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SARS-CoV-2 variants have become a major virological, epidemiological, and clinical concern, particularly with regard to the risk of escape from vaccine-induced immunity. Here, we describe the emergence of a new variant, with the index case returning from travel in Cameroon. For 13 SARS-CoV-2-positive patients living in the same geographical area of southeastern France, a qPCR test for screening variant-associated mutations showed an atypical combination. The genome sequences were obtained by next-generation sequencing with Oxford Nanopore Technologies on GridION instruments within about 8 h. Analysis revealed 46 nucleotide substitutions and 37 deletions, resulting in 30 amino acid substitutions and 12 deletions. Fourteen of the amino acid substitutions, including N501Y and E484K, and nine deletions are located in the spike protein. This genotype pattern led to the establishment of a new Pangolin lineage, named B.1.640.2, that is a phylogenetic sister group to the old B.1.640 lineage, which has now been renamed B.1.640.1. The lineages differ by 25 nucleotide substitutions and 33 deletions. The combination of mutations in these isolates and their phylogenetic position indicate, based on our previous definition, that they represent a new variant, which we have named "IHU". These data are a further example of the unpredictability of the emergence of SARS-CoV-2 variants, and of their possible introduction into a given geographical area from abroad. [ABSTRACT FROM AUTHOR]

We detected SARS-CoV-2 of PANGO lineage R.1 with the spike substitution E484K in three patients. Eleven other sequences in France and 8,831 worldwide were available from GISAID, 92% originating from Japan. The three genome sequences from our institute were phylogenetically closest to another from Guinea-Conakry, where one of the patients had travelled. These viruses did not exhibit any unusual features in cell culture. Spike structural predictions indicated a 1.3-time higher transmissibility index than for the globally spread B.1.1.7 variant but also an affinity loss for gangliosides that might have slowed dissemination. The spread of new SARS-CoV-2 mutants/variants is still not well understood and therefore difficult to predict, and this hinders implementation of effective preventive measures, including adapted vaccines. [ABSTRACT FROM AUTHOR]

Marseillevirus is the founding member of the proposed family Marseilleviridae, which is the second discovered family of giant viruses that infect amoebae. These viruses have been recovered from environmental water samples and, more recently, from humans. Tunisvirus was isolated from fountain water in Tunis, Tunisia, by culturing on Acanthamoeba spp. and is a new marseillevirus. We describe here its 380,011 base-pair genome. A total of 484 proteins were identified, among which 320 and 358 have an ortholog in Marseillevirus and Lausannevirus (e-value <1e-2), respectively, and 259 and 299 have best reciprocal hits with a Marseillevirus and a Lausannevirus protein, respectively. In addition, a significant hit was found in organisms other than marseilleviruses for 144 Tunisvirus proteins, indicating extensive lateral gene transfers, as has been demonstrated previously for Marseillevirus. Finally, a total of 21 ORFans were identified. Phylogeny reconstructions and analysis of the gene repertoires of marseilleviruses, including the proportion of orthologs and the mean amino acid identity between genes in pairs, suggest that the proposed family Marseilleviridae encompasses three lineages. Lineage A is composed of Marseillevirus, Cannes 8 virus and Senegalvirus; lineage B is represented by Lausannevirus alone; and lineage C has Tunisvirus as its first member. Taken together, these findings suggest that the marseilleviruses display a substantial level of diversity. [ABSTRACT FROM AUTHOR]

The nucleocytoplasmic large DNA viruses (NCLDVs) comprise a monophyletic group of viruses that infect animals and diverse unicellular eukaryotes. The NCLDV group includes the families Poxviridae, Asfarviridae, Iridoviridae, Ascoviridae, Phycodnaviridae, Mimiviridae and the proposed family “Marseilleviridae”. The family Mimiviridae includes the largest known viruses, with genomes in excess of one megabase, whereas the genome size in the other NCLDV families varies from 100 to 400 kilobase pairs. Most of the NCLDVs replicate in the cytoplasm of infected cells, within so-called virus factories. The NCLDVs share a common ancient origin, as demonstrated by evolutionary reconstructions that trace approximately 50 genes encoding key proteins involved in viral replication and virion formation to the last common ancestor of all these viruses. Taken together, these characteristics lead us to propose assigning an official taxonomic rank to the NCLDVs as the order “Megavirales”, in reference to the large size of the virions and genomes of these viruses. [ABSTRACT FROM AUTHOR]

The family 'Marseilleviridae' is a new proposed taxon for giant viruses that infect amoebae. Its first member, Acanthamoeba polyphaga marseillevirus (APMaV), was isolated in 2007 by culturing on amoebae a water sample collected from a cooling tower in Paris, France. APMaV has an icosahedral shape with a diameter of ≈250 nm. Its genome is a double-stranded circular DNA that is 368,454 base pairs (bp) in length. The genome has a GC content of 44.7 % and is predicted to encode 457 proteins. Phylogenetic reconstructions showed that APMaV belongs to a new viral family among nucleocytoplasmic large DNA viruses, a group of viruses that also includes Acanthamoeba polyphaga mimivirus (APMV) and the other members of the family Mimiviridae as well as the members of the families Poxviridae, Phycodnaviridae, Iridoviridae, Ascoviridae, and Asfarviridae. In 2011, Acanthamoeba castellanii lausannevirus (ACLaV), another close relative of APMaV, was isolated from river water in France. The ACLaV genome is 346,754 bp in size and encodes 450 genes, among which 320 have an APMaV protein as the closest homolog. Two other giant viruses closely related to APMaV and ACLaV have been recovered in our laboratory from a freshwater sample and a human stool sample using an amoebal co-culture method. The only currently identified hosts for 'marseilleviruses' are Acanthamoeba spp. The prevalence of these viruses in the environment and in animals and humans remains to be determined. [ABSTRACT FROM AUTHOR]