Regulatory effect of PGE2 on microbicidal activity and inflammatory cytokines in canine leishmaniasis.

Canine leishmaniasis (CanL) is caused by the intracellular parasite Leishmania infantum. Prostaglandin E2 (PGE2 ) exerts potent regulatory effects on the immune system in experimental model Leishmania infection, but this influence has not yet been studied in CanL. In this study, PGE2 and PGE2 receptor levels and the regulatory effect of PGE2 on arginase activity, NO2 , IL-10, IL-17, IFN-γ, TNF-α and parasite load were evaluated in cultures of splenic leucocytes obtained from dogs with CanL in the presence of agonists and inhibitors. Our results showed that splenic leucocytes from dogs with CanL had lower EP2 receptor levels than those of splenic leucocytes from healthy animals. We observed that NO2 levels decreased when the cells were treated with a PGE2 receptor agonist (EP1/EP2/EP3) or COX-2 inhibitor (NS-398) and that TNF-α, IL-17 and IFN-γ cytokine levels decreased when the cells were treated with a PGE2 receptor agonist (EP2) or PGE2 itself. The parasite load in splenic leucocyte cell cultures from dogs with CanL decreased after stimulation of the cells with PGE2 . We conclude that Leishmania infection of dogs modulates PGE2 receptors and speculate that the binding of PGE2 to its receptors may activate the microbicidal capacity of cells.

Plasmonic rK28 ELISA improves the diagnosis of canine Leishmania infection.

In this study, we evaluated the performance of a new enzyme-linked immunosorbent assay (ELISA) variant known as indirect "plasmonic ELISA" (pELISA) for the detection of Leishmania spp. infection. Serum samples from 170 dogs from an area where canine leishmaniosis (CanL) is endemic and from 26 healthy dogs from a nonendemic area were tested by indirect pELISA, and the results were compared to those of an indirect ELISA (both with recombinant antigen rK28) and those of an immunochromatographic test (dual-path platform, TR-DPP®) using real-time PCR on blood samples or conjunctival swabs as the gold standard. The pELISA, indirect rK28 ELISA and the TR-DPP® immunochromatographic test presented sensitivities of 94.7%, 89.5% and 79.0% and specificities of 100%, 92.7% and 91.5%, respectively. The analysis of the results revealed that the specificity of the indirect pELISA was greater than that of the method recommended by the Ministry of Health in Brazil and may increase the feasibility of diagnosis in resource-constrained countries because it does not require sophisticated instruments to read. Thus, this method can be used as an additional tool for the detection of Leishmania spp. infection in these areas.

MicroRNA-21 and microRNA-148a affects PTEN, NO and ROS in canine leishmaniasis.

Canine Visceral leishmaniasis (CanL) poses a severe public health threat in several countries. Disease progression depends on the degree of immune response suppression. MicroRNAs (miRs) modulate mRNA translation into proteins and regulate various cellular functions and pathways associated with immune responses. MiR-21 and miR-148a can alter the parasite load and M1 macrophages are the principal cells in dogs' leishmanicidal activity. A previous study found increased miR-21 and miR-148a in splenic leukocytes (SL) of dogs with CanL using microarray analysis and in silico analysis identified PTEN pathway targets. PTEN is involved in the immune regulation of macrophages. We measured PTEN and the production of reactive oxygen species (ROS) and nitric oxide (NO) before and after transfection SLs of dogs with CanL with mimic and inhibition of miR-21 and miR-148a. PTEN levels increased, NO and ROS decreased in SLs from dogs with CanL. Inhibition of miRNA-21 resulted in PTEN increase; in contrast, PTEN decreased after miR-148a inhibition. Nitrite (NO2) levels increased after transfection with miR-21 inhibitor but were decreased with miR-148a inhibitor. The increase in miR-21 promoted a reduction in ROS and NO levels, but miR-148a inhibition increased NO and reduced ROS. These findings suggest that miR-21 and miR-148a can participate in immune response in CanL, affecting PTEN, NO, and ROS levels.

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-1ß, 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-1ß 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.

miRNA-21 regulates CD69 and IL-10 expression in canine leishmaniasis.

Visceral leishmaniasis in humans is a chronic and fatal disease if left untreated. Canine leishmaniasis (CanL) is a severe public health problem because infected animals are powerful transmitters of the parasite to humans via phlebotomine vectors. Therefore, dogs are an essential target for control measures. Progression of canine infection is accompanied by failure of cellular immunity with reduction of circulating lymphocytes and increased cytokines that suppress macrophage function. Studies showed that the regulation of the effector function of macrophages and T cells appears to depend on miRNAs; miRNA-21 (miR-21) shows increased expression in splenic leukocytes of dogs with CanL and targets genes related to the immune response. Mimics and inhibitors of miR-21 were used in vitro to transfect splenic leukocytes from dogs with CanL. After transfection, expression levels of the proteins FAS, FASL, CD69, CCR7, TNF-α, IL-17, IFN-γ, and IL-10 were measured. FAS, FASL, CD69, and CCR7 expression levels decreased in splenic leukocytes from dogs with CanL. The miR-21 mimic decreased CD69 expression in splenic leukocytes from CanL and healthy groups. The miR-21 inhibitor decreased IL-10 levels in culture supernatants from splenic leukocytes in the CanL group. These findings suggest that miR-21 alters the immune response in CanL; therefore, miR-21 could be used as a possible therapeutic target for CanL.

Differential expression of miRNAs in canine peripheral blood mononuclear cells (PBMC) exposed to Leishmania infantum in vitro.

Visceral Leishmaniasis (VL) is a neglected tropical disease, caused by L. infantum in the New World, where dogs are the main reservoir. These parasites can regulate host immune response through miRNA differential expression in the early stages of infection; however such early response has not yet been investigated in the canine model. PBMC from healthy dogs were exposed to L. infantum in vitro and microarray analysis showed an upregulation of miR-206, miR-302d, miR-433, miR-214, miR-493, miR-514, miR-1835, miR-210, miR-539, miR-432, miR-188, miR-345 and downregulation of miR-489 and miR-503 in comparison to non-exposed control cells, at 24 h post-exposure. In silico target prediction showed that the upregulated miRNAs target 1541 genes, which can modulate important pathways involved in the early immune responses, like the "MAPK signaling pathway", one of the most relevant pathways to Leishmania survival inside host cells. These findings shed light on parasite modulation of host immunity following Leishmania infection, which in turn can be explored for drug development.

Combined in vitro IL-12 and IL-15 stimulation promotes cellular immune response in dogs with visceral leishmaniasis.

Domestic dogs are the main reservoir of Leishmania infantum, a causative agent of visceral leishmaniasis (VL). The number of human disease cases is associated with the rate of canine infection. Currently available drugs are not efficient at treating canine leishmaniasis (CanL) and months after the treatment most dogs show disease relapse, therefore the development of new drugs or new therapeutic strategies should be sought. In CanL, dogs lack the ability to mount a specific cellular immune response suitable for combating the parasite and manipulation of cytokine signaling pathway has the potential to form part of effective immunotherapeutic methods. In this study, recombinant canine cytokines (rcaIL-12, rcaIL-2, rcaIL-15 and rcaIL-7) and soluble receptor IL-10R1 (rcasIL-10R1), with antagonistic activity, were evaluated for the first time in combination (rcaIL-12/rcaIL-2, rcaIL-12/rcaIL-15, rcaIL-12/rcasIL-10R1, rcaIL-15/rcaIL-7) or alone (rcasIL-10R1) to evaluate their immunomodulatory capacity in peripheral blood mononuclear cells (PBMCs) from dogs with leishmaniasis. All the combinations of recombinant proteins tested were shown to improve lymphoproliferative response. Further, the combinations rcaIL-12/rcaIL-2 and rcaIL-12/rcaIL-15 promoted a decrease in programmed cell death protein 1 (PD-1) expression in lymphocytes. These same combinations of cytokines and rcaIL-12/rcasIL-10R1 induced IFN-γ and TNF-α production in PBMCs. Furthermore, the combination IL-12/IL-15 led to an increased in T-bet expression in lymphocytes. These findings are encouraging and indicate the use of rcaIL-12 and rcaIL-15 in future in vivo studies aimed at achieving polarization of cellular immune responses in dogs with leishmaniasis, which may contribute to the development of an effective treatment against CanL.

PD-1 regulates leishmanicidal activity and IL-17 in dogs with leishmaniasis.

Leishmaniasis is an immunosuppressive disease caused by protozoa of the genus Leishmania, for which dogs are the domestic reservoir. The programmed cell death-1 molecule (PD-1) is highly expressed in leukocyte cells of dogs with leishmaniasis, and it promotes T lymphocyte exhaustion and suppression of cytokine secretion. Because PD-1 has a suppressive function regarding cell immunity, we evaluated the effect of PD-1 blocking antibodies on NO, ROS and interleukin 17 (IL-17) production and on parasite load in spleen leukocyte cultures from dogs with leishmaniasis. In vitro, PD-1 blocking promoted increased levels of intracellular NO and NO2 and reduced the levels of IL-17 in the culture supernatant, in addition to reducing the parasite load, but it did not change ROS levels. We conclude that PD-1 participates in the regulation of the immune response and that the blocking antibody is effective in restoring host microbicidal activity. This can be investigated in an immunotherapeutic study in the future.

Induction of miR 21 impairs the anti-Leishmania response through inhibition of IL-12 in canine splenic leukocytes.

Visceral Leishmaniasis is a chronic zoonosis and, if left untreated, can be fatal. Infected dogs have decreased cellular immunity (Th1) and develop a potent humoral response (Th2), which is not effective for elimination of the protozoan. Immune response can be modulated by microRNAs (miRNAs), however, characterization of miRNAs and their possible regulatory role in the spleen of infected dogs have not been done. We evaluated miRNA expression in splenic leukocytes (SL) from dogs naturally infected with Leishmania infantum and developing leishmaniasis (CanL; n = 8) compared to healthy dogs (n = 4). Microarray analysis showed increased expression of miR 21, miR 148a, miR 7 and miR 615, and downregulation of miR 150, miR 125a and miR 125b. Real-time PCR validated the differential expression of miR 21, miR 148a and miR 615. Further, decrease of miR 21 in SL, by means of transfection with a miR 21 inhibitor, increased the IL-12 cytokine and the T-bet/GATA-3 ratio, and decreased parasite load on SL of dogs with CanL. Taken together, these findings suggest that L. infantum infection alters splenic expression of miRNAs and that miR 21 interferes in the cellular immune response of L. infantum-infected dogs, placing this miRNA as a possible therapeutic target in CanL.

Development of plasmonic ELISA for the detection of anti-Leishmania sp. IgG antibodies.

Recently, a novel Enzyme-Linked Immunosorbent Assay (ELISA) strategy has emerged, known as "plasmonic ELISA" (pELISA), which enables the detection of disease biomarkers at low concentrations with the naked eye. For the first time, this research has developed a signal-generation mechanism for the detection of anti-Leishmania sp. IgG antibodies with the naked eye using pELISA. The immunoassay incorporates an indirect ELISA with successive growth of gold nanoparticles to obtain blue or red-colored solutions in the presence or absence of anti-Leishmania sp. IgG antibodies in canine serum, respectively. The technique we developed was successfully tested in canine serum positive and negative for canine leishmaniasis (CanL), and was shown to be an effective method that could be used as an additional tool for CanL diagnosis. It will be particularly useful in resource-constrained countries, because it does not require sophisticated instruments to read the results, increasing the practicality of CanL detection in these areas.

Characterization of the microtranscriptome of macrophages infected with virulent, attenuated and saprophyte strains of Leptospira spp.

Leptospirosis is a bacterial zoonosis, caused by Leptospira spp., that leads to significant morbidity and mortality worldwide. Despite considerable advances, much is yet to be discovered about disease pathogenicity. The influence of epigenetic mechanisms, particularly RNA-mediated post-transcriptional regulation of host immune response has been described following a variety of bacterial infections. The current study examined the microtranscriptome of macrophages J774A.1 following an 8h infection with virulent, attenuated and saprophyte strains of Leptospira. Microarray analysis revealed that 29 miRNAs were misregulated following leptospiral infection compared to control macrophages in a strain and virulence-specific manner. Pathway analysis for targets of these differentially expressed miRNAs suggests that several processes involved in immune response could be regulated by miRNAs. Our data provides the first evidence that host miRNAs are regulated by Leptospira infection in macrophages. A number of the identified miRNA targets participate in key immune response processes. We suggest that post-transcriptional regulation by miRNAs may play a role in host response to infection in leptospirosis.

Relationship of peripheral blood mononuclear cells miRNA expression and parasitic load in canine visceral leishmaniasis.

Visceral leishmaniasis (VL) in humans is a chronic and often fatal disease if left untreated. Dogs appear to be the main reservoir host for L. infantum infection, however, in many regions other canids such as jackals, foxes, wolves and other mammals, such as hares or black rats, have been implicated as wild reservoirs. Most dogs cannot form an effective immune response against this infection, and this could be modulated by small non-coding RNAs, called microRNAs, responsible for post-transcriptional control of gene expression. Here, we evaluated the expression of miRNAs in peripheral blood mononuclear cells (PBMC) of symptomatic dogs naturally infected with Leishmania (L.) infantum (n = 10) and compared to those of healthy dogs (n = 5). Microarray analysis revealed that miR-21, miR-424, miR-194 and miR-451 had a 3-fold increase in expression, miR-192, miR-503, and miR-371 had a 2-fold increase in expression, whereas a 2-fold reduction in expression was observed for miR-150 and miR-574. Real-time PCR validated the differential expression of miR-21, miR-150, miR-451, miR-192, miR-194, and miR-371. Parasite load of PBMC was measured by real-time PCR and correlated to the differentially expressed miRNAs, showing a strong positive correlation with expression of miR-194, a regular positive correlation with miR-371 expression, and a moderate negative correlation with miR-150 expression in PBMC. These findings suggest that Leishmania infection interferes with miRNAs expression in PBMC, and their correlation with parasite load may help in the identification of therapeutic targets in Canine Visceral Leishmaniasis (CVL).

Transcriptome datasets of macrophages infected with different strains of Leptospira spp.

The datasets reported herein provide information about microarray experiment of macrophage cell line J774A.1 infected with three different strains of Leptospira spp. Transcriptomic profiles were generated using Affymetrix® Mouse Gene 2.1 ST Array Strip. Data was normalized and statically process, p-value < 0.01, FDR < 0.05 and log2 fold change (± 2). The microarray raw data are available in Gene Expression Omnibus (GEO) under accession number GSE105141.

Data on differentially expressed miRNAs in dogs infected with Leishmania infantum.

This paper contains data on differentially expressed miRNAs in peripheral blood mononuclear cells (PBMC) of dogs naturally infected by Leishmania (L.) infantum compared to healthy dogs. In recent years, studies with miRNAs have shown that these molecules play a critical role in the regulation and function of immune response.Differentially expressed miRNAs were identified by microarray, validated by real time PCR and compared with parasite load in the dogs. Targets and pathways were analyzed using the Ingenuity Pathway Analysis program.