Tropism Testing – Facts Challenges Vision Arevir Meeting May 2011
Therapy examples • situation I: – Therapy: Kaletra/AZT/3TC virus: wt – after 1 year: PR: L63P RT: 41L, 215Y, 184V • what to change? • Who is out!
Therapy examples • situation II: – Therapy: AZT/3TC/MVC; virus: wt, R5- tropic – after 1 year: RT: 41L, 215Y, X4-tropic • who is out and why ??
Stability of Tropism under ART
Resistance vs. Tropism shift • HIV exposure to drug selects for resistance = virus becomes non-responsive • After resistance selection: the affected drug is lost! • CCR5 antagonists select resistances within R5 ‐ tropic viruses! • Tropism shift under MVC therapy is NOT a “resistance”! = a selection mechanism for existing X4 ‐ tropic virus or for new virus evolution • X4 viruses emerge under insufficient backbone pressure! • Disappears when MVC is removed!(?)
Challenges of R-Testing remain… (will we ever need it?)
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