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

Elucidation of conserved multi-epitope vaccine against Leishmania donovani using reverse vaccinology

Visceral leishmaniasis (VL) is a tropical disease that causes severe public health problems in humans when untreated. As no licensed vaccine exists against VL, we aimed to formulate a potential MHC-restricted chimeric vaccine construct against this dreadful parasitic disease. Amastin-like protein derived from L. donovani is considered to be stable, immunogenic and non-allergic. A comprehensive established framework was used to explore the set of immunogenic epitopes with estimated population coverage of 96.08% worldwide. The rigorous assessment revealed 6 promiscuous T-epitopes which can plausibly be presented by more than 66 diverse HLA alleles. Further docking and simulation study of peptide receptor complexes identified a strong and stable binding interaction with better structural compactness. The predicted epitopes were combined with appropriate linkers and adjuvant molecules and their translation efficiency was evaluated in pET28+(a), an bacterial expression vector using in-silico cloning. Molecular docking followed by MD simulation study revealed a stable interaction between chimeric vaccine construct with TLRs. Immune simulation of the chimeric vaccine constructs showed an elevated Th1 immune response against both B and T epitopes. With this, the detailed computational analysis suggested that the chimeric vaccine construct can evoke a robust immune response against Leishmania donovani infection. Future studies are required to validate the role of amastin as a promising vaccine target.Communicated by Ramaswamy H. Sarma.

Intramuscular Immunization with a Liposomal Multi-Epitope Chimeric Protein Induces Strong Cellular Immune Responses against Visceral Leishmaniasis

Control of the intracellular parasite Leishmania (L.) requires the activation of strong type 1 cellular immune responses. Towards this goal, in the present study, a multiepitope chimeric protein named LiChimera was encapsulated into cationic liposomes and its protective efficacy against experimental visceral leishmaniasis was investigated. Liposomal LiChimera conferred significant protection against L. infantum as evidenced by the significantly reduced parasite loads in the spleen and liver. Protection detected in Lipo:LiChimera-immunized mice was dependent on the differentiation of long-lasting cellular immune responses and particularly the induction of antigen-specific multifunctional memory CD4+ TH1 and CD8+ T cells that persisted during infection, as evidenced by the persistent high production of IFN-γ and IL-2 and proliferation activity. Notably, protected mice were also characterized by significantly low numbers of non-regulatory CD4+ T cells able to co-produce IFN-γ and IL-10, an important population for disease establishment, as compared to non-immunized control group. Collectively, these results demonstrate that cationic liposomes containing LiChimera can be considered an effective candidate vaccine against visceral leishmaniasis.

Revealing a Novel Antigen Repressor of Differentiation Kinase 2 for Diagnosis of Human Visceral Leishmaniasis in India

Visceral leishmaniasis (VL) is one of the major global health concerns due to its association with morbidity and mortality. All available diagnostic tools have been, until now, unable to provide a very specific and cost-effective mode of detection for VL globally. Therefore, the design of robust, specific, and commercially translatable diagnostic tests is urgently required. Currently, we are attempting to identify and explore the diagnostic potential of a novel parasite antigen. Repressor of differentiation kinase 2 (RDK2), a serine/threonine kinase, has a versatile role in parasite life cycle progression. However, its role as a diagnostic candidate for VL has not been investigated. Herein, we cloned and over-expressed LdRDK2 and studied the recombinant RDK2 for the diagnosis of human VL using serum and urine samples. In silico analysis predicted that RDK2 is conserved among Leishmania species with the least conservation in humans. RDK2 developed immune-reactive bands with antibodies present in VL patients' sera, and it demonstrated no cross-reactivity with sera from healthy controls and other diseases. Additionally, RDK2 antigen demonstrated a significant reactivity with IgG antibodies of VL patients' sera, with 78% sensitivity and 86.67% specificity as compared to healthy controls and other diseases. Furthermore, we evaluated its utility for non-invasive diagnosis of VL using patients' urine samples and found 93.8% sensitivity and 85.7% specificity. RDK2 was found to have better sensitivity and treatment response in patients' urine compared to serum samples, indicating its role as a promising point of care (POC) antigen. In a nutshell, we explored the role of RDK2 as a potential diagnostic marker for VL in both invasive and non-invasive modes as well as its utility as a promising POC antigen for treatment response cases.

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.

A Phospholipase-A Activity in Soluble Leishmania Antigens Causes Instability of Liposomes

Aim:

This study aimed to investigate the existence of phospholipase-A (PLA) activity in Soluble L. major Antigens (SLA) because of no reports for it so far. Liposomes were used as sensors to evaluate PLA activity.

Objective:

Liposomal SLA consisting of Egg Phosphatidylcholine (EPC) or Sphingomyelin (SM) were prepared by two different methods in different pH or temperatures and characterized by Dynamic Light Scattering (DLS) and Thin Layer Chromatography (TLC).

Methods:

Lipid hydrolysis led to the disruption of EPC liposomal SLA in both methods but the Film Method (FM) produced more stable liposomes than the Detergent Removal Method (DRM).

Results:

The preparation of EPC liposomal SLA at pH 6 via FM protected liposomes from hydrolysis to some extent for a short time. EPC liposomes but not SM liposomes were disrupted in the presence of SLA.

Conclusion:

Therefore, a phospholipid without ester bond such as SM should be utilized in liposome formulations containing PLA as an encapsulating protein.

DDX3 DEAD-box RNA helicase (Hel67) gene disruption impairs infectivity of Leishmania donovani and induces protective immunity against visceral leishmaniasis

Visceral leishmaniasis (VL) is a vector-borne disease caused by the digenetic protozoan parasite Leishmania donovani complex. So far there is no effective vaccine available against VL. The DDX3 DEAD-box RNA Helicase (Hel67) is 67 kDa protein which is quite essential for RNA metabolism, amastigote differentiation, and infectivity in L. major and L. infantum. To investigate the role of Hel67 in the L. donovani, we created L. donovani deficient in the Hel67. Helicase67 null mutants (LdHel67^-/-) were not able to differentiate as axenic amastigotes and were unable to infect the hamster. So, we have analyzed the prophylactic efficacy of the LdHel67^-/- null mutant in hamsters. The LdHel67^-/- null mutant based candidate vaccine exhibited immunogenic response and a higher degree of protection against L. donovani in comparison to the infected control group. Further, the candidate vaccine displayed antigen-specific delayed-type hypersensitivity (DTH) as well as strong antibody response and NO production which strongly correlates to long term protection of candidate vaccine against the infection. This study confirms the potential of LdHel67^-/- null mutant as a safe and protective live attenuated vaccine candidate against visceral leishmaniasis.

Evaluation of Cysteine Protease C of Leishmania donovani in Comparison with Glycoprotein 63 and Elongation Factor 1α for Diagnosis of Human Visceral Leishmaniasis and for Posttreatment Follow-Up Response

Visceral leishmaniasis (VL) is a threat in many developing countries. Much effort has been put to eliminating this disease, for which serodiagnosis remains the mainstay for VL control programs. New and improved antigens as diagnostic candidates are required, though, as the available antigens fail to demonstrate equal optimum performance in all areas of endemicity. Moreover, these diagnoses are dependent on invasive serum sampling. In the current study, we cloned and expressed Leishmania donovani cysteine protease C (CPC) and evaluated its diagnostic and test-of-cure possibilities by detecting the antibody levels in human serum and urine through ELISA and immunoblot assays. Two immunodominant antigens, recombinant glycoprotein 63 (GP63) and elongation factor 1α (EF1α), identified earlier by our group, were also assessed by employing human serum and urine samples. Of these three antigens in ELISAs, CPC demonstrated the highest sensitivities of 98.15% and 96% positive testing in serum and urine of VL patients, respectively. Moreover, CPC yielded 100% specificity with serum and urine of nonendemic healthy controls compared to GP63 and EF1α. Urine samples were found to be more specific than serum for distinguishing endemic healthy controls and other diseases by means of all three antigens. In all cases, CPC gave the most promising results. Unlike serum, urine tests demonstrated a significant decrease in antibody levels for CPC, GP63, and EF1α after 6 months of treatment. The diagnostic and test-of-cure performances of CPC in the immunoblot assay were found to be better than those of GP63 and EF1α. In conclusion, CPC, followed by GP63 and EF1α, may be utilized as candidates for diagnosis of VL and to assess treatment response.

Investigation of the antigenicity and protective efficacy of Leishmania promastigote membrane antigens in search of potential diagnostic and vaccine candidates against visceral leishmaniasis

BACKGROUND

Visceral leishmaniasis (VL), is a parasitic disease that causes serious medical consequences if treatment is delayed. Despite a decline in the number of VL cases in the Indian subcontinent, the commencement of the disease in newer areas continues to be a major concern. Although serological diagnosis mainly by immunochromatographic tests has been found to be effective, a test of cure in different phases of treatment is still desired. Even though a good prophylactic response has been obtained in murine models by a number of vaccine candidates, few have been proposed for human use.

METHODS

In this study, nine antigenic components (31, 34, 36, 45, 51, 63, 72, 91 and 97 kDa) of Leishmania promastigote membrane antigens (LAg), were electroeluted and evaluated through ELISA to diagnose and distinguish active VL from one month cured and six months post-treatment patients. Further, to investigate the immunogenicity of electroeluted proteins, human PBMCs of cured VL patients were stimulated with 31, 34, 51, 63, 72 and 91 kDa proteins.

RESULTS

We found that 34 and 51 kDa proteins show 100% sensitivity and specificity with healthy controls and other diseases. After six months post-treatment, antibodies to 72 and 91 kDa antigens show a significant decline to almost normal levels. This suggests that 34 and 51 kDa proteins are efficient in diagnosis, whereas 72 and 91 kDa proteins may be used to monitor treatment outcome. In another assay, 51 and 63 kDa proteins demonstrated maximum ability to upregulate IFN-γ and IL-12 with minimum induction of IL-10 and TGF-β. The results indicating that 51 and 63 kDa proteins could be strong candidates for human immunization against VL. In contrast, 34 and 91 kDa proteins demonstrated a reverse profile and may not be a good vaccine candidate.

CONCLUSIONS

The preliminary data obtained in this study proposes the potential of some of the antigens in Leishmania diagnosis and for test of cure. Additionally, some antigens demonstrated good immunoprophylactic cytokine production through T cell-mediated immune response, suggesting future vaccine candidates for VL. However, further studies are necessary to explore these antigens in diagnosis and to access the long-term immune response.

Development of nano-carriers for Leishmania vaccine delivery

Introduction: Leishmaniasis is a neglected tropical infection caused by several species of intracellular protozoan parasites of the genus Leishmania. It is strongly believed that the development of vaccines is the most appropriate approach to control leishmaniasis. However, there is no vaccine available yet and the lack of an appropriate adjuvant delivery system is the main reason.Areas covered: Adjuvants are the utmost important part of a vaccine, to induce the immune response in the right direction. Limitations and drawbacks of conventional adjuvants have been necessitated the development of novel particulate delivery systems as adjuvants to obtain desirable protection against infectious diseases such as leishmaniasis. This review focused on particulate adjuvants especially nanoparticles that are in use to develop vaccines against leishmaniasis. The list of adjuvants includes generally lipids-, polymers-, or mineral-based delivery systems that target antigens specifically to the site of action within the host's body and enhance immune responses.Expert opinion: Over the past few years, there has been an increasing interest in developing particulate adjuvants as alternatives to immunostimulatory types. The composition of nano-carriers and particularly the physicochemical properties of nanoparticles have great potential to overcome challenges posed to leishmaniasis vaccine developments.

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.

Protection induced by Leishmania Major antigens and the imiquimod adjuvant encapsulated on liposomes in experimental cutaneous leishmaniasis

There is a need for new, effective, and less expensive and toxic treatment for Leishmaniasis. It seems that the use of a suitable adjuvant and a delivery system is effective in inducing immune reactions for protection. Liposomes can be applied as immunoadjuvants to trigger immune reactions to different antigens. The adjuvant effects of imiquimod using DSPC liposomes containing SLA (soluble Leishmania antigens) were studied on the type and intensity of the produced immune reaction to the challenge of Leishmania major in BALB/c mice. Liposomes were produced by the lipid film procedure. BALB/C mice were immunized subcutaneously, three times at 2-week intervals and with various formulations. Lesion development and the parasite burden in the spleens and feet after the challenge with Leishmania major, Th1 cytokine (IFN-γ), and the IgG isotype titration were assessed to evaluate the induced immune reaction and the protection level. The group of mice immunized with Liposome DSPC +Imiquimod +SLA revealed less severe footpad swelling, being significantly different (P < .05) from other groups. A higher level of IgG2a and IFN-γ secretion was observed in the mice immunized with Liposome DSPC +Imiquimod +SLA than the control group. These observations imply that the DSPC liposome containing imiquimod induces the Th1 immune response that is protective against the challenge of Leishmania major.

Evaluation of Lsa46 and Lsa77 Leptospiral Proteins for Their Immunoprotective Activities in Hamster Model of Leptospirosis

Leptospirosis is a neglected tropical disease caused by pathogenic Leptospira spp. The lack of an effective vaccine favors the increase of the disease. Currently, surface-exposed proteins are the main targets for the search of vaccine candidates. In this study, we examined whether the surface Lsa46 and Lsa77 proteins, previously identified as laminin and plasminogen binding proteins, have the capacity of inducing protection and sterilizing immunity against challenge with virulent Leptospira in hamster model. Animals were subcutaneously immunized with Lsa46, Lsa77, or a combination of both in Alum adjuvant and challenged intraperitoneally with L. interrogans serovar Kennewicki strain Pomona Fromm. Hamster immunization with Lsa46 or Lsa77 or both promoted a strong IgG response. Th2- and Th1-biased immune responses were observed when Lsa46 and Lsa77 were individually administered, respectively, as detected by the IgG1/IgG2/3 ratio. Immunized hamsters with the combined proteins induced a Th1-biased immune response. Although the immunization with Lsa46 and Lsa77 stimulated protective immunity with reduction of bacterial burden, when compared to animals individually immunized with the proteins, the data was not statistically significant. Thus, although promising, more studies are needed before the role of these proteins in stimulating sterilizing immunity in mammals is conclusively determined.

The role of MPL and imiquimod adjuvants in enhancement of immune response and protection in BALB/c mice immunized with soluble Leishmania antigen (SLA) encapsulated in nanoliposome

Adjuvants play an essential role in the induction of immunity against leishmaniasis. In this study, monophosphoryl lipid A (MPL) and imiquimod (IMQ) were used as TLR ligands adjuvants to enhance immunogenicity and rate of protection against leishmaniasis. Nanoliposomes containing soluble Leishmania antigens (SLA) and adjuvants were consisted of DSPC, DSPG and Chol prepared by using lipid film method followed by bath sonication. The size of nanoliposomes was around 95 nm and their zeta potential was negative. BALB/c mice were immunized by liposomal formulations of lip/SLA, lip/MPL/SLA, lip/IMQ/SLA, lip/MPL/IMQ/SLA, lip/SLA + lip/IMQ, lip/SLA + lip/MPL, lip/SLA + lip/MPL/IMQ and five controls of SLA, lip/MPL, lip/IMQ, lip/MPL/IMQ and buffer by subcutaneously (SC) injections, three times in 2 weeks intervals. The synergic effect of two adjuvants when they are used in one formulation showed significantly (p < .001) smaller footpad swelling and the lowest parasite burden in lymph node and foot after the challenge. IgG2a in these groups showed the higher titre compared to control groups, which is compatible with the high IFN-γ production and lowest IL-4. Taken together the results indicated that co-delivery of MPL and IMQ adjuvants and antigen in nanoliposome carrier could be an appropriate delivery system to induce cellular immunity pathway against leishmaniasis.

Liposomal Elongation Factor-1α Triggers Effector CD4 and CD8 T Cells for Induction of Long-Lasting Protective Immunity against Visceral Leishmaniasis

Despite advances, identification and formulation of safe and effective vaccine for long-lasting protection against leishmaniasis is still inadequate. In this study, we have identified a novel antigen, leishmanial elongation factor-1α (EF1-α), as an immunodominant component of solubilized leishmanial membrane antigens that reacts with visceral leishmaniasis (VL) sera and induces cellular proliferative and cytokine response in PBMCs of cured VL subjects. Leishmanial EF1-α is a 50 kDa antigen that plays a crucial role in pathogen survival by regulating oxidative burst in the host phagocytes. Previously, immunodominant truncated forms of EF1-α from different species of Leishmania have been reported. Formulation of the L. donovani 36 kDa truncated as well as the cloned recombinant EF1-α in cationic liposomes induce strong resistance to parasitic burden in liver and spleen of BALB/c mice through induction of DTH and a IL-10 and TGF-β suppressed mixed Th1/Th2 cytokine responses. Multiparametric analysis of splenocytes for generation of antigen-specific IFN-γ, IL2, and TNF-α producing lymphocytes indicate that cationic liposome facilitates expansion of both CD4⁺ as well as CD8⁺ memory and effector T cells. Liposomal EF1-α is a novel and potent vaccine formulation against VL that imparts long-term protective responses. Moreover, the flexibility of this formulation opens up the scope to combine additional adjuvants and epitope selected antigens for use in other disease forms also.

Liposomal vaccine formulations as prophylactic agents: design considerations for modern vaccines

Vaccinology is one of the most important cornerstones in modern medicine, providing better quality of life. The human immune system is composed of innate and adaptive immune processes that interplay when infection occurs. Innate immunity relies on pathogen-associated molecular patterns which are recognized by pathogen recognition receptors localized in antigen presenting cells. After antigen processing and presentation, CD4+ T cell polarization occurs, further leading to B cell and CD8+ activation and humoral and cell-mediated adaptive immune responses. Liposomes are being employed as vaccine technologies and their design is of importance to ensure proper immune responses. Physicochemical parameters like liposome size, charge, lamellarity and bilayer fluidity must be completely understood to ensure optimal vaccine stability and efficacy. Liposomal vaccines can be developed to target specific immune cell types for the induction of certain immune responses. In this review, we will present promising liposomal vaccine approaches for the treatment of important viral, bacterial, fungal and parasitic infections (including tuberculosis, TB). Cationic liposomes are the most studied liposome types due to their enhanced interaction with the negatively charged immune cells. Thus, a special section on the cationic lipid dimethyldioctadecylammonium and TB is also presented.

Antigenicity, immunogenicity and protective efficacy of a conserved Leishmania hypothetical protein against visceral leishmaniasis

In this study, a Leishmania hypothetical protein, LiHyS, was evaluated regarding its antigenicity, immunogenicity and protective efficacy against visceral leishmaniasis (VL). Regarding antigenicity, immunoblottings and an enzyme-linked immunosorbent assay using human and canine sera showed high sensitivity and specificity values for the recombinant protein (rLiHyS) in the diagnosis of VL. When evaluating the immunogenicity of LiHyS, which is possibly located in the parasite's flagellar pocket, proliferative assays using peripheral blood mononuclear cells from healthy subjects or VL patients showed a high proliferative index in both individuals, when compared to the results obtained using rA2 or unstimulated cultures. Later, rLiHyS/saponin was inoculated in BALB/c mice, which were then challenged with Leishmania infantum promastigotes. The vaccine induced an interferon-γ, interleukin (IL)-12 and granulocyte-macrophage colony-stimulating factor production, which was maintained after infection and which was associated with high nitrite and IgG2a antibody levels, as well as low IL-4 and IL-10 production. Significant reductions in the parasite load in liver, spleen, bone marrow and draining lymph nodes were found in these animals. In this context, the present study shows that the rLiHyS has the capacity to be evaluated as a diagnostic marker or vaccine candidate against VL.

Total Leishmania antigens with Poly(I:C) induce Th1 protective response

Our proposal was to develop a vaccine based on total Leishmania antigens (TLA) adjuvanted with polyinosinic-polycytidylic acid [Poly(I:C)] able to induce a Th1 response which can provide protection against Leishmania infection. Mice were vaccinated with two doses of TLA-Poly(I:C) administered by subcutaneous route at 3-week interval. Humoral and cellular immune responses induced by the immunization were measured. The protective efficacy of the vaccine was evaluated by challenging mice with infective promastigotes of Leishmania (Leishmania) amazonensis into the footpad. Mice vaccinated with TLA-Poly(I:C) showed a high anti-Leishmania IgG titre, as well as increased IgG1 and IgG2a subclass titres compared with mice vaccinated with the TLA alone. The high IgG2a indicated a Th1 bias response induced by the TLA-Poly(I:C) immunization. Accordingly, the cellular immune response elicited by the formulation was characterized by an increased production of IFN-γ and no significant production of IL-4. The TLA-Poly(I:C) immunization elicited good protection, which was associated with decreased footpad swelling, a lower parasite load and a reduced histopathological alteration in the footpad. Our findings demonstrate a promising vaccine against cutaneous leishmaniasis that is relatively economic and easy to develop and which should be taken into account for preventing leishmaniasis in developing countries.

Vaccination with poly(D,L-lactide-co-glycolide) nanoparticles loaded with soluble Leishmania antigens and modified with a TNFα-mimicking peptide or monophosphoryl lipid A confers protection against experimental visceral leishmaniasis

Visceral leishmaniasis (VL) persists as a major public health problem, and since the existing chemotherapy is far from satisfactory, development of an effective vaccine emerges as the most appropriate strategy for confronting VL. The development of an effective vaccine relies on the selection of the appropriate antigen and also the right adjuvant and/or delivery vehicle. In the present study, the protective efficacy of poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles (NPs), which were surface-modified with a TNFα-mimicking eight-amino-acid peptide (p8) and further functionalized by encapsulating soluble Leishmania infantum antigens (sLiAg) and monophosphoryl lipid A (MPLA), a TLR4 ligand, was evaluated against challenge with L. infantum parasites in BALB/c mice. Vaccination with these multifunctionalized PLGA nanoformulations conferred significant protection against parasite infection in vaccinated mice. In particular, vaccination with PLGA-sLiAg-MPLA or p8-PLGA-sLiAg NPs resulted in almost complete elimination of the parasite in the spleen for up to 4 months post-challenge. Parasite burden reduction was accompanied by antigen-specific humoral and cellular immune responses. Specifically, injection with PLGA-sLiAg-MPLA raised exclusively anti-sLiAg IgG1 antibodies post-vaccination, while in p8-PLGA-sLiAg-vaccinated mice, no antibody production was detected. However, 4 months post-challenge, in mice vaccinated with all the multifunctionalized NPs, antibody class switching towards IgG2a subtype was observed. The study of cellular immune responses revealed the increased proliferation capacity of spleen cells against sLiAg, consisting of IFNγ-producing CD4⁺ and CD8⁺ T cells. Importantly, the activation of CD8⁺ T cells was exclusively attributed to vaccination with PLGA NPs surface-modified with the p8 peptide. Moreover, characterization of cytokine production in vaccinated-infected mice revealed that protection was accompanied by significant increase of IFNγ and lower levels of IL-4 and IL-10 in protected mice when compared to control infected group. Conclusively, the above nanoformulations hold promise for future vaccination strategies against VL.

Liposomal adjuvant development for leishmaniasis vaccines

Leishmaniasis is a parasitic disease that ranges in severity from skin lesions to fatality. Since long-lasting protection is induced upon recovery from cutaneous leishmaniasis, development of an effective vaccine is promising. However, there is no vaccine for use in humans yet. It seems limited efficacy in leishmaniasis vaccines is due to lack of an appropriate adjuvant or delivery system. Hence, the use of particulate adjuvants such as liposomes for effective delivery to the antigen presenting cells (APCs) is a valuable strategy to enhance leishmaniasis vaccine efficacy. The extraordinary versatility of liposomes because of their unique amphiphilic and biphasic nature allows for using antigens or immunostimulators within the core, on the surface or within the bilayer, and modulates both the magnitude and the T-helper bias of the immune response. In this review article, we attempt to summarize the role of liposomal adjuvants in the development of Leishmania vaccines and describe the main physicochemical properties of liposomes like phospholipid composition, surface charge, and particle size during formulation design. We also suggest potentially useful formulation strategies in order for future experiments to have a chance to succeed as liposomal vaccines against leishmaniasis.

Withania somnifera chemotype NMITLI 101R significantly increases the efficacy of antileishmanial drugs by generating strong IFN-γ and IL-12 mediated immune responses in Leishmania donovani infected hamsters

BACKGROUND

Withania somnifera (L.) Dunal (Solanaceae), commonly known as Ashwagandha, is one of the most important medicinal plant in the traditional Indian medical systems. Pharmacological studies have established that root extracts of W. somnifera contain several bioactive constituents called withanolides. The plant has long been used for its several beneficial properties and recently as an immunomodulator.

HYPOTHESIS/PURPOSE

A combination therapy including a potential and safe immunostimulant with lower doses of effective drug, which can reduce the parasitic burden and simultaneously can produce an enhancement of adaptive immunity, has proven to be significantly a more effective approach than immunotherapy or drug therapy alone.

STUDY DESIGN

Evaluation of the immunostimulatory effect of W. somnifera chemotype NMITLI 101R when used in combination with ED₅₀ doses of antileishmanial drugs in Leishmania donovani infected hamsters.

METHODS

Infected animals were administered with chemotype 101R(30mg/kg × 15 days) either alone or in combination with ED₅₀ doses of miltefosine (10mg/kg × 5 days), paromomycin (30mg/kg × 5 days) or amphotericin B (0.5mg/kg × 5 days). The treated animals were euthanized on days 30 and 60 post-treatment (p.t.) and checked for parasite clearance, delayed type hypersensitivity (DTH) response, cytokine and inducible nitric oxide synthase levels by real-time PCR, nitric oxide (NO) production, reactive oxygen species (ROS) generation, lymphoproliferative and antibody responses.

RESULTS

The group of animals that received 101R and ED₅₀ dose of miltefosine showed optimum inhibition of parasite multiplication (∼98%) by day 60 p.t. followed by the group that received 101R plus paromomycin (∼94%) and 101R plus amphotericin B (∼93%). The efficacy was well supported by the increased inducible NO synthase mRNA transcript, strong IFN-γand IL-12 mediated Th1 immune responses and significantly suppressed levels of Th2 cytokines (IL-4, IL-10 and TGF-β). Additionally, same therapy also induced significant increase in the level of NO production, ROS generation, Leishmania specific IgG2 antibody along with profound DTH and strong T-cell responses as compared with all the other treated groups.

CONCLUSION

Our results suggest that combination of chemotype 101R with ED₅₀ doses of antileishmanial drugs may provide a promising alternative for the cure of visceral leishmaniasis with significant restoration of the host immune response.

Cross-protective efficacy of Leishmania infantum LiHyD protein against tegumentary leishmaniasis caused by Leishmania major and Leishmania braziliensis species

Vaccination can be considered the most cost-effective strategy to control neglected diseases, but nowadays there is not an effective vaccine available against leishmaniasis. In the present study, a vaccine based on the combination of the Leishmania-specific hypothetical protein (LiHyD) with saponin was tested in BALB/c mice against infection caused by Leishmania major and Leishmania braziliensis species. This antigen was firstly identified in Leishmania infantum and showed to be protective against infection of BALB/c mice using this parasite species. The immunogenicity of rLiHyD/saponin vaccine was evaluated, and the results showed that immunized mice produced high levels of IFN-γ, IL-12 and GM-CSF after in vitro stimulation with rLiHyD, as well as by using L. major or L. braziliensis protein extracts. After challenge, vaccinated animals showed significant reductions in the infected footpad swellings, as well as in the parasite burden in the infection site, liver, spleen, and infected paws draining lymph nodes, when compared to those that were inoculated with the vaccine diluent (saline) or immunized with saponin. The immunization of rLiHyD without adjuvant was not protective against both challenges. The partial protection obtained by the rLiHyD/saponin vaccine was associated with a parasite-specific IL-12-dependent IFN-γ secretion, which was produced mainly by CD4(+) T cells. In these animals, a decrease in the parasite-mediated IL-4 and IL-10 responses, associated with the presence of high levels of LiHyD- and parasite-specific IgG2a isotype antibodies, were also observed. The present study showed that a hypothetical protein that was firstly identified in L. infantum, when combined to a Th1 adjuvant, was able to confer a cross-protection against highly infective stationary-phase promastigotes of two Leishmania species causing tegumentary leishmaniasis.

Immunoprotective responses of T helper type 1 stimulatory protein-S-adenosyl-L-homocysteine hydrolase against experimental visceral leishmaniasis

It is well known that a patient in clinical remission of visceral leishmaniasis (VL) remains immune to reinfection, which provides a rationale for the feasibility of a vaccine against this deadly disease. In earlier studies, observation of significant cellular responses in treated Leishmania patients as well as in hamsters against leishmanial antigens from different fractions led to its further proteomic characterization, wherein S-adenosyl-L-homocysteine hydrolase (AdoHcy) was identified as a helper type 1 (Th1) stimulatory protein. The present study includes immunological characterization of this protein, its cellular responses [lymphoproliferation, nitric oxide (NO) production and cytokine responses] in treated Leishmania-infected hamsters and patients as well as prophylactic efficacy against Leishmania challenge in hamsters and the immune responses generated thereof. Significantly higher cellular responses were noticed against recombinant L. donovani S-adenosyl-L-homocysteine hydrolase (rLdAdoHcy) compared to soluble L. donovani antigen in treated samples. Moreover, stimulation of peripheral blood mononuclear cells with rLdAdoHcy up-regulated the levels of interferon (IFN)-γ, interleukin (IL)-12 and down-regulated IL-10. Furthermore, vaccination with rLdAdoHcy generated perceptible delayed-type hypersensitivity response and exerted considerably good prophylactic efficacy (∼70% inhibition) against L. donovani challenge. The efficacy was confirmed by the increased expression levels of inducible NO synthase and Th1-type cytokines, IFN-γ and IL-12 and down-regulation of IL-4, IL-10 and transforming growth factor (TGF)-β. The results indicate the potentiality of rLdAdoHcy protein as a suitable vaccine candidate against VL.

Studies on the protective efficacy of freeze thawed promastigote antigen of Leishmania donovani along with various adjuvants against visceral leishmaniasis infection in mice

Visceral leishmaniasis (VL) caused by Leishmania donovani persists as a major public health issue in tropical and subtropical areas of the world. Current treatment of this disease relies on use of drugs. It is doubtful that chemotherapy can alone eradicate the disease, so there is a need for an effective vaccine. Killed antigen candidates remain a good prospect considering their ease of formulation, stability, low cost and safety. To enhance the efficacy of killed vaccines suitable adjuvant and delivery system are needed. Therefore, the current study was conducted to determine the protective efficacy of freeze-thawed L. donovani antigen in combination with different adjuvants against experimental infection of VL. For this, BALB/c mice were immunized thrice at an interval of two weeks. Challenge infection was given two weeks after last immunization. Mice were sacrificed after last immunization and on different post challenge/infection days. Immunized mice showed significant reduction in parasite burden, enhanced DTH responses with increased levels of Th1 cytokines and lower levels of Th2 cytokines, thus indicating the development of a protective Th1 response. Maximum protection was achieved with liposome encapsulated freeze thawed promastigote (FTP) antigen of L. donovani and it was followed by group immunized with FTP+MPL-A, FTP+saponin, FTP+alum and FTP antigen (alone). The present study highlights greater efficacy of freeze thawed promastigote antigen as a potential vaccine candidate along with effective adjuvant formulations against experimental VL infection.

Nanotechnology-Based Drug Delivery Systems for Melanoma Antitumoral Therapy: A Review

Melanoma (MEL) is a less common type of skin cancer, but it is more aggressive with a high mortality rate. The World Cancer Research Fund International (GLOBOCAN 2012) estimates that there were 230,000 new cases of MEL in the world in 2012. Conventional MEL treatment includes surgery and chemotherapy, but many of the chemotherapeutic agents used present undesirable properties. Drug delivery systems are an alternative strategy by which to carry antineoplastic agents. Encapsulated drugs are advantageous due to such properties as high stability, better bioavailability, controlled drug release, a long blood circulation time, selective organ or tissue distribution, a lower total required dose, and minimal toxic side effects. This review of scientific research supports applying a nanotechnology-based drug delivery system for MEL therapy.

Immunological consequences of stress-related proteins – cytosolic tryparedoxin peroxidase and chaperonin TCP20 – identified in splenic amastigotes ofLeishmania donovanias Th1 stimulatory, in experimental visceral leishmaniasis

In earlier studies, proteomic characterization of splenic amastigote fractions from clinical isolates ofLeishmania donovani, exhibiting significant cellular responses in curedLeishmaniasubjects, led to the identification of cytosolic tryparedoxin peroxidase (LdcTryP) and chaperonin-TCP20 (LdTCP20) as Th1-stimulatory proteins. Both the proteins, particularly LdTCP20 for the first time, were successfully cloned, overexpressed, purified and were found to be localized in the cytosol of purified splenic amastigotes. When evaluated against lymphocytes of curedLeishmania-infected hamsters, the purified recombinant proteins (rLdcTryP and rLdTCP20) induced their proliferations as well as nitric oxide production. Similarly, these proteins also generated Th1-type cytokines (IFN-γ/IL-12) from stimulated PBMCs of cured/endemicLeishmaniapatients. Further, vaccination with rLdcTryP elicited noticeable delayed-type hypersensitivity response and offered considerably good prophylactic efficacy (~78% inhibition) againstL. donovanichallenge in hamsters, which was well supported by the increased mRNA expression of Th1 and Th2 cytokines. However, animals vaccinated with rLdTCP20 exhibited comparatively lesser prophylactic efficacy (~55%) with inferior immunological response. The results indicate the potentiality of rLdcTryP protein, between the two, as a suitable anti-leishmanial vaccine. Since, rLdTCP20 is also an important target, for optimization, further attempts towards determination of immunodominant regions for designing fusion peptides may be taken up.

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.

Nanobiotechnologic approach to a promising vaccine prototype for immunisation against leishmaniasis: a fast and effective method to incorporate GPI-anchored proteins of Leishmania amazonensis into liposomes

Liposomes are known to be a potent adjuvant for a wide range of antigens, as well as appropriate antigen carriers for antibody generation response in vivo. In addition, liposomes are effective vehicles for peptides and proteins, thus enhancing their immunogenicity. Considering these properties of liposomes and the antigenicity of the Leishmania membrane proteins, we evaluated if liposomes carrying glycosylphosphatidylinositol (GPI)-anchored proteins of Leishmania amazonensis promastigotes could induce protective immunity in BALB/c mice. To assay protective immunity, BALB/c mice were intraperitoneally injected with liposomes, GPI-protein extract (EPSGPI) as well as with the proteoliposomes carrying GPI-proteins. Mice inoculated with EPSGPI and total protein present in constitutive proteoliposomes displayed a post-infection protection of about 70% and 90%, respectively. The liposomes are able to work as adjuvant in the EPSGPI protection. These systems seem to be a promising vaccine prototype for immunisation against leishmaniasis.

Combining cationic liposomal delivery with MPL-TDM for cysteine protease cocktail vaccination against Leishmania donovani: evidence for antigen synergy and protection

BACKGROUND

With the paucity of new drugs and HIV co-infection, vaccination remains an unmet research priority to combat visceral leishmaniasis (VL) requiring strong cellular immunity. Protein vaccination often suffers from low immunogenicity and poor generation of memory T cells for long-lasting protection. Cysteine proteases (CPs) are immunogenic proteins and key mediators of cellular functions in Leishmania. Here, we evaluated the vaccine efficacies of CPs against VL, using cationic liposomes with Toll like receptor agonists for stimulating host immunity against L. donovani in a hamster model.

METHODOLOGY/PRINCIPAL FINDINGS

Recombinant CPs type I (cpb), II (cpa) and III (cpc) of L. donovani were tested singly and in combination as a triple antigen cocktail for antileishmanial vaccination in hamsters. We found the antigens to be highly immunoreactive and persistent anti-CPA, anti-CPB and anti-CPC antibodies were detected in VL patients even after cure. The liposome-entrapped CPs with monophosphoryl lipid A-Trehalose dicorynomycolate (MPL-TDM) induced significantly high nitric oxide (up to 4 fold higher than controls) mediated antileishmanial activity in vitro, and resulted in strong in vivo protection. Among the three CPs, CPC emerged as the most potent vaccine candidate in combating the disease. Interestingly, a synergistic increase in protection was observed with liposomal CPA, CPB and CPC antigenic cocktail which reduced the organ parasite burden by 1013-1016 folds, and increased the disease-free survival of >80% animals at least up to 6 months post infection. Robust secretion of IFN-γ and IL-12, along with concomitant downregulation of Th2 cytokines, was observed in cocktail vaccinates, even after 3 months post infection.

CONCLUSION/SIGNIFICANCE

The present study is the first report of a comparative efficacy of leishmanial CPs and their cocktail using liposomal formulation with MPL-TDM against L. donovani. The level of protection attained has not been reported for any other subcutaneous single or polyprotein vaccination against VL.

Nucleosomal histone proteins of L. donovani: a combination of recombinant H2A, H2B, H3 and H4 proteins were highly immunogenic and offered optimum prophylactic efficacy against Leishmania challenge in hamsters

The present study includes cloning and expression of recombinant Leishmania donovani histone proteins (rLdH2B, rLdH3, rLdH2A and rLdH4), assessment of their immunogenicity in Leishmania infected cured patients/endemic contacts as well as in cured hamsters and finally evaluation of their prophylactic efficacy in hamsters against L. donovani challenge. All recombinant proteins were expressed and purified from the heterologous bacterial host system. Leishmania infected cured patients/endemic contacts as well as cured hamsters exhibited significantly higher proliferative responses to individual recombinant histones and their pooled combination (rLdH2B+rLdH3+rLdH2A+rLdH4) than those of L.donovani infected hosts. The L.donovani soluble antigens (SLD) stimulated PBMCs of cured/exposed and Leishmania patients to produce a mixed Thl/Th2-type cytokine profile, whereas rLdH2B, rLdH3, rLdH2A, rLdH4 and pooled combination (rLdH2-4) stimulated the production of Th1 cytokines IFN-γ, IL-12 and TNF-α but not Th2 cytokines IL-4 or IL-10. The immunogenicity of these histone proteins along with their combination was also checked in cured hamsters where they stimulated higher lymphoproliferation and Nitric oxide production in lymphocytes of cured hamsters than that of infected controls. Moreover, significantly increased IgG2 response, an indicative of cell mediated immunity, was observed in cured hamsters against these individual proteins and their combination as compared to infected hamsters. Further, it was demonstrated that rLdH2B, rLdH3, rLdH2A and rLdH4 and pooled combination were able to provide considerable protection for hamsters against L. donovani challenge. The efficacy was supported by the increased inducible Nitric Oxide Synthase (iNOS) mRNA transcripts and Th1-type cytokines--IFN-γ, IL-12 and TNF-α and down-regulation of IL-4, IL-10 and TGF-β. Hence, it is inferred that pooled rLdH2-4 elicits Thl-type of immune responses exclusively and confer considerable protection against experimental Visceral Leishmaniasis.

Combination of liposomal CpG oligodeoxynucleotide 2006 and miltefosine induces strong cell-mediated immunity during experimental visceral leishmaniasis

Immuno-modulators in combination with antileishmanial drug miltefosine is a better therapeutic approach for treatment of Visceral Leishmaniasis (VL) as it not only reduces the dose of miltefosine but also shortens the treatment regimen. However, immunological mechanisms behind the perceived benefits of this combination therapy have not been investigated in detail. In the present study, we hypothesized that potential use of drugs that target the host in addition to the parasite might represent an alternative strategy for combination therapy. We investigated immune responses generated in Leishmania donovani infected animals (hamsters and mice) treated with combination of CpG-ODN-2006 and miltefosine at short dose regimen. Infected animals were administered CpG-ODN-2006 (0.4 mg/kg, single dose), as free and liposomal form, either alone or in combination with miltefosine for 5 consecutive days and parasite clearance was evaluated at day 4 and 7 post treatment. Animals that received liposomal CpG-ODN-2006 (lipo-CpG-ODN-2006) and sub-curative miltefosine (5 mg/kg) showed the best inhibition of parasite multiplication (∼97%) which was associated with a biased Th1 immune response in. Moreover, compared to all the other treated groups, we observed increased mRNA expression levels of pro-inflammatory cytokines (IFN-γ, TNF-α and IL-12) and significantly suppressed levels of Th2 cytokines (IL-10 and TGF-β) on day 4 post treatment in animals that underwent combination therapy with lipo-CpG-ODN-2006 and sub-curative miltefosine. Additionally, same therapy also induced heightened iNOS mRNA levels and NO generation, increased IgG2 antibody level and strong T-cell response in these hamsters compared with all the other treated groups. Collectively, our results suggest that combination of lipo-CpG-ODN-2006 and sub-curative miltefosine generates protective T-cell response in an animal model of visceral leishmaniasis which is characterized by strong Th1 biased immune response thereby underlining our hypothesis that combination therapy, at short dose regimen can be used as a novel way of treating visceral leishmaniasis.

IL-4 contributes to failure, and colludes with IL-10 to exacerbate Leishmania donovani infection following administration of a subcutaneous leishmanial antigen vaccine

Background

Visceral leishmaniasis caused by the protozoan parasite Leishmania donovani complex is a potentially fatal disease if left untreated. Few treatment options exist and are toxic, costly and ineffective against resistant strains. Thus a safe and efficacious vaccine to combat this disease is needed. Previously, we reported that intraperitoneal administration of leishmanial antigens (LAg) entrapped in liposomes conferred protection to BALB/c mice against L. donovani challenge infection. However, this vaccine failed to protect mice when administered subcutaneously. We therefore evaluated whether formulation of LAg in combination with two commonly used human-compatible adjuvants, alum and saponin, could improve the protective efficacy of subcutaneously administered LAg, to a level comparable to that of the intraperitoneal liposomal vaccination.

Results

Vaccine formulations of LAg with alum or saponin failed to reduce parasite burden in the liver, and alum + LAg immunized mice also failed to reduce parasite burden in the spleen. Interestingly, saponin + LAg vaccination actually resulted in an increased L. donovani parasitic load in the spleen following L. donovani challenge, suggesting this regimen exacerbates the infection. In contrast, mice immunized intraperitoneally with Lip + LAg demonstrated significant protection in both liver and spleen, as expected. Mechanistically, we found that failure of alum + LAg to protect mice was associated with elevated levels of IL-4, whereas both IL-4 and IL-10 levels were increased in saponin + LAg immunized mice. This outcome served to exacerbate L. donovani infection in the saponin + LAg group, despite a concurrent increase in proinflammatory IFN-γ production. On the contrary, protection against L. donovani challenge in Lip + LAg immunized mice was associated with elevated levels of IFN-γ in conjunction with low levels of IL-4 and IL-10 production.

Conclusions

These findings indicate that elevated levels of IL-4 may contribute to LAg vaccine failure, whereas combined elevation of IL-4 together with IL-10 exacerbated the disease as observed in saponin + LAg immunized mice. In contrast, a robust IFN-γ response, in the absence of IL-4 and IL-10 production, was associated with protective immunity following administration of the Lip + LAg vaccine. Together these findings suggest that optimization of antigen/adjuvant formulations to minimize IL-4 and IL-10 induction may be helpful in the development of high efficacy vaccines targeting Leishmania.

Induction of protection against leishmaniasis in susceptible BALB/c mice using simple DOTAP cationic nanoliposomes containing soluble Leishmania antigen (SLA)

A suitable adjuvant and delivery system are needed to develop an effective vaccine against leishmaniasis. To induce a Th1 type of response and protection in BALB/c mice against Leishmania major infection, 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) nanoliposomes bearing an intrinsic adjuvanticity, were used as an antigen delivery system and immunoadjuvant for soluble Leishmania antigens (SLA). DOTAP liposomes containing different concentrations of SLA were prepared by using lipid film method followed by sonication. The prepared vesicles showed a diameter of about 100nm, a positive zeta potential and approximately 70% encapsulation efficiency of SLA. BALB/c mice were immunized subcutaneously (SC), three times in a 3-week interval with different concentrations of liposomal SLA (12.5, 25, and 50μg of SLA/50μl/mice), free SLA and as well as free liposome. The group of mice received 50μg of SLA in DOTAP-nanoliposomes showed a significantly (p<0.001) smaller footpad swelling and the lowest spleen and footpad parasite burden after the challenge. This group also showed the highest IFN-γ production compared to the other groups, lower IL-4 level and higher IgG2a antibody titer. Taken together, the results indicated that simple DOTAP nanoliposome containing 1μg/μl SLA are appropriate delivery systems to induce a Th1 type of immune response and protection against L. major infection in BALB/c mice.

Heat shock proteins enriched-promastigotes of Leishmania major inducing Th2 immune response in BALB/c mice

BACKGROUND

Heat shock proteins (HSP) are highly conserved molecules with many immunological functions. They are highly immunogenic with important role in cancer immunotherapy and in vaccine development against infectious diseases. As adjuvant, HSP can augment the immunogenicity of weak antigens and can stimulate antigen presenting cells. Although vaccines have been successful for many infectious diseases, progress in leishmaniasis has not been achieved. In this report, the protective effect of HSP-enriched soluble leishmania antigen (SLA) was determined.

METHODS

BALB/c mice were immunized 3× with HSP-enriched SLA and SLA alone and 10 days after final boost. They were infected with 106 stationary phase promastigote of Leishmania major and immunological responses were followed until nine weeks.

RESULTS

No significant differences were observed in lymphocyte proliferation, footpad swelling, parasite burden, nitric oxide or IL-12 cytokine between HSP-enriched or SLA groups. Although the levels of IFN-γ, IL-4, TGF-β, IgG1 and IgG2b were increased in both groups, IFN-γ was significantly higher in SLA group and IgG2a in HSP-enriched SLA.

CONCLUSION

These results indicate that HSP direct the immune system towards Th2 pattern and does not have protective role in L. major infection.

Effect of NF-κB inhibitor aurothiomalate on local inflammation in experimental Th1- and Th2-type immune response

We compared the effect of NF-κB inhibitor aurothiomalate and voltaren on local inflammation in different types of immune response. Both substances reduced edema caused by sheep erythrocytes (Th1-type immune response) and local immediate-type hypersensitivity response induced with ovalbumin (Th2-dependent response). The anti-inflammatory effects of aurothiomalate were similar to those of voltaren during Th1-type immune response.

Leishmania donovani triose phosphate isomerase: a potential vaccine target against visceral leishmaniasis

Visceral leishmaniasis (VL) is one of the most important parasitic diseases with approximately 350 million people at risk. Due to the non availability of an ideal drug, development of a safe, effective, and affordable vaccine could be a solution for control and prevention of this disease. In this study, a potential Th1 stimulatory protein- Triose phosphate isomerase (TPI), a glycolytic enzyme, identified through proteomics from a fraction of Leishmania donovani soluble antigen ranging from 89.9–97.1 kDa, was assessed for its potential as a suitable vaccine candidate. The protein- L. donovani TPI (LdTPI) was cloned, expressed and purified which exhibited the homology of 99% with L. infantum TPI. The rLdTPI was further evaluated for its immunogenicity by lymphoproliferative response (LTT), nitric oxide (NO) production and estimation of cytokines in cured Leishmania patients/hamster. It elicited strong LTT response in cured patients as well as NO production in cured hamsters and stimulated remarkable Th1-type cellular responses including IFN-ã and IL-12 with extremely lower level of IL-10 in Leishmania-infected cured/exposed patients PBMCs in vitro. Vaccination with LdTPI-DNA construct protected naive golden hamsters from virulent L. donovani challenge unambiguously (∼90%). The vaccinated hamsters demonstrated a surge in IFN-ã, TNF-á and IL-12 levels but extreme down-regulation of IL-10 and IL-4 along with profound delayed type hypersensitivity and increased levels of Leishmania-specific IgG2 antibody. Thus, the results are suggestive of the protein having the potential of a strong candidate vaccine.

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.

Evaluation of Leishmania donovani protein disulfide isomerase as a potential immunogenic protein/vaccine candidate against visceral Leishmaniasis

In Leishmania species, Protein disulfide isomerase (PDI) - a redox chaperone, is reported to be involved in its virulence and survival. This protein has also been identified, through proteomics, as a Th1 stimulatory protein in the soluble lysate of a clinical isolate of Leishmania donovani (LdPDI). In the present study, the molecular characterization of LdPDI was carried out and the immunogenicity of recombinant LdPDI (rLdPDI) was assessed by lymphocyte proliferation assay (LTT), nitric oxide (NO) production, estimation of Th1 cytokines (IFN-γ and IL-12) as well as IL-10 in PBMCs of cured/endemic/infected Leishmania patients and cured L. donovani infected hamsters. A significantly higher proliferative response against rLdPDI as well as elevated levels of IFN-γ and IL-12 were observed. The level of IL-10 was found to be highly down regulated in response to rLdPDI. A significant increase in the level of NO production in stimulated hamster macrophages as well as IgG2 antibody and a low level of IgG1 in cured patient's serum was observed. Higher level of IgG2 antibody indicated its Th1 stimulatory potential. The efficacy of pcDNA-LdPDI construct was further evaluated for its prophylactic potential. Vaccination with this construct conferred remarkably good prophylactic efficacy (∼90%) and generated a robust cellular immune response with significant increases in the levels of iNOS transcript as well as TNF-α, IFN-γ and IL-12 cytokines. This was further supported by the high level of IgG2 antibody in vaccinated animals. The in vitro as well as in vivo results thus indicate that LdPDI may be exploited as a potential vaccine candidate against visceral Leishmaniasis (VL).

Secreted virulence factors and immune evasion in visceral leishmaniasis

Evasion or subversion of host immune responses is a well-established paradigm in infection with visceralizing leishmania. In this review, we summarize current findings supporting a model in which leishmania target host regulatory molecules and pathways, such as the PTP SHP-1 and the PI3K/Akt signaling cascade, to prevent effective macrophage activation. Furthermore, we describe how virulence factors, secreted by leishmania, interfere with macrophage intracellular signaling. Finally, we discuss mechanisms of secretion and provide evidence that leishmania use a remarkably adept, exosome-based secretion mechanism to export and deliver effector molecules to host cells. In addition to representing a novel mechanism for trafficking of virulence factors across membranes, recent findings indicate that leishmania exosomes may have potential as vaccine candidates.

Proteoliposomes in nanobiotechnology

Proteoliposomes are systems that mimic lipid membranes (liposomes) to which a protein has been incorporated or inserted. During the last decade, these systems have gained prominence as tools for biophysical studies on lipid-protein interactions as well as for their biotechnological applications. Proteoliposomes have a major advantage when compared with natural membrane systems, since they can be obtained with a smaller number of lipidic (and protein) components, facilitating the design and interpretation of certain experiments. However, they have the disadvantage of requiring methodological standardization for incorporation of each specific protein, and the need to verify that the reconstitution procedure has yielded the correct orientation of the protein in the proteoliposome system with recovery of its functional activity. In this review, we chose two proteins under study in our laboratory to exemplify the steps necessary for the standardization of the reconstitution of membrane proteins in liposome systems: (1) alkaline phosphatase, a protein with a glycosylphosphatidylinositol anchor, and (2) Na,K-ATPase, an integral membrane protein. In these examples, we focus on the production of the specific proteoliposomes, as well as on their biochemical and biophysical characterization, with emphasis on studies of lipid-protein interactions. We conclude the chapter by highlighting current prospects of this technology for biotechnological applications, including the construction of nanosensors and of a multi-protein nanovesicular biomimetic to study the processes of initiation of skeletal mineralization.

Leishmania donovani: immunostimulatory cellular responses of membrane and soluble protein fractions of splenic amastigotes in cured patient and hamsters

Visceral leishmaniasis (VL), caused by the intracellular parasite Leishmania donovani, L. chagasi and L. infantum is characterized by defective cell-mediated immunity (CMI) and is usually fatal if not treated properly. An estimated 350 million people worldwide are at risk of acquiring infection with Leishmania parasites with approximately 500,000 cases of VL being reported each year. In the absence of an efficient and cost-effective antileishmanial drug, development of an appropriate long-lasting vaccine against VL is the need of the day. In VL, the development of a CMI, capable of mounting Th1-type of immune responses, play an important role as it correlate with recovery from and resistance to disease. Resolution of infection results in lifelong immunity against the disease which indicates towards the feasibility of a vaccine against the disease. Most of the vaccination studies in Leishmaniasis have been focused on promastigote- an infective stage of parasite with less exploration of pathogenic amastigote form, due to the cumbersome process of its purified isolation. In the present study, we have isolated and purified splenic amastigotes of L. donovani, following the traditional protocol with slight modification. These were fractionated into five membranous and soluble subfractions each i.e MAF1-5 and SAF1-5 and were subjected for evaluation of their ability to induce cellular responses. Out of five sub-fractions from each of membrane and soluble, only four viz. MAF2, MAF3, SAF2 and SAF3 were observed to stimulate remarkable lymphoproliferative, IFN-γ, IL-12 responses and Nitric Oxide production, in Leishmania-infected cured/exposed patients and hamsters. Results suggest the presence of Th-1 type immunostimulatory molecules in these sub-fractions which may further be exploited for developing a successful subunit vaccine from the less explored pathogenic stage against VL.

Cationic liposomes containing soluble Leishmania antigens (SLA) plus CpG ODNs induce protection against murine model of leishmaniasis

Development of an effective vaccine against leishmaniasis is possible due to the fact that individuals cured from cutaneous leishmaniasis (CL) are protected from further infection. First generation Leishmania vaccines consisting of whole killed parasites reached to phase 3 clinical trials but failed to show enough efficacies mainly due to the lack of an appropriate adjuvant. In this study, an efficient liposomal protein-based vaccine against Leishmania major infection was developed using soluble Leishmania antigens (SLA) as a first generation vaccine and cytidine phosphate guanosine oligodeoxynucleotides (CpG ODNs) as an immunostimulatory adjuvant. 1, 2-Dioleoyl-3-trimethylammonium-propane was used as a cationic lipid to prepare the liposomes due to its intrinsic adjuvanticity. BALB/c mice were immunized subcutaneously (SC), three times in 2-week intervals, with Lip-SLA-CpG, Lip-SLA, SLA + CpG, SLA, or HEPES buffer. As criteria for protection, footpad swelling at the site of challenge and spleen parasite loads were assessed, and the immune responses were evaluated by determination of IFN-γ and IL-4 levels of cultured splenocytes, and IgG subtypes. The group of mice that received Lip-SLA-CpG showed a significantly smaller footpad swelling, lower spleen parasite burden, higher IgG2a antibody, and lower IL-4 level compared to the control groups. It is concluded that cationic liposomes containing SLA and CpG ODNs are appropriate to induce Th1 type of immune response and protection against leishmaniasis.

Vaccination with liposomal leishmanial antigens adjuvanted with monophosphoryl lipid-trehalose dicorynomycolate (MPL-TDM) confers long-term protection against visceral leishmaniasis through a human administrable route

The development of a long-term protective subunit vaccine against visceral leishmaniasis depends on antigens and adjuvants that can induce an appropriate immune response. The immunization of leishmanial antigens alone shows limited efficacy in the absence of an appropriate adjuvant. Earlier we demonstrated sustained protection against Leishmania donovani with leishmanial antigens entrapped in cationic liposomes through an intraperitoneal route. However, this route is not applicable for human administration. Herein, we therefore evaluated the immune response and protection induced by liposomal soluble leishmanial antigen (SLA) formulated with monophosphoryl lipid-trehalose dicorynomycolate (MPL-TDM) through a subcutaneous route. Subcutaneous immunization of BALB/c mice with SLA entrapped in liposomes or with MPL-TDM elicited partial protection against experimental visceral leishmaniasis. In contrast, liposomal SLA adjuvanted with MPL-TDM induced significantly higher levels of protection in liver and spleen in BALB/c mice challenged 10 days post-vaccination. Protection conferred by this formulation was sustained up to 12 weeks of immunization, and infection was controlled for at least 4 months of the challenge, similar to liposomal SLA immunization administered intraperitoneally. An analysis of cellular immune responses of liposomal SLA + MPL-TDM immunized mice demonstrated the induction of IFN-γ and IgG2a antibody production not only 10 days or 12 weeks post-vaccination but also 4 months after the challenge infection and a down regulation of IL-4 production after infection. Moreover, long-term immunity elicited by this formulation was associated with IFN-γ production also by CD8⁺ T cells. Taken together, our results suggest that liposomal SLA + MPL-TDM represent a good vaccine formulation for the induction of durable protection against L. donovani through a human administrable route.

Radio-attenuated leishmanial parasites as immunoprophylactic agent against experimental murine visceral leishmaniasis

The present study intends to evaluate the role of radio-attenuated leishmania parasites as immunoprophylactic agents for experimental murine visceral leishmaniasis. BALB/c mice were immunized with gamma (γ)-irradiated Leishmania donovani. A second immunization was given after 15 days of first immunization. After two immunizations, mice were infected with virulent L. donovani promastigotes. Protection against Kala-azar (KA) was estimated from spleen and liver parasitic burden along with the measurement of nitrite and superoxide anion generation by isolation of splenocytes and also by T-lymphocyte helper 1(Th1) and T-lymphocyte helper 2(Th2) cytokines release from the experimental groups. It was observed that BALB/c mice having prior immunization with radio-attenuated parasites showed protection against L. donovani infection through higher expression of Th1 cytokines and suppression of Th2 cytokines along with the generation of protective free radicals. The group of mice without prior priming with radio-attenuated parasites surrendered to the disease. Thus it can be concluded that radio-attenuated L. donovani may be used for.