Efficacy of human beta-casein fragment (54-59) and its synthetic analogue compound 89/215 against Leishmania donovani in hamsters

Role of Cytokines in Experimental and Human Visceral Leishmaniasis

Visceral Leishmaniasis (VL) is the most fatal form of disease leishmaniasis. To date, there are no effective prophylactic measures and therapeutics available against VL. Recently, new immunotherapy-based approaches have been established for the management of VL. Cytokines, which are predominantly produced by helper T cells (Th) and macrophages, have received great attention that could be an effective immunotherapeutic approach for the treatment of human VL. Cytokines play a key role in forming the host immune response and in managing the formation of protective and non-protective immunities during infection. Furthermore, immune response mediated through different cytokines varies from different host or animal models. Various cytokines viz. IFN-γ, IL-2, IL-12, and TNF-α play an important role during protection, while some other cytokines viz. IL-10, IL-6, IL-17, TGF-β, and others are associated with disease progression. Therefore, comprehensive knowledge of cytokine response and their interaction with various immune cells is very crucial to determine appropriate immunotherapies for VL. Here, we have discussed the role of cytokines involved in VL disease progression or host protection in different animal models and humans that will determine the clinical outcome of VL and open the path for the development of rapid and accurate diagnostic tools as well as therapeutic interventions against VL.

Immunization of Experimental Dogs With Salivary Proteins From Lutzomyia longipalpis, Using DNA and Recombinant Canarypox Virus Induces Immune Responses Consistent With Protection Against Leishmania infantum

Metacyclic Leishmania promastigotes are transmitted by sand flies that inject parasites and saliva into the host's skin. Previous studies have demonstrated that DNA plasmids encoding Lutzomyia longipalpis salivary proteins LJM17 and LJL143, when used to immunize dogs, resulted in a systemic and local Th1 cell-mediated immunity that interfered in parasite survival in vitro. Here we evaluated the ability of these same salivary antigens to induce anti-Leishmania immunity and to confer protection by immunizing dogs using a novel vaccination strategy more suitable for use in the field. The strategy consisted of a single dose of plasmid followed by two doses of recombinant Canarypoxvirus (rCanarypoxvirus) expressing L. longipalpis salivary proteins (LJM17 or LJL143). Thirty days after the final immunization, dogs were intradermally challenged with 10⁷Leishmania infantum promastigotes in the presence of L. longipalpis saliva. We followed the experimentally infected dogs for 10 months to characterize clinical, parasitological, and immunological parameters. Upon vaccination, all immunized dogs presented strong and specific humoral responses with increased serum concentrations of IFN-γ, TNF, IL-7, and IL-15. The serum of dogs immunized with LJM17 also exhibited high levels of IL-2, IL-6, and IL-18. L. infantum infection was established in all experimental groups as evidenced by the presence of anti-Leishmania IgG, and by parasite detection in the spleen and skin. Dogs immunized with LJM17-based vaccines presented higher circulating levels of IFN-γ, IL-2, IL-6, IL-7, IL-15, IL-18, TNF, CXCL10, and GM-CSF post-infection when compared with controls. Results demonstrated that relevant Leishmania-specific immune responses were induced following vaccination of dogs with L. longipalpis salivary antigen LJM17 administered in a single priming dose of plasmid DNA, followed by two booster doses of recombinant Canarypox vector. Importantly, a significant increase in pro-inflammatory cytokines and chemokines known to be relevant for protection against leishmaniasis was evidenced after challenging LJM17-vaccinated dogs as compared to controls. Although similar results were observed following immunization with LJL143, the pro-inflammatory response observed after immunization was attenuated following infection. Collectively, these data suggest that the LJM17-based vaccine induced an immune profile consistent with the expected protective immunity against canine leishmaniosis. These results clearly support the need for further evaluation of the LJM17 antigen, using a heterologous prime-boost vaccination strategy against canine visceral leishmaniosis (CVL).

Preparation of surface-imprinted microspheres effectively controlled by orientated template immobilization using highly cross-linked raspberry-like microspheres for the selective recognition of an immunostimulating peptide

Surface-imprinted microspheres were prepared using raspberry-like microspheres for selectively recognizing IHH.

Preparation of highly cross-linked raspberry-like nano/microspheres and surface tailoring for controlled immunostimulating peptide adsorption

The surface functionalities of ionic liquid-functionalized nano/microspheres with a highly cross-linked raspberry-like structure could be well controlled by adjusting the functional chains appropriately.

Characterization and evaluation of amphotericin B loaded MDP conjugated poly(propylene imine) dendrimers

This paper describes a novel strategy for targeted delivery of amphotericin B (AmB) to macrophages with muramyl dipeptide (MDP) conjugated multimeric poly(propyleneimine) (PPI) dendrimers. Synergistic antiparasitic activity due to immunostimulation by multimeric presentation of MDP on dendrimers was anticipated. MDP conjugated 5.0G PPI (MdPPI) dendrimers were synthesized and characterized. Therapeutic activity and toxicity of dendrimeric formulation of AmB (MdPPIA) were compared with marketed formulations of AmB. Highly significant (P<0.01) reduction in toxicity was observed in hemolytic toxicity and cytotoxicity studies in erythrocytes and J774A.1 macrophage cells, respectively. Formulation MdPPIA showed appreciable macrophage targeting potential and higher or equivalent antiparasitic activity against parasite infected macrophage cell lines and in vivo infection in Balb/c mice. These results suggest the developed MDP conjugated dendrimeric formulation of AmB as a promising immunostimulant targeted drug delivery system and a safer alternative to marketed formulations. From the clinical editor: Parasitic infections remain a significant issue in the clinical setting. The authors in this article studied the use of ligand anchored dendrimeric formulation of Amphotericin B to target infected macrophages and showed reduced toxicity, high anti-leishmanial activity. This may add another treatment option to available formulations in the future.

Human beta casein fragment (54-59) modulates M. bovis BCG survival and basic transcription factor 3 (BTF3) expression in THP-1 cell line

Immunostimulatory peptides potentiate the immune system of the host and are being used as a viable adjunct to established therapeutic modalities in treatment of cancer and microbial infections. Several peptides derived from milk protein have been reported to induce immunostimulatory activity. Human β -casein fragment (54–59), natural sequence peptide (NS) carrying the Val-Glu-Pro-Ile-Pro-Tyr amino acid residues, was reported to activate the macrophages and impart potent immunostimulatory activity. In present study, we found that this peptide increases the clearance of M. bovis BCG from THP-1 cell line in vitro. The key biomolecules, involved in the clearance of BCG from macrophage like, nitric oxide, pro-inflammatory cytokines and chemokines, were not found to be significantly altered after peptide treatment in comparison to the untreated control. Using proteomic approach we found that BTF3a, an isoform of the Basic Transcription Factor, BTF3, was down regulated in THP-1 cell line after peptide treatment. This was reconfirmed by real time RT-PCR and western blotting. We report the BTF3a as a novel target of this hexapeptide. Based on the earlier findings and the results from the present studies, we suggest that the down regulation of BTF3a following the peptide treatment may augment the M. bovis BCG mediated apoptosis resulting in enhanced clearance of M. bovis BCG from THP-1 cell line.

Effect of Pam3Cys induced protection on the therapeutic efficacy of miltefosine against experimental visceral leishmaniasis

Prophylactic potential of synthetic bacterial lipopeptide and a TLR2 agonist, Pam3Cys was first evaluated against experimental visceral leishmaniasis in rodent model. After establishing the potential its effect on therapeutic efficacy of miltefosine was also studied. Pam3Cys showed 74.64% inhibition in parasitic establishment when administered by ip route at a dose of 100 μg/animal spaced at two weeks, i.e. on day -7 and +7 of challenge with Leishmania donovani amastigotes. However, when aforesaid dose of Pam3Cys was given with sub-curative dose of miltefosine (2.5 mg/kg for 5 days) its efficacy enhanced from 49.80% to 92.25%. These findings revealed that this lipopeptide has potential protective efficacy which significantly enhanced the therapeutic efficacy of miltefosine used at low dose against Leishmania infection and warrants detailed investigations on its possible immunopotentiatory actions.

Proteophosphoglycan is differentially expressed in sodium stibogluconate-sensitive and resistant Indian clinical isolates of Leishmania donovani

Leishmania produce several types of mucin-like glycoproteins called proteophosphoglycans (PPGs) some of which are secreted while others are found on the surface of promastigotes and amastigotes. These proteins are thought to be important in the transmission, invasion and subsequent intracellular survival of parasites. The structure and function of PPGs are species and stage-specific in the case of L. major and L. mexicana, but no such information has hitherto been available for L. donovani. This study presents, for the first time, an initial characterization (localization) of PPG in sodium stibogluconate (SSG)-resistant and sensitive clinical isolates of L. donovani from Bihar (India) by confocal microscopy, flow cytometry and Western blotting using antibodies to L. major PPG. Confocal microscopy analysis revealed that both promastigotes and amastigotes possess PPG on their cell membrane and flagellar pocket membrane but its expression was variable in different isolates. The quantitative analysis by FACS and Western blotting showed that the expression and intensity of PPG bands was higher in SSG-resistant isolates. This study suggests the possibilities of involvement of PPG in drug-resistant mechanisms and of using PPG abundance as a marker for identifying drug-resistant clinical isolates in Indian kala azar.

Antileishmanial potential of a marine sponge, Haliclona exigua (Kirkpatrick) against experimental visceral leishmaniasis

In this study, we are reporting antileishmanial activity of a marine sponge Haliclona exigua, belonging to phylum Porifera. The crude methanol extract and its three fractions were tested both in vitro and in vivo. The crude extract exerted almost complete inhibition of promastigotes at 50 microg/ml and 76.4 +/- 6.5% inhibition of intracellular amastigotes at 100 microg/ml concentration with IC50 values of 18.6 microg/ml and 47.2 microg/ml, respectively. When administered to Leishmania donovani infected hamsters at a dose of 500 mg/kg x 5, p.o., it resulted in 72.2 +/- 10.4% inhibition of intracellular amastigotes. At a lower dose (250 mg/kg), it exhibited 43.9 +/- 5.1% inhibition. Among the fractions, highest antileishmanial activity both in vitro (>90%) and in vivo (60.9 +/- 18.3%) was observed in n-butanol (soluble) fraction with IC50 values of 8.2 mug/ml and 31.2 microg/ml against promastigotes and intracellular amastigotes, respectively. Hexane fraction also showed comparatively good activity against both the stages of parasites in vitro but was moderately active in leishmania-infected hamsters. Chloroform fraction resulted in 45 +/- 10.2% inhibition in vivo at a dose of 500 mg/kg x 5, p.o., whereas it was inactive in vitro. n-Butanol (insoluble) fraction was inactive both in vitro and in vivo. Araguspongin C, an alkaloid isolated from n-butanol (soluble) fraction exhibited moderate inhibition of promastigotes and intracellular amastigotes at 100 microg/ml but showed weak antileishmanial action in vivo. Our findings indicate that this marine sponge has the potential to provide new lead toward development of an effective antileishmanial agent and, hence, calls for more exhaustive studies for exploiting the vast world of marine resources to combat the scourge of several parasitic diseases.

In vitro and in vivo leishmanicidal activity of Dysoxylum binectariferum and its fractions against Leishmania donovani

The leishmanicidal effect of crude ethanolic extract of stem bark of Dysoxylum binectariferum and its fractions has been investigated against Leishmania donovani, the causative agent of visceral leishmaniasis. Ethanolic extract was lethal to promastigotes as well as amastigote forms in macrophage system at the concentration of 100 microg/ml. Chloroform fraction significantly inhibited promastigote multiplication and was also active against amastigotes in infected J774A.1 macrophages at 100 microg/ml. Hexane fraction was moderately active and the other fractions were inactive against both the forms. When tested in vivo in hamsters, ethanolic extract was toxic at 500 mg/kg whereas exhibited marginal activity (67.7+/-5.3%) at 250 mg/kg x 5, p.o. on day 7 post treatment (p.t.) which increases slightly (69+/-4.7) by day 30 p.t. Chloroform and n-hexane fractions exhibited 64.3+/-4% and 47.8+/-4.6% parasite inhibition at the dose of 100 mg/kg x 5 p.o., respectively. The pure compound, rohitukine, obtained from chloroform fraction showed weaker in vitro activity and was ineffective in infected hamsters. The lead potential of this plant need further investigations.

Glycolipids and other constituents from Desmodium gangeticum with antileishmanial and immunomodulatory activities

Nineteen compounds of various classes, such as flavonoid glycosides, pterocarpanoids, lipids, glycolipids, and alkaloids, were isolated and identified from the Desmodium gangeticum whole plant. Aminoglucosyl glycerolipid (8) is reported here for the first time. Its structure has been elucidated by spectroscopic and degradation studies. This novel compound exhibited in vitro antileishmanial and immunomodulatory activities, as it enhanced nitric oxide (NO) production and provided resistance against infection established in peritoneal macrophages by the protozoan parasite Leishmania donovani. Another known compound, glycosphingolipid (cerebroside) (7) was found to possess significant in vitro antileishmanial and immunomodulatory activities against the same parasite. Other compounds were found to be inactive.

Efficacy of Desmodium gangeticum extract and its fractions against experimental visceral leishmaniasis

Crude ethanolic extract of Indian medicinal plant, Desmodium gangeticum (A001) and its three fractions-hexane (F002), n-butanol (F003) and aqueous (F004) were evaluated chemoprophylactically and chemotherapeutically against experimental visceral leishmaniasis in hamsters. Ethanolic extract showed 41.2+/-5.3% inhibition of parasite multiplication when administered at a dose of 250 mg/kgx2 on day -7 and +7 of Leishmania donovani challenge. Its n-butanol fraction exhibited better efficacy than the ethanolic extract to the tune of 66.7+/-6.1% inhibition when administered at similar dose schedule. But the other two fractions failed to exert any action prophylactically. F003 also imparted significant (P<0.001) non-specific resistance to peritoneal macrophages against Leishmania infection. F003 also showed moderate antileishmanial activity when tested against established infection of Leishmania donovani in hamsters but the rest three fractions failed to show any significant inhibition of parasite multiplication. These findings revealed that this plant has potential prophylactic and therapeutic efficacy against Leishmania infection and warrants detailed investigations on its possible immunopotentiatory actions.