from, USA ProMed

Abstract
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"A distinct class of infectious agents, the virophages that infect
giant viruses of the _Mimiviridae_ family, has been recently
described. Here, we report the simultaneous discovery of a giant virus
of _Acanthamoeba polyphaga_ (Lentille virus) that contains an
integrated genome of a virophage (Sputnik 2), and a member of a
previously unknown class of mobile genetic elements, the
transpovirons. The transpovirons are linear DNA elements of around 7
kb that encompass 6-8 protein-coding genes, 2 of which are homologous
to virophage genes. Fluorescence in situ hybridization showed that the
free form of the transpoviron replicates within the giant virus
factory and accumulates in high copy numbers inside giant virus
particles, Sputnik 2 particles, and amoeba cytoplasm. Analysis of
deep-sequencing data showed that the virophage and the transpoviron
can integrate in nearly any place in the chromosome of the giant virus
host and that, although less frequently, the transpoviron can also be
linked to the virophage chromosome. In addition, integrated fragments
of transpoviron DNA were detected in several giant virus and Sputnik
genomes. Analysis of 19 Mimivirus strains revealed 3 distinct
transpovirons associated with 3 subgroups of Mimiviruses. The
virophage, the transpoviron, and the previously identified
self-splicing introns and inteins, constitute the complex,
interconnected mobilome of the giant viruses and are likely to
substantially contribute to interviral gene transfer."

Amoebae, large single-celled organisms, are commonly found in
air-conditioning systems in large buildings and often harbour various
bacteria and viruses inside them, which can go on to infect people
working in those buildings. The world's largest virus, a giant virus
that lurks inside amoebae and may cause pneumonia in humans, was
discovered in a sample taken from a water cooling tower in Bradford,
UK in 1992. This virus, subsequently named "_Mimivirus_," has at least
900 genes, an enormous number for a virus, and its size is more like
that of a bacterium. It can be seen using a good optical microscope,
whereas most viruses can only be visualised by electron microscopy. In
terms of DNA, it is approximately 1/5th bigger than any previously
characterised virus considered to be the largest in the world.

Now, another mimivirus, named Lentille virus, has been isolated from
an _Acanthamoeba polyphaga_ host that was present in contact lens
fluid of an eye patient, and presumably considered to be a fortuitous
contaminant. Its present significance is that it is the host of
another minivirus named _Lentille virus_. This virus contains the
integrated genome of a virophage (designated Sputnik 2) and a member
of a previously unknown class of mobile genetic elements, designated
transpovirons. The transpovirons are linear DNA elements of
approximately 7 kb that encompass 6-8 protein-encoding genes, 2 of
which are homologous to virophage genes. The free form of the
transpoviron replicates within the giant virus factory and accumulates
in high copy numbers inside giant virus particles, Sputnik 2
particles, and amoeba cytoplasm. The virophage, the transpoviron, and
the previously identified self-splicing introns and inteins constitute
the complex, interconnected mobilome of the giant viruses and are
likely to substantially contribute to interviral gene transfer.