Questions on unusual Mimivirus-like structures observed in human cells

Abstract

Background: Mimiviruses or giant viruses that infect amoebas have the ability to retain the Gram stain, which is usually used to colour bacteria. There is some evidence suggesting that Mimiviruses can also infect human cells. Guided by these premises, we performed a routine Gram stain on a variety of human specimens to see if we could detect the same Gram positive blue granules that identify Mimiviruses in the amoebas. Methods: We analysed 24 different human specimens (liver, brain, kidney, lymph node and ovary) using Gram stain histochemistry, electron microscopy immunogold, high resolution mass spectrometry and protein identification. Results: We detected in the human cells Gram positive granules that were distinct from bacteria. The fine blue granules displayed the same pattern of the Gram positive granules that diagnose Mimiviruses in the cytoplasm of the amoebas. Electron microscopy confirmed the presence of human Mimiviruses-like structures and mass spectrometry identified histone H4 peptides, which had the same footprints as giant viruses. However, some differences were noted: the Mimivirus-like structures identified in the human cells were ubiquitous and manifested a distinct mammalian retroviral antigenicity. Conclusions: Our main hypotheses are that the structures could be either giant viruses having a retroviral antigenicity or ancestral cellular components having a viral origin. However, other possible alternatives have been proposed to explain the nature and function of the newly identified structures.

Discovery and description of the first human Retro-Giant virus

“…Gram positive blue granules that disclosed the existence of giant viruses in the amoeba, similarly detected this newly giant virus in human cells both in our previous study 1 and current study.…”

“…The `viral factories` and viral histone H4, described in our previous study 1 , suggests a protected system that hijacks host immunity and epigenetics to enhance viral replication.…”

“…Our previous paper described the presence of unusual Mimiviruses-like structures in human tissues 1 . Like Mimiviruses (~450 nm giant viruses found in the amoebas), these human structures had the ability to retain Gram staining, and mass spectrometry revealed the presence of histone peptides that had the same footprints as giant viruses [2][3][4][5][6][7][8][9] .…”

Discovery of the First Human Retro-Giant Virus: Description of its morphology, retroviral kinase and ability to induce tumours in mice

“…Our previous paper described the presence of unusual Mimiviruses-like structures in human tissues 1 . Like Mimiviruses (~450 nm giant viruses found in the amoeba), these human structures had the ability to retain Gram staining, and mass spectrometry revealed the presence of histone peptides that had the same footprints as giant viruses [2][3][4][5][6][7][8] .…”

Boiling Acid Mimics Intracellular Giant Virus Genome Release

“…GV have been isolated from a wide variety of hosts, including amoeba (Aherfi et al, 2016b), animals Andrade et al, 2015;Dornas et al, 2014a;Khan et al, 2007), as well as human and murine cells (Ghigo et al, 2008;Lusi et al, 2017). However, amoebas also infect these creatures, casting doubt on the true viral reservoir.…”