The arginine-552-cysteine (R1315C) mutation within the A1 loop of von Willebrand factor induces an abnormal folding with a loss of function resulting in type 2A-like phenotype of von Willebrand disease: study of 10 patients and mutated recombinant von Willebrand factor

The study identified 10 patients from 6 families with prolonged bleeding time, decreased von Willebrand factor (vWF) ristocetin cofactor activity (RCoF) to vWF:Ag (antigen) ratio, and reduced ristocetin-induced platelet agglutination as well as ristocetin- or botrocetin-induced binding of plasma vWF to platelet glycoprotein Ib (GpIb). In addition, all patients showed a decrease of intermediate-molecular-weight (intermediate-MW) and high-molecular-weight (HMW) multimers of vWF. In the heterozygous state, a cysteine-to-threonine (C --> T) transversion was detected at nucleotide 4193 of the VWF gene of all patients and lead to the arginine (R)522C substitution in the A1 loop of vWF mature subunit (R1315C in the preprovWF). By in vitro mutagenesis of full-length complementary DNA (cDNA) of vWF and transient expression in COS-7 cells, the mutated C552 recombinant vWF (C552rvWF) was found to exhibit decreased expression, abnormal folding, and lack of intermediate-MW and HMW multimers. In addition, direct binding of botrocetin to C552rvWF, as well as ristocetin- and botrocetin-induced binding of C552rvWF to GpIb, was markedly decreased. Although being localized in an area of the A1 loop of vWF where most of the type 2B mutations that induce a gain-of-function have been identified, the R552C mutation induces a 2A-like phenotype with a decrease of intermediate-MW and HMW multimers as well as a loss-of-function of vWF in the presence of either ristocetin or botrocetin. (Blood. 2001;97:952-959)     

Discrepancy between IIA phenotype and IIB genotype in a patient with a variant of von Willebrand disease

Type IIA and IIB von Willebrand disease (vWD) result from qualitative abnormalities of von Willebrand factor (vWF) characterized by an absence in plasma of high molecular weight vWF multimers and an abnormal reactivity of vWF towards platelet glycoprotein (GP) Ib, which is decreased in type IIA and increased in type IIB. In this report, we describe the case of a patient having a IIA vWD phenotype associated with an intermittent thrombocytopenia atypical in this subtype but observed in type IIB vWD. The patient plasma vWF showed an absence of high molecular weight and intermediate multimers and had a decreased binding capacity to GPIb. The affinity of botrocetin was normal for plasma vWF from the propositus. Analysis of the propositus vWF gene showed the presence of a substitution Val 551 to Phe of the mature vWF subunit. This mutation is localized within a 509-695 disulphide loop of the vWF that plays an important role in the binding to GPIb and is where most of the molecular defects described so far were associated with type-IIB vWD. We have reproduced the Val 551 Phe substitution onto the vWF cDNA, expressed it in COS-7 cells, and performed structural and functional analysis of the mutant recombinant protein (rvWFPhe 551). The rvWFPhe 551 had a normal multimeric structure and showed the capacity to spontaneously interact with GPIb. Botrocetin had a decreased affinity for rvWFPhe 551. In conclusion, the Val 551 Phe mutation modifies the affinity of vWF for platelet GPIb, as does a type IIB mutation, and may be responsible for the thrombocytopenia of the patient and the clearance of the high molecular weight and intermediate- sized multimers of vWF from the plasma. The study of the rvWFPhe 551 has confirmed the discrepancy between the IIA phenotype and the IIB genotype of the patient.     

A Randomized,Placebo-Controlled Trial Evaluating Safety and Immunogenicity of the Killed,Bivalent, Whole-Cell Oral Cholera Vaccine in Ethiopia

Killed whole-cell oral cholera vaccine (OCV) has been a key component of a comprehensive package including water and sanitation measures for recent cholera epidemics. The vaccine, given in a two-dose regimen, has been evaluated in a large number of human volunteers in India, Vietnam, and Bangladesh, where it has demonstrated safety, immunogenicity, and clinical efficacy. We conducted a double-blind randomized placebo-controlled trial in Ethiopia, where we evaluated the safety and immunogenicity of the vaccine in 216 healthy adults and children. OCV was found to be safe and elicited a robust immunological response against Vibrio cholerae O1, with 81% adults and 77% children demonstrating seroconversion 14 days after the second dose of vaccine. This is the first study to evaluate safety and immunogenicity of the vaccine in a population outside Asia using a placebo-controlled, double-blind, randomized study design.     

HIV and tuberculosis coinfection in the southern region of Ethiopia: a prospective epidemiological study

HIV has played a key role in TB, modifying its incidence and clinical presentation. This study describes the prevalence of HIV among TB patients attending health facilities in the southern region of Ethiopia. The HIV prevalence was 18% for female and 21% for male TB patients. 15% and 30%, respectively, of the rural and urban patients with TB were HIV positive (p<0.05). 19% (51/261) smear-positive PTB, 26% (36/137) smear-negative PTB and 11% (10/94) of the extrapulmonary TB patients were HIV positive. The proportion of patients with extra-PTB varied from 11% to 38% across the centres and was highest in the zones with the lowest HIV prevalence. In the light of limited diagnostic facilities, clinicians often make a clinical diagnosis of TB without laboratory confirmation. The increase in the number of TB cases could be due to HIV. However, the number of health facilities offering TB treatment in the area also increased (from 53 to 236) during the same period and the increase in TB is likely to be the result of a combination of factors, including improved detection and HIV. It is important to consider this multi-factorial phenomenon when interpreting the increase of TB in a geographical area.     

Effects of Melatonin on Ischemia and Reperfusion Injury of the Rat Heart

Effects of melatonin on various manifestations of ischemia/reperfusion injury of the isolated perfused rat heart were examined. Ischemia- and reperfusion-induced ventricular arrhythmias were studied under constant flow in hearts subjected to 10, 15 or 25 min of regional ischemia (induced by LAD coronary artery occlusion) and 10-min reperfusion. Melatonin was added to the perfusion medium 5 min before ischemia at concentrations of 10 mol/l or 10 nmol/l and was present throughout the experiment. Recovery of the contractile function was evaluated under constant perfusion pressure after 20-min global ischemia followed by 40-min reperfusion. Hearts were treated with melatonin at a high concentration (10 mol/l) either 5 min before ischemia only (M1) or 5 min before ischemia and during reperfusion (M2) or only during reperfusion (M3). At the high concentration, melatonin significantly reduced the incidence of reperfusion-induced ventricular fibrillation and decreased arrhythmia score (10% and 2.2 ± 0.3, respectively) as compared with the corresponding untreated group (62% and 4.1 ± 0.3, respectively); the low concentration had no effect. This substance did not affect the incidence and severity of ischemic arrhythmias. Melatonin (M2, M3) significantly improved the recovery of the contractile function as compared with the untreated group; this protection did not appear if melatonin was absent in the medium during reperfusion (M1). Our results show that melatonin, in accordance with its potent antioxidant properties, effectively protects the rat heart against injury associated with reperfusion. It appears unlikely that melatonin is cardioprotective at physiological concentrations.