Current and Future Trends in the Clinical Diagnosis of Rickettsioses Sensu Lato.

Aims: The aim of this review is to present Rickettsioses sensu lato, with emphasis on their current and future clinical diagnosis. The review presents the conditions, the agents that cause them, and the current gold standards on their diagnosis in national and international reference centres. Additionally, this review covers the various emerging technologies available in the diagnosis of Rickettsioses and discusses their potential for future use as gold standards in the diagnosis of these diseases. Introduction: The introduction presents Rickettsioses sensu lato and gives a broad overview of the conditions they cause, the issues associated with their current diagnosis and the need for their improved, earlier and more accurate diagnosis, in order to prevent current issues with false negatives, misdiagnosis or delay in the diagnosis associated with these conditions, which often renders them grave or lethal. Main Body: The main body of the review presents in independent sections Rickettsias, Ehrlichia, Anaplasma, Bartonella and Coxiella and the conditions associated with each of these bacteria. Spotted fever, endemic typhus, human granulocytic anaplasmosis, human monocytic ehrlichioses, bartonellosis and Q-fever are some of the conditions associated with this group of proteobacteria. The emphasis is on the clinical diagnosis of these conditions and an overview of the current practice, gold standards in reference laboratories and improvements in these methodologies is presented. The last part of the review focuses on novel technologies in bacterial detection and their application specifically on Rickettsioses sensu lato, demonstrating how these technologies are being applied in this field and how they could improve current standards and resolve issues associated with the clinical diagnosis of rickettsioses. Conclusion: Rickettsioses sensu lato are conditions associated with proteobacteria historically included in the Rickettsiaceae family, able to cause a number of conditions, often grave or lethal. One of the major issues associated with poor clinical outcome is the lack of early and accurate differential diagnostic methodologies. Current methods, including serological and molecular biology techniques have various advantages and disadvantages, which new technologies available or currently in development may be in a position to resolve and the issues associated with the institution of such technologies.

A time-dependent, two-step binding mode of the nitro dye flavianic acid to trypsin in acid media

Synthetic dyes bind to proteins causing selective coprecipitation of the complexes in acid aqueous solution by a process of reversible denaturation that can be used as an alternative method for protein fractionation. The events that occur before precipitation were investigated by equilibrium dialysis using bovine trypsin and flavianic acid as a model able to cause coprecipitation. A two-step mode of interaction was found to be dependent on the incubation periods allowed for binding, with pronounced binding occurring after 42 h of incubation. The first step seems to involve hydration effects and conformational changes induced by binding of the first dye molecule, following rapid denaturation due to the binding of six additional flavianate anions to the macromolecule

Microencapsulation and tissue engineering as an alternative treatment of diabetes

In the 70's, pancreatic islet transplantation arose as an attractive alternative to restore normoglycemia; however, the scarcity of donors and difficulties with allotransplants, even under immunosuppressive treatment, greatly hampered the use of this alternative. Several materials and devices have been developed to circumvent the problem of islet rejection by the recipient, but, so far, none has proved to be totally effective. A major barrier to transpose is the highly organized islet architecture and its physical and chemical setting in the pancreatic parenchyma. In order to tackle this problem, we assembled a multidisciplinary team that has been working towards setting up the Human Pancreatic Islets Unit at the Chemistry Institute of the University of São Paulo, to collect and process pancreas from human donors, upon consent, in order to produce purified, viable and functional islets to be used in transplants. Collaboration with the private enterprise has allowed access to the latest developed biomaterials for islet encapsulation and immunoisolation. Reasoning that the natural islet microenvironment should be mimicked for optimum viability and function, we set out to isolate extracellular matrix components from human pancreas, not only for analytical purposes, but also to be used as supplementary components of encapsulating materials. A protocol was designed to routinely culture different pancreatic tissues (islets, parenchyma and ducts) in the presence of several pancreatic extracellular matrix components and peptide growth factors to enrich the beta cell population in vitro before transplantation into patients. In addition to representing a therapeutic promise, this initiative is an example of productive partnership between the medical and scientific sectors of the university and private enterprises.

Flavianate, an amino acid precipitant, is a competitive inhibitor of trypsin at pH 3.0

Textile dyes bind to proteins leading to selective co-precipitation of a complex involving one protein molecule and more than one dye molecule of opposite charge in acid solutions, in a process of reversible denaturation that can be utilized for protein fractionation. In order to understand what occurs before the co-precipitation, a kinetic study using bovine ß-trypsin and sodium flavianate was carried out based on reaction progress curve techniques. The experiments were carried out using a-CBZ-L-Lys-p-nitrophenyl ester as substrate which was added to 50 mM sodium citrate buffer, pH 3.0, containing varying concentrations of ß-trypsin and dye. The reaction was recorded spectrophotometrically at 340 nm for 30 min, and the families of curves obtained were analyzed simultaneously by fitting integrated Michaelis-Menten equations. The dye used behaved as a competitive inhibitor of trypsin at pH 3.0, with Ki = 99 µM; kinetic parameters for the substrate hydrolysis were: Km = 32 µM, and kcat = 0.38/min. The competitive character of the inhibition suggests a specific binding of the first dye molecule to His-57, the only positively charged residue at the active site of the enzyme

Jejunal absorption of trypsin in rat and guinea pig

Gut absorption is one of the first requirements for the study of the mechanism of a possible anti-inflammatory action of proteases, such as orally administered trypsin. Porcine trypsin absorption was studied in isolated jejunal loops of rats (female Holtzman and male Wistar) and guinea pig (males) by open-loop perfusion. Trypsin was dissolved in Tyrode solution and the solution perfused at a rate of 0.5 ml/min, at 37§C. Trypsin activity, total protein, and sodium and potassium concentrations were assayed in the jejunal effluent; the values were unchanged throughout the experiments, which lasted 45 to 120 min. Using a high sensitivity ELISA (i.e. pg/ml), trypsin absorption could be demonstrated by determination of the enzyme in the mesenteric venous blood (samples of 0.5 ml); the enzyme concentration increased with time of perfusion. The linear range-specificity for intact trypsin varied from 1 to 500 ng/well. In this assay polyclonal antibodies prepared against trypsin-TLCK were utilized. Whereas trypsin concentration in the perfused lumen was practically constant at 0.12 mg/ml, the concentration of absorbed trypsin in mesenteric vein blood increased from about 100 ng/ml at time zero to 1.8 µg/ml, after 45 min of perfusion. Histological and ultrastructural examination of the jejunal mucosa before and after perfusion revealed that the brush-border, basal membrane, and junctional complexes were fully preserved, thus eliminating the possibility that trypsin might have destroyed the structures, thereby reaching the blood circulation. The present data indicate that µg quantities of trypsin were absorbed by the isolated jejunal loop of the rat

Competitive parabolic inhibition of bovine trypsin by benzamidines

Competitive parabolic inhibition, a rare type of inhibition of one-substrate enzymes, is described for alpha-and beta-trypsin. The enzymes were so inhibited by two bis-benzamidines 4-4' diazoamino-bis-benzamidine, Berenil (DABB) and its platinum complex, DABB-PtCl2, acting on acyl-amino acid-peptidyl nitroanilides (Nan) substrates, when inhibitor concentrations exceed 10 mM and approch the millimolar range. The type of nonlinear inhibition observed require4s ternary complex formation between one enzyme molecule and two inhibitor molecules (M. E. M), and also permits the formation of the mixed ternary complex (M. E. S.). Binding of the first DABB molecule to the active center of trypsin takes place with K1 values of ca. 1.50 uM for both alpha-and- beta-trypsin. The secondary binding site binds the inhibitor with dissociation constants K12 close to 0.25 mM for both forms of the enzyme, as determined with different substrates. The dissociation constants of the ternary mixed complexes (Ksi and Kis), however, depend on the structural features of the substrates, which are of negligible importance for Bz-Arg-Nan, but significant for Ac-Phe-Arg-Nan and D-Val-Leu-Arg-Nan, reflecting subsite interactions between S1-S3 and S'2. Pentamidine, a diamidino-4,4'-diphenoxy-alkane with a flexible chain, behaved as a strict competitive inhibitor. This implies that the triazene moiety of DABB is involved in the interaction between the inhibitor and the secondary binding site of the enzyme