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© 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/), Malaria is a febrile illness caused by species of the protozoan parasite Plasmodium and is characterized by recursive infections of erythrocytes, leading to clinical symptoms and pathology. In mammals, Plasmodium parasites undergo a compulsory intrahepatic development stage before infecting erythrocytes. Liver-stage parasites have a metabolic configuration to facilitate the replication of several thousand daughter parasites. Their metabolism is of interest to identify cellular pathways essential for liver infection, to kill the parasite before onset of the disease. In this review, we summarize the current knowledge on nutrient acquisition and biosynthesis by liver-stage parasites mostly generated in murine malaria models, gaps in knowledge, and challenges to create a holistic view of the development and deficiencies in this field., This work was also financed by la Caixa Foundation (HR17/52150010) to M.M.M.

© 2022 The Authors. This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/)., Intracellular pathogens manipulate host cells to survive and thrive. Cellular sensing and signaling pathways are among the key host machineries deregulated to favor infection. In this study, we show that liver-stage Plasmodium parasites compete with the host to sequester a host endosomal-adaptor protein (APPL1) known to regulate signaling in response to endocytosis. The enrichment of APPL1 at the parasitophorous vacuole membrane (PVM) involves an atypical Plasmodium Rab5 isoform (Rab5b). Depletion of host APPL1 alters neither the infection nor parasite development; however, upon overexpression of a GTPase-deficient host Rab5 mutant (hRab5_Q79L), the parasites are smaller and their PVM is stripped of APPL1. Infection with the GTPase-deficient Plasmodium berghei Rab5b mutant (PbRab5b_Q91L) in this case rescues the PVM APPL1 signal and parasite size. In summary, we observe a robust correlation between the level of APPL1 retention at the PVM and parasite size during exoerythrocytic development., This work was supported by grants from the la Caixa Banking Foundation and Fundação para a Ciência e a Tecnologia (HR17-00264 and PTDC/SAU-PAR/30751/2017 respectively, both to M.M.M.). A.L and S.S.B were sponsored by Fundação para a Ciência e a Tecnologia fellowships (PD/BD/114036/2015, SFRH/BD/114464/2016, respectively). V.S acknowledges funding from the Science and Engineering Research Board (SERB) (EMR/2016/006810), Department of Science and Technology (DST), Government of India. V.P. and C.S. were supported by GRK2581 (P6) SPHINGOINF of the Growing Spine Foundation (DFG).

Malaria infection involves an obligatory, yet clinically silent liver stage1,2. Hepatocytes operate in repeating units termed lobules, exhibiting heterogeneous gene expression patterns along the lobule axis3, but the effects of hepatocyte zonation on parasite development have not been molecularly explored. Here, we combine single-cell RNA sequencing4 and single-molecule transcript imaging5 to characterize the host’s and parasite’s temporal expression programs in a zonally-controlled manner for the rodent malaria parasite Plasmodium berghei ANKA. We identify differences in parasite gene expression in distinct zones, and a sub-population of periportally-biased hepatocytes that harbor abortive infections associated with parasitophorous vacuole breakdown. These ‘abortive hepatocytes’ up-regulate immune recruitment and key signaling programs. They exhibit reduced levels of Plasmodium transcripts, perturbed parasite mRNA localization, and may give rise to progressively lower abundance of periportal infections. Our study provides a resource for understanding the liver stage of Plasmodium infection at high spatial resolution and highlights heterogeneous behavior of both the parasite and the host hepatocyte.

Parasite-derived PVM-resident proteins are critical for complete parasite development inside hepatocytes (Hanson et al., 2013; Mueller et al., 2005), although the function of most of these proteins remains unknown. Here, we show that the Up-Regulated in Infectious Sporozoites 4 (UIS4) protein, resident at the PVM, interacts with the host-cell actin. By suppressing filamentous actin formation UIS4 avoids parasite elimination. Host-cell actin dynamics increases around UIS4-deficient parasites, which is associated with subsequent parasite elimination. Notably, parasite elimination is impaired significantly by the inhibition of host myosin-II, possibly through relieving the compression generated by actomyosin complexes at the host-parasite interface. Together, these data reveal that UIS4 has a critical role in the evasion of host defensive mechanisms, enabling hence EEF survival and development.

© Copyright © 2016, The Author(s). This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/, Iron is an essential micronutrient but is also highly toxic. In yeast and plant cells, a key detoxifying mechanism involves iron sequestration into intracellular storage compartments, mediated by members of the vacuolar iron-transporter (VIT) family of proteins. Here we study the VIT homologue from the malaria parasites Plasmodium falciparum (PfVIT) and Plasmodium berghei (PbVIT). PfVIT-mediated iron transport in a yeast heterologous expression system is saturable (Km ∼ 14.7 μM), and selective for Fe(2+) over other divalent cations. PbVIT-deficient P. berghei lines (Pbvit(-)) show a reduction in parasite load in both liver and blood stages of infection in mice. Moreover, Pbvit(-) parasites have higher levels of labile iron in blood stages and are more sensitive to increased iron levels in liver stages, when compared with wild-type parasites. Our data are consistent with Plasmodium VITs playing a major role in iron detoxification and, thus, normal development of malaria parasites in their mammalian host., This work was supported by grants from the European Research Council ERC-2012-StG_311502 to M.M.M., Fundação para a Ciência e Tecnologia EXPL/BIM-MET/0753/2013 and The European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n°. 304948—NANOMAL to S.K. and H.M.S. K.S. was supported by an EMBO long-term fellowship (EMBO ALTF 1584-2011).

Dissertação de Mestrado em Biologia Celular e Molecular, apresentada ao Departamento de Ciências da Vida da Universidade de Coimbra. Malaria has long been a threat to survival and persistently challenging at vaccine development. With a stuttering rise in drug resistant strains of the human parasites - Plasmodium falciparum and Plasmodium vivax, it is of paramount concern to identify new drug targets, which would render infection unsustainable at the earliest stage. As an essential co-factor iron has a critical role in virtually every cell from the simplest prokaryotes to complex eukaryotes. In humans, the fine tuning of iron homeostatic mechanism also dictates the outcomes to various infections. Plasmodium with its intricate life cycle and immense replication potential exhibits a high demand for iron at multiple stages during its development. During its intra-erythrocytic development Plasmodium has several possible iron reservoirs at its disposal in the host cell such as the iron bound in ferritin, the cytosolic labile iron pool and hemoglobin. The parasite’s mechanism for iron uptake from the host and, its storage still remain shrouded due to the complexity in relating genome sequence of Plasmodium spp. to specific proteins and function. In this thesis project we have attempted to explore the function of two novel iron transporters in Plasmodium: Divalent metal transporter (DMT1) and Vacuolar iron transporter (VIT) homologues and, investigate the effect of compromise of their function on parasite development and virulence. Understanding the iron transport mechanism will shed some light on possible methods to target such machinery, if found essential. A malária continua a ser uma ameaça à sobrevivência e persiste ao desafio da formulação de uma vacina. Com o aumento da prevalência das estirpes de Plasmodium falciparum e Plasmodium vivax resistentes aos fármacos disponíveis, torna-se cada vez mais relevante a identificação de novos alvos moleculares para o desenvolvimento de fármacos que inibam a infeção em fases precoces. O ferro, um co-factor essencial, tem um papel fundamental em virtualmente todas as células, desde o mais simples procariota até ao mais complexo eucariota. No Homem, a regulação da homeostase do ferro determina o resultado de várias infeções. Dado o seu ciclo de vida complexo e o seu grande potencial replicativo, Plasmodium spp. requerem uma grande disponibilidade ferro durante o seu desenvolvimento. Durante a sua maturação nos eritrócitos, Plasmodium tem na célula hospedeira várias reservas de ferro disponíveis, tais como, o ferro ligado à ferritina, o ferro livre no citosol e o ferro contido na hemoglobina. Os mecanismos utilizados pelo parasita na obtenção de ferro a partir do hospedeiro e no seu armazenamento continuam elusivos. Um obstáculo reside em parte na dificuldade em relacionar uma dada sequência genómica de Plasmodium spp. com a função da proteína resultante. Neste trabalho, tentámos explorar a função de dois transportadores de ferro identificados em Plasmodium: o Transportador de metais divalentes (do inglês, DMT) e o Transportador vacuolar de ferro (do inglês, VIT). Nesse âmbito estudámos o efeito da disrupção da sua função no desenvolvimento e na virulência do parasita. A melhor compreensão desta maquinaria do parasita, se considerada essencial, elucidará possíveis métodos para a modular e utilizar como alvo terapêutico.

Twelve male patients with non-union of fracture neck femur of 6-12 months duration were managed by open reduction and internal fixation and tensor fascia lata or gluteus medius muscle pedicle bone grafting through the anterior route. Internal fixation was done with Knowles pins and Asinis screws or combination of both. Union could be achieved in 11 out of the 12 cases. Functional recovery of hip was good in 9, fair in 2 and poor in one.