Evaluation of a single-platform microcapillary flow cytometer for enumeration of absolute CD4+ T-lymphocyte counts in HIV-1 infected Thai patients

BACKGROUND: Various assays are used to enumerate peripheral blood absolute CD4+ T-lymphocytes. Flow cytometry is considered the gold standard for this purpose. However, the high cost of available flow cytometers and monoclonal antibody reagents make it difficult to implement such methods in the resource-poor settings. In this study, we evaluated a cheaper, recently developed single-platform microcapillary cytometer for CD4+ T-lymphocyte enumeration, the personal cell analyzer (PCA), from Guava Technologies. METHODS: CD4+ and CD8+ T-lymphocyte counts in whole blood samples from 250 HIV-1 infected Thais were determined, using a two-color reagent kit and the Guava PCA, and compared with the results obtained with two reference microbead-based methods from Becton Dickinson Biosciences: the three-color TruCOUNT tube method and the two-color FACSCount method. Statistical correlations and agreements were determined using linear correlation and Bland-Altman analysis. RESULTS: Absolute CD4+ T-lymphocyte counts obtained using the Guava PCA method highly correlated with those obtained using TruCOUNT method (R(2) = 0.95, mean bias +13.1 cells/microl, limit of agreement [LOA]-117.9 to +144.1 cells/microl) and the FACSCount method (R2 = 0.94, mean bias = +33.2 cells/microl, LOA-101.8 to +168.3 cells/microl). Absolute CD8+ T-lymphocyte counts obtained using the Guava PCA method also highly correlated with those obtained with the two reference methods (R(2) = 0.92 and 0.88, respectively). CONCLUSION: This study shows that the enumeration of CD4+ T-lymphocytes using the Guava microcapillary cytometer PCA method performed well when compared with the two reference bead-based methods. However, like the two reference methods, this new method needs substantial technical expertise.     

Cell cycle distribution of CD4+ lymphocytes in HIV-1-infected subjects

BACKGROUND: Apoptosis is one of the possible explanations for the progressive loss of CD4(+) T lymphocytes in infection with the human immunodeficiency virus (HIV), which may interfere with cell cycle distribution. This study evaluated the cell cycle of CD4(+) and CD8(+) lymphocytes in HIV-infected subjects and controls. METHODS: Two methods to identify lymphocytes for cell cycle analysis were evaluated, magnetic beads and concurrent staining, and both were followed by propidium iodide DNA labeling. The chosen method was used to evaluate the cell cycle of lymphocytes in HIV-1-infected subjects and controls. RESULTS: There was no significant difference between the two methods, although a higher variability was observed with the magnetic bead cell separation method. A higher proportion of cells in the S phase was observed in HIV-1 patients (2.69% vs. 1.19%, P = 0.016), coupled with a decrease in G(1) (96.11% vs. 98.10%, P = 0.005) in CD4(+) lymphocytes, a phenomenon not observed in CD8(+) lymphocytes. No correlation was detected between the different cell cycle phases and T-lymphocyte counts or viral load. CONCLUSIONS: The present work developed a new approach to evaluate lymphocyte cell cycle distribution, applied in the setting of HIV-1 infection. It may contribute to the understanding of the CD4(+) T-lymphocytes depletion seen in these patients.     

Relationship between CD4 count, viral burden, and quality of life over time in HIV-1-infected patients

BACKGROUND: Although surrogate markers such as CD4 counts and viral burden (HIV-1 RNA) are predictive of AIDS-related disease progression, little is known about the relationship between changes in surrogate markers and health-related quality of life (HRQOL) outcomes. This study investigated how changes in CD4/mm3 and viral burden (RNA copies/mL) are related to changes in HRQOL as indexed by the Medical Outcomes Study HIV Health Survey (MOS-HIV-30). METHODS: Subjects were HIV-1-infected patients with CD4 counts <300/mm3 enrolled in a double-blind, randomized clinical trial of delavirdine. As part of the clinical protocol, patients completed the MOS-HIV-30, from which the Physical Health (PHS) and Mental Health (MHS) summary scores were used for analyses. HRQOL and surrogate marker data assessed up to 2 years after randomization were analyzed for a total of 1,112 patients. RESULTS: Individual patients' initial status (intercepts) and rates of change (slopes) over time for log CD4, log RNA, PHS, and MHS were estimated with the use of empirical Bayes. Early response to treatment correlated with HRQOL better for RNA than for CD4. However, the relationship between weekly change and HRQOL was stronger for CD4 than for RNA. CONCLUSIONS: Surrogate markers are significantly associated with HRQOL outcomes. Improvements in HRQOL over time are associated with lower initial viral load and with increases in CD4 counts. Limitations concerning the restricted variability of the change scores are addressed.     

Functional Fas-ligand expression on T cells from HIV-1-infected patients is unrelated to CD4+ lymphopenia

Recent studies have demonstrated that the expression of Fas by peripheral T cells from HIV-1⁺ patients is deregulated and increases the susceptibility of these cells to undergo apoptosis. Here, we show that secretion of Fas-ligand (L), the complementary agonist of Fas, is abnormally upregulated in CD4⁺ cells from HIV-1-infected individuals, particularly during the non-lymphopenic stages of the disease. An increase of soluble Fas-L occurred in T cell cultures from 26 patients with a number of CD4⁺ cells higher than 400/μl, whereas it was almost undetectable in cultures from 21 severely lymphopenic patients (CD4⁺ <200/μl). The MTT test, cytofluorimetric analysis of cellular DNA, cytotoxicity, and proliferative assays using the Fas-transfected WC8 mouse lymphoma confirmed the cytocidal capability of T cell supernatants from non-lymphopenic patients. Double-fluorescence analysis revealed that the majority of CD4⁺ cells (approximately 90%) in these cultures secreted Fas-L in the presence of high intracellular γ-interferon and low Bcl-2. In contrast, the CD8⁺/Fas-L⁺ population was comparably decreased (approximately 55%). Molecular cloning of Fas-L revealed a substantial expression of Fas-L mRNA in cells from non-lymphopenic patients compared with patients with advanced disease and healthy controls. Since CD4⁺ cells of Th1 phenotype are impaired during HIV-1 infection and show high cellular expression of Fas-L, it is conceivable that excess Fas-L during the early or non-lymphopenic phase of the disease increases the extent of apoptosis in these cells by the Fas/Fas-L pathway. The defective expression of the ligand in severely lymphopenic stages could be explained by exhaustion of this mechanism as the disease progresses.     

Nef protein induces differential effects in CD8+ cells from HIV-1-infected patients

BACKGROUND: The Nef protein of HIV-1 is suspected to play a role in the depletion of uninfected CD4+ lymphocytes that leads to AIDS. By contrast its effect on CD8+ cells, whose functions are also deregulated during HIV-1 infection, is presently unclear. Here we describe a number of derangements induced in vitro by Nef in CD8+ cells from HIV-1-infected patients. DESIGN: Peripheral lymphocytes from 16 HIV-1+ subjects and 9 uninfected individuals were cultivated on a Nef-transfected mouse fibroblast layer exposing the carboxyl-terminal region of the viral protein on cell membrane. The cultures were then measured for both apoptosis and proliferation by subdiploid DNA content and Ki67 expression, respectively, whereas the molecular analysis of purified CD8+ cells investigated the Fas-L mRNA levels in Nef-treated CTLs. In addition, we evaluated the Nef-induced variation in the extent of CD8+/HLA-DR+ subset, which includes non cytotoxic cells secreting T-cell antiviral factor (CAF) and a soluble factor inhibiting the HIV-1 replication. RESULTS: The viral protein induced in peripheral blood lymphocytes (PBL) a moderate tendency to proliferate, as measured by the increment of Ki67 antigen, particularly on the CD8+ subset of HIV-1 infected individuals (P < 0.05). This profile was particularly evident in cultures from patients with severe CD4+ lymphopenia and paralleled an apparent expansion of the CD8+/CD57+ suppressor cell subset. Molecular analysis of purified CD8+ cells revealed a defective expression of Fas-L mRNA in Nef-cultured CTLs, whereas the viral protein exerted a down modulatory effect on the CD8+/HLA-DR+ subset (P < 0.05), thus suggesting a potential inhibition of CAF. CONCLUSIONS: These results support a potential role of Nef in the progression of HIV-1 infection as a number of cellular functions are affected in the CD8+ subset. In particular, the defective functions of CD8+ cells induced by the viral protein could contribute, at least partly, to the escape of HIV-1 from the immune control of these cells.     

CD4+ T-cell count increase in HIV-1-infected patients with suppressed viral load within 1 year after start of antiretroviral therapy

BACKGROUND: CD4+ T-cell recovery in patients with continuous suppression of plasma HIV-1 viral load (VL) is highly variable. This study aimed to identify predictive factors for long-term CD4+ T-cell increase in treatment-naive patients starting combination antiretroviral therapy (cART). METHODS: Treatment-naive patients in the Swiss HIV Cohort Study reaching two VL measurements <50 copies/ml >3 months apart during the 1st year of cART were included (n=1816 patients). We studied CD4+ T-cell dynamics until the end of suppression or up to 5 years, subdivided into three periods: 1st year, years 2-3 and years 4-5 of suppression. Multiple median regression adjusted for repeated CD4+ T-cell measurements was used to study the dependence of CD4+ T-cell slopes on clinical covariates and drug classes. RESULTS: Median CD4+ T-cell increases following VL suppression were 87, 52 and 19 cells/microl per year in the three periods. In the multiple regression model, median CD4+ T-cell increases over all three periods were significantly higher for female gender, lower age, higher VL at cART start, CD4+ T-cell <650 cells/microl at start of the period and low CD4+ T-cell increase in the previous period. Patients on tenofovir showed significantly lower CD4+ T-cell increases compared with stavudine. CONCLUSIONS: In our observational study, long-term CD4+ T-cell increase in drug-naive patients with suppressed VL was higher in regimens without tenofovir. The clinical relevance of these findings must be confirmed in, ideally, clinical trials or large, collaborative cohort projects but could influence treatment of older patients and those starting cART at low CD4+ T-cell levels.     

Stavudine, didanosine and nevirapine in antiretroviral-naive HIV-1-infected patients

In an ongoing, open-label, non-comparative study, the safety and efficacy of nevirapine/stavudine/didanosine were evaluated in 100 antiretroviral-naive adults with CD4 cell counts > or = 200 cells/mm3 and plasma HIV-1 RNA (pVL) > or = 5000 copies/ml. Sixty patients received nevirapine twice daily (VIRGO I) and 40 received nevirapine once daily (VIRGO II); all patients received didanosine once a day. After median follow-ups of 44 weeks in VIRGO I and 30 weeks in VIRGO II, the following virological results were observed (ongoing study): an intent-to-treat, non-completer equals failure analysis at week 24 showed the proportions of patients with pVL <500 copies/ml were 78% in VIRGO I (60% <50 copies/ml) and 75% in VIRGO II. An on-treatment analysis at week 52 showed 80% of patients with a pVL <500 copies/ml and 59% with <50 copies/ml in VIRGO I. The mean CD4 cell count increase was +171 cells/mm3 at week 24 and +218 cells/mm3 at week 52 in VIRGO I and +158 cells/mm3 at week 24 in VIRGO II. Cutaneous rash (grades 1 to 3) occurred in 24% of patients leading to nevirapine discontinuation in eight of 24 patients. Five other patients discontinued therapy during the first 24 weeks because of hepatic cytolysis, peripheral neuropathy or biological pancreatitis. The nevirapine/stavudine/didanosine combination is a convenient and safe regimen, with rapid and potent immunological and antiviral effects sustained over 12 months.     

Interaction between artemether-lumefantrine and nevirapine-based antiretroviral therapy in HIV-1-infected patients

Artemether-lumefantrine and nevirapine-based antiretroviral therapy (ART) are the most commonly recommended first-line treatments for malaria and HIV, respectively, in Africa. Artemether, lumefantrine, and nevirapine are metabolized by the cytochrome P450 3A4 enzyme system, which nevirapine induces, creating potential for important drug interactions. In a parallel-design pharmacokinetic study, concentration-time profiles were obtained in two groups of HIV-infected patients: ART-naïve patients and those stable on nevirapine-based therapy. Both groups received the recommended artemether-lumefantrine dose. Patients were admitted for intense pharmacokinetic sampling (0 to 72 h) with outpatient sampling until 21 days. Concentrations of lumefantrine, artemether, dihydroartemisinin, and nevirapine were determined by validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods. The primary outcome was observed day 7 lumefantrine concentrations, as these are associated with therapeutic response in malaria. We enrolled 36 patients (32 females). Median (range) day 7 lumefantrine concentrations were 622 ng/ml (185 to 2,040 ng/ml) and 336 ng/ml (29 to 934 ng/ml) in the nevirapine and ART-naïve groups, respectively (P = 0.0002). The median artemether area under the plasma concentration-time curve from 0 to 8 h [AUC_{(0-8 h)}] (P < 0.0001) and dihydroartemisinin AUC_{(60-68 h)} (P = 0.01) were lower in the nevirapine group. Combined artemether and dihydroartemisinin exposure decreased over time only in the nevirapine group (geometric mean ratio [GMR], 0.76 [95% confidence interval {CI}, 0.65 to 0.90]; P < 0.0001) and increased with the weight-adjusted artemether dose (GMR, 2.12 [95% CI, 1.31 to 3.45]; P = 0.002). Adverse events were similar between groups, with no difference in electrocardiographic Fridericia corrected QT and P-R intervals at the expected time of maximum lumefantrine concentration (T_max). Nevirapine-based ART decreased artemether and dihydroartemisinin AUCs but unexpectedly increased lumefantrine exposure. The mechanism of the lumefantrine interaction remains to be elucidated. Studies investigating the interaction of nevirapine and artemether-lumefantrine in HIV-infected patients with malaria are urgently needed.     

Evolution of transmitted HIV-1 drug resistance in HIV-1-infected patients in Italy from 2000 to 2010

Prevalence and predictors of transmitted drug resistance (TDR), defined as the presence of at least one WHO surveillance drug resistance mutation (SDRM), were investigated in antiretroviral-na?ve HIV-1-infected patients, with a genotypic resistance test (GRT) performed ≤6 months before starting cART between 2000 and 2010. 3163 HIV-1 sequences were selected (69% subtype B). Overall, the prevalence of TDR was 12% (13.2% subtype B, 9% non-B). TDR significantly declined overall and for the single drug classes. Older age independently predicted increased odds of TDR, whereas a more recent GRT, a higher HIV-RNA and C vs. B subtype predicted lower odds of TDR.     

Plasma and intracellular population pharmacokinetic analysis of tenofovir in HIV-1-infected patients

The relationships among the dose of tenofovir disoproxil fumarate (TDF), tenofovir (TFV) plasma concentrations, and intracellular TFV diphosphate (TFV-DP) concentrations are poorly understood. Our objective was to characterize TFV and TFV-DP relationships. Data were pooled from two studies in HIV-infected persons (n = 55) on stable antiretroviral therapy. TFV and TFV-DP were measured with validated liquid chromatography/tandem mass spectrometry (LC/MS/MS) methods. Nonlinear mixed effects modeling (NONMEM 7) was used to develop the population model and explore the influence of covariates on TFV. A sequential analysis approach was utilized. A two-compartment model with first-order absorption best described TFV PK (FOCEI). An indirect stimulation of response model best described TFV-DP, where formation of TFV-DP was driven by plasma TFV concentration. Final plasma population estimates were as follows: absorption rate constant, 1.03 h(-1); apparent clearance (CL/F), 42 liters/h (33.5% interindividual variability [IIV]); intercompartment clearance, 181 liters/h; apparent central distribution volume (Vc/F), 273 liters (64.8% IIV); and apparent peripheral distribution volume (Vp/F), 440 liters (46.5% IIV). Creatinine clearance was the most significant covariate on CL/F and Vc/F. The correlation between CL/F and Vc/F was 0.553. The indirect response model for TFV-DP resulted in estimates of the maximal intracellular concentration (E(max)), the TFV concentration producing 50% of E(max) (EC(50)), and the intracellular elimination rate constant (k(out)) of 300 fmol/10(6) cells (82% IIV), 100 ng/ml (106% IIV), and 0.008 h(-1), respectively. The estimated k(out) gave an 87-h TFV-DP half-life. A predictive check assessment indicated satisfactory model performance. This model links formation of TFV-DP with plasma TFV concentrations and should facilitate more informed investigations of TFV clinical pharmacology.     

Investigation of emtricitabine-associated skin pigmentation and safety in HIV-1-infected Japanese patients

Emtricitabine (FTC) has been reported to cause skin pigmentation (SP), and the incidence of SP associated with FTC varied with ethnicity, with a higher rate in African-American patients (8%). We assessed the incidence of SP in Japanese HIV-1-infected patients receiving combination antiretroviral therapy (cART) with FTC for a period of 48 weeks and confirmed new findings of FTC-associated SP, including pathological characteristics. This was a multicenter, prospective, longitudinal non-randomized study. We evaluated the appearance of SP at 48 weeks as the primary endpoint in 155 Japanese patients, and secondary endpoints included the characteristics of the SP (location, color tone, size, and progression). Six cases (3.9%) of SP occurred at a median of 124 days (range: 7–259 days) within 48 weeks. The SP looked like an isolated dark spot, 1–2 mm in diameter, mainly on the hands and/or feet. The severity of all the SPs was mild. Each SP had disappeared or faded at a median of 112 days (range: 28–315 days) with continued FTC. FTC-associated SP was considered to be lentigo simplex by dermatoscopy and pathological appearance. In summary, the incidence of FTC-associated SP in Japanese patients was 3.9%, and was comparable to the previously reported incidence in Asian patients (4%). FTC-associated SP was not associated with any clinically significant symptoms and has little clinical significance.     

Pharmacokinetic interaction between chemotherapy for non-Hodgkin's lymphoma and protease inhibitors in HIV-1-infected patients

OBJECTIVES: We have investigated whether chemotherapy for HIV-related systemic non-Hodgkin's lymphoma (NHL) affects the pharmacokinetics of protease inhibitors. PATIENTS AND METHODS: This was a prospective, open-label, non-randomized, two-way crossover trial in HIV-1-infected patients treated with highly active antiretroviral therapy and chemotherapy for NHL. Seven patients received indinavir at a dosage of 800 mg three times daily and three patients received nelfinavir at a dosage of 750 mg three times daily. Chemotherapy consisted of adriamycin, cyclophosphamide, vincristine and prednisolone (CHOP). Each patient had blood samples for protease inhibitor pharmacokinetics drawn concomitantly with or independently of the CHOP cycle. RESULTS: When indinavir was given concomitantly with CHOP, the AUC(0-8) increased by 38% (20.5 +/- 9.0 versus 14.9 +/- 9.5 mg.h/L; P=0.03), and was comparable to historical controls. By contrast, the AUC(0-8) of indinavir administered without CHOP was lower than expected. A similar trend was observed with nelfinavir. Likewise, we observed a significant number of patients with C(0) and C(8) below the IC(50) for the wild-type virus (0.1 mg/L) when the drug was administered without CHOP. CONCLUSIONS: Therapeutic drug monitoring of protease inhibitors should be part of the work-up in HIV-infected patients receiving chemotherapy for NHL.     

Oligoclonal expansion of HIV-specific cytotoxic CD8 T lymphocytes in the skin of HIV-1-infected patients with cutaneous pseudolymphoma.

A massive infiltration of the skin by activated CD8+ T lymphocytes involving both the dermis and the epidermis has been found in HIV-1-infected patients presenting with a chronic skin rash. We characterized the T cell receptor (TCR) BV-BJ junctional diversity of the skin-infiltrating lymphocytes (SILs) in four patients. The SILs expressed a limited set of TCRBV gene segments. Complementarity determining region 3 length analysis further emphasized their oligoclonality, suggesting that antigen stimulation might be responsible for the cutaneous T cell expansion. Furthermore, independent skin biopsies obtained from the same individual were shown to harbor distinct T cell repertoires, possibly reflecting the spatial heterogeneity of the antigenic stimuli. The CD8+ cytotoxic T lymphocyte (CTL) lines isolated from the skin rash in one patient exhibited a specific, class I MHC-restricted cytotoxic activity against HIV-1 Gag- and Pol-expressing target cells, whereas CTL lines derived from the skin lesions of a second patient were shown to be predominantly Env-specific. Taken together, these data demonstrate the infiltration of HIV-specific CTLs in the skin of HIV-infected patients, and suggest that in addition to their known role in controlling the retroviral infection, these CTLs may also be involved in the pathogenesis of cutaneous inflammatory disorders occurring during the course of HIV infection.     

Serum adiponectin and metabolic parameters in HIV-1-infected patients after substitution of nevirapine for protease inhibitors

BACKGROUND: In the context of HIV infection and antiretroviral therapy, adiponectin concentrations have been shown to be related to lipodystrophy, metabolic alterations and HIV-protease inhibitor (PI) use. The replacement of PI by nevirapine has improved the lipid profile of patients under antiretroviral therapy. The aim of the present study was to examine whether adiponectin concentration or insulin sensitivity level correlate with the modifications of lipid parameters after the switch of PI by nevirapine. MATERIAL AND METHODS: The evolution of metabolic parameters before and after 6 months of substitution of nevirapine for protease inhibitors was evaluated in a cohort of 55 HIV-1 infected patients. Adiponectin concentration, insulin sensitivity, lipid profile, cholesterol ester transfer protein (CETP) mass concentration and triglyceride enrichment of HDL were determined before and after the replacement of PI by nevirapine. Insulin sensitivity was evaluated by the HOMA model assessment. RESULTS: Twenty-four weeks of treatment with nevirapine improved significantly the lipid profile with a significant reduction of apoB (from 0.98 to 0.92 g L(-1); P = 0.005) and triglyceride (from 2.02 to 1.66 mmol L(-1); P = 0.02). HDL cholesterol and apoA1 increased significantly (from 0.99 to 1.19 mmol L(-1); P = 0.001 and from 1.40 to 1.57 g L(-1); P < 0.001, respectively). The triglyceride enrichment of HDL significantly decreased after the replacement of PI by nevirapine (from 0.248 +/- 0.092 to 0.213 +/- 0.093; P = 0.003). At baseline, and after 24 weeks of nevirapine treatment, we observed significant correlations between adiponectin level and lipid parameters [(HDL-cholesterol (r = 0.66, P = 0.001 and r = 0.69, P = 0.001); triglycerides (r = -0.42, P = 0.002 and r = -0.57, P = 0.001), and triglyceride enrichment of HDL (r = -0.43, P = 0.005 and r = -0.53, P = 0.005)]. Twenty-four weeks of treatment with nevirapine did not significantly change adiponectin concentrations (from 984 to 1086 micro g L(-1), P = 0.22), CETP mass and insulin sensitivity. CONCLUSION: This study shows that even though a strong correlation was found between adiponectin and some metabolic parameters at baseline and after 24 weeks of treatment by nevirapine, the improvement of lipid profile observed after the replacement of PI by nevirapine was not in relation to the change of plasma adiponectin concentration. The significant decrease of triglyceride enrichment of HDL after the replacement of PI by nevirapine probably leads to a decreased catabolism of HDL lipoprotein, and consequently explains the increase of plasma HDL concentration observed in this study.     

类风湿关节炎患者外周血T淋巴细胞亚群CD4~+/CD8~+表达的意义

目的探讨类风湿关节炎(RA)患者外周血T淋巴细胞亚群CD4+/CD8+的表达变化对疾病进展的关系。方法采用流式细胞术检测94例RA患者和22例健康对照者外周血T淋巴细胞亚群CD4+/CD8+。其中94例RA患者按RA疾病活动指数(DAS28)评分分为低值、中值、高值3组。结果与健康对照组比较,RA组外周血中CD3+CD4+T淋巴细胞的表达率明显升高(P0.05),其中CD3+CD4+T淋巴细胞在DAS28低值组为(41.03±9.53)%,DAS28中值组为(42.16±7.08)%,DAS28高值组为(43.72±9.63)%;CD3+CD8+T淋巴细胞表达率明显降低(P0.05),其中CD3+CD8+T淋巴细胞在DAS28低值组为(21.33±6.67)%,DAS28中值组为(21.39±7.36)%,DAS28高值组为(21.28±6.60)%。结论CD4+/CD8+比值与RA患者疾病进程相关,表明CD4+/CD8+失衡在RA的发病中发挥了重要作用。     

Pharmacokinetics and pharmacodynamics of the non-nucleoside reverse-transcriptase inhibitor etravirine in treatment-experienced HIV-1-infected patients

The pharmacokinetics and pharmacodynamics of the antiretroviral agent etravirine were evaluated in two phase III clinical trials. Pharmacokinetic data were available in 577 patients randomized to receive etravirine. The mean (SD) population-pharmacokinetics-derived area under the concentration-time curve at 12?h (AUC(12?h)) and concentration at 0?h (C(0?h)) were 5,501?(4,544) ng·h/ml and 393?(378) ng/ml, respectively. Hepatitis C coinfection raised etravarine exposure, and concomitant use of tenofovir disoproxil fumarate lowered etravirine exposure, but these changes were not considered clinically relevant. Etravirine apparent oral clearance was not affected by age, weight, sex, race, hepatitis B coinfection status, creatinine clearance, or concomitant use of enfuvirtide. Virologic response (<50?copies/ml) at week 24 was 59% in patients randomized to etravirine vs. 41% in those receiving placebo (P < 0.0001). There was no apparent relationship between etravirine pharmacokinetics and either efficacy or safety. Factors other than the pharmacokinetics of etravirine such as the characteristics of the patients and the disease, as well as characteristics of the treatment regimen, predict virologic response.