Journal Article

HIV-1 Drug Resistance in the iPrEx Preexposure Prophylaxis Trial

Teri Liegler, Mohamed Abdel-Mohsen, L. Gordon Bentley, Robert Atchison, Timothy Schmidt, Jacqueline Javier, Megha Mehrotra, Christopher Eden, David V. Glidden, Vanessa McMahan, Peter L. Anderson, Peilin Li, Joseph K. Wong, Susan Buchbinder, Juan V. Guanira and Robert M. Grant

in The Journal of Infectious Diseases

Published on behalf of Infectious Diseases Society of America

Volume 210, issue 8, pages 1217-1227
Published in print October 2014 | ISSN: 0022-1899
Published online April 2014 | e-ISSN: 1537-6613 | DOI:

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  • Infectious Diseases
  • Immunology
  • Public Health and Epidemiology
  • Microbiology


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Background. The iPrEx study demonstrated that combination oral emtricitabine and tenofovir disoproxil fumarate (FTC/TDF) as preexposure prophylaxis (PrEP) protects against HIV acquisition in men who have sex with men and transgender women. Selection for drug resistance could offset PrEP benefits.

Methods. Phenotypic and genotypic clinical resistance assays characterized major drug resistant mutations. Minor variants with FTC/TDF mutations K65R, K70E, M184V/I were measured using 454 deep sequencing and a novel allele-specific polymerase chain reaction (AS-PCR) diagnostic tolerant to sequence heterogeneity.

Results. Control of primer-binding site heterogeneity resulted in improved accuracy of minor variant measurements by AS-PCR. Of the 48 on-study infections randomized to FTC/TDF, none showed FTC/TDF mutations by clinical assays despite detectable drug levels in 8 participants. Two randomized to FTC/TDF had minor variant M184I detected at 0.53% by AS-PCR or 0.75% by deep sequencing, only 1 of which had low but detectable drug levels. Among those with acute infection at randomization to FTC/TDF, M184V or I mutations that were predominant at seroconversion waned to background levels within 24 weeks after discontinuing drug.

Conclusions. Drug resistance was rare in iPrEx on-study FTC/TDF-randomized seroconverters, and only as low-frequency minor variants. FTC resistance among those initiating PrEP with acute infection waned rapidly after drug discontinuation.

Clinical Trials Registration. NCT00458393.

Keywords: 454 deep sequencing; AS-PCR; drug resistance; HIV-1; minor variant; preexposure prophylaxis; PrEP; FTC/TDF

Journal Article.  5770 words.  Illustrated.

Subjects: Infectious Diseases ; Immunology ; Public Health and Epidemiology ; Microbiology

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