A Novel MicroRNA From the Translated Region of the Giardiavirus rdrp Gene Governs Virus Copy Number in Giardia duodenalis

Giardia duodenalis is an important zoonotic parasite that can cause human and animal diarrhea. Giardiavirus (GLV) is a double-stranded RNA virus in Totiviridae family, which specifically infects trophozoites of the primitive protozoan parasite G. duodenalis. However, the GLV infectious and the pathogenicity of the G. duodenalis still remain to be confirmed. The GLV genome is 6,277 bp, which encodes two proteins (Gag and Gag-Pol). The expression of Gag-Pol protein is regulated by a-1 ribosomal frameshift. In this report, we identified a novel microRNA (GLV miRNA1) from the GLV. Split ligation northern results showed that GLV miRNA1 is a special expression product of GLV, and the precursor was also identified by primer extension. Antisense sequence of the GLV miRNA1 could increase the copy number of virus in G. duodenalis. It suggests that GLV miRNA1 governs the copy number of Giardiavirus in G. duodenalis. Most importantly, the GLV miRNA1 lies at the translated region of the rdrp gene, which is the first case that microRNA locates in the translated region of a known protein. It may be implying a novel phenomenon for miRNA biogenesis.

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Detection of zoonotic and livestock-specific assemblages of Giardia duodenalis in free-living wild lizards

Revista Brasileira de Parasitologia Veterinária ◽

10.1590/s1984-29612017034 ◽

2017 ◽

Vol 26 (3) ◽

pp. 395-399 ◽

Cited By ~ 4

Author(s):

Aurora Reboredo-Fernández ◽

Elvira Ares-Mazás ◽

Pedro Galán ◽

Simone Mario Cacciò ◽

Hipólito Gómez-Couso

Keyword(s):

Giardia Duodenalis ◽

Pcr Amplification ◽

Protozoan Parasite ◽

Its2 Region ◽

Free Living ◽

Wide Range ◽

Two Samples ◽

Zoonotic Parasite ◽

Rock Lizard ◽

Podarcis Bocagei

Abstract Giardia duodenalis is a zoonotic parasite that infects the gut of a wide range of vertebrates, including numerous wildlife species. However, little is known about this protozoan parasite in reptiles. Fecal samples from 31 wild lizards were collected in Galicia (northwest Spain) and screened for the presence of Giardia by PCR amplification and sequencing of the ITS1-5.8S-ITS2 region in the ribosomal unit. This allowed detection of the parasite in 5 samples (16.1%), and enabled identification of G. duodenalis assemblage A2 in two samples of Iberian rock lizard (Iberolacerta monticola), G. duodenalis assemblage B in other two samples of I. monticola, and G. duodenalis assemblage E in one sample of Bocage’s wall lizard (Podarcis bocagei). The results obtained after PCR amplification and sequencing of the SSU-rDNA gene confirmed the presence of G. duodenalis assemblage A in two samples of I. monticola. This is the first report of G. duodenalis in free-living lizards, although further studies are needed to distinguish between actual infection and mechanical dissemination of cysts. The detection of zoonotic and livestock-specific assemblages of G. duodenalis demonstrates the wide environmental contamination by this parasite, possibly due to human activities.

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N6-methyladenosine RNA modification suppresses antiviral innate sensing pathways via reshaping double-stranded RNA

Nature Communications ◽

10.1038/s41467-021-21904-y ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Weinan Qiu ◽

Qingyang Zhang ◽

Rui Zhang ◽

Yangxu Lu ◽

Xin Wang ◽

...

Keyword(s):

Rna Virus ◽

Negative Regulator ◽

Rna Modification ◽

Type I ◽

Viral Immunity ◽

Potential Therapeutic Target ◽

Viral Dsrna ◽

Double Stranded Rna ◽

Genetic Ablation ◽

Vesicular Stomatitis

AbstractDouble-stranded RNA (dsRNA) is a virus-encoded signature capable of triggering intracellular Rig-like receptors (RLR) to activate antiviral signaling, but whether intercellular dsRNA structural reshaping mediated by the N6-methyladenosine (m6A) modification modulates this process remains largely unknown. Here, we show that, in response to infection by the RNA virus Vesicular Stomatitis Virus (VSV), the m6A methyltransferase METTL3 translocates into the cytoplasm to increase m6A modification on virus-derived transcripts and decrease viral dsRNA formation, thereby reducing virus-sensing efficacy by RLRs such as RIG-I and MDA5 and dampening antiviral immune signaling. Meanwhile, the genetic ablation of METTL3 in monocyte or hepatocyte causes enhanced type I IFN expression and accelerates VSV clearance. Our findings thus implicate METTL3-mediated m6A RNA modification on viral RNAs as a negative regulator for innate sensing pathways of dsRNA, and also hint METTL3 as a potential therapeutic target for the modulation of anti-viral immunity.

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Multilocus Genotyping of Giardia duodenalis in Mostly Asymptomatic Indigenous People from the Tapirapé Tribe, Brazilian Amazon

Pathogens ◽

10.3390/pathogens10020206 ◽

2021 ◽

Vol 10 (2) ◽

pp. 206

Author(s):

Pamela Carolina Köster ◽

Antonio F. Malheiros ◽

Jeffrey J. Shaw ◽

Sooria Balasegaram ◽

Alexander Prendergast ◽

...

Keyword(s):

Triosephosphate Isomerase ◽

Gastrointestinal Symptoms ◽

Giardia Duodenalis ◽

Protozoan Parasite ◽

Indigenous Communities ◽

Brazilian Amazon ◽

Epidemiological Survey ◽

Small Subunit ◽

High Genetic Diversity ◽

Cross Sectional

Little information is available on the occurrence and genetic variability of the diarrhoea-causing enteric protozoan parasite Giardia duodenalis in indigenous communities in Brazil. This cross-sectional epidemiological survey describes the frequency, genotypes, and risk associations for this pathogen in Tapirapé people (Brazilian Amazon) at four sampling campaigns during 2008–2009. Microscopy was used as a screening test, and molecular (PCR and Sanger sequencing) assays targeting the small subunit ribosomal RNA, the glutamate dehydrogenase, the beta-giardin, and the triosephosphate isomerase genes as confirmatory/genotyping methods. Associations between G. duodenalis and sociodemographic and clinical variables were investigated using Chi-squared test and univariable/multivariable logistic regression models. Overall, 574 individuals belonging to six tribes participated in the study, with G. duodenalis prevalence rates varying from 13.5–21.7%. The infection was positively linked to younger age and tribe. Infected children <15 years old reported more frequent gastrointestinal symptoms compared to adults. Assemblage B accounted for three out of four G. duodenalis infections and showed a high genetic diversity. No association between assemblage and age or occurrence of diarrhoea was demonstrated. These data indicate that the most likely source of infection was anthropic and that different pathways (e.g., drinking water) may be involved in the transmission of the parasite.

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Re-Discovery of Giardiavirus: Genomic and Functional Analysis of Viruses from Giardia duodenalis Isolates

Biomedicines ◽

10.3390/biomedicines9060654 ◽

2021 ◽

Vol 9 (6) ◽

pp. 654

Author(s):

Gianluca Marucci ◽

Ilaria Zullino ◽

Lucia Bertuccini ◽

Serena Camerini ◽

Serena Cecchetti ◽

...

Keyword(s):

High Throughput Sequencing ◽

Diarrheal Disease ◽

Current Knowledge ◽

Biological Significance ◽

Giardia Duodenalis ◽

Protozoan Parasite ◽

Protein Translation ◽

Mass Spectrometry Analysis ◽

Animal Origin ◽

Spectrometry Analysis

Giardiasis, caused by the protozoan parasite Giardia duodenalis, is an intestinal diarrheal disease affecting almost one billion people worldwide. A small endosymbiotic dsRNA viruses, G. lamblia virus (GLV), genus Giardiavirus, family Totiviridae, might inhabit human and animal isolates of G. duodenalis. Three GLV genomes have been sequenced so far, and only one was intensively studied; moreover, a positive correlation between GLV and parasite virulence is yet to be proved. To understand the biological significance of GLV infection in Giardia, the characterization of several GLV strains from naturally infected G. duodenalis isolates is necessary. Here we report high-throughput sequencing of four GLVs strains, from Giardia isolates of human and animal origin. We also report on a new, unclassified viral sequence (designed GdRV-2), unrelated to Giardiavirus, encoding and expressing for a single large protein with an RdRp domain homologous to Totiviridae and Botybirnaviridae. The result of our sequencing and proteomic analyses challenge the current knowledge on GLV and strongly suggest that viral capsid protein translation unusually starts with a proline and that translation of the RNA-dependent RNA polymerase (RdRp) occurs via a +1/−2 ribosomal frameshift mechanism. Nucleotide polymorphism, confirmed by mass-spectrometry analysis, was also observed among and between GLV strains. Phylogenetic analysis indicated the occurrence of at least two GLV subtypes which display different phenotypes and transmissibility in experimental infections of a GLV naïve Giardia isolate.

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Cardiomyopathy Syndrome of Atlantic Salmon (Salmo salar L.) Is Caused by a Double-Stranded RNA Virus of the Totiviridae Family

Journal of Virology ◽

10.1128/jvi.02154-10 ◽

2011 ◽

Vol 85 (11) ◽

pp. 5275-5286 ◽

Cited By ~ 107

Author(s):

O. Haugland ◽

A. B. Mikalsen ◽

P. Nilsen ◽

K. Lindmo ◽

B. J. Thu ◽

...

Keyword(s):

Atlantic Salmon ◽

Salmo Salar ◽

Rna Virus ◽

Double Stranded Rna ◽

Atlantic Salmon Salmo Salar

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The coat protein of the yeast double-stranded RNA virus L-A attaches covalently to the cap structure of eukaryotic mRNA

Molecular and Cellular Biology ◽

10.1128/mcb.12.8.3390-3398.1992 ◽

1992 ◽

Vol 12 (8) ◽

pp. 3390-3398

Author(s):

A Blanc ◽

C Goyer ◽

N Sonenberg

Keyword(s):

Saccharomyces Cerevisiae ◽

Coat Protein ◽

Translation Initiation ◽

Rna Virus ◽

Binding Protein ◽

Covalent Bond ◽

Cellular Proteins ◽

Double Stranded Rna ◽

Virus Coat ◽

Drosophila Cells

The eukaryotic mRNA 5' cap structure m7GpppX (where X is any nucleotide) interacts with a number of cellular proteins. Several of these proteins were studied in mammalian, yeast, and drosophila cells and found to be involved in translation initiation. Here we describe a novel cap-binding protein, the coat protein of L-A, a double-stranded RNA virus that is persistently maintained in many Saccharomyces cerevisiae strains. The results also suggest that the coat protein of a related double-stranded RNA virus (L-BC) is likewise a cap-binding protein. Strikingly, in contrast to the cellular cap-binding proteins, the interaction between the L-A virus coat protein and the cap structure is through a covalent bond.

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New Associated Structures of the Anterior Flagella of Giardia duodenalis

Microscopy and Microanalysis ◽

10.1017/s1431927613013275 ◽

2013 ◽

Vol 19 (5) ◽

pp. 1374-1376 ◽

Cited By ~ 9

Author(s):

Claudia Maia-Brigagão ◽

Ana Paula Rocha Gadelha ◽

Wanderley de Souza

Keyword(s):

Electron Microscopy ◽

Structural Organization ◽

Giardia Duodenalis ◽

Protozoan Parasite ◽

Filamentous Structure ◽

Marginal Plates ◽

Favorable Conditions ◽

And Behavior ◽

Crossing Point ◽

Scanning Electron

AbstractGiardia duodenalis is a protozoan parasite that causes intestinal disorders. The trophozoites present four pairs of flagella. Here we further analyze the structural organization of the anterior flagella associated structures of G. duodenalis. High resolution scanning electron microscopy of detergent-extracted trophozoites revealed novel aspects of the interaction of the anterior flagella axonemes with the marginal plates. Images of the marginal plates showed that it was located in the anterior region of the parasite, above the crossing point of the anterior flagella axonemes toward the periphery of the cell. Two well distinguished structures were seen associated with the anterior flagella. The first one corresponds to the “dense rods”, located just below the axoneme. The second one is a system of filaments located in the upper portion of the flagellum, facing the marginal plates and connecting these two structures. The thickness of the filaments is around 18 nm and they are spaced at intervals of 4–32 nm (average 18 nm). The length of the filaments may vary from 33 to 240 nm. We suggest that this filamentous structure of Giardia may help the dynamics and behavior of the anterior flagella of trophozoites during protozoan motility and adhesion, providing favorable conditions for the establishment of parasitism.

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Refractory Giardiasis in an Immunosuppressed Patient in Turkey

The Journal of Infection in Developing Countries ◽

10.3855/jidc.9669 ◽

2018 ◽

Vol 12 (03) ◽

pp. 204-207

Author(s):

Filiz Kaya ◽

Ahmet Çağkan İnkaya ◽

Salih Maçin ◽

Yakut Akyön ◽

Sibel Ergüven

Keyword(s):

Small Intestine ◽

Giardia Duodenalis ◽

Protozoan Parasite ◽

Chronic Diarrhoea ◽

Immunosuppressed Patient ◽

Predisposing Factor ◽

Giardia Infection ◽

Stool Samples ◽

Higher Doses ◽

Immunocompetent Patients

Giardiasis is an infection of the small intestine caused by the protozoan parasite Giardia duodenalis. In immunocompetent patients the infection is usually self-limited and no treatment may be needed. Immunodeficiency, however, is a predisposing factor for the development of severe Giardia infection. In this report, a case of recurrent giardiasis refractory to nitroimidazoles and nitazoxanides presented. A 28-year-old male patient with hypogammaglobulinemia admitted to our hospital because of chronic diarrhoea. Microscopic examination of stool revealed a high number of Giardia trophozoites and cysts. Treatment with higher doses and a longer course of metronidazole, trimethoprim-sulfamethoxazole, ornidazole and albendazole failed. Administration of nitazoxanide, which has been reported to be effective against Giardia duodenalis refractory to nitroimidazoles, was commenced, but his symptoms persisted and stool samples demonstrated Giardia trophozoites and cysts again.

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Giardia duodenalis and Its Secreted PPIB Trigger Inflammasome Activation and Pyroptosis in Macrophages through TLR4-Induced ROS Signaling and A20-Mediated NLRP3 Deubiquitination

Cells ◽

10.3390/cells10123425 ◽

2021 ◽

Vol 10 (12) ◽

pp. 3425

Author(s):

Lin Liu ◽

Yongwu Yang ◽

Rui Fang ◽

Weining Zhu ◽

Jingxue Wu ◽

...

Keyword(s):

Nlrp3 Inflammasome ◽

Defense Mechanisms ◽

Giardia Duodenalis ◽

Protozoan Parasite ◽

Global Scale ◽

Inflammasome Activation ◽

Giardia Infection ◽

Immune Effector ◽

Nlrp3 Inflammasome Activation ◽

Innate Immune Effector

The extracellular protozoan parasite Giardia duodenalis is a well-known and important causative agent of diarrhea on a global scale. Macrophage pyroptosis has been recognized as an important innate immune effector mechanism against intracellular pathogens. Yet, the effects of noninvasive Giardia infection on macrophage pyroptosis and the associated molecular triggers and regulators remain poorly defined. Here we initially observed that NLRP3 inflammasome-mediated pyroptosis was activated in Giardia-treated macrophages, and inhibition of ROS, NLRP3, or caspase-1 could block GSDMD cleavage, IL-1β, IL-18 and LDH release, and the cell viability reduction. We also confirmed that Giardia-induced NLRP3 inflammasome activation was involved in its K63 deubiquitination. Thus, six candidate deubiquitinases were screened, among which A20 was identified as an effective regulator. We then screened TLRs on macrophage membranes and found that upon stimulation TLR4 was tightly correlated to ROS enhancement, A20-mediated NLRP3 deubiquitination, and pyroptotic signaling. In addition, several Giardia-secreted proteins were predicted as trigger factors via secretome analysis, of which peptidyl-prolyl cis-trans isomerase B (PPIB) independently induced macrophage pyroptosis. This was similar to the findings from the trophozoite treatment, and also led to the TLR4-mediated activation of NLRP3 through K63 deubiquitination by A20. Collectively, the results of this study have significant implications for expanding our understanding of host defense mechanisms after infection with G. duodenalis.

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