Studies on the protective efficacy and immunogenicity of Hsp70 and Hsp83 based vaccine formulations in Leishmania donovani infected BALB/c mice

Leishmania vaccine development: A comprehensive review

Infectious diseases like leishmaniasis, malaria, HIV, tuberculosis, leprosy and filariasis are responsible for an immense burden on public health systems. Among these, leishmaniasis is under the category I diseases as it is selected by WHO (World Health Organization) on the ground of diversity and complexity. High cost, resistance and toxic effects of Leishmania traditional drugs entail identification and development of therapeutic alternative. Since the natural infection elicits robust immunity, consistence efforts are going on to develop a successful vaccine. Clinical trials have been conducted on vaccines like Leish-F1, F2, and F3 formulated using specific Leishmania antigen epitopes. Current strategies utilize individual or combined antigens from the parasite or its insect vector's salivary gland extract, with or without adjuvant formulation for enhanced efficacy. Promising animal data supports multiple vaccine candidates (Lmcen-/-, LmexCen-/-), with some already in or heading for clinical trials. The crucial challenge in Leishmania vaccine development is to translate the research knowledge into affordable and accessible control tools that refines the outcome for those who are susceptible to infection. This review focuses on recent findings in Leishmania vaccines and highlights difficulties facing vaccine development and implementation.

Exploring direct and indirect targets of current antileishmanial drugs using a novel thermal proteomics profiling approach

Visceral leishmaniasis (VL), caused by Leishmania infantum, is an oft-fatal neglected tropical disease. In the absence of an effective vaccine, the control of leishmaniasis relies exclusively on chemotherapy. Due to the lack of established molecular/genetic markers denoting parasite resistance, clinical treatment failure is often used as an indicator. Antimony-based drugs have been the standard antileishmanial treatment for more than seven decades, leading to major drug resistance in certain regions. Likewise, drug resistance to miltefosine and amphotericin B continues to spread at alarming rates. In consequence, innovative approaches are needed to accelerate the identification of antimicrobial drug targets and resistance mechanisms. To this end, we have implemented a novel approach based on thermal proteome profiling (TPP) to further characterize the mode of action of antileishmanials antimony, miltefosine and amphotericin B, as well as to better understand the mechanisms of drug resistance deployed by Leishmania. Proteins become more resistant to heat-induced denaturation when complexed with a ligand. In this way, we used multiplexed quantitative mass spectrometry-based proteomics to monitor the melting profile of thousands of expressed soluble proteins in WT, antimony-resistant, miltefosine-resistant, and amphotericin B-resistant L. infantum parasites, in the presence (or absence) of the above-mentioned drugs. Bioinformatics analyses were performed, including data normalization, melting profile fitting, and identification of proteins that underwent changes (fold change > 4) caused by complexation with a drug. With this unique approach, we were able to narrow down the regions of the L. infantum proteome that interact with antimony, miltefosine, and amphotericin B; validating previously-identified and unveiling novel drug targets. Moreover, analyses revealed candidate proteins potentially involved in drug resistance. Interestingly, we detected thermal proximity coaggregation for several proteins belonging to the same metabolic pathway (i.e., tryparedoxin peroxidase and aspartate aminotransferase in proteins exposed to antimony), highlighting the importance of these pathways. Collectively, our results could serve as a jumping-off point for the future development of innovative diagnostic tools for the detection and evaluation of antimicrobial-resistant Leishmania populations, as well as open the door for new on-target therapies.

Virulence factors of Leishmania parasite: Their paramount importance in unraveling novel vaccine candidates and therapeutic targets

Leishmaniasis is a neglected tropical disease and remains a global concern for healthcare. It is caused by an opportunistic protozoan parasite belonging to the genus Leishmania and affects millions worldwide. This disease is mainly prevalent in tropical and subtropical regions and is associated with a high risk of public morbidity and mortality if left untreated. Transmission of this deadly disease is aggravated by the bite of female sand-fly vectors (Phlebotomus and Lutzomyia). With time, significant advancement in leishmaniasis-related research has been carried out to cope with the disease burden. Still, the Leishmania parasite has also co-evolved with its host and adapted successfully within the host's lethal milieu/environment. Thus, understanding and knowledge of various leishmanial virulence factors responsible for the parasitic infection are essential for exploring drug targets and vaccine candidates. The present review elucidates the importance of virulence factors in pathogenesis and summarizes the major leishmanial virulence molecules contributing to the parasitic infection during host-pathogen interaction. Furthermore, we have also elaborated on the potential contribution of leishmanial virulence proteins in developing vaccine candidates and exploring novel therapeutics against this parasitic disease. We aim to represent a clearer picture of parasite pathogenesis within the human host that can further aid in unraveling new strategies to fight against the deadly infection of leishmaniasis.

Extracellular vesicles from Trichinella spiralis: Proteomic analysis and protective immunity

Trichinella spiralis (T. spiralis) derived extracellular vesicles (EVs) have been proposed to play a key role in regulating the host immune responses. In this study, we provided the first investigation of EVs proteomics released by T. spiralis muscle larvae (ML). T. spiralis ML EVs (Ts-ML-EVs) were successfully isolated and characterized by transmission electron microscopy (TEM) and western blotting. Using liquid chromatograph mass spectrometer (LC-MS/MS) analysis, we identified 753 proteins in the Ts-ML-EVs proteome and annotated by gene ontology (GO). These proteins were enriched in different categories by GO, kyoto encyclopedia of genes and genomes (KEGG) and domain analysis. GO enrichment analysis indicated association of protein deglutathionylation, lysosomal lumen and serine-type endopeptidase inhibitor activity with proteins which may be helpful during parasite-host interaction. Moreover, KEGG enrichment analysis revealed involvement of Ts-ML-EVs proteins in other glycan degradation, complement and coagulation cascades, proteasome and various metabolism pathways. In addition, BALB/c mice were immunized by subcutaneous injection of purified Ts-ML-EVs. Ts-ML-EVs group demonstrated a 23.4% reduction in adult worms and a 43.7% reduction in ML after parasite challenge. Cellular and humoral immune responses induced by Ts-ML-EVs were detected, including the levels of specific antibodies (IgG, IgM, IgE, IgG1 and IgG2a) as well as cytokines (IL-12, IFN-γ, IL-4 and IL-10) in serum. The results showed that Ts-ML-EVs could induce a Th1/Th2 mixed immune response with Th2 predominant. This study revealed a potential role of Ts-ML-EVs in T. spiralis biology, particularly in the interaction with host. This work provided a critical step to against T. spiralis infection based on Ts-ML-EVs.

Extracellular vesicles (EVs) play an important role in cell-cell communication. They can transport functional molecules to target tissues and cells. During parasite infection, EVs provide suitable diagnostic makers and vaccine antigens for as well as inducing host immune responses. In Trichinella spiralis (T. spiralis), we previous proved that Ts-ML-EVs exerted immunomodulatory effect that inhibited experimental colitis in mice. Based on these results, we tested the protein composition of Ts-ML-EVs and the immune protective effect of Ts-ML-EVs. Our study showed that Ts-ML-EVs contained a number of immune-related proteins and it could be potential vaccine antigen for preventing T. spiralis infection.

Immunological characterization of rLdTCP1γ for its prophylactic potential against visceral leishmaniasis in hamster model

Visceral leishmaniasis (VL) is a chronic tropical disease responsible for devastating epidemics worldwide. Though current treatment relies on drugs, the emergence of resistance, toxic side-effects, and strenuous administration has led to an ineffective remedy. Hence, vaccination remains an alternative and desirable approach for VL control. Though extensive research on anti-leishmanial vaccine candidates has been carried out in past decades, presence of an effective molecule is still missing. In the present study, we have evaluated the immunogenicity and prophylactic potential of a recombinant T-complex protein-1 gamma subunit of L. donovani (rLdTCP1γ), against VL in hamster model. The antigen exhibited in vitro stimulation of lymphoproliferative and NO response in miltefosine and amphotericin B treated hamsters depicting its immunotherapeutic/immunogenic nature. Immunization with rLdTCP1γ revealed a strong protective response against experimental VL as indicated by reduced parasite load in the spleen of immunized group compared to infected control. The immunized animals gained body weight and exhibited significant reduction in the spleen and liver weight as compared to infected controls on days 60, 90, 120 post-challenge. A substantial augmentation of cell-mediated immune response as depicted by an increased lymphocyte proliferation, nitric oxide production, DTH responses and increased levels of IgG2 was observed in rLdTCP1γ immunized hamsters. The Th1 stimulatory potential, imparted by the antigen, was found to be intensified in the presence of adjuvant Bacillus Calmette-Guérin (BCG). The efficacy was further assisted by an upregulated mRNA transcript of Th1 induced cytokines (IL-12, IFN-γ and TNFα) and downregulation of IL-4 and IL-10. The results are thus suggestive of rLdTCP1γ having the potential of a strong vaccine candidate against VL.

Review on the Role of Host Immune Response in Protection and Immunopathogenesis during Cutaneous Leishmaniasis Infection

Cutaneous leishmaniasis (CL) is a major public health problem worldwide and spreads to human via the bite of sand flies during blood meal. Following its inoculation, the promastigotes are immediately taken up by phagocytic cells and these leishmania-infected host cells produce proinflammatory cytokines that activate other immune cells and these infected host cells produce more cytokines and reactive nitrogen and oxygen species for efficient control of leishmania infection. Many experimental studies showed that resistance to infection with leishmania paraites is associated with the production of proinflammatory cytokines and activation of CD4⁺ Th1 response. On the other hand, vulnerability to this parasitic infection is correlated to production of T helper 2 cytokines that facilitate persistence of parasites and disease progression. In addition, some studies have also indicated that CD8⁺ T cells play a vital role in immune defense through cytokine production and their cytotoxic activity and excessive production of proinflammatory mediators promote amplified recruitment of cells. This could be correlated with excessive inflammatory reaction and ultimately resulted in tissue destruction and development of immunopathogenesis. Thus, there are contradictions regarding the role of immune responses in protection and immunopathogenesis of CL disease. Therefore, the aim of this paper was to review the role of host immune response in protection and its contribution to disease severity for CL infection. In order to obtain more meaningful data regarding the nature of immune response to leishmania, further in-depth studies focused on immune modulation should be conducted to develop better therapeutic strategies.

Comparative analysis of excretory-secretory products of muscle larvae of three isolates of Trichinella pseudospiralis by the iTRAQ method

Trichinella pseudospiralis is a non-encapsulated intracellular parasitic nematode that can possess a strong ability to modulate the host immune response. Here, we compared the differentially expressed proteins of excretory-secretory (ES) products in three isolates of T. pseudospiralis muscle larvae (ML) [from Russia (RUS), United States of America (USA) and Australia (AUS)] using isobaric tags for relative and absolute quantification (iTRAQ)-based technology. A total of 2591 nonredundant proteins were identified, of which 65 (146), 72 (98) and 43 (103) significantly upregulated (downregulated) differentially expressed proteins were detected among pairwise comparisons (T4RUS vs T4USA, T4AUS vs T4USA and T4RUS vs T4AUS). In addition, GO annotation, KEGG and STRING analyses were carried out on the screened differentially altered proteins. The main biological processes involved included carbohydrate metabolic processes, DNA metabolic processes, cellular protein modification processes and homeostatic processes. The majority of KEGG pathways were found to be related to the metabolic pathways, lysosome pathway and protein processing in endoplasmic reticulum. Moreover, all ES protein expression levels involved in the lysosome pathway were significantly higher in the T4USA isolate than in the other two isolates. We also found differences in the expression of some important immunoregulatory proteins, such as protein disulfide-isomerase, thioredoxin protein and deoxyribonuclease-2-alpha, between different isolates of T. pseudospiralis ML. Flow cytometry was used to detect the increase in the CD4+/CD8 + T-cell ratio in pig peripheral blood and to verify the effect of T. pseudospiralis on the Th1/Th2 polarization of the host. Quantitative real-time PCR analysis also confirmed that the changes in the transcriptional level of genes were consistent with those at the proteomic level. These findings reveal the possible role of significantly differentially expressed proteins in ES products of the different isolates of T. pseudospiralis in antagonizing and participating in the regulation of the host immune response and maintaining a stable growth environment.

Host's immune response in unresponsive and responsive patients with anthroponotic cutaneous leishmaniasis treated by meglumine antimoniate: A case-control study of Th1 and Th2 pathways

The objective of the present study was to compare the host's immune responses between unresponsive and responsive patients with anthroponotic cutaneous leishmaniasis (ACL) treated by meglumine antimoniate. A case-control study was carried out in an endemic focus in Iran. Blood samples were taken from patients and peripheral blood mononuclear cells (PBMCs) were isolated. Two wells were considered for each isolate of unresponsive and responsive patients; one was exposed to L. tropica (Lt-stimulated cells) and the other remained non-exposed (non-stimulated cells). After 24 h of incubation, whole RNA was extracted from each sample. Real-time quantitative PCR was carried out to confirm the differences in expression levels of IL-12 P40, IFN-γ, IL-1β, IL-4 and IL-10 among isolates. Data were analyzed and P < 0.05 was considered to be statistically significant. In our study, Lt-stimulated cells and non-stimulated cells in unresponsive groups demonstrated significantly lower expression levels of IL-1β, IL-12 P40 and IFN-γ genes and higher expression levels of IL-4 and IL-10 genes, compared to Lt-stimulated cells and non-stimulated cells in responsive groups. There was a negative correlation between IL-12 P40 with IL-10 and IL-1β with IL-10 in ACL Lt-stimulated cells in unresponsive group, while a positive correlation between IL-12 P40 with IL-1β and IL-12 P40 with IFN-γ in ACL Lt-stimulated cells in responsive group. Probably, different immune responses caused by various factors play a major role in the pathogenesis and development of unresponsiveness in ACL patients. The profile and timing of cytokine production correlated well with the treatment outcome of Leishmania infection.

Chimeric protein consisting of 3M2e and HSP as a universal influenza vaccine candidate: from in silico analysis to preliminary evaluation

The 23-amino acid ectodomain of influenza virus M2 protein (M2e) is highly conserved among human influenza virus variants and represents an attractive target for developing a universal vaccine. Although this peptide has limited potency and low immunogenicity, the degree of M2e density has been shown to be a critical factor influencing the magnitude of epitope-specific responses. The aim of this study was to design a chimer protein consisting of three tandem repeats of M2e peptide sequence fused to the Leishmania major HSP70 gene and evaluate its characteristics and immunogenicity. The structure of the deduced protein and its stability, aliphatic index, biocomputed half-life and the anticipated immunogenicity were analyzed by bioinformatics software. The oligonucleotides encoding 3M2e and chimer 3M2e-HSP70 were expressed in Escherichia coli and affinity purified. The immunogenicity of the purified recombinant proteins was preliminary examined in mouse model. It was predicted that fusion of HSP70 to the C-terminal of 3M2e peptide led to increased stability, hydropathicity, continuous B cell epitopes and antigenic propensity score of chimer protein. Also, the predominant 3M2e epitopes were not hidden in the chimer protein. The initial in vivo experiment showed that 3M2e-HSP chimer protein stimulates specific immune responses. In conclusion, the results of the current study suggest that 3M2e-HSP chimer protein would be an effective universal subunit vaccine candidate against influenza infection.

Evaluation of the adjuvant effect of agonists of toll-like receptor 4 and 7/8 in a vaccine against leishmaniasis in BALB/c mice

There is no effective vaccine against human leishmaniasis. Achieving successful vaccines seems to need powerful adjuvants. Separate or combined use of toll like receptor (TLR) agonists as adjuvant is a promising approach in Leishmania vaccine research. In present study, we evaluated adjuvant effect of separate or combined use of a TLR7/8 agonist, R848 and a TLR4 agonist, monophosphoryl lipid A (MPL) beside soluble Leishmania antigen (SLA) in BALB/c mice. Mice were vaccinated three times by SLA with separate or combined TLR7/8 and TLR4 agonists and were then challenged by Leishmania major. Delay type hypersensitivity, lesion development, parasite load, and cytokines (interferon gamma, and interleukin-10) response were assessed. Results showed: 1) MPL can slightly assist SLA in parasite load reduction, but it is not able to increase SLA ability in evoking DTH and cytokine responses or decreasing lesion diameter. 2) R848 does not affect the DTH response and parasite load of mice vaccinated with SLA, but it decreases/inhibits cytokine responses induced by SLA, leading to increase lesion diameter. 3) MPL neutralized inhibitory effect of R848. In overall, these data emphasize that MPL slightly assists SLA to make a more potent vaccine, but R848 is not a good adjuvant to induce T cell-dependent immune response in BALB/c mice, and therefore combination of these TLR agonists in the current formulation, is not recommended for making a more powerful adjuvant.

In Vitro Evaluation of Influenza M2 and Leishmania major HSP70 (221-604) Chimer Protein

Background:

Permanent antigenic variation of influenza viruses causes a major concern to develop an effective human influenza vaccine. Conserved antigens are new vaccine candidates because it is not necessary to match the prepared vaccine with circulating strains. Ion channel M2 protein is conserved among all influenza A viruses, allowing the virus to enter host cells.

Objectives:

To prepare an effective vaccine against influenza A viruses, a chimerical DNA plasmid encoding Influenza virus M2 protein and Leishmania major HSP70 was constructed.

Materials and Methods:

Influenza A/New Caledonia/20/99 (H1N1) was inoculated into MDCK cell line and total RNA was extracted. The full length M2 gene was amplified by RT-PCR using designed specific primers, cloned into pGEM-T Easy cloning vector and completely sequenced. The M2 gene was then subcloned into the pcDNA upstream of HSP70 gene. Recombinant plasmids were transfected into COS-7 cells to evaluate protein expression.

Results:

The recombinant plasmids were confirmed by PCR, restriction enzyme analysis and sequencing. Three dimensional structure of chimer protein was assessed using specific software. Transient protein expression in eukaryotic cells was confirmed by specific mRNA detection, indirect Immunofluorescence test and western blotting.

Conclusions:

M2-HSP70 chimer protein was successfully expressed in eukaryotic cells. Computational studies of chimer peptide sequence revealed that fusing HSP to the C-terminal of M2 protein does not mask the predominant epitope of M2. HSP70 is a molecular chaperon and immunostimulatory component. Genetically fusing antigens to HSPs leads to the enrichment of DNA vaccine potency. The immunogenicity of this construct with different formulation would be evaluated in further investigations.

Th1 stimulatory proteins of Leishmania donovani: comparative cellular and protective responses of rTriose phosphate isomerase, rProtein disulfide isomerase and rElongation factor-2 in combination with rHSP70 against visceral leishmaniasis

In visceral leishmaniasis, the recovery from the disease is always associated with the generation of Th1-type of cellular responses. Based on this, we have previously identified several Th1-stimulatory proteins of Leishmania donovani -triose phosphate isomerase (TPI), protein disulfide isomerase (PDI) and elongation factor-2 (EL-2) etc. including heat shock protein 70 (HSP70) which induced Th1-type of cellular responses in both cured Leishmania patients/hamsters. Since, HSPs, being the logical targets for vaccines aimed at augmenting cellular immunity and can be early targets in the immune response against intracellular pathogens; they could be exploited as vaccine/adjuvant to induce long-term immunity more effectively. Therefore, in this study, we checked whether HSP70 can further enhance the immunogenicity and protective responses of the above said Th1-stimulatory proteins. Since, in most of the studies, immunogenicity of HSP70 of L. donovani was assessed in native condition, herein we generated recombinant HSP70 and tested its potential to stimulate immune responses in lymphocytes of cured Leishmania infected hamsters as well as in the peripheral blood mononuclear cells (PBMCs) of cured patients of VL either individually or in combination with above mentioned recombinant proteins. rLdHSP70 alone elicited strong cellular responses along with remarkable up-regulation of IFN-γ and IL-12 cytokines and extremely lower level of IL-4 and IL-10. Among the various combinations, rLdHSP70 + rLdPDI emerged as superior one augmenting improved cellular responses followed by rLdHSP70 + rLdEL-2. These combinations were further evaluated for its protective potential wherein rLdHSP70 + rLdPDI again conferred utmost protection (∼80%) followed by rLdHSP70 + rLdEL-2 (∼75%) and generated a strong cellular immune response with significant increase in the levels of iNOS transcript as well as IFN-γ and IL-12 cytokines which was further supported by the high level of IgG2 antibody in vaccinated animals. These observations indicated that vaccine(s) based on combination of HSP70 with Th1-stimulatory protein(s) may be a viable proposition against intracellular pathogens.

Synthesis and antileishmanial evaluation of some 2,3-disubstituted-4(3H)-quinazolinone derivatives

Background

Leishmaniasis is a neglected tropical parasitic diseases affecting millions of people around the globe. Quinazolines are a group of compounds with diverse pharmacological activities. Owing to their promising antileishmanial activities, some 3-aryl-2-(substitutedstyryl)-4(3H)-quinazolinones were synthesized in good yields (65.2% to 86.4%).

Results

The target compounds were synthesized by using cyclization, condensation, and hydrolysis reactions. The structures of the synthesized compounds were determined using elemental microanalysis, infrared (IR), and proton nuclear magnetic resonance (¹H NMR). The in vitro antileishmanial activities of the synthesized compounds were evaluated using Leishmania donovani strain. All the synthesized compounds displayed appreciable antileishmanial activities (IC₅₀ values, 0.0128 to 3.1085 μg/ml) as compared to the standard drug miltefosine (IC₅₀ = 3.1911 μg/ml). (E)-2-(4-chlorostyryl)-3-p-tolyl-4(3H)-quinazolinone (7) is the compound with the most promising antileishmanial activities (IC₅₀ = 0.0128 μg/ml) which is approximately 4 and 250 times more active than the standard drugs amphotericin B deoxycholate (IC₅₀ = 0.0460 μg/ml) and miltefosine (IC₅₀ = 3.1911 μg/ml), respectively.

Conclusions

The results obtained from this investigation indicate that the synthesized and biologically evaluated quinazoline compounds showed promising antileishmanial activities and are good scaffolds for the synthesis of different antileishmanial agents.

Electronic supplementary material

The online version of this article (doi:10.1186/s13588-014-0010-1) contains supplementary material, which is available to authorized users.

Shotgun proteomics to unravel the complexity of the Leishmania infantum exoproteome and the relative abundance of its constituents

The exoproteome of some Leishmania species has revealed important insights into host-parasite interaction, paving the way for the proposal of novel disease-oriented interventions. The focus of the present investigation constituted the molecular profile of the L. infantum exoproteome revealed by a shotgun proteomic approach. Promastigotes under logarithmic phase of growth were obtained and harvested by centrifugation at different time points. Cell integrity was evaluated through the counting of viable parasites using propidium iodide labeling, followed by flow cytometry analysis. The 6h culture supernatant, operationally defined here as exoproteome, was then conditioned to in solution digestion and the resulting peptides submitted to mass spectrometry. A total of 102 proteins were identified and categorized according to their cellular function. Their relative abundance index (emPAI) allowed inference that the L. infantum exoproteome is a complex mixture dominated by molecules particularly involved in nucleotide metabolism and antioxidant activity. Bioinformatic analyses support that approximately 60% of the identified proteins are secreted, of which, 85% possibly reach the extracellular milieu by means of non-classic pathways. At last, sera from naturally infected animals, carriers of differing clinical forms of Canine Visceral Leishmaniasis (CVL), were used to test the immunogenicity associated to the L. infantum exoproteome. Western blotting experiments revealed that this sub-proteome was useful at discriminating symptomatic animals from those exhibiting other clinical forms of the disease. Collectively, the molecular characterization of the L. infantum exoproteome and the preliminary immunoproteomic assays opened up new research avenues related to treatment, prognosis and diagnosis of CVL.

Immunostimulatory effects of Leishmania infantum HSP70 recombinant protein on dendritic cells in vitro and in vivo

Background: Activation of dendritic cells (DCs) has an important role in immunity against Leishmania. Aim: We investigated the effect of Leishmania infantum (L. infantum) heat shock protein 70 recombinant protein (rHSP70) as a vaccine on DC maturation and function. Materials & methods: BALB/c mouse splenic DCs were isolated and treated with different concentrations of rHSP70. Maturation markers, cytokine production and capability of DCs to proliferate allogeneic T cells were evaluated. Furthermore, this recombinant protein was injected into BALB/c mice, and expression of CD86, CD40 and MHC class II molecules by their splenic DCs were evaluated. Results: rHSP70 significantly increases the production of IL-12p70 by DCs. It had no effect on allogeneic T-cell proliferation in mixed lymphocyte reaction. It increased IFN-γ and decreased IL-4 cytokine level in mixed lymphocyte reaction supernatant. The in vitro study showed that rHSP70 had no significant effect neither on the percentage of CD40+, CD86+ and MHC class II+ DCs nor on the mean fluorescent intensity. However, in vivo results showed that rHSP70 increases the percentage of CD86-, CD40- and MHC class II-expressing cells as well as mean fluorescent intensity of CD40 and MHC class II. Conclusion: This study demonstrated the capability of L. infantum-derived rHSP70 in maturating BALB/c mice splenic DCs and in vivo polarization of immunity to a Th1 response.

Tinospora cordifolia as a protective and immunomodulatory agent in combination with cisplatin against murine visceral leishmaniasis

Effect of pure herb, Tinospora cordifolia was studied for its hepatoprotective, nephroprotective and immunomodulatory activity against high dose cisplatin treatment in Leishmania donovani infected BALB/c mice. Administration of cisplatin (5mg/kg b.wt. daily for 5 days, i.p.) reduced the parasite load in L. donovani infected BALB/c mice but produced damage in liver and kidney as manifested biochemically by an increase in serum glutamate oxaloacetate transaminase (SGOT), serum glutamate pyruvate transaminase (SGPT), serum urea, serum creatinine and various electrolytes etc. These biochemical analyses were further supported by cisplatin induced morphological changes in kidney, liver and spleen. To combat this pure herb, T. cordifolia (100mg/kg b.wt. for 15 days daily) was used in combination with cisplatin in L. donovani infected BALB/c mice and it was found that all the aforementioned changes were effectively attenuated by T. cordifolia when administered in combination with cisplatin. Moreover, flow cytometric analysis of lymphocyte surface markers of T cells (CD3+, CD4+ and CD8+), NK1.1 and B cells (CD19) indicated prominent enhancement in proliferation and differentiation of lymphocytes. T. cordifolia in combination with cisplatin selectively induced Th1 type of immune response as depicted by enhanced levels of IFN-γ and IL-2 whereas Th2 specific cytokines IL-4 and IL-10 observed a moderate decline. Confirmation of Th1 polarization was further obtained from augmented levels of IgG2a over IgG1 and heightened DTH (delayed type hypersensitivity) response. Thus, our results suggest that treatment by T. cordifolia may be a critical remedy for the amelioration of adverse effects of cisplatin. Thus, this might serve as a novel combination against visceral leishmaniasis in future.

Studies on the protective and immunomodulatory efficacy of Withania somnifera along with cisplatin against experimental visceral leishmaniasis

Visceral leishmaniasis (VL) or kala-azar continues to persist as one of the major public health problems in many tropical countries. However, no effective treatment for cure of the disease is yet available. The present study was designed to investigate the nephroprotective and immunomodulatory effect of Withania somnifera in cisplatin-treated Leishmania donovani-infected BALB/c mice. Administration of cisplatin (5 mg/kg body weight (b.wt.) daily for 5 days, i.p.) reduced the parasite load in L. donovani-infected BALB/c mice but produced damage in liver and kidney as manifested biochemically by an increase in SGOT, SGPT, serum creatinine, and blood urea nitrogen, respectively. The biochemical analysis was further substantiated by histopathological changes induced in the liver and kidney by cisplatin. However, W. somnifera (350 mg/kg b.wt. daily for 15 days, orally) when given along with cisplatin, significantly reversed these changes and enhanced the antileishmanial efficacy of the drug, cisplatin. But, when W. somnifera was given alone per se it showed less antileishmanial potential. The results also indicate that W. somnifera in combination with cisplatin resulted in significant selective upregulation of Th1 type of immunity because it guided expression of T helper cell (Th1)1 cytokines, IFN-gamma and IL-2; augmented levels of IgG2a over IgG1; and heightened DTH (delayed type hypersensitivity) responses while Th2 cytokines, IL-4, and IL-10 were downregulated. Flow cytometric analysis of W. somnifera and cisplatin-treated animals showed an increase in the percentage of T cells (CD4+, CD8+) and NK1.1 suggesting its effect on activation of T cells. These results confirm the protective and immunomodulatory activity of W. somnifera suggesting that it along with cisplatin may be a critical remedy for the amelioration of adverse effects of cisplatin. Thus, this combination appears to offer a fruitful strategy for treatment of VL.

Protective immunity using MPL-A and autoclaved Leishmania donovani as adjuvants along with a cocktail vaccine in murine model of visceral leishmaniasis

The current study is an extension of our previous study where we tested the protective efficacy of gp63 and Hsp70 against murine visceral leishmaniasis. The cocktail vaccine was combined with MPL-A and ALD adjuvants and the protection afforded by the three vaccines was compared. Inbred BALB/c mice were immunized twice at an interval of two weeks with the vaccine formulations. Two weeks after the booster, they were challenged with 10(7) promastigotes of Leishmania donovani and sacrificed on 30, 60 and 90 days post infection/challenge. The protective efficacy of vaccines was analyzed by assessment of the hepatic and splenic parasite burden and generation of cellular and humoral immune responses. The immunized animals revealed a significant reduction in parasite burden as compared to the infected controls. These animals also showed heightened DTH response, increased generation of IgG2a, IFN-γ and IL-2 by spleen cells. This was also accompanied by a decrease in the levels of IgG1 and IL-10. Mice immunized with gp63+Hsp70+MPL-A exhibited significantly greater protection in comparison to those immunized with gp63+Hsp70+ALD.

Mitigating an undesirable immune response of inherent susceptibility to cutaneous leishmaniosis in a mouse model: the role of the pathoantigenic HISA70 DNA vaccine

Leishmania major is the major cause of cutaneous leishmaniosis (CL) outside of the Americas. In the present study we have cloned six Leishmania genes (H2A, H2B, H3, H4, A2 and HSP70) into the eukaryotic expression vector pCMVβ-m2a, resulting in pCMV-HISA70m2A, which encodes all six pathoantigenic proteins as a single polyprotein. This expression plasmid has been evaluated as a novel vaccine candidate in the BALB/c mouse model of CL. The DNA vaccine shifted the immune response normally induced by L. major infection away from a Th2-specific pathway to one of basal susceptibility. Immunization with pCMV-HISA70m2A dramatically reduced footpad lesions and lymph node parasite burdens relative to infected control mice. Complete absence of visceral parasite burden was observed in all 12 immunized animals but not in any of the 24 control mice. Moreover, vaccinated mice produced large amounts of IFN-γ, IL-17 and NO at 7 weeks post-infection (pi), and they showed lower arginase activity at the site of infection, lower IL-4 production and a weaker humoral immune response than infected control mice. Taken together, these results demonstrate the ability of the HISA70 vaccine to shift the murine immune response to L. major infection away from an undesirable, Th2-specific pathway to a less susceptible-like pathway involving Th1 and Th17 cytokine profiles.

ELISA and western blotting for the detection of Hsp70 and Hsp83 antigens of Leishmania donovani

Visceral leishmaniasis (VL) is endemic in the tropical, sub-tropical regions of Asia, Africa, the Mediterranean, Southern Europe and South and Central America. Approximately 500,000 new cases are reported annually. Classically the diagnosis of VL is confirmed by the demonstration of the parasite in aspirates of spleen, bone marrow or liver which can yield false negative results, also these methods are invasive. In this study, we aimed to evaluate the serodiagnostic potential of two heat shock proteins (Hsps) i.e. Hsp70 and Hsp83 in combination by ELISA and western blotting in mouse model. Parasite proteins were separated by SDS-PAGE and transferred to PVDF membranes which were further incubated with serum samples of infected mice for visualizing different bands. Both the bands i.e. Hsp70 and Hsp83 were simultaneously visualized in all infected groups on different post infection days. The presence of both the antigens was also detected by sandwich ELISA. The results suggest that the simultaneous occurrence of both the antigens Hsp70 and Hsp83 may be useful in serodiagnostic assay of VL as it may reduce the need for traumatic bone marrow sampling and risky spleen aspiration.

Vaccine Development Against Leishmania donovani

Visceral leishmaniasis (VL) caused by Leishmania donovani and Leishmania infantum/chagasi represents the second most challenging infectious disease worldwide, leading to nearly 500,000 new cases and 60,000 deaths annually. Zoonotic VL caused by L. infantum is a re-emergent canid zoonoses which represents a complex epidemiological cycle in the New world where domestic dogs serve as a reservoir host responsible for potentially fatal human infection and where dog culling is the only measure for reservoir control. Life-long immunity to VL has motivated development of prophylactic vaccines against the disease but very few have progressed beyond the experimental stage. No licensed vaccine is available till date against any form of leishmaniasis. High toxicity and increasing resistance to the current chemotherapeutic regimens have further complicated the situation in VL endemic regions of the world. Advances in vaccinology, including recombinant proteins, novel antigen-delivery systems/adjuvants, heterologous prime-boost regimens and strategies for intracellular antigen presentation, have contributed to recent advances in vaccine development against VL. Attempts to develop an effective vaccine for use in domestic dogs in areas of canine VL should be pursued for preventing human infection. Studies in animal models and human patients have revealed the pathogenic mechanisms of disease progression and features of protective immunity. This review will summarize the accumulated knowledge of pathogenesis, immune response, and prerequisites for protective immunity against human VL. Authors will discuss promising vaccine candidates, their developmental status and future prospects in a quest for rational vaccine development against the disease. In addition, several challenges such as safety issues, renewed and coordinated commitment to basic research, preclinical studies and trial design will be addressed to overcome the problems faced in developing prophylactic strategies for protection against this lethal infection.

Leishmaniasis: vaccine candidates and perspectives

Leishmania is a protozoan parasite and a causative agent of the various clinical forms of leishmaniasis. High cost, resistance and toxic side effects of traditional drugs entail identification and development of therapeutic alternatives. The sound understanding of parasite biology is key for identifying novel drug targets, that can induce the cell mediated immunity (mainly CD4+ and CD8+ IFN-gamma mediated responses) polarized towards a Th1 response. These aspects are important in designing a new vaccine along with the consideration of the candidates with respect to their ability to raise memory response in order to improve the vaccine performance. This review is an effort to identify molecules according to their homology with the host and their ability to be used as potent vaccine candidates.

Leishmania donovani whole cell antigen delivered with adjuvants protects against visceral leishmaniasis in vervet monkeys (Chlorocebus aethiops)

In a previous immunogenicity and efficacy study in mice, montanide ISA 720 (MISA) was indicated to be a better adjuvant than bacillus calmette guerin vaccine (BCG) for a Leishmania vaccine. In the present study, we report the safety, immunogenicity and efficacy of Leishmania donovani (L. donovani) sonicated antigen delivered with alum-BCG (AlBCG), MISA or monophosphoryl lipid A (MPLA) in vervet monkeys following intradermal inoculums. Vaccinated and control animals were challenged with virulent L. donovani parasites and the parasitic burden was determined. Only animals vaccinated with alum-BCG adversely reacted to the inoculum by producing ulcerative erythematous skin indurations. Non-parametric ANOVA followed by a post test showed significantly higher IgG antibodies, and revealed the presence of lymphoproliferative and interferon gamma responses in both AlBCG+Ag and MISA+Ag as compared to the MPLA+Ag or other groups (P < 0.001). We conclude that L. donovani sonicated antigen containing MISA is safe and is associated with protective immune response against Leishmania donovani infection in the vervet monkey model.