Protozoan phagotrophy from predators to parasites: An overview of the enigmatic cytostome-cytopharynx complex of Trypanosoma cruzi

A limitation lifted: A conditional knockdown system reveals essential roles for Polo-like kinase and Aurora kinase 1 in Trypanosoma cruzi cell division

While advances in genome editing technologies have simplified gene disruption in many organisms, the study of essential genes requires development of conditional disruption or knockdown systems that are not available in most organisms. Such is the case for Trypanosoma cruzi, a parasite that causes Chagas disease, a severely neglected tropical disease endemic to Latin America that is often fatal. Our knowledge of the identity of essential genes and their functions in T. cruzi has been severely constrained by historical challenges in very basic genetic manipulation and the absence of RNA interference machinery. Here, we describe the development and use of self-cleaving RNA sequences to conditionally regulate essential gene expression in T. cruzi. Using these tools, we identified essential roles for Polo-like and Aurora kinases in T. cruzi cell division, mirroring their functions in Trypanosoma brucei. Importantly, we demonstrate conditional knockdown of essential genes in intracellular amastigotes, the disease-causing stage of the parasite in its human host. This conditional knockdown system enables the efficient and scalable functional characterization of essential genes in T. cruzi and provides a framework for the development of conditional gene knockdown systems for other nonmodel organisms.

Characterization of Allobodo yubaba sp. nov. and Novijibodo darinka gen. et sp. nov., cultivable free-living species of the phylogenetically enigmatic kinetoplastid taxon Allobodonidae

Kinetoplastids are a large and diverse protist group, spanning ecologically important free-living forms to medically important parasites. The taxon Allobodonidae holds an unresolved position within kinetoplastids, and the sole described species, Allobodo chlorophagus, is uncultivated, being a necrotroph/parasite of macroalgae. Here we describe Allobodo yubaba sp. nov. and Novijibodo darinka gen. nov. et sp. nov., both free-living bacterivores isolated into monoeukaryotic cultures. Electron microscopy shows that both A. yubaba and N. darinka have a microtubular prism in the feeding apparatus (absent in A. chlorophagus), and an ovoid eukinetoplast, rather than pan-kDNA as in A. chlorophagus. Phylogenetic analyses of SSU rDNA sequences robustly place A. yubaba as the sister to A. chlorophagus, while N. darinka branches separately within Allobodonidae, as a sister group of undescribed freshwater isolates. We view Allobodonidae as containing at least four genus-level clades: Allobodo (A. chlorophagus and A. yubaba n. sp.), an undescribed fresh-water clade, an undescribed marine clade, and now Novijibodo-with N. darinka as its sole known member. Electron microscopy also revealed a rod-shaped gram-negative bacterial cytoplasmic endosymbiont in our N. darinka isolate. The availability of these species in monoeukaryotic culture should facilitate future research, including resolving the position of Allobodonidae using phylogenomic approaches.

Inside the Host: Understanding the Evolutionary Trajectories of Intracellular Parasitism

This review explores the origins of intracellular parasitism, an intriguing facet of symbiosis, where one organism harms its host, potentially becoming deadly. We focus on three distantly related groups of single-celled eukaryotes, namely Kinetoplastea, Holomycota, and Apicomplexa, which contain multiple species-rich lineages of intracellular parasites. Using comparative analysis of morphological, physiological, and molecular features of kinetoplastids, microsporidians, and sporozoans, as well as their closest free-living relatives, we reveal the evolutionary trajectories and adaptations that enabled the transition to intracellular parasitism. Intracellular parasites have evolved various efficient mechanisms for host acquisition and exploitation, allowing them to thrive in a variety of hosts. Each group has developed unique features related to the parasitic lifestyle, involving dedicated protein families associated with host cell invasion, survival, and exit. Indeed, parallel evolution has led to distinct lineages of intracellular parasites employing diverse traits and approaches to achieve similar outcomes.

Phagocytosis underpins the biotrophic lifestyle of intracellular parasites in the class Phytomyxea (Rhizaria)

Phytomyxea are intracellular biotrophic parasites infecting plants and stramenopiles, including the agriculturally impactful Plasmodiophora brassicae and the brown seaweed pathogen Maullinia ectocarpii. They belong to the clade Rhizaria, where phagotrophy is the main mode of nutrition. Phagocytosis is a complex trait of eukaryotes, well documented for free-living unicellular eukaryotes and specific cellular types of animals. Data on phagocytosis in intracellular, biotrophic parasites are scant. Phagocytosis, where parts of the host cell are consumed at once, is seemingly at odds with intracellular biotrophy. Here we provide evidence that phagotrophy is part of the nutritional strategy of Phytomyxea, using morphological and genetic data (including a novel transcriptome of M. ectocarpii). We document intracellular phagocytosis in P. brassicae and M. ectocarpii by transmission electron microscopy and fluorescent in situ hybridization. Our investigations confirm molecular signatures of phagocytosis in Phytomyxea and hint at a small specialized subset of genes used for intracellular phagocytosis. Microscopic evidence confirms the existence of intracellular phagocytosis, which in Phytomyxea targets primarily host organelles. Phagocytosis seems to coexist with the manipulation of host physiology typical of biotrophic interactions. Our findings resolve long debated questions on the feeding behaviour of Phytomyxea, suggesting an unrecognized role for phagocytosis in biotrophic interactions.

Are patents important indicators of innovation for Chagas disease treatment?

INTRODUCTION

Chagas disease is a neglected, endemic disease in 21 countries, spreading to non-endemic countries too. Like other neglected diseases affecting primarily low- and middle-income countries, low investment and the absence of new chemical entities from the industry occurred. Increased knowledge about the parasite, drug targets, and vector control has been observed, but this was not translated into new drugs. The partnerships of pharmaceutical companies with academies and consolidated networks to increment the new drugs and treatment research in Chagas disease are shown. The current review analyzes in detail the patents dealing with compounds candidates for new drugs and treatment. The patent search was performed using Orbit Intelligence® software in the 2001-2021 period.

AREAS COVERED

The author focused specifically on patents for the treatment, the new candidates disclosed in the patents, and the barriers to innovation.

EXPERT OPINION

Patents in Chagas disease have been increasing in the last years, although they do not bring new compounds to an effective treatment.