18 research outputs found
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Characterization of HIV seroconverters in a TDF/FTC PrEP study: HPTN 067/ADAPT
Background: HPTN 067/ADAPT evaluated tenofovir disoproxil fumarate/emtricitabine (TDF/FTC) pre-exposure prophylaxis (PrEP) in women (South Africa) and men who have sex with men (Thailand, US). Participants received once-weekly directly observed TDF/FTC (DOT), and were then randomized to daily, time-driven, or event-driven PrEP. This report describes characterization of 12 HIV seroconversion events in this trial.
Methods: HIV rapid testing was performed at study sites. Retrospective testing included: 4th generation assays; HIV RNA testing; Western blot; an HIV-1/2 discriminatory assay; resistance testing; and antiretroviral (ARV) drug testing.
Results: Six of the 12 seroconverters received TDF/FTC in the DOT phase, but were not randomized (3 were acutely infected at enrollment; 2 were infected during the DOT phase; one was not randomized due to pregnancy). One of the six randomized participants had acute infection at randomization but was not diagnosed for 3–4 months because HIV rapid tests were non-reactive; continued daily PrEP use was associated with false-negative antibody tests and low HIV RNA levels. The five participants infected after randomization included four with low adherence to the PrEP regimen, and one who reported a 7-day period without dosing prior to infection. Three participants had TDF/FTC resistance (M184I, K65R), including two who received only four once-weekly TDF/FTC doses; most TDF/FTC mutations were detected by next generation sequencing only.
Conclusions: In HPTN 067/ADAPT, participants who acquired HIV infection had infrequent PrEP dosing or low/suboptimal adherence. Sensitive assays improved detection of HIV infection and drug resistance. Drug resistance was observed with limited PrEP exposure
Discovery of genetic variants of the kinases that activate tenofovir among individuals in the United States, Thailand, and South Africa: HPTN067.
Tenofovir (TFV), a nucleotide reverse transcriptase inhibitor, requires two phosphorylation steps to form a competitive inhibitor of HIV reverse transcriptase. Adenylate kinase 2 (AK2) has been previously demonstrated to phosphorylate tenofovir to tenofovir-monophosphate, while creatine kinase, muscle (CKM), pyruvate kinase, muscle (PKM) and pyruvate kinase, liver and red blood cell (PKLR) each have been found to phosphorylate tenofovir-monophosphate to the pharmacologically active tenofovir-diphosphate. In the present study, genomic DNA isolated from dried blood spots collected from 505 participants from Bangkok, Thailand; Cape Town, South Africa; and New York City, USA were examined for variants in AK2, CKM, PKM, and PKLR using next-generation sequencing. The bioinformatics tools SIFT and PolyPhen predicted that 19 of the 505 individuals (3.7% frequency) carried variants in at least one kinase that would result in a decrease or loss of enzymatic activity. To functionally test these predictions, AK2 and AK2 variants were expressed in and purified from E. coli, followed by investigation of their activities towards tenofovir. Interestingly, we found that purified AK2 had the ability to phosphorylate tenofovir-monophosphate to tenofovir-diphosphate in addition to phosphorylating tenofovir to tenofovir-monophosphate. Further, four of the six AK2 variants predicted to result in a loss or decrease of enzyme function exhibited a ≥30% decrease in activity towards tenofovir in our in vitro assays. Of note, an AK2 K28R variant resulted in a 72% and 81% decrease in the formation of tenofovir-monophosphate and tenofovir-diphosphate, respectively. These data suggest that there are naturally occurring genetic variants that could potentially impact TFV activation
Previously unreported <i>CKM</i> missense variants detected in clinical trial participants located in Bangkok, Thailand, Cape Town, South Africa, and New York City, USA.
<p>Previously unreported <i>CKM</i> missense variants detected in clinical trial participants located in Bangkok, Thailand, Cape Town, South Africa, and New York City, USA.</p
Previously unreported <i>AK2</i> missense variants detected in clinical trial participants located in Bangkok, Thailand, Cape Town, South Africa, and New York City, USA.
<p>Previously unreported <i>AK2</i> missense variants detected in clinical trial participants located in Bangkok, Thailand, Cape Town, South Africa, and New York City, USA.</p
HPTN 067 participant enrollment location and gender information.
<p>HPTN 067 participant enrollment location and gender information.</p
Previously unreported <i>PKLR</i> missense variants detected in clinical trial participants located in Thailand, South Africa, and the USA.
<p>Previously unreported <i>PKLR</i> missense variants detected in clinical trial participants located in Thailand, South Africa, and the USA.</p
Distribution of individuals enrolled at the Bangkok, Cape Town, and New York City study sites carrying genetic variants in TFV-activating kinases.
<p>Each rectangle is representative of a TFV-activating kinase that was sequenced: <i>AK2</i> in blue, <i>CKM</i> in pink, <i>PKM</i> in orange and <i>PKLR</i> in green. Numerical values indicate the number of individuals detected to carry a single nucleotide variation or deletion. Overlapping regions of each rectangle indicate the number of individuals with genetic variants in more than one kinase.</p