Aerial pesticide application causes DNA damage in pilots from Sinaloa, Mexico

The use of pesticides in agricultural production originates residues in the environment where they are applied. Pesticide aerial application is a frequent source of exposure to pesticides by persons dedicated to agricultural practices and those living in neighboring communities of sprayed fields. The aim of the study was to assess the genotoxic effects of pesticides in workers occupationally exposed to these chemicals during their aerial application to agricultural fields of Sinaloa, Mexico. The study involved 30 pilots of airplanes used to apply pesticides via aerial application and 30 unexposed controls. Damage was evaluated through the micronucleus assay and by other nuclear abnormalities in epithelial cells of oral mucosa. The highest frequency ratios (FR) equal to 269.5 corresponded to binucleated cells followed by 54.2, corresponding to cells with pyknotic nuclei, 45.2 of cells with chromatin condensation, 3.7 of cells with broken-egg, 3.6 of cells with micronucleus, and 2.0 of karyolytic cells. Age, worked time, smoking, and alcohol consumption did not have significant influence on nuclear abnormalities in the pilots studied. Pesticide exposure was the main factor for nuclear abnormality results and DNA damage. Marked genotoxic damage was developed even in younger pilots with 2 years of short working period, caused by their daily occupational exposure to pesticides.

Origin, evolution and function of the hemipteran perimicrovillar membrane with emphasis on Reduviidae that transmit Chagas disease

The peritrophic matrix is a chitin-protein structure that envelops the food bolus in the midgut of the majority of insects, but is absent in some groups which have, instead, an unusual extra-cellular lipoprotein membrane named the perimicrovillar membrane. The presence of the perimicrovillar membrane (PMM) allows these insects to exploit restricted ecological niches during all life stages. It is found only in some members of the superorder Paraneoptera and many of these species are of medical and economic importance. In this review we present an overview of the midgut and the digestive system of insects with an emphasis on the order Paraneoptera and differences found across phylogenetic groups. We discuss the importance of the PMM in Hemiptera and the apparent conservation of this structure among hemipteran groups, suggesting that the basic mechanism of PMM production is the same for different hemipteran species. We propose that the PMM is intimately involved in the interaction with parasites and as such should be a target for biological and chemical control of hemipteran insects of economic and medical importance.

PstS-1, the 38-kDa Mycobacterium tuberculosis glycoprotein, is an adhesin, which binds the macrophage mannose receptor and promotes phagocytosis

Mycobacterium tuberculosis, the primary causative agent of tuberculosis, infects macrophages and transforms the hostile intracellular environment into a permissive niche. M. tuberculosis infects macrophages using a variety of microbial ligand/cell receptor systems. In this study, binding assays with biotin-labelled mycobacterial cell wall proteins revealed five Concanavalin A-reactive proteins that bind macrophages. Among these proteins, we identified PstS-1, a 38-kDa M. tuberculosis mannosylated glycolipoprotein, and characterized it as an adhesin. Inhibition assays with mannan and immunoprecipitation demonstrated that PstS-1 binds the mannose receptor. We purified PstS-1 to 95.9% purity using ion exchange chromatography. The presence of mannose in purified PstS-1 was demonstrated by Concanavalin A interaction, which was abolished in the presence of sodium m-periodate and α-D-mannosidase. Gas chromatography revealed that purified PstS-1 contained 1% of carbohydrates by weight, which was mainly mannose. Finally, we used fluorescent microbeads coated with purified PstS-1 in phagocytosis assays and discovered that microbead uptake was inhibited by the pre-incubation of cells with GlcNAc, mannan and α-methyl mannoside. The interaction of PstS-1 coated beads with the mannose receptor was confirmed by confocal colocalization studies that showed high Pearson and Manders's colocalization coefficients. Our findings contribute to a better understanding of the strategies M. tuberculosis uses to infect host cells, the critical first step in the pathogenesis of tuberculosis.

Characterization of a lectin from the craysfish Cherax quadricarinatus hemolymph and its effect on hemocytes

Lectins participate in the immune mechanisms of crustaceans. They have been considered as humoral receptors for pathogen-associated molecular patterns; however, some reports suggest that lectins could regulate crustacean cellular functions. In the present study, we purified and characterized a serum lectin (CqL) from the hemolymph of Cherax quadricarinatus by affinity chromatography and determined its participation in the regulation of hemocytes' oxidative burst. CqL is a 290-kDa lectin in native form, constituted by 108, 80, and 29-kDa subunits. It is mainly composed of glycine, alanine, and a minor proportion of methionine and histidine. It showed no carbohydrates in its structure. CqL is composed of several isoforms, as determined by 2D-electrophoresis, and shows no homology with any crustacean protein as determined by Lc/Ms mass spectrometry. CqL agglutinated mainly rat and rabbit erythrocytes and showed a broad specificity for monosaccharides such as galactose, glucose, and sialic acid, as well as for glycoproteins, such as porcine stomach and bovine submaxillary mucin and fetuin. It is a Mn(2+)-dependent lectin. CqL recognized 8% of crayfish granular hemocytes and increased 4.2-fold the production of hemocytes' superoxide anion in vitro assays when compared with non-treated hemocytes. This effect showed the same specificity for carbohydrates as hemagglutination; moreover, superoxide dismutase and diphenyleneiodonium chloride were effective inhibitors of CqL oxidative-activation. The CqL homoreceptor is a 120-kDa glycoprotein identified in the hemocytes lysate. Our results suggest that CqL participates actively in the regulation of the generation of superoxide anions in hemocytes using NADPH-dependent mechanisms.

Identification of iron-acquisition proteins of Avibacterium paragallinarum

When Avibacterium paragallinarum reference strain 0083 (serovar A) was grown in an iron-restricted culture medium, the expression of the 60, 68 and 93 kDa outer membrane proteins increased as compared with normal media. Sera of chickens experimentally infected with Av. paragallinarum recognized these iron-restriction induced proteins, suggesting their expression in vivo. The three outer membrane proteins were identified as transferrin receptor and iron transport proteins by mass spectroscopy and a search in sequence databases. As these proteins have been reported to be regulated by the Fur protein in many bacteria, we investigated, through molecular methods, the presence of the fur gene in Av. paragallinarum. A candidate fur gene of Av. paragallinarum was amplified by polymerase chain reaction using complementary primers to conserved regions of fur gene sequences from members of the Pasteurellaceae family. The nucleotide sequence of the cloned gene, from ATG to TAA stop codon, was 453 base pairs in length and the deduced amino acid sequence showed 94% identity with Fur sequences of Actinobacillus pleuropneumoniae and Haemophilus ducreyi. The Av. paragallinarum deduced Fur protein (17.8 kDa) amino acid sequence contains the N-terminal helix-turn-helix DNA-binding domain and the two iron-binding sites in the C-terminal end, typical of other described Fur proteins. The study of iron-restriction-induced proteins and the mechanism regulating their expression could lead to an understanding of the responses of Av. paragallinarum to survive in an iron-restricted environment on host mucosal surfaces.

Cell death mechanisms induced by cytotoxic lymphocytes

One of the functions of the immune system is to recognize and destroy abnormal or infected cells to maintain homeostasis. This is accomplished by cytotoxic lymphocytes. Cytotoxicity is a highly organized multifactor process. Here, we reviewed the apoptosis pathways induced by the two main cytotoxic lymphocyte subsets, natural killer (NK) cells and CD8+ T cells. In base to recent experimental evidence, we reviewed NK receptors involved in recognition of target-cell, as well as lytic molecules such as perforin, granzymes-A and -B, and granulysin. In addition, we reviewed the Fas-FasL intercellular linkage mediated pathway, and briefly the cross-linking of tumor necrosis factor (TNF) and TNF receptor pathway. We discussed three models of possible molecular interaction between lytic molecules from effector cytotoxic cells and target-cell membrane to induction of apoptosis.

Crystallization and identification of the glycosylated moieties of two isoforms of the main allergen Hev b 2 and preliminary X-ray analysis of two polymorphs of isoform II

Latex from Hevea brasiliensis contains several allergenic proteins that are involved in type I allergy. One of them is Hev b 2, which is a beta-1,3-glucanase enzyme that exists in different isoforms with variable glycosylation content. Two glucanase isoforms were isolated from trees of the GV-42 clone by gel filtration, affinity and ion-exchange chromatography. Isoform I had a carbohydrate content of about 20%, with N-linked N-acetyl-glucosamine, N-acetyl-galactosamine, fucose and galactose residues as the main sugars, while isoform II showed 6% carbohydrate content consisting of N-acetyl-glucosamine, fucose, mannose and xylose. Both isoforms were crystallized by the hanging-drop vapour-diffusion method. Isoform I crystals were grown using 0.2 M trisodium citrate dihydrate, 0.1 M Na HEPES pH 7.5 and 20%(v/v) 2-propanol, but these crystals were not appropriate for data collection. Isoform II crystals were obtained under two conditions and X-ray diffraction data were collected from both. In the first condition (0.2 M trisodium citrate, 0.1 M sodium cacodylate pH 6.5, 30% 2-propanol), crystals belonging to the tetragonal space group P4(1) with unit-cell parameters a = b = 150.17, c = 77.41 A were obtained. In the second condition [0.2 M ammonium acetate, 0.1 M trisodium citrate dihydrate pH 5.6, 30%(w/v) polyethylene glycol 4000] the isoform II crystals belonged to the monoclinic space group P2(1), with unit-cell parameters a = 85.08, b = 89.67, c = 101.80 A, beta = 113.6 degrees. Preliminary analysis suggests that there are four molecules of isoform II in both asymmetric units.

Characterization of a cytotoxic CD57+ T cell subset from patients with pulmonary tuberculosis

We investigated the proportion, phenotype, and cytotoxicity of CD8+CD57+ and CD57- T cells in peripheral blood from 20 tuberculosis (TB)-patients and 20 healthy tuberculin skin test-positive donors. Our results showed an increase in CD8+CD57+ T cells from TB-patients as compared with those from age-matched healthy donors (p<0.0001). CD8+CD57+ T cells from TB-patients expressed CD69, perforin, granzyme-A, and a CD28-CD62L-CD161- phenotype without recognition for the alpha-galactosylceramide-CD1d complex. This cell subset also expressed TNF-alpha and IFN-gamma, under phorbol-myristate-acetate/ionomycin stimulation. Interestingly, the cytotoxicity against autologous monocytes was higher in CD57- cells from TB-patients and donors than their CD57+ counterparts, in the presence of Mycobacterium tuberculosis H37Rv culture filtrate. However, only CD8+CD57+ T cells from TB-patients exhibited spontaneous cytotoxicity against monocytes in the absence of antigen. Our results suggest that CD8+CD57+ T cells are a subset of effector cells that could be helpful to evaluate the cell-mediated immune response to M. tuberculosis.

CD4+ CD30+ T cells perpetuate IL-5 production in Dermatophagoides pteronyssinus allergic patients

BACKGROUND

Airway allergic diseases are regulated by interleukin (IL)-5, which causes infiltration of eosinophils into the bronchial epithelium, and by IL-4 which increases serum immunoglobulin E (IgE) production and promotes CD30 expression on Th cells. CD30 generates a costimulatory signal involved in apoptosis or cell proliferation, depending on the microenvironment. Our aims were: (i) to analyze if CD4+ CD30+ T cells from allergic patients proliferate in response to Dermatophagoides pteronyssinus, and (ii) if upon stimulation this cell population produces IL-4 and IL-5.

METHODS

Peripheral blood mononuclear cell (PBMC) from 17 allergic rhinitis and mild allergic asthma patients and 12 healthy nonallergic individuals were stimulated with allergen in the presence or absence of anti-IL-4, anti-IL-5 or anti-IL-4Ralpha monoclonal antibodies (mAbs). TdT-mediated dUTP nick end-labeling (TUNEL) assay, 7-aminoactinomycin-D (7-AAD) intercalation, and flow cytometry were used to determine the CD4+ CD30+ blasts percentage, cell proliferation, apoptosis, and intracellular cytokines after 7 culture days.

RESULTS

Cell proliferation induced with allergen showed that 90% of the allergen-stimulated blasts were CD4+, 50% of which were CD30+. Allergen-stimulated PBMC showed a progressive increase (mean: from 7% to 23%) of CD4+ CD30+IFN-gamma+ and CD4+ CD30+IL-4+ blasts which diminished (mean: 6%) after 5 culture days. In contrast, CD4+ CD30+IL-5+ blasts showed a continuous progression (from 12% to 24%) that maintained after 7 culture days. The vast majority of CD4+ CD30+ blasts were negative to 7-AAD or TUNEL. Additionally, a significant decrease (34%) was observed in the number of CD4+ CD30+ blasts when IL-4 was neutralized.

CONCLUSIONS

These data suggest that specific allergen stimulation of PBMC isolated from allergic patients generates a nonapoptotic CD4+ CD30+ blast subset that produces IL-5.

Prolactin effect on CD69 and CD154 expression by CD4+ cells from systemic lupus erythematosus patients

OBJECTIVE

The aim was to explore the role of prolactine (PRL) in the lymphocyte activation process in active and inactive systemic lupus erythematosus (SLE) patients in an in vitro model.

METHODS

Peripheral blood mononuclear cells (PBMNC) were isolated from SLE patients and healthy individuals. The mRNA for prolactine and its receptor, obtained by standard techniques with an appropriate primer, were subjected to PCR and visualised. The PBMC were cultured with: a) medium alone as a negative control, b) unspecific mitogen as a positive control (PMA-ionomycin for CD154 or concanavalin A for CD69), c) PRL alone, d) mitogen plus PRL, e) mitogen plus antibody anti-PRL (1:50) and f) mitogen plus an unrelated antibody. Then CD69 and CD154 were determined by flow cytometry analysis.

RESULTS

Twelve inactive and 15 active SLE patients were studied. 25% of the active patients displayed hyperprolactinemia. Under basal conditions, CD69 expression was associated with disease activity. In contrast, CD154 did not show this association. The PBMNC activated in vitro were capable of producing and secreting prolactine as measured by mRNA and Nb2 assay. In the same way the mRNA for prolactine receptor was visualized. Cells from SLE patients cultivated with PRL alone did not display increased CD69 or CD154 expression. The addition of PRL to the unspecific stimulated culture did not have an additive effect. In contrast, the addition of antibodies against PRL, in order to block the autocrine prolactine, resulted in a striking reduction in CD69 and CD154 expression.

CONCLUSIONS

PRL is produced and secreted by the immune cell and acts just after the first trigger signal of activation in an autocrine way. The expression of CD69 and CD154 molecules depend partially on the prolactine.

Coexistence of reactive plasticity and neurodegeneration in Alzheimer diseased brains

Alzheimer's disease (AD) is a pathological process characterized by neuron degeneration and, as recently suggested, brain plasticity. In this work, we compared the reactive plasticity in AD brains associated to O-glycosydically linked glycans, recognized by lectins from Amaranthus leucocarpus (ALL) and Macrobrachium rosenbergii (MRL), and the tau neuritic degeneration. The neuritic degenerative process was evaluated by the quantification of aggregated neuritic structures. Lesions were determined using antibodies against hyperphosphorylated-tau (AD2), amyloid-beta, and synaptophysin. In these conditions, we classified and quantified three pathological structures associated to the neuritic degenerative process: 1) Amyloid-beta deposits (AbetaDs), 2) Classic neuritic plaques (NPs), and 3) Dystrophic neurites clusters (DNCs) lacking amyloid-beta deposits. Reactive plasticity structures were constituted by meganeuritic clusters (MCs) and peri-neuronal sprouting in neurons of the CA4 region of the hippocampus, immunoreactive to synaptophysin (exclusively in AD brains) and GAP-43. Besides, MCs were associated to sialylated O-glycosydically linked glycans as determined by positive labeling with ALL and MRL. Considering that these lectins are specific for the synaptic sprouting process in AD, our results suggest the co-occurrence of of several areas of reactive plasticity and neuron degeneration in AD.

Histoplasma capsulatum yeast cells attach and agglutinate human erythrocytes

The ability of yeast cells of Histoplasma capsulatum to attach and agglutinate human erythrocytes has been described. This is the first report involving these yeasts in the hemagglutination phenomenon. Results revealed that the yeast cells were able to bind to erythrocytes irrespective of blood groups and to agglutinate them when a high density of yeast cells was used. Assays on the inhibition of yeast attachment to erythrocytes were also performed, using sugar-treated yeast cells. Results indicate that galactose (Gal), mainly the beta-anomer, specially inhibited yeast attachment. Disaccharides (Gal-derivatives) and glycosaminoglycans containing Gal residues, mainly chondroitin sulfate C, promote this type of inhibition. In addition, preliminary data of inhibition assays also involved a probable ionic strength driven mechanism mediated by sialic acid and heparan sulfate, suggesting that yeast binding to erythrocytes could be associated with negative charges of both molecules.

Development of a diagnostic test for Entamoeba histolytica using idiotype expression in human

The protozoan parasite Entamoeba histolytica is the etiological agent of human amebiasis. The pathology of the disease starts with the cytolysis of the host target cells by amoebae. It is initiated by the adhesion of trophozoites to the host cells, through surface lectin via specific receptors. These adherence lectins have been demonstrated to be highly conserved, and can be recognised by serum antibodies from patients with invasive amebiasis. Some of these molecules have been used as antigens in serologic studies, which has been very helpful in the diagnosis of invasive intestinal amebiasis. However, false-positive serologic reactivity can occur using E. histolytica extracts and purified antigens. Additional problems are because the extracts display a great enzymatic activity. Several diagnostic methods, using different molecules and techniques, have been described. However, the problem still remains since these tests are not capable of differentiating between amoebic liver abscess (ALA) and intestinal amebiasis.Here, the research has been addressed to the 66-kDa antigen, which is a part of the outer membrane proteins from the E. histolytica strain HM1-IMSS trophozoites. First of all, we characterized the 66-kDa antigen in order to prove the relevance. We found that the 66-kDa antigen is a part of the plasma membranes and is distributed rather homogeneously on the cell surface of trophozoites. Apparently, the 66-kDa antigen is a glycoprotein. Using a monoclonal antibody (MAb), we found 25% of inhibition in the erythrophagocytosis by the trophozoites. Starting form one monoclonal antibody, we prepared an anti-idiotype (anti-Id) antibody reagent, with the purpose of searching for the different expressions of the idiotype between the sera from ALA and the intestinal amebiasis patients. Moreover, we produced the antibody Ab3 that is capable of recognising the 66-kDa antigen; it means that the Ab2 displays the internal image of the antigen. We found that 91.6% of the serum from ALA patients displayed the expression of the Id. In contrast, 15.7% of the E. histolytica asymtomatic cyst carriers displayed the Id expression, 6.6% of the patients with another parasite infection, and 11% of the negative controls (serum from umbilical cords of newborn babies). Our results showed that the expression of the Id could be differentiated among the AHA patients from the other groups with a 91.6% sensibility and 88.3% specificity.

Toluidine blue-O staining of prion protein deposits

Prion diseases or transmissible spongiform encephalopathies are a group of fatal neurodegenerative diseases caused by an abnormal form of prion protein (PrP(sc)). In this study, we developed a sensitive histochemical detection of PrP(sc) deposits in a Gertsmann-Sträussler-Scheinker disease (GSS) patient using toluidine blue-O staining, a specific reagent to stain mucins and mucopolysaccharides. Detection of prion deposits correlated with immunohistochemistry using anti-prion antibodies. Control assays were performed using amyloid-beta (Abeta) plaques from Alzheimer's disease (AD) brains. Our results demonstrated that toluidine blue-O staining allowed to recognize 69.1+/-2.6% of the total plaques recognized by the anti-prion antibody. Furthermore, in the 15 studied brain regions from the GSS patient, toluidine blue-O revealed the same recognition pattern as anti-prion labeling. Toluidine blue-O stained specifically the prion deposits but not the Abeta plaques in AD brains. The specificity of the technique was confirmed in a Creutzfeldt-Jakob disease brain. This method opens several possibilities for postmortem diagnoses. Our results also suggest the relevance of specific post-translational modifications of PrP(sc), identified by toluidine blue-O, that might participate in the transformation of PrP(c) to PrP(sc).

Purification and characterization of a galactose-specific lectin from corn (Zea mays) coleoptile

We purified and characterized a lectin from the corn coleoptyle (Zea mays). The lectin (CCL) was purified by affinity chromatography on a Lactosyl-Sepharose 4B column. It is a glycoprotein of 88.7 kDa, composed mainly by glutamic, aspartic, glycine, and Ser residues; in a minor proportion, it contained methionine and cysteine residues. Carbohydrates that constituted 12% of the total weight comprised galactose, mannose, and N-acetyl-D-glucosamine. The lectin contained the blocked amino-terminus. Analysis of the lectin, determined from peptides obtained after trypsin digestion by MALDI-TOF (matrix-assisted laser desorption ionization-time of flight), indicated that CCL has 18% homology with a putative calcium-dependent Ser/Thr protein kinase, from Arabidopsis thaliana, and 39% homology with a NADPH-dependent reductase from Z. mays. The lectin showed hemagglutinating activity toward several erythrocytes, including human A, B, and O. Hapten inhibition assays indicated that the lectin interacts specifically with the OH on C4 from galactose residues. OH- on C1 plays a relevant role in the interaction with CCL, since beta-galactose residues are better recognized than those from the anomeric alpha-galactose. Lack of lectin activity was observed in corn extracts; the highest specific activity was obtained from coleoptyle obtained at the 7th day after seeding.

Sialylation is modulated through maturation in hemocytes from Macrobrachium rosenbergii

In this work we identified in adult and juvenile freshwater prawn, Macrobrachium rosenbergii, three major type of circulating hemocytes: fusiform; rounded; and large ovoid hemocytes. Rounded and large hemocytes represent the first defense line, since this type of cells exerts phagocytic activity as well as lectin synthesis. Considering that glycosylation plays important roles in cell communication and as a target for pathogenic microorganisms, in this report was also described the main glycosidic modifications that occur in the large and rounded hemocytes from the freshwater prawn during maturation as determined with lectins. Neu5Acalpha2,6Gal, was identified homogeneously distributed in the membrane in 90% of hemocytes from juvenile organisms. Maturation of the freshwater prawn induced a decrease or complete loss of Neu5Acalpha2,6Gal residues that were replaced with Neu5Acalpha2,3 molecules in practically all hemocytes from adult organisms. This change was paralleled by a diminution in 9-O-acetyl-neuraminic acid (Neu5,9Ac(2)) expression. T and Tn antigens (Galbetal,3 GalNAcalpha1-0-Ser/Thr or GalNAcalpha1-0-Ser/Thr, respectively), as well as N-glycosidically linked glycans, seem to be highly conserved throughout maturation. Our results show that sialylation of freshwater prawn hemocytes is modulated throughout the maturation process.

Pathogenesis II: fungal responses to host responses: interaction of host cells with fungi

Most of our knowledge concerning the virulence determinants of pathogenic fungi comes from the infected host, mainly from animal models and more recently from in vitro studies with cell cultures. The fungi usually present intra- and/or extracellular host-parasite interfaces, with the parasitism phenomenon dependent on complementary surface molecules. Among living organisms, this has been characterized as a cohabitation event, where the fungus is able to recognize specific host tissues acting as an attractant, creating stable conditions for its survival. Several fungi pathogenic for humans and animals have evolved special strategies to deliver elements to their cellular targets that may be relevant to their pathogenicity. Most of these pathogens express surface factors that mediate binding to host cells either directly or indirectly, in the latter case binding to host adhesion components such as extracellular matrix (ECM) proteins, which act as 'interlinking' molecules. The entry of the pathogen into the host cell is initiated by fungal adherence to the cell surface, which generates an uptake signal that may induce its cytoplasmic internalization. Once this is accomplished, some fungi are able to alter the host cytoskeletal architecture, as manifested by a rearrangement of microtubule and microfilament proteins, and this can also induce epithelial host cells to become apoptotic. It is possible that fungal pathogens induce modulation of different host cell pathways in order to evade host defences and to foster their own proliferation. For a number of pathogens, the ability to bind ECM glycoproteins, the capability of internalization and the induction of apoptosis are considered important factors in virulence. Furthermore, specific recognition between fungal parasites and their host cell targets may be mediated by the interaction of carbohydrate-binding proteins, e.g., lectins on the surface of one type of cell, probably a parasite, that combine with complementary sugars on the surface of host-cell. These interactions supply precise models to study putative adhesins and receptor-containing molecules in the context of the fungus-host interface. The recognition of the host molecules by fungi such as Aspergillus fumigatus, Paracoccidioides brasiliensis and Histoplasma capsulatum, and their molecular mechanisms of adhesion and invasion, are reviewed in this paper.

Comparative evaluation of the CD4+CD8+ and CD4+CD8- lymphocytes in the immune response to porcine rubulavirus

The porcine immune system is unique in the expression of CD4+CD8+ (double-positive, DP) lymphocytes. These cells have been associated with immunological memory due to their gradual increase with age, the expression of memory phenotype and their ability to respond to recall viral antigen. This work analyzes the biological function of CD4+CD8- and CD4+CD8+ lymphocytes in the immune response to porcine rubulavirus (PRv). CD4+CD8- cells isolated from pigs 3 weeks after infection with porcine rubulavirus proliferated in response to homologous virus and generated lymphoblasts which were predominantly of the CD4+CD8+ phenotype, whereas stimulation with mitogen induced proliferation but did not switch the phenotype. CD4+CD8- lymphocytes isolated after 10 weeks of infection proliferated in response to phytohemagglutinin (PHA) but did not proliferate in response to homologous virus and did not change their phenotype, whereas CD4+CD8+ lymphocytes proliferated in response to PHA and to viral antigen. The cytokine profile of both lymphocyte populations showed the presence of IL-2 and IL-10 transcripts, quantitation demonstrated that CD4+CD8+ cells expressed mainly IL-10, whereas CD4+CD8- lymphocytes expressed primarily IL-2. Our results show that CD4+CD8- lymphocytes in the early phase of porcine rubulavirus infection can be converted to double-positive cells expressing IL-10 in an antigen-dependent manner, and that CD4+CD8- T-cells late in infection do not acquire CD8.

[Advances in the study of immunopathology in atopic disorders]

The atopic diseases are mediated by type I hypersensitivity. These disorders are multifactorial, although, the inherency is probably the most important cause. The disregulation of the Th1/Th2 immune response is one of the predominant factors on the generation and maintenance on the atopic process. We analyze the mechanisms of the regulation of the response Th1/Th2, the recent theories of the disregulation on this response as an etiology, the soluble factors as cytokines, chemokines and their receptors, surface cell markers and transcriptional factors recently mentioned to be important on this disregulation mechanism. Otherwise, we propose some general considerations and perspectives.

O-Glycosylation in sprouting neurons in Alzheimer disease, indicating reactive plasticity

Reactive plasticity, including axonal and dendritic sprouting and reactive synaptogenesis, has been proposed to contribute to the pathogenesis of several neurological disorders. This work was aimed at identifying the possible role of protein glycosylation in the brain from patients with Alzheimer disease (AD), using lectin histochemistry, as determinants of reactive plasticity. Results indicate an increase in the production of cryptic O-glycosidically linked proteins (NeuAcalpha2,6 Galbeta1,3GalNAcalpha1,0 Ser/Thr or sialyl-T-antigen) in neuritic sprouting in AD brains as determined by positive labeling with Amaranthus leucocarpus (ALL, T-antigen-specific) and Macrobrachium rosenbergii (MRL, specific for NeuAc5,9Ac2) lectins. Immunohistochemistry indicated that lectin staining was specific for the synaptic sprouting process (meganeurites) in AD. These results were confirmed using anti-synaptophysin and anti-GAP 43 antibodies, which recognized meganeurites and dystrophic neurites around amyloid-beta deposits. In normal control brains, labeling with the aforementioned lectins was restricted to microvessels. Control experiments with neuraminidase-treated brain samples revealed positivity to the lectin from Arachis hypogaea (PNA), which is specific for galactose. Our results suggest specific O-glycosylation patterns of proteins closely related to neuronal plasticity in AD.

Hevein, an allergenic lectin from rubber latex, activates human neutrophils' oxidative burst

Hevein is an N-acetyl-D-glucosamine (GlcNAc) specific lectin that has been hypothesized to participate in the IgE-mediated allergic reactions in patients with latex allergy. In this work we assessed the specificity and biological effect of hevein purified from rubber latex on human leukocytes, using epifluorescence microscopy and flow cytometry. Purified human granulocytes were stimulated in vitro with hevein, and production of oxidative radicals was measured by reduction of nitroblue tetrazolium formazan. Histochemical staining and flow cytometry showed that hevein recognizes specifically monocytes (CD14+) and neutrophils (CD16+), but not lymphoid cells. Hevein induced oxidative response in purified granulocytes; this effect was 1.3-1.5-fold higher than the effect observed with the lectin WGA (wheat germ agglutinin), or other lectins with different sugar specificity. The induced reactions and cellular recognition by hevein were inhibited with GlcNAc and its oligomers; as well as by glycoproteins containing tri-and tetra-antennary N-glycosydically linked glycans. Our findings suggest that neutrophils are the main target for latex hevein; this lectin induces production of oxidative radicals, which seem to play an important role in tissue damage during latex allergy.

Chemical characterization of the lectin from Amaranthus leucocarpus syn. hypocondriacus by 2-D proteome analysis

In this work, we characterized chemically the N-acetyl-D-galactosamine specific lectin from Amaranthus leucocarpus syn hypocondriacus lectin (ALL). It is a dimeric glycoprotein composed by three isoforms with pl at 4.8, 4.9, and 5.2. Circular dichroism analysis indicated that the secondary structure of ALL contains 45% of \bibeta-sheet and 5% of \bialpha-helix. Amino acid sequence of the purified lectin and its isoforms was determined from peptides obtained after trypsin digestion by MALDI-TOF (Matrix assisted laser desorption ionization-time of flight). The tryptic peptides prepared from the purified lectin and the three isoforms showed different degrees (80 to 83%) of identity with the amino acid sequence belonging to a previously described high nutritional value protein from A. hypocondriacus not shown at the time to be a lectin. Furthermore, analysis of tryptic peptides obtained from ALL previously treated with peptide N-glycosidase, revealed a 93% identity with the aforementioned protein. Presence of N-glycosidically linked glycans of the oligomannosidic type and, in minor proportion, of the N-acetyllactosaminic type glycans was determined by affinity chromatography on immobilized Con A.

The hydrophobic character of peanut (Arachis hypogaea) isoagglutinins

Peanut seed lectin (PNA) is widely used to identify tumor-specific antigens on the eukaryotic cell surface. In this work PNA was purified by affinity chromatography, using a column containing glutaraldehyde-treated human erythrocytes, whereas PNA isoforms were purified by hydrophobic interaction chromatography using Phenyl-Sepharose. The affinity-purified PNA and its isoforms consist of four equal subunits of 24.5 kDa each, all of which agglutinated human sialidase-treated erythrocytes equally well; however, differences in their relative thermostabilities and sugar specificities for lactose were observed. Fractions PNA-I and PNA-II possess higher affinity for lactose residues than the more hydrophobic isoforms III and IV. These findings suggest that the differences observed in PNA isoagglutinins are due to hydrophobic regions of the protein that influence the three-dimensional organization of the molecule as well as its thermal stability and sugar specificity.

Impairment of Leishmania mexicana phagocytosis in peritoneal macrophages induced by Amaranthus leucocarpus lectin

The lectin from Amaranthus leucocarpus (ALL) is specific for N-acetyl-D-galactosamine and inhibits phagocytosis of Leishmania mexicana promastigotes in Balb/c mice peritoneal macrophages by 38%. The lipophosphoglycan (LPG) purified from L. mexicana inhibits penetration of promastigotes into peritoneal macrophages by 31%; interestingly, treatment of macrophages with both, ALL and LPG, inhibits phagocytosis of promastigotes by 72%, confirming that ALL induces modification of the macrophage's phagocytic activity by a different route than mannose or C3b receptors. The Inhibitory effect of ALL was time-dependent. N-acetyl-D-galactosamine (GalNAc) or O-glycosidically linked glycoproteins modified macrophage phagocytosis of Leishmania. These results suggest that macrophage membrane glycoproteins, possessing constitutive GalNAc, can influence the signaling pathways used by this intracellular parasite to infect.

Chemical characterization of the lectin from the freshwater prawn Macrobrachium rosenbergii (De Man) by MALDI-TOF

The serum of the freshwater prawn contains a sialic acid specific lectin (MrL) that agglutinates erythrocytes from rat and rabbit, as well as some Gram negative and positive bacterial strains. In this work, we performed the chemical characterization of the MrL purified by affinity chromatography on stroma from rat erythrocytes and by ion exchange chromatography. In its active form, MRL is a dimeric glycoprotein with 9.5 kDa per subunit. The amino acid sequence of the lectin was deduced from peptides obtained after trypsin treatment by matrix-assisted laser desorption ionization mass spectrometry-time of flight analysis (MALDI-TOF). The predicted amino acid sequence of the lectin showed 54% homology with the hyperglycemic hormone from Macrobrachium rosenbergii. It also showed homology with the variable region of the human immunoglobulin kappa (22%) and lambda (27%) light chains. The lectin is a glycoprotein with 11% (w/w) carbohydrate content and is constituted by Gal, Man, GlcNAc, GalNAc and NeuAc in a molar ratio of 4:3:2:1:0.6. The primary structure of the carbohydrate chains of the lectin from the freshwater prawn was determined by affinity chromatography of MrL-glycopeptides on Con A and LCA lectin columns, which indicated that the main carbohydrate chains conforming the lectin are N-glycosidically linked. Man3 GlcNAc2.1 oligosaccharides were the most abundant structures with 57%) followed by Gal1.3 Man3 GlcNAc2.8 with 24%. Our results suggest that the freshwater prawn possess a lectin in the hemolymph plasma, related to those from the immunoglobulin superfamily.

Quantification of lectin in freshwater prawn (Macrobrachium rosenbergii ) hemolymph by ELISA

An enzyme-linked immunoabsorbent assay was developed to quantify the lectin present in the hemolymph of the freshwater prawn Macrobrachium rosenbergii. This method involves the use of murine monoclonal IgG1 with kappa light chain (designated as 3G1) antibodies raised against the purified lectin, the assay that we developed recognized as little as 30 ng/ml of lectin, and was used to measure the lectin concentration in animals at different maturation stages. The highest concentration of lectin was identified in the hemolymph from post-larval prawns and the lowest in molt stage adult animals. The hemagglutination activity of the lectin was four-fold higher in adult than in juvenile specimens, although in all cases N-acetylated sugar residues, such as N-acetyl-D-glucosamine, N-acetyl-D-galactosamine, and N-acetyl-D-neuraminic acid were inhibitors of the lectin activity, suggesting that lectin plays a role in the transport of N-acetylated sugar in juvenile prawns. Our results indicate that lectin concentration and hemagglutinating activity could be influenced by developmental conditions of the freshwater prawn.

Differential expression of sialic acid on porcine organs during the maturation process

Sialylated structures play important roles in cell communication, and change in a regulated manner during development and differentiation. In this work, we report the main glycosidic modifications that occur during the maturation of porcine tissues, involving the sialylation process as determined with lectins. Sialic acids were identified at several levels in a broad range of cell types of nervous, respiratory, genitourinary and lymphoid origin. Nevertheless, the most contrasting was the type of glycosidic linkage between 5-N-acetyl-neuraminic acid (Neu5Ac) and galactose (Gal) expressed in central nervous system (CNS). Newborn CNS abundantly expressed Neu5Acalpha2,3Gal, but weakly or scarcely expressed Neu5Acalpha2,6Gal/GalNAc. Maturation of CNS induced drastic changes in sialic acid expression. These changes include decrease or complete loss of NeuAcalpha2,3Gal residues, mainly in olfactory structures and brain cortex, which were replaced by their isomers Neu5Acalpha2,6Gal/GalNAc. In the brain cortex and cerebellum, the increase of Neu5Acalpha2,6Gal/GalNAc molecules was paralleled by an increase of 5-N-acetyl-9-O-acetyl-neuraminic acid (Neu5,9Ac2). In addition, terminal Gal and N-acetyl-D-galactosamine (GalNAc) residues also increased their expression in adult CNS tissues, but this was more significant in structures forming the encephalic trunk. Our results show that sialylation of porcine CNS is finely modulated throughout the maturation process.

Identification of lectin isoforms in juvenile freshwater prawns Macrobrachium rosenbergii (DeMan, 1879)

From the serum of juvenile freshwater prawns, we isolated by affinity chromatography on glutaraldehyde-fixed rat erythrocytes stroma, immobilized in Sephadex G-25, a sialic acid specific lectin of 9.6 kDa per subunit. Comparative analysis against adult organisms purified lectin, by chromatofocusing, showed that the lectin from juvenile specimens is composed by four main isoforms with a pI of 4.2, 4.6, 5.1, and 5.6, whereas the lectin from adults is eluted at pH 4.2. The amino acid composition of the lectin obtained from adult and juvenile stages suggest identity, but the compositions are not identical since a higher content of carbohydrates was found in the lectin from younger organisms. The freshwater prawn lectin showed specificity toward N-acetylated amino sugar residues such as GlcNAc, GalNAc, Neu5Ac and Neu5,9Ac; but in juvenile organisms the lectin showed three times less hemagglutinating activity than the lectin from adults. Both lectins agglutinated rat, rabbit and chicken erythrocytes, indicating that Neu5,9Ac in specific O-glycosydically linked glycans seems to be relevant for the interaction of M. rosenbergii lectins with their specific cellular receptor. Our results suggest that the physicochemical characteristics of the lectin from the freshwater prawn are regulated through maturation.

Isolation of the receptor for Amaranthus leucocarpus lectin from murine naive thymocytes

From murine medullary thymocytes we purified the receptor for the Amaranthus leucocarpus lectin (ALL) using a complex with the biotin-labeled lectin and avidin-agarose as the affinity matrix. Most ALL(+)thymocytes (83%) are naive cells with the CD4(+)CD8(-)CD45RB(+)phenotype. The receptor for this lectin is a 70 kDa glycoprotein that contains 20% of sugar by mass. It is constituted mainly by aspartic and glutamic acids, serine, proline, and glycine; its glycosidic portion contains mainly O-glycosidically linked glycans with Gal, GalNAc and NeuAc residues as well as one N-glycosidically linked glycan per molecule. Ionic strength chromatography revealed that the ALL-thymocyte receptor (ALLTr) is made up by three isoforms, which possess similar amino acid composition but show slight differences in their sugar composition. The N-terminal amino acid residues are blocked both in the receptor and its purified isoforms. Analyses of the receptor's peptides, obtained by trypsin digestion with MALDI-TOF (matrix assisted laser desorption ionization-time of flight), were compared with the relative values obtained from the NCBInr (Swiss-Prot 10/01/99) database. Our results indicate that the peptides of ALLTr show low homology (<17%) with the human KIIA protein, the Fas-associated death domain protein, and the transforming growth factor-beta type II receptor. Our results suggest that the ALL thymocyte receptor could be considered a novel phenotypic marker specific for naive T cells.

Purification and characterization of an adhesin from Pasteurella haemolytica

We purified an adhesin from Pasteurella. haemolytica by affinity chromatography using glutaraldehyde treated rabbit erythrocytes stroma. The adhesin is a protein of 68 kDa, as determined by SDS-PAGE, and the most abundant amino acids constituting this protein were Gly, Ser, Glx, and Ala, and low concentrations of Cys, Met, and Tyr residues were also found. The N-terminal sequence of the adhesin is ANEVNVYIYKQPYLI. No carbohydrate residues were detected. The adhesin agglutinated rabbit erythrocytes but when the latter were desialylated or pronase treated the agglutinating activity was abolished. The agglutinating activity of the adhesin was inhibited with N-acetyl-D-glucosamine (GlcNAc), and in a lesser degree with N-acetyl-neuraminic acid (NeuAc). GalNAc, N-glycolyl-neuraminic acid, N-deacetylated GlcNAc, or neutral sugars do not modify the activity of the adhesin. The equatorial -OH on C4 and the NH-acetylated group on C2 from GlcNAc, as well as the 4-OH and NH-acetylated group on C5 from NeuAc seem to be responsible for the interaction with the adhesin. The protein is divalent cation-dependent and thermolabile. As for the agglutinating activity, the adhesion of P.haemolytica to tracheal cell-cultures was inhibited by GlcNAc, NeuAc or the purified adhesin, strongly suggesting that the P.haemolytica adhesin plays an important role in infection.

Purification and characterization of the hemagglutinin-neuraminidase of Porcine rubulavirus LPMV

The Hemagglutinin-Neuraminidase (HN) from the LPMV strain of Porcine rubulavirus was purified from virions by ultracentrifugation in a continuous 20-60% sucrose gradient and by ion exchange chromatography. The HN is a glycoprotein of 66 kDa constituted by 50.5, 13.3 and 13.6% of non polar, uncharged polar, and charged polar amino acids, respectively. The HN contains 4% of carbohydrates, its glycannic portion is constituted by Man, Gal, GlcNAc, GalNAc, and Neu5Ac in 3:3:4:1:1 molar ratios. The HN possesses hemagglutinating activity in the presence of erythrocytes from several animal species, including human ABO, and treating the erythrocytes with neuraminidase or pronase abolishes this activity. The binding specificity of the purified HN was determined by hapten inhibition assays, indicating that the hemagglutinating activity of the HN is specific for sialic acid and Neu5Acalpha2,3Gal-containing structures.

A comparative study on the purification of the Amaranthus leucocarpus syn. hypocondriacus lectin

Amaranthus leucocarpus lectin is a homodimeric glycoprotein of 35 kDa per sub-unit, which interacts specifically with N-acetyl-galactosamine. In this work, we compared different glycoproteins that contain Galbeta1-3 GalNAcalpha1-3 Ser/Thr or GalNAcalpha1-3 Ser/Thr in their structure as ligands to purify the A. leucocarpus lectin. From the glycoproteins tested, fetuin was the most potent inhibitor of the hemagglutinating activity and the better ligand for lectin purification; however, the use of desialylated stroma from erythrocytes represented the cheapest method to purify this lectin. O-linked glycans released from the glycoproteins used as affinity matrix and those from different erythrocytes were less inhibitory than parental glycoproteins. The NH2-terminal of the lectin is blocked; moreover, this is the only example of a lectin isolated from this genus to be a glycoprotein. Analysis of the glycoprotein sequences with inhibitory activity for the lectin, showed a different pattern in the O-glycosylation, which confirms that A. leucocarpus lectin recognizes conformation and, probably, distances among O-linked glycans moieties.

Characterization of GP39-42 and GP24 antigens from Taenia solium cysticerci and of their antigenic GP10 subunit

Diagnosis of neurocysticercosis is performed by Western blotting with an enriched fraction of glycoproteins (LLGP). GP39-42 and GP24 are immunodominant antigens. These antigens were electroeluted and characterized by biochemical methods. When GP39-42 or GP24 were reduced, a band of 10 kDa (named GP10) appeared; this band was also analyzed. The most abundant amino acids in the three GPs were lysine, phenylalanine, asparagine, glycine, and leucine. The amino terminal portion was sequenced, and the following order was obtained for the three GPs: EKNKPKNVAXSTKKGYEYVXEF. The glycan portion was 8.4%, 18.2%, and 18.3% in GP39-42, GP24, and GP10, respectively. The three GPs contained mannose, N-acetyl-D-glucosamine, and galactose. GP39-42 and GP24 seem to be oligomeric forms of GP10. When reduced LLGP was reacted with samples obtained from patients with neurocysticercosis or pigs with cysticercosis, a band corresponding to GP10 was always observed. Furthermore, hyperimmune serum from rabbits immunized with GP39-42 or with GP24 recognized GP10 as well as GP39-42 and GP24. The data obtained in this paper suggest that GP10 might be a useful tool for diagnosis.

Identification of immunodominant antigens in Mexican strains of Trypanosoma cruzi

Chagas disease represents an important public health problem. In Mexico most studies have been performed using Trypanosoma cruzi' antigens extracted from strains of other geographical origins. This work was aimed at developing a reactive antigen to perform serological diagnosis of Chagas' disease, using Mexican T. cruzi strains. We prepared antigenic extracts from epimastigotes, trypomastigotes and sphaeromastigotes of three Mexican strains. Parasites homogenate was obtained by lysis and sonication, solubilized proteins were analyzed by SDS-PAGE, Western-blot assays, and ELISA to determine the reactivity against sera from chagasic reference serum and chagasic and leishmaniasic patients and healthy donors. Western Blot profiles revealed, with the reference serum, eleven main components between 212 to 25 kDa; however, five bands corresponding to 74, 44, 31, 25 and 18 kDa antigens were recognized by the T. cruzi reactive sera from Mexican chagasic patients, which did not cross-react with Leishmania mexicana. Antigens from the Tequesquitengo strain yielded the best reactivity in the enzymatic immunoassay, thus enabling us to propose their use for serodiagnoses of Chagas' disease in Mexico.

Diabetes knowledge and its determinants in a Mexican population

PURPOSE

The purpose of this study was to measure the level of diabetes knowledge in a representative group of Mexican individuals with diabetes and to identify the factors that influence it.

METHODS

A validated questionnaire was administered to 570 outpatients; 11.2% had Type 1 diabetes, 36.4% had Type 2 diabetes treated with insulin, and 52.2% had Type 2 diabetes treated with oral agents. Samples for HbA1c determination also were obtained.

RESULTS

The percentage of correct answers in each section of the questionnaire was low. Type 1 patients had the highest scores, followed by the insulin-treated Type 2 patients; those with chronic complications also had high scores. Educational background, attendance at diabetes courses, age, and HbA1c concentration were the main predictors of knowledge. Attendance at courses was influenced by the severity of the disease.

CONCLUSIONS

The amount of patient knowledge about diabetes-related issues was low in this representative Mexican population. The educational efforts were focused on those with the worst metabolic control and/or with diabetes complications.

Collagen degrading activity associated with Mycobacterium species

BACKGROUND

The mechanism of Mycobacterium tuberculosis penetration into tissues is poorly understood but it is reasonable to assume that there is a contribution from proteases capable of disrupting the extracellular matrix of the pulmonary epithelium and the blood vessels. A study was undertaken to identify and characterise collagen degrading activity of M tuberculosis.

METHODS

Culture filtrate protein extract (CFPE) was obtained from reference mycobacterial strains and mycobacteria isolated from patients with tuberculosis. The collagen degrading activity of CFPE was determined according to the method of Johnson-Wint using 3H-type I collagen. The enzyme was identified by the Birkedal-Hansen and Taylor method and its molecular mass determined by SDS-PAGE and Sephacryl S-300 gel filtration chromatography using an electroelution purified enzyme.

RESULTS

CFPE from Mycobacterium tuberculosis strain H37Rv showed collagenolytic activity that was four times higher than that of the avirulent strain H37Ra. The 75 kDa enzyme responsible was divalent cation dependent. Other mycobacterial species and those isolated from patients with tuberculosis also had collagen degrading activity.

CONCLUSIONS

Mycobacterium species possess a metalloprotease with collagen degrading activity. The highest enzymatic activity was found in the virulent reference strain H37Rv.

[Mechanisms of pathogenicity and adhesion in Pasteurella haemolytica]

Pasteurella haemolytica is one of the bacteria most commonly isolated from pneumonic cases in ruminants. Some of the mechanisms and factors involved in the pathogenesis of the disease are partially documented; and the early stages of bacterial colonization have not been totally clarified. Therefore a review is presented in this paper, particularly related with the mechanisms of bacterial pathogenicity responsible of pulmonary damage to ruminants, as well as a detailed analysis of the adherence process.

Effects of concanavalin A on protein-C activity

Concanavalin A interacts specifically with the oligosaccharides from protein-C and modifies its anticoagulant activity. The lectin activates the protein-C activity in a dose dependent manner as demonstrated by in vitro and in vivo assays. Concanavalin A at low concentration (0.1 to 2 microg/mL) induces an increase on the catalytic activity of protein-C; at higher concentrations (5 to 20 microg/mL), the catalytic activity returns to the baseline. The effect of concanavalin A was prevented by incubating the protein-C with alpha-methyl-mannoside or by treating the purified protein-C with alpha-mannosidase; furthermore, cleavage of mannosidic residues diminishes its catalytic activity. Our results indicate that the oligomannosidic portion of protein-C participates in the regulation of the catalytic activity of this protein.

Isolation of a proliferation inhibitor factor from uterine myomatosis fibroblasts

In this work, we report the isolation of a factor from the culture supernatant of confluent fibroblasts from human cervix with the diagnosis of uterine myomatosis. This factor possesses the capacity to inhibit the proliferation of normal fibroblasts. The proliferation inhibitor factor (PIF) was purified from the culture supernatant by precipitation with 80% ammonium sulfate, and by molecular sieve chromatography. Our results indicate that PIF is a protein of 23 kDa, which is highly sensitive to trypsin treatment, and is thermolabile, since temperatures equal to, or above, 60 degrees C eliminate the protein activity in 15 to 20 min. Western blot analyses identified no cross reactions of the purified PIF with TGF-alpha, TNFalpha, IFNgamma, or IL-1beta, suggesting that PIF is a new protein belonging to the group of factors secreted by fibroblasts able to inhibit cellular proliferation.

Relevance of sialoglycoconjugates in murine thymocytes during maturation and selection in the thymus

Differentiation of most T lymphocytes is characterized not only by the variable expression of CD4/CD8 coreceptor molecules and increased surface density of the T cell antigen receptor, but also by changes in the glycosylation pattern of cell surface glycolipids or glycoproteins. In this work we evaluated the changes in the sialylation pattern in thymus sections from normal and dexamethasone treated mice. We used sialic acid specific lectins, such as Sambucus nigra agglutinin (SNA, NeuAcalpha2,6-Gal specific) and Maackia amurensis agglutinin (MAA, NeuAcalpha2,3-Gal specific). Our results indicate that the sialylation pattern was modified during the maturation process of thymic cells. The immature CD4-CD8- and CD4+CD8+ cortical thymocytes were recognized by SNA, whereas the mature single positive (CD4+ or CD8+) medullary cells, preferentially bound MAA lectin. However, in the corticomedullary region we found not only SNA+ cells, but also MAA+ cells. In the thymus of dexamethasone treated mice, the clusters of thymocytes undergoing apoptosis in the cortex were characteristically stained by SNA. These results suggest that in the initial stages of the differentiation pathway, a great number of thymocytes express an alpha2,6 linked sialic acid on their surface and as they progress to more mature stages there is a change in the sialylation pattern to alpha2,3 linked sialic acids probably due to a regulated expression of different sialyltransferases, which could be modulated by the thymic microenvironment.

Altered glycosylation pattern of proteins in Alzheimer disease

Post-translational modifications due to glycosylation of proteins in human brains from patients with Alzheimer disease (AD) were analyzed using lectin histochemistry. Results indicate a significant increase in the production of O-glycosylated (containing Galbeta1,3GalNAc alpha1,0 Ser/Thr or GalNAc alpha1,0 Ser/Thr) proteins in neuritic plaques and neurofibrillary tangles which are the major histopathological hallmarks of AD brains. These alterations were determined by positive labelling with lectins obtained from Amaranthus leucocarpus (ALL) and Macrobrachium rosenbergii (MRL) respectively. Immunohistochemistry indicated that the lectin-staining labelled specifically both neurofibrillary tangles and neuritic plaques. In contrast, lectins labelling was restricted to microvessels in normal control brains. These results provide evidence that modifications of the specific glycosylation patterns are closely related with the presence of the hallmark lesions of this disease, suggesting that an abnormal enzymatic processing of proteins may be an early event in the neuronal degeneration which characterises AD.

Identification of major glycoconjugates from Mycobacterium bovis culture filtrate by biotin-hydrazide labeling

To identify Mycobacterium bovis glycoproteins, carbohydrates present in a delipidized M. bovis culture filtrate protein extract were biotin-hydrazide labeled. 11 carbohydrate-containing protein with a molecular weight of 15-, 19-, 25-, 32-, 35-, 39-, 42-, 48-, 52-, 58-, and 62-kDa were detected. The 52- and 32-kDa protein were deglycosylated by endoglycosidase-F.

Interaction of murine macrophage-membrane proteins with components of the pathogenic fungus Histoplasma capsulatum

The interaction of macrophage-membrane proteins and histoplasmin, a crude antigen of the pathogenic fungus Histoplasma capsulatum, was studied using murine peritoneal macrophages. Membrane proteins were purified via membrane attachment to polycationic beads and solubilized in Tris-HCl/SDS/DTT/glycerol for protein extraction; afterwards they were adsorbed or not with H. capsulatum yeast or lectin binding-enriched by affinity chromatography. Membrane proteins and histoplasmin interactions were detected by ELISA and immunoblotting assays using anti-H. capsulatum human or mouse serum and biotinylated goat anti-human or anti-mouse IgG/streptavidin-peroxidase system to reveal the interaction. Results indicate that macrophage-membrane proteins and histoplasmin components interact in a dose-dependent reaction, and adsorption of macrophage-membrane proteins by yeast cells induces a critical decrease in the interaction. Macrophage-membrane glycoproteins with terminal D-galactosyl residues, purified by chromatography with Abrus precatorius lectin, bound to histoplasmin; and two bands of 68kD and 180kD of transferred membrane protein samples interacted with histoplasmin components, as revealed by immunoblot assays. Specificity for beta-galactoside residues on the macrophage-membrane was confirmed by galactose inhibition of the interaction between macrophage-membrane proteins and histoplasmin components, in competitive ELISA using sugars, as well as by enzymatic cleavage of the galactoside residues.

Immunity to porcine rubulavirus infection in adult swine

The immune response against the porcine rubulavirus was analyzed in experimentally infected adult pigs. High titers of virus neutralizing and hemagglutinating inhibitory antibodies were identified in infected animals. The antibody specificity was directed towards HN, M, and NP rubula virion proteins; immunodominance of HN proteins was demonstrated. Peripheral blood mononuclear cells from infected, but not from non-infected pigs proliferated in vitro in response to virus antigenic stimuli, showing a bell-shaped plot with the highest peak at 5 weeks post-infection. Virus-induced lymphoblasts expressed CD4+ CD8+ phenotype, whereas lectin-induced lymphoblasts were mainly identified as CD4+ CD8- cells. Phenotype analysis of freshly prepared PBMC revealed increased number of both monocytes (PoM1+) and total T lymphocytes (CD2+) early during infection, with reduced values of B lymphocytes at 4 weeks post-infection. Decrease in CD4+ CD8- blood cells was observed at 3 weeks post-infection, whereas both CD4- CD8+ and CD4+ CD8+ cells increased 1 and 4 weeks post-infection, respectively. This work discusses the relevance of CD4+ CD8+ T cells in the control of porcine rubulavirus infection.

Isolation of the receptor for Amaranthus leucocarpus lectin from murine peritoneal macrophages

The receptor for Amaranthus leucocarpus lectin from CD-1 resident macrophages was purified with affinity chromatography with biotin labeled A. leucocarpus lectin and using avidin-agarose as affinity matrix. The receptor is a glycoprotein of 70 kDa that contains 18% of sugar by weight; it is mainly composed of galactose and N-acetyl-D-galactosamine in its saccharidic portion, and lacks sialic acid; the protein is rich in glycine, serine and alanine and lacks cysteine residues. The amino terminus of the receptor is blocked. By ionic strength chromatography on a mono P column in anionic form we purified three isoforms from the affinity purified receptor, each showing quantitative differences in glycosylation. The A. leucocarpus lectin receptor is identified only in resting, not activated, macrophages suggesting that it plays a role in activation mechanisms of macrophages.