scholarly journals Visualization of a Dinoflagellate-Infecting Virus HcDNAV and Its Infection Process

Viruses ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 554 ◽  
Author(s):  
Yoshihito Takano ◽  
Yuji Tomaru ◽  
Keizo Nagasaki
Keyword(s):  
Infection Process ◽  
Host Cells ◽  
Epifluorescence Microscopy ◽  
Entry Site ◽  
Marine Microalga ◽  
Double Stranded Dna ◽  
Heterocapsa Circularisquama ◽  
Close Proximity ◽  
Host Nucleus ◽  
Virus Factory

HcDNAV (a type species of Genus Dinodnavirus) is a large double-stranded DNA virus, which lytically infects the bloom-forming marine microalga Heterocapsa circularisquama Horiguchi (Dinophyceae). In the present study, detailed observation of the HcDNAV particle and its infection process was conducted via field emission scanning electron microscopy (FE-SEM) and epifluorescence microscopy (EFM). Each five-fold vertex of the icosahedral virion was decorated with a protrusion, which may be related to the entry process of HcDNAV into the host. The transverse groove of host cells is proposed to be the main virus entry site. A visible DAPI-stained region, which is considered to be the viroplasm (virus factory), appeared in close proximity to the host nucleus at 11 h post infection (hpi); the putative viral DAPI signal was remarkably enlarged at 11–30 hpi. It was kidney-shaped at 13–15 hpi, horseshoe-shaped at 20 hpi, doughnut-shaped at 30 hpi, and changed into a three-dimensionally complicated shape at 51–53 hpi, by which time most parts of the host cell were occupied by the putative viral DAPI signal. While the virions were within the viroplasm, they were easily distinguishable by their vertex protrusions by FE-SEM.

Biochemical and cellular mechanisms regulatingAcanthamoeba castellaniiadherence to host cells

Parasitology ◽  
2013 ◽  
Vol 141 (4) ◽  
pp. 531-541 ◽  
Author(s):  
K. J. SOTO-ARREDONDO ◽  
L. L. FLORES-VILLAVICENCIO ◽  
J. J. SERRANO-LUNA ◽  
M. SHIBAYAMA ◽  
M. SABANERO-LÓPEZ
Keyword(s):  
Neuronal Cells ◽  
Acanthamoeba Castellanii ◽  
Cell Types ◽  
Infection Process ◽  
Surface Proteins ◽  
Host Cells ◽  
Epifluorescence Microscopy ◽  
Cellular Mechanisms ◽  
Cutaneous Lesions ◽  
Causative Agents

SUMMARYFree-living amoebae belonging to the genusAcanthamoebaare the causative agents of infections such as amoebic keratitis (AK), granulomatous amoebic encephalitis (GAE) and cutaneous lesions. The mechanisms involved in the establishment of infection are unknown. However, it is accepted that the initial phase of pathogenesis involves adherence to the host tissue. In this work, we analysed surface molecules with an affinity for epithelial and neuronal cells from the trophozoites ofAcanthamoeba castellanii. We also investigated the cellular mechanisms that govern the process of trophozoite adhesion to the host cells. We first used confocal and epifluorescence microscopy to examine the distribution of theA. castellaniiactin cytoskeleton during interaction with the host cells. The use of drugs, as cytochalasin B (CB) and latrunculin B (LB), revealed the participation of cytoskeletal filaments in the adhesion process. In addition, to identify the proteins and glycoproteins on the surface ofA. castellanii, the trophozoites were labelled with biotin and biotinylated lectins. The results revealed bands of surface proteins, some of which were glycoproteins with mannose andN-acetylglucosamine residues. Interaction assays of biotinylated amoebae proteins with epithelial and neuronal cells showed that some surface proteins had affinity for both cell types. The results of this study provide insight into the biochemical and cellular mechanisms of theAcanthamoebainfection process.

The illustrated life cycle of Microbotryum on the host plant Silene latifolia

Botany ◽  
2010 ◽  
Vol 88 (10) ◽  
pp. 875-885 ◽  
Author(s):  
Angela Maria Schäfer ◽  
Martin Kemler ◽  
Robert Bauer ◽  
Dominik Begerow
Keyword(s):  
Life Cycle ◽  
Light And Electron Microscopy ◽  
Laboratory Data ◽  
Infection Process ◽  
Host Cells ◽  
Silene Latifolia ◽  
Long Distance ◽  
Biological Studies ◽  
Plant Parasitic

The plant-parasitic genus Microbotryum (Pucciniomycotina) has been used as a model for various biological studies, but fundamental aspects of its life history have not been documented in detail. The smut fungus is characterized by a dimorphic life cycle with a haploid saprophytic yeast-like stage and a dikaryotic plant-parasitic stage, which bears the teliospores as dispersal agents. In this study, seedlings and flowers of Silene latifolia Poir. (Caryophyllaceae) were inoculated with teliospores or sporidial cells of Microbotryum lychnidis-dioicae (DC. ex Liro) G. Deml & Oberw. and the germination of teliospores, the infection process, and the proliferation in the host tissue were documented in vivo using light and electron microscopy. Although germination of the teliospore is crucial for the establishment of Microbotryum, basidium development is variable under natural conditions. In flowers, where the amount of nutrients is thought to be high, the fungus propagates as sporidia, and mating of compatible cells takes place only when flowers are withering and nutrients are decreasing. On cotyledons (i.e., nutrient-depleted conditions), conjugation occurs shortly after teliospore germination, often via intrapromycelial mating. After formation of an infectious hypha with an appressorium, the invasion of the host occurs by direct penetration of the epidermis. While the growth in the plant is typically intercellular, long distance proliferation seems mediated through xylem tracheary elements. At the beginning of the vegetation period, fungal cells were found between meristematic shoot host cells, indicating a dormant phase inside the plant. By using different microscopy techniques, many life stages of Microbotryum are illustrated for the first time, thereby allowing new interpretations of laboratory data.

scholarly journals An endometrial organoid model of Chlamydia-epithelial and immune cell interactions

2020 ◽  
Author(s):  
Lee Dolat ◽  
Raphael H. Valdivia
Keyword(s):  
Epithelial Cell ◽  
Cell Biology ◽  
Immune Cell ◽  
Three Dimensional ◽  
Time Lapse ◽  
Cell Types ◽  
Infection Process ◽  
Host Cells ◽  
Cell Diversity ◽  
Intracellular Organelles

ABSTRACTOur understanding of how the obligate intracellular bacterium Chlamydia trachomatis reprograms the cell biology of host cells in the upper genital tract is largely based on observations made in cell culture with transformed epithelial cell lines. Here we describe a primary spherical organoid system derived from endometrial tissue to recapitulate epithelial cell diversity, polarity, and ensuing responses to Chlamydia infection. Using high-resolution and time-lapse microscopy, we catalogue the infection process in organoids from invasion to egress, including the reorganization of the cytoskeleton and positioning of intracellular organelles. We show this model is amenable to screening C. trachomatis mutants for defects in the fusion of pathogenic vacuoles, the recruitment of intracellular organelles, and inhibition of cell death. Moreover, we reconstructed a primary immune cell response by co-culturing infected organoids with neutrophils, and determined that the effector TepP limits the recruitment of neutrophils to infected organoids. Collectively, our model details a system to study the cell biology of Chlamydia infections in three dimensional structures that better reflect the diversity of cell types and polarity encountered by Chlamydia upon infection of their animal hosts.Summary statement3D endometrial organoids to model Chlamydia infection and the role of secreted virulence factors in reprogramming host epithelial cells and immune cell recruitment

scholarly journals Dinoflagellate Host Chloroplasts and Mitochondria Remain Functional During Amoebophrya Infection

2020 ◽  
Vol 11 ◽  
Author(s):  
Ehsan Kayal ◽  
Catharina Alves-de-Souza ◽  
Sarah Farhat ◽  
Lourdes Velo-Suarez ◽  
Joanne Monjol ◽  
...  
Keyword(s):  
Gene Expression ◽  
Carbon Fixation ◽  
Nuclear Gene ◽  
Host Cells ◽  
Infection Period ◽  
Nuclear Gene Expression ◽  
Intracellular Parasites ◽  
Electron Transport Chains ◽  
Complete Digestion ◽  
Host Nucleus

Dinoflagellates are major components of phytoplankton that play critical roles in many microbial food webs, many of them being hosts of countless intracellular parasites. The phototrophic dinoflagellate Scrippsiella acuminata (Dinophyceae) can be infected by the microeukaryotic parasitoids Amoebophrya spp. (Syndiniales), some of which primarily target and digest the host nucleus. Early digestion of the nucleus at the beginning of the infection is expected to greatly impact the host metabolism, inducing the knockout of the organellar machineries that highly depend upon nuclear gene expression, such as the mitochondrial OXPHOS pathway and the plastid photosynthetic carbon fixation. However, previous studies have reported that chloroplasts remain functional in swimming host cells infected by Amoebophrya. We report here a multi-approach monitoring study of S. acuminata organelles over a complete infection cycle by nucleus-targeting Amoebophrya sp. strain A120. Our results show sustained and efficient photosystem II activity as a hallmark of functional chloroplast throughout the infection period despite the complete digestion of the host nucleus. We also report the importance played by light on parasite production, i.e., the amount of host biomass converted to parasite infective propagules. Using a differential gene expression analysis, we observed an apparent increase of all 3 mitochondrial and 9 out of the 11 plastidial genes involved in the electron transport chains (ETC) of the respiration pathways during the first stages of the infection. The longer resilience of organellar genes compared to those encoded by the nucleus suggests that both mitochondria and chloroplasts remain functional throughout most of the infection. This extended organelle functionality, along with higher parasite production under light conditions, suggests that host bioenergetic organelles likely benefit the parasite Amoebophrya sp. A120 and improve its fitness during the intracellular infective stage.

scholarly journals Targeting adhesion in fungal pathogen Candida albicans

2020 ◽  
Author(s):  
Harlei Martin ◽  
Kevin Kavanagh ◽  
Trinidad Velasco-Torrijos
Keyword(s):  
Candida Albicans ◽  
Fungal Infections ◽  
Initial Step ◽  
Infection Process ◽  
Host Cells ◽  
Fungal Cell ◽  
Receptor Interactions ◽  
Genes Encoding ◽  
Invasive Infections ◽  
Wall Components

Fungal infections with increasing resistance to conventional therapies are a growing concern. Candida albicans is a major opportunistic yeast responsible for mucosal and invasive infections. Targeting the initial step of the infection process (i.e., C. albicans adhesion to the host cell) is a promising strategy. A wide variety of molecules can interfere with adhesion processes via an assortment of mechanisms. Herein, we focus on how small molecules disrupt biosynthesis of fungal cell wall components and membrane structure, prevent the localization of GPI-anchor proteins, inhibit production of enzymes involved in adhesion, downregulate genes encoding adhesins and competitively inhibit receptor interactions. As a result, adhesion of C. albicans to host cells is reduced, paving the way to new classes of antifungal agents.

scholarly journals An overview of RNA virus-encoded microRNAs

ExRNA ◽  
2019 ◽  
Vol 1 (1) ◽  
Author(s):  
Xihan Li ◽  
Xiaoping Zou
Keyword(s):  
Gene Expression ◽  
Gene Regulation ◽  
Viral Replication ◽  
Potential Role ◽  
Rna Viruses ◽  
Rna Virus ◽  
Host Cells ◽  
Basic Pattern ◽  
Double Stranded Dna ◽  
Non Coding Rnas

Abstract MicroRNAs (miRNAs) are a number of small non-coding RNAs playing a regulatory part in gene expression. Many virus-encoded miRNAs have been found, which manifests that viruses as well apply the basic pattern of gene regulation, however, mostly in viruses transcribed from double-stranded DNA genomes. It is still in dispute if RNA viruses could encode miRNAs because the excision of miRNA might result in the cleavage of viral RNA genome. We will focus on the miRNAs encoded by RNA virus and discuss their potential role in viral replication cycle and host cells.

Ultrastructure of eastern cottonwood clones susceptible or resistant to leaf rust

1987 ◽  
Vol 65 (8) ◽  
pp. 1586-1598 ◽  
Author(s):  
L. Shain ◽  
U. Järlfors
Keyword(s):  
Electron Microscopy ◽  
Leaf Rust ◽  
Light And Electron Microscopy ◽  
Infection Process ◽  
The Other ◽  
Host Cells ◽  
Eastern Cottonwood ◽  
Melampsora Medusae ◽  
Wall Appositions ◽  
Infected Cells

The infection process in four clones of eastern cottonwood susceptible or resistant to leaf rust caused by Melampsora medusae was studied by light and electron microscopy. Infection was initiated by stomatal rather than direct entry. Typical dikaryotic haustoria were observed in all clones within 1 day of inoculation. Some healthy-appearing haustoria were observed in susceptible clones throughout the duration of the study, which was terminated during the initiation of uredial production. Incompatibility was expressed differently in the two resistant clones. In clone St 75, most haustoria and invaded host cells that were observed appeared necrotic within 2 days of inoculation. Cell wall appositions appeared during this time in cells adjoining necrotic host cells. Some infected cells disintegrated within 4 days of inoculation. Affected host cells of clone St 92, on the other hand, plasmolyzed during the first 2 to 3 days after inoculation. Necrotic host cells were not observed in this clone until the 4th day after inoculation. Hyphal ramification and host plasmolysis were extensive at 6 days after inoculation.

scholarly journals Oligosaccharides as Receptors for JC Virus

2002 ◽  
Vol 76 (24) ◽  
pp. 12992-13000 ◽  
Author(s):  
Rika Komagome ◽  
Hirofumi Sawa ◽  
Takashi Suzuki ◽  
Yasuo Suzuki ◽  
Shinya Tanaka ◽  
...  
Keyword(s):  
Sialic Acid ◽  
Demyelinating Disease ◽  
Jc Virus ◽  
Host Cells ◽  
Hemagglutination Activity ◽  
Dna Viruses ◽  
Double Stranded Dna ◽  
The Central Nervous System ◽  
Capsid Protein Vp1 ◽  
Sugar Chains

ABSTRACT JC virus (JCV) belongs to the polyomavirus family of double-stranded DNA viruses and in humans causes a demyelinating disease of the central nervous system, progressive multifocal leukoencephalopathy. Its hemagglutination activity and entry into host cells have been reported to depend on an N-linked glycoprotein containing sialic acid. In order to identify the receptors of JCV, we generated virus-like particles (VLP) consisting of major viral capsid protein VP1. We then developed an indirect VLP overlay assay to detect VLP binding to glycoproteins and a panel of glycolipids. We found that VLP bound to sialoglycoproteins, including α1-acid glycoprotein, fetuin, and transferrin receptor, and that this binding depended on α2-3-linked sialic acids and N-linked sugar chains. Neoglycoproteins were synthesized by using ovalbumin and conjugation with oligosaccharides containing the terminal α2-3- or α2-6-linked sialic acid or the branched α2-6-linked sialic acid. We show that the neoglycoprotein containing the terminal α2-6-linked sialic acid had the highest affinity for VLP, inhibited the hemagglutination activity of VLP and JCV, and inhibited the attachment of VLP to cells. We also demonstrate that VLP bound to specific glycolipids, such as lactosylceramide, and gangliosides, including GM3, GD2, GD3, GD1b, GT1b, and GQ1b, and that VLP bound weakly to GD1a but did not bind to GM1a, GM2, or galactocerebroside. Furthermore, the neoglycoprotein containing the terminal α2-6-linked sialic acid and the ganglioside GT1b inhibited JCV infection in the susceptible cell line IMR-32. These results suggest that the oligosaccharides of glycoproteins and glycolipids work as JCV receptors and may be feasible as anti-JCV agents.

scholarly journals Hierarchies of Host Factor Dynamics at the Entry Site of Shigella flexneri during Host Cell Invasion

2012 ◽  
Vol 80 (7) ◽  
pp. 2548-2557 ◽  
Author(s):  
Soudeh Ehsani ◽  
José Carlos Santos ◽  
Cristina D. Rodrigues ◽  
Ricardo Henriques ◽  
Laurent Audry ◽  
...  
Keyword(s):  
Host Cell ◽  
Tyrosine Kinases ◽  
Time Course ◽  
Shigella Flexneri ◽  
Time Lapse ◽  
Small Gtpases ◽  
Host Factors ◽  
Host Cells ◽  
Entry Site ◽  
Content Type

ABSTRACTShigella flexneri, the causative agent of bacillary dysentery, induces massive cytoskeletal rearrangement, resulting in its entry into nonphagocytic epithelial cells. The bacterium-engulfing membrane ruffles are formed by polymerizing actin, a process activated through injected bacterial effectors that target host small GTPases and tyrosine kinases. Once inside the host cell,S. flexneriescapes from the endocytic vacuole within minutes to move intra- and intercellularly. We quantified the fluorescence signals from fluorescently tagged host factors that are recruited to the site of pathogen entry and vacuolar escape. Quantitative time lapse fluorescence imaging revealed simultaneous recruitment of polymerizing actin, small GTPases of the Rho family, and tyrosine kinases. In contrast, we found that actin surrounding the vacuole containing bacteria dispersed first from the disassembling membranes, whereas other host factors remained colocalized with the membrane remnants. Furthermore, we found that the disassembly of the membrane remnants took place rapidly, within minutes after bacterial release into the cytoplasm. Superresolution visualization of galectin 3 through photoactivated localization microscopy characterized these remnants as small, specular, patchy structures between 30 and 300 nm in diameter. Using our experimental setup to track the time course of infection, we identified theS. flexnerieffector IpgB1 as an accelerator of the infection pace, specifically targeting the entry step, but not vacuolar progression or escape. Together, our studies show that bacterial entry into host cells follows precise kinetics and that this time course can be targeted by the pathogen.

scholarly journals RpoH Mediates the Expression of Some, but Not All, Genes Induced in Neisseria gonorrhoeae Adherent to Epithelial Cells

2006 ◽  
Vol 74 (5) ◽  
pp. 2767-2776 ◽  
Author(s):  
Ying Du ◽  
Cindy Grove Arvidson
Keyword(s):  
Epithelial Cells ◽  
Neisseria Gonorrhoeae ◽  
Host Cell ◽  
Infection Process ◽  
Host Cells ◽  
Cell Contact ◽  
Transmitted Infection ◽  
New Host ◽  
Sexually Transmitted ◽  
Cell Induction

ABSTRACT Neisseria gonorrhoeae (gonococcus [GC]), is highly adapted to the human host, the only known reservoir for gonococcal infection. However, since it is sexually transmitted, infection of a new host likely requires a regulatory response on the part of the gonococcus to respond to this significant change in environment. We previously showed that adherence of gonococci to epithelial cells results in changes of gene expression in the bacteria that presumably prepare them for subsequent steps in the infection process. Expression of the heat shock sigma factor gene, rpoH, was shown to be important for the invasion step, as gonococci depleted for rpoH were reduced in their ability to invade epithelial cells. Here, we show that of the genes induced in adherent gonococci, two are part of the gonococcal RpoH regulon. When RpoH is depleted, expression of these genes is no longer induced by host cell contact, indicating that RpoH is mediating the host cell induction response of these genes. One RpoH-dependent gene, NGO0376, is shown to be important for invasion of epithelial cells, consistent with earlier observations that RpoH is necessary for this step of infection. Two genes, NGO1684 and NGO0340, while greatly induced by host cell contact, were found to be RpoH independent, indicating that more than one regulator is involved in the response to host cell contact. Furthermore, NGO0340, but not NGO1684, was shown to be important for both adherence and invasion of epithelial cells, suggesting a complex regulatory network in the response of gonococci to contact with host cells.

Sign in / Sign up

Export Citation Format

Share Document