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A paradigm for virus-host coevolution: sequential counter-adaptations between endogenous and exogenous retroviruses
Frederick Arnaud1, Marco Caporale, Mariana Varela
1Institute of Comparative Medicine, University of Glasgow Veterinary School, Glasgow, Scotland.
Plos Pathogens
|November 14, 2007
Summary
Endogenous retroviruses (ERVs) can act as host defense mechanisms against pathogenic retroviruses. This study shows sheep ERVs evolved to block exogenous retroviruses, demonstrating an evolutionary arms race.
Area of Science:
- * Virology
- * Evolutionary Biology
- * Immunology
Background:
- * Endogenous retroviruses (ERVs) are integrated into host germlines, passed vertically.
- * ERVs are hypothesized to function as restriction factors against exogenous retroviral infections.
- * Sheep harbor exogenous and related endogenous retroviruses, offering a model for coevolutionary studies.
Purpose of the Study:
- * To investigate the evolutionary history and molecular virology of endogenous Jaagsiekte sheep retroviruses (enJSRVs).
- * To understand the coevolutionary dynamics between enJSRVs and exogenous retroviruses in sheep.
- * To determine if ERVs have evolved as restriction factors in the sheep model.
Main Methods:
- * Isolation and characterization of 27 enJSRV proviruses.
- * Analysis of evolutionary history and integration timelines.
- * Molecular virology to assess viral replication and host-pathogen interactions.
Main Results:
- * enJSRVs integrated into the sheep genome over the last 5-7 million years.
- * Two enJSRV proviruses (enJS56A1, enJSRV-20) evolved a transdominant phenotype to block exogenous retroviral replication.
- * A provirus emerged that escaped this restriction, indicating ongoing evolutionary antagonism.
Conclusions:
- * Endogenization and selection of ERVs as restriction factors is a host defense strategy against retroviral infections.
- * Sheep ERVs provide evidence for an evolutionary arms race between endogenous and exogenous retroviruses.
- * This study highlights the dynamic interplay between retroviruses and their hosts over evolutionary timescales.
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