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

A new polysaccharide from fruit bodies of Morchella elata: Chemical structure and immunomodulation abilities

A new polysaccharide (MEPS, Morchella elata polysaccharide) obtained through alkali extraction from fruit bodies of Morchella elata was purified by dialysis and sepharose-6B column chromatography. Chemical and spectroscopic analysis including GLC, GLC-MS, FT-IR, 1D NMR (1H, 13C, DEPT-135) and 2D NMR (TOCSY, HMQC, NOESY, DQF, ROESY, and HMBC) revealed that the backbone of its repeating unit was →6)-β-d-Manp-(1 → 3)-α-d-Glcp-(1 → 4)-α-d-Glcp-(1→, branched at C-3 of (1 → 4)-linked- α-d-Glcp by α-d-Manp-(1 → 4)-α-d-Glcp-(1 → 4)-α-d-Galp-(1 → . It was also found that a terminal β-l-fucopyranosyl residue was attached at C-3 of α-d-glucopyranosyl residue of the branched chain. In vitro evaluation of immune modulation of the polysaccharide revealed the significant macrophage polarizing properties and capability to induce an alternative phenotype M2 in peritoneal macrophages obtained from BALB/c mice. It was further confirmed by the ability to induce the expression of M2 polarizing cytokines, specifically IL-10.

Inverse correlation between Leishmania-induced TLR1/2 and TGF-β differentially regulates parasite persistence in bone marrow during the chronic phase of infection

Host-tissue preference is a critical aspect of parasitic infections and is directly correlated with species diversity. Even the same species, Leishmania donovani, infects the host's bone marrow, spleen, and liver differentially. The tissue-specific persistence of Leishmania results from host-pathogen immune conflicts and arguments. The protective pro-host or destructive pro-parasitic role of TLRs during L. donovani infection has been well established, but what entirely missing is the influence of TLRs on tissue-specific parasite persistence. We observed that the parasites induced differential expression of TLR1/2 in the bone marrow but not in the spleen. Interestingly, the rate of Leishmania infection was found to be positively correlated with TLR1/2-mediated upregulation of myelopoietic cytokines, M-CSF, GM-CSF, IL-6, and IL-3, leading to the expansion of Ly6ChiCCR2+ monocytes, however, negatively correlated with the expression of the disease hallmark cytokines, TNF-α, TGF-β, and IL-10, along the course of infection in the bone marrow. Leishmania induced the activation of bone marrow-specific TLR1/2 to promote Ly6ChiCCR2+ monocytes for its safe shelter vis-à-vis infection establishment. Consequently, the established infection initiated the release of TNF-α, TGF-β, and IL-10 in the bone marrow. Post-infection time-kinetic study affirmed that TGF-β had a significant negative influence on the expression of TLR1/2 heterodimer in the bone marrow niche. To the best of our knowledge, this is the first report to show that the inverse correlation of TLR1/2 - TGF-β can be instrumental in tissue-specific parasite persistence during Leishmania infection.

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.

Exploring the paradox of defense between host and Leishmania parasite

Leishmaniasis, a neglected tropical disease, still remains a global concern for the healthcare sector. The primary causative agents of the disease comprise diverse leishmanial species, leading to recurring failures in disease diagnosis and delaying the initiation of appropriate chemotherapy. Various species of the Leishmania parasite cause diverse clinical manifestations ranging from skin ulcers to systemic infections. Therefore, host immunity in response to different forms of infecting species of Leishmania becomes pivotal in disease progression or regression. Thus, understanding the paradox of immune arsenals during host and parasite interface becomes crucial to eliminate this deadly disease. In the present review, we have elaborated on the immunological perspectives of the disease and discussed primary host immune cells that form a defense line to counteract parasite infection. Furthermore, we also have shed light on the immune cells and effector molecules responsible for parasite survival in host lethal milieu/ environment. Next, we have highlighted recent molecules/compounds showing potent leishmanicidal activities pertaining to their pro-oxidant and immuno-modulatory mechanisms. This review addresses an immuno-biological overview of the factors influencing the parasitic disease, as this knowledge can aid in the unraveling/ identification of potential biomarkers, novel therapeutics, and vaccine candidates against leishmaniasis.