A rapid spin through oil results in higher cell-associated concentrations of antiretrovirals compared with conventional cell washing

The Effect of Rifampicin on Darunavir, Ritonavir, and Dolutegravir Exposure within Peripheral Blood Mononuclear Cells: a Dose Escalation Study

Ritonavir-boosted darunavir (DRV/r) and dolutegravir (DTG) are affected by induction of metabolizing enzymes and efflux transporters caused by rifampicin (RIF). This complicates the treatment of people living with HIV (PLWH) diagnosed with tuberculosis. Recent data showed that doubling DRV/r dose did not compensate for this effect, and hepatic safety was unsatisfactory. We aimed to evaluate the pharmacokinetics of DRV, ritonavir (RTV), and DTG in the presence and absence of RIF in peripheral blood mononuclear cells (PBMCs). PLWH were enrolled in a dose-escalation crossover study with 6 treatment periods of 7 days. Participants started with DRV/r 800/100 mg once daily (QD), RIF and DTG were added before the RTV dose was doubled, and then they received DRV/r 800/100 twice daily (BD) and then 1,600/200 QD or vice versa. Finally, RIF was withdrawn. Plasma and intra-PBMC drug concentrations were measured through validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods. Seventeen participants were enrolled but only 4 completed all study phases due to high incidence of liver toxicity. Intra-PBMC DRV trough serum concentration (C_trough) after the addition of RIF dropped from a median (interquartile range [IQR]) starting value of 261 ng/mL (158 to 577) to 112 ng/mL (18 to 820) and 31 ng/mL (12 to 331) for 800/100 BD and 1,600/200 QD DRV/r doses, respectively. The DRV intra-PBMC/plasma ratio increased significantly (P = 0.003). DTG and RIF intra-PBMC concentrations were in accordance with previous reports in the absence of RIF or DRV/r. This study showed a differential impact of enzyme and/or transporter induction on DRV/r concentrations in plasma and PBMCs, highlighting the usefulness of studying intra-PBMC pharmacokinetics with drug-drug interactions. (This study has been registered at ClinicalTrials.gov under registration no. NCT03892161.)

Antiretroviral drug exposure in lymph nodes is heterogeneous and drug dependent

Introduction

HIV reservoirs and infected cells may persist in tissues with low concentrations of antiretrovirals (ARVs). Traditional pharmacology methods cannot assess variability in ARV concentrations within morphologically complex tissues, such as lymph nodes (LNs). We evaluated the distribution of six ARVs into LNs and the proximity of these ARVs to CD4⁺ T cells and cell‐associated RT‐SHIV viral RNA.

Methods

Between December 2014 and April 2017, RT‐SHIV infected (SHIV+; N = 6) and healthy (SHIV–; N = 6) male rhesus macaques received two selected four‐drug combinations of six ARVs over 10 days to attain steady‐state conditions. Serial cryosections of axillary LN were analysed by a multimodal imaging approach that combined mass spectrometry imaging (MSI) for ARV disposition, RNAscope in situ hybridization for viral RNA (vRNA) and immunohistochemistry for CD4⁺ T cell and collagen expression. Spatial relationships across these four imaging domains were investigated by nearest neighbour search on co‐registered images using MATLAB.

Results

Through MSI, ARV‐dependent, heterogeneous concentrations were observed in different morphological LN regions, such as the follicles and medullary sinuses. After 5–6 weeks of infection, more limited ARV penetration into LN tissue relative to the blood marker heme was found in SHIV+ animals (SHIV+: 0.7 [0.2–1.4] mm; SHIV–: 1.3 [0.5–1.7] mm), suggesting alterations in the microcirculation. However, we found no detectable increase in collagen deposition. Regimen‐wide maps of composite ARV distribution indicated that up to 27% of SHIV+ LN tissue area was not exposed to detectable ARVs. Regions associated with B cell follicles had median 1.15 [0.94–2.69] ‐fold reduction in areas with measurable drug, though differences were only statistically significant for tenofovir (p = 0.03). Median co‐localization of drug with CD4⁺ target cells and vRNA varied widely by ARV (5.1–100%), but nearest neighbour analysis indicated that up to 10% of target cells and cell‐associated vRNA were not directly contiguous to at least one drug at concentrations greater than the IC50 value.

Conclusions

Our investigation of the spatial distributions of drug, virus and target cells underscores the influence of location and microenvironment within LN, where a small population of T cells may remain vulnerable to infection and low‐level viral replication during suppressive ART.

The Lymph Node Reservoir: Physiology, HIV Infection, and Antiretroviral Therapy

Despite advances in treatment, finding a cure for HIV remains a top priority. Chronic HIV infection is associated with increased risk of comorbidities, such as diabetes and cardiovascular disease. Additionally, people living with HIV must remain adherent to daily antiretroviral therapy, because lapses in medication adherence can lead to viral rebound and disease progression. Viral recrudescence occurs from cellular reservoirs in lymphoid tissues. In particular, lymph nodes are central to the pathology of HIV due to their unique architecture and compartmentalization of immune cells. Understanding how antiretrovirals (ARVs) penetrate lymph nodes may explain why these tissues are maintained as HIV reservoirs, and how they contribute to viral rebound upon treatment interruption. In this report, we review (i) the physiology of the lymph nodes and their function as part of the immune and lymphatic systems, (ii) the pathogenesis and outcomes of HIV infection in lymph nodes, and (iii) ARV concentrations and distribution in lymph nodes, and the relationship between ARVs and HIV in this important reservoir.

Distribution of fluoroquinolones in the two aqueous compartments of Escherichia coli

The double-layered cell envelope of Gram-negative bacteria and active drug efflux present a formidable barrier for antimicrobial compounds to penetrate. Fluoroquinolones are among the few classes of antimicrobials that are clinically useful in the treatment of Gram-negative bacterial infection. Previous studies on fluoroquinolone accumulation measured total bacteria associated compounds, rather than the cytoplasmic accumulation. Fluoroquinolones target the type II topoisomerases in the cytoplasm. Thus, the cytoplasmic accumulation is expected to be more relevant to the potency of the drugs. Here, we fractionated and measured the concentration of nine fluoroquinolone compounds in the periplasm and the cytoplasm of two strains of E. coli cells, a parent strain and its isogenic efflux-deficient tolC knockout strain. The potency of the drugs was determined using the minimum inhibitory concentration (MIC) assay. We found that all fluoroquinolones tested accumulated at much higher concentrations in the periplasm than in the cytoplasm. The periplasmic concentrations were 2–15 folds higher than the cytoplasmic concentration, while the actual distribution ratio varies drastically among the compounds tested. Good correlation between the MIC and the cytoplasmic accumulation, but not whole cell accumulation, was observed using a pair of isogenic wild type and drug-efflux deficient strains.

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Fluoroquinolones accumulate to high concentration in the periplasm of E. coli

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Periplasmic concentrations are higher than the cytoplasmic and exterior media concentration.

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Good correlation was observed for the cytoplasmic drug concentration and the antimicrobial potency.

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Disruption of active efflux has a larger impact on the periplasmic than the cytoplasmic accumulation.

Antiretroviral Therapy Concentrations Differ in Gut vs. Lymph Node Tissues and Are Associated With HIV Viral Transcription by a Novel RT-ddPCR Assay

BACKGROUND

Most HIV-infected cells during antiretroviral therapy (ART) persist in lymphoid tissues. Studies disagree on whether suboptimal tissue ART concentrations contribute to ongoing HIV replication during viral suppression.

METHODS

We performed a cross-sectional study in virally-suppressed HIV+ participants measuring lymphoid tissue ART [darunavir (DRV), atazanavir (ATV), and raltegravir (RAL)] concentrations by LC-MS/MS assay. Tissue and plasma ART concentrations were used to estimate TPRs and drug-specific tissue:inhibitory concentration ratios (TICs). HIV DNA and sequentially produced HIV RNA transcripts were quantified from rectal biopsies using droplet digital PCR (ddPCR) assays.

RESULTS

Tissue samples were collected in duplicate from 19 participants: 38 rectal, 8 ileal (4 RAL, 2 DRV, 2 ATV), and 6 lymph node (4 RAL, 2 DRV) samples. Overall, median TICs were higher for RAL than DRV or ATV (both P = 0.006). Median TICs were lower in lymph nodes vs. ileum (0.49 vs. 143, P = 0.028) or rectum (33, P = 0.019), and all ART levels were below target concentrations. Higher rectal TICs were associated with lower HIV RNA transcripts (read-through, long LTR, and Nef, P all < 0.026) and a lower long LTR RNA/long LTR DNA ratio (P = 0.021).

CONCLUSIONS

We observed higher tissue ART concentrations in ileum and rectum compared with lymph nodes. We observed higher HIV transcription in participants with lower rectal ART concentrations. These findings add to the limited data supporting the idea that viral transcription may be influenced by ART concentrations in lymphoid tissues. Further exploration of tissue pharmacokinetics is needed in future HIV eradication strategies.

Direct and indirect quantification of phosphate metabolites of nucleoside analogs in biological samples

Nucleoside reverse transcriptase inhibitors (NRTIs) are prodrugs that require intracellular phosphorylation to active triphosphate nucleotide metabolites (NMs) for their pharmacological activity. However, monitoring these pharmacologically active NMs is challenging due to their instability, high hydrophilicity, and their low concentrations in blood and tissues. Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) is the gold standard technique for the quantification of NRTIs and their phosphorylated NMs. In this review, an overview of the publications describing the quantitative analysis of intracellular and total tissue concentration of NMs is presented. The focus of this review is the comparison of the different approaches and challenges associated with sample collection, tissue homogenization, cell lysis, cell counting, analyte extraction, sample storage conditions, and LC-MS analysis. Quantification methods of NMs via LC-MS can be categorized into direct and indirect methods. In the direct LC-MS methods, chromatographic retention of the NMs is accomplished by ion-exchange (IEX), ion-pairing (IP), hydrophilic interaction (HILIC), porous graphitic carbon (PGC) chromatography, or capillary electrophoresis (CE). In indirect methods, parent nucleosides are 1st generated from the dephosphorylation of NMs during sample preparation and are then quantified by reverse phase LC-MS as surrogates for their corresponding NMs. Both approaches have advantages and disadvantages associated with them, which are discussed in this review.

Heterogeneous antiretroviral drug distribution and HIV/SHIV detection in the gut of three species

HIV replication within tissues may increase in response to a reduced exposure to antiretroviral drugs. Traditional approaches to measuring drug concentrations in tissues are unable to characterize a heterogeneous drug distribution. Here, we used mass spectrometry imaging (MSI) to visualize the distribution of six HIV antiretroviral drugs in gut tissue sections from three species (two strains of humanized mice, macaques, and humans). We measured drug concentrations in proximity to CD3+ T cells that are targeted by HIV, as well as expression of HIV or SHIV RNA and expression of the MDR1 drug efflux transporter in gut tissue from HIV-infected humanized mice, SHIV-infected macaques, and HIV-infected humans treated with combination antiretroviral drug therapy. Serial 10-μm sections of snap-frozen ileal and rectal tissue were analyzed by MSI for CD3+ T cells and MDR1 efflux transporter expression by immunofluorescence and immunohistochemistry, respectively. The tissue slices were analyzed for HIV/SHIV RNA expression by in situ hybridization and for antiretroviral drug concentrations by liquid chromatography-mass spectrometry. The gastrointestinal tissue distribution of the six drugs was heterogeneous. Fifty percent to 60% of CD3+ T cells did not colocalize with detectable drug concentrations in the gut tissue. In all three species, up to 90% of HIV/SHIV RNA was found to be expressed in gut tissue with no exposure to drug. These data suggest that there may be gut regions with little to no exposure to antiretroviral drugs, which may result in low-level HIV replication contributing to HIV persistence.

Advances and challenges in bacterial compound accumulation assays for drug discovery

The identification of potent in vitro inhibitors of essential bacterial targets is relatively straightforward, however vanishingly few of these molecules have Gram-negative antibacterial potency and spectrum because of a failure to accumulate inside the bacteria. The Gram-negative bacterial cell envelope provides a formidable barrier to entry and couples with efflux pumps to prevent compound accumulation. Assays to measure the cellular permeation, efflux and accumulation of compounds in bacteria continue to be innovated and refined to guide drug discovery. Important advances in the label-free detection of compounds associated with or passing through bacteria rely on mass spectrometry This technique holds the promise of bacterial subcellular resolution and the throughput needed to test libraries of compounds to evaluate structure-accumulation relationships.

Plasma and intracellular pharmacokinetics of tenofovir in patients switched from tenofovir disoproxil fumarate to tenofovir alafenamide

OBJECTIVES

The aim of the study was to compare the intraindividual plasma and intracellular peripheral blood mononuclear cell (PBMC) pharmacokinetics of tenofovir (TFV) and its intracellular metabolite, TFV-diphosphate (TFV-DP) in patients switched from a fixed-dose combination (FDC) tablet of TFV disoproxil fumarate (TDF)/emtricitabine (FTC)/elvitegravir (EVG)/cobicistat (COBI) to a FDC containing TFV alafenamide (TAF)/FTC/EVG/COBI.

DESIGN

A single-arm, prospective, nonrandomized, cross-over, pharmacokinetic study in patients receiving a TDF-containing regimen (TDF 300 mg/FTC 200 mg/EVG 150 mg/COBI 150 mg) switched to a TAF-containing FDC regimen (TAF 10 mg/FTC 200 mg/EVG 150 mg/COBI 150 mg).

METHODS

Single, sparse plasma and PBMC samples were collected during TDF therapy and 4-8 weeks post-switch to the TAF-containing regimen. Plasma TFV and cell associated TFV-DP concentrations were determined with validated liquid chromatography tandem mass spectrometry methods. PBMC cell enumeration was performed by quantification of RNaseP (RPP30) gene copy numbers using a highly sensitive droplet digital PCR assay. Plasma and PBMC pharmacokinetics were summarized as geometric mean and compared as a geometric mean ratio with a Wilcoxon signed-rank test.

RESULTS

In 30 participants with evaluable data, TFV plasma concentrations decreased 90% [TDF: 99.98 (2.24) ng/ml vs. TAF: 10.2 (1.6) ng/ml, P < 0.001] after the switch while cell-associated TFV-DP increased 2.41-fold [TAF: 834.7 (2.49) vs. TDF: 346.85 (3.75) fmol/10 cells, P = 0.004].

CONCLUSION

Intraindividually, plasma TFV concentrations significantly decreased while cell associated TFV-DP concentrations significantly increased after switching from a TDF to a TAF-containing antiretroviral therapy regimen.

Tissue Pharmacologic and Virologic Determinants of Duodenal and Rectal Gastrointestinal-Associated Lymphoid Tissue Immune Reconstitution in HIV-Infected Patients Initiating Antiretroviral Therapy

Plasma, duodenal, and rectal tissue antiretroviral therapy (ART) drug concentrations, human immunodeficiency virus (HIV) RNA and HIV DNA copy numbers, and recovery of mucosal immunity were measured before and 9 months after initiation of 3 different ART regimens in 26 subjects. Plasma and tissue HIV RNA correlated at baseline and when 9-month declines were compared, suggesting that these compartments are tightly associated. Antiretroviral tissue:blood penetration ratios were above the 50% inhibitory concentration values in almost 100% of cases. There were no correlations between drug concentrations and HIV DNA/RNA. Importantly, no evidence was found for residual viral replication or deficient tissue drug penetration to account for delayed gastrointestinal-associated lymphoid tissue immune recovery.

HIV Persistence in Gut-Associated Lymphoid Tissues: Pharmacological Challenges and Opportunities

An increasing amount of evidence suggests that HIV replication persists in gut-associated lymphoid tissues (GALT), despite treatment with combination antiretroviral therapy (cART). Residual replication in this compartment may propagate infection at other sites in the body and contribute to sustained immune dysregulation and delayed immune recovery. Therefore, it is important to focus efforts on eliminating residual replication at this site. There are several challenges to accomplishing this goal, including low antiretroviral (ARV) exposure at specific tissue locations within GALT, which might be overcome by using the tools of clinical pharmacology. Here, we summarize the evidence for GALT as a site of residual HIV replication, highlight the consequences of persistent infection in tissues, identify current pharmacologic knowledge of drug exposure in GALT, define the challenges that hinder eradication from this site, and propose several avenues for pharmacologic intervention.