2021-11-17Zeitschriftenartikel
A Comprehensive Analysis of Human Endogenous Retroviruses HERV-K (HML.2) from Teratocarcinoma Cell Lines and Detection of Viral Cargo in Microvesicles
About 8% of our genome is composed of sequences from Human Endogenous Retroviruses
(HERVs). The HERV-K (HML.2) family, here abbreviated HML.2, is able to produce virus particles that
were detected in cell lines, malignant tumors and in autoimmune diseases. Parameters and properties
of HML.2 released from teratocarcinoma cell lines GH and Tera-1 were investigated in detail. In most
experiments, analyzed viruses were purified by density gradient centrifugation. HML.2 structural
proteins, reverse transcriptase (RT) activity, viral RNA (vRNA) and particle morphology were
analyzed. The HML.2 markers were predominantly detected in fractions with a buoyant density of
1.16 g/cm3. Deglycosylation of TM revealed truncated forms of transmembrane (TM) protein. Free
virions and extracellular vesicles (presumably microvesicles—MVs) with HML.2 elements, including
budding intermediates, were detected by electron microscopy. Viral elements and assembled virions
captured and exported by MVs can boost specific immune responses and trigger immunomodulation
in recipient cells. Sequencing of cDNA clones demonstrated exclusive presence of HERV-K108 env
in HML.2 from Tera-1 cells. Not counting two recombinant variants, four known env sequences
were found in HML.2 from GH cells. Obtained results shed light on parameters and morphology of
HML.2. A possible mechanism of HML.2-induced diseases is discussed.
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