Mapping Evolutionary Pathways of HIV-1 Drug Resistance Using Conditional Selection Pressure
Presenter
March 4, 2008
Keywords:
- Evolutionary
MSC:
- 91A22
Abstract
Can genomics provide a new level of strategic intelligence about
rapidly evolving pathogens? We have developed a new approach to
measure the rates of all possible evolutionary pathways in a genome,
using conditional Ka/Ks to estimate their "evolutionary velocity",
and have applied this to several datasets, including clinical
sequencing of 50,000 HIV-1 samples. Conditional Ka/Ks predicts the
preferred order and relative rates of competing evolutionary
pathways. We recently tested this approach using independent data
generously provided by Shafer and coworkers (Stanford HIV Database),
in which multiple samples collected at different times from each
patient make it possible to track which mutations occurred first
during this time-course. Out of 35 such mutation pairs in protease
and RT, conditional Ka/Ks correctly predicted the experimentally
observed order in 28 cases (p=0.00025). Conditional Ka/Ks data
reveal specific accessory mutations that greatly accelerate the
evolution of multi-drug resistance. Our analysis was highly
reproducible in four independent datasets, and can decipher a
pathogen's evolutionary pathways to multi-drug resistance even while
such mutants are still rare. Analysis of samples from untreated
patients shows that these rapid evolutionary pathways are
specifically associated with drug treatment, and vanish in its absence.