Immunotherapy against visceral leishmaniasis with the nucleoside hydrolase-DNA vaccine of Leishmania donovani

Green-synthesized chitosan‑carbon dot nanocomposite as turn-on aptasensor for detection and quantification of Leishmania infantum parasite

Leishmania is one of the most common diseases between human and animals, caused by Leishmania infantum parasite. Here, we have developed an ultra-selective turn-on fluorescent probe based on an aptamer and Chitosan-CD nanocomposite. The CD used in this study were synthesized using Quercus cap extract and a microwave-assisted approach. The Chitosan-CD nanocomposite was optimized using several microscopic and spectroscopic techniques to possess a bright fluorescence emission before adding aptamer and totally quenched fluorescence after addition of aptamer. The designed probe was proficient in the detection and quantification Leishmania infantum parasite by selective targeting of poly(A) binding protein (PABP) on the surface of the parasite. The designed fluorescent biosensor with high sensitivity, excellent selectivity, and a limit of detection (LOD) of 94 cells/mL of the Leishmania infantum parasite as well as a linear response in the ranges of 188-750 cells/mL and 3000-6000 cells/mL (R2 ≥ 0.98 for both linear ranges). Additionally, the selectivity of the designed probe was evaluated in the presence of different pathogenic species such as Trypanosoma brucei parasite and Staphylococcus aureus bacteria, as well as LiIF2α and LiP2a and BSA proteins as interference substances. The results of this study shows that using Chitosan-CD nanocomposite is a great strategy for developing selective turn-on probes with extraordinary accuracy and sensitivity in identifying Leishmania infantum parasite, especially in the early stages of the disease, and it is promising for the future clinical applications.

Vaccination in Leishmaniasis: A Review Article

Leishmaniasis is caused by protozoan Leishmania parasites that are transmitted through female sandfly bites. The disease is predominantly endemic to the tropics and semi-tropics and has been reported in more than 98 countries. Due to the side effects of anti-Leishmania drugs and the emergence of drug-resistant isolates, there is currently no encouraging prospect of introducing an effective therapy for the disease. Hence, it seems that the key to disease control management is the introduction of an effective vaccine, particularly against its cutaneous form. Advances in understanding underlying immune mechanisms are feasibale using a variety of candidate antigens, including attenuated live parasites, crude antigens, pure or recombinant Leishmania proteins, Leishmania genes encoding protective proteins, as well as immune system activators from the saliva of parasite vectors. However, there is still no vaccine against different types of human leishmaniasis. In this study, we review the works conducted or being performed in this field.

Development of the Antileishmanial Vaccine

Search for an efficacious antileishmanial vaccine has led to clinical trials of numerous vaccine candidates in the past few decades. As no promising candidate has emerged from these studies, novel vaccine modalities and vaccine assessment techniques are still emerging for antileishmanial vaccine development. Briefly, this chapter discusses: (a) history and timeline of antileishmanial vaccine development; (b) techniques utilized for developing whole-parasite and subunit-based antileishmanial vaccine formulations, and (c) immunogenicity and post-challenge protective efficacy assessment of vaccine candidates.

Cross-protective efficacy of immuno-stimulatory recombinant Brugia malayi protein HSP60 against the Leishmania donovani in BALB/c mice

Coinfection of Leishmania with bacteria, viruses, protozoans, and nematodes alter the immune system of the host, thereby influencing the disease outcomes. Here, we have determined the immunogenic property and protective efficacy of the cross-reactive molecule HSP60 of filarial parasite B. malayi against the L. donovani in BALB/c mice. Parasitological parameters results showed a significant decrease in the parasite burden (~59%; P < 0.001) and also a substantial increase in the delayed-type hypersensitivity (DTH) response (P < 0.001) in mice immunized with 10 μg of rBmHSP60. Protection against L. donovani in mice immunized with rBmHSP60 resulted from activation of the T cells, which is characterized by higher levels of nitric oxide (NO) production, enhanced cell proliferation, higher levels (expression and release) of IFN- γ, TNF- α, and IL-12, also, higher production of IgG and IgG2a antibodies. This strong Th1 immune response creates an inflammatory domain for L. donovani and protects the host from VL.

Leishmaniasis: where are we and where are we heading?

Leishmaniasis is a zoonotic disease in humans caused by the bite of a parasite-infected sandfly. The disease, widely referred to as "poor man's disease," affects millions of people worldwide. The clinical manifestation of the disease depends upon the species of the parasite and ranges from physical disfigurement to death if left untreated. Here, we review the past, present, and future of leishmaniasis in detail. The life cycle of Leishmania sp., along with its epidemiology, is discussed, and in addition, the line of therapeutics available for treatment currently is examined. The current status of the disease is critically evaluated, keeping emerging threats like human immunodeficiency virus (HIV) coinfection and post kala-azar dermal leishmaniasis (PKDL) into consideration. In summary, the review proposes a dire need for new therapeutics and reassessment of the measures and policies concerning emerging threats. New strategies are essential to achieve the goal of leishmaniasis eradication in the next few decades.

The Role of Nitro (NO2-), Chloro (Cl), and Fluoro (F) Substitution in the Design of Antileishmanial and Antichagasic Compounds

Neglected tropical diseases (NTDs) are responsible for over 500,000 deaths annually and are characterized by multiple disabilities. Leishmaniasis and Chagas diseases are among the most severe NTDs, and are caused by the Leishmania sp and Trypanosoma cruzi, respectively. Glucantime, pentamidine, and miltefosine are commonly used to treat leishmaniasis, whereas nifurtimox, benznidazole are current treatments for Chagas disease. However, these treatments are associated with drug resistance and severe side effects. Hence, the development of synthetic products, especially those containing N0₂, F, or Cl, are known to improve biological activity. The present work summarizes the information on the antileishmanial and antitrypanosomal activity of nitro-, chloro-, and fluorosynthetic derivatives. Scientific publications referring to halogenated derivatives in relation to antileishmanial and antitrypanosomal activities were hand-searched in databases such as SciFinder, Wiley, Science Direct, PubMed, ACS, Springer, Scielo, and so on. According to the literature information, more than 90 compounds were predicted as lead molecules with reference to their IC₅₀/EC₅₀ values in in vitro studies. It is worth mentioning that only active compounds with known cytotoxic effects against mammalian cells were considered in the present study. The observed activity was attributed to the presence of nitro-, fluoro-, and chloro-groups in the compound backbone. All in all, nitro and halogenated derivatives are active antileishmanial and antitrypanosomal compounds and can serve as the baseline for the development of new drugs against leishmaniasis and Chagas disease. However, efforts in in vitro and in vivo toxicity studies of the active synthetic compounds is still needed. Pharmacokinetic studies and the mechanism of action of the promising compounds need to be explored. The use of new catalysts and chemical transformation can afford unexplored halogenated compounds with improved antileishmanial and antitrypanosomal activity.

Leishmania eukaryotic elongation Factor-1 beta protein is immunogenic and induces parasitological protection in mice against Leishmania infantum infection

Treatment for visceral leishmaniasis (VL) is hampered mainly by the toxicity and/or high cost of antileishmanial drugs. What is more, variability on sensitivity and/or specificity of diagnostic tests hinders effective disease management. In this context, prophylactic vaccination should be considered as a strategy to prevent disease. In the present study, immunogenicity of the Leishmania eukaryotic Elongation Factor-1 beta (EF1b) protein, classified as a Leishmania virulence factor, was evaluated in vitro and in vivo and tested, for the first time, as a vaccine candidate against Leishmania infantum infection. The antigen was administered as DNA vaccine or as recombinant protein (rEF1b) delivered in saponin. BALB/c mice immunization with a DNA plasmid and recombinant protein plus saponin induced development of specific Th1-type immunity, characterized by high levels of IFN-γ, IL-12, GM-CSF, both T cell subtypes and antileishmanial IgG2a isotype antibodies, before and after infection. This immunological response to the vaccines was corroborated further by parasitological analysis of the vaccinated and then challenged mice, which showed significant reductions in the parasite load in their liver, spleen, bone marrow and draining lymph nodes, when compared to the controls. Vaccination using rEF1b/saponin induced a more robust Th1 response and parasitological protection when compared to the DNA vaccine. Furthermore, in vitro analysis of lymphoproliferation, IFN-γ and IL-10 levels in human PBMC cultures showed as well development of a specific Th1-type response. In conclusion, data suggest that EF1b could be a promising vaccine candidate to protect against L. infantum infection.

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

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

Anti-Leishmanial Vaccines: Assumptions, Approaches, and Annulments

Leishmaniasis is a neglected protozoan parasitic disease that occurs in 88 countries but a vaccine is unavailable. Vaccination with live, killed, attenuated (physically or genetically) Leishmania have met with limited success, while peptide-, protein-, or DNA-based vaccines showed promise only in animal models. Here, we critically assess several technical issues in vaccination and expectation of a host-protective immune response. Several studies showed that antigen presentation during priming and triggering of the same cells in infected condition are not comparable. Altered proteolytic processing, antigen presentation, protease-susceptible sites, and intracellular expression of pathogenic proteins during Leishmania infection may vary dominant epitope selection, MHC-II/peptide affinity, and may deter the reactivation of desired antigen-specific T cells generated during priming. The robustness of the memory T cells and their functions remains a concern. Presentation of the antigens by Leishmania-infected macrophages to antigen-specific memory T cells may lead to change in the T cells' functional phenotype or anergy or apoptosis. Although cells may be activated, the peptides generated during infection may be different and cross-reactive to the priming peptides. Such altered peptide ligands may lead to suppression of otherwise active antigen-specific T cells. We critically assess these different immunological issues that led to the non-availability of a vaccine for human use.

Immunomodulatory and antiparasitic effects of garlic-arteether combination via nitric oxide pathway in Plasmodium berghei-infected mice

Many reports indicate medicinal value of garlic (Allium sativum), a popular herbal medicine used worldwide, and its therapeutic effect against several diseases. Earlier studies in our laboratory have shown a potential therapeutic role of garlic-artemisinin combination in mice infected with Plasmodium berghei. A single dose of α, β-arteether with three oral doses of garlic provides almost 95% protection. The present study aims to understand the mode of action of this combination. We have documented the level of nitric oxide (NO), a key molecule of protection and have seen in the reversal of organ morphology caused by malaria infection. The combination effects on the (a) survival rate and degree of parasitemia and (b) NO levels in blood, liver, spleen and thymus of malaria-infected mice were investigated. During the study, liver, spleen and thymus cell suspensions were assessed for immunobiochemical alterations of NO levels. The increase in NO level after infection appears to be unable to protect, whereas striking increase in spleen and thymus leads to protection against infection, and is further confirmed by detection of increased inducible nitric oxide synthase mRNA expression levels in different organs by RT-PCR. In addition, the role of T cell subsets during combination treatment was also studied. All these results indicate a potential mechanism of protection through NO pathway in combination-treated animals after malaria infection and may lead to an immunotherapy trial of malaria disease.

Visceral leishmaniasis: An overview of vaccine adjuvants and their applications

Although there has been an extensive research on vaccine development over the last decade and some vaccines have been commercialized for canine visceral leishmaniasis (CVL), but as yet no effective vaccine is available for anthroponotic VL which may partly be due to the absence of an appropriate adjuvant system. Vaccines alone yield poor immunity hence requiring an adjuvant which can boost the immunosuppressed state of VL infected individuals by eliciting adaptive immune responses to achieve required immunological enhancement. Recent studies have documented the continuous efforts that are being made in the field of adjuvants research in an attempt to render vaccines more effective. This review article focuses on adjuvants, particularly particulate and non-particulate ones, which have been assessed with VL vaccine candidates in several preclinical and clinical trials outlining the induction of immune responses obtained from these studies. Moreover, we have emphasized the applicability of multiple adjuvants combination for an improvement in the potential of a VL vaccine.

Nucleoside Hydrolase NH 36: A Vital Enzyme for the Leishmania Genus in the Development of T-Cell Epitope Cross-Protective Vaccines

NH36 is a vital enzyme of the DNA metabolism and a specific target for anti-Leishmania chemotherapy. We developed second-generation vaccines composed of the FML complex or its main native antigen, the NH36 nucleoside hydrolase of Leishmania (L.) donovani and saponin, and a DNA vaccine containing the NH36 gene. All these vaccines were effective in prophylaxis and treatment of mice and dog visceral leishmaniasis (VL). The FML-saponin vaccine became the first licensed veterinary vaccine against leishmaniasis (Leishmune®) which reduced the incidence of human and canine VL in endemic areas. The NH36, DNA or recombinant protein vaccines induced a Th1 CD4+IFN-γ+ mediated protection in mice. Efficacy against VL was mediated by a CD4+TNF-α T lymphocyte response against the NH36-F3 domain, while against tegumentary leishmaniasis (TL) a CD8+ T lymphocyte response to F1 was also required. These domains were 36-41 % more protective than NH36, and a recombinant F1F3 chimera was 21% stronger than the domains, promoting a 99.8% reduction of the parasite load. We also identified the most immunogenic NH36 domains and epitopes for PBMC of active human VL, cured or asymptomatic and DTH+ patients. Currently, the NH36 subunit recombinant vaccine is turning into a multi-epitope T cell synthetic vaccine against VL and TL.

NH36 and F3 Antigen-Primed Dendritic Cells Show Preserved Migrating Capabilities and CCR7 Expression and F3 Is Effective in Immunotherapy of Visceral Leishmaniasis

Physical contact between dendritic cells (DCs) and T cell lymphocytes is necessary to trigger the immune cell response. CCL19 and CCL21 chemokines bind to the CCR7 receptor of mature DCs, and of T cells and regulate DCs migration to the white pulp (wp) of the spleen, where they encounter lymphocytes. In visceral leishmaniasis (VL), cellular immunosuppression is mediated by impaired DC migration due to the decreased chemokine secretion by endothelium and to the reduced DCs CCR7 expression. The Leishmania (L.) donovani nucleoside hydrolase NH36 and its C-terminal domain, the F3 peptide are prominent antigens in the generation of preventive immunity to VL. We assessed whether these vaccines could prevent the migrating defect of DCs by restoring the expression of CCR7 receptors. C57Bl6 mice were vaccinated with NH36 and F3 and challenged with L. (L.) infantum chagasi. The F3 vaccine induced a 100% of survival and a long-lasting immune protection with an earlier CD4+Th1 response, with secretion of higher IFN-γ and TNF-α/IL-10 ratios, and higher frequencies of CD4+ T cells secreting IL-2+, TNF-α+, or IFN-γ+, or a combination of two or the three cytokines (IL-2+TNF-α+IFN-γ+). The CD8+ T cell response was promoted earlier by the NH36-vaccine, and later by the F3-vaccine. Maximal number of F3-primed DCs migrated in vitro in response to CCL19 and showed a high expression of CCR7 receptors (26.06%). Anti-CCR7 antibody treatment inhibited DCs migration in vitro (90%) and increased parasite load in vivo. When transferred into 28-day-infected mice, only 8% of DCs from infected, 59% of DCs from NH36-vaccinated, and 84% of DCs from F3-vaccinated mice migrated to the wp. Consequently, immunotherapy of infected mice with F3-primed DCs only, promoted increases in corporal weight and reductions of spleen and liver parasite loads and relative weights. Our findings indicate that vaccination with F3-vaccine preserves the maturation, migration properties and CCR7 expression of DCs, which are essential processes for the generation of cell-mediated immunity. The F3 vaccine is more potent in reversing the migration defect that occurs in VL and, therefore, more efficient in immunotherapy of VL.

Ethnoveterinary perspectives and promising future

In this review, we have discussed the recent potential effects of plants and their derivatives in treating diseases of veterinary importance in livestock. The therapeutic value of these natural products depends upon their bioactive metabolites that are developed and isolated from crude plants, thus produced a selective action on the body. The crises of drug resistance in most pathogenic bacteria and parasites that cause economic loss in animals necessitate developing new sources for drugs to overcome therapeutic failure. We summarized the different antibacterial and antiparasitic plants with their bioactive compounds that have widely used in animals. Finally, the environmental friendly feed additives that may be used as alternatives to an antibiotic growth promoter for broiler chickens were illustrated.

A third generation vaccine for human visceral leishmaniasis and post kala azar dermal leishmaniasis: First-in-human trial of ChAd63-KH

BACKGROUND

Visceral leishmaniasis (VL or kala azar) is the most serious form of human leishmaniasis, responsible for over 20,000 deaths annually, and post kala azar dermal leishmaniasis (PKDL) is a stigmatizing skin condition that often occurs in patients after successful treatment for VL. Lack of effective or appropriately targeted cell mediated immunity, including CD8+ T cell responses, underlies the progression of VL and progression to PKDL, and can limit the therapeutic efficacy of anti-leishmanial drugs. Hence, in addition to the need for prophylactic vaccines against leishmaniasis, the development of therapeutic vaccines for use alone or in combined immuno-chemotherapy has been identified as an unmet clinical need. Here, we report the first clinical trial of a third-generation leishmaniasis vaccine, developed intentionally to induce Leishmania-specific CD8+ T cells.

METHODS

We conducted a first-in-human dose escalation Phase I trial in 20 healthy volunteers to assess the safety, tolerability and immunogenicity of a prime-only adenoviral vaccine for human VL and PKDL. ChAd63-KH is a replication defective simian adenovirus expressing a novel synthetic gene (KH) encoding two Leishmania proteins KMP-11 and HASPB. Uniquely, the latter was engineered to reflect repeat domain polymorphisms and arrangements identified from clinical isolates. We monitored innate immune responses by whole blood RNA-Seq and antigen specific CD8+ T cell responses by IFNγ ELISPOT and intracellular flow cytometry.

FINDINGS

ChAd63-KH was safe at intramuscular doses of 1x1010 and 7.5x1010 vp. Whole blood transcriptomic profiling indicated that ChAd63-KH induced innate immune responses characterized by an interferon signature and the presence of activated dendritic cells. Broad and quantitatively robust CD8+ T cell responses were induced by vaccination in 100% (20/20) of vaccinated subjects.

CONCLUSION

The results of this study support the further development of ChAd63-KH as a novel third generation vaccine for VL and PKDL.

TRIAL REGISTRATION

This clinical trial (LEISH1) was registered at EudraCT (2012-005596-14) and ISRCTN (07766359).

Leishmania donovani Nucleoside Hydrolase (NH36) Domains Induce T-Cell Cytokine Responses in Human Visceral Leishmaniasis

Development of immunoprotection against visceral leishmaniasis (VL) focused on the identification of antigens capable of inducing a Th1 immune response. Alternatively, antigens targeting the CD8 and T-regulatory responses are also relevant in VL pathogenesis and worthy of being included in a preventive human vaccine. We assessed in active and cured patients and VL asymptomatic subjects the clinical signs and cytokine responses to the Leishmania donovani nucleoside hydrolase NH36 antigen and its N-(F1), central (F2) and C-terminal (F3) domains. As markers of VL resistance, the F2 induced the highest levels of IFN-γ, IL-1β, and TNF-α and, together with F1, the strongest secretion of IL-17, IL-6, and IL-10 in DTH+ and cured subjects. F2 also promoted the highest frequencies of CD3+CD4+IL-2+TNF-α-IFN-γ-, CD3+CD4+IL-2+TNF-α+IFN-γ-, CD3+CD4+IL-2+TNF-α-IFN-γ+, and CD3+CD4+IL-2+TNF-α+IFN-γ+ T cells in cured and asymptomatic subjects. Consistent with this, the IFN-γ increase was correlated with decreased spleen (R = -0.428, P = 0.05) and liver sizes (R = -0.428, P = 0.05) and with increased hematocrit counts (R = 0.532, P = 0.015) in response to F1 domain, and with increased hematocrit (R = 0.512, P 0.02) and hemoglobin counts (R = 0.434, P = 0.05) in response to F2. Additionally, IL-17 increases were associated with decreased spleen and liver sizes in response to F1 (R = -0.595, P = 0.005) and F2 (R = -0.462, P = 0.04). Conversely, F1 and F3 increased the CD3+CD8+IL-2+TNF-α-IFN-γ-, CD3+CD8+IL-2+TNF-α+IFN-γ-, and CD3+CD8+IL-2+TNF-α+IFN-γ+ T cell frequencies of VL patients correlated with increased spleen and liver sizes and decreased hemoglobin and hematocrit values. Therefore, cure and acquired resistance to VL correlate with the CD4+-Th1 and Th-17 T-cell responses to F2 and F1 domains. Clinical VL outcomes, by contrast, correlate with CD8+ T-cell responses against F3 and F1, potentially involved in control of the early infection. The in silico-predicted NH36 epitopes are conserved and bind to many HL-DR and HLA and B allotypes. No human vaccine against Leishmania is available thus far. In this investigation, we identified the NH36 domains and epitopes that induce CD4+ and CD8+ T cell responses, which could be used to potentiate a human universal T-epitope vaccine against leishmaniasis.

A Chimera Containing CD4+ and CD8+ T-Cell Epitopes of the Leishmania donovani Nucleoside Hydrolase (NH36) Optimizes Cross-Protection against Leishmania amazonesis Infection

The Leishmania donovani nucleoside hydrolase (NH36) and NH A34480 of Leishmania amazonensis share 93% of sequence identity. In mice, the NH36 induced protection against visceral leishmaniasis is mediated by a CD4+ T cell response against its C-terminal domain (F3). Besides this CD4+ Th1 response, prevention and cure of L. amazonensis infection require also additional CD8+ and regulatory T-cell responses to the NH36 N-terminal (F1 domain). We investigated if mice vaccination with F1 and F3 domains cloned in tandem, in a recombinant chimera, with saponin, optimizes the vaccine efficacy against L. amazonensis infection above the levels promoted by the two admixed domains or by each domain independently. The chimera induced the highest IgA, IgG, and IgG2a anti-NH36 antibody, IDR, IFN-γ, and IL-10 responses, while TNF-α was more secreted by mice vaccinated with F3 or all F3-contaning vaccines. Additionally, the chimera and the F1 vaccine also induced the highest proportions of CD4+ and CD8+ T cells secreting IL-2, TNF-α, or IFN-γ alone, TNF-α in combination with IL-2 or IFN-γ, and of CD4+ multifunctional cells secreting IL-2, TNF-α, and IFN-γ. Correlating with the immunological results, the strongest reductions of skin lesions sizes were determined by the admixed domains (80%) and by the chimera (84%), which also promoted the most pronounced and significant reduction of the parasite load (99.8%). Thus, the epitope presentation in a recombinant chimera optimizes immunogenicity and efficacy above the levels induced by the independent or admixed F1 and F3 domains. The multiparameter analysis disclosed that the Th1-CD4+ T helper response induced by the chimera is mainly directed against its FRYPRPKHCHTQVA epitope. Additionally, the YPPEFKTKL epitope of F1 induced the second most important CD4+ T cell response, and, followed by the DVAGIVGVPVAAGCT, FMLQILDFYTKVYE, and ELLAITTVVGNQ sequences, also the most potent CD8+ T cell responses and IL-10 secretion. Remarkably, the YPPEFKTKL epitope shows high amino acid identity with a multipotent PADRE sequence and stimulates simultaneously the CD4+, CD8+ T cell, and a probable T regulatory response. With this approach, we advanced in the design of a NH36 polytope vaccine capable of inducing cross-protection to cutaneous leishmaniasis.

A vaccine composed of a hypothetical protein and the eukaryotic initiation factor 5a from Leishmania braziliensis cross-protection against Leishmania amazonensis infection

In the present study, two proteins cloned from Leishmania braziliensis species, a hypothetical protein (LbHyp) and the eukaryotic initiation factor 5a (EiF5a), were evaluated to protect BALB/c mice against L. amazonensis infection. The animals were immunized with the antigens, either separately or in combination, using saponin as an immune adjuvant in both cases. Spleen cells from vaccinated and later infected mice produced significantly higher levels of protein and parasite-specific IFN-γ, IL-12, and GM-CSF, in addition to low levels of IL-4 and IL-10. Evaluating the parasite load by means of a limiting dilution technique and quantitative Real-Time PCR, vaccinated animals presented significant reductions in the parasite load in both infected tissues and organs, as well as lower footpad swelling, when compared to the control (saline and saponin) groups. The best results regarding the protection of the animals were achieved when the combined vaccine was administered into the animals. Protection was associated with an IFN-γ production against parasite antigens, which was mediated by both CD4+ and CD8+ T cells and correlated with antileishmanial nitrite production. In conclusion, data from the present study show that this polyprotein vaccine, which combines two L. braziliensis proteins, can induce protection against L. amazonensis infection.

The importance of nucleoside hydrolase enzyme (NH) in studies to treatment of Leishmania: A review

Leishmania is a genus of trypanosomes, which are responsible for leishmaniasis disease, a major trypanosome infection in humans. In recent years, published studies have shown that the search for new drugs for Leishmania treatments has intensified. Through technique modeling it has been possible to develop new compounds, which act as nucleoside hydrolase (NH) inhibitors. The effect of these enzymes is the hydrolysis of certain RNA nucleotides, which include uridine and inosine, necessary for the protozoa to transform certain nucleosides obtained from infected individuals into nucleobases for the preparation of their DNA. The obtention of NH inhibitors is very important to eliminate leishmaniasis disease in infected individuals. The aim of this study is to discuss the research and development of new agents for the treatment of Leishmania, and to stimulate the formulation of new NH inhibitors.

Expression and purification of an engineered, yeast-expressed Leishmania donovani nucleoside hydrolase with immunogenic properties

Leishmania donovani is the major cause of visceral leishmaniasis (kala-azar), now recognized as the parasitic disease with the highest level of mortality second only to malaria. No human vaccine is currently available. A 36 kDa L. donovani nucleoside hydrolase (LdNH36) surface protein has been previously identified as a potential vaccine candidate antigen. Here we present data on the expression of LdNH36 in Pichia pastoris and its purification at the 20 L scale to establish suitability for future pilot scale manufacturing. To improve efficiency of process development and ensure reproducibility, 4 N-linked glycosylation sites shown to contribute to heterogeneous high-mannose glycosylation were mutated to glutamine residues. The mutant LdNH36 (LdNH36-dg2) was expressed and purified to homogeneity. Size exclusion chromatography and light scattering demonstrated that LdNH36-dg2 existed as a tetramer in solution, similar to the wild-type recombinant L. major nucleoside hydrolase. The amino acid mutations do not affect the tetrameric interface as confirmed by theoretical modeling, and the mutated amino acids are located outside the major immunogenic domain. Immunogenic properties of the LdNH36-dg2 recombinant protein were evaluated in BALB/c mice using formulations that included a synthetic CpG oligodeoxynucleotide, together with a microparticle delivery platform (poly(lactic-co-glycolic acid)). Mice exhibited high levels of IgG1, IgG2a, and IgG2b antibodies that were reactive to both LdNH36-dg2 and LdNH36 wild-type. While the point mutations did affect the hydrolase activity of the enzyme, the IgG antibodies elicited by LdNH36-dg2 were shown to inhibit the hydrolase activity of the wild-type LdNH36. The results indicate that LdNH36-dg2 as expressed in and purified from P. pastoris is suitable for further scale-up, manufacturing, and testing in support of future first-in-humans phase 1 clinical trials.

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.

Immucillins ImmA and ImmH Are Effective and Non-toxic in the Treatment of Experimental Visceral Leishmaniasis

BACKGROUND

Immucillins ImmA (IA), ImmH (IH) and SerMe-ImmH (SMIH) are synthetic deazapurine nucleoside analogues that inhibit Leishmania (L.) infantum chagasi and Leishmania (L.) amazonensis multiplication in vitro without macrophage toxicity. Immucillins are compared to the Glucantime standard drug in the chemotherapy of Leishmania (L.) infantum chagasi infection in mice and hamsters. These agents are tested for toxicity and immune system response.

METHODOLOGY/PRINCIPAL FINDINGS

BALB/c mice were infected with 107 amastigotes, treated with IA, IH, SMIH or Glucantime (2.5mg/kg/day) and monitored for clinical variables, parasite load, antibody levels and splenocyte IFN-γ, TNF-α, and IL-10 expression. Cytokines and CD4+, CD8+ and CD19+ lymphocyte frequencies were assessed in uninfected controls and in response to immucillins. Urea, creatinine, GOT and GPT levels were monitored in sera. Anti-Leishmania-specific IgG1 antibodies (anti-NH36) increased in untreated animals. IgG2a response, high levels of IFN-γ, TNF-α and lower levels of IL-10 were detected in mice treated with the immucillins and Glucantime. Immucillins permitted normal weight gain, prevented hepato-splenomegaly and cleared the parasite infection (85-89%) without renal and hepatic toxicity. Immucillins promoted 35% lower secretion of IFN-γ in uninfected controls than in infected mice. IA and IH increased the CD4+ T and CD19+ B cell frequencies. SMIH increased only the proportion of CD-19 B cells. IA and IH also cured infected hamsters with lower toxicity than Glucantime.

CONCLUSIONS/SIGNIFICANCE

Immucillins IA, IH and SMIH were effective in treating leishmaniasis in mice. In hamsters, IA and IH were also effective. The highest therapeutic efficacy was obtained with IA, possibly due to its induction of a TH1 immune response. Low immucillin doses were required and showed no toxicity. Our results disclose the potential use of IA and IH in the therapy of visceral leishmaniasis.

Immunity to visceral leishmaniasis: implications for immunotherapy

Visceral leishmaniasis, caused by Leishmania donovani, L. infantum (syn. Leishmania chagasi), is a globally widespread disease with a burden of about 400,000 new infections reported annually. It is the most dangerous form of human leishmaniasis in terms of mortality and morbidity and is spreading to several nonendemic areas because of migration, global traveling and military conflicts. The emergence of Leishmania-HIV co-infection and increased prevalence of drug-resistant strains have worsened the impact of the disease. The traditional low-cost drugs are often toxic with several adverse effects, highlighting the need for development of new therapeutic and prophylactic strategies. Therefore, a detailed understanding of mechanisms of protective immunity is extremely important in order to develop new therapeutics in the form of vaccines or immunotherapies. This review gives an overview of visceral leishmaniasis, with particular emphasis on the innate and adaptive immune responses, vaccine and vaccination strategies and their potentials for immunotherapy against the disease.

Vaccines for visceral leishmaniasis: A review

Visceral leishmaniasis, which is also known as Kala-Azar, is one of the most severely neglected tropical diseases recognized by the World Health Organization (WHO). The threat of this debilitating disease continues due to unavailability of promising drug therapy or human vaccine. An extensive research is undergoing to develop a promising vaccine to prevent this devastating disease. In this review we compiled the findings of recent research with a view to facilitate knowledge on experimental vaccinology for visceral leishmaniasis. Various killed or attenuated parasite based first generation vaccines, second generation vaccines based on antigenic protein or recombinant protein, and third generation vaccines derived from antigen-encoding DNA plasmids including heterologous prime-boost Leishmania vaccine have been examined for control and prevention of visceral leishmaniasis. Vaccines based on recombinant protein and antigen-encoding DNA plasmids have given promising results and few vaccines including Leishmune®, Leishtec, and CaniLeish® have been licensed for canine visceral leishmaniasis. A systematic investigation of these vaccine candidates can lead to development of promising vaccine for human visceral leishmaniasis, most probably in the near future.

Visceral Leishmaniasis: Advancements in Vaccine Development via Classical and Molecular Approaches

Visceral leishmaniasis (VL) or kala-azar, a vector-borne protozoan disease, shows endemicity in larger areas of the tropical, subtropical and the Mediterranean countries. WHO report suggested that an annual incidence of VL is nearly 200,000 to 400,000 cases, resulting in 20,000 to 30,000 deaths per year. Treatment with available anti-leishmanial drugs are not cost effective, with varied efficacies and higher relapse rate, which poses a major challenge to current kala-azar control program in Indian subcontinent. Therefore, a vaccine against VL is imperative and knowing the fact that recovered individuals developed lifelong immunity against re-infection, it is feasible. Vaccine development program, though time taking, has recently gained momentum with the emergence of omic era, i.e., from genomics to immunomics. Classical as well as molecular methodologies have been overtaken with alternative strategies wherein proteomics based knowledge combined with computational techniques (immunoinformatics) speed up the identification and detailed characterization of new antigens for potential vaccine candidates. This may eventually help in the designing of polyvalent synthetic and recombinant chimeric vaccines as an effective intervention measures to control the disease in endemic areas. This review focuses on such newer approaches being utilized for vaccine development against VL.

Leishmania donovani Nucleoside Hydrolase Terminal Domains in Cross-Protective Immunotherapy Against Leishmania amazonensis Murine Infection

Nucleoside hydrolases of the Leishmania genus are vital enzymes for the replication of the DNA and conserved phylogenetic markers of the parasites. Leishmania donovani nucleoside hydrolase (NH36) induced a main CD4(+) T cell driven protective response against L. chagasi infection in mice which is directed against its C-terminal domain. In this study, we used the three recombinant domains of NH36: N-terminal domain (F1, amino acids 1-103), central domain (F2 aminoacids 104-198), and C-terminal domain (F3 amino acids 199-314) in combination with saponin and assayed their immunotherapeutic effect on Balb/c mice previously infected with L. amazonensis. We identified that the F1 and F3 peptides determined strong cross-immunotherapeutic effects, reducing the size of footpad lesions to 48 and 64%, and the parasite load in footpads to 82.6 and 81%, respectively. The F3 peptide induced the strongest anti-NH36 antibody response and intradermal response (IDR) against L. amazonenis and a high secretion of IFN-γ and TNF-α with reduced levels of IL-10. The F1 vaccine, induced similar increases of IgG2b antibodies and IFN-γ and TNF-α levels, but no IDR and no reduction of IL-10. The multiparameter flow cytometry analysis was used to assess the immune response after immunotherapy and disclosed that the degree of the immunotherapeutic effect is predicted by the frequencies of the CD4(+) and CD8(+) T cells producing IL-2 or TNF-α or both. Total frequencies and frequencies of double-cytokine CD4 T cell producers were enhanced by F1 and F3 vaccines. Collectively, our multifunctional analysis disclosed that immunotherapeutic protection improved as the CD4 responses progressed from 1+ to 2+, in the case of the F1 and F3 vaccines, and as the CD8 responses changed qualitatively from 1+ to 3+, mainly in the case of the F1 vaccine, providing new correlates of immunotherapeutic protection against cutaneous leishmaniasis in mice based on T-helper TH1 and CD8(+) mediated immune responses.

Cross-Protective Immunity to Leishmania amazonensis is Mediated by CD4+ and CD8+ Epitopes of Leishmania donovani Nucleoside Hydrolase Terminal Domains

The nucleoside hydrolase (NH) of Leishmania donovani (NH36) is a phylogenetic marker of high homology among Leishmania parasites. In mice and dog vaccination, NH36 induces a CD4+ T cell-driven protective response against Leishmania chagasi infection directed against its C-terminal domain (F3). The C-terminal and N-terminal domain vaccines also decreased the footpad lesion caused by Leishmania amazonensis. We studied the basis of the crossed immune response using recombinant generated peptides covering the whole NH36 sequence and saponin for mice prophylaxis against L. amazonensis. The F1 (amino acids 1-103) and F3 peptide (amino acids 199-314) vaccines enhanced the IgG and IgG2a anti-NH36 antibodies to similar levels. The F3 vaccine induced the strongest DTH response, the highest proportions of NH36-specific CD4+ and CD8+ T cells after challenge and the highest expression of IFN-γ and TNF-α. The F1 vaccine, on the other hand, induced a weaker but significant DTH response and a mild enhancement of IFN-γ and TNF-α levels. The in vivo depletion with anti-CD4 or CD8 monoclonal antibodies disclosed that cross-protection against L. amazonensis infection was mediated by a CD4+ T cell response directed against the C-terminal domain (75% of reduction of the size of footpad lesion) followed by a CD8+ T cell response against the N-terminal domain of NH36 (57% of reduction of footpad lesions). Both vaccines were capable of inducing long-term cross-immunity. The amino acid sequence of NH36 showed 93% identity to the sequence of the NH A34480 of L. amazonensis, which also showed the presence of completely conserved predicted epitopes for CD4+ and CD8+ T cells in F1 domain, and of CD4+ epitopes differing by a single amino acid, in F1 and F3 domains. The identification of the C-terminal and N-terminal domains as the targets of the immune response to NH36 in the model of L. amazonensis infection represents a basis for the rationale development of a bivalent vaccine against leishmaniasis.

Vaccines to prevent leishmaniasis

Leishmaniasis is a parasitic disease that encompasses a range of clinical manifestations affecting people in tropical and subtropical regions of the world. Epidemiological and experimental data indicate that protection from disease can be achieved in most people. In addition, we know how the host immune system must respond to infection in order to control parasite growth. However, there is still no vaccine for use in humans. Here, we review our understanding of host immunity following Leishmania infection and also discuss recent advances in the development of vaccines to prevent leishmaniasis, highlighting a new promising approach that targets the parasite hemoglobin receptor.

Experimental models in vaccine research: malaria and leishmaniasis

Animal models have a long history of being useful tools, not only to test and select vaccines, but also to help understand the elaborate details of the immune response that follows infection. Different models have been extensively used to investigate putative immunological correlates of protection against parasitic diseases that are important to reach a successful vaccine. The greatest challenge has been the improvement and adaptation of these models to reflect the reality of human disease and the screening of vaccine candidates capable of overcoming the challenge of natural transmission. This review will discuss the advantages and challenges of using experimental animal models for vaccine development and how the knowledge achieved can be extrapolated to human disease by looking into two important parasitic diseases: malaria and leishmaniasis.

DNA Vaccines against Protozoan Parasites: Advances and Challenges

Over the past 15 years, DNA vaccines have gone from a scientific curiosity to one of the most dynamic research field and may offer new alternatives for the control of parasitic diseases such as leishmaniasis and Chagas disease. We review here some of the advances and challenges for the development of DNA vaccines against these diseases. Many studies have validated the concept of using DNA vaccines for both protection and therapy against these protozoan parasites in a variety of mouse models. The challenge now is to translate what has been achieved in these models into veterinary or human vaccines of comparable efficacy. Also, genome-mining and new antigen discovery strategies may provide new tools for a more rational search of novel vaccine candidates.

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.

Immunotherapy as a strategy for treatment of leishmaniasis: a review of the literature

Leishmaniasis occurs as a spectrum of clinical syndromes divided into cutaneous, mucocutaneous and visceral forms. The epidemiology and clinical features are highly variable owing to the interplay of many factors ranging from parasite species and strains, vectors, host genetics and environment. Currently, there is no effective licensed vaccine for use in humans against leishmaniasis. Most traditional and low-cost treatment options, particularly in poor and endemic areas, are toxic with many adverse reactions and they require a long course of administration. The use of more effective, less toxic drugs is limited because total treatment cost is very high (expensive) and there are fears of development of drug resistance. Recent studies indicate that certain strategies aimed at modulating the host immune response (collectively called immunotherapy) could result in prophylactic and/or therapeutic cure of leishmaniasis under both laboratory and field conditions. In this review, we focus on treatment of leishmaniasis with a particular emphasis on immunotherapy/immunochemotherapy as an alternative to conventional drug treatment.

Adaptive immunity against Leishmania nucleoside hydrolase maps its c-terminal domain as the target of the CD4+ T cell-driven protective response

Nucleoside hydrolases (NHs) show homology among parasite protozoa, fungi and bacteria. They are vital protagonists in the establishment of early infection and, therefore, are excellent candidates for the pathogen recognition by adaptive immune responses. Immune protection against NHs would prevent disease at the early infection of several pathogens. We have identified the domain of the NH of L. donovani (NH36) responsible for its immunogenicity and protective efficacy against murine visceral leishmaniasis (VL). Using recombinant generated peptides covering the whole NH36 sequence and saponin we demonstrate that protection against L. chagasi is related to its C-terminal domain (amino-acids 199-314) and is mediated mainly by a CD4+ T cell driven response with a lower contribution of CD8+ T cells. Immunization with this peptide exceeds in 36.73±12.33% the protective response induced by the cognate NH36 protein. Increases in IgM, IgG2a, IgG1 and IgG2b antibodies, CD4+ T cell proportions, IFN-γ secretion, ratios of IFN-γ/IL-10 producing CD4+ and CD8+ T cells and percents of antibody binding inhibition by synthetic predicted epitopes were detected in F3 vaccinated mice. The increases in DTH and in ratios of TNFα/IL-10 CD4+ producing cells were however the strong correlates of protection which was confirmed by in vivo depletion with monoclonal antibodies, algorithm predicted CD4 and CD8 epitopes and a pronounced decrease in parasite load (90.5-88.23%; p = 0.011) that was long-lasting. No decrease in parasite load was detected after vaccination with the N-domain of NH36, in spite of the induction of IFN-γ/IL-10 expression by CD4+ T cells after challenge. Both peptides reduced the size of footpad lesions, but only the C-domain reduced the parasite load of mice challenged with L. amazonensis. The identification of the target of the immune response to NH36 represents a basis for the rationale development of a bivalent vaccine against leishmaniasis and for multivalent vaccines against NHs-dependent pathogens.

Selection and identification of malaria vaccine target molecule using bioinformatics and DNA vaccination

Following a genome-wide search for a blood stage malaria DNA-based vaccine using web-based bioinformatic tools, 29 genes from the annotated Plasmodium yoelii genome sequence (www.PlasmoDB.org and www.tigr.org) were identified as encoding GPI-anchored proteins. Target genes were those with orthologues in P. falciparum, containing an N-terminal signal sequence containing hydrophobic amino acid stretch and signal P criteria, a transmembrane-like domain and GPI anchor motif. Focusing on the blood stage, we extracted mRNA from pRBCs, PCR-amplified 22 out of the 29 selected genes, and eventually cloned nine of these into a DNA vaccine plasmid, pVAX 200-DEST. Biojector-mediated delivery of the nine DNA vaccines was conducted using ShimaJET to C57BL/6 mice at a dose of 4 μg/mouse three times at an interval of 3 weeks. Two weeks after the second booster, immunized mice were challenged with P. y. yoelii 17XL-parasitized RBCs and the level of parasitaemia, protection and survival was assessed. Immunization with one gene (PY03470) resulted in 2-4 days of delayed onset and level of parasitaemia and was associated with increased survival compared to non-immunized mice. Antibody production was, however, low following DNA vaccination, as determined by immunofluorescence assay. Recombinant protein from this gene, GPI8p transamidase-related protein (rPyTAM) in PBS or emulsified with GERBU adjuvant was also used to immunize another set of C57BL/6 mice with 10-20 μg/mouse three times at 3-week interval. Higher antibody response was obtained as determined by ELISA with similar protective effects as observed after DNA vaccination.

DNA vaccines: a rational design against parasitic diseases

Parasitic diseases are one of the most devastating causes of morbidity and mortality worldwide. Although immunization against these infections would be an ideal solution, the development of effective vaccines has been hampered by specific challenges posed by parasitic pathogens. Plasmid-based DNA vaccines may prove to be promising immunization tools in this area because vectors can be designed to integrate several antigens from different stages of the parasite life cycle or different subspecies; vaccines, formulations and immunization protocols can be tuned to match the immune response that offers protective immunity; and DNA vaccination is an affordable platform for developing countries. Partial and full protective immunity have been reported following DNA vaccination against the most significant parasitic diseases in the world.

Vaccine development against Trypanosoma cruzi and Leishmania species in the post-genomic era

Trypanosoma cruzi and the genus Leishmania are protozoan parasites causing diseases of major public health importance, and the recent completion of the sequencing of their genomes has opened new opportunities to further our understanding of the mechanisms required for protection and the development of vaccines. For example, trans-sialidases, one of the largest protein families from T. cruzi, contain dominant CD8+ T cell epitopes, and their use as preventive or therapeutic vaccines in different animal models has provided encouraging results. A much wider range of antigens and vaccine formulations have been tested against Leishmania, and new correlates for protection are being defined, such as the induction of multifunctional Th1 effector cells capable of producing a complex set of cytokines. Also, while a large number of these vaccine candidates have been rather successful in mouse models, their usefulness in more relevant animal models is still poor, in spite of significant immunogenicity. Novel proteomics and genomics approaches are being used for antigen discovery and the identification of new vaccine candidates, some of which have shown promise for the control of infection. These studies cast little doubt that T. cruzi and Leishmania genomes represent major resources for understanding key aspects of the mechanisms of immune protection against these parasites, and the increasing use of these tools will greatly impact vaccine development.

Leishmania infantum sterol 24-c-methyltransferase formulated with MPL-SE induces cross-protection against L. major infection

The enzyme sterol 24-c-methyltranferase (SMT) is required for the biosynthesis of ergosterol, the major membrane sterol in Leishmania parasites. SMT and ergosterol are not found in mammals, so this protein may be an attractive target for anti-leishmanial vaccines and drugs. We have previously demonstrated that SMT from L. infantum, which causes visceral leishmaniasis, is a protective antigen against this parasite. Because this protein is highly conserved among Leishmania species, we evaluated the potential of SMT to cross-protect against a different form of leishmaniasis. Here, we show that immunization with L. infantum SMT, formulated with monophosphoryl lipid A in stable emulsion (MPL-SE), protects mice from cutaneous leishmaniasis caused by L. major. In BALB/c mice the vaccine preparation induced antigen-specific multi-functional CD4(+) T cells capable of producing IFN-gamma, IL-2, and/or TNF-alpha upon antigen re-exposure, and MPL-SE was indispensable to direct immune responses to SMT towards Th1. Mice immunized with the SMT/MPL-SE vaccine developed significantly smaller lesions following ear challenge with L. major. These results suggest that SMT is a promising vaccine antigen for multiple forms of leishmaniasis.

Recent developments in leishmaniasis vaccine delivery systems

BACKGROUND

The observation that recovery from infection with Leishmania confers immunity to reinfection suggests that control of leishmaniasis by vaccination may be possible. New generation vaccines, particularly those based on recombinant proteins and DNA, are found to be less immunogenic.

OBJECTIVE

There is an urgent need for the development of new and improved vaccine adjuvants.

METHODS

Based on their principal mechanisms of action, adjuvants can be broadly separated into two classes: immunostimulatory adjuvants and vaccine delivery systems. Vaccine delivery systems can carry both antigen and adjuvant for effective delivery to the antigen-presenting cells (APCs). In this article, we review the adjuvants, the delivery systems and their combinations used in the search of an effective vaccine against leishmaniasis.

CONCLUSION

Based on current knowledge, cationic liposomes appear to have better prospects as effective delivery systems for developing a vaccine for leishmaniasis.

FML vaccine against canine visceral leishmaniasis: from second-generation to synthetic vaccine

The Leishmania donovani glycoprotein fraction, known as FML, successfully underwent preclinical and clinical (Phase I-III) vaccine trials against canine visceral leishmaniasis (92-95% of protection and 76-80% of vaccine efficacy) when formulated with a QS21 saponin-containing adjuvant. It became the licensed Leishmune vaccine for canine prophylaxis in Brazil. The immune response raised by the vaccine is long lasting, immunotherapeutic and reduces dog infectivity blocking the transmission of the disease, as revealed by an in vivo assay. The preliminary epidemiological control data of vaccinated areas in Brazil indicate that, in spite of the still low vaccine coverage, there was a significant decrease in the incidence of the human and canine disease. A 36-kDa glycoprotein, in the FML complex, is the human marker of the disease, which was protective in mice as native recombinant protein or DNA vaccine. The DNA vaccine is now being tested against the canine disease. This review resumes the development of the second-generation FML-saponin-Leishmune vaccine, its adjuvant and of the NH36 DNA vaccine, toward the identification of its major epitopes that might be included in a possible future synthetic vaccine.

Vaccines for leishmaniasis in the fore coming 25 years

Human vaccination against leishmaniasis using live Leishmania was used in Middle East and Russia (1941-1980). First-generation vaccines, composed by killed parasites induce low efficacies (54%) and were tested in humans and dogs Phase III trials in Asia and South America since 1940. Second-generation vaccines using live genetically modified parasites, or bacteria or viruses containing Leishmania genes, recombinant or native fractions are known since the 1990s. Due to the loss of PAMPs, the use of adjuvants increased vaccine efficacies of the purified antigens to 82%, in Phase III dog trials. Recombinant second-generation vaccines and third-generation DNA vaccines showed average values of parasite load reduction of 68% and 59% in laboratory animal models, respectively, but their success in field trials had not yet been reported. This review is focused on vaccine candidates that show any efficacy against leishmaniasis and that are already in different phase trials. A lot of interest though was generated in recent years, by the studies going on in experimental models. The promising candidates may find a place in the forth coming years. Among them most probably are the multiple-gene DNA vaccines that are stable and do not require cold-chain transportation. In the mean time, second-generation vaccines with native antigens and effective adjuvants are likely to be licensed and used in Public Health control programs in the fore coming 25 years. To date, only three vaccines have been licensed for use: one live vaccine for humans in Uzbekistan, one killed vaccine for human immunotherapy in Brazil and a second-generation vaccine for dog prophylaxis in Brazil.

Leishmanial antigens in liposomes promote protective immunity and provide immunotherapy against visceral leishmaniasis via polarized Th1 response

Leishmaniasis affects 12 million people, and it is generally agreed that vaccination provides the best long-term strategy for its control. An ideal vaccine should be effective in both preventing and treating leishmaniasis. However, immunological correlates to predict vaccine efficacy and success of treatment in visceral leishmaniasis (VL) remain ill defined. Here, we correlated the vaccine efficacy of soluble leishmanial antigens (SLA) from Leishmania donovani promastigote membrane, entrapped in negative, neutral and positively charged liposomes with the elicited immune responses to predict vaccine success in experimental VL. Production of both IFN-gamma and IL-4 with a dominance of Th1 response following immunization was required for optimum success against L. donovani infection in BALB/c mice. The best vaccine formulation, SLA in positively charged liposomes, was then used for immunotherapy. This vaccine induced more than 90% elimination of parasites from both liver and spleen. The success of immunotherapy exhibited an immune modulation with surge in Th1 cytokines, IFN-gamma and IL-12 with extreme down regulation of disease promoting IL-4 and IL-10. These findings suggest that an immune modulation towards Th1 is effective for both successful vaccination and immunotherapy.

Natural history and surgical treatment of brown tumor lesions at various sites in refractory primary hyperparathyroidism

OBJECTIVE

Nowadays, the occurrence of brown tumor lesions or osteitis fibrosa cystica caused by long-lasting primary hyperparathyroidism are very rare, since measuring serum calcium became available routinely in the mid-1970s. It is a tumor-like lesion that may affect the entire skeleton, often presenting with diffuse focal bone pain or by pathological fracture.

METHODS

We describe our experience of brown tumor lesions at different skeletal sites that were treated at our trauma centre within the last two years. This included surgical therapy for the indications (i) pain at the pelvis, (ii) increased risk for pathological fracture at the tibia and (iii) acute radicular symptoms at the lumbar spine. The literature was reviewed for the current understanding of the pathophysiology as well as therapy of brown tumor lesions in primary hyperparathyroidism.

RESULTS

Curettage of a left-sided iliac crest brown tumor terminated focal pain. A less invasive stabilisation system and bone cement decreased both patient pain and the fracture risk of brown tumor lesion sites of the shinbone; and internal fixator including laminectomy at the lumbar spine ended radicular symptoms.

CONCLUSION

Patients with refractory primary hyperparathyroidism should be monitored closely by endocrinologists and the patient's serum calcium level should be adjusted as far as possible. Radiography is required only if focal bone pain or pathological fractures or radicular symptoms occur. Surgery should be considered if large bone defects with spontaneous fracture risk or increasing pain are present. Tumor curettage, Palacos plombage and less invasive stabilisation systems have proved to be acceptable surgical options.

Immunotherapy against experimental canine visceral leishmaniasis with the saponin enriched-Leishmune vaccine

In order to assess the immunotherapeutic potential on canine visceral leishmaniasis of the Leishmune^® vaccine, formulated with an increased adjuvant concentration (1 mg of saponin rather than 0.5 mg), 24 mongrel dogs were infected with Leishmania (L.) chagasi. The enriched-Leishmune^® vaccine was injected on month 6, 7 and 8 after infection, when animals were seropositive and symptomatic. The control group were injected with a saline solution. Leishmune^®-treated dogs showed significantly higher levels of anti-FML IgG antibodies (ANOVA; p < 0.0001), a higher and stable IgG2 and a decreasing IgG1 response, pointing to a TH1 T cell mediated response. The vaccine had the following effects: it led to more positive delayed type hypersensitivity reactions against Leishmania lysate in vaccinated dogs (75%) than in controls (50%), to a decreased average of CD4+ Leishmania-specific lymphocytes in saline controls (32.13%) that fell outside the 95% confidence interval of the vaccinees (41.62%, CI95% 43.93–49.80) and an increased average of the clinical scores from the saline controls (17.83) that falls outside the 95% confidence interval for the Leishmune^® immunotherapy-treated dogs (15.75, CI95% 13.97–17.53). All dogs that received the vaccine were clustered, and showed lower clinical scores and normal CD4+ counts, whereas 42% of the untreated dogs showed very diminished CD4+ and higher clinical score. The increase in clinical signs of the saline treated group was correlated with an increase in anti-FML antibodies (p < 0.0001), the parasitological evidence (p = 0.038) and a decrease in Leishmania-specific CD4+ lymphocyte proportions (p = 0.035). These results confirm the immunotherapeutic potential of the enriched-Leishmune^® vaccine. The vaccine reduced the clinical symptoms and evidence of parasite, modulating the outcome of the infection and the dog's potential infectiosity to phlebotomines. The enriched-Leishmune^® vaccine was subjected to a safety analysis and found to be well tolerated and safe.

Ethnoveterinary medicines used for ruminants in British Columbia, Canada

BACKGROUND

The use of medicinal plants is an option for livestock farmers who are not allowed to use allopathic drugs under certified organic programs or cannot afford to use allopathic drugs for minor health problems of livestock.

METHODS

In 2003 we conducted semi-structured interviews with 60 participants obtained using a purposive sample. Medicinal plants are used to treat a range of conditions. A draft manual prepared from the data was then evaluated by participants at a participatory workshop.

RESULTS

There are 128 plants used for ruminant health and diets, representing several plant families. The following plants are used for abscesses: Berberis aquifolium/Mahonia aquifolium Echinacea purpurea, Symphytum officinale, Bovista pila, Bovista plumbea, Achillea millefolium and Usnea longissima. Curcuma longa L., Salix scouleriana and Salix lucida are used for caprine arthritis and caprine arthritis encephalitis. Euphrasia officinalis and Matricaria chamomilla are used for eye problems. Wounds and injuries are treated with Bovista spp., Usnea longissima, Calendula officinalis, Arnica sp., Malva sp., Prunella vulgaris, Echinacea purpurea, Berberis aquifolium/Mahonia aquifolium, Achillea millefolium, Capsella bursa-pastoris, Hypericum perforatum, Lavandula officinalis, Symphytum officinale and Curcuma longa. Syzygium aromaticum and Pseudotsuga menziesii are used for coccidiosis. The following plants are used for diarrhea and scours: Plantago major, Calendula officinalis, Urtica dioica, Symphytum officinale, Pinus ponderosa, Potentilla pacifica, Althaea officinalis, Anethum graveolens, Salix alba and Ulmus fulva. Mastitis is treated with Achillea millefolium, Arctium lappa, Salix alba, Teucrium scorodonia and Galium aparine. Anethum graveolens and Rubus sp., are given for increased milk production. Taraxacum officinale, Zea mays, and Symphytum officinale are used for udder edema. Ketosis is treated with Gaultheria shallon, Vaccinium sp., and Symphytum officinale. Hedera helix and Alchemilla vulgaris are fed for retained placenta.

CONCLUSION

Some of the plants showing high levels of validity were Hedera helix for retained placenta and Euphrasia officinalis for eye problems. Plants with high validity for wounds and injuries included Hypericum perforatum, Malva parviflora and Prunella vulgaris. Treatments with high validity against endoparasites included those with Juniperus communis and Pinus ponderosa. Anxiety and pain are well treated with Melissa officinalis and Nepeta caesarea.