Activation of neutrophils excels the therapeutic potential of Mycobacterium indicus pranii and heat-induced promastigotes against antimony-resistant Leishmania donovani infection.

Repurposing drugs and adjuvants is an attractive choice of present therapy that reduces the substantial costs, chances of failure, and systemic toxicity. Mycobacterium indicus pranii was originally developed as a leprosy vaccine but later has been found effective against Leishmania donovani infection. To extend our earlier study, here we reported the immunotherapeutic modulation of the splenic and circulatory neutrophils in favour of hosts as neutrophils actually serve as the pro-parasitic portable shelter to extend the Leishmania infection specifically during the early entry into the hosts' circulation. We targeted to disrupt this early pro-parasitic incidence by the therapeutic combination of M. indicus pranii and heat-induced promastigotes against antimony-resistant L. donovani infection. The combination therapy induced the functional expansion of CD11b+Ly6CintLy6Ghi neutrophils both in the post-infected spleen, and also in the circulation of post-treated animals followed by the immediate Leishmania infection. More importantly, the enhanced expression of MHC-II, phagocytic uptake of the parasites by the circulatory neutrophils as well as the oxidative burst were induced that limited the chances of the very early establishment of the infection. The enhanced expression of pro-inflammatory cytokines, like IL-1α and TNF-α indicated resistance to the parasite-mediated takeover of the neutrophils, as these cytokines are critical for the activation of T cell-mediated immunity and host-protective responses. Additionally, the induction of essential transcription factors and cytokines for early granulocytic lineage commitment suggests that the strategy not only contributed to the peripheral activation of the neutrophils but also promoted granulopoiesis in the bone marrow.

Leishmania LPG interacts with LRR5/LRR6 of macrophage TLR4 for parasite invasion and impairs the macrophage functions.

Visceral leishmaniasis (VL) is a severe form of leishmaniasis, primarily affecting the poor in developing countries. Although several studies have highlighted the importance of toll-like receptors (TLRs) in the pathophysiology of leishmaniasis, the role of specific TLRs and their binding partners involved in Leishmania donovani uptake are still elusive. To investigate the mechanism of L. donovani entry inside the macrophages, we found that the parasite lipophosphoglycan (LPG) interacted with the macrophage TLR4, leading to parasite uptake without any significant alteration of macrophage cell viability. Increased parasite numbers within macrophages markedly inhibited lipopolysachharide-induced pro-inflammatory cytokines gene expression. Silencing of macrophage-TLR4, or inhibition of parasite-LPG, significantly stemmed parasite infection in macrophages. Interestingly, we observed a significant enhancement of macrophage migration, and generation of reactive oxygen species (ROS) in the parasite-infected TLR4-silenced macrophages, whereas parasite infection in TLR4-overexpressed macrophages exhibited a notable reduction of macrophage migration and ROS generation. Moreover, mutations in the leucine-rich repeats (LRRs), particularly LRR5 and LRR6, significantly prevented TLR4 interaction with LPG, thus inhibiting cellular parasite entry. All these results suggest that parasite LPG recognition by the LRR5 and LRR6 of macrophage-TLR4 facilitated parasite entry, and impaired macrophage functions. Therefore, targeting LRR5/LRR6 interactions with LPG could provide a novel option to prevent VL.

Black carbon health impacts in the Indo-Gangetic plain: Exposures, risks, and mitigation.

A large discrepancy between simulated and observed black carbon (BC) surface concentrations over the densely populated Indo-Gangetic plain (IGP) has so far limited our ability to assess the magnitude of BC health impacts in terms of population exposure, morbidity, and mortality. We evaluate these impacts using an integrated modeling framework, including successfully predicted BC concentrations. Population exposure to BC is notable, with more than 60 million people identified as living in hotspots of BC concentration (wintertime mean, >20 µg m-3). The attributable fraction of the total cardiovascular disease mortality (CVM) burden to BC exposures is 62% for the megacity. The semiurban area comprised about 49% of the total BC-attributable CVM burden over the IGP. More than 400,000 lives can potentially be saved from CVM annually by implementing prioritized emission reduction from the combustion of domestic biofuel in the semiurban area, diesel oil in transportation, and coal in thermal power plant and brick kiln industries in megacities.

Deletion of Glutamine Synthetase Gene Disrupts the Survivability and Infectivity of Leishmania donovani.

Glutamine synthetase (GS) is one of the most important metabolic enzymes which catalyzes ligation of glutamate and ammonia to form glutamine. Previous studies from our lab had revealed significant differences in parasite and host GS enzyme which warranted us to further work on its relevance in parasite. To analyze glutamine synthetase function in Leishmania, we generated GS overexpressors and knockout mutants and evaluated their ability to grow in vitro in monocyte differentiated macrophage and in vivo by infections in BALB/c mice. GS knocked out strain showed significant growth retardation with delayed cell cycle progression and morphological alteration. Null mutants exhibited attenuated infectivity both in in vitro and in vivo experiments and the effect was reverted back when infected with GS complemented parasites. This indicated that the alterations in phenotype observed were indeed due to GS knockout. GS knockout also made the parasite increasingly sensitive to Miltefosine. Detailed investigation of mode of parasite death upon Miltefosine treatment by dual staining with Annexin-V conjugated FITC and propidium iodide, pointed towards apoptotic or necrotic mode of cell death. This is the first report to confirm that GS is essential for the survivability and infectivity of Leishmania donovani, and can be exploited as a potential drug-target.

Cytokines in the generation and function of regulatory T cell subsets in leishmaniasis.

CD4+ T regulatory cells (Tregs) are a group of T lymphocytes that maintain self-tolerance and protect the host from inflammation-induced tissue damage. An interacting network of cytokines and transcription factors influence the origin, differentiation, and function of the Tregs in primary and secondary lymphoid organs. However, following antigenic stimulation, it can also be induced at the sites of infection. Immune cell resident microbial pathogens, such as Leishmania, employ varieties of mechanisms to promote the suppressive functions of Tregs for protective evasion from the host immune system. This establishes a state of immune unresponsiveness in the host, exacerbating the disease in Leishmania infection. Elimination of Leishmania pathogens is accomplished with a strong pro-inflammatory response accompanied by the release of host protective cytokines such as Interleukin-2 (IL-2), Interferon-gamma (IFN-γ), and Tumor necrosis factor-alpha (TNF-α), which functions through suppression of Tregs or making the effector cells recalcitrant to Treg mediated suppression. Nevertheless, during chronic infection, the persistence of unwarranted pro-inflammatory cytokines can trigger self-tissue damage. Tregs limit the consequence of chronic inflammation to restrict self-harm suggesting its mutually opposing role in host protection. Furthermore, Tregs function to prevent complete parasite clearance to provide long-term immunity to re-infection. This review summarizes the roles of pro-inflammatory and anti-inflammatory cytokines involved in the homing, activation, differentiation, and suppression of Tregs in the course of Leishmania infection. We also suggest cytokines that can be modulated as potential therapeutic targets to treat Leishmania infection.

Silver linings in the dark clouds of COVID-19: Improvement of air quality over India and Delhi metropolitan area from measurements and WRF-CHIMERE model simulations.

The current study examines the impact of the COVID-19 lockdown (25th March until May 17, 2020) period in particulate matter (PM) concentrations and air pollutants (NOx, SO2, CO, NH3, and O3) at 63 stations located at Delhi, Uttar Pradesh and Haryana states within the Delhi-NCR, India. Large average reductions are recorded between the stations in each state such as PM10 (-46 to -58%), PM2.5 (-49 to -55%), NO2 (-27 to -58%), NO (-54% to -59%), CO (-4 to -44%), NH3 (-2 to -38%), while a slight increase is observed for O3 (+4 to +6%) during the lockdown period compared to same periods in previous years. Furthermore, PM and air pollutants are significantly reduced during lockdown compared to the respective period in previous years, while a significant increase in pollution levels is observed after the re-opening of economy. The meteorological changes were rather marginal between the examined periods in order to justify such large reductions in pollution levels, which are mostly attributed to traffic-related pollutants (NOx, CO and road-dust PM). The WRF-CHIMERE model simulations reveal a remarkable reduction in PM2.5, NO2 and SO2 levels over whole Indian subcontinent and mostly over urban areas, due to limitation in emissions from the traffic and industrial sectors. A PM2.5 reduction of -48% was simulated in Delhi in great consistency with measurements, rendering the model as a powerful tool for simulations of lower pollution levels during lockdown period.

A mushroom derived 'carbohydrate-fraction' reinstates host-immunity and protects from Leishmania donovani infection.

The anti-leishmanial effect of the 'carbohydrate-fraction', isolated from an edible mushroom Astraeus hygrometricus, was evaluated against Leishmania donovani infection both in vitro and in vivo. Ahf-Car induced the expression of inducible nitric oxide synthase 2 (iNOS2) and pro-inflammatory cytokines like TNF-α and IL-12, with subsequent downregulation of the anti-inflammatory cytokines as TGF-ß and IL-10, in vitro and in vivo along with a remarkable increase in the expressions of IL-6, IL-1ß, IFN-γ and IRFs, IRF-7 and IRF-8 in vivo. Ahf-Car also reduced the parasite burden in the spleen and liver dose-dependently with a simultaneous proliferation of Ly6C+ cells in the bone marrow of Leishmania-infected experimental animals. It also increased the monocyte population dose-dependently and the expression of the myeloid transcription factor PU.1, in vivo, which presumably signifies the expansion of protective macrophages. Thus, Ahf-Car might be a potent anti-leishmanial lead with unique and effective adjuvant capacity.

Multi-frequency EPR studies of a mononuclear holmium single-molecule magnet based on the polyoxometalate [Ho(III)(W5O18)2]9-.

Continuous-wave, multi-frequency electron paramagnetic resonance (EPR) studies are reported for a series of single-crystal and powder samples containing different dilutions of a recently discovered mononuclear Ho(III) (4f(10)) single-molecule magnet (SMM) encapsulated in a highly symmetric polyoxometalate (POM) cage. The encapsulation offers the potential for applications in molecular spintronics devices, as it preserves the intrinsic properties of the nanomagnet outside of the crystal. A significant magnetic anisotropy arises due to a splitting of the Hund's coupled total angular momentum (J = L + S = 8) ground state in the POM ligand field. Thus, high-frequency (50.4 GHz) EPR studies reveal a highly anisotropic eight line spectrum corresponding to transitions within the lowest m(J) = ±4 doublet, split by a strong hyperfine interaction with the I = 7/2 Ho nucleus (100% natural abundance). X-band EPR studies reveal the presence of an appreciable tunneling gap between the m(J) = ±4 doublet states having the same nuclear spin projection, leading to a highly non-linear field-dependence of the spectrum at low-frequencies.