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Published on: November 12, 2015
Isolation and characterization of retrovirus-like elements from normal human fetuses
International Journal of Cancer
|September 15, 1982
Summary
Retrovirus-like particles found in human fetal tissues contain reverse transcriptase and endogenous RNA. Their presence correlates with embryonic differentiation, suggesting they are retroviral elements, not infectious retroviruses.
Area of Science:
- Virology
- Molecular Biology
- Developmental Biology
Background:
- Retrovirus-like particles (RLPs) have been detected in human fetal samples.
- Understanding the nature and origin of these particles is crucial for human developmental biology.
Purpose of the Study:
- To characterize RLPs isolated from human fetal tissues.
- To investigate the relationship between RLP expression and embryonic differentiation.
Main Methods:
- Isolation and density gradient centrifugation of particles from fetal plasma and organs.
- Electron microscopy for particle morphology.
- Enzymatic assays for reverse transcriptase (RT) activity using various template-primers.
- Inhibition assays using antisera against known RTs.
- RNA-DNA hybridization to determine nucleic acid origin and integration.
Main Results:
- RLPs were isolated from fetal plasma and embryonic organs, with densities of 1.19-1.22 g/ml and some lighter particles (1.15-1.17 g/ml).
- Electron microscopy revealed retrovirus-like morphology. Particles contained high molecular weight RNAs (70S and 35S) and RT activity.
- RT showed partial inhibition (40%) by antiserum against feline endogenous virus (RD114) RT, but no inhibition by antisera against AMV, SNV, or GALV RT.
- Complementary DNA hybridized to adult human DNA, indicating endogenous origin.
- RLPs were exclusively found in embryonic organs during differentiation and could not be induced.
Conclusions:
- The isolated particles are endogenous retroviral elements, not infectious retroviruses, due to lack of induced expression and demonstrated infectivity.
- Retroviral gene expression appears correlated with embryonic differentiation in humans.
- These findings contribute to understanding endogenous retroviral elements in human development.
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