[Classification of dengue hemorrhagic fever using decision trees in the early phase of the disease]. / Clasificación de dengue hemorrágico utilizando árboles de decisión en la fase temprana de la enfermedad.

INTRODUCTION: dengue is a viral disease with endemic behavior. At the beginning of the illness it is not possible to know which patients will have an unfavorable evolution and develop a severe form of dengue. However, some warning symptoms and signs may be present. OBJECTIVE: to apply decision tree techniques to the exploration of signs of severity in the early phase of the illness. METHODS: the study sample was made up of 230 patients admitted with dengue to "Pedro Kouri" Institute of Tropical Medicine in 2001. The variables considered for the classification were the signs, symptoms and laboratory exams on the third day of evolution of the illness. The algorithm of classification and regression trees using the Gini's index was applied. Different loss matrices to improve the sensitivity were considered. RESULTS: the algorithm CART, corresponding to the best loss, had a sensitivity of 98,68% and global error of 0,36. Without considering loss, it obtained its sensitivity reached 74% with an error of 0,25. In both cases, the most important variables were platelets and hemoglobin. CONCLUSIONS: the study submitted rules of decision with high sensitivity and negative predictive value of utility in the clinical practice. The laboratory variables resulted more important from the informational viewpoint than the clinical ones to discriminate clinical forms of dengue.

Functional analysis in serum from atypical Hemolytic Uremic Syndrome patients reveals impaired protection of host cells associated with mutations in factor H.

A subgroup of patients with the most severe form of the Hemolytic Uremic Syndrome (HUS) presents mutations in the complement regulatory protein factor H. The functional analyses of the factor H mutant proteins purified from some of these patients have shown a specific defect in the capacity to control complement activation on cellular surfaces. Here, we show that these factor H-related complement regulatory defects can be detected in the patients' serum with a simple hemolytic assay. Data obtained from HUS patients and control individuals indicate that this assay is a useful tool for the molecular diagnosis of factor H-related HUS.

Complement factor I deficiency associated with recurrent meningitis coinciding with menstruation.

BACKGROUND: Complement (C) factor I deficiency is a rare immunodeficiency state frequently associated with recurrent pyogenic infections in early infancy. This deficiency causes a permanent uncontrolled activation of the alternative pathway resulting in massive consumption of C3. PATIENT: A 23-year-old woman with monthly recurrent meningitis episodes, mostly in the perimenstrual period, since August 1999. Previously, at age 16 years, she had meningococcal sepsis, also coinciding with menstruation. OBJECTIVES: To study the patient and her family to elucidate the molecular defects in the pedigree and to evaluate her clinical evolution. RESULTS: We describe clinical, immunological, and treatment follow-up during this period. First, we characterized the existence of a total complement factor I deficiency defined by undetectable levels by enzyme immunosorbent assay. This total deficiency was also found in her sister. Her parents and brother had approximately half of the normal levels. In addition, the patient had very low levels of C3; factor B; and an important reduction of factor H, properdin, C5, C7, and C8 complement components. Additional studies in the patient's sera evidenced high levels of immune complexes containing C1q and immunoglobulin (Ig) G, as well as C3b/factor H, C3b/properdin, C3b/IgG, and properdin/IgG complexes. Treatment with prophylactic antibiotics, antiestrogen medication, plasma infusions, or intravenous immunoglobulin has been unsuccessful in avoiding consecutive meningitis episodes. CONCLUSION: For the first time to our knowledge, these data present an unusual relationship between meningitis episodes and menstruation in factor I immunodeficiency.

Clustering of missense mutations in the C-terminal region of factor H in atypical hemolytic uremic syndrome.

Hemolytic-uremic syndrome (HUS) is a microvasculature disorder leading to microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure. Most cases of HUS are associated with epidemics of diarrhea caused by verocytotoxin-producing bacteria, but atypical cases of HUS not associated with diarrhea (aHUS) also occur. Early studies describing the association of aHUS with deficiencies of factor H suggested a role for this complement regulator in aHUS. Molecular evidence of factor H involvement in aHUS was first provided by Warwicker et al., who demonstrated that aHUS segregated with the chromosome 1q region containing the factor H gene (HF1) and who identified a mutation in HF1 in a case of familial aHUS with normal levels of factor H. We have performed the mutational screening of the HF1 gene in a novel series of 13 Spanish patients with aHUS who present normal complement profiles and whose plasma levels of factor H are, with one exception, within the normal range. These studies have resulted in the identification of five novel HF1 mutations in four of the patients. Allele HF1 Delta exon2, a genomic deletion of exon 2, produces a null HF1 allele and results in plasma levels of factor H that are 50% of normal. T956M, W1183L, L1189R, and V1197A are missense mutations that alter amino acid residues in the C-terminal portion of factor H, within a region--SCR16-SCR20--that is involved in the binding to solid-phase C3b and to negatively charged cellular structures. This remarkable clustering of mutations in HF1 suggests that a specific dysfunction in the protection of cellular surfaces by factor H is a major pathogenic condition underlying aHUS.

Internalization of factor J and cellular signalization after factor J-cell interaction.

Factor J (FJ) is a cationic glycoprotein with inhibitory activity in vitro against both classical and alternative pathways of complement activation. Recently FJ has been implicated in adhesion to several cell lines, through a membrane receptor identified as nucleolin. In the present work we study the events that follow the binding of FJ to cells. After incubation of K562 with FJ, this protein was internalized actively and localized in the cytoplasm and nucleus. Adhesion to immobilized FJ induced tyrosine phosphorylation of several intracellular proteins in Jurkat cell line with a similar pattern to that induced by fibronectin (FN), an extracellular matrix protein. This effect was maximal at 5 min and decreased after 10 min, and inhibited by anti-FJ monoclonal antibody (mAb). These results suggest that the binding of FJ to cells may play an important role in transduction of biochemical signals across the plasma membrane to the cell interior.

Cellular adhesion mediated by factor J, a complement inhibitor. Evidence for nucleolin involvement.

Factor J (FJ) is a complement inhibitor that acts on the classical and the alternative pathways. We demonstrated FJ-cell interactions in fluid phase by flow cytometry experiments using the cell lines Jurkat, K562, JY, and peripheral blood lymphocytes. FJ bound to plastic plates was able to induce in vitro adhesion of these cells with potency equivalent to fibronectin. As evidence for the specificity of this reaction, the adhesion was blocked by MAJ2, an anti-FJ monoclonal antibody, and by soluble FJ. Attachment of the cells required active metabolism and cytoskeletal integrity. The glycosaminoglycans heparin, heparan sulfate, or chondroitin sulfates A, B, and C inhibited to varying degrees the binding of FJ to cells, as did treatment with chondroitinase ABC. In the search for a putative receptor, a protein of 110 kDa was isolated by affinity chromatography, and microsequence analysis identified this protein as nucleolin. Confocal microscopy evidenced the presence of nucleolin in cell membrane by immunofluorescence with monoclonal (D3) and polyclonal anti-nucleolin antibodies in Jurkat cells. The interaction FJ-nucleolin was evidenced by Western blot and enzyme-linked immunosorbent assay. Furthermore, purified nucleolin and D3 inhibited adhesion of Jurkat cells to immobilized FJ, suggesting that the interaction was specific and that nucleolin mediated the binding.

Modulation of C4b-binding protein isoforms during the acute phase response caused by orthopedic surgery.

Orthopedic surgery is described as an event with a high risk of thromboembolic diseases. This is probably a consequence of a synergistic combination of different risk factors in the patients subjected to this type of surgery, including age, immobilization, anesthesia and different hypercoagulable states. After surgery patients develop an acute-phase response that leads to changes in several plasma proteins. One of these proteins is the complement regulator C4b-binding protein (C4BP). We have recently shown that in some acute-phase patients C4BP is incorrectly controlled (with elevation of the C4BP beta-containing isoforms), leading to a potential hypercoagulable state by decreasing the plasma levels of free (active) protein S. Here we have studied whether patients subjected to orthopedic surgery have an appropriate modulation of the C4BP isoforms during their postoperative acute-phase responses. We have analyzed the evolution of the C4BP isoforms in serial samples from 11 patients who have undergone knee (or hip) prosthesis surgery (mean age 70 years), or scoliosis surgery (mean age 18 years). Our data suggest a similar evolution of C4BP isoforms in all these patients, with an almost exclusive increase of C4BP isoforms lacking C4BP beta polypeptides and steady levels of free protein S.

Elevated factor J levels in synovial fluid from patients with inflammatory arthropathies.

Factor J (FJ) is a complement inhibitor that is able to regulate in vitro both the classical and alternative human complement pathways. In the search of its biological significance, we have analyzed FJ levels in synovial fluid from patients with different arthropathies, in which IL-6 levels had been previously measured. The pathologies included in this study were: rheumatoid arthritis (RA) (n = 21), crystal deposition diseases (CDD) (n = 6), osteoarthritis (OA) (n = 23), spondyloarthritis (SpA) (n = 3) and other inflammatory arthropathies (OIA) (n = 4). We found a good correlation between IL-6 and FJ levels (r = 0.33, p = 0.0132) in the 57 processed samples. Synovial fluids had high levels of IL-6 (median: 3000 pg/ml). Besides, we found that FJ levels were elevated (241 +/- 429 micrograms/ml) when compared with NHS (5.32 +/- 2.82 micrograms/ml). Considering OA patients as control group for non-inflammatory situation, we found that FJ levels were significantly elevated in inflammatory patients only if RA patients were excluded. Furthermore, there were also significant differences with CDD patients. In addition, we have examined the presence of this inhibitor in synovial fluid by Western blot after running gels at acid pH and electrophoretical transference at the same pH. In these experiments, we evidenced the presence of a cationic protein immunoreactive with polyclonal and monoclonal anti-FJ antibodies. In conclusion, FJ levels are elevated in pathological synovial fluids. FJ could be an acute phase reactant as other molecules present in the synovial fluid, or could be shed from extracellular matrix as a consequence of the high enzymatic activity present in the articular fluid or as a response to the inflammatory stimulus.

Factor J, an inhibitor of the classical and alternative complement pathway, does not inhibit esterolysis by factor D.

Factor J (FJ) is an inhibitor of the classical and alternative complement pathways. On the classical pathway factor J disrupts the C1 component, and on the alternative pathway, factor J disrupts the C3 convertase (C3b,Bb) by a direct interaction of FJ with the components C3b and Bb. The aim of this work was to verify whether FJ could have any effect on factor D proteolytic activity since previous experiments could not rule out an eventual inhibition by factor J on factor D enzymatic activity. For this purpose, the reactivity of serine proteinase factor D was determined by using two peptide thioester substrates, Z-Lys-SBzl.HCl and Z-Lys-Arg-SBzl.2HCl, in the presence and in the absence of factor J. Kinetic studies evidenced that FJ did not affect the enzymatic activity of factor D in any case.

Cell surface molecules related to factor J in human lymphoid cells and cell lines.

Factor J (FJ) is a cationic glycoprotein that is able to inhibit in vitro both the classical and alternative pathways of complement. FJ was purified to homogeneity from human urine by sequential chromatographic steps. To examine the expression of FJ in human cells we obtained mAbs against urine-purified FJ. Preliminary studies by immunocytochemistry revealed that one of the anti-FJ mAbs recognized cell surface components of certain cell lines, such as K562 and U937 cells, so we have focused subsequently on the detection of these homologue membrane-bound FJ Ags (FJ-h Ags) in cell lines of lymphoid (Ramos and Jurkat) and mieloyd (U937 and K562) origin, as well as in peripheral blood cells. The flow cytometry analysis of the examined cell lines revealed partial staining ranging from 10% (U937) to 29% (K562) positive cells. Flow cytometry of peripheral blood cells showed a positive staining in a small but consistent population of lymphocytes (mean = 11%, n = 17) but none at all on monocytes, granulocytes, erythrocytes, or platelets. Double Ab immunostaining of lymphocytes showed that the FJ-h positive population included mainly B lymphocytes (a mean of 63% CD19+ were FJ-h positive). When we analyzed peripheral blood lymphocytes from a patient with chronic lymphocytic leukemia B (95% CD19+/CD5+), the majority of these (55%) bore FJ-h on their surface. Acid strip of these cells did not abrogate the surface staining, which supports the finding that the Ag is tightly bound to the membrane. Immunoprecipitation from U937 cell lysates showed a single 65 kDa band under reducing conditions. FJ-h Ags purified from K562 and U937 cells displayed inhibitory activity in the functional EAC14 assay for the classical complement pathway, as did urine FJ, and they were recognized immunochemically by five different (one polyclonal and four monoclonal) anti-FJ Abs. In conclusion, FJ-homologues are present in the membranes of several human cell lines that show functional and antigenic characteristics similar to soluble urine FJ. They are also found in a small subset of peripheral blood lymphocytes, mainly B cells. The structural relationship between both soluble urine FJ and these membrane-bound FJ-h remains to be established.

Factor J, a human inhibitor of complement C1, is a cationic, highly glycosylated protein.

Factor J (FJ) is a new inhibitor of the complement system. This work supports the fact that FJ is a cationic molecule (pI > or = 9.6 in native conditions, or pI = 8.1 in denaturing conditions) with a high sugar content (40%) that is able to interact with different lectins, suggesting a complex glycosylation. SDS impaired FJ migration in polyacrylamide gel electrophoresis. In Triton-acid-urea-polyacrylamide gel electrophoresis FJ migrated as a complex, dispersed molecule. In contrast, FJ after Smith degradation (dFJ) gave a single, smeared band of M(r) = 23.4 kDa in reducing SDS-PAGE. dFJ retained only 60% of the initial inhibitory activity of intact FJ. When digestions with different proteinases were performed, no modification of activity was observed. After beta-glucuronidase digestion, FJ lost 80% of its initial activity. Consequently, glycosylation plays an important role in the inhibitory activity of FJ.

The inhibitory effect of factor J on the alternative complement pathway.

Factor J (FJ) is a cationic glycoprotein with inhibitory activity in C1, the first component of the classical complement pathway. This study demonstrates that FJ is able to regulate the activity of the alternative complement pathway. FJ inhibits the generation of fluid-phase and cell-bound alternative pathway C3 convertase, C3b,Bb (C3-cleaving enzyme). Thus, FJ interferes with the generation of alternative pathway C3 convertase when sheep erythrocytes bearing antibody and activated C3 and C4 (EAC4b,3b) are incubated with the individual complement components, factors B, D, and P. FJ accelerates the decay of C3 convertase with a time course similar to that of factor H, and when both regulators are present together, the decay of enzyme activity is faster than when they are added separately. Furthermore, FJ is able to inhibit the cleavage of C3 by factor B in a fluid-phase assay. FJ prevents the initiation of alternative pathway activation in "more stabilized systems" with well known activators of alternative pathway C3 convertase such as C3 nephritic factor (an autoantibody against alternative pathway C3 convertase), cobra venom factor, and rabbit erythrocytes. In these systems, FJ has no effect on C3 convertase stabilized by rabbit erythrocytes or cobra venom factor. In contrast, FJ promotes the dissociation of C3 convertase stabilized by C3 nephritic factor, but with much lower efficiency than in preventing initiation. Direct interaction of FJ with individual components of C3 convertase was shown by a solid-phase binding assay using plates coated with C3, C3b, B, Bb, or FJ. FJ inhibitory activity in the alternative pathway can be modulated by polyanions like heparin. FJ-mediated inhibition in the alternative complement pathway can be modified by surface interactions, as occurs during alternative pathway C3 convertase activation. Thus, when FJ is adsorbed by and eluted from hydroxylapatite and reverse-phase columns, its inhibitory effect on more stabilized systems is lost. This loss of inhibitory activity is fully reversed when FJ is rechromatographed on heparin-Sepharose or Sepharose columns. Taking into account these data, FJ may be included in the group of highly charged molecules that inhibit the activation of classical and alternative complement pathways (i.e. eosinophil major basic protein, protamine, and heparin).

Factor J, an inhibitor of the complement classical pathway: the quantitation by an ELISA inhibition assay in normal human serum.

Factor J (FJ) is a protein present in human serum, with inhibitory activity against C1. Here we describe the quantitation of FJ in human serum by means of an ELISA inhibition assay. We have purified FJ from the urine of a normal donor following a previously published method with slight modifications. Polyclonal anti-FJ antibodies have been raised in rabbits immunized with a single dose of purified antigen injected in multiple sites. IgG from polyclonal FJ antiserum, coupled to a solid matrix (Affi-Prep gel) was able to adsorb purified FJ antigenically and functionally. Furthermore, anti-FJ specifically retained serum components antigenically related with urine FJ. Taking into account this reactivity, we have developed an inhibition enzyme-linked immunosorbent assay (ELISA) useful for measuring FJ levels in normal human serum. This immunoassay involves preincubating polyclonal anti-FJ with different dilutions of normal human serum to quantitatively reduce the antibody available to bind to purified FJ-coated microtiter plates. Binding of remaining antibody to the microtiter plate is measured spectrophotometrically using peroxidase-conjugated secondary antibody. Quantitation is accomplished by comparison with a known quantity of purified FJ. Conditions for optimization of this quantitative assay have been assessed, including trials with different blocking agents, of which nonfat milk gave the best results. Preliminary experiments showed the existence of paradoxical effects, that is, high nonspecific binding at high serum dilutions. We have eliminated these effects by including high ionic strength (0.4 M NaCl) in the sample incubation solution. Sensitivity and reproducibility parameters have also been established. FJ levels have been measured for the first time in sera from 86 healthy donors.(ABSTRACT TRUNCATED AT 250 WORDS)