Similarities between novel cellular structures identified in human liver and ancient terrestrial giant Mimiviruses.

  1. 1.  St Vincent Health Care Group, Dublin, Ireland
  2. 2.  Department of Biology, Electron Microscopy Unit, University of Padua, Italy
  3. 3.  St Camillo Hospital of Rome, Liver Unit

Novel human cellular structures have been identified in the hepatocytes of patients with a variety of chronic liver diseases, chronic unexplained hepatitis  and liver specimens with no histological lesions.

Electron Microscopy (EM) assays were carried out in two different international Centres that were blind to each. Ten liver specimens from different patients were analysed by EM immunogold and more that 600 micrographs were scrutinized. For this presentation, we narrowed the choice down to one striking image  (figure 1).

The human cellular structures, scattered in the cytoplasm of the hepatocytes, have strong similarities with Mimiviruses, terrestrial giant viruses that are also able to infect mammals (Campos et al. Virology Journal 2014). Note the morphological similarities between the human structures with Mimiviruses in the reported picture.

Further investigations are now required to establish if the newly identified human cellular structures are giant viruses infecting humans or ubiquitous eukaryotic cellular structures having an evolutionary link with giant viruses.

Figure 1. Electron Microscopy Immunogold, human liver cells. Striking similarities between  human liver structures ( section 1.) with giant Mimiviruses described by Campos (2).  Compare the two viral factories (VF) and the giant particles (red arrows) in section 1. and section 2. However, the human cellular structures (section 1.) display an antigenicity that is not typical for giant viruses and its nature needs to be clarified with additional experiments.

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    Walter Kyle
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    The data appears to more than support the authors conclusions.  

    The two systems appear to consist of a Viral Factory (VF), generated viruses with microvilli, and virophages.  The authors do not identify the virophages (black dots) in Photo 1 which seem to match the size of the virophages in Photo 2 and comprise a recognized component of  Nucleocytoplasmic large DNA viruses (NCLDVs) systems. Photo 1 depicts these virophages (black dots) exuding from the Viral Factory (VF) whilst the 450 nm identified virus particle seems to have torn away from the VF.   Under the V in Photo 1 a darkened slice which approximates the size of the lower labia-like tear in the VF may be another particle, richer in RNA antigenicity, preparing to break away.  

    The Samba Mimivirus system depicted in Photo 2 seems to a exhibit a more developed system which generates the classical hexagonal shaped Mimiviruses in large numbers and a more ordered fashion that might be either attributed to antiquity or host habitat factors.   One might interpret the retroviral antigenicity and crude replication of the human liver structure to predate the Samba Mimivirus and others might not.

    The consistent retroviral antigenicity the authors report in the virophages (black dots), VF and virus particle have not to my knowledge been found in NCLDVs which makes this mega virus system unique to human hepatocytes, cells which interestingly like amoebas - host cells for previously reported NCLDVs, are capable of regeneration.   

    Hepatocyte cell size regulation in rats has been reported a function of the RNA:DNA ratio which raises a question for the authors - "Is this giant human liver structure's Viral Factory that generates virophages with retroviral antigenicity a factor in some cases of liver inflammation -  hepatitis?"

    Walter S. Kyle
    24-May-2016
    I have no professional conflicts with authors.



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