OA26.06 LB
Background: Successful pre-exposure prophylaxis requires antiretroviral (ARV) adherence. Therapeutic drug monitoring provides accurate, but short term adherence data. Hair strand (HS) analysis with traditional LC/MS provides long term adherence information, but fails to discriminate ARV presence at the time of HIV exposure. Mass spectrometry imaging (MSI) offers the ability to visualize ARV exposure in tissues, allowing for identification of distinct distribution patterns. Here, as proof of concept, we use MSI to visualize tenofovir (TFV), emtricitabine (FTC), and efavirenz (EFV) in HS from HIV positive subjects.
Methods: HS (20–30) were taken from 5 HIV positive, virologically suppressed subjects receiving Atripla® for >1 year. HS incubated in TFV, FTC, and EFV for 24 hours or HS never exposed to ARVs served as positive and negative controls, respectively. After collection, HS were analyzed using an infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) source coupled to a Thermo Q-Exactive mass spectrometer. Signal intensity between HS from a single subject was compared to assess intra-subject variability. MSI data were analyzed using MSiReader software.
Results: MSI experiments demonstrate continuous EFV signal along HS for all 5 subjects. MS/MS analysis and the use of a negative control confirmed EFV specificity. Variability in signal intensity was similar within (∼ 2.5 fold) and between (∼ 4 fold) subjects. TFV and FTC were not visualized in HS from dosed subjects, though FTC and EFV were both detected in the positive control sample.
Conclusions: EFV distribution in HS demonstrates consistent ARV exposure in these subjects, and is in agreement with their suppressed viral loads. Confirmation of EFV signal with MS/MS and low intra-subject variability showcase the accuracy and precision of this method. We show for the first time that MSI of HS is a promising approach for measuring ARV adherence. Future studies will examine ARV hair distribution patterns in non-suppressed patients.
