With adequate adherence, HIV preexposure prophylaxis (PrEP) with emtricitabine (FTC)/tenofovir (TFV) disoproxil fumarate (TDF) substantially reduces the risk of HIV acquisition . Acquisition of drug-resistant virus despite high adherence, however, has been reported in two prior case reports [2,3]. Determining whether resistance is primary (transmitted) or acquired under selective pressure from incompletely suppressive antiretroviral therapy is challenging. Here, we describe a case of HIV infection despite oral PrEP complicated by inappropriate prescribing and follow-up. We also present an innovative procedure utilizing segmental analysis of a hair sample to determine past adherence to oral FTC/TDF over time. This procedure may help elucidate the mechanism of PrEP failure in future cases.
A 34-year-old, white cisgender MSM started daily FTC/TDF in February 2016 after a nonreactive automated HIV antigen/antibody combination test in December 2015; he reported no interim sexual activity. He reported being fully adherent to FTC/TDF from February to May 2016, but self-discontinued from May to July 2016 because of perceived lack of risk. He restarted FTC/TDF without undergoing repeated HIV testing in July 2016. Pharmacy dispensing records support this patient-reported timeline of PrEP initiation and adherence.
At his first PrEP visit in February 2016, he was prescribed 30 days of FTC/TDF with 11 refills by an infectious diseases specialist and told to return in 1 month and then 6 months for HIV and renal function tests; no visits occurred. In March 2017, after being on PrEP for the last 8 months with good adherence per self-report, he developed fevers, chills, and myalgias. He sought care at an urgent care center, where a rapid influenza test was performed and was negative, although no HIV testing was performed. In April 2017, he presented for evaluation of anal condylomata, at which visit an automated HIV antigen/antibody test was sent and was reactive (day 0). On day 2, his HIV-1 RNA was 27 316 copies/ml, and genotyping (by population sequencing) subsequently revealed significant mutations in the reverse transcriptase gene, including M184V [which reduces susceptibility to lamivudine (3TC)/ emtricitabine (FTC)], K65R (which reduces susceptibility to TDF), K70T (which reduces susceptibility to TDF and FTC/3TC), and the K103N mutation (which reduces susceptibility to efavirenz and nevirapine). The reverse transcriptase gene also harbored two polymorphisms (V90I and V179I), and there were no mutations in the protease-encoding gene. Given his infection with a multidrug-resistant (MDR) virus, the patient was started on dolutegravir, rilpivirine, and darunavir/cobicistat, beginning on day 13. Plasma HIV-1 RNA decreased to less than 20 copies/ml by day 66, at which point his regimen was simplified to rilpivirine and dolutegravir.
Subsequent evaluations focused on assessing his FTC/TDF adherence prior to diagnosis. Liquid-chromatography–tandem-mass-spectrometric (LC–MS/MS) analysis of plasma collected on day 2 revealed TFV and FTC levels of 75 and 281 ng/ml, respectively, consistent with recent dosing. To further evaluate adherence over time, a hair sample was collected at day 27 and segmental analysis of TFV and FTC levels by LC–MS/MS was performed in segments of 1 cm each from the scalp. Hair levels were commensurate with consistently high PrEP adherence over the 3 months prior to the HIV diagnosis (Fig. 1). As of April 2018, he continues to do well on antiretroviral therapy with HIV-1 RNA loads persistently less than 20 copies/ml. In terms of sexual activity, he confirmed two male sexual partners since going on PrEP: one who was his primary relationship and reportedly HIV-uninfected and a second partner of unknown HIV status. No contact tracing could be performed on either sexual partner.
Acquisition of MDR HIV in patients with excellent adherence to oral FTC/TDF is rare. In our case, multiple factors contributed to a negative outcome: a 2-month gap between initial HIV testing and FTC/TDF initiation, provision of 11 months of medication refills at the initial visit without verifying return visits, and the patient's failure to obtain HIV testing prior to reinitiating FTC/TDF in July 2016. Although the procedure described here, in which drug levels are quantified in plasma and segmental hair samples, is useful in establishing PrEP compliance over an extended time period, it cannot determine precisely when HIV infection occurred.
The presence of three nucleoside reverse transcriptase inhibitor (NRTI)-conferring mutations and a nonnucleoside reverse transcriptase inhibitor (NNRTI)-conferring mutation upon FTC/TDF failure makes the acquisition of an MDR virus the most likely scenario. The flu-like symptoms in March 2017 (∼1 month prior to confirming an HIV diagnosis) were consistent with an acute seroconversion syndrome. In this setting, the plasma and segmental hair analysis data suggest that the patient was highly adherent to PrEP for 3 months prior to this flu-like syndrome (and likely date of MDR virus acquisition). There is a more remote possibility that the patient was infected with HIV prior to the period represented by the adherence metrics obtained via segmental hair analysis. In that case, if the patient was not fully adherent to PrEP when exposed to HIV in the past, the patient could have developed the NRTI-resistant mutations (M184V, K70T, and K65R) through the selective pressure of FTC/TDF prophylaxis after acquiring a virus carrying the K103N mutation. The NRTI-resistance mutations, with their negative impact on viral fitness, are less commonly transmitted than the K103N mutation . Of note, additional plasma was not available around the time of likely seroconversion for next-generation sequencing to determine if minority quasispecies associated with resistance were also present.
The US Public Health Service guidelines recommend HIV testing within a week of starting PrEP, as well as follow-up every 3 months for laboratory evaluation including HIV testing. Such recommendations, if followed in this case, would have allowed for more rapid initiation of antiretroviral therapy for individual-level benefit and a more expedient response to the public health hazard associated with MDR HIV infection and viremia in a patient with multiple sexual partners. This case serves as a reminder of best practices on administering PrEP. Moreover, although hair analysis of PrEP drugs has been examined as a metric of adherence in prior settings, this report describes for the first time the use of segmental hair analysis to examine adherence patterns to PrEP over time. Hair grows remarkably consistently in the occipital region of the scalp at a rate of approximately 1 cm per month . Segmental hair analysis provides information on drug exposure over time, suggesting a protocol for measuring PrEP adherence over past months in future cases of seroconversions on PrEP.
M.G. and H.O., as well as the hair testing, was funded through the US National Institutes of Health (NIAID/NIH 2RO1AI098472). J.J.T., C.B.H., and M.S.M. had no funding source for this study. The funding source had no role in study design, data collection, data analysis, data interpretation, article preparation, or in the decision to submit the article for publication.
Author contributions: J.T.T. collected data, conceptualized and designed the analysis plan, analyzed data, drafted the initial article, and reviewed and revised the article. M.G. conceptualized and designed the study, collected data, analyzed data, and reviewed and revised the article. C.B.H. analyzed data and reviewed and revised the article. M.S.M. conceptualized and designed the analysis plan, reviewed and revised the article, and supervised all aspects of this project.
Conflicts of interest
All authors have no conflicts of interest to declare. Written informed consent to publish in all formats was obtained from the patient described in this study.
Previously presented in abstract form at the 25th Annual Conference on Retroviruses and Opportunistic Infections (CROI): Thaden JT, Gandhi M, Kuncze K, et al. Seroconversion on PrEP: A Protocol for Untangling Adherence vs. Resistance Failure. CROI Abstract 1041, March 4–8, 2018. Boston, MA.
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