Leishmania donovani Metacyclic Promastigotes Impair Phagosome Properties in Inflammatory Monocytes

Abstract

Leishmaniasis, a debilitating disease with clinical manifestations ranging from self-healing ulcers to life-threatening visceral pathologies, is caused by protozoan parasites of the Leishmania genus. These professional vacuolar pathogens are transmitted by infected sand flies to mammalian hosts as metacyclic promastigotes and are rapidly internalized by various phagocyte populations. Classical monocytes are among the first myeloid cells to migrate to infection sites. Recent evidence shows that recruitment of these cells contributes to parasite burden and to the establishment of chronic disease. However, the nature of Leishmania-inflammatory monocyte interactions during the early stages of host infection has not been well investigated. Here, we aimed to assess the impact of Leishmania donovani metacyclic promastigotes on antimicrobial responses within these cells. Our data showed that inflammatory monocytes are readily colonized by L. donovani metacyclic promastigotes, while infection with Escherichia coli is efficiently cleared. Upon internalization, metacyclic promastigotes inhibited superoxide production at the parasitophorous vacuole (PV) through a mechanism involving exclusion of NADPH oxidase subunits gp91phox and p47phox from the PV membrane. Moreover, we observed that unlike phagosomes enclosing zymosan particles, vacuoles containing parasites acidify poorly. Interestingly, whereas the parasite surface coat virulence glycolipid lipophosphoglycan (LPG) was responsible for the inhibition of PV acidification, impairment of the NADPH oxidase assembly was independent of LPG and GP63. Collectively, these observations indicate that permissiveness of inflammatory monocytes to L. donovani may thus be related to the ability of this parasite to impair the microbicidal properties of phagosomes.

Leishmania infantum Defective in Lipophosphoglycan Biosynthesis Interferes With Activation of Human Neutrophils

“…Here, we investigated whether LPG interferes in a similar mechanism to protect L. infantum promastigotes within parasitophorous vacuoles in human neutrophils. Our observation that ∆lpg1 L. infantum parasites, but not WT, are found within acidified parasitophorous vacuoles is consistent with previously reported findings demonstrating that LPG prevents phagolysosome biogenesis and acidification ( Desjardins and Descoteaux, 1997 ; Dermine et al., 2000 ; Gueirard et al., 2008 ; Vinet et al., 2009 ; da Silva Vieira et al., 2019 ; Matte et al., 2021 ). To confirm the role of acidified compartments in the killing of ∆lpg1 L. infantum , we performed a viability assay in the presence of Wortmannin, an inhibitor of vesicle fusion and phagolysosome formation ( Tavares et al., 2016 ).…”

“…Leishmania ’s LPG is thought to inhibit the maturation of vacuoles in which they are contained by blocking recruitment of the v-ATPase and acidification ( Vinet et al., 2009 ; Matte et al., 2021 ) and assembly of the NADPH oxidase ( Lodge et al., 2006 ). The blockage of phagosome acidification inhibits action of ROS.…”

Addressing anemia severity in antimony-resistantLeishmania donovaniinfection at the nexus of oxidative outburst and iron transit

“…Primary reducing equivalents, NADPH have been widely reported previously to neutralize intracellular ROS by donating reductive potentials to glutathione and thioredoxins (33). As maximum ROS generation was observed in 2-4hrs pi when LD persists as intracellular promastigotes in early PV (5), intrinsic NAPDH level was compared between metacyclic LD-S and LD-R ( Figure 2D, and 2D inset ). HPLC-based quantification of NADPH/ NADP+ in LD-S and LD-R suggests that the NADPH/NADP+ ratio is significantly higher in LD-R as compared to LD-S at a retention time of around 1.5-2mins.…”

Macrophage Mitochondrial Biogenesis and Metabolic Reprogramming Induced by Leishmania donovani Require Lipophosphoglycan and Type I Interferon Signaling

“…Female HsdHan:AURA hamsters of 4 to 6 weeks of age were purchased from Harlan Sprague Dawley, Inc. Promastigotes of L. donovani (MHOM/ET/67/Hu3:LV9), L. major NIHS (MHOM/SN/74/Seidman), L. amazonensis LV79 (MPRO/BR/72/M 1841), and L. mexicana (MNYC/BZ/62/M379) were cultured in Leishmania medium (M199 medium supplemented with 10% heat-inactivated fetal bovine serum [FBS] [HyClone], 100 μM hypoxanthine, 10 mM HEPES, 5 μM hemin, 3 μM biopterin, 1 μM biotin, penicillin [100 U/mL], and streptomycin [100 μg/mL]) at 26°C. The isogenic L. donovani Δ lpg1 mutant ( 71 ) was cultured in M199 medium supplemented with hygromycin (100 μg/mL), and its complemented counterpart L. donovani Δ lpg1 + LPG1 ( 71 ) was cultured in M199 medium supplemented with hygromycin (100 μg/mL) and zeocin (100 μg/mL). Amastigotes of L. donovani (MHOM/ET/67/Hu3:LV9) were isolated from the spleens of hamsters infected 8 to 12 weeks earlier with 1.5 × 10 8 amastigotes by intraperitoneal inoculation ( 94 ).…”