Pro- and anti-inflammatory cytokines in cutaneous leishmaniasis: a review

A conserved Leishmania hypothetical protein evaluated for the serodiagnosis of canine and human visceral and tegumentary leishmaniasis, as well as a serological marker for the posttreatment patient follow-up

In the present study, a conserved Leishmania hypothetical protein, LiHyE, was evaluated for the serodiagnosis of leishmaniasis. Results showed that it presented high sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) to serologically identify visceral leishmaniasis (VL) dogs when 40 positive sera and 95 cross-reactive samples were used. rLiHyE also showed the best results of sensitivity, specificity, PPV, and NPV to identify tegumentary leishmaniasis (TL) and VL patients when 45 leishmaniasis patients' sera and 90 cross-reactive samples were used. Results were better in comparison to those obtained when rA2 or Leishmania antigenic extract was employed as controls. The posttreatment follow-up showed that rLiHyE-specific antibodies declined significantly after the end of treatments, and a predominance of the IgG2 subclass was found in comparison to IgG1 levels in both TL and VL patients. In conclusion, rLiHyE can be considered a candidate for the serodiagnosis of canine and human leishmaniasis.

Vaccine candidates against leishmania under current research

INTRODUCTION

The search for vaccines to prevent human leishmaniasis is an active field of investigation aimed to prevent the devastating effects of this family of diseases on human health. The design and commercialization of several vaccines against canine leishmaniasis is a hopeful advance toward the achievement of a human vaccine.

AREAS COVERED

This review includes a summary of the most relevant immunological aspects accompanying leishmaniasis in natural hosts as well as a description of the latest advances in the multiple strategies that are being followed to develop leishmanial prophylactic vaccines. We have combined citations of the latest specialized reviews with research articles presenting the most recent results.

EXPERT COMMENTARY

Achieving safe, effective, durable and low-cost prophylactic vaccines against leishmaniasis is still a major challenge. These vaccines should control not only parasite progression, but also the accompanying pathology, which results from an imbalanced interaction between the infectious agent and the human host immune system. Different strategies for development of vaccines are currently under investigation. They range from the use of live non-pathogenic vectors to the employment of subunit vaccines combined with adjuvants and/or delivery systems inducing cell-mediated immunity.

Oral Immunization against PEDV with Recombinant Lactobacillus casei Expressing Dendritic Cell-Targeting Peptide Fusing COE Protein of PEDV in Piglets

Porcine epidemic diarrhea (PED) is a highly contagious disease in newborn piglets. In our previous study, a genetically engineered Lactobacillus casei oral vaccine (pPG-COE-DCpep/L393) expressing a dendritic cell (DC)-targeting peptide fused with porcine epidemic diarrhea virus (PEDV) COE antigen was developed. This vaccine induced significant levels of anti-PEDV specific IgG and IgA antibody responses in mice, indicating a potential strategy against PEDV infection. In this study, pPG-COE-DCpep/L393 was used for oral vaccination of newborn piglets against PEDV. We then assessed the immune responses and protection efficacy of pPG-COE-DCpep/L393. An indirect enzyme-linked immunosorbent assay (ELISA) showed that the recombinant Lactobacillus vaccine elicits a specific systemic and mucosal immune response. The T-helper cells mediated by pPG-COE-DCpep/L393 and PEDV infection display a Th1 phenotype. The histopathological results showed that pPG-COE-DCpep/L393 promotes lymphocyte proliferation and effectively protects piglets against PEDV infection. The transforming growth factor-β level indicated that the recombinant Lactobacillus vaccine plays a role in anti-inflammatory responses in mesenteric lymph nodes during PEDV infection. These results show that pPG-COE-DCpep/L393 is a potential vaccine against PEDV infection.

High levels of extracellular ATP lead to chronic inflammatory response in melanoma patients

Skin cancer represents a serious public health problem and melanoma is considered the most significant due to its high metastasis capacity. Evasion mechanisms are the main characteristic of these tumor cells to escape of immune response. Extracellular nucleotides and nucleosides play an important role in inflammatory and immune responses. In this study, we analyzed the expression and activity of purinergic system enzymes in platelets and lymphocytes, ATP levels quantification, as well the level of pro and anti-inflammatory interleukins in the serum of 23 patients with surgical melanoma removal (CM group) and 23 control subjects (CT group). Results showed a decrease in ATP, ADP, and AMP hydrolysis and an increase in ATP levels quantification in CM group. The pro-inflammatory cytokines were elevated in CM group when compared to CT group. These results suggest an inflammatory process, even after surgical removal, due to elevated extracellular ATP levels. Besides, CM group displayed an increase in IL-10 levels and an increased in ADA activity in platelets and lymphocytes. Once adenosine and IL-10 are anti-inflammatory molecules, these results indicate a down-regulation of immune system front to malignant process. The alteration in nucleotide and nucleoside hydrolysis reinforces the purinergic systems role in this cancer. Therefore, even after surgical removal, the purinergic system can develop a chronic inflammatory micro-environment that can influence directly on relapse or metastasis.

Immunization with LJM11 salivary protein protects against infection with Leishmania braziliensis in the presence of Lutzomyia longipalpis saliva

Leishmania is transmitted in the presence of sand fly saliva. Protective immunity generated by saliva has encouraged identification of a vector salivary-based vaccine. Previous studies have shown that immunization with LJM11, a salivary protein from Lutzomyia longipalpis, is able to induce a Th1 immune response and protect mice against bites of Leishmania major-infected Lutzomyia longipalpis. Here, we further investigate if immunization with LJM11 recombinant protein is able to confer cross-protection against infection with Leishmania braziliensis associated with salivary gland sonicate (SGS) from Lutzomyia intermedia or Lu. longipalpis. Mice immunized with LJM11 protein exhibited an increased production of anti-LJM11 IgG, IgG1 and IgG2a and a DTH response characterized by an inflammatory infiltrate with the presence of CD4⁺ IFN-γ⁺ T cells. LJM11-immunized mice were intradermally infected in the ear with L. braziliensis in the presence of Lu. longipalpis or Lu. intermedia SGS. A significant reduction of parasite numbers in the ear and lymph node in the group challenged with L. braziliensis plus Lu. longipalpis SGS was observed, but not when the challenge was performed with L. braziliensis plus Lu. intermedia SGS. A higher specific production of IFN-γ and absence of IL-10 by lymph node cells were only observed in LJM11 immunized mice after infection. After two weeks, a similar frequency of CD4⁺ IFN-γ⁺ T cells was detected in LJM11 and BSA groups challenged with L. braziliensis plus Lu. longipalpis SGS, suggesting that early events possibly triggered by immunization are essential for protection against Leishmania infection. Our findings support the specificity of saliva-mediated immune responses and reinforce the importance of identifying cross-protective salivary antigens.

Leishmania-Derived Trimannose Modulates the Inflammatory Response To Significantly Reduce Leishmania major-Induced Lesions

Leishmania lipophosphoglycan (LPG) is a key virulence factor, initiating inflammation resulting in cutaneous lesions. LPG is capped by various oligosaccharides. How these glycans are recognized and how they alter the course of Leishmania infection are poorly understood. Previous studies synthesized α-1,2-trimannose cap sugars on latex beads and demonstrated that C57BL/6 mice coinoculated with Leishmania major and trimannose-coated beads produced significantly higher levels of interleukin-12p40 (IL-12p40) and other proinflammatory, type 1 cytokines than mice inoculated with L. major alone within the first 48 h of infection. However, as L. major infection typically progress over weeks to months, the role of trimannose in altering disease progression over the course of infection was unknown. Wild-type mice were inoculated with either trimannose-coated or carrier (uncoated) beads, infected with L. major alone, coinoculated with carrier beads and L. major, or coinoculated with trimannose-coated beads and L. major Trimannose treatment of L. major-infected mice decreased the parasite load and significantly decreased the lesion size at 14 days postinfection (p.i.) compared to results for nontreated, infected mice. Infected, trimannose-treated mice had decreased IL-12p40 and IL-10 secretion and increased interferon gamma secretion at 14 days p.i. Mannose receptor knockout (MR^-/-) mice lack the ability to detect trimannose. When MR^-/- mice were infected with L. major and treated with trimannose beads, they did not have decreased lesion size. Leishmania-derived trimannose represents a novel immunomodulator that provides early type 1-skewed cytokine production to control the parasite load and alter the course of cutaneous leishmaniasis.

Leishmania infantum lipophosphoglycan induced-Prostaglandin E2 production in association with PPAR-γ expression via activation of Toll like receptors-1 and 2

Lipophosphoglycan (LPG) is a key virulence factor expressed on the surfaces of Leishmania promastigotes. Although LPG is known to activate macrophages, the underlying mechanisms resulting in the production of prostaglandin E₂ (PGE₂) via signaling pathways remain unknown. Here, the inflammatory response arising from stimulation by Leishmania infantum LPG and/or its lipid and glycan motifs was evaluated with regard to PGE₂ induction. Intact LPG, but not its glycan and lipid moieties, induced a range of proinflammatory responses, including PGE₂ and nitric oxide (NO) release, increased lipid droplet formation, and iNOS and COX2 expression. LPG also induced ERK-1/2 and JNK phosphorylation in macrophages, in addition to the release of PGE₂, MCP-1, IL-6, TNF-α and IL-12p70, but not IL-10. Pharmacological inhibition of ERK1/2 and PKC affected PGE₂ and cytokine production. Moreover, treatment with rosiglitazone, an agonist of peroxisome proliferator-activated receptor gamma (PPAR-γ), also modulated the release of PGE₂ and other proinflammatory mediators. Finally, we determined that LPG-induced PPAR-γ signaling occurred via TLR1/2. Taken together, these results reinforce the role played by L. infantum-derived LPG in the proinflammatory response seen in Leishmania infection.

Effects of Bone Marrow Mesenchymal Stromal Cell Therapy in Experimental Cutaneous Leishmaniasis in BALB/c Mice Induced by Leishmania amazonensis

Cutaneous leishmaniasis remains both a public health and a therapeutic challenge. To date, no ideal therapy for cutaneous leishmaniasis has been identified, and no universally accepted therapeutic regimen and approved vaccines are available. Due to the mesenchymal stromal cell (MSC) immunomodulatory capacity, they have been applied in a wide variety of disorders, including infectious, inflammatory, and allergic diseases. We evaluated the potential effects of bone marrow MSC therapy in a murine model of cutaneous leishmaniasis. In vitro, coculture of infected macrophages with MSC increased parasite load on macrophages in comparison with controls (macrophages without MSCs). In vivo, BALB/c mice were infected with 2 × 10⁶Leishmania amazonensis (Josefa strain) promastigotes in the footpad. 7 and 37 days after infection, animals were treated with 1 × 10⁵ MSCs, either intralesional (i.l.), i.e., in the same site of infection, or intravenously (i.v.), through the external jugular vein. Control animals received the same volume (50 µL) of phosphate-buffered saline by i.l. or i.v. routes. The lesion progression was assessed by its thickness measured by pachymetry. Forty-two days after infection, animals were euthanized and parasite burden in the footpad and in the draining lymph nodes was quantified by the limiting dilution assay (LDA), and spleen cells were phenotyped by flow cytometry. No significant difference was observed in lesion progression, regardless of the MSC route of administration. However, animals treated with i.v. MSCs presented a significant increase in parasite load in comparison with controls. On the other hand, no harmful effect due to MSCs i.l. administered was observed. The spleen cellular profile analysis showed an increase of IL-10 producing T CD4⁺ and TCD8⁺ cells in the spleen only in mice treated with i.v. MSC. The excessive production of IL-10 could be associated with the disease-aggravating effects of MSC therapy when intravenously administered. As a conclusion, in the current murine model of L. amazonensis-induced cutaneous disease, MSCs did not control the damage of cutaneous disease and, depending on the administration route, it could result in deleterious effects.

Immunopathological characterization of human cutaneous leishmaniasis lesions caused by Leishmania (Viannia) spp. in Amazonian Brazil

American cutaneous leishmaniasis (ACL) is a chronic infectious disease caused by different protozoan species of Leishmania, and it is endemic in both tropical and subtropical countries. Using immunohistochemistry, we investigate the density of CD68⁺, lysozyme⁺, CD1a⁺, factor XIIIa⁺, CD4⁺, CD8⁺, CD56⁺, interferon (IFN)-γ⁺, and inducible NO synthase (iNOS⁺) cells. These cells were analyzed from 22 biopsy samples obtained from the lesions of ACL patients, whose infection was caused by Leishmania (Viannia) spp. Histopathological analysis showed dense mononuclear inflammatory infiltration in the dermis, which was composed of lymphocytes, macrophages, plasma cells, and discrete tissue parasitism. Granulomatous reactions were also present in the majority of cases. The density of the activated macrophages was higher than that of inactivated macrophages in the lesions. The density of Langerhans cells (CD1a⁺) was lower than that of dermal dendrocytes (factor XIIIa⁺). The density of CD8⁺ T lymphocytes was higher than that of CD4⁺ T lymphocytes. The cellular density of these immunological markers in relation to the species of Leishmania demonstrated that L. (Viannia) sp. lesions had higher IFN-γ expression than that Leishmania (Viania) braziliensis lesions. The evaluation of these markers, according to disease progression, did not reveal any significant differences. L. (Viannia) sp. infection leads to a favorable immune response in the host, as predominantly represented by lysozyme⁺, factor XIIIa⁺, CD8⁺ T cells, and the expression of (IFN)-γ⁺ at the lesion site.