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Author: Donna Huber

Dennis Kyle Featured Guest on People, Parasites & Plagues Podcast

Dr. Dennis Kyle, director of CTEGD and professor in the departments of cellular biology and infectious diseases, is the featured guest on Episode 5 of the People, Parasites & Plagues Podcast. He talks about a deadly disease caused by Naegleria fowleri, also known as the brain-eating amoeba.

The podcast is also available at AmazoniTunesGoogleSpotifyStitcherAudible, and TuneIn

People, Parasites & Plagues is a podcast aimed at delivering information about the fascinating pathogens among us from the impressive professionals who study them.

Join hosts Dr. David Peterson and Dr. Liliana Salvador, two infectious disease researchers from the University of Georgia, as they explore the past, present, and future of science.

Tune in every other week for a new and enlightening episode as they unpack the details surrounding some of Earth’s most perplexing diseases. Look for the People, Parasites & Plagues Podcast on your favorite Podcast service!

Trypanosoma cruzi Letm1 is involved in mitochondrial Ca 2+ transport, and is essential for replication, differentiation, and host cell invasion

Leucine zipper-EF-hand containing transmembrane protein 1 (Letm1) is a mitochondrial inner membrane protein involved in Ca2+ and K+ homeostasis in mammalian cells. Here, we demonstrate that the Letm1 orthologue of Trypanosoma cruzi, the etiologic agent of Chagas disease, is important for mitochondrial Ca2+ uptake and release. The results show that both mitochondrial Ca2+ influx and efflux are reduced in TcLetm1 knockdown (TcLetm1-KD) cells and increased in TcLetm1 overexpressing cells, without alterations in the mitochondrial membrane potential. Remarkably, TcLetm1 knockdown or overexpression increases or does not affect mitochondrial Ca2+ levels in epimastigotes, respectively. TcLetm1-KD epimastigotes have reduced growth, and both overexpression and knockdown of TcLetm1 cause a defect in metacyclogenesis. TcLetm1-KD also affected mitochondrial bioenergetics. Invasion of host cells by TcLetm1-KD trypomastigotes and their intracellular replication is greatly impaired. Taken together, our findings indicate that TcLetm1 is important for Ca2+ homeostasis and cell viability in T cruzi.

Guilherme Rodrigo Rm Dos Santos, Ana Catarina Rezende Leite, Noelia Lander, Miguel Angel Chiurillo, Aníbal Eugênio Vercesi, Roberto Docampo. FASEB J. 2021 Jul;35(7):e21685. doi: 10.1096/fj.202100120RR

Lacto-N-fucopentaose-III ameliorates acute and persisting hippocampal synaptic plasticity and transmission deficits in a Gulf War Illness mouse model

Aims: The present study investigated if treatment with the immunotherapeutic, lacto-N-fucopentaose-III (LNFPIII), resulted in amelioration of acute and persisting deficits in synaptic plasticity and transmission as well as trophic factor expression along the hippocampal dorsoventral axis in a mouse model of Gulf War Illness (GWI).

Main methods: Mice received either coadministered or delayed LNFPIII treatment throughout or following, respectively, exposure to a 15-day GWI induction paradigm. Subsets of animals were subsequently sacrificed 48 h, seven months, or 11 months post GWI-related (GWIR) exposure for hippocampal qPCR or in vitro electrophysiology experiments.

Key findings: Progressively worsened impairments in hippocampal synaptic plasticity, as well as a biphasic effect on hippocampal synaptic transmission, were detected in GWIR-exposed animals. Dorsoventral-specific impairments in hippocampal synaptic responses became more pronounced over time, particularly in the dorsal hippocampus. Notably, delayed LNFPIII treatment ameliorated GWI-related aberrations in hippocampal synaptic plasticity and transmission seven and 11 months post-exposure, an effect that was consistent with enhanced hippocampal trophic factor expression and absence of increased interleukin 6 (IL-6) in animals treated with LNFPIII.

Significance: Approximately a third of Gulf War Veterans have GWI; however, GWI therapeutics are presently limited to targeted and symptomatic treatments. As increasing evidence underscores the substantial role of persisting neuroimmune dysfunction in GWI, efficacious neuroactive immunotherapeutics hold substantial promise in yielding GWI remission. The findings in the present report indicate that LNFPIII may be an efficacious candidate for ameliorating persisting neurological abnormalities presented in GWI.

Kyle A Brown, Jessica M Carpenter, Collin J Preston, Helaina D Ludwig, Kendall B Clay, Donald A Harn, Thomas Norberg, John J Wagner, Nikolay M Filipov. Life Sci. 2021 Jun 5;119707. doi: 10.1016/j.lfs.2021.119707

Lack of detectable short-term effects of a single dose of ivermectin on the human immune system

Background: Ivermectin is widely used in human and animal medicine to treat and prevent parasite nematode infections. It has been suggested that its mode of action requires the host immune system, as it is difficult to reproduce its clinical efficacy in vitro. We therefore studied the effects of a single dose of ivermectin (Stromectol®-0.15 mg/kg) on cytokine levels and immune cell gene expression in human volunteers. This dose reduces bloodstream microfilariae rapidly and for several months when given in mass drug administration programmes.

Methods: Healthy volunteers with no travel history to endemic regions were given 3-4 tablets, depending on their weight, of either ivermectin or a placebo. Blood samples were drawn immediately prior to administration, 4 h and 24 h afterwards, and complete blood counts performed. Serum levels of 41 cytokines and chemokines were measured using Luminex® and expression levels of 770 myeloid-cell-related genes determined using the NanoString nCounter®. Cytokine levels at 4 h and 24 h post-treatment were compared to the levels pre-treatment using simple t tests to determine if any individual results required further investigation, taking p = < 0.05 as the level of significance. NanoString data were analysed on the proprietary software, nSolver™.

Results: No significant differences were observed in complete blood counts or cytokine levels at either time point between people given ivermectin versus placebo. Only three genes showed a significant change in expression in peripheral blood mononuclear cells 4 h after ivermectin was given; there were no significant changes 24 h after drug administration or in polymorphonuclear cells at either time point. Leukocytes isolated from those participants given ivermectin showed no difference in their ability to kill Brugia malayi microfilariae in vitro.

Conclusions: Overall, our data do not support a direct effect of ivermectin, when given at the dose used in current filarial elimination programmes, on the human immune system. Trial registration NCT03459794 Registered 9th March 2018, Retrospectively registered .

Natalie E Wilson, Barbara J Reaves, Adrian J Wolstenholme. Parasit Vectors. 2021 Jun 5;14(1):304. doi: 10.1186/s13071-021-04810-6.

Immune exhaustion in chronic Chagas disease: Pro-inflammatory and immunomodulatory action of IL-27 in vitro

In chronic Chagas disease, Trypanosoma cruzi-specific T-cell function decreases over time, and alterations in the homeostatic IL-7/IL-7R axis are evident, consistent with a process of immune exhaustion. IL-27 is an important immunoregulatory cytokine that shares T-cell signaling with IL-7 and other cytokines of the IL-12 family and might be involved in the transcriptional regulation of T-cell function. Here, we evaluated the expression and function of IL-27R in antigen-experienced T cells from subjects with chronic Chagas disease and assessed whether in vitro treatment with IL-27 and IL-7 might improve T. cruzi-specific polyfunctional T-cell responses. In vitro exposure of PBMCs to T. cruzi induced a downregulation of IL-27R in CD4+ T cells and an upregulation in CD8+ T cells in subjects without heart disease, while IL-27R expression remained unaltered in subjects with more severe clinical stages. The modulation of IL-27R was associated with functional signaling through STAT3 and STAT5 and induction of the downstream genes TBX21, EOMES and CXCL9 in response to IL-27. In vitro treatment of PBMCs with IL-27 and IL-7 improved monofunctional and polyfunctional Th1 responses, accompanied by the induction of IL-10 and Bcl-2 expression in subjects without heart disease but did not improve those in subjects with cardiomyopathy. Our findings support the process of desensitization of the IL-27/IL-27R pathway along with disease severity and that the pro-inflammatory and immunomodulatory mechanisms of IL-27 might be interconnected.

María Ailén Natale, Todd Minning, María Cecilia Albareda, Melisa Daiana Castro Eiro, María Gabriela Álvarez, Bruno Lococo, Gonzalo Cesar, Graciela Bertocchi, María Josefina Elias, María Belén Caputo, Rick Lee Tarleton, Susana Adriana Laucella. PLoS Negl Trop Dis. 2021 Jun 1;15(6):e0009473. doi: 10.1371/journal.pntd.0009473.

TbVps41 regulates trafficking of endocytic but not biosynthetic cargo to lysosomes of bloodstream forms of Trypanosoma brucei

The bloodstream stage of Trypanosoma brucei, the causative agent of African trypanosomiasis, is characterized by its high rate of endocytosis, which is involved in remodeling of its surface coat. Here we present evidence that RNAi-mediated expression down-regulation of vacuolar protein sorting 41 (Vps41), a component of the homotypic fusion and vacuole protein sorting (HOPS) complex, leads to a strong inhibition of endocytosis, vesicle accumulation, enlargement of the flagellar pocket (“big eye” phenotype), and dramatic effect on cell growth. Unexpectedly, other functions described for Vps41 in mammalian cells and yeasts, such as delivery of proteins to lysosomes, and lysosome-related organelles (acidocalcisomes) were unaffected, indicating that in trypanosomes post-Golgi trafficking is distinct from that of mammalian cells and yeasts. The essentiality of TbVps41 suggests that it is a potential drug target.

Srinivasan Ramakrishnan, Rodrigo P Baptista, Beejan Asady, Guozhong Huang, Roberto Docampo. FASEB J. 2021 Jun;35(6):e21641. doi: 10.1096/fj.202100487R

Belen Cassera Featured on People, Parasites and Plagues Podcast

Dr. Belen Cassera is the featured guest on Episode 4 of the People, Parasites & Plagues Podcast. She discusses the development of new drugs to treat and prevent malaria, one of the deadliest diseases afflicting humankind.

The podcast is also available at Amazon, iTunes, Google, Spotify, Stitcher, Audible, and TuneIn

People, Parasites & Plagues is a podcast aimed at delivering information about the fascinating pathogens among us from the impressive professionals who study them.

Join hosts Dr. David Peterson and Dr. Liliana Salvador, two infectious disease researchers from the University of Georgia, as they explore the past, present, and future of science.

Tune in every other week for a new and enlightening episode as they unpack the details surrounding some of Earth’s most perplexing diseases. Look for the People, Parasites & Plagues Podcast on your favorite Podcast service!

A Comparison of Two Structurally Related Human Milk Oligosaccharide Conjugates in a Model of Diet-Induced Obesity

Obesity is the largest risk factor for the development of chronic diseases in industrialized countries. Excessive fat accumulation triggers a state of chronic low-grade inflammation to the detriment of numerous organs. To address this problem, our lab has been examining the anti-inflammatory mechanisms of two human milk oligosaccharides (HMOs), lacto-N-fucopentaose III (LNFPIII) and lacto-N-neotetraose (LNnT). LNFPIII and LNnT are HMOs that differ in structure via presence/absence of an α1,3-linked fucose. We utilize LNFPIII and LNnT in conjugate form, where 10-12 molecules of LNFPIII or LNnT are conjugated to a 40 kDa dextran carrier (P3DEX/NTDEX). Previous studies from our lab have shown that LNFPIII conjugates are anti-inflammatory, act on multiple cell types, and are therapeutic in a wide range of murine inflammatory disease models. The α1,3-linked fucose residue on LNFPIII makes it difficult and more expensive to synthesize. Therefore, we asked if LNnT conjugates induced similar therapeutic effects to LNFPIII. Herein, we compare the therapeutic effects of P3DEX and NTDEX in a model of diet-induced obesity (DIO). Male C57BL/6 mice were placed on a high-fat diet for six weeks and then injected twice per week for eight weeks with 25µg of 40 kDa dextran (DEX; vehicle control), P3DEX, or NTDEX. We found that treatment with P3DEX, but not NTDEX, led to reductions in body weight, adipose tissue (AT) weights, and fasting blood glucose levels. Mice treated with P3DEX also demonstrated improvements in glucose homeostasis and insulin tolerance. Treatment with P3DEX or NTDEX also induced different profiles of serum chemokines, cytokines, adipokines, and incretin hormones, with P3DEX notably reducing circulating levels of leptin and resistin. P3DEX also reduced WAT inflammation and hepatic lipid accumulation, whereas NTDEX seemed to worsen these parameters. These results suggest that the small structural difference between P3DEX and NTDEX has significant effects on the conjugates’ therapeutic abilities. Future work will focus on identifying the receptors for these conjugates and delineating the mechanisms by which P3DEX and NTDEX exert their effects.

Jessica Ramadhin, Vanessa Silva-Moraes, Tamas Nagy, Thomas Norberg, Donald Harn. Front Immunol. 2021 May 20;12:668217. doi: 10.3389/fimmu.2021.668217

Aminoalkoxycarbonyloxymethyl Ether Prodrugs with a pH-Triggered Release Mechanism: A Case Study Improving the Solubility, Bioavailability, and Efficacy of Antimalarial 4(1 H)-Quinolones with Single Dose Cures

Preclinical and clinical development of numerous small molecules is prevented by their poor aqueous solubility, limited absorption, and oral bioavailability. Herein, we disclose a general prodrug approach that converts promising lead compounds into aminoalkoxycarbonyloxymethyl (amino AOCOM) ether-substituted analogues that display significantly improved aqueous solubility and enhanced oral bioavailability, restoring key requirements typical for drug candidate profiles. The prodrug is completely independent of biotransformations and animal-independent because it becomes an active compound via a pH-triggered intramolecular cyclization-elimination reaction. As a proof-of-concept, the utility of this novel amino AOCOM ether prodrug approach was demonstrated on an antimalarial compound series representing a variety of antimalarial 4(1H)-quinolones, which entered and failed preclinical development over the last decade. With the amino AOCOM ether prodrug moiety, the 3-aryl-4(1H)-quinolone preclinical candidate was shown to provide single-dose cures in a rodent malaria model at an oral dose of 3 mg/kg, without the use of an advanced formulation technique.

Andrii Monastyrskyi, Fabian Brockmeyer, Alexis N LaCrue, Yingzhao Zhao, Steven P Maher, Jordany R Maignan, Vivian Padin-Irizarry, Yana I Sakhno, Prakash T Parvatkar, Ami H Asakawa, Lili Huang, Debora Casandra, Sherwin Mashkouri, Dennis E Kyle, Roman Manetsch. J Med Chem. 2021 May 12. doi: 10.1021/acs.jmedchem.0c01104.

Toll9 from Bombyx mori functions as a pattern recognition receptor that shares features with Toll-like receptor 4 from mammals

Toll/Toll-like receptors (TLRs) are key regulators of the innate immune system in both invertebrates and vertebrates. However, while mammalian TLRs directly recognize pathogen-associated molecular patterns, the insect Toll pathway is thought to be primarily activated by binding Spätzle cytokines that are processed from inactive precursors in response to microbial infection. Phylogenetic and structural data generated in this study supported earlier results showing that Toll9 members differ from other insect Tolls by clustering with the mammalian TLR4 group, which recognizes lipopolysaccharide (LPS) through interaction with myeloid differentiation-2 (MD-2)-like proteins. Functional experiments showed that BmToll9 from the silkmoth Bombyx mori also recognized LPS through interaction with two MD-2-like proteins, previously named BmEsr16 and BmPP, that we refer to in this study as BmMD-2A and BmMD-2B, respectively. A chimeric BmToll9-TLR4 receptor consisting of the BmToll9 ectodomain and mouse TLR4 transmembrane and Toll/interleukin-1 (TIR) domains also activated LPS-induced release of inflammatory factors in murine cells but only in the presence of BmMD-2A or BmMD-2B. Overall, our results indicate that BmToll9 is a pattern recognition receptor for LPS that shares conserved features with the mammalian TLR4-MD-2-LPS pathway.

Ruonan Zhang, Xiaofeng Li, Jie Zhang, Yanjun Li, Yuan Wang, Yuhang Song, Feifei Ren, Huiyu Yi, Xiaojuan Deng, Yangjin Zhong, Yang Cao, Michael R Strand, Xiao-Qiang Yu, Wanying Yang. Proc Natl Acad Sci U S A. 2021 May 11;118(19):e2103021118. doi: 10.1073/pnas.2103021118.