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Different models, different trees: the geographic origin of PTLV-I
C R Kelsey1, K A Crandall, A F Voevodin
1Department of Zoology, Brigham Young University, Provo, Utah 84602-5255, USA.
Molecular Phylogenetics and Evolution
|December 22, 1999
Summary
Investigating human and simian T-cell lymphotropic virus type I (HTLV-I/STLV-I) evolution, this study found unequal evolutionary rates between lineages. Phylogenetic analyses suggest an African origin for these primate T-lymphotropic viruses.
Area of Science:
- Virology
- Evolutionary Biology
- Genomics
Background:
- Human T-cell lymphotropic virus type I (HTLV-I) and simian T-cell lymphotropic virus type I (STLV-I) are closely related retroviruses with significant global health implications.
- Understanding their evolutionary history and geographic origins is crucial for tracing viral transmission and developing effective control strategies.
Purpose of the Study:
- To investigate the evolutionary rates and geographic origins of HTLV-I and STLV-I using nucleotide sequence data from three distinct genomic regions.
- To test hypotheses regarding the evolutionary divergence and ancestral location of these primate T-lymphotropic viruses (PTLV).
Main Methods:
- Analysis of nucleotide sequences from pol, LTR, and env regions of HTLV-I/STLV-I.
- Application of the likelihood ratio test to assess evolutionary rates and compare models of evolution.
- Construction of phylogenetic trees using multiple phylogenetic techniques to infer ancestral origins.
Main Results:
- Demonstrated unequal rates of evolution along HTLV-I and STLV-I lineages, challenging the reliability of pairwise distances for determining viral ancestry.
- Identified conflicting results when using different evolutionary models, indicating the importance of statistically justified model selection.
- While neither African nor Asian origin hypotheses could be statistically rejected, best phylogenetic estimates supported an African origin for PTLV across all analyzed gene regions.
Conclusions:
- The evolutionary trajectory of HTLV-I/STLV-I is characterized by unequal divergence rates, necessitating advanced phylogenetic methods for accurate ancestry inference.
- Phylogenetic analyses provide strong support for an African origin of primate T-lymphotropic viruses, despite statistical ambiguities in origin-testing.
- This research underscores the importance of rigorous evolutionary modeling in understanding the deep history and dissemination of human and simian viruses.
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