The combination of kidney function variables with cell cycle arrest biomarkers identifies distinct subphenotypes of sepsis-associated acute kidney injury: a post-hoc analysis (the PHENAKI study)

BACKGROUND

The severity and course of sepsis-associated acute kidney injury (SA-AKI) are correlated with the mortality rate. Early detection of SA-AKI subphenotypes might facilitate the rapid provision of individualized care.

PATIENTS AND METHODS

In this post-hoc analysis of a multicenter prospective study, we combined conventional kidney function variables with serial measurements of urine (tissue inhibitor of metalloproteinase-2 [TIMP-2])* (insulin-like growth factor-binding protein [IGFBP7]) at 0, 6, 12, and 24 h) and then using an unsupervised hierarchical clustering of principal components (HCPC) approach to identify different phenotypes of SA-AKI. We then compared the subphenotypes with regard to a composite outcome of in-hospital death or the initiation of renal replacement therapy (RRT).

RESULTS

We included 184 patients presenting SA-AKI within 6 h of the initiation of catecholamines. Three distinct subphenotypes were identified: subphenotype A (99 patients) was characterized by a normal urine output (UO), a low SCr and a low [TIMP-2]*[IGFBP7] level; subphenotype B (74 patients) was characterized by existing chronic kidney disease (CKD), a higher SCr, a low UO, and an intermediate [TIMP-2]*[IGFBP7] level; and subphenotype C was characterized by very low UO, a very high [TIMP-2]*[IGFBP7] level, and an intermediate SCr level. With subphenotype A as the reference, the adjusted hazard ratio (aHR) [95%CI] for the composite outcome was 3.77 [1.92-7.42] (p < 0.001) for subphenotype B and 4.80 [1.67-13.82] (p = 0.004) for subphenotype C.

CONCLUSIONS

Combining conventional kidney function variables with urine measurements of [TIMP-2]*[IGFBP7] might help to identify distinct SA-AKI subphenotypes with different short-term courses and survival rates.

Urine cell cycle arrest biomarkers distinguish poorly between transient and persistent AKI in early septic shock: a prospective, multicenter study

Background

The urine biomarkers tissue inhibitor of metalloproteinases-2 (TIMP-2) and insulin-like growth factor-binding protein 7 (IGFBP7) have been validated for predicting and stratifying AKI. In this study, we analyzed the utility of these biomarkers for distinguishing between transient and persistent AKI in the early phase of septic shock.

Methods

We performed a prospective, multicenter study in 11 French ICUs. Patients presenting septic shock, with the development of AKI within the first 6 h, were included. Urine [TIMP-2]*[IGFBP7] was determined at inclusion (0 h), 6 h, 12 h, and 24 h. AKI was considered transient if it resolved within 3 days. Discriminative power was evaluated by receiver operating characteristic (ROC) curve analysis.

Results

We included 184 patients, within a median [IQR] time of 1.0 [0.0–3.0] h after norepinephrine (NE) initiation; 100 (54%) patients presented transient and 84 (46%) presented persistent AKI. Median [IQR] baseline urine [TIMP-2]*[IGFBP7] was higher in the persistent AKI group (2.21 [0.81–4.90] (ng/ml)²/1000) than in the transient AKI group (0.75 [0.20–2.12] (ng/ml)²/1000; p < 0.001). Baseline urine [TIMP-2]*[IGFBP7] was poorly discriminant, with an AUROC [95% CI] of 0.67 [0.59–0.73]. The clinical prediction model combining baseline serum creatinine concentration, baseline urine output, baseline NE dose, and baseline extrarenal SOFA performed well for the prediction of persistent AKI, with an AUROC [95% CI] of 0.81 [0.74–0.86]. The addition of urine [TIMP-2]*[IGFBP7] to this model did not improve the predictive performance.

Conclusions

Urine [TIMP-2]*[IGFBP7] measurements in the early phase of septic shock discriminate poorly between transient and persistent AKI and do not improve clinical prediction over that achieved with the usual variables.

Trial registration

NCT02812784

Value and determinants of the mean systemic filling pressure in critically ill patients

Mean systemic filling pressure (Pmsf) is a major determinant of venous return. Its value is unknown in critically ill patients (ICU). Our objectives were to report Pmsf in critically ill patients and to look for its clinical determinants, if any. We performed a prospective study in 202 patients who died in the ICU with a central venous and/or arterial catheter. One minute after the heart stopped beating, intravascular pressures were recorded in the supine position after ventilator disconnection. Parameters at admission, during the ICU stay, and at the time of death were prospectively collected. One-minute Pmsf was 12.8 ± 5.6 mmHg. It did not differ according to gender, severity score, diagnosis at admission, fluid balance, need for and duration of mechanical ventilation, or length of stay. Nor was there any difference according to suspected cause of death, classified as shock (cardiogenic, septic, and hemorrhagic) and nonshock, although a large variability of values was observed. The presence of norepinephrine at the time of death (102 patients) was associated with a higher 1-min Pmsf (14 ± 6 vs. 11.4 ± 4.5 mmHg), whereas the decision to forgo life-sustaining therapy (34 patients) was associated with a lower 1-min Pmsf (10.9 ± 3.8 vs. 13.1 ± 5.3 mmHg). In a multiple-regression analysis, norepinephrine (β = 2.67, P = 0.0004) and age (β = -0.061, P = 0.022) were associated with 1-min Pmsf. One-minute Pmsf appeared highly variable without any difference according to the kind of shock and fluid balance, but was higher with norepinephrine.

Therapeutic hypothermia after nonshockable cardiac arrest: the HYPERION multicenter, randomized, controlled, assessor-blinded, superiority trial

BACKGROUND

Meta-analyses of nonrandomized studies have provided conflicting data on therapeutic hypothermia, or targeted temperature management (TTM), at 33°C in patients successfully resuscitated after nonshockable cardiac arrest. Nevertheless, the latest recommendations issued by the International Liaison Committee on Resuscitation and by the European Resuscitation Council recommend therapeutic hypothermia. New data are available on the adverse effects of therapeutic hypothermia, notably infectious complications. The risk/benefit ratio of therapeutic hypothermia after nonshockable cardiac arrest is unclear.

METHODS

HYPERION is a multicenter (22 French ICUs) trial with blinded outcome assessment in which 584 patients with successfully resuscitated nonshockable cardiac arrest are allocated at random to either TTM between 32.5 and 33.5°C (therapeutic hypothermia) or TTM between 36.5 and 37.5°C (therapeutic normothermia) for 24 hours. Both groups are managed with therapeutic normothermia for the next 24 hours. TTM is achieved using locally available equipment. The primary outcome is day-90 neurological status assessed by the Cerebral Performance Categories (CPC) Scale with dichotomization of the results (1 + 2 versus 3 + 4 + 5). The primary outcome is assessed by a blinded psychologist during a semi-structured telephone interview of the patient or next of kin. Secondary outcomes are day-90 mortality, hospital mortality, severe adverse events, infections, and neurocognitive performance. The planned sample size of 584 patients will enable us to detect a 9% absolute difference in day-90 neurological status with 80% power, assuming a 14% event rate in the control group and a two-sided Type 1 error rate of 4.9%. Two interim analyses will be performed, after inclusion of 200 and 400 patients, respectively.

DISCUSSION

The HYPERION trial is a multicenter, randomized, controlled, assessor-blinded, superiority trial that may provide an answer to an issue of everyday relevance, namely, whether TTM is beneficial in comatose patients resuscitated after nonshockable cardiac arrest. Furthermore, it will provide new data on the tolerance and adverse events (especially infectious complications) of TTM at 32.5-33.5°C.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01994772 .

Prospective assessment of a score for assessing basic critical-care transthoracic echocardiography skills in ventilated critically ill patients

Background

We studied a score for assessing basic transthoracic echocardiography (TTE) skills exhibited by residents who examined critically ill patients receiving mechanical ventilation.

Methods

We conducted a prospective study in the 16 residents who worked in our medical-surgical ICU between 1 May 2008 and 1 November 2009. The residents received theoretical teaching (two hours) then performed supervised TTEs during their six-month rotation. Their basic TTE skills in mechanically ventilated patients were evaluated after one (M1), three (M3), and six (M6) months by two experts, who used a scoring system devised for the study. After scoring, residents gave their hemodynamic diagnosis and suggested a treatment.

Results

The 4 residents with previous TTE skills obtained a significantly higher total score than did the 12 novices at M1 (18 (16 to 19) versus 13 (10 to 15), respectively, P = 0.03). In the novices, the total score increased significantly during training (M1, 13 (10 to 14); M3, 15 (12 to 16); and M6, 17 (15 to 18); P < 0.001) and correlated significantly with the number of supervised TTEs (r = 0.68, P < 0.0001). In the overall population, agreement with experts regarding the diagnosis and treatment was associated with a significantly higher total score (17 (16 to 18) versus 13 (12 to 16), P = 0.002). A total score ≥ 19/20 points had 100% specificity (95% confidence interval, 79 to 100%) for full agreement with the experts regarding the diagnosis and treatment.

Conclusions

Our results validate the scoring system developed for our study of the assessment of basic critical-care TTE skills in residents.

Pulse pressure variations to guide fluid therapy in donors: a multicentric echocardiographic observational study

PURPOSE

Preload responsiveness parameters could be useful in the hemodynamic management of septic shock.

METHODS

A multicentric prospective echocardiographic observational study was conducted from March 2009 to August 2011. Clinically brain-dead subjects were included. Pulse pressure variations (ΔPPs) were recorded. Cardiac index, variation of the maximum flow velocity of aortic systolic blood flow, and right ventricular function parameters were evaluated via transthoracic echocardiography. Fluid responsiveness was defined by at least 15% cardiac index increase, 30 minutes after a 500-mL colloid solution infusion. The number of organs harvested was recorded.

RESULTS

Twenty-five subjects were included. Pulse pressure variation could not discriminate responders (n=15) from nonresponders (n=10). The best ΔPP threshold (20%) could discriminate responders with a sensitivity of 100% and a specificity of 40%. Variation of the maximum flow velocity of aortic systolic blood flow, tricuspid annular plane systolic excursion, and right ventricle dilation could not discriminate responders from nonresponders. Eighteen subjects underwent organ harvesting. The number of organs harvested was higher in responders (3.5 [3-5]) than in nonresponders (2.5 [2-3]; P=.03).

CONCLUSIONS

A ΔPP threshold of 13% is insufficient to guide volume expansion in donors. The best threshold is 20%. Fluid responsiveness monitoring could enhance organ harvesting.

Echocardiography: a help in the weaning process

Introduction

To evaluate the ability of transthoracic echocardiography (TTE) to detect the effects of spontaneous breathing trial (SBT) on central hemodynamics and to identify indices predictive of cardiac-related weaning failure.

Methods

TTE was performed just before and at the end of a 30-min SBT in 117 patients fulfilling weaning criteria. Maximal velocities of mitral E and A waves, deceleration time of E wave (DTE), maximal velocity of E' wave (tissue Doppler at the lateral mitral annulus), and left ventricular (LV) stroke volume were measured. Values of TTE parameters were compared between baseline (pressure support ventilation) and SBT in all patients and according to LV ejection fraction (EF): >50% (n = 58), 35% to 50% (n = 30), and <35% (n = 29). Baseline TTE indices were also compared between patients who were weaned (n = 94) and those who failed (n = 23).

Results

Weaning failure was of cardiac origin in 20/23 patients (87%). SBT resulted in a significant increase in cardiac output and E/A, and a shortened DTE. At baseline, DTE was significantly shorter in patients with LVEF <35% when compared to other subgroups (median [25^th-75^th percentiles]: 119 ms [90-153]; vs. 187 ms [144-224] vs. 174 ms [152-193]; P < 0.01) and E/E' was greater (7.9 [5.4-9.1] vs. 6.0 [5.3-9.0] vs. 5.2 [4.7-6.0]; P < 0.01). When compared to patients who were successfully weaned, those patients who failed exhibited at baseline a significantly lower LVEF (36% [27-55] vs. 51% [43-55]: P = 0.04) and higher E/E' (7.0 [5.0-9.2] vs. 5.6 [5.2-6.3]: P = 0.04).

Conclusions

TTE detects SBT-induced changes in central hemodynamics. When performed by an experienced operator prior to SBT, TTE helps in identifying patients at high risk of cardiac-related weaning failure when documenting a depressed LVEF, shortened DTE and increased E/E'. Further studies are needed to evaluate the impact of this screening strategy on the weaning process and patient outcome.

Reversal of refractory septic shock with drotrecogin alpha (activated)

OBJECTIVE

We previously reported that early continuous veno-venous hemodiafiltration (CVVHDF) enables rapid identification of a subgroup of patients with "refractory" septic shock and a 100% risk of death. The objective of this study was to investigate whether early administration of drotrecogin alpha (activated) (DrotAA) to this selected subgroup of septic patients at extremely high risk of death would significantly improve prognosis.

METHOD

Prospective observational study in a medical intensive-care unit of a University Hospital. Twenty-three patients with refractory septic shock were included. "Refractory" shock was defined as persistent circulatory failure despite adequate circulatory support, associated with persisting lactic acidosis despite early CVVHDF. Response to CVVDHF was assessed after 6 h of this continuous procedure. Patients selected by this strategy received DrotAA infusion for four days.

RESULTS

The 28-day mortality rate of the 23 patients was 39%. No difference was observed at inclusion between survivors and nonsurvivors. In patients who finally survived, 12 h of DrotAA infusion was associated with a significant decrease in lactic acidosis and in norepinephrine dose.

CONCLUSION

DrotAA therapy was associated with unexpectedly high 28-day survival in patients with "refractory" septic shock.

Efficacy of therapeutic hypothermia after out-of-hospital cardiac arrest due to ventricular fibrillation

AIM OF THE STUDY

We investigated implementation and efficacy of mild therapeutic hypothermia in the treatment of out-of-hospital cardiac arrest due to ventricular fibrillation.

MATERIALS AND METHODS

Two periods were compared, an historical one (36 patients) between 2000 and 2002 where therapeutic hypothermia was never used, and a recent period (32 patients) between 2003 and 2005 where therapeutic hypothermia (32-34 degrees C) was implemented prospectively in our unit. Cooling was obtained by simply using wet cloths and ice packs. Survival in the two groups and factors associated with survival were analysed, together with the neurological prognosis in discharged patients.

RESULTS

Survival was significantly higher in the hypothermia group (56% versus 36%), whereas no significant difference was observed in severity between the two periods. Only age, time from return to spontaneous circulation <20min, and therapeutic hypothermia were independently associated with survival. Therapeutic hypothermia was well tolerated and was associated with a significant improvement in neurological outcome. Whereas only 23% of patients actually reached the target temperature in 2003, 100% did in 2005.

CONCLUSION

Therapeutic hypothermia is efficient in significantly improving survival and neurological outcome of out-of-hospital cardiac arrest with ventricular fibrillation. By using a simple method, it can be implemented easily and quickly, without side effects.

Prone positioning unloads the right ventricle in severe ARDS

BACKGROUND

Despite airway pressure limitation, acute cor pulmonale persists in a minority of ARDS patients. Insufficient airway pressure limitation, hypercapnia, or both may be responsible. Because prone positioning (PP) has been shown to be a safe way to reduce airway pressure and to improve alveolar ventilation, we decided to assess its effect on right ventricular (RV) pressure overload in ARDS patients.

METHODS

Between January 1998 and December 2006, we studied 42 ARDS patients treated by PP to correct severe oxygenation impairment (Pao2/fraction of inspired oxygen ratio, <100 mm Hg). RV function was evaluated by bedside transesophageal echocardiography, before and after 18 h of prone-position ventilation. RV enlargement was measured by RV/left ventricular (LV) end-diastolic area ratio in the long axis. Septal dyskinesia was quantified by measuring short-axis systolic eccentricity of the LV.

RESULTS

Before PP, 21 patients (50%) had acute cor pulmonale, defined by RV enlargement associated with septal dyskinesia (group 1), whereas 21 patients had a normal RV (group 2). PP was accompanied by a significant decrease in airway pressure and Paco2. In group 1, this produced a significant decrease in mean (+/-SD) RV enlargement (from 0.91+/-0.22 to 0.61+/-0.21) after 18 h of PP (p=0.000) and a significant reduction in mean septal dyskinesia (from 1.5+/-0.2 to 1.1+/-0.1) after 18 h of PP (p=0.000).

CONCLUSION

In the most severe forms of ARDS, PP was an efficient means of controlling RV pressure overload.

Validation of a skills assessment scoring system for transesophageal echocardiographic monitoring of hemodynamics

OBJECTIVE

Transesophageal echocardiography (TEE) is increasingly used in hemodynamic monitoring in the intensive care unit. This paper describes and validates a scoring system for assessing competence in TEE performed by intensivists for this indication.

DESIGN

Prospective study over an 18-month period.

SETTINGS

Two medical intensive care units.

METHODS

The scoring system is used to assess four aspects of TEE: quality of the views (score out of 14); semiquantitative evaluation of respiratory variations in the superior vena cava, valve regurgitation, size of the right ventricle (score out of 10); accuracy of measurement of velocity-time integrals for pulmonary and aortic flow, peak velocity of the E and A waves of mitral flow, left ventricular fractional area change (score out of 8); summary and proposed treatment (score out of 8). The scoring system was validated by using it to assess intensivists after 1 month (M1), 3 months (M3) and 6 months (M6) of training. TEE was done on a mechanically ventilated, hypotensive patient and scored by comparing the intensivist's examination with that of the expert examiner. The intensivists were divided into two groups of theoretical expertise at the start of training.

RESULTS

Nineteen intensivists were evaluated. The scores at M1 for level 0 (no experience in echocardiography) and level 1 (previous experience) were, respectively, 18.5 +/- 4 and 24.7 +/- 5. The scores at M1, M3, and M6 were, respectively, 20.4 +/- 5, 30.4 +/- 5 and 35.7 +/- 3. At M6, the intensivists had performed TEE 29 +/- 10 times.

CONCLUSION

The scoring system was discriminatory and sensitive to change, and could be used as a tool to assess an intensivist's mastery of TEE.

Genes required for osmoregulation and apical secretion in Caenorhabditis elegans

Few studies have investigated whether or not there is an interdependence between osmoregulation and vesicular trafficking. We previously showed that in Caenorhabditis elegans che-14 mutations affect osmoregulation, cuticle secretion, and sensory organ development. We report the identification of seven lethal mutations displaying che-14-like phenotypes, which define four new genes, rdy-1-rdy-4 (rod-like larval lethality and dye-filling defective). rdy-1, rdy-2, and rdy-4 mutations affect excretory canal function and cuticle formation. Moreover, rdy-1 and rdy-2 mutations reduce the amount of matrix material normally secreted by sheath cells in the amphid channel. In contrast, rdy-3 mutants have short cystic excretory canals, suggesting that it acts in a different process. rdy-1 encodes the vacuolar H+-ATPase a-subunit VHA-5, whereas rdy-2 encodes a new tetraspan protein. We suggest that RDY-1/VHA-5 acts upstream of RDY-2 and CHE-14 in some tissues, since it is required for their delivery to the epidermal, but not the amphid sheath, apical plasma membrane. Hence, the RDY-1/VHA-5 trafficking function appears essential in some cells and its proton pump function essential in others. Finally, we show that RDY-1/VHA-5 distribution changes prior to molting in parallel with that of actin microfilaments and propose a model for molting whereby actin provides a spatial cue for secretion.

[Circulatory failures]

To treat circulatory failures and recognize their mechanisms, we need to understand circulatory physiology. What determines systemic venous return? How does the right ventricle feed the pulmonary circulation? Where is the left ventricular preload reserve located? Four types of circulatory failure are conventionally recognized: hypovolemic, obstructive, vasoplegic and cardiogenic. One or more of these mechanisms may account for circulatory failure in septic shock. Treatment of circulatory failure requires admission to a specialized unit and continuous or discontinuous hemodynamic monitoring. Prognosis is highly dependent on rapid treatment and correction of circulatory impairment.

Effet de la fluvastatine sur l'expression du CMH de classe I par les cellules endothéliales humaines

Originally designed to target elevated lipids, the "traditional" cause of atherosclerosis, statins might also confer vascular benefit by directly or indirectly modulating both the inflammatory and immune responses. Statins have been shown to downregulate MHC class II and CD40 expression on activated endothelial cells (EC). In this study, we investigate the potential effect of statins on MHC class I expression and regulation in response to IFNgamma. Primary cultures of human ECs have been treated with increasing doses of fluvastatin (0.01; 0.1 and 1 microM) with or without IFNgamma for 48 hours. Surface expression of MHC class I and class II has been analyzed by flow cytometry. Our data indicate that fluvastatin increases MHC class I expression on quiescent ECs by a dose-dependent effect. Furthermore, fluvastatin potentiates the MHC class I upregulation but prevents MHC class II induction triggered by IFNgamma. These effects are reversed by mevalonate. In conclusion, our results suggest that while decreasing MHC class II expression, fluvastatin (at 0.1 and 1 microM) upregulates MHC class I expression on ECs. Functional consequences of statin-mediated modulation of MHC on ECs have still to be elucidated in vitro and in vivo.

The binding affinity of double-stranded RNA motifs to HIV-1 Tat protein affects transactivation and the neutralizing capacity of anti-Tat antibodies elicited after intranasal immunization

In this study we examined the hypothesis that the binding affinity of two double-stranded (ds) RNA motifs to HIV-1 Tat protein might affect transactivation and the type of anti-Tat immune responses. Using surface plasmon resonance technology we demonstrated the capacity of the poly(A):poly(U) (pA:pU) motif to bind with high affinity to a totally synthetic Tat protein and to inhibit more efficiently the Tat/transactivation response element (TAR) RNA interaction as compared to the poly(I):poly(C) (pI:pC) motif. Furthermore, the pA:pU motif was tenfold more effective in inhibiting Tat-driven transactivation than the pI:pC motif. Following intranasal immunization of mice, both dsRNA motifs enhanced the antibody (serum and mucosal) and cellular responses to Tat. However, only the serum samples of mice immunized with Tat + pI:pC inhibited Tat-driven transactivation. The profile of serum antibody subclasses together with the secreted cytokines by Tat-stimulated splenocyte cultures indicated that both dsRNA motifs favored the induction of a balanced Th1 and Th2 immune response. The demonstration in this study that two dsRNA motifs had a marked effect on Tat/TAR RNA interaction and on the neutralizing capacity of anti-Tat specific antibody responses highlights their potential for biological applications and the importance of selecting the appropriate motif as an adjuvant for vaccine design.

Tat-neutralizing versus Tat-protecting antibodies in rhesus macaques vaccinated with Tat peptides

The human immunodeficiency virus (HIV) regulatory protein Tat represents an attractive target for developing vaccine strategies. Both humoral and cellular responses against Tat might reduce disease progression by interfering with the deleterious functions of extracellularly secreted protein and by reducing viral replication. We have immunized Rhesus macaques intramuscularly and intranasally with a cocktail of three Tat peptides encompassing residues 1-20, 1-61 and 44-61 administrated in the presence of Montanide ISA 720 as adjuvant. The monkeys were challenged by the intrarectal route with 10 MID50 of SHIV BX08. All immunized macaques but one gave a good cross-reactive antibody response to Tat but the proliferative response and levels of IL-2, IFN-gamma and TNF-alpha secretion of peripheral blood mononuclear cells (PBMCs) recalled ex vivo with active Tat protein were weak. After viral challenge one peptide-vaccinated macaque only remained free of virus. The presence in the serum of vaccinated animals of neutralizing antibodies able to inhibit Tat transactivation activity or Tat-induced apoptosis was not correlated to protection.

Important B-cell epitopes for neutralization of human immunodeficiency virus type 1 Tat in serum samples of humans and different animal species immunized with Tat protein or peptides

The Tat regulatory protein of human immunodeficiency virus type 1 (HIV-1) is secreted by infected cells and plays a key role in viral pathogenesis and replication. Tat protein has been proposed as a target antigen for vaccine design since anti-Tat antibodies may interfere with virus spread and disease progression. The aim of this study was to analyse the serum antibody response of mice, rabbits, macaques and humans immunized with recombinant Tat, synthetic Tat, Tat toxoid or Tat peptides and to examine the biological properties of these antibodies in terms of Tat-induced transactivation and HIV-1 replication. Only sera with antibody specificity to both N-terminal and basic functional domains were able to inhibit extracellular Tat-dependent transactivation significantly in vitro. Antibodies from a human subject immunized with Tat also reduced HIV-1 replication in acutely infected T cells and blocked reactivation of virus replicating low levels in chronically infected cells by exogenous Tat. These results demonstrate that immunization with Tat protein or a combination of synthetic Tat peptides elicits the production of Tat-neutralizing serum antibodies and suggest that Tat vaccination could be used to block in vivo extracellular Tat autocrine/paracrine transactivation of HIV-1 replication.

Specificity and effect on apoptosis of Tat antibodies from vaccinated and SHIV-infected rhesus macaques and HIV-infected individuals

Recent contributions have demonstrated that actively secreted Tat protein plays an important functional role in human immunodeficiency virus-1 (HIV-1) infection and that Tat antibodies might interfere with disease progression by blocking the protein extracellularly. In this context we have studied the recognition of several Tat mutants as well as various synthetic Tat fragments by anti-Tat monoclonal antibodies and by IgG antibodies from a large collection of slow and fast-progressor infected individuals. We have also tested the sera from simian/human immunodeficiency virus (SHIV)-infected macaques with these Tat peptides. Important differences were found between long-term non-progressors and fast-progressors, and between human and monkey sera in terms of antibody specificity. Rabbits and macaques were immunised with several Tat peptides and we found that certain antibody subsets from immunised animals recognised the cognate protein Tat and had the capacity to inhibit Tat-induced apoptosis of T cells. Such antibodies might be important for controlling Tat-induced death in cells uninfected by HIV-1.

Immunity under the skin: potential application for topical delivery of vaccines

With the technological advances in biomedical sciences and the better understanding of how the immune system works, new immunisation strategies and vaccine delivery options, such sprays, patches, and edible formulations have been developed. This has opened up the possibility of administering vaccines without the use of needles and syringes. Already topical immunisation is a reality and it has the potential to make vaccine delivery more equitable, safer, and efficient. Furthermore, it would increase the rate of vaccine compliance and greatly facilitate the successful implementation of worldwide mass vaccination campaigns against infectious diseases. This review gives a brief account of the latest developments of application of candidate vaccine antigens onto bare skin and describes some of our recent observations using peptide and glycoconjugate vaccines as immunogens.

Increased sterol biosynthesis in tobacco calli resistant to a triazole herbicide which inhibits demethylation of 14α-methyl sterols

The γ-keto triazole derivative 4,4-dimethyl-1-(2-methoxyphenyl)-1-(1,2,4-triazol-1-yl)-1-penten-3-one is toxic to Nicotiana tabacum L. cv. Xanthi plants or cell cultures. Analysis of the sterol composition of treated wild-type plant material demonstrates that this herbicide is an inhibitor of the C-14α-methyl demethylation process in sterol biosynthesis. Selection experiments, consisting of screening large populations of microcalli derived from UV-mutagenized tobacco protoplasts for resistance to a lethal dose (1 mg · 1(-1)) of the γ-keto triazole, have resulted in the recovery of two groups of resistant calli. In the first group, selected calli show a sterol composition in the absence or presence of the inhibitor very similar to that of wild-type sensitive calli, whereas in the second group the main feature of the selected calli is a new sterol profile. These calli present an overproduction of sterols with a concomitant esterification of overproduced metaolites, just as it was demonstrated for calli previously selected in our laboratory for resistance to LAB 170250F, a triazole fungicide (Maillot-Vernier et al., 1991, Mol. Gen. Genet. 231, 33-40).

Genetic study and further biochemical characterization of a tobacco mutant that overproduces sterols

A genetic and biochemical characterization is presented of a tobacco mutant that was previously shown to have an increased sterol content with an accumulation of biosynthetic intermediates. We first show that a precise regulation of the membrane sterol composition occurs in this mutant, via a selective esterification process. Indeed, sterols representing the usual end-products of the biosynthetic pathway are preferably integrated into the membranes as free sterols, whereas most of the intermediates pool is esterified and stored in cytoplasmic lipid droplets. It is further demonstrated that overproduction of sterols by the LAB1-4 mutant is due to a single nuclear and semi-dominant mutation. Finally, increase of biosynthesis and esterification of unusual sterols are shown to be responsible for the resistance of LAB1-4 calli to LAB170 250F, the triazole pesticide used to select this mutant. However, differentiated LAB1-4 tissues do not express the resistance trait, suggesting that sterol biosynthesis might not be the only site of action for the triazole at the plant level.

In Vitro Selection of Calli Resistant to a Triazole Cytochrome-P-450-Obtusifoliol-14-Demethylase Inhibitor from Protoplasts of Nicotiana tabacum L. cv Xanthi

The selection of biochemical mutants has been undertaken in order to elucidate regulatory and functional aspects of sterol biosynthesis in plants. 2-(4-Chlorophenyl)-3-phenyl-1-(1H-1,2,4- triazol-1-yl)-2,3-oxidopropane (LAB170250F), an experimental fungicide of the triazole family, was used as a selective agent. Indeed, this compound is a strong inhibitor of the cytochrome-P-450-obtusifoliol-14-demethylase in sterol biosynthesis. The selection strategy consisted of screening large populations of microcalli derived from ultraviolet-mutagenized protoplasts of Nicotiana tabacum L. cv Xanthi for resistance to a lethal concentration of LAB170250F. The best selective conditions were first determined, i.e. strength of the selection pressure as well as the time and duration of its application in the developmental process from protoplast to whole plant. Selection experiments resulted in the recovery of 40 resistant calli. These calli were divided into three classes according to the modification of their sterol content in response to LAB170250F. Some of these calli might be impaired in sterol biosynthesis, but most have a sterol profile identical to that of the control calli. This suggests that the toxic properties of LAB170250F are due to the parallel inhibition of sterol biosynthesis and of at least one additional unidentified target in the plant cell.

The steady-state level of potato sucrose synthase mRNA is dependent on wounding, anaerobiosis and sucrose concentration

The steady-state level of potato sucrose synthase (SSase) mRNA was investigated in different plant organs and in response to certain stimuli. SSase mRNA is mainly present in developing tubers, but its presence is not restricted to this organ and the transcript is found at detectable levels in all the tissues analysed, except leaves. Wounding results in a decrease in SSase mRNA, but this can be overcome by incubation under anaerobic conditions. In leaves and petioles, an increase in sucrose concentration leads to an increase in SSase mRNA.

Biochemical characterization of a sterol mutant plant regenerated from a tobacco callus resistant to a triazole cytochrome-P-450-obtusifoliol-14-demethylase inhibitor

We report here, for the first time, the biochemical characterization of a plant mutant impaired in sterol biosynthesis. A fertile plant was regenerated from a tobacco callus resistant to LAB170250F, a potent inhibitor of the cytochrome-P450-obtusifoliol-14-demthylase. The resistant callus and the leaves from the regenerated plant are characterized by profound qualitative and quantitative changes in their sterol content. Self-fertilization of this plant yielded seeds with the same biochemical features, indicating that the new phenotype is of mutational origin.

Molecular cloning and sequencing of sucrose synthase cDNA from potato (Solanum tuberosum L.): preliminary characterization of sucrose synthase mRNA distribution

A cDNA library constructed from poly(A)+ RNA from potato tuber in lambda gt11 was screened for sucrose synthase using a maize sucrose synthase cDNA probe. The longest 2.7-kb insert was sequenced. An ATG located within the sequence CTGCAATGG starts an open reading frame of 805 codons. The nucleotide sequence, when compared to the maize sucrose synthase cDNA sequence, exhibits about 70% identity and the deduced amino acid sequence about 75%. Three amino acid regions are about 90% homologous and two of them could be important for the protein function. Expression studies show that transcription of the potato sucrose synthase gene is at least ten fold higher in tubers compared to photosynthetically active tissues.