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1.
Angew Chem Int Ed Engl ; 60(36): 19897-19904, 2021 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-34241943

RESUMO

The general perception of viruses is that they are small in terms of size and genome, and that they hijack the host machinery to glycosylate their capsid. Giant viruses subvert all these concepts: their particles are not small, and their genome is more complex than that of some bacteria. Regarding glycosylation, this concept has been already challenged by the finding that Chloroviruses have an autonomous glycosylation machinery that produces oligosaccharides similar in size to those of small viruses (6-12 units), albeit different in structure compared to the viral counterparts. We report herein that Mimivirus possesses a glycocalyx made of two different polysaccharides, now challenging the concept that all viruses coat their capsids with oligosaccharides of discrete size. This discovery contradicts the paradigm that such macromolecules are absent in viruses, blurring the boundaries between giant viruses and the cellular world and opening new avenues in the field of viral glycobiology.


Assuntos
Mimiviridae/metabolismo , Polissacarídeos/biossíntese , Glicosilação , Mimiviridae/química , Polissacarídeos/química
2.
J Virol ; 95(18): e0091921, 2021 08 25.
Artigo em Inglês | MEDLINE | ID: mdl-34191583

RESUMO

Since 2003, various viruses from the subfamily Megavirinae in the family Mimiviridae have been isolated worldwide, including icosahedral mimiviruses and tailed tupanviruses. To date, the evolutionary relationship between tailed and nontailed mimiviruses has not been elucidated. Here, we present the genomic and morphological features of a newly isolated giant virus, Cotonvirus japonicus (cotonvirus), belonging to the family Mimiviridae. It contains a linear double-stranded DNA molecule of 1.47 Mb, the largest among the reported viruses in the subfamily Megavirinae, excluding tupanviruses. Among its 1,306 predicted open reading frames, 1,149 (88.0%) were homologous to those of the family Mimiviridae. Several nucleocytoplasmic large DNA virus (NCLDV) core genes, aminoacyl-tRNA synthetase genes, and the host specificity of cotonvirus were highly similar to those of Mimiviridae lineages A, B, and C; however, lineage A was slightly closer to cotonvirus than the others were. Moreover, based on its genome size, the presence of two copies of 18S rRNA-like sequences, and the period of its infection cycle, cotonvirus is the most similar to the tupanviruses among the icosahedral mimiviruses. Interestingly, the cotonvirus utilizes Golgi apparatus-like vesicles for virion factory (VF) formation. Overall, we showed that cotonvirus is a novel lineage of the subfamily Megavirinae. Our findings support the diversity of icosahedral mimiviruses and provide mechanistic insights into the replication, VF formation, and evolution of the subfamily Megavirinae. IMPORTANCE We have isolated a new virus of an independent lineage belonging to the family Mimiviridae, subfamily Megavirinae, from the fresh water of a canal in Japan, named Cotonvirus. In a proteomic tree, this new nucleocytoplasmic large DNA virus (NCLDV) is phylogenetically placed at the root of three lineages of the subfamily Megavirinae-lineages A (mimivirus), B (moumouvirus), and C (megavirus). Multiple genomic and phenotypic features of cotonvirus are more similar to those of tupanviruses than to those of the A, B, or C lineages, and other genomic features, while the host specificity of cotonvirus is more similar to those of the latter than of the former. These results suggest that cotonvirus is a unique virus that has chimeric features of existing viruses of Megavirinae and uses Golgi apparatus-like vesicles of the host cells for virion factory (VF) formation. Thus, cotonvirus can provide novel insights into the evolution of mimiviruses and the underlying mechanisms of VF formation.


Assuntos
Acanthamoeba/virologia , Linhagem da Célula , Genoma Viral , Complexo de Golgi/virologia , Especificidade de Hospedeiro , Mimiviridae/genética , Mimiviridae/ultraestrutura , Acanthamoeba/classificação , Evolução Molecular , Tamanho do Genoma , Microscopia Eletrônica de Transmissão , Mimiviridae/classificação , Mimiviridae/isolamento & purificação , Filogenia , Vírion
3.
Mol Biol Evol ; 38(5): 2014-2029, 2021 05 04.
Artigo em Inglês | MEDLINE | ID: mdl-33570580

RESUMO

Mimivirus is one of the most complex and largest viruses known. The origin and evolution of Mimivirus and other giant viruses have been a subject of intense study in the last two decades. The two prevailing hypotheses on the origin of Mimivirus and other viruses are the reduction hypothesis, which posits that viruses emerged from modern unicellular organisms; whereas the virus-first hypothesis proposes viruses as relics of precellular forms of life. In this study, to gain insights into the origin of Mimivirus, we have carried out extensive phylogenetic, correlation, and multidimensional scaling analyses of the putative proteins involved in the replication of its 1.2-Mb large genome. Correlation analysis and multidimensional scaling methods were validated using bacteriophage, bacteria, archaea, and eukaryotic replication proteins before applying to Mimivirus. We show that a large fraction of mimiviral replication proteins, including polymerase B, clamp, and clamp loaders are of eukaryotic origin and are coevolving. Although phylogenetic analysis places some components along the lineages of phage and bacteria, we show that all the replication-related genes have been homogenized and are under purifying selection. Collectively our analysis supports the idea that Mimivirus originated from a complex cellular ancestor. We hypothesize that Mimivirus has largely retained complex replication machinery reminiscent of its progenitor while losing most of the other genes related to processes such as metabolism and translation.


Assuntos
Coevolução Biológica , Mimiviridae/genética , Seleção Genética , Proteínas Virais/genética , Replicação Viral/genética , Transferência Genética Horizontal , Análise de Escalonamento Multidimensional , Filogenia
4.
Viruses ; 12(10)2020 09 29.
Artigo em Inglês | MEDLINE | ID: mdl-33003637

RESUMO

Potassium ion (K+) channels have been observed in diverse viruses that infect eukaryotic marine and freshwater algae. However, experimental evidence for functional K+ channels among these alga-infecting viruses has thus far been restricted to members of the family Phycodnaviridae, which are large, double-stranded DNA viruses within the phylum Nucleocytoviricota. Recent sequencing projects revealed that alga-infecting members of Mimiviridae, another family within this phylum, may also contain genes encoding K+ channels. Here we examine the structural features and the functional properties of putative K+ channels from four cultivated members of Mimiviridae. While all four proteins contain variations of the conserved selectivity filter sequence of K+ channels, structural prediction algorithms suggest that only two of them have the required number and position of two transmembrane domains that are present in all K+ channels. After in vitro translation and reconstitution of the four proteins in planar lipid bilayers, we confirmed that one of them, a 79 amino acid protein from the virus Tetraselmis virus 1 (TetV-1), forms a functional ion channel with a distinct selectivity for K+ over Na+ and a sensitivity to Ba2+. Thus, virus-encoded K+ channels are not limited to Phycodnaviridae but also occur in the members of Mimiviridae. The large sequence diversity among the viral K+ channels implies multiple events of lateral gene transfer.


Assuntos
Mimiviridae/fisiologia , Canais de Potássio/fisiologia , Potássio/metabolismo , Vírus não Classificados/fisiologia , Sequência de Aminoácidos , Evolução Molecular , Genoma Viral , Canais Iônicos , Bicamadas Lipídicas , Mimiviridae/genética , Phycodnaviridae/genética , Filogenia , Canais de Potássio/classificação , Canais de Potássio/genética , Alinhamento de Sequência , Análise de Sequência , Sódio/metabolismo , Canais de Sódio , Vírus não Classificados/genética
5.
J Virol ; 94(24)2020 11 23.
Artigo em Inglês | MEDLINE | ID: mdl-32999026

RESUMO

We conducted an exhaustive search for three-dimensional structural homologs to the proteins of 20 key phylogenetically distinct nucleocytoplasmic DNA viruses (NCLDV). Structural matches covered 429 known protein domain superfamilies, with the most highly represented being ankyrin repeat, P-loop NTPase, F-box, protein kinase, and membrane occupation and recognition nexus (MORN) repeat. Domain superfamily diversity correlated with genome size, but a diversity of around 200 superfamilies appeared to correlate with an abrupt switch to paralogization. Extensive structural homology was found across the range of eukaryotic RNA polymerase II subunits and their associated basal transcription factors, with the coordinated gain and loss of clusters of subunits on a virus-by-virus basis. The total number of predicted endonucleases across the 20 NCLDV was nearly quadrupled from 36 to 132, covering much of the structural and functional diversity of endonucleases throughout the biosphere in DNA restriction, repair, and homing. Unexpected findings included capsid protein-transcription factor chimeras; endonuclease chimeras; enzymes for detoxification; antimicrobial peptides and toxin-antitoxin systems associated with symbiosis, immunity, and addiction; and novel proteins for membrane abscission and protein turnover.IMPORTANCE We extended the known annotation space for the NCLDV by 46%, revealing high-probability structural matches for fully 45% of the 9,671 query proteins and confirming up to 98% of existing annotations per virus. The most prevalent protein families included ankyrin repeat- and MORN repeat-containing proteins, many of which included an F-box, suggesting extensive host cell modulation among the NCLDV. Regression suggested a minimum requirement for around 36 protein structural superfamilies for a viable NCLDV, and beyond around 200 superfamilies, genome expansion by the acquisition of new functions was abruptly replaced by paralogization. We found homologs to herpesvirus surface glycoprotein gB in cytoplasmic viruses. This study provided the first prediction of an endonuclease in 10 of the 20 viruses examined; the first report in a virus of a phenolic acid decarboxylase, proteasomal subunit, or cysteine knot (defensin) protein; and the first report of a prokaryotic-type ribosomal protein in a eukaryotic virus.


Assuntos
Vírus de DNA/classificação , Vírus de DNA/genética , Vírus Gigantes/genética , Filogenia , Proteoma/genética , Proteínas Virais/genética , Anquirinas/genética , Citoplasma/virologia , RNA Polimerases Dirigidas por DNA , Células Eucarióticas , Evolução Molecular , Tamanho do Genoma , Genoma Viral , Mimiviridae/genética , Vaccinia/genética
6.
Emerg Infect Dis ; 26(10): 2524-2526, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32946733

RESUMO

Primary ciliary dyskinesia is a rare autosomal recessive disorder that causes oto-sino-pulmonary disease. We report a case of pulmonary infection related to mimivirus in a 10-year-old boy with primary ciliary dyskinesia that was identified using molecular techniques. Our findings indicate that the lineage C of mimivirus may cause pneumonia in humans.


Assuntos
Transtornos da Motilidade Ciliar , Mimiviridae , Pneumonia , Criança , Humanos , Masculino
7.
J Fish Dis ; 43(11): 1391-1400, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32882746

RESUMO

A group of pathogenic nucleocytoplasmic large DNA viruses (NCLDVs) related to the Mimiviridae family infect farmed sturgeons across Europe, causing mild-to-severe losses. One of these viruses, Acipenser iridovirus-European (AcIV-E), was identified in six sturgeon species. During the 2018-2019 period, nine sick Siberian (A. baerii) and Russian (A. gueldenstaedtii) sturgeons were sampled in Ukrainian farms and tested for the presence of AcIV-E using real-time PCR. The presence of AcIV-E was confirmed in some samples. High-resolution melting (HRM) assay and Sanger sequencing demonstrated the presence in three farms of two alleles of the major capsid protein (MCP) gene, called var1 and var2. Five samples carried both var1 and var2 at varying ratios, and the sixth sample was infected with only var1. These results constitute the first detection of AcIV-E in Ukraine and the first detection of a sample carrying only var1. The full-length sequences of the MCP genes confirmed the existence of two genetic lineages of AcIV-E, tentatively named V1 and V2, each displaying multiple substitutions in the MCP gene. Some of the MCP sequences showed a genetic relationship to both V1 and V2 lineages, depending on the fragment examined. Most likely, these sequences resulted from recombination events.


Assuntos
Doenças dos Peixes/virologia , Mimiviridae/genética , Animais , Aquicultura , Proteínas do Capsídeo/genética , Infecções por Vírus de DNA/veterinária , Doenças dos Peixes/epidemiologia , Peixes , Mimiviridae/classificação , Reação em Cadeia da Polimerase em Tempo Real , Análise de Sequência de DNA , Ucrânia/epidemiologia
8.
Protein Sci ; 29(11): 2164-2174, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-32797646

RESUMO

For the field of virology, perhaps one of the most paradigm-shifting events so far in the 21st century was the identification of the giant double-stranded DNA virus that infects amoebae. Remarkably, this virus, known as Mimivirus, has a genome that encodes for nearly 1,000 proteins, some of which are involved in the biosynthesis of unusual sugars. Indeed, the virus is coated by a layer of glycosylated fibers that contain d-glucose, N-acetyl-d-glucosamine, l-rhamnose, and 4-amino-4,6-dideoxy-d-glucose. Here we describe a combined structural and enzymological investigation of the protein encoded by the open-reading frame L780, which corresponds to an l-rhamnose synthase. The structure of the L780/NADP+ /UDP-l-rhamnose ternary complex was determined to 1.45 Å resolution and refined to an overall R-factor of 19.9%. Each subunit of the dimeric protein adopts a bilobal-shaped appearance with the N-terminal domain harboring the dinucleotide-binding site and the C-terminal domain positioning the UDP-sugar into the active site. The overall molecular architecture of L780 places it into the short-chain dehydrogenase/reductase superfamily. Kinetic analyses indicate that the enzyme can function on either UDP- and dTDP-sugars but displays a higher catalytic efficiency with the UDP-linked substrate. Site-directed mutagenesis experiments suggest that both Cys 108 and Lys 175 play key roles in catalysis. This structure represents the first model of a viral UDP-l-rhamnose synthase and provides new details into these fascinating enzymes.


Assuntos
Acanthamoeba/virologia , Carboidratos Epimerases/química , Mimiviridae/enzimologia , Açúcares de Uridina Difosfato/química , Proteínas Virais/química , Cristalografia por Raios X , Mimiviridae/genética , Domínios Proteicos
9.
Infect Genet Evol ; 84: 104491, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32763443

RESUMO

Sturgeon mimiviruses can cause a lethal disease of the integumentary systems of sturgeon (Acipenseridae). Here we provide phylogeographic evidence that sturgeon mimivirus is endemic in endangered populations of wild Lake Sturgeon within Canada's Hudson Bay drainage basin. Namao virus (NV) variants were diagnosed in 24% of Lake Sturgeon samples (n = 1329) collected between 2010-2015. Lake Sturgeon populations with the highest virus prevalence were from the Nelson River (58%) in 2015, Saskatchewan River (41%) in 2010 and South Saskatchewan River (36%) in 2011. Bayesian phylogenetic reconstructions suggested that four NV variants, designated HBDB I-IV, co-circulate temporally and spatially within and between the genetically and biogeographically distinct Lake Sturgeon populations. Evidence from recapture studies suggested that Lake Sturgeon across the basin are persistently infected with NV at prevalence and titer (103.6 equivalent plasmid copies per µg DNA) levels consistent with the hypothesis that wild Lake Sturgeon populations serve as a maintenance population and reservoir for sturgeon mimiviruses. Bayesian hierarchical modeling of NV in the Landing River population of Lake Sturgeon suggested that host weight and age were the best predictors of sturgeon mimivirus presence and titer, respectively, whereas water flow rate, level and temperature, and number of previous captures did not significantly improve model fit. A negative relationship was estimated between sturgeon mimivirus presence and Lake Sturgeon weight and between virus titer and Lake Sturgeon age.


Assuntos
Evolução Molecular , Doenças dos Peixes/virologia , Mimiviridae/genética , Modelos Biológicos , Animais , Teorema de Bayes , Canadá/epidemiologia , Clonagem Molecular , DNA Viral/genética , Doenças dos Peixes/epidemiologia , Peixes , Lagos , Filogenia , RNA Viral/genética , Análise de Sequência de DNA
10.
J Struct Biol ; 211(3): 107552, 2020 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-32569642

RESUMO

Uracil-N-glycosylase (UNG) is found in most organisms as well as in large DNA viruses. Its inhibitory proteins, including uracil glycosylase inhibitor (UGI) and p56, tightly bind to the active site of UNG by mimicking the DNA substrates. As the binding motifs are conserved in UNG family proteins, the inhibitory proteins bind to various UNG proteins across species. However, the intercalation residue that penetrates the DNA minor groove during uracil excision is not conserved among UNG proteins. To understand the role of the intercalation residue in their binding to the inhibitory proteins, we prepared mutants of mimivirus UNG, measured the binding affinity between the UNG mutants and inhibitory proteins, and analyzed the interactions based on the crystal structures of mimivirus UNG mutants complexed with UGI. The results show that mimivirus UNG, which harbors Tyr as an intercalation residue, did not interact with the inhibitory proteins intrinsically, whereas mutations of the intercalation residue to Phe or Leu resulted in tight interactions with UGI and p56; mutation to Met resulted in tight interactions only with p56. The crystal structures revealed that Phe and Leu stabilize the interactions by fitting into the hydrophobic pocket of UGI. These results show that differences in size and hydrophobicity of the intercalation residues determine the interactions between UNG family proteins and the inhibitory proteins, UGI and p56.


Assuntos
Mimiviridae/química , Uracila-DNA Glicosidase/química , Uracila-DNA Glicosidase/metabolismo , Proteínas Virais/química , Proteínas Virais/metabolismo , Cristalografia por Raios X , Polarização de Fluorescência , Mimiviridae/metabolismo , Mutação , Conformação Proteica , Tirosina/química , Tirosina/metabolismo , Uracila-DNA Glicosidase/genética , Proteínas Virais/genética
12.
Commun Biol ; 3(1): 248, 2020 05 21.
Artigo em Inglês | MEDLINE | ID: mdl-32439847

RESUMO

Virus adaptation to new hosts is a major cause of infectious disease emergence. This mechanism has been intensively studied in the context of zoonotic virus spillover, due to its impact on global health. However, it remains unclear for virophages, parasites of giant viruses and potential regulators of microbial communities. Here, we present, for the first time to our knowledge, evidence of cross-species infection of a virophage. We demonstrated that challenging the native population of Guarani virophage with two previously unidentified giant viruses, previously nonpermissive to this virophage, allows the selection of a mutant genotype able to infect these giant viruses. We were able to characterize the potential genetic determinant (deletion) carried by the virophage with the expanded-host range. Our study also highlights the relevant biological impact of this host adaptation by demonstrating that coinfection with the mixture containing the mutant virophage abolishes giant virus production and rescues the host cell population from lysis.


Assuntos
Acanthamoeba castellanii/virologia , Sobrevivência Celular , Vírus Gigantes/fisiologia , Interações Hospedeiro-Patógeno , Mimiviridae/fisiologia , Virófagos/fisiologia
13.
Arch Virol ; 165(6): 1267-1278, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32333117

RESUMO

Giant viruses of amoebas are a remarkable group of viruses. In addition to their large size and peculiar structures, the genetic content of these viruses is also special. Among the genetic features of these viruses that stand out is the presence of coding regions for elements involved in translation, a complex biological process that occurs in cellular organisms. No viral genome described so far has such a complex genetic arsenal as those of giant viruses, which code for several of these elements. Currently, tupanviruses have the most complete set of translation genes in the known virosphere. In this review, we have condensed what is currently known about translation genes in different groups of giant viruses and theorize about their biological importance, origin, and evolution, and what might possibly be found in the coming years.


Assuntos
Vírus Gigantes/genética , Mimiviridae/genética , Amoeba/virologia , Evolução Molecular , Genoma Viral , Vírus Gigantes/patogenicidade , Especificidade de Hospedeiro/genética , Mimiviridae/metabolismo , Mimiviridae/ultraestrutura , Filogenia , Biossíntese de Proteínas , Proteoma/genética , RNA Ribossômico 16S/genética , RNA Viral/genética
14.
Protein Sci ; 29(5): 1148-1159, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32083779

RESUMO

The exciting discovery of the giant DNA Mimivirus in 2003 challenged the conventional description of viruses in a radical way, and since then, dozens of additional giant viruses have been identified. It has now been demonstrated that the Mimivirus genome encodes for the two enzymes required for the production of the unusual sugar 4-amino-4,6-dideoxy-d-glucose, namely a 4,6-dehydratase and an aminotransferase. In light of our long-standing interest in the bacterial 4,6-dehydratases and in unusual sugars in general, we conducted a combined structural and functional analysis of the Mimivirus 4,6-dehydratase referred to as R141. For this investigation, the three-dimensional X-ray structure of R141 was determined to 2.05 Å resolution and refined to an R-factor of 18.3%. The overall fold of R141 places it into the short-chain dehydrogenase/reductase (SDR) superfamily of proteins. Whereas its molecular architecture is similar to that observed for the bacterial 4,6-dehydratases, there are two key regions where the polypeptide chain adopts different conformations. In particular, the conserved tyrosine that has been implicated as a catalytic acid or base in SDR superfamily members is splayed away from the active site by nearly 12 Å, thereby suggesting that a major conformational change must occur upon substrate binding. In addition to the structural analysis, the kinetic parameters for R141 using either dTDP-d-glucose or UDP-d-glucose as substrates were determined. Contrary to a previous report, R141 demonstrates nearly identical catalytic efficiency with either nucleotide-linked sugar. The data presented herein represent the first three-dimensional model for a viral 4,6-dehydratase and thus expands our understanding of these fascinating enzymes.


Assuntos
Hidroliases/química , Hidroliases/metabolismo , Mimiviridae/enzimologia , Açúcares/metabolismo , Cristalografia por Raios X , Hidroliases/isolamento & purificação , Modelos Moleculares , Açúcares/química
15.
Arch Virol ; 165(4): 853-863, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32052196

RESUMO

Since its discovery, the first identified giant virus associated with amoebae, Acanthamoeba polyphaga mimivirus (APMV), has been rigorously studied to understand the structural and genomic complexity of this virus. In this work, we report the isolation and genomic characterization of a new mimivirus of lineage B, named "Borely moumouvirus". This new virus exhibits a structure and replicative cycle similar to those of other members of the family Mimiviridae. The genome of the new isolate is a linear double-strand DNA molecule of ~1.0 Mb, containing over 900 open reading frames. Genome annotation highlighted different translation system components encoded in the DNA of Borely moumouvirus, including aminoacyl-tRNA synthetases, translation factors, and tRNA molecules, in a distribution similar to that in other lineage B mimiviruses. Pan-genome analysis indicated an increase in the genetic arsenal of this group of viruses, showing that the family Mimiviridae is still expanding. Furthermore, phylogenetic analysis has shown that Borely moumouvirus is closely related to moumouvirus australiensis. This is the first mimivirus lineage B isolated from Brazilian territory to be characterized. Further prospecting studies are necessary for us to better understand the diversity of these viruses so a better classification system can be established.


Assuntos
Genoma Viral , Mimiviridae/isolamento & purificação , Rios/virologia , Brasil , Genômica , Mimiviridae/classificação , Mimiviridae/genética , Mimiviridae/fisiologia , Filogenia , Replicação Viral
16.
J Virol ; 94(8)2020 03 31.
Artigo em Inglês | MEDLINE | ID: mdl-31996429

RESUMO

Microbes trapped in permanently frozen paleosoils (permafrost) are the focus of increasing research in the context of global warming. Our previous investigations led to the discovery and reactivation of two Acanthamoeba-infecting giant viruses, Mollivirus sibericum and Pithovirus sibericum, from a 30,000-year old permafrost layer. While several modern pithovirus strains have since been isolated, no contemporary mollivirus relative was found. We now describe Mollivirus kamchatka, a close relative to M. sibericum, isolated from surface soil sampled on the bank of the Kronotsky River in Kamchatka, Russian Federation. This discovery confirms that molliviruses have not gone extinct and are at least present in a distant subarctic continental location. This modern isolate exhibits a nucleocytoplasmic replication cycle identical to that of M. sibericum Its spherical particle (0.6 µm in diameter) encloses a 648-kb GC-rich double-stranded DNA genome coding for 480 proteins, of which 61% are unique to these two molliviruses. The 461 homologous proteins are highly conserved (92% identical residues, on average), despite the presumed stasis of M. sibericum for the last 30,000 years. Selection pressure analyses show that most of these proteins contribute to virus fitness. The comparison of these first two molliviruses clarify their evolutionary relationship with the pandoraviruses, supporting their provisional classification in a distinct family, the Molliviridae, pending the eventual discovery of intermediary missing links better demonstrating their common ancestry.IMPORTANCE Virology has long been viewed through the prism of human, cattle, or plant diseases, leading to a largely incomplete picture of the viral world. The serendipitous discovery of the first giant virus visible under a light microscope (i.e., >0.3 µm in diameter), mimivirus, opened a new era of environmental virology, now incorporating protozoan-infecting viruses. Planet-wide isolation studies and metagenome analyses have shown the presence of giant viruses in most terrestrial and aquatic environments, including upper Pleistocene frozen soils. Those systematic surveys have led authors to propose several new distinct families, including the Mimiviridae, Marseilleviridae, Faustoviridae, Pandoraviridae, and Pithoviridae We now propose to introduce one additional family, the Molliviridae, following the description of M. kamchatka, the first modern relative of M. sibericum, previously isolated from 30,000-year-old arctic permafrost.


Assuntos
Vírus Gigantes/classificação , Vírus Gigantes/genética , Vírus Gigantes/isolamento & purificação , Filogenia , Acanthamoeba/virologia , Vírus de DNA/classificação , Vírus de DNA/genética , Genoma Viral , Genômica , Vírus Gigantes/ultraestrutura , Mimiviridae/classificação , Mimiviridae/genética , Federação Russa , Microbiologia do Solo , Vírion/genética , Vírion/ultraestrutura , Vírus não Classificados/classificação , Vírus não Classificados/genética , Vírus não Classificados/isolamento & purificação
17.
J Med Virol ; 92(2): 187-190, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31498443

RESUMO

Marseilleviridae is a family of viruses which have only been propagated in acanthamoeba. Marseillevirus sequences have been recently detected in different human matrices by viral metagenomics. Single-center studies worldwide have estimated a low prevalence of marseillevirus both in symptomatic patients and in healthy donors but, to date, no informations are available on the prevalence of this giant virus in Italy. By a polymerase chain reaction targeting the ORF152 viral sequence, we tested sera from 197 immunosuppressed patients and 285 healthy donors, and 63 and 30 respiratory and cerebrospinal fluid samples, respectively, of patients with various clinical conditions and referring the Virology Division for diagnostic purposes. We observed no evidence of Marseillevirus DNA in all 575 samples tested. Marseillevirus probably does not cause infection in human.


Assuntos
Mimiviridae/genética , Mimiviridae/isolamento & purificação , Adulto , Idoso , Sangue/virologia , Líquido Cefalorraquidiano/virologia , Criança , Pré-Escolar , DNA Viral/isolamento & purificação , Feminino , Humanos , Imunocompetência , Hospedeiro Imunocomprometido , Itália , Masculino , Pessoa de Meia-Idade , Reação em Cadeia da Polimerase , Sistema Respiratório/virologia
18.
Proc Natl Acad Sci U S A ; 117(1): 552-562, 2020 01 07.
Artigo em Inglês | MEDLINE | ID: mdl-31871193

RESUMO

Systemic sclerosis (SSc) is a clinically heterogeneous autoimmune disease characterized by mutually exclusive autoantibodies directed against distinct nuclear antigens. We examined HLA associations in SSc and its autoantibody subsets in a large, newly recruited African American (AA) cohort and among European Americans (EA). In the AA population, the African ancestry-predominant HLA-DRB1*08:04 and HLA-DRB1*11:02 alleles were associated with overall SSc risk, and the HLA-DRB1*08:04 allele was strongly associated with the severe antifibrillarin (AFA) antibody subset of SSc (odds ratio = 7.4). These African ancestry-predominant alleles may help explain the increased frequency and severity of SSc among the AA population. In the EA population, the HLA-DPB1*13:01 and HLA-DRB1*07:01 alleles were more strongly associated with antitopoisomerase (ATA) and anticentromere antibody-positive subsets of SSc, respectively, than with overall SSc risk, emphasizing the importance of HLA in defining autoantibody subtypes. The association of the HLA-DPB1*13:01 allele with the ATA+ subset of SSc in both AA and EA patients demonstrated a transancestry effect. A direct correlation between SSc prevalence and HLA-DPB1*13:01 allele frequency in multiple populations was observed (r = 0.98, P = 3 × 10-6). Conditional analysis in the autoantibody subsets of SSc revealed several associated amino acid residues, mostly in the peptide-binding groove of the class II HLA molecules. Using HLA α/ß allelic heterodimers, we bioinformatically predicted immunodominant peptides of topoisomerase 1, fibrillarin, and centromere protein A and discovered that they are homologous to viral protein sequences from the Mimiviridae and Phycodnaviridae families. Taken together, these data suggest a possible link between HLA alleles, autoantibodies, and environmental triggers in the pathogenesis of SSc.


Assuntos
Autoanticorpos/imunologia , Autoantígenos/genética , Antígenos HLA/genética , Mimetismo Molecular/imunologia , Escleroderma Sistêmico/genética , Afro-Americanos/genética , Alelos , Sequência de Aminoácidos/genética , Antígenos Virais/genética , Antígenos Virais/imunologia , Autoantígenos/imunologia , Biologia Computacional , Conjuntos de Dados como Assunto , Grupo com Ancestrais do Continente Europeu/genética , Feminino , Predisposição Genética para Doença , Antígenos HLA/imunologia , Humanos , Masculino , Mimiviridae/imunologia , Phycodnaviridae/imunologia , Estrutura Secundária de Proteína/genética , Medição de Risco , Escleroderma Sistêmico/epidemiologia , Escleroderma Sistêmico/imunologia , Homologia de Sequência de Aminoácidos
19.
ISME J ; 14(3): 727-739, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-31822788

RESUMO

Acanthamoeba-infecting Mimiviridae are giant viruses with dsDNA genome up to 1.5 Mb. They build viral factories in the host cytoplasm in which the nuclear-like virus-encoded functions take place. They are themselves the target of infections by 20-kb-dsDNA virophages, replicating in the giant virus factories and can also be found associated with 7-kb-DNA episomes, dubbed transpovirons. Here we isolated a virophage (Zamilon vitis) and two transpovirons respectively associated to B- and C-clade mimiviruses. We found that the virophage could transfer each transpoviron provided the host viruses were devoid of a resident transpoviron (permissive effect). If not, only the resident transpoviron originally isolated from the corresponding virus was replicated and propagated within the virophage progeny (dominance effect). Although B- and C-clade viruses devoid of transpoviron could replicate each transpoviron, they did it with a lower efficiency across clades, suggesting an ongoing process of adaptive co-evolution. We analysed the proteomes of host viruses and virophage particles in search of proteins involved in this adaptation process. This study also highlights a unique example of intricate commensalism in the viral world, where the transpoviron uses the virophage to propagate and where the Zamilon virophage and the transpoviron depend on the giant virus to replicate, without affecting its infectious cycle.


Assuntos
Acanthamoeba/virologia , Mimiviridae/fisiologia , Vírus Gigantes/genética , Vírus Gigantes/fisiologia , Mimiviridae/genética , Mimiviridae/crescimento & desenvolvimento , Mimiviridae/isolamento & purificação , Simbiose , Virófagos/genética , Virófagos/fisiologia
20.
Viruses ; 11(12)2019 12 04.
Artigo em Inglês | MEDLINE | ID: mdl-31817274

RESUMO

Giant viruses, like pandoraviruses and mimiviruses, have been discovered from diverse environments, and their broad global distribution has been established. Here, we report two new isolates of Pandoravirus spp. and one Mimivirus sp., named Pandoravirus hades, Pandoravirus persephone, and Mimivirus sp. isolate styx, co-isolated from riverbank soil in Japan. We obtained nearly complete sequences of the family B DNA polymerase gene (polB) of P. hades and P. persephone; the former carried two known intein regions, while the latter had only one. Phylogenetic analysis revealed that the two new pandoravirus isolates are closely related to Pandoravirus dulcis. Furthermore, random amplified polymorphic DNA analysis revealed that P. hades and P. persephone might harbor different genome structures. Based on phylogenetic analysis of the partial polB sequence, Mimivirus sp. isolate styx belongs to mimivirus lineage A. DNA staining suggested that the Pandoravirus spp. asynchronously replicates in amoeba cells while Mimivirus sp. replicates synchronously. We also observed that P. persephone- or Mimivirus sp. isolate styx-infected amoeba cytoplasm is extruded by the cells. To the best of our knowledge, we are the first to report the isolation of pandoraviruses in Asia. In addition, our results emphasize the importance of virus isolation from soil to reveal the ecology of giant viruses.


Assuntos
Vírus de DNA/isolamento & purificação , Mimiviridae/isolamento & purificação , Amoeba/ultraestrutura , Amoeba/virologia , Vírus de DNA/classificação , Japão/epidemiologia , Mimiviridae/classificação , Técnicas de Amplificação de Ácido Nucleico , Filogenia , Microbiologia do Solo
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