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Equine infectious anemia virus genomic evolution in progressor and nonprogressor ponies
C Leroux1, J K Craigo, C J Issel
1Department of Molecular Genetics and Biochemistry, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA.
Journal of Virology
|April 20, 2001
Summary
Equine infectious anemia virus (EIAV) envelope variation persists during infection, independent of replication levels. This viral evolution continues even with low virus replication, aiding immune evasion.
Area of Science:
- Virology
- Immunology
- Evolutionary Biology
Background:
- Lentivirus persistence relies on genetic and antigenic variation.
- Viral replication rate is thought to correlate with genetic variation.
- Equine infectious anemia virus (EIAV) serves as a model for lentiviral evolution.
Purpose of the Study:
- To investigate the relationship between EIAV replication levels and envelope variation.
- To determine if EIAV envelope variation differs based on clinical progression and viremia.
- To explore the patterns of EIAV envelope variation during long-term asymptomatic infection.
Main Methods:
- Experimental infection of ponies with EIAV over 2.5 years.
- Monitoring of clinical progression and plasma virus genomic RNA levels.
- Analysis of EIAV envelope gp90 variation using sequence analysis.
Main Results:
- Similar extents of EIAV envelope gp90 variation were observed regardless of disease cycles or viremia.
- Envelope variation was independent of steady-state replication levels, from undetectable to 10(5) copies/ml.
- Distinct viral quasispecies evolved during acute and chronic EIA, with ongoing variation during asymptomatic infection.
Conclusions:
- EIAV variation is associated with low-level replication and selection in target tissues, not just high plasma viremia.
- Envelope variation continues throughout all stages of persistent EIAV infection.
- This ongoing variation contributes to the virus's ability to evade host immune responses.