Factors associated with viral rebound among highly treatment-experienced HIV-positive patients who have achieved viral suppression

Objective

More and more highly treatment‐experienced patients are achieving viral suppression. However, the durability of suppression remains unclear.

Methods

Patients from Royal Free Hospital (London, UK) and JW Goethe University Hospital (Frankfurt, Germany) who had failed ≥1 antiretroviral (ARV) regimen in all three main drug classes and ≥3 previous ARV regimens and subsequently achieved viral load <50 HIV‐1 RNA copies/mL were included. They were followed until stopping pre‐combination antiretroviral therapy, end of follow‐up or viral rebound (two viral loads >400 copies/mL).

Results

Two hundred and forty‐seven patients contributed 723 person‐years and 114 viral rebounds [rate=15.8 per 100 person‐years; 95% confidence interval (CI) 12.9–18.7]. More recent calendar years of viral suppression [relative risk (RR)=0.90 per year later; 95% CI 0.81–1.00; P=0.05] and greater number of ARVs in the regimen not previously failed (RR=0.78 per 1 ARV more; 95% CI 0.65–0.95; P=0.01) were associated with lower viral rebound rates. At 0–1, 1–2, 2–3 and >3 years after achieving suppression, the rebound rates were 30.9, 9.2, 4.3 and 3.5 per 100 person‐years, respectively. Compared to 0–1 years, the adjusted RRs (95% CIs) after 1–2, 2–3 and >3 years were 0.33 (0.18–0.58), 0.21 (0.09–0.48) and 0.14 (0.06–0.33), respectively (P<0.0001).

Conclusions

Although rebound rates are high, especially in the first year after viral suppression, this risk reduces substantially if highly treatment‐experienced patients can maintain viral suppression.     

Cytochrome P450 2B6 516G→T is associated with plasma concentrations of nevirapine at both 200 mg twice daily and 400 mg once daily in an ethnically diverse population

Objectives

The aim of the study was to characterize the impact of the cytochrome P450 2B6 (CYP2B6), CYP3A4, CYP3A5 and ATP‐binding cassette sub‐family B member 1 (ABCB1) polymorphisms on nevirapine plasma concentrations.

Methods

A total of 104 patients (82% male; 26% non‐Caucasian) were genotyped for eight single nucleotide polymorphisms at four loci (CYP2B6, CYP3A4, CYP3A5 and MDR1). Nevirapine plasma concentrations were determined using high‐performance liquid chromatography.

Results

Non‐Caucasian ethnicity [5609 ng/mL (n=27) for non‐Caucasians vs. 3771 ng/mL (n=77) for Caucasians; P<0.0001] and CYP2B6 516G→T [GG, 3574 ng/mL (n=50); GT, 4634 ng/mL (n=50); TT, 8170 ng/mL (n=4); P_{analysis of variance (anova)} =0.001] were significantly associated with a higher nevirapine trough concentration (C_trough). The latter association was maintained with both 200 mg twice daily (bid) and 400 mg once daily (qd) dosing [GG, 3527 ng/mL (n=30); GT, 4525 ng/mL (n=32); TT, 7020 ng/mL (n=2); P_anova =0.05 and GG, 3645 ng/mL (n=20); GT, 4861 ng/mL (n=17); TT, 9508 ng/mL (n=2); P_anova =0.01, respectively]. In a multivariable analysis, CYP2B6 516G→T and non‐Caucasian ethnicity remained significant predictors of nevirapine C_trough but CYP2B6 516G→T homozygosity had the greatest effect (108% higher, 46% higher). No associations were found between nevirapine C_trough and the remaining polymorphisms.

Conclusion

In this population, both non‐Caucasian ethnicity and carriage of the variant allele of CYP2B6 516G→T were significant predictors of nevirapine C_trough. The association between CYP2B6 516G→T and higher plasma nevirapine exposure was maintained at both bid and qd dosing.     

Neural respiratory drive in healthy subjects and in COPD

The aim of the present study was to use the diaphragm electromyogram (EMG(di)) to compare levels of neural respiratory drive (NRD) in a cohort of healthy subjects and chronic obstructive pulmonary disease (COPD) patients, and to investigate the relationship between NRD and pulmonary function in COPD. EMG(di) was recorded at rest and normalised to peak EMG(di) recorded during maximum inspiratory manoeuvres (EMG(di) % max) in 100 healthy subjects and 30 patients with COPD, using a multipair oesophageal electrode. EMG(di) was normalised to the amplitude of the diaphragm compound muscle action potential (CMAP(di,MS)) in 64 healthy subjects. The mean+/-sd EMG(di) % max was 9.0+/-3.4% in healthy subjects and 27.9+/-9.9% in COPD patients, and correlated with percentage predicted forced expiratory volume in one second, vital capacity and inspiratory capacity in patients. EMG(di) % max was higher in healthy subjects aged 51-80 yrs than in those aged 18-50 yrs (11.4+/-3.4 versus 8.2+/-2.9%, respectively). Observations in the healthy group were similar when peak EMG(di) or CMAP(di,MS) were used to normalise EMG(di). Levels of neural respiratory drive were higher in chronic obstructive pulmonary disease patients than healthy subjects, and related to disease severity. Diaphragm compound muscle action potential could be used to normalise diaphragm electromyogram if volitional inspiratory manoeuvres could not be performed, allowing translation of the technique to critically ill and ventilated patients.     

Tungstic acid reduction of cold-resistant stress-induced ulceration in rats

Sprague-Dawley rats were restrained at 4°C for 2 h (stress). Tungstic acid in a single dose of 0.01, 0.1, 1, 10, 100 or 300 mg/kg (dissolved in distilled water) was administered intragastrically to animals 30 min prior to stress. Stress induced significant gastric mucosal damage, whereas tungstic acid pretreatment dose-dependently reduced lesion formation. Doses of tungstic acid of 1 mg/kg and higher significantly (P < 0.05–0.001) decreased ulcers. The mucosal mast cell counts in rats pretreated with tungstic acid were significantly higher than those of control rats. In motility experiments using oral administration of amberlite pellets, pretreatment with tungstic acid dose-dependently reduced the gastric emptying rate during a 1 h period of stress. Gastric mucosal xanthine oxidase and superoxide dismutase (SOD) activities, after pretreatment with a single dose of tungstic acid, were not altered in stressed animals. It is suggested that tungstic acid effectively antagonizes stress-induced gastric ulcers, possibly by decreasing motility and mass cell degranulation. Xanthine oxidase and SOD activities and mucous content were not changed in the gastric mucosa by the present method of tungstic acid administration.     

Identification of a distinct low-affinity receptor for human interleukin-4 on pre-B cells

Biotinylated interleukin-4 (IL-4) was used to examine IL-4 receptor (IL- 4R) expression on a range of human B-cell lines by flow cytometry. Using high concentrations of biotinylated IL-4, we have identified a novel low-affinity IL-4 receptor expressed at high levels on pre-B lines. Expression of this low-affinity receptor did not correlate with detected mRNA levels for the previously cloned receptor or with reactivity of two anti-human IL-4R monoclonal antibodies (MoAb). Radiolabeled IL-4 cross-linking studies using pre-B lines showed a doublet of 65 to 75 Kd in contrast to the 110- to 130-Kd molecule detected on cells expressing the cloned IL-4R. A soluble IL-4 binding protein (IL-4bp) was purified from the supernatants of three pre-B lines expressing the low-affinity receptor on their surface. IL-4bp could block both IL-4-mediated CD23 induction on tonsil B cells and IL- 4-induced inhibition of proliferation of the pre-B line JM1. Partial N- terminal amino acid sequence was obtained from purified IL-4bp that confirmed this protein to be novel. A 12 amino acid peptide based on the IL-4bp sequence was used to produce a polyclonal antiserum that was reactive with purified IL-4bp, and also bound to the surface of pre-B cells but not to murine CTLL cells transfected with the human IL-4R. Blocking MoAb against the previously characterized high-affinity receptor inhibited IL-4-mediated proliferation of hIL-4R+ CTLL cells but had no effect on IL-4-induced inhibition of JM1 cell proliferation, and only partially inhibited IL-4-mediated CD23 and sIgM induction and proliferation of tonsil B cells. The data presented here provide evidence for a novel cell-surface expressed low-affinity IL-4R that also exists as a biologically active soluble IL-4 binding protein.     

Oxidative inactivation of plasmin and other serine proteases by copper and ascorbate

Fibrin thrombi form at sites of injury, where leukocytes release a variety of oxidants. To determine whether oxidants might affect proteins of the fibrinolytic system, we examined the effects of various oxidants on plasmin. Plasmin was not inhibited by micromolar concentrations of hypochlorous acid, chloramine T, or H2O2. Neither Fe nor Cu affected plasmin alone or in the presence of H2O2. However, incubation of plasmin with 5 mumol/L Cu(I or II) in the presence of the reducing agent ascorbic acid resulted in a loss of its hydrolytic activity towards proteins as well as towards small synthetic substrates. The addition of EDTA, but not mannitol, prevented its inactivation. Inactivation was prevented by the addition of catalase and accelerated by hydrogen peroxide. Preincubation of plasmin with the competitive inhibitor alpha-N-acetyl-L-lysine methyl ester prevented inactivation by Cu(II) and ascorbate. These results together suggest site-specific oxidation of plasmin's active site. Treatment of the plasminogen activators tissue plasminogen activator and two-chain urokinase-type plasminogen activator, as well as trypsin, neutrophil elastase, and thrombin with Cu(II) and ascorbate resulted in a loss of their amidolytic and proteolytic activity, indicating the general susceptibility of serine proteases to this type of oxidation. Oxidation of the zymogens Glu-plasminogen and single-chain urokinase-type plasminogen activator by Cu(II) and ascorbate resulted in the failure of these molecules to generate active enzymes when treated with plasminogen activators or plasmin, respectively. The active site His residue may be the target of oxidative inactivation, as evidenced by the partial protection afforded plasmin by the addition of Zn(II), histidine, or the platinum derivative, platinum(II) (2,2':6',2"- terpyridine) chloride. Because platelets contain micromolar concentrations of Cu and leukocytes are rich in ascorbate, Cu-dependent site-specific oxidation might play a role in modulating proteolytic events and the life span of thrombi formed at sites of tissue injury.     

群勃龙及其人尿代谢物的GC/MSD分析

群勃龙(去甲雄三烯醇酮,trenbolone)在MsTFA,MBTFA,MO-MSTFA衍生化后形成的TMS醚式和TFA酯化产物,经GC/MSD分析,获得各自的特征图谱,讨论了有关的衍生化问题。群勃龙阳性尿样分析结果显示,其主要代谢产物是表群勃龙(epitrenbolone)和可能的羟基群勃龙(hydroxy-trenbolone),另有少量原型以及可能有去甲雄三烯二酮(triendione)存在。