Description and comparative genomic of Marseillevirus. Description and comparative genomic of Marseillevirus

Family Marseilleviridae was the second family of giant viruses to be described in 2013, after family Mimiviridae. Marseillevirus marseillevirus (MRSV) isolated in 2007 by coculture on Acanthamoeba polyphaga, is the prototype member of this family. Then, the worldwide distribution of marseillevirus was revealed by their isolation from samples of various types and sources. Thus, 48 were isolated from environmental water, one from soil, one from a dipteran, one from mussels, and two from asymptomatic humans, which led overall to the description of 53 marseillevirus isolates, including 21 by IHU Méditerranée Infection in France. Recently, five marseillevirus genomes were assembled from deep sea sediment in Norway. Isolated marseilleviruses have 250 nm icosahedral capsids and 348-404 kb long mosaic genomes that encode 386-545 predicted proteins. Comparative genomic analyses indicate that the family Marseilleviridae includes five lineages and possess a pan-genome composed of 3,082 clusters of genes. The detection of marseilleviruses in both symptomatic and asymptomatic humans in stools, blood and lymph nodes, and an up to 30-day persistence of MSRV in rats and mice, question on their possible clinical significance, which is still under investigation.