Enhanced expression of Toll-like receptors 2 and 4, but not 9, in spleen tissue from patients with visceral leishmaniasis

Immunoinformatics-based multi-epitope containing fused polypeptide vaccine design against visceral leishmaniasis with high immunogenicity and TLR binding

Visceral leishmaniasis (VL) is the most lethal among all leishmaniasis diseases and remains categorized as a neglected tropical disease (NTD). This study aimed to develop a peptide-based multi-epitope vaccine construct against VL using immunoinformatics methodologies. To achieve this, four distinct proteins were screened to identify peptides consisting of 9-15 amino acids with high binding affinity to toll-like receptors (TLRs), strong antigenicity, low allergenicity, and minimal toxicity. The resulting multi-epitope vaccine construct was fused in a tandem arrangement with appropriate linker peptides and exhibited superior properties related to cytotoxic T lymphocytes (CTLs), helper T lymphocytes (HTLs), and B-cell epitopes. Subsequently, a three-dimensional (3D) model of the vaccine construct was generated, refined, and validated for structural stability and immune response capabilities. Molecular docking and simulations confirmed the vaccine construct's stability and binding affinities with TLRs, with TLR4 displaying the highest binding affinity, followed by TLR2 and TLR3. Additionally, simulations predicted robust cellular and humoral antibody-mediated immune responses elicited by the designed vaccine construct. Notably, this vaccine construct includes proteins from various pathways of Leishmania donovani (LD), which have not been previously utilized in VL vaccine design. Thus, this study opens new avenues for the development of vaccines against diverse protozoan diseases.

Toll-like Receptor-9 (TLR-9) Signaling Is Crucial for Inducing Protective Immunity following Immunization with Genetically Modified Live Attenuated Leishmania Parasites

No human vaccine is available for visceral leishmaniasis (VL). Live attenuated centrin gene-deleted L. donovani (LdCen−/−) parasite vaccine has been shown to induce robust innate immunity and provide protection in animal models. Toll-like receptors (TLRs) are expressed in innate immune cells and are essential for the early stages of Leishmania infection. Among TLRs, TLR-9 signaling has been reported to induce host protection during Leishmania infection. Importantly, TLR-9 ligands have been used as immune enhancers for non-live vaccination strategies against leishmaniasis. However, the function of TLR-9 in the generation of a protective immune response in live attenuated Leishmania vaccines remains unknown. In this study, we investigated the function of TLR-9 during LdCen−/− infection and found that it increased the expression of TLR-9 on DCs and macrophages from ear-draining lymph nodes and spleen. The increase in TLR-9 expression resulted in changes in downstream signaling in DCs mediated through signaling protein myeloid differentiation primary response 88 (MyD88), resulting in activation and nuclear translocation of nuclear factor-κB (NF-κB). This process resulted in an increase in the DC’s proinflammatory response, activation, and DC-mediated CD4+T cell proliferation. Further, LdCen−/− immunization in TLR-9−/− mice resulted in a significant loss of protective immunity. Thus, LdCen−/− vaccine naturally activates the TLR-9 signaling pathway to elicit protective immunity against virulent L. donovani challenge.

Neutrophils and Visceral Leishmaniasis: Impact on innate immune response and cross-talks with macrophages and dendritic cells

Neutrophils with their array of microbicidal activities are the first innate immune cells to guard against infection. They are also most crucial for the host's initial defense against Leishmania parasites which cause clinically diverse diseases ranging from self-healing cutaneous leishmaniasis (CL) to a more severe visceral form, visceral leishmaniasis (VL). Neutrophils are recruited in large numbers at the infection site after bite of sandfly, which is the vector for the disease. The initial interaction of neutrophils with the parasites may modulate the subsequent innate and adaptive immune responses and hence affect the disease outcome. The purpose of this review is to comprehensively appraise the role of neutrophils during the early stages of Leishmania infection with a focus on the visceral form of the disease. In the past decade, new insights regarding the role of neutrophils in VL have surfaced which have been extensively elaborated in the present review. In addition, since much of the information regarding neutrophil-Leishmania early interaction has accumulated through studies on mouse models of CL, these studies are also revisited. We begin by reviewing the factors which drive the recruitment of neutrophils at the site of injection by the sandfly. We then discuss the studies delineating the molecular mechanisms involved in the uptake of the Leishmania parasite by neutrophils and how the parasite subverts their microbicidal functions. In the end, the interaction of infected neutrophils with macrophages and dendritic cells is summarized.

Tissue-specific transcriptomic changes associated with AmBisome® treatment of BALB/c mice with experimental visceral leishmaniasis

Background: Liposomal amphotericin B (AmBisome®) as a treatment modality for visceral leishmaniasis (VL) has had significant impact on patient care in some but not all regions where VL is endemic.  As the mode of action of AmBisome® in vivo is poorly understood, we compared the tissue-specific transcriptome in drug-treated vs untreated mice with experimental VL.    Methods:  BALB/c mice infected with L. donovani were treated with 8mg/kg AmBisome®, resulting in parasite elimination from liver and spleen over a 7-day period. At day 1 and day 7 post treatment (R x+1 and R x+7), transcriptomic profiling was performed on spleen and liver tissue from treated and untreated mice and uninfected mice.  BALB/c mice infected with M. bovis BCG (an organism resistant to amphotericin B) were analysed to distinguish between direct effects of AmBisome® and those secondary to parasite death.   Results: AmBisome® treatment lead to rapid parasitological clearance.  At R x+1, spleen and liver displayed only 46 and 88 differentially expressed (DE) genes (P<0.05; 2-fold change) respectively. In liver, significant enrichment was seen for pathways associated with TNF, fatty acids and sterol biosynthesis.  At R x+7, the number of DE genes was increased (spleen, 113; liver 400).  In spleen, these included many immune related genes known to be involved in anti-leishmanial immunity. In liver, changes in transcriptome were largely accounted for by loss of granulomas.   PCA analysis indicated that treatment only partially restored homeostasis.  Analysis of BCG-infected mice treated with AmBisome® revealed a pattern of immune modulation mainly targeting macrophage function.   Conclusions: Our data indicate that the tissue response to AmBisome® treatment varies between target organs and that full restoration of homeostasis is not achieved at parasitological cure.  The pathways required to restore homeostasis deserve fuller attention, to understand mechanisms associated with treatment failure and relapse and to promote more rapid restoration of immune competence.

Bioinformatics analysis of gene expression profile data to screen key genes involved in intracranial aneurysms

Intracranial aneurysm (IA) is a cerebrovascular disease with a high mortality rate. The pathogenesis of IA remains unclear and the treatment limited. The purpose of the present study was to identify the key genes expressed in IAs and provide the basis for further research and treatment. The raw dataset GSE75436 was downloaded from Gene Expression Omnibus, including 15 IA samples and 15 matched superficial temporal artery (STA) samples. Then, differentially expressed genes (DEGs) were identified using the limma package in R software. Hierarchical clustering analysis was performed on the DEGs using the gplot2 package in R. Database for Annotation, Visualization, and Integrated Discovery (DAVID) online tools were used to perform gene ontology (GO) functional enrichment analysis. DAVID and gene set enrichment analysis were separately used to perform the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. The intersections of the two results were selected as common KEGG pathways. Protein-protein interaction (PPI) analysis among the DEGs involved in the common KEGG pathways was performed using Search Tool for the Retrieval of Interacting Genes online tools, and visualized with Cytoscape software. A total of 782 DEGs were identified, comprising 392 upregulated and 390 downregulated DEGs. Hierarchical clustering demonstrated that the DEGs could precisely distinguish the IAs from the STAs. The GO enrichment analysis demonstrated that the upregulated DEGs were mainly involved in the inflammatory response and the management of extracellular matrix, and the downregulated DEGs were mainly involved in the process of vascular smooth muscle contraction. The KEGG pathway enrichment analysis demonstrated that the common pathways were ‘leishmaniasis’, ‘Toll-like receptor signaling pathway’ and ‘vascular smooth muscle contraction’. In the PPI network, tumor necrosis factor (TNF), interleukin 8 and Toll-like receptor 4 had the highest degrees; they were associated with the inflammatory response. The Toll-like receptor signaling pathway and TNF gene may serve as targets for future research and treatment.

Alternative to Chemotherapy-The Unmet Demand against Leishmaniasis

Leishmaniasis is a neglected protozoan disease that mainly affects the tropical as well as subtropical countries of the world. The primary option to control the disease still relies on chemotherapy. However, a hindrance to treatments owing to the emergence of drug-resistant parasites, enormous side effects of the drugs, their high cost, and requirement of long course hospitalization has added to the existing problems of leishmaniasis containment program. This review highlights the prospects of immunotherapy and/or immunochemotherapy to address the limitations for current treatment measures for leishmaniasis. In addition to the progress in alternate therapeutic strategies, the possibility and advances in developing preventive measures against the disease have been pointed. The review highlights our recent understandings of the protective immunology that can be exploited to develop an effective vaccine against leishmaniasis. Moreover, an update on the approaches that have evolved over the recent years are predominantly focused to overcome the current challenges in developing immunotherapeutic as well as prophylactic antileishmanial vaccines is discussed.

TLR-2 and TLR-4 transcriptions in unstimulated blood from dogs with leishmaniosis due to Leishmania infantum at the time of diagnosis and during follow-up treatment

Innate immunity, in particular, the role of toll-like receptors (TLRs), has not been extensively studied in canine L. infantum infection. The main aim of this study was to determine the transcription of TLR2 and TLR4 in the blood of dogs with natural clinical leishmaniosis at the time of diagnosis and during treatment follow-up and subsequently correlate these findings with clinical, serological and parasitological data. Forty-six Leishmania-seropositive sick dogs with a high antibody level at the time of diagnosis were studied and compared with 34 healthy seronegative dogs. Twenty-two of these sick dogs were treated with meglumine antimoniate and allopurinol and followed-up at 30, 180 and 365days following the start of treatment. Clinical status was defined by a thorough physical examination, complete blood count, biochemistry profile, electrophoresis of serum proteins, and urinary protein/creatinine ratio (UPC). EDTA blood was stored in RNAlater^® solution before RNA extraction and cDNA production were performed. TLR2, TLR4 and three reference genes (HPRT-1, CG14980 and SDHA) were studied in each blood sample by real time PCR. The relative quantification of TLR2 was higher (mean 3.5) in sick dogs when compared with seronegative healthy dogs (mean 1.3; P=0.0001) while the relative quantification of TLR4 was similar in both groups. In addition, the relative quantification of TLR2 significantly decreased during follow-up at all time points compared with day 0 whereas no changes were observed with TLR4 transcription. A significant positive correlation was noted between TLR2 and UPC, total protein, beta and gamma globulins, specific L. infantum antibodies and blood parasite load while a negative correlation was observed with albumin, albumin/globulin ratio, hematocrit and hemoglobin. TLR4 transcript did not correlate with any parameter. These findings indicate an up-regulation of TLR2 transcription in unstimulated blood in naturally infected sick dogs as compared to healthy dogs suggesting active innate immune and proinflammatory responses. In addition, TLR2 transcription is reduced with clinical improvement during treatment. In contrast, TLR4 transcription appears to be similar among groups at the time of diagnosis with no changes during treatment follow-up suggesting a less important role for this TLR in clinical canine leishmaniosis.

Possibilities and challenges for developing a successful vaccine for leishmaniasis

Leishmaniasis is a vector-borne disease caused by different species of protozoan parasites of the genus Leishmania. It is a major health problem yet neglected tropical diseases, with approximately 350 million people worldwide at risk and more than 1.5 million infections occurring each year. Leishmaniasis has different clinical manifestations, including visceral (VL or kala-azar), cutaneous (CL), mucocutaneous (MCL), diffuse cutaneous (DCL) and post kala-azar dermal leishmaniasis (PKDL). Currently, the only mean to treat and control leishmaniasis is by rational medications and vector control. However, the number of available drugs is limited and even these are either exorbitantly priced, have toxic side effects or prove ineffective due to the emergence of resistant strains. On the other hand, the vector control methods are not so efficient. Therefore, there is an urgent need for developing a safe, effective, and affordable vaccine for the prevention of leishmaniasis. Although in recent years a large body of researchers has concentrated their efforts on this issue, yet only three vaccine candidates have gone for clinical trial, until date. These are: (i) killed vaccine in Brazil for human immunotherapy; (ii) live attenuated vaccine for humans in Uzbekistan; and (iii) second-generation vaccine for dog prophylaxis in Brazil. Nevertheless, there are at least half a dozen vaccine candidates in the pipeline. One can expect that, in the near future, the understanding of the whole genome of Leishmania spp. will expand the vaccine discovery and strategies that may provide novel vaccines. The present review focuses on the development and the status of various vaccines and potential vaccine candidates against leishmaniasis.

Transcription of Toll-Like Receptors 2, 3, 4 and 9, FoxP3 and Th17 Cytokines in a Susceptible Experimental Model of Canine Leishmania infantum Infection

Canine leishmaniosis (CanL) due to Leishmania infantum is a chronic zoonotic systemic disease resulting from complex interactions between protozoa and the canine immune system. Toll-like receptors (TLRs) are essential components of the innate immune system and facilitate the early detection of many infections. However, the role of TLRs in CanL remains unknown and information describing TLR transcription during infection is extremely scarce. The aim of this research project was to investigate the impact of L. infantum infection on canine TLR transcription using a susceptible model. The objectives of this study were to evaluate transcription of TLRs 2, 3, 4 and 9 by means of quantitative reverse transcription polymerase chain reaction (qRT-PCR) in skin, spleen, lymph node and liver in the presence or absence of experimental L. infantum infection in Beagle dogs. These findings were compared with clinical and serological data, parasite densities in infected tissues and transcription of IL-17, IL-22 and FoxP3 in different tissues in non-infected dogs (n = 10), and at six months (n = 24) and 15 months (n = 7) post infection. Results revealed significant down regulation of transcription with disease progression in lymph node samples for TLR3, TLR4, TLR9, IL-17, IL-22 and FoxP3. In spleen samples, significant down regulation of transcription was seen in TLR4 and IL-22 when both infected groups were compared with controls. In liver samples, down regulation of transcription was evident with disease progression for IL-22. In the skin, upregulation was seen only for TLR9 and FoxP3 in the early stages of infection. Subtle changes or down regulation in TLR transcription, Th17 cytokines and FoxP3 are indicative of the silent establishment of infection that Leishmania is renowned for. These observations provide new insights about TLR transcription, Th17 cytokines and Foxp3 in the liver, spleen, lymph node and skin in CanL and highlight possible markers of disease susceptibility in this model.

Effects of CD14 and TLR4 on LPS-mediated normal human skin fibroblast proliferation

BACKGROUND

This study was designed to elucidate the effects of CD14 and TLR4 on the proliferation of LPS-mediated normal human skin fibroblasts and to gain new insights into the mechanisms underlying LPS-induced scar formation.

METHODS

Cell morphology and density were observed using an inverted microscope. Proliferation curves were described by MTT. The number of proliferating cells was counted by staining the cells with trypan blue. Cells were stained with propidium iodide (PI) and the phase of cell generation cycle was determined by flow cytometry.

RESULTS

The growth rate detected in groups B, C, D was slower compared to group A after 48 h. All proliferation curves were approximately S shaped and the peak was seen on days 6, followed by a sharp decline on days 7. The proliferation rate of groups B, C, D was significantly slower than group A. After the staining, we found a significantly smaller number of proliferating cells in groups B, C, D as compared to group A. Flow cytometry revealed that the ratio of proliferating cells at S phase was lower in the groups B, C, D as compared to group A.

CONCLUSIONS

Both separate and combined use of anti-CD14 and anti-TLR4 enable a significant decline in the rate and capacity of proliferation, with the latter pretreatment resulting in the sharpest reduction. Therefore, it seems likely that anti-CD14 along with anti-TLR4 is significantly engaged in the signaling mechanisms of LPS-mediated fibroblast proliferation.