Francesca T. Aweeka

Tryptophan Catabolism by Indoleamine 2,3-Dioxygenase 1 Alters the Balance of TH17 to Regulatory T Cells in HIV Disease

Patients with AIDS have fewer immune cells to defend against microbial invasion through the gut, a critical loss that may be caused by a tryptophan metabolite produced by other immune cells. Loss of the Defenders at the Gate Like archers stationed along the walls of a medieval castle, the immune system patrols the vulnerable parts of our body to keep pathogens at bay. One of these susceptible areas is the mucosa of the gastrointestinal tract, which is continually exposed to ingested and resident pathogens. This defense breaks down in patients with AIDS, in which sentinel immune cells [T helper 17 (TH17) cells] are missing from the gastrointestinal lining, potentially accounting for some secondary infections acquired by these patients. Favre and colleagues present evidence that the loss of these cells (and a parallel increase in immune suppressor cells) is caused by a metabolite of the amino acid tryptophan, new understanding that should help to prevent this serious consequence of HIV infection. HIV disease is in part an inflammatory disease, and activated T cells and cytokines circulate in patients’ blood, along with pathogen-derived molecules that trigger the innate immune system. The authors show that, in patients with serious AIDS, who are in this inflammatory state, the enzyme indoleamine 2,3-dioxygenase 1 (IDO1), which catabolizes tryptophan, is elevated in dendritic cells (DCs)—agents that present antigen to the immune system—from the blood, lymph nodes, and mucosa of the lower gastrointestinal tract. The inflammation-related molecules interferon γ and bacterial lipopolysaccharide can induce IDO1 in isolated DCs. This excess IDO1 activation increased blood concentrations of tryptophan catabolites in patients, and two of the catabolites increased the proportion of TH17 (activating) immune cells and decreased the proportion of T regulatory (Treg) (suppressing) immune cells in culture. In patients with serious disease, the authors found that the ratio of TH17 to Treg cells was much lower than normal, which hampers the ability of the body to raise an effective immune defense against pathogens. This dysfunctional system would set up a reinforcing loop that progressively depletes vulnerable tissues of their immune protection. Paradoxically, it seems, activation of the immune system by HIV may be contributing to the decline in immune function that is the hallmark of the disease. IDO1 inhibitors are being tested for their efficacy in interfering with this dangerous depletion of defenses. The pathogenesis of human and simian immunodeficiency viruses is characterized by CD4+ T cell depletion and chronic T cell activation, leading ultimately to AIDS. CD4+ T helper (TH) cells provide protective immunity and immune regulation through different immune cell functional subsets, including TH1, TH2, T regulatory (Treg), and interleukin-17 (IL-17)–secreting TH17 cells. Because IL-17 can enhance host defenses against microbial agents, thus maintaining the integrity of the mucosal barrier, loss of TH17 cells may foster microbial translocation and sustained inflammation. Here, we study HIV-seropositive subjects and find that progressive disease is associated with the loss of TH17 cells and a reciprocal increase in the fraction of the immunosuppressive Treg cells both in peripheral blood and in rectosigmoid biopsies. The loss of TH17/Treg balance is associated with induction of indoleamine 2,3-dioxygenase 1 (IDO1) by myeloid antigen-presenting dendritic cells and with increased plasma concentration of microbial products. In vitro, the loss of TH17/Treg balance is mediated directly by the proximal tryptophan catabolite from IDO metabolism, 3-hydroxyanthranilic acid. We postulate that induction of IDO may represent a critical initiating event that results in inversion of the TH17/Treg balance and in the consequent maintenance of a chronic inflammatory state in progressive HIV disease.

Pharmacokinetic interactions between protease inhibitors and statins in HIV seronegative volunteers: ACTG Study A5047.

Objective Lipid lowering therapy is used increasingly in persons with HIV infection in the absence of safety data or information on drug interactions with antiretroviral agents. The primary objectives of this study were to examine the effects of ritonavir (RTV) plus saquinavir soft-gel (SQVsgc) capsules on the pharmacokinetics of pravastatin, simvastatin, and atorvastatin, and the effect of pravastatin on the pharmacokinetics of nelfinavir (NFV) in order to determine clinically important drug–drug interactions. Design Randomized, open-label study in healthy, HIV seronegative adults at AIDS Clinical Trials Units across the USA. Methods Three groups of subjects (arms 1, 2, and 3) received pravastatin, simvastatin or atorvastatin (40 mg daily each) from days 1–4 and 15–18. In these groups, RTV 400 mg and SQVsgc 400 mg twice daily were given from days 4–18. A fourth group (arm 4) received NFV 1250 mg twice daily from days 1–14 with pravastatin 40 mg daily added from days 15–18. Statin and NFV levels were measured by liquid chromatography/tandem mass spectrometry. Results Fifty-six subjects completed both pharmacokinetic study days. In arms 1–3, the median estimated area under the curves (AUC)0−−24 for the statins were: pravastatin (arm 1, n = 13), 151 and 75 nguu.h/ml on days 4 and 18 (decline of 50% in presence of RTV/SQVsgc), respectively (P = 0.005); simvastatin (arm 2, n = 14), 17 and 548 nguu.h/ml on days 4 and 18 (increase of 3059% in the presence of RTV/SQVsgc), respectively (P < 0.001); and total active atorvastatin (arm 3, n = 14), 167 and 289 nguu.h/ml on days 4 and 18 (increase of 79% in the presence of RTV/SQVsgc), respectively (P < 0.001). In arm 4, the median estimated AUC0−−8 for NFV (24 319 versus 26 760 nguu.h/ml;P = 0.58) and its active M8 metabolite (15 565 versus 14 571 nguu.h/m;P = 0.63) were not statistically different from day 14 to day 18 (without or with pravastatin). Conclusions Simvastatin should be avoided and atorvastatin may be used with caution in persons taking RTV and SQVsgc. Dose adjustment of pravastatin may be necessary with concomitant use of RTV and SQVsgc. Pravastatin does not alter the NFV pharmacokinetics, and thus appears to be safe for concomitant use.

Indinavir acutely inhibits insulin-stimulated glucose disposal in humans: a randomized, placebo-controlled study.

Background Therapy with HIV protease inhibitors (PI) causes insulin resistance even in the absence of HIV infection, hyperlipidemia or changes in body composition. The mechanism of the effects on insulin action is unknown. In vitro studies suggest that PI selectively and rapidly inhibit the activity of the insulin-responsive glucose transporter GLUT-4. We hypothesized that a single dose of the PI indinavir resulting in therapeutic plasma concentrations would acutely decrease insulin-stimulated glucose disposal in healthy human volunteers. Methods Randomized, double-blind, cross-over study comparing the effect of 1200 mg of orally administered indinavir and placebo on insulin-stimulated glucose disposal during a 180-min euglycemic, hyperinsulinemic clamp. Six healthy HIV-seronegative adult male volunteers were studied twice with 7 to 10 days between studies. Results There were no significant differences in baseline fasting body weight, or plasma glucose, insulin, lipid and lipoprotein levels between placebo- and indinavir-treated subjects. During steady-state (t60−−180 min) insulin reached comparable levels (394 ± 13 versus 390 ± 11 pmol/l) and glucose was clamped at approximately 4.4 mmol/l under both conditions. The average maximum concentration of indinavir was 9.4 ± 2.2 μM and the 2-h area under the curve was 13.5 ± 3.1 μM⋅h. Insulin-stimulated glucose disposal per unit of insulin (M/I) decreased in all subjects from 14.1 ± 1.2 to 9.2 ± 0.8 mg/kg⋅min per μ UI/ml (95% confidence interval for change, 3.7–6.1;P < 0.001) on indinavir (average decrease, 34.1 ± 9.2%). The non-oxidative component of total glucose disposal (storage) decreased from 3.9 ± 1.8 to 1.9 ± 0.9 mg/kg⋅min (P < 0.01). Free fatty acid levels were not significantly different at baseline and were suppressed equally with insulin administration during both studies. Conclusions A single dose of indinavir acutely decreases total and non-oxidative insulin-stimulated glucose disposal during a euglycemic, hyperinsulinemic clamp. Our data are compatible with the hypothesis that an acute effect of indinavir on glucose disposal in humans is mediated by a direct blockade of GLUT-4 transporters.

Artemether-lumefantrine treatment of uncomplicated Plasmodium falciparum malaria: a systematic review and meta-analysis of day 7 lumefantrine concentrations and therapeutic response using individual patient data

Achieving adequate antimalarial drug exposure is essential for curing malaria. Day 7 blood or plasma lumefantrine concentrations provide a simple measure of drug exposure that correlates well with artemether-lumefantrine efficacy. However, the ‘therapeutic’ day 7 lumefantrine concentration threshold needs to be defined better, particularly for important patient and parasite sub-populations. The WorldWide Antimalarial Resistance Network (WWARN) conducted a large pooled analysis of individual pharmacokinetic-pharmacodynamic data from patients treated with artemether-lumefantrine for uncomplicated Plasmodium falciparum malaria, to define therapeutic day 7 lumefantrine concentrations and identify patient factors that substantially alter these concentrations. A systematic review of PubMed, Embase, Google Scholar, ClinicalTrials.gov and conference proceedings identified all relevant studies. Risk of bias in individual studies was evaluated based on study design, methodology and missing data. Of 31 studies identified through a systematic review, 26 studies were shared with WWARN and 21 studies with 2,787 patients were included. Recrudescence was associated with low day 7 lumefantrine concentrations (HR 1.59 (95 % CI 1.36 to 1.85) per halving of day 7 concentrations) and high baseline parasitemia (HR 1.87 (95 % CI 1.22 to 2.87) per 10-fold increase). Adjusted for mg/kg dose, day 7 concentrations were lowest in very young children (<3 years), among whom underweight-for-age children had 23 % (95 % CI −1 to 41 %) lower concentrations than adequately nourished children of the same age and 53 % (95 % CI 37 to 65 %) lower concentrations than adults. Day 7 lumefantrine concentrations were 44 % (95 % CI 38 to 49 %) lower following unsupervised treatment. The highest risk of recrudescence was observed in areas of emerging artemisinin resistance and very low transmission intensity. For all other populations studied, day 7 concentrations ≥200 ng/ml were associated with >98 % cure rates (if parasitemia <135,000/μL). Current artemether-lumefantrine dosing recommendations achieve day 7 lumefantrine concentrations ≥200 ng/ml and high cure rates in most uncomplicated malaria patients. Three groups are at increased risk of treatment failure: very young children (particularly those underweight-for-age); patients with high parasitemias; and patients in very low transmission intensity areas with emerging parasite resistance. In these groups, adherence and treatment response should be monitored closely. Higher, more frequent, or prolonged dosage regimens should now be evaluated in very young children, particularly if malnourished, and in patients with hyperparasitemia.

The metabolic effects of lopinavir/ritonavir in HIV-negative men.

Background: Therapy with HIV protease inhibitors (PI) has been shown to worsen glucose and lipid metabolism, but whether these changes are caused by direct drug effects, changes in disease status, or body composition is unclear. Therefore, we tested the effects of the PI combination lopinavir and ritonavir on glucose and lipid metabolism in HIV-negative subjects. Methods: A dose of 400 mg lopinavir/100 mg ritonavir was given twice a day to 10 HIV-negative men. Fasting glucose and insulin, lipid and lipoprotein profiles, oral glucose tolerance, insulin sensitivity by euglycemic hyperinsulinemic clamp, and body composition were determined before and after lopinavir/ritonavir treatment for 4 weeks. Results: On lopinavir/ritonavir, there was an increase in fasting triglyceride (0.89 ± 0.15 versus 1.63 ± 0.36 mmol/l; P = 0.007), free fatty acid (FFA; 0.33 ± 0.04 versus 0.43 ± 0.06 mmol/l; P = 0.001), and VLDL cholesterol (15.1 ± 2.6 versus 20 ± 3.3 mg/dl; P = 0.05) levels. There were no changes in fasting LDL, HDL, IDL, lipoprotein (a), or total cholesterol levels. Fasting glucose, insulin, and insulin-mediated glucose disposal were unchanged, but on a 2 h oral glucose tolerance test glucose and insulin increased. There were no changes in weight, body fat, or abdominal adipose tissue by computed tomography. Conclusion: Treatment with 4 weeks of lopinavir/ritonavir in HIV-negative men causes an increase in triglyceride levels, VLDL cholesterol, and FFA levels. Lopinavir/ritonavir leads to a deterioration in glucose tolerance at 2 h, but there is no significant change in insulin-mediated glucose disposal rate by euglycemic hyperinsulinemic clamp.

Interruption of treatment with individual therapeutic drug classes in adults with multidrug-resistant HIV-1 infection.

BACKGROUND Many antiretroviral-treated human immunodeficiency virus (HIV)-infected patients experience sustained immunologic and virologic benefit despite the presence of multidrug-resistant HIV. We hypothesized that the use of simplified regimens could maintain treatment benefit while preventing viral evolution and reducing drug-related toxicity and costs. METHODS We conducted a 48-week nonrandomized study of adults with multidrug-resistant HIV type 1 infection. Subjects interrupted protease inhibitor (PI) (n=18), reverse-transcriptase inhibitor (RTI) (n=6), or nonnucleoside RTI (NNRTI) (n=6) treatment. RESULTS At study entry, subjects had a median reduction in HIV RNA levels of 1.2 log10 copies/mL relative to pretreatment levels. Interruption of PI treatment was associated with stable HIV RNA levels (mean change per week, +0.005 log10 copies/mL; P=.36). PI mutations waned and replicative capacity and HIV RNA levels increased after long-term observation. HIV RNA levels also remained stable in subjects interrupting NNRTI treatment. In contrast, all subjects who interrupted RTI treatment exhibited immediate increases in HIV RNA levels, and most exhibited a subsequent loss of the M184V mutation. CONCLUSIONS These data indicate that nucleoside analogues often exert continued antiviral activity in the setting of drug-resistance mutations and that both nucleoside analogues and PIs can select for drug-resistance mutations that reduce viral fitness. These observations support the evaluation of treatment strategies aimed at maintaining the treatment benefit of therapy while reducing drug exposure.

Time course of cerebrospinal fluid responses to antiretroviral therapy : evidence for variable compartmentalization of infection

OBJECTIVES To compare the kinetics and magnitude of HIV-1 RNA responses to antiretroviral therapy (ART) in the cerebrospinal fluid (CSF) and plasma. DESIGN Repeated lumbar punctures (LPs) were performed after the initiation or change in ART in 15 HIV-1-infected subjects, with the focus on two phases of response: an acute phase within the first 11 days, for which crude estimates of viral RNA half-lives and decay rates were derived and CSF:plasma relative decay ratios quantitatively analysed; and a longer-term phase beyond 4 weeks that was descriptively assessed. RESULTS In 13 subjects studied during the acute phase, the crude HIV-1 RNA half-life was longer (median 2.0 compared with 1.9 days), the decay rate slower (median 0.13 compared with 0.16 log10 copies/day) and, most notably, the variability greater (intraquartile range of half-life 1.8-4.3 compared with 1.7-2.1 days) in the CSF than in the plasma. A slower decay in the CSF correlated with lower initial blood CD4 T lymphocyte counts (P = 0.001). Seven of 11 subjects studied at 4 weeks or later, including some with slower acute-phase CSF responses, showed greater or more durable viral suppression in the CSF. CONCLUSION Divergent acute-phase viral kinetics in the CSF and plasma, and proportionally greater long-term decrements in CSF HIV-1 RNA in slow early-responders or poor overall plasma responders indicate variable compartmentalization of CSF infection, consistent with a model of two prototypes of CSF infection: short-lived, transitory infection that predominates in early HIV-1 infection and longer-lived, more autonomous CSF infection predominating in late HIV-1 infection. Additional studies will be needed to define more precisely the acute and longer-term CSF kinetics in different clinical settings and to assess this model.

Efficacy and Tolerability of 3 Nonnucleoside Reverse Transcriptase Inhibitor–Sparing Antiretroviral Regimens for Treatment-Naive Volunteers Infected With HIV-1: A Randomized, Controlled Equivalence Trial

Background Non-nucleoside reverse transcriptase (NNRTI) inhibitor-based antiretroviral therapy is not suitable for all treatment-naive HIV-infected persons.BACKGROUND Nonnucleoside reverse transcriptase inhibitor-based antiretroviral therapy is not suitable for all treatment-naive HIV-infected persons. OBJECTIVE To evaluate 3 nonnucleoside reverse transcriptase inhibitor-sparing initial antiretroviral regimens to show equivalence for virologic efficacy and tolerability. DESIGN A phase 3, open-label study randomized in a 1:1:1 ratio with follow-up for at least 96 weeks. (ClinicalTrials.gov: NCT00811954). SETTING 57 sites in the United States and Puerto Rico. PATIENTS Treatment-naive persons aged 18 years or older with HIV-1 RNA levels greater than 1000 copies/mL without resistance to nucleoside reverse transcriptase inhibitors or protease inhibitors. INTERVENTION Atazanavir, 300 mg/d, with ritonavir, 100 mg/d; raltegravir, 400 mg twice daily; or darunavir, 800 mg/d, with ritonavir, 100 mg/d, plus combination emtricitabine, 200 mg/d, and tenofovir disoproxil fumarate, 300 mg/d. MEASUREMENTS Virologic failure, defined as a confirmed HIV-1 RNA level greater than 1000 copies/mL at or after 16 weeks and before 24 weeks or greater than 200 copies/mL at or after 24 weeks, and tolerability failure, defined as discontinuation of atazanavir, raltegravir, or darunavir for toxicity. A secondary end point was a combination of virologic efficacy and tolerability. RESULTS Among 1809 participants, all pairwise comparisons of incidence of virologic failure over 96 weeks showed equivalence within a margin of equivalence defined as -10% to 10%. Raltegravir and ritonavir-boosted darunavir were equivalent for tolerability, whereas ritonavir-boosted atazanavir resulted in a 12.7% and 9.2% higher incidence of tolerability discontinuation than raltegravir and ritonavir-boosted darunavir, respectively, primarily because of hyperbilirubinemia. For combined virologic efficacy and tolerability, ritonavir-boosted darunavir was superior to ritonavir-boosted atazanavir, and raltegravir was superior to both protease inhibitors. Antiretroviral resistance at the time of virologic failure was rare but more frequent with raltegravir. LIMITATION The trial was open-label, and ritonavir was not provided. CONCLUSION Over 2 years, all 3 regimens attained high and equivalent rates of virologic control. Tolerability of regimens containing raltegravir or ritonavir-boosted darunavir was superior to that of the ritonavir-boosted atazanavir regimen. PRIMARY FUNDING SOURCE National Institute of Allergy and Infectious Diseases.

failure to Detect Nelfinavir in the Cerebrospinal Fluid of Hiv-1-infected Patients With and Without Aids Dementia Complex

OBJECTIVE To assess the penetration of the HIV-1 protease inhibitor, nelfinavir, into cerebrospinal fluid (CSF). DESIGN Nelfinavir, a commonly used HIV-1 protease inhibitor (PI), is highly effective for reducing plasma viral load. It is deployed clinically in combination with other antiretroviral agents, including nucleoside and nonnucleoside reverse transcriptase inhibitors (NRTIs and NNRTIs). Despite its potency based on plasma HIV-1 RNA results, its effectiveness in reducing HIV-1 RNA levels (i.e., viral load) in the central nervous system (CNS) is less certain. We sampled the CSF as a surrogate for brain because this fluid also is separated from the blood by a barrier to free diffusion, the blood-CSF barrier (BCB), which shares properties with the blood-brain barrier (BBB). These studies of nelfinavir CSF pharmacokinetics exploited the multiple CSF samples derived from individual study subjects who were enrolled in studies the primary objective of which was to compare viral kinetics in CSF and blood in response to antiviral therapy. METHODS Six study subjects, four with and two without AIDS dementia complex, underwent multiple lumbar punctures (LP). Intervals of CSF sampling after drug dosing were varied (from 0.48 hours to 10.3 hours after nelfinavir administration) to quantitate nelfinavir concentrations throughout the steady-state dosing interval. In four study subjects, CSF sampling was accompanied by assessment of nelfinavir levels in plasma before and after LP, whereas in the other two subjects, a single plasma sample was obtained before or after the LP. In total, 25 CSF samples were analyzed. Nelfinavir concentrations in CSF and plasma were determined using an high-performance liquid chromatography (HPLC) method with a limit of quantitation of 25 and 50 ng/ml, respectively. RESULTS Plasma concentrations before and after LP averaged 2420+/-1365 ng/ml and 2528+/-1132 ng/ml, respectively. Nelfinavir was not detected in any of the CSF samples and levels >25 ng/ml were not present in the CSF. Thus, standard therapy with nelfinavir does not result in CSF drug concentrations at or exceeding the IC95 level for most HIV-1 isolates. However, study subjects with high CSF viral loads experienced a marked reduction in the context of the combination-drug regimen including nelfinavir with two subjects showing a comparable CSF response with that in plasma. CONCLUSIONS Nelfinavir does not appreciably penetrate into the CSF. The clinical importance of this observation is not certain, in that in four study subjects who initiated nelfinavir in combination with other antiretroviral therapy, a comparable degree of viral suppression was obtained in both the CSF and the blood when sampled 4 weeks or later after initiating therapy.

CYP2B6 genetic variants are associated with nevirapine pharmacokinetics and clinical response in HIV-1-infected children

Background:Cytochrome P450 2B6 (CYP2B6)-G516T genotype is associated with altered activity of hepatic CYP2B6 and efavirenz pharmacokinetics, but the relationship between the CYP2B6-G516T genotype and nevirapine (NVP) pharmacokinetics in plasma and cerebrospinal fluid (CSF) is limited. Methods:In 126 children who received NVP and protease inhibitors from PACTG 366 and 377 cohorts, CYP2B6 and ATP-binding cassette, sub-family B, member 1 (ABCB1) gene polymorphisms were analyzed using real-time PCR. Plasma NVP pharmacokinetics and clinical data were collected and levels of NVP in CSF were evaluated in children with HIV-related neurologic diseases. Results:NVP oral clearance in children with the CYP2B6-516-T/T genotype (homozygous variant, n = 14) was 1.6 l/h per m2, which was significantly decreased compared to 2.3 l/h per m2 in those with the -G/G (wild type, n = 49, P = 0.002) and 2.1 l/h per m2 in those with the -G/T genotype (heterozygous variants, n = 63, P = 0.008). Furthermore, children with the -T/T genotype had a significant increase in CD4+ T-cell percentage (+9.0%) compared with those with the -G/G (+3.2%, P = 0.01) and -G/T genotype (+5.0%, P = 0.04) from baseline to week 12. The same trend continued at week 24. Although ABCB1-C3435T genotypes did not affect plasma NVP pharmacokinetics (P = 0.39), the NVP CSF: plasma ratios were significantly higher in children with the ABCB1-3435-C/T or -T/T genotypes (0.62, n = 9) in comparison with those with the ABCB1-3435-C/C genotype (0.43, n = 5) (P = 0.01). Conclusions:The CYP2B6-G516T genotype alters NVP pharmacokinetics and the immunologic response to NVP-containing HAART regimens in children. These data suggest that the CYP2B6-G516T is an important genetic variant that alters the pharmacokinetics and response to HAART regimens containing NVP.