Interaction between drug and placebo effects: a cross-over balanced placebo design trial

<p>Abstract</p> <p>Background</p> <p>The total effect of a medication is the sum of its drug effect, placebo effect (meaning response), and their possible interaction. Current interpretation of clinical trials' results assumes no interaction. Demonstrating such an interaction has been difficult due to lack of an appropriate study design.</p> <p>Methods</p> <p>180 adults were randomized to caffeine (300 mg) or placebo groups. Each group received the assigned intervention described by the investigators as caffeine or placebo, in a randomized crossover design. 4-hour-area-under-the-curve of energy, sleepiness, nausea (on 100 mm visual analog scales), and systolic blood pressure levels as well as caffeine pharmacokinetics (in 22 volunteers nested in the caffeine group) were determined. Caffeine drug, placebo, placebo-plus-interaction, and total effects were estimated by comparing outcomes after, receiving caffeine described as placebo to receiving placebo described as placebo, receiving placebo described as caffeine or placebo, receiving caffeine described as caffeine or placebo, and receiving caffeine described as caffeine to receiving placebo described as placebo, respectively.</p> <p>Results</p> <p>The placebo effect on area-under-the-curve of energy (mean difference) and sleepiness (geometric mean ratio) was larger than placebo-plus-interaction effect (16.6 [95% CI, 4.1 to 29.0] vs. 8.4 [-4.2 to 21.0] mm*hr and 0.58 [0.39 to 0.86] vs. 0.69 [0.49 to 0.97], respectively), similar in size to drug effect (20.8 [3.8 to 37.8] mm*hr and 0.49 [0.30 to 0.91], respectively), and its combination with the later was larger than total caffeine effect (29.5 [11.9 to 47.1] mm*hr and 0.37 [0.22 to 0.64]). Placebo-plus-interaction effect increased caffeine terminal half-life by 0.40 [0.12 to 0.68] hr (P = 0.007).</p> <p>Conclusions</p> <p>Drug and placebo effects of a medication may be less than additive, which influences the interpretation of clinical trials. The placebo effect may increase active drug terminal half-life, a novel mechanism of placebo action.</p> <p>Trial Registration</p> <p>ClinicalTrials.gov identification number - NCT00426010.</p

Surface Co-Expression of Two Different PfEMP1 Antigens on Single Plasmodium falciparum-Infected Erythrocytes Facilitates Binding to ICAM1 and PECAM1

The Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) antigens play a major role in cytoadhesion of infected erythrocytes (IE), antigenic variation, and immunity to malaria. The current consensus on control of variant surface antigen expression is that only one PfEMP1 encoded by one var gene is expressed per cell at a time. We measured var mRNA transcript levels by real-time Q-PCR, analysed var gene transcripts by single-cell FISH and directly compared these with PfEMP1 antigen surface expression and cytoadhesion in three different antibody-selected P. falciparum 3D7 sub-lines using live confocal microscopy, flow cytometry and in vitro adhesion assays. We found that one selected parasite sub-line simultaneously expressed two different var genes as surface antigens, on single IE. Importantly, and of physiological relevance to adhesion and malaria pathogenesis, this parasite sub-line was found to bind both CD31/PECAM1 and CD54/ICAM1 and to adhere twice as efficiently to human endothelial cells, compared to infected cells having only one PfEMP1 variant on the surface. These new results on PfEMP1 antigen expression indicate that a re-evaluation of the molecular mechanisms involved in P. falciparum adhesion and of the accepted paradigm of absolutely mutually exclusive var gene transcription is required

α2-Macroglobulin can crosslink multiple plasmodium falciparum Erythrocyte Membrane Protein 1 (PfEMP1) molecules and may facilitate adhesion of parasitized erythrocytes

Rosetting, the adhesion of Plasmodium falciparum-infected erythrocytes to uninfected erythrocytes, involves clonal variants of the parasite protein P. falciparum erythrocyte membrane protein 1 (PfEMP1) and soluble serum factors. While rosetting is a well-known phenotypic marker of parasites associated with severe malaria, the reason for this association remains unclear, as do the molecular details of the interaction between the infected erythrocyte (IE) and the adhering erythrocytes. Here, we identify for the first time a single serum factor, the abundant serum protease inhibitor α2-macroglobulin (α2M), which is both required and sufficient for rosetting mediated by the PfEMP1 protein HB3VAR06 and some other rosette-mediating PfEMP1 proteins. We map the α2M binding site to the C terminal end of HB3VAR06, and demonstrate that α2M can bind at least four HB3VAR06 proteins, plausibly augmenting their combined avidity for host receptors. IgM has previously been identified as a rosette-facilitating soluble factor that acts in a similar way, but it cannot induce rosetting on its own. This is in contrast to α2M and probably due to the more limited cross-linking potential of IgM. Nevertheless, we show that IgM works synergistically with α2M and markedly lowers the concentration of α2M required for rosetting. Finally, HB3VAR06+ IEs share the capacity to bind α2M with subsets of genotypically distinct P. falciparum isolates forming rosettes in vitro and of patient parasite isolates ex vivo. Together, our results are evidence that P. falciparum parasites exploit α2M (and IgM) to expand the repertoire of host receptors available for PfEMP1-mediated IE adhesion, such as the erythrocyte carbohydrate moieties that lead to formation of rosettes. It is likely that this mechanism also affects IE adhesion to receptors on vascular endothelium. The study opens opportunities for broad-ranging immunological interventions targeting the α2M--(and IgM-) binding domains of PfEMP1, which would be independent of the host receptor specificity of clinically important PfEMP1 antigens

Liver-related morbidity and mortality in patients with chronic hepatitis C and cirrhosis with and without sustained virologic response

Sofie Hallager,1 Steen Ladelund,2 Peer Brehm Christensen,3 Mette Kj&aelig;r,4,5 Birgit Thorup Roege,6 Karin Elmegaard Gr&oslash;nb&aelig;k,7 Erika Belard,8 Toke S Barfod,9 Lone Galmstrup Madsen,10 Jan Gerstoft,11 Britta Tarp,12 Henrik Bygum Krarup,13 Nina Weis,1,5 1Department of Infectious Diseases, Copenhagen University Hospital, Hvidovre, 2Clinical Research Center, Copenhagen University Hospital, Hvidovre, 3Department of Infectious Diseases and Clinical Institute, Odense University Hospital, University of Southern Denmark, Odense, 4Department of Hepatology, Copenhagen University Hospital, Rigshospitalet, 5Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, 6Department of Internal Medicine, Kolding Hospital, Kolding, 7Department of Gastroenterology, Copenhagen University Hospital, Hvidovre, 8Department of Gastroenterology, Copenhagen University Hospital, Herlev, 9Department of Internal Medicine, Zealand University Hospital, Roskilde, 10Department of Gastroenterology, Zealand University Hospital, K&oslash;ge, 11Department of Infectious Diseases, Copenhagen University Hospital, Rigshospitalet, 12Diagnostic Centre, University Research Clinic for Innovative Patient Pathways, Silkeborg Regional Hospital, Silkeborg, 13Section of Molecular Diagnostics, Clinical Biochemistry and Department of Medical Gastroenterology, Aalborg University Hospital, Aalborg, Denmark Background: Chronic hepatitis C (CHC) causes liver cirrhosis in 5%&ndash;20% of patients, leading to increased morbidity and mortality. This study aimed to estimate liver-related morbidity and mortality among patients with CHC and cirrhosis in Denmark with and without antiviral treatment and sustained virologic response (SVR). Furthermore we aimed to estimate the rate of hepatocellular carcinoma (HCC) and decompensation associated with certain prognostic factors.Materials and methods: Patients with CHC and cirrhosis registered in the Danish Database for Hepatitis B and C were eligible. Cirrhosis was based on liver biopsy, transient elastography, and clinical cirrhosis. Data were extracted from nationwide registries. The study period was from 2002 until 2013.Results: Of 1,038 patients included, 716 (69%) were male and the median age was 52 years. Median follow-up was 3.8 years, 360 patients died, and 233 of 519 treated patients achieved SVR. Alcohol overuse and hepatitis C virus genotype 3 were associated with an increased incidence rate (IR) of HCC, whereas diabetes and alcohol overuse were associated with increased IRs of decompensation. Achieving SVR reduced all-cause mortality (adjusted mortality rate ratio 0.68 [95% CI 0.43&ndash;1.09]) and liver-related mortality (mortality rate ratio 0.6 [95% CI 0.36&ndash;1]), as well as liver-related morbidity with adjusted IR ratios of 0.37 (95% CI 0.22&ndash;0.62) for HCC and 0.31 (95% CI 0.17&ndash;0.57) for decompensation. The IRs of HCC and decompensation remained elevated in patients with alcohol overuse after SVR.Conclusion: Alcohol overuse, hepatitis C genotype 3, and diabetes were associated with liver-related morbidity in patients with CHC and cirrhosis. SVR markedly reduced liver-related morbidity and mortality; however, special attention to patients with alcohol overuse should continue after SVR. Keywords: chronic hepatitis C, cirrhosis, liver-related morbidity, cohort study, sustained virologic respons