Molecular and biological analysis of echovirus 9 strain isolated from a diabetic child

The full-length infectious cDNA clone was constructed and sequenced from the strain DM of echovirus 9, which was recently isolated from a 6-week-old child at the clinical onset of type 1 diabetes. Parallel with the isolate DM, the full-length infectious cDNA clone of the prototype strain echovirus 9 Barty (Barty-INF), was constructed and sequenced. Genetic relationships of the sequenced echo 9 viruses to the other members of the human enterovirus type B species were studied by phylogenetic analyses. Comparison of capsid protein sequences showed that the isolate DM was closely related to both prototype strains: Hill and Barty-INF. The only exception was the inner capsid protein VP4 where serotype specificity was not evident and the isolate DM clustered with the strain Hill and the strain Barty-INF with echovirus 30 Bastianni. Likewise, the nonstructural protein coding region, P2P3, of isolate DM was more similar to strain Hill than to strain Barty-INF. However, like echovirus 9 Barty, the isolate DM contained the RGD-motif in the carboxy terminus of capsid protein VP1. By blocking experiments using an RGD-containing peptide and a polyclonal rabbit antiserum to the alpha(v)beta(3)-integrin, it was shown that this molecule works as a cellular receptor for isolate DM. By using primary human islets, it was shown that the isolate DM is capable of infecting insulin-producing beta-cells like the corresponding prototype strains did. However, only isolate DM was clearly cytolytic for beta-cells. The infectious clones that were made allow further investigations of the molecular features responsible for the diabetogenicity of the isolate DM.     

Acidic ATP activates lymphocyte outwardly rectifying chloride channels via a novel pathway

Using whole-cell patch-clamp techniques we found that ATP activated an outwardly rectifying current in Daudi human B lymphoma cells under acidic conditions. The substitution of Cl^– for gluconate^– shifted the reversal potential, while Cl^– channel blockers, 4,4-diisothiocyanostibene-2,2-disulfonic acid (DIDS) and 9-anthracene carboxylic acid (9-AC), blocked the current, indicating that ATP induces this current by activating the outwardly rectifying chloride channel (ORCC). The effect of ATP on ORCC was mimicked by ADP, but not by other P2 receptor agonists such as ATPS (a poorly hydrolyzable analog of ATP), 2,3-O-benzoyl-4-benzoyl-ATP (BzATP), and UTP. The ATP-induced ORCC current was completely blocked by 100 M suramin (a P2 receptor antagonist), and was partially blocked by 100 M pyridoxal-phosphate-6-azophenyl-2,4-disulfonic acid tetrasodium (PPADS), which is another P2 receptor antagonist. Neither inactivation of G proteins nor elimination of extracellular Ca²⁺ affected the ATP-induced current, indicating that G protein-coupled P2Y receptors and Ca²⁺-permeable P2X receptors are not involved. Based on the pharmacological profile and the fact that acidic conditions are required for ATP to activate the ORCC, we suggest that acidic ATP activates the lymphocyte ORCC via a novel pathway, which is not associated with any previously described purinergic receptors.     

Red cell transfusion in medicine: Future challenges

Many side-effects of red blood cell transfusion have been described. They include iron-overload, as well as allo- and autoantibody formation against red cells. During storage, erythrocytes undergo complex structural and biochemical changes. It has been suggested that accelerated and/or aberrant forms of the physiological erythrocyte aging process underlie the red cell storage lesion. This storage lesion may contribute to side-effects of transfusion as endothelial damage by release of internal erythrocyte constituents, (pro)inflammatory consequences, hampered microcirculation and oxygen delivery. Understanding the process that determines the fate of red blood cells after transfusion may contribute to the prevention of side-effects after red blood cell transfusion. This should be the focus of research on red blood cell transfusion in clinical transfusion medicine.     

Metabolic polymorphisms and the micronucleus frequency in buccal epithelium of adolescents living in an urban environment

Micronuclei and other biomarkers were evaluated in oral cells from 11- to 16-year-old girls living in a foster home in the central area of México City. Variables analyzed for possible association with these biomarkers include smoking habits, body mass index, metabolic polymorphisms for NAT1 and GSTM1 and whether the cells were obtained from the cheek or pharynx. The results indicated that individuals having the NAT1*10 homozygous genotype showed a significant increase in chromatin buds and binucleated cells. When the damage in the cheek was compared with damage in the pharynx, a significant increase in micronuclei and binucleated cells was found for the latter tissue in all the individuals analyzed.     

The yeast VPS genes affect telomere length regulation

Eukaryotic cells invest a large proportion of their genome in maintaining telomere length homeostasis. Among the 173 non-essential yeast genes found to affect telomere length, a large proportion is involved in vacuolar traffic. When mutated, these vacuolar protein-sorting (VPS) genes lead to telomeres shorter than those observed in the wild type. Using genetic analysis, we characterized the pathway by which VPS15, VPS34, VPS22, VPS23 and VPS28 affect the telomeres. Our results indicate that these VPS genes affect telomere length through a single pathway and that this effect requires the activity of telomerase and the Ku heterodimer, but not the activity of Tel1p or Rif2p. We present models to explain the link between vacuolar traffic and telomere length homeostasis.     

Anti-beta2-glycoprotein I (GPI) autoantibodies, annexin V binding and the anti-phospholipid syndrome

We examined the role of autoantibodies to beta2-GPI and prothrombin (PT) in the inhibition of annexin V binding to cardiolipin (CL) and the association with clinical manifestations of the anti-phospholipid syndrome (APS). Plasma samples from 59 patients with anti-phospholipid (aPL) antibodies were studied. Affinity purification of total IgG and IgG anti-ss2-GPI antibodies was performed using staphylococcal protein A and phospholipid liposomes. Annexin V binding to CL was significantly inhibited by 31/59 (53%) aPL+ plasma samples. There was a significant association between annexin V inhibition and elevated levels of IgG anti-cardiolipin (aCL) (r = -0.62; P < 0.001), IgG anti-ss2-GPI (r = -0.67; P < 0. 001) and a weaker association with lupus anti-coagulant (r = -0.27; P = 0.05). There was no association with other isotypes of aCL and anti-ss2-GPI or with anti-PT of any isotype. In patients with clinical manifestations of the APS there were higher levels of IgG aCL (median (range) Z score): 10.0 (0-17.6) versus 5.0 (0-16.1); P = 0.03), IgG anti-ss2-GPI (4.5 (0-11.3) versus 0.9 (0-9.7); P = 0.02) and greater inhibition of annexin V binding to CL (-3.4 (-11.4-0.6) versus -1.1 (-10.8-1.2); P = 0.22). Odds ratios for the laboratory assays and the presence of clinical manifestations of the APS varied between 0.38 and 4.16, with the highest values for IgG aCL (4.16), IgG anti-ss2-GPI (3.28) and annexin V inhibition (2.85). Additional experiments with affinity-purified IgG antibodies indicated that inhibition of annexin V binding was dependent upon the concentration of ss2-GPI and anti-ss2-GPI antibodies. These results indicate that inhibition of annexin V binding to procoagulant phospholipid surfaces is dependent upon anti-ss2-GPI antibodies and suggest a role for annexin V in the pathogenesis of the APS.     

The kinetics and distribution of C9 and SC5b-9 in vivo: effects of complement activation.

Many diseases associated with complement activation are characterized by tissue deposition of components of the terminal complement complex (TCC). The ninth component of complement (C9) plays an important role in the cytolytic effects, and may contribute to the non-lethal cell-regulating functions of the TCC. In this study we examined the behaviour of radiolabelled human C9 and its soluble complexed form SC5b-9 in vivo in order to determine the effects of complement activation on its turnover, distribution and molecular size. In normal rabbits the metabolic parameters of 125I-C9 (median and range) were: plasma half-life (t1/2) 25.9 (20.6-29.5) h, fractional catabolic rate (FCR) 5.7 (5.3-7.0)%/h, and extravascular/intravascular ratio (EV/IV) 0.7 (0.6-1.1). The distribution of radiolabelled C9 amongst body tissues was similar to that observed for rabbit serum albumin (RSA). Activation of the complement cascade with i.v. injection of cobra venom factor (CVF) resulted in rapid disappearance of C9 from the plasma and accumulation of protein-bound radiolabeled in the spleen (exceeding the plasma concentration) and the liver. RSA metabolism and distribution were unaffected by CVF. Fine performance liquid chromatography (FPLC) gel filtration of plasma samples suggested that monomeric C9 was the only major radiolabelled protein present during normal turnovers, whereas CVF administration was accompanied by the prompt appearance of a high mol. wt species consistent in size with SC5b-9. When injected directly, 125I-SC5b-9 disappeared rapidly from the plasma, falling by 50% in 0.7 (0.6-0.8) h, and less than 15% remaining after 4 h with accumulation of protein-bound label in the spleen and liver. These results demonstrate the complexity of C9 metabolism during complement activation.     

Inhibition of C5 or absence of C6 protects from sepsis mortality

Inhibiting complement anaphlytoxin C5a during sepsis may prevent sepsis mortality. Although human anti-C5 antibodies exist, their therapeutic use in microbial sepsis has been avoided because of the hypothesis that inhibiting C5b will prevent formation of the bactericidal membrane attack complex (MAC) and worsen clinical outcome. We wished to test the hypothesis that inhibition of C5 would improve outcomes in sepsis. Sepsis was induced in rats by laparotomy and cecal ligation and puncture (CLP) by an IACUC-approved protocol. Sham animals underwent laparotomy without CLP. Following CLP rats were randomized to receive a single IV dose of purified IgG ant-C5 antibody (Ab) or control IgG Ab. Anti-C5 Ab treated rats (n = 20) had significantly lower mortality vs. controls (n = 21), 20% vs. 52% (P = 0.019, log-rank). Analysis of bacterial load by culture of spleen and liver homogenates showed a reduction in colony forming units in anti-C5 Ab treated rats vs. control IgG (P = 0.003 and 0.009, respectively). Anti-C5 treatment reduced lung injury as measured by total MPO content of lung tissue (P = 0.024). Finally, rats genetically deficient in C6 production, unable to form MAC but capable of producing C5a and C5b, were protected from CLP-induced sepsis mortality. Our results show that in anti-C5 antibody therapy prevents CLP sepsis-induced mortality and improves lung injury. Inhibition of the complement MAC does not increase bacterial load or mortality, therefore, the use of anti-C5 therapy may be beneficial rather than detrimental in sepsis.