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A Campos-Neto

Publications and source records attributed to A Campos-Neto.

54 records · Page 3Linked to original sources
PubMed1986

IgA-affinity purification and characterization of the lectin jacalin.

We describe the use of IgA-Sepharose 4B affinity chromatography to purify the lectin jacalin from saline extracts of Artocarpus integrifolia L. seeds. Elution with 0.8 M D-galactose provides 10-15 mg lectin/50 mg seed protein. Jacalin behaved like a single component on immunoelectrophoresis and a single, somewhat diffuse band was obtained by polyacrylamide gel electrophoresis (PAGE) at pH 4.5. A single peak corresponding to an apparent molecular weight of 43 kDa was obtained by gel filtration on Sephadex G-75 (10 mM phosphate buffered saline (PBS), pH 7.4). On SDS-PAGE +/- 2-mercaptoethanol two bands of apparent molecular weights 11.8 and 14.7 kDa were detected. Jacalin behaved like a protein of apparent molecular weight of 13-14 kDa on Sephadex G-50 eluted with PBS containing 0.2% SDS. These data indicate that the jacalin molecule consists of 3-4 non-identical polypeptide subunits not connected by disulfide bridges. The amino acid composition of IgA affinity-purified jacalin (mol/405 mol amino acids) is Lys (24), His (5), Arg (4), Trp (6), Asx (36), Thr (35), Ser (48), Glx (31), Pro (18), Gly (53), Ala (13), Val (25), Met (3), Ile (23), Leu (25), Tyr (30), Phe (26), which corresponds to a molecular weight of 44.163 kDa.

Amino Acids↗
PubMed1985

Purification of tissue forms (Amastigotes) of Trypanosoma cruzi by immunoaffinity chromatography.

A rapid and simple method for the purification of amastigotes of Trypanosoma cruzi from spleens of infected mice is described. A protein A-Sepharose 4B immunoadsorbent column bound with antisera to epimastigotes of T. cruzi was used to purify the tissue forms of this parasite. Host cells and debris are not retained, and parasites can be eluted in high yields and purity. Studies of surface glycoproteins and glycolipids of the purified amastigotes with 18 lectins of various specificities revealed the presence on the parasites of receptors for N-acetylglucosamine, N-acetylgalactosamine, D-galactose, and D-mannose binding lectins.

Agglutination↗
PubMed1985

Jacalin: an IgA-binding lectin.

We previously reported that seeds of Artocarpus integrifolia (jackfruit) contain a lectin, which we call jacalin, that is both a potent T cell mitogen and an apparently T cell-independent activator of human B cells for the secretion of immunoglobulins. During the above experiments we noted a massive precipitation in cell cultures stimulated with greater than or equal to 100 micrograms of lectin. In this paper, we show that the precipitate is formed after the interaction of jacalin and the serum protein added to the culture medium. More importantly, we demonstrate that IgA is probably the major serum constituent precipitated by the lectin and that no IgG or IgM can be detected in the precipitates. In secretions such as colostrum, IgA is the only protein precipitated by jacalin. On the basis of this specificity we describe a simple and reliable affinity chromatography procedure for the purification of both human serum and colostrum IgA. Jacalin is a D-Gal binding lectin and should be a useful tool for studying of serum and secretory IgA.

Animals↗
PubMed1985

Hypergammaglobulinaemia in Leishmania donovani infected hamsters: possible association with a polyclonal activator of B cells and with suppression of T cell function.

Studies were carried out on the mechanisms by which B lymphocytes are polyclonally activated to secrete antibodies during visceral leishmaniasis. Crude extracts of Leishmania donovani, the aetiological agent of this disease, of Leishmania mexicana amazonensis, the etiological agent of cutaneous leishmaniasis, and of Herpetomonas muscarum, a related non-pathogenic organism, all contain components which cause strong in vitro polyclonal activation of hamster spleen cells leading to the production of antibodies. However, in vivo, only hamsters infected with L. donovani develop hypergammaglobulinaemia due to B cell polyclonal activation. Hamsters injected with the crude extracts of leishmania or infected with L. mexicana amazonensis do not manifest these alterations in their B cell response. Furthermore spleen cells of hamsters infected with L. donovani became unresponsive to stimulation with the T cell mitogen phytohaemagglutinin (PHA) by day 10 of infection, whereas their response to concanavalin A (Con A) was preserved. The decreased lymphocyte response to PHA coincided with the augmentation of the PFC/spleen ratio. In contrast, spleen cells from hamsters infected with L. mexicana amazonensis, responded normally to both mitogens throughout the course of infection. These results suggest that the hypergammaglobulinaemia present in visceral leishmaniasis may be the consequence of an inbalance of regulatory T cells, possibly associated with a direct stimulation of hamster B cells by L. donovani components.

Animals↗
PubMed1985

Cellular cytotoxicity of Trypanosoma cruzi mediated by different classes of antibody and by lectins.

We have investigated the nature of the ligand involved in antibody-dependent cellular cytotoxicity (ADCC) of human leukocytes to epimastigotes of Trypanosoma cruzi. Purified anti-T. cruzi IgG was highly efficient in mediating ADCC whereas IgM mediated the killing of this parasite poorly even at high concentrations. The presence of the Fc portion on the IgG molecule seems to be necessary since F(ab')2 derived from anti-T. cruzi IgG did not mediate ADCC. We also present evidence suggesting that the mediator, aside from promoting the interaction between the effector and target cells, may play a functional role in triggering target destructions by the effector cells. This conclusion is based on results of experiments in which lectins capable of binding to both leukocytes and parasite were used as mediators of cellular cytotoxicity. The lectin concanavalin A could readily replace IgG for human leukocyte killing of T. cruzi. In contrast, lectins from Lens culinaris, Triticum vulgaris, Aaptos papillata and Bandeirae simplicifolia although capable of interacting with leukocytes and T. cruzi, did not mediate the cellular cytotoxicity of the parasites. The specific cellular mechanism of parasite killing, i.e. phagocytosis and or extracellular lysis, remains to be determined.

Adult↗
PubMed1985

Mesangial proliferative glomerulonephritis associated with progressive amyloid deposition in hamsters experimentally infected with Leishmania donovani.

In the present work, 42 golden hamsters (Mesocricetus auratus) were infected by intracardiac injection of 5 X 10(6) amastigote forms of Leishmania donovani. Another group of 28 animals served as uninfected controls. Six hamsters of the infected group and four hamsters of the control group were selected randomly and sacrificed at Days 7, 14, 21, 28, 35, 42, and 49 after inoculation. The kidneys were studied by light microscopy, immunofluorescence and electron microscopy. The levels of serum and urinary immunoglobulins were determined. None of the control hamsters had kidney lesions. Light-microscopically the kidneys of infected hamsters showed a marked mesangial proliferation from Day 7 after infection. These changes were more pronounced at Day 21, when a discrete infiltration of mononuclear cells was frequent. These glomerular changes diminished after Day 28 and were replaced by deposits of amyloid. In the beginning these deposits were in the mesangium and progressively became more extensive, involving capillary loops, Bowman's capsule, and interstitium. The immunofluorescence study showed L donovani antigens and hamster immunoglobulins, primarily in the mesangial areas, by Days 7-14 after infection. These deposits extended into contiguous loops from Day 21 to Day 28. In the last 2 weeks the fluorescent staining for L donovani antigens remained intensely positive, whereas the staining for hamster immunoglobulins became moderate to slightly positive. The ultrastructural study revealed mesangial proliferation, mesangial and paramesangial electron-dense deposits, and amyloidosis in the glomeruli of infected animals. The serum immunoglobulins increased from Day 7 after infection, reaching a peak at Day 21 and falling thereafter until Day 49 to near control values. Immunoglobulins were detected in the urine of infected hamsters at day 21, increasing in amount thereafter. Since L donovani antigens and immunoglobulins were identified in the glomerular lesions, it is likely that they are implicated in the pathogenesis of the mesangial proliferative glomerulonephritis in hamsters experimentally infected with L donovani. The glomerular changes may also explain the loss of immunoglobulins in the urine and the consequent lowering of serum immunoglobulin levels.

Amyloidosis↗
PubMed1982

Polyclonal B cell activation in hamsters infected with parasites of the genus Leishmania.

Mesocricetus auratus (golden hamsters) infected with leishmania developed characteristic B cell immune responses that depended on the infecting species of leishmania. Thus, hamsters infected with viscerotropic leishmania (Leishmania donovani) developed antileishmania antibodies and hypergammaglobulinemia due to polyclonal activation of B cells as measured by reverse hemolytic plaque assay. In contrast, dermotropic leishmanias (L. braziliensis braziliensis and L. mexicana amazonensis) stimulated antileishmania antibodies with no increase in either serum immunoglobulin concentration or in the number of antibody-forming cells per spleen. The dermotropic leishmanias were unable to stimulate polyclonal activation even in hamsters in which visceralization had occurred with high splenic parasitization. These findings suggest that species-specific leishmania antigens (or factors) might be the modulators of the altered immune response present in these diseases.

Animals↗
PubMed1981

Receptor for immunoglobulin Fc on pathogenic but not on nonpathogenic protozoa of the Trypanosomatidae.

Members of the Trypanosomatidae were studied for their ability to acquire host IgG through a possible Fc receptor. A simple rosette test was devised in which the different species and forms of protozoa were mixed with SRBC sensitized with subagglutinating does of IgG, IgM, and F (ab') 2 anti-SRBC, and the pelleted mixture was observed for the number of clumps (rosettes) formed between the parasites and SRBC. Rosettes were formed between parasites and SRBC sensitized with IgG but not with IgM or F(ab')2, indicating the presence of a receptor for IgG Fc. The specificity of this receptor for Fc was confirmed by inhibition experiments with normal rabbit aggregated gammaglobulins or with purified normal rabbit Fc. The receptor is sensitive to treatment with trypsin but regenerates after a short period of incubation (1 h), which indicates that it is synthesized by the parasite itself. Interesting was the observation that only pathogenic members of the Trypanosomatidae formed rosettes with sensitized SRBC. In none of the nonpathogenic forms studied could we demonstrate the Fc receptor. Also important was the finding that freshly isolated blood stream forms of Trypanosoma cruzi from infected mice did not form rosettes. However, after trypsinization, these forms clearly displayed the ability to do so, possibly indicating a previous acquisition of the host IgG by the parasites in the mouse blood stream. These findings point to a possible and important means of parasite evasion of the host immune response by masking their surface with host IgG.

Animals↗
PubMed1981

Lectin(s) extracted from seeds of Artocarpus integrifolia (jackfruit): potent and selective stimulator(s) of distinct human T and B cell functions.

A lectin activity that selectively induces different functions of human lymphocytes has been described in a PBS crude extract obtained from the seeds of Artocarpus integrifolia (jackfruit). Both unfractionated peripheral blood mononuclear cells and purified T cells are strongly stimulated to proliferate by this extract, whereas purified B cells are not. However, the lectin induced a potent polyclonal activation of B cells measured by a reverse hemolytic plaque assay using a multivalent anti-human Fab antibody.

B-Lymphocytes↗
PubMed1978

Specificity and genetic restrictions of the guinea-pig immune response to dinitrophenyl-lysyl-alanyl octapeptides.

A series of 2,4-dinitrophenyl (DNP) octapeptides containing L-lysine and L-alanine were prepared to examine the specificity and genetic restrictions of both cellular and humoral immune responses in inbred guinea-pigs. Strains 2 and 13 guinea-pigs were therefore immunized with Lys4-Ala3-Lys(DNP), Lys3Ala4-Lys(DNP), Lys2-Ala5-Lys(DNP) and Lys-Ala6-Lys(DNP). Only Lys4-Ala3-Lys(DNP) was under Ir gene control and could induce both antibody and T-cell responses in strain 2 guinea-pigs. In contrast, Lys4-Ala3-Lys(DNP) injected in strain 13 guinea-pigs and the other DNP-octapeptides injected in strain 2 or 13 guinea-pigs elicited only antibody formation and no specific T-cell mediated response. Antibody formed in the absence of specific T-cell responsiveness in either strain 2 or 13 was hapten specific and lacked the capacity to discriminate the immunizing antigen from closely related DNP-peptides. Antibody produced by animals with specific T-cell responses, on the other hand, was exquisitely specific for the immunizing peptide and could discriminate it from closely related peptides.

Alanine↗
PubMed1977

Immune ascites in the guinea pig: specificity of cells and antibody in an induced peritoneal exudate.

Strain 2 guinea pigs, immunized with Lys10-Lys(Dnp) in CFA and repeatedly injected intraperitoneally with adjuvant, developed ascites. The fluid was harvested over 8 months in total amounts up to 2 liters per animal and contained substantial amounts of cells and antibody which reacted with the immunizing antigen and related peptides. The antibody was of the IgG and IgA classes and showed restricted heterogeneity. Among synthetic Dnp-oligopeptides, both the cells, studied by antigen-stimulated thymidine incorporation, and the purified antibody, studied by fluorescence quenching, demonstrated the same specificity for the immunizing antigen as has previously been noted in lymph node cells and in serum antibody. The technique offers a means for studying more cells and more antibody than has previously been possible from individual guinea pigs.

Animals↗
PubMedDate not supplied

Evaluation of a synthetic tripeptide as antigen for detection of IgM and IgG antibodies to Trypanosoma cruzi in serum samples from patients with Chagas disease or viral diseases.

An enzyme-linked immunosorbent assay (ELISA) has been developed to detect IgG and IgM antibodies in human sera against a synthetic tripeptide derived from a hybrid peptide containing 3 specific epitopes from Trypanosoma cruzi. This assay was compared in Brazil with one using conventional antigen, the alkaline crude extract. Serum samples were divided into positive (40 samples) or negative (107 samples) for Chagas disease. Positive samples included 9 serum samples from patients with acute Chagas disease, while negative samples included 57 samples from patients suffering from viral diseases. The total percentages of IgG positive samples from patients with chronic Chagas disease for alkaline extract and synthetic tripeptide were 93.5% and 100%, respectively. All samples from patients with acute Chagas disease were confirmed positive for IgM antibodies by using both the tripeptide and the alkaline extract. However, the results for anti-T. cruzi IgM in the group of chronic Chagas disease patients demonstrated that 41.9% were positive for IgM with the alkaline extract, while the synthetic peptide showed a significantly lower number of positive samples (12.9%). The serum samples from healthy people showed similar results for both antigens. However, 40% of the serum samples from patients presenting with viral diseases were IgM positive for Chagas disease when assayed with conventional antigen; with the synthetic tripeptide as antigen, 100% of this group of samples were found to be negative. Thus, as the results of ELISA with synthetic tripeptide showed higher rates of sensitivity and specificity than ELISA with conventional antigen, the former should be included as a laboratory tool in the serodiagnosis of Chagas disease.

Acute Disease↗