Impact of intrapeptide epitope location on CD8 T cell recognition: implications for design of overlapping peptide panels

BACKGROUND: Antigen-specific CD8 T cells following infection or immunization are typically assessed by measuring interferon-gamma production after stimulation with overlapping peptides spanning the region of interest. The effect of epitope location within such peptides is not known but may influence recognition. OBJECTIVE: To examine if peptides containing the appropriate C-terminal anchor amino acid residue would provide more sensitive detection of T cell responses. The impact was examined of epitope location within overlapping peptides on recognition of epitope-specific CD8 T cell responses. METHODS: C-terminal amino acid residues were analyzed in well-defined optimal epitopes for HIV, Epstein-Barr virus, cytomegalovirus and influenza and in peptide-binding motifs. Recognition of known epitopes within longer synthesized peptides by peripheral blood mononuclear cells or CD8 T cell lines was tested using interferon-gamma Elispot at various peptide concentrations. RESULTS: Only 9 of 20 amino acids served as the C-terminal anchor position in 96% of described optimal epitopes and in 95% of peptide-binding motifs. A CD8 T cell response to an epitope within a longer peptide is best detected when the epitope is situated at the C-terminal end of the longer peptide, both when using peptides designed to include the optimal epitope at every possible position and when comparing responses towards optimal epitopes and corresponding overlapping peptides in a larger group of subjects. CONCLUSION: When using overlapping peptides to screen for CD8 T cell responses, more sensitive detection will be achieved using known C-terminal anchor amino acid residues at the C-terminus.     

Collateral-flow measurements in humans by myocardial contrast echocardiography: validation of coronary pressure-derived collateral-flow assessment.

AIMS: Myocardial blood flow (MBF) is the gold standard to assess myocardial blood supply and, as recently shown, can be obtained by myocardial contrast echocardiography (MCE). The aims of this human study are (i) to test whether measurements of collateral-derived MBF by MCE are feasible during elective angioplasty and (ii) to validate the concept of pressure-derived collateral-flow assessment. METHODS AND RESULTS: Thirty patients with stable coronary artery disease underwent MCE of the collateral-receiving territory during and after angioplasty of 37 stenoses. MCE perfusion analysis was successful in 32 cases. MBF during and after angioplasty varied between 0.060-0.876 mL min(-1) g(-1) (0.304+/-0.196 mL min(-1) g(-1)) and 0.676-1.773 mL min(-1) g(-1) (1.207+/-0.327 mL min(-1) g(-1)), respectively. Collateral-perfusion index (CPI) is defined as the rate of MBF during and after angioplasty varied between 0.05 and 0.67 (0.26+/-0.15). During angioplasty, simultaneous measurements of mean aortic pressure, coronary wedge pressure, and central venous pressure determined the pressure-derived collateral-flow index (CFI(p)), which varied between 0.04 and 0.61 (0.23+/-0.14). Linear-regression analysis demonstrated an excellent agreement between CFI(p) and CPI (y=0.88 x +0.01; r(2)=0.92; P<0.0001). CONCLUSION: Collateral-derived MBF measurements by MCE during angioplasty are feasible and proved that the pressure-derived CFI exactly reflects collateral relative to normal myocardial perfusion in humans.     

Distinct error-correcting and incidental learning of location relative to landmarks and boundaries

Associative reinforcement provides a powerful explanation of learned behavior. However, an unproven but long-held conjecture holds that spatial learning can occur incidentally rather than by reinforcement. Using a carefully controlled virtual-reality object-location memory task, we formally demonstrate that locations are concurrently learned relative to both local landmarks and local boundaries but that landmark-learning obeys associative reinforcement (showing "overshadowing" and "blocking" or "learned irrelevance"), whereas boundary-learning is incidental, showing neither overshadowing nor blocking nor learned irrelevance. Crucially, both types of learning occur at similar rates and do not reflect differences in levels of performance, cue salience, or instructions. These distinct types of learning likely reflect the distinct neural systems implicated in processing of landmarks and boundaries: the striatum and hippocampus, respectively [Doeller CF, King JA, Burgess N (2008) Proc Natl Acad Sci USA 105:5915-5920]. In turn, our results suggest the use of fundamentally different learning rules by these two systems, potentially explaining their differential roles in procedural and declarative memory more generally. Our results suggest a privileged role for surface geometry in determining spatial context and support the idea of a "geometric module," albeit for location rather than orientation. Finally, the demonstration that reinforcement learning applies selectively to formally equivalent aspects of task-performance supports broader consideration of two-system models in analyses of learning and decision making.     

MMP-2 in the left rat ventricle is increased by growth hormone.

In cardiac hypertrophy induced by GH, the turn-over of collagen seems to be increased. Matrix metalloproteinases (MMP) are enzymes suggested to contribute to the remodelling of the extracellular matrix in the myocardium. The aim of the present experiment was to investigate how GH influenced MMP concentration, collagen concentration, and structure of the connective tissue of the LV in young rats in relation to time. Three-month-old female rats were injected with GH (5mg/kg/day) or vehicle for 5, 10, 20, 40, or 80 days. MMPs and structural changes of the connective tissue were analysed using zymography and stereology, respectively. Wet weight of the LV was increased time-dependently by GH (r = 0.89, P < 0.001). Furthermore, GH increased the MMP-2 concentration (P < 0.01, two-way ANOVA), whereas no collagenases (MMP-1, MMP-8, or MMP-13) could be demonstrated. The increase in MMP-2 was accompanied by a time-dependent decrease in the collagen concentration (r = -0.46, P < 0.05), whereas the total collagen content (r = 0.85, P < 0.01) and total number of non-myocyte nuclei (GH: r = 0.89, P < 0.001) were time-dependently increased. These results indicate that MMP-2 may be involved in the remodelling process of the extracellular matrix in GH-induced cardiac hypertrophy.     

Obstructive sleep apnea syndrome, sleepiness, and quality of life

OBJECTIVE: To evaluate the addition of short arousals of > 3 s on indexes of sleep-disordered breathing (SDB) and subjective sleepiness in patients with obstructive sleep apnea (OSA), and to evaluate the quality of life and reported difficulty driving with arousal index and indexes of SDB. METHOD: Data was collected from a general clinical evaluation, and evaluations using the Epworth sleepiness scale (ESS), the sleep disorders questionnaire, the Beck depression inventory (BDI), the Medical Outcomes Study 36-item short form health survey (SF-36), a questionnaire on driving difficulties and accidents, and polysomnography. RESULTS: A total of 135 male subjects (mean [+/- SD] age, 52 +/- 12.1 years; mean body mass index [BMI], 27.8 +/- 5.6 kg/m(2); mean apnea-hypopnea index [AHI], 48.7 +/- 26.8 events per hour) were studied. Of these subjects, 70.4% acknowledged having driven while sleepy. ESS scores correlated significantly with the arousal index and AHI, and negatively with the lowest arterial oxygen saturation. The "physical functioning," "general health," and "role physical" subscales of the SF-36 correlated with the arousal index. No significant correlation was seen in multiple regression analyses after adjusting for age and BMI, using "reports of sleepiness while driving" as the dependent variable. CONCLUSION: Several subjective complaints and subscales of the SF-36 correlated significantly with a frequency of SDB-related arousal of > 3 s. Patients perceived that an organic health problem had been impairing their quality of life more than an emotional problem, despite elevated scores on the BDI. However, if sleepiness while driving was common in OSA patients, it was not significant. Many clinical and polysomnographic variables may be considered as possible independent variables in the regression analysis. Other unrelated factors have a greater impact. To relate sleepiness while driving only to the usually studied variables in OSA patients is an oversimplification.     

Monitoring carbon dioxide tension and arterial oxygen saturation by a single earlobe sensor in patients with critical illness or sleep apnea

OBJECTIVES: The purpose of the study was to evaluate a novel, combined sensor for transcutaneous monitoring of arterial oxygen saturation and carbon dioxide tension. DESIGN: The new monitoring technique was compared to established reference methods. SETTING: ICU and sleep laboratory of a university hospital. PATIENTS: Eighteen critically ill adult patients with acute respiratory failure or heart failure, and 12 patients with sleep apnea (mean [+/- SD] apnea/hypopnea index, 43 +/- 24 events per hour). MEASUREMENTS: Continuous measurements were performed over several hours by the novel heated (temperature, 42 degrees C) earlobe sensor (TOSCA; Linde Medical Sensors; Basel, Switzerland), incorporating electrochemical and optical elements for carbon dioxide measurement (PtcCO2) and pulse oximetry (SpO2), respectively. The data were compared to the results of repeated arterial blood gas analyses in critically ill patients and to simultaneous nocturnal pulse oximetry performed with different devices with earlobe or finger sensors in sleep apnea patients. RESULTS: In critically ill patients, the mean difference and limits of agreement (bias +/- 2 SDs) of transcutaneous PtcCO2 vs arterial PaCO2 were 3 +/- 7 mm Hg; the corresponding values for changes in PtcCO2 vs PaCO2 were 1 +/- 6 mm Hg. The bias +/- 2 SDs for pulse oximetric SpO2 vs arterial oxygen saturation (SaO2) were 1 +/- 4%. In sleep apnea patients, the combined earlobe sensor identified more transient oxygen desaturations, and the rate of change in oxygen saturation during events was greater compared to those with other tested pulse oximeters, indicating a faster response. CONCLUSIONS: Due to its ability to accurately assess both ventilation and oxygenation by a single transcutaneous sensor, the described noninvasive monitoring technique is a valuable tool for respiratory monitoring with potential applications in critical care and sleep medicine.     

Comparison of non-invasive liver fibrosis biomarkers in HIV/HCV co-infected patients: the fibrovic study--ANRS HC02

BACKGROUND/AIMS: To compare non-invasive biological liver fibrosis scores, as alternatives to liver biopsy, in HIV/HCV co-infected patients. METHODS: Two hundred and seventy-two HIV/HCV patients, nai ve for HCV treatment, underwent liver biopsy [197 (72%) men, 39.9 years, fibrosis stage (Metavir) F1 (25%), F2 (40%), F3 (25%), F4 (10%), median CD4 486/mm(3) and median HIV viral load 3.5log. Fibrotest (FT), Hepascore (HS), Fibrometer (FM), SHASTA, APRI, Forns index, and Fib-4 were tested in order to differentiate patients with mild to moderate fibrosis (F2) and those with advanced fibrosis (F3). The AUROC and the rate of well-classified patients were compared to liver biopsy. RESULTS: FT, HS, and FM were able to stage liver fibrosis in all patients with AUROCs of 0.78, 0.84 and 0.89 for the diagnosis of F2, respectively. The correlation coefficient indexes were 0.37, 0.46 and 0.48, respectively. The rates of well-classified patients were 62%, 68% and 71%, respectively. Fib-4, APRI and the Forn's index were only able to stage 37-61% of patients and showed lower accuracies. Using a combination of FT, HS and FM did not significantly increase the performance of each test. CONCLUSIONS: In HIV/HCV co-infected patients, Fibrometer, Hepascore and Fibrotest outperformed other non-invasive liver fibrosis biomarkers for the prediction of significant liver fibrosis.     

Infectious risks and outcomes after stem cell transplantation: are nonmyeloablative transplants changing the picture?

PURPOSE OF REVIEW: Opportunistic infections contribute to morbidity and mortality after myeloablative allogeneic stem cell transplantation. The development of nonmyeloablative or toxicity-reduced conditioning regimens for allogeneic hematopoietic stem cell transplantation might change this picture significantly. These regimens are in general highly immunosuppressive, but effects on myelopoiesis and mucosal toxicities are usually reduced compared with myeloablative hematopoietic stem cell transplantation conditioning regimens. This review summarizes the infectious risks associated with each type of hematopoietic stem cell transplantation conditioning regimen, and presents the results of early clinical studies. RECENT FINDINGS: Although the data are preliminary, the results of recent studies suggest that nonmyeloablative conditioning regimens may decrease the risks of bacterial infections associated with mucosal damage and persistent neutropenia; however, risks for late viral and fungal infections persist during severe graft versus host disease. Results of several case reports and series emphasize that therapeutic outcomes of infections may be improved in patients who receive nonmyeloablative conditioning regimens. SUMMARY: Infectious risks and outcomes after hematopoietic stem cell transplantation appear to be in evolution given the introduction of alternative, nonmyeloablative conditioning regimens. Although infections remain a prominent cause of transplant-related mortality, the timing and types of infections may differ. Further studies are necessary to define appropriate preventative strategies, and to determine whether patients with ongoing infections might benefit from nonmyeloablative hematopoietic stem cell transplantation.     

Change of the mechanical properties of two different balloon catheters with increasing numbers of cycles of resterilization.

An increasing number of centers are reusing PTCA catheters even though manufacturers warrant single use only. This prospective bench laboratory trial addresses the quality of PTCA balloon catheters after up to three resterilization cycles in order to determine whether a larger trial is warranted to discern whether catheters should be reused. Forty PTCA catheters from two different manufacturers (nominal diameters 1.5 and 3.0 mm) were taken from the shelf. An independent institute tested mechanical properties such as burst pressure, nominal diameter, crossing profile, and balloon surface. The crossing profile increased by 22.5%-39.2% with no additional deterioration after repeated sterilizations. The nominal diameter either increased or decreased by a maximum of 47%. In all 1.5 mm balloons, the burst pressure remained above the manufacturers' values, whereas in the 3.0 mm balloons, the value dropped below the rated burst pressure in 40%-50% of the trials. In conclusion, in both catheter types analyzed, reuse was associated with a considerably worse quality, which puts in question their routine clinical use.