PBMC) were isolated. The cytokine profile was analysed in terms of IFN-gamma, IL-4, IL-10 and TNF-alpha mRNA expression in cultured PBMC by a semi-quantitative reverse transcriptase-PCR. Thirteen out of 22 Leishmania-infected dogs remained asymptomatic in the follow-up, while 9 showed clinical signs of leishmaniasis. IL-4, IL-10, TNF-alpha and IFN-gamma mRNA levels were not significantly different in asymptomatic compared to symptomatic animals 4 months from the diagnosis of Leishmania infection, but were significantly higher in symptomatic versus asymptomatic dogs after 8 months from diagnosis. In addition, IL-4, IL-10 and TNF-alpha mRNA levels significantly increased only in symptomatic dogs at 8 months, in comparison to the levels found at 4 months. These results show a mixed Th1 and Th2 cytokine response in Leishmania-infected dogs, with higher cytokine expression in dogs with manifest clinical disease, during the second follow-up after 8 months from the first diagnosis of infection.

ERB-041, a selective ER beta agonist, inhibits iNOS production in LPS-activated peritoneal macrophages of endometriosis via suppression of NF-kappaB activation

OBJECTIVE

The aim of the present study was to assess the anti-inflammatory effects of selective ER beta (ER beta) agonist on lipopolysaccharide (LPS)-induced inducible nitric oxide synthase (iNOS) production in peritoneal macrophages (PMs) of endometriosis (EMS).

METHODS

ER alpha (ER alpha) and ER beta expressions in PMs were analyzed by RT-PCR and immunoblot. The PMs of endometriosis were exposed to increasing concentrations of ER beta agonist ERB-041 over a period from 0.5 to 8h before stimulation with LPS and the levels of iNOS protein were evaluated by immunoblot. Subsequently, the PMs were pretreated with vehicle, ERB-041 or ER alpha agonist PPT before exposing to LPS. iNOS expression, p65 protein and active extracellular signal-regulated kinases (ERKs) level accumulated in the nuclear were detected by immunoblot. For experiment investigating the role of ERKs in LPS-induced iNOS expression, the PMs were pretreated with U0126, a specific ERK inhibitor, for 60 min before LPS treatment and iNOS expression was detected by immunoblot.

RESULTS

The PMs of EMS expressed ER beta to a greater extent compared with normal women. Pretreatment the PMs with ERB-041 resulted in a significant inhibition of LPS-induced iNOS expression and NF-kappaB activation by preventing its nuclear translocation. The ERKs pathway was involved in the LPS-induced iNOS production and was not repressed by the activation of ERs.

CONCLUSION

The inhibitory effect of ER beta agonist on LPS-induced iNOS production in PMs of EMS is likely mediated via repressing of nuclear factor-kappa B (NF-kappaB) but not ERKs signaling pathways.