3rd International Workshop on HIV Drug Resistance 2-5 August 1994, Kauai, Hawaii, USA

NOVEL MUTATIONS IN HIV-1 REVERSE TRANSCRIPTASE CONFER RESISTANCE TO FOSCARNET IN LABORATORY AND CLINICAL ISOLATES

Int Wkshop HIV Drug Res 1994 Aug 2-5;3:24 (abstract no. 23)

J. Mellors¹, H. Bazmi¹, J. Weir², E. Arnold³, R. Schinazi⁴, D. Mayers^2
1University of Pittsburgh/VA Medical Center, Pittsburgh, PA; ²Military Medical Consortium for Applied Retroviral Research, Bethesda, MD; ³Center for Advanced Biotechnology and Medicine, Piscataway, NJ; ⁴Emory UniversityNA Medical Center, Atlanta, GA, USA

Foscarnet (FOS) is a DNA polymerase inhibitor with in vivo activity against CMV and HIV-l. Resistance of HIV-1 to FOS has not been reported despite long-term FOS therapy of HIV-infected patients with CMV infection. We evaluated the potential for HIV-1 resistance to FOS by serial passage of virus in 400 µM drug. After 13 passages, virus exhibiting 8- to 10-fold FOS resistance was isolated. Virion-associated RT showed similar FOS resistance (8- to 10-fold) in RT inhibition assays. FOS-resistant virus was ~50-fold hyper-susceptible to AZT and ~10-fold hyper-susceptible to TIBO R82150 and nevirapine. DNA sequence analysis of RT identified the co-existence of two amino acid substitutions in all resistant clones: Gln¹⁶¹ to Leu and His²⁰⁸ to Tyr. Genetic analysis of HIV-1 from five patients on long-term FOS therapy (>3 months) revealed the Tyr²⁰⁸ mutation in two, the Leu¹⁶¹ mutation in one, and a Trp⁸⁸ to Ser or Gly mutation in four patients. Site-specific mutagenesis and production of mutant recombinant HIV-1 demonstrated that the Leu¹⁶¹ and Tyr²⁰⁸ mutation together or the Se⁸⁸ mutation alone conferred FOS resistance. In the crystal structure of RT, the Gln¹⁶¹ residue is just beneath the putative dNTP binding site. Substitution of Gln¹⁶¹ to Leu may alter the structure of the dNTP binding site and its affinity for FOS. The Se⁸⁸ substitution probably affects template binding, as do several nucleoside drug resistance mutations. HIV-1 resistance to FOS can develop and is caused by novel mutations in RT at template and dNTP binding sites.

Download PDF of this abstract.

1994-08-02
23

Copyright © 1994 - International Medical Press Ltd. Reproduction of this abstract (other than one copy for personal reference) must be cleared through the International Medical Press Ltd. 2-4 Idol Lane, London EC3R 5DD UK.