The regulatory role of vitamin D receptor (VDR) gene variants of Bsm I, Apa I, Taq I, and Fok I polymorphisms on vitamin D(3)-modulated macrophage phagocytosis with live Mycobacterium tuberculosis and lymphoproliferative response to M. tuberculosis culture filtrate antigen (CFA) was studied in patients with pulmonary tuberculosis (n = 46) and in normal healthy subjects (NHS) (n = 64). Vitamin D(3) at a concentration of 1 x 10(-7) M enhanced the phagocytic potential of normal subjects who had a phagocytic index of less than 20%. This increase was seen in subjects with the genotypes BB (p = 0.017), AA (p = 0.016), tt (p = 0.034), and FF (p = 0.013) and the extended genotype BBAAtt (p = 0.034). Normal subjects with BBAAtt performed better phagocytosis than individuals with bbaaTT genotype (p = 0.034). Vitamin D(3) at 10(-9), 10(-8), and 10(-7) M concentrations suppressed the lymphoproliferative response to CFA antigen in normal subjects. This decreased lymphocyte response was observed in normal individuals with the genotypes BB (p = 0.0009), tt (p = 0.016), and FF (p = 0.008) and the extended genotype BBAAtt (p = 0.02). Addition of vitamin D(3) had no significant effect on macrophage phagocytosis and lymphoproliferative response to CFA in pulmonary TB patients. This may be due to the unresponsive nature of the cells to the action of vitamin D(3) or the downregulated VDR expression by virtue of the disease, which renders them inactive. The genotypes BB, tt, and the extended genotype BBAAtt may be associated with increased expression of VDR which in turn regulate the action of vitamin D(3) and modulate the immune functions to M. tuberculosis in NHS.

The in vitro activity of paromomycin and miltefosine against host cells is TLR4 dependent. This has implications for: (i) evaluation of in vitro activity of combinational antileishmanial therapy; (ii) the evaluation of drug susceptibility of clinical isolates; and (iii) the standardization of in vitro antileishmanial assays for determining toxicity in hosts.

BACKGROUND AND PURPOSEThe combination of paromomycin-miltefosine is a successful anti-leishmanial therapy in visceral leishmaniasis (VL). This encouraged us to study its effect on Toll-like receptor (TLR)-mediated immunomodulation of dendritic cells (DC), as DC maturation and activation is crucial for anti-leishmanial activity. EXPERIMENTAL APPROACHIn silico protein-ligand interaction and biophysical characterization of TLR9-drug interaction was performed. Interaction assays of HEK293 cells with different concentrations of miltefosine and/or paromomycin were performed, and NF-κB promoter activity measured. The role of TLR9 and MyD88 in paromomycin/miltefosine-induced maturation and activation of DCs was evaluated through RNA interference techniques. The effect of drugs on DCs was measured in terms of counter-regulatory production of IL-12 over IL-10, and characterized by chromatin immunoprecipitation assay at the molecular level. KEY RESULTSComputational and biophysical studies revealed that paromomycin/miltefosine interact with TLR9. Both drugs, as a monotherapy/combination, induced TLR9-dependent NF-κB promoter activity through MyD88. Moreover, the drug combination induced TLR9/MyD88-dependent functional maturation of DCs, evident as an up-regulation of co-stimulatory markers, enhanced antigen presentation by increasing MHC II expression, and increased stimulation of naive T-cells to produce IFN-γ. Both drugs, by modifying histone H3 at the promoter level, increased the release of IL-12, but down-regulated IL-10 in a TLR9-dependent manner. CONCLUSIONS AND IMPLICATIONSThese results provide the first evidence that the combination of paromomycin-miltefosine critically modifies the maturation, activation and development of host DCs through a mechanism dependent on TLR9 and MyD88. This has implications for evaluating the success of other combination anti-leishmanial therapies that act by targeting host DCs.

As drug resistance problem persists in case of Leishmaniasis, modeling and analysis of different essential proteins of Leishmania strains will help us further to discover novel lead compounds. Lipophosphoglycan 2 (LPG2) protein is required for the development of Leishmania throughout their life cycle, including for virulence to the mammalian host. LPG2 participates in a specialized virulence pathway, which may offer an attractive target for chemotherapy. Homology models of LPG2 of five Leishmania species have been constructed using the X-ray structures of different transporter proteins as templates, by comparative protein modeling principles. The resulting model has the correct stereochemistry as gauged from the Ramachandran plot and good three-dimensional (3-D) structure compatibility as assessed by the Procheck and Profiles-3D scores. Functional assignment of LPG2 protein of Leishmania strains by SVM revealed that along with transporters activity it also performs several novel functions e.g. iron-binding, sodium-binding, copper binding. It also belongs to protein of major facilitator family (MFS) and type II (general) secretory pathway (IISP) family. Important functional motifs have been identified in LPG2 protein of different Leishmania strains using different programs. Potential Ligand Binding Sites (LBSs) in LPG2 protein of these strains have been identified using Pocket Finder program. On the basis of structure of ligand binding sites, particular LPG2 inhibitors can be designed. The similarity in the molecular structure, function and differences in LBSs of LPG2 of L. donovani, L. major, L. infantum, L. braziliensis and L. mexicana provide evidences for selective and specific LPG2 inhibitors.