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Biomedical subjects

L A Hanson

Publications and source records attributed to L A Hanson.

At least 127 records · Page 7Linked to original sources
PubMed1995

Bystander suppression of the immune response to human serum albumin in rats fed ovalbumin.

Bystander suppression of delayed-type hypersensitivity (DTH) and the antibody response to human serum albumin (HSA) were studied in young normal rats and in young rats made partially tolerant to ovalbumin (OVA) by feeding an OVA-containing diet for 4 weeks from weaning. At 2 months of age, the animals were intracutaneously immunized with a mixture of OVA and HSA in Freund's complete adjuvant (FCA) at one site of the back, or separately at two different sites on the back. All rats made orally tolerant to OVA showed a significantly reduced IgE and IgG anti-OVA antibody production and DTH response to OVA, compared to the controls. OVA-fed rats subsequently immunized with a mixture of OVA + HSA had significantly lower IgE and DTH responses to HSA than the controls. When rats were immunized with OVA and HSA at two different sites, however, there was no difference in the response to HSA between the OVA-fed rats and the control rats, which rules out the possibility of shared epitopes between the antigens. Ear-challenge with the mixture of OVA + HSA gave a significantly lower DTH reaction in the tolerant rats immunized with a mixture of the antigens, compared to the control rats. However, suppression of the DTH reaction was not seen when tolerant and control rats were immunized with HSA alone and challenged with the mixture of OVA + HSA in one ear. These results present evidence that young rats orally tolerant to one antigen show a suppressed T-cell and antibody response to an unrelated antigen, provided that the two antigens are given in a mixture during the inductive phase. There was no evidence for bystander suppression of the T-cell response at the effector site.

Animals↗
PubMed1995

Bovine immunodeficiency virus in stud bull semen.

Bovine immunodeficiency virus (BIV), a lentivirus, is prevalent in dairy and beef cattle in southeastern United States and may be associated with a lymphoproliferative disease. The mode(s) of BIV transmission are undefined. Because artificial insemination is a common practice in dairy production, contaminated stud semen could serve as an important source of infection if the virus is harbored in seminal fluids. To evaluate this possibility, we procured 11 cryopreserved semen specimens from a stud semen repository. Leukocytes were purified from the specimens, and the leukocyte DNA was used as template in a polymerase chain reaction procedure that targeted a 235-base pair, highly conserved domain of the BIV pol gene. The target sequence was amplified from the seminal leukocyte DNA of 9 of the specimens (82%), and nucleotide sequencing confirmed the BIV specificity of the fragment. This finding provides evidence that stud bull semen may serve as an important reservoir of BIV, suggesting the possibility that artificial insemination of dairy cows may have a major role in transmission and wide-spread dissemination of this bovine lentivirus.

Animals↗
PubMed1995

Detection of bovine immunodeficiency virus in blood and milk-derived leukocytes by use of polymerase chain reaction.

Bovine immunodeficiency virus (BIV) is prevalent in beef and dairy cattle, yet the mode(s) of BIV transmission are undefined. Using polymerase chain reaction, which specifically targeted a 235-bp, highly conserved region of the BIV pol gene, BIV-infected leukocytes were detected in the blood and milk of BIV-seropositive cows. These data confirm the presence of BIV in milk and identify the potential for lactogenic transmission of this virus.

Animals↗
PubMed1995

T-cell-independent and T-cell-dependent IgE responses to the nematode Nippostrongylus brasiliensis: comparison of serum IgE and mast-cell-bound IgE.

The IgE immune response was studied in female athymic, nude (Lewis rnu/rnu) and euthymic (Lewis +/+) rats infected with the nematode Nippostrongylus brasiliensis. During the course of the infection, serum IgE levels were followed using an enzyme-linked immunosorbent assay technique (ELISA), while the surface expression and occupancy of IgE receptors on peritoneal mast cells were quantified using flow cytometry after immunolabelling with anti-IgE. The results show that the up-regulation of IgE receptors, which takes place on the mast cells of both athymic and normal rats during the early phase of the immune response, is more pronounced and longer-lasting in normal rats than in athymic ones, thereby suggesting that T cells are necessary for a full response to the parasite infection. The increased IgE occupancy observed on the mast cells during the early phase of the parasite immune response was not reflected in the serum IgE levels, which remained low during the entire infection period in athymic rats. In euthymic rats, on the other hand, there was a pronounced increase in serum IgE, as well as an increase in IgE occupancy on the mast cells, all reaching a peak level after 2 weeks of infection. However, there was no significant correlation between the serum IgE concentration and IgE occupancy or the density of IgE receptors on the mast cells of the individual euthymic rats. This indicates that the quantification of IgE occupancy on the mast cells may be a better way of detecting low-level IgE responses than the measurement of serum IgE. These findings, which were obtained in female Lewis rats, when compared with our previous findings in male rats of the same strain, suggest that sex differences may exist in terms of the intensity and duration of the IgE immune response to the parasite infection.

Animals↗
PubMed1994

Neutralizing interaction between heparins and myotoxin II, a lysine 49 phospholipase A2 from Bothrops asper snake venom. Identification of a heparin-binding and cytolytic toxin region by the use of synthetic peptides and molecular modeling.

Heparin binds to phospholipase A2 myotoxins from Bothrops asper snake venom, inhibiting their toxic activities. This interaction was investigated using purified myotoxin II, a Lys-49 phospholipase A2 of this venom, and a series of heparin variants, fragments, and other glycosaminoglycans. The binding was correlated to toxin neutralization, using endothelial cells as a target. Myotoxin II binds radiolabeled heparin in solution unselectively, and forms macromolecular complexes with an optimum at a heparin:toxin molar ratio of 1:5. Both O-sulfates and N-sulfates play a role in heparin binding, in the order of importance 2-O-sulfates > 6-Osulfates > N-sulfates. The shortest heparin oligosaccharides interacting with myotoxin II are hexasaccharides. The binding of a neutralizing monoclonal antibody (MAb-3) to myotoxin II was not inhibited by heparin, indicating that the two molecules interact with different sites on the toxin. A synthetic peptide (residues 115-129 in the numbering system of Renetseder et al. (Renetseder, R., Brunie, S., Dijkstra, B. W., Drenth, J., and Sigler, P. B. (1985) J. Biol. Chem. 260, 11627-11634) of myotoxin II displays both heparin-binding and cytolytic activities. It is concluded that heparin neutralizes myotoxin II by binding to a strongly cationic site in the region of residues 115-129, a possible contribution of lysines 36 and 38 suggested by molecular modeling studies. As this cationic region appears to be responsible for the cytolytic activity of the toxin, the present report constitutes the first identification of a cytotoxic region on a phospholipase A2 myotoxin.

Amino Acid Sequence↗
PubMed1994

Channel catfish herpesvirus (CCV) encodes a functional thymidine kinase gene: elucidation of a point mutation that confers resistance to Ara-T.

The channel catfish herpesvirus (CCV) thymidine kinase (TK) gene was mapped on the CCV genome by marker rescue analysis using a TK-deficient channel catfish ovary cell line (CCO), a TK-negative CCV mutant, and a panel of cloned CCV genomic DNA fragments. The TK-deficient cell line (CCOBr) was isolated after repeated propagation of CCO cells in increasing concentrations of 5-bromo-2'-deoxyuridine. Infection of CCOBr cells with CCV produced high levels of TK activity. The TK- virus (CCVAr) was isolated after repeated propagation in the presence of the TK-activated antiherpetic agent, 1-beta-D-arabinofuranosylthymine (Ara-T). A CCV genomic DNA library was constructed into cosmid pHC 79. Marker rescue analysis mapped the mutation within a 3.1-kb fragment located internal to the 18-kb repeat ends of the CCV genome. These genomic coordinates contained a putative TK gene identified by homology to other herpesvirus TK and cellular deoxycytidine kinase genes. DNA sequencing of the mapped coordinates identified the presence of a single mutation in the CCVAr mutant virus which resulted in a stop codon at amino acid position 97. These results functionally confirm that ORF 5 identified by Davison (Virology 186, 9-14, 1992) is the TK gene and show that CCV is amenable to marker rescue and marker transfer genetic analyses extensively used for investigations of the molecular biology of other herpesviruses.

Animals↗
PubMed1994

Neutralization of the cytolytic and myotoxic activities of phospholipases A2 from Bothrops asper snake venom by glycosaminoglycans of the heparin/heparan sulfate family.

Basic phospholipases A2 from the venom of Bothrops asper exhibit skeletal muscle damaging activity in vivo, and cytolytic activity to a variety of cell types in culture. Glycosaminoglycans of the heparin/heparan sulfate family were found to be potent blockers of the cytolytic action in vitro, and, as well, to be able to neutralize the muscle damaging activity of purified myotoxins and crude venom in vivo. However, the neutralizing effect of heparins was more potent in vitro than in vivo. The cytolytic activity of myotoxin II (a lysine-49 phospholipase A2 isoform) and its inhibition by heparin was characterized. The neutralizing effect of heparin did not depend on its anticoagulant activity, since both standard heparin and heparin with low affinity for antithrombin (LA-heparin) had a similar efficiency. Heparan sulfate and low molecular mass heparin (5 kDa) also neutralized myotoxin II. In contrast, different heparin-derived disaccharides were unable to block cytolysis, implying a requirement for a longer carbohydrate chain structure for the interaction with the protein. By affinity chromatography and gel diffusion, it was demonstrated that heparins form a complex with all isoforms of basic venom myotoxins, held at least in part by electrostatic interactions. The phospholipase A2 activity of myotoxin III, a related aspartate-49 isoform from the same venom, was unaffected by heparins, despite the fact that its myotoxic activity was inhibited, indicating a dissociation of the two actions.

Animals↗
PubMed1994

Activity of hemorrhagic metalloproteinase BaH-1 and myotoxin II from Bothrops asper snake venom on capillary endothelial cells in vitro.

In vivo, hemorrhagic toxins isolated from snake venoms cause a disorganization of the basal lamina of capillaries, with a concomitant degenerative process of endothelial cells. In this study we investigated the effects of BaH-1, a hemorrhagic metalloproteinase purified from the venom of Bothrops asper, on a murine endothelial cell line of capillary origin. A quantitative cytotoxicity assay based on the release of lactic dehydrogenase was utilized. BaH-1, despite its potent hemorrhagic activity, did not exert direct cytolytic activity on the endothelial cells, even at concentrations as high as 65 micrograms/ml. The only visible effect of BaH-1 on the cultured cells was a relatively slow, moderate detachment of cells, interpreted as a consequence of proteolytic degradation of extracellular matrix components. In contrast, myotoxin II, a lysine-49 phospholipase A2 from the same venom, was clearly cytotoxic to this cell type, albeit being devoid of hemorrhagic activity. These findings suggest that the ability of venom metalloproteinases to induce hemorrhage is not related to a direct cytotoxic action on endothelial cells, and that the rapid degenerative changes of endothelium observed in vivo are probably the result of an indirect mechanism.

Animals↗
PubMed1994

Broad cytolytic specificity of myotoxin II, a lysine-49 phospholipase A2 of Bothrops asper snake venom.

The cytotoxic activity of Bothrops asper myotoxin II, a lysine-49 phospholipase A2 isoform, on different cell types in culture, was investigated. Myotoxin II caused a dose-dependent cytolytic effect on all cell types tested, characterized by rapid release of cytoplasmic lactic dehydrogenase and drastic morphological cell alterations. Quantitative differences in the susceptibility to myotoxin II among cell types fell within a relatively narrow range, and in general, the toxin was cytolytic at concentrations of 50-100 micrograms/ml (3-7 microM), when assays were performed using culture medium as a diluent. Toxin activity was markedly enhanced if phosphate-buffered saline was utilized instead of medium. The cytotoxic activity of myotoxin III, an aspartate-49 isoform from the same venom, on both endothelial cells and skeletal muscle myoblasts was higher than that of myotoxin II, suggesting that, although phospholipase A2 activity is clearly not required for the induction of cell damage, it may have an enhancing role. In contrast to B. asper myotoxins, other basic phospholipases A2 with myotoxic activity in vivo (notexin from Notechis scutatus, and two enzymes isolated from Vipera russelli venom) did not affect endothelial cells and myoblasts. Pretreatment of cells with neuraminidase, tunicamycin, or protamine, did not alter their susceptibility to myotoxin II. At low temperatures (2-4 degrees C) myotoxin II was devoid of cytolytic effect. Washing and neutralization experiments using heparin with low affinity for antithrombin or mouse monoclonal antibody MAb-3 suggest that at low temperatures myotoxin II binds very weakly to the cells, and that its normal interaction with the putative target is probably not only based on charge, but that a membrane penetration event may be required.

Adenocarcinoma↗
PubMed1994

The prevalence of childhood asthma in Costa Rica.

The prevalence of asthma in children between the ages of 5 and 17 years in Costa Rica was determined using a large sample (n = 2682). The definition of asthma was based on a combination of a physician's diagnosis and a symptom score, using information from a questionnaire given to the parents. An overall asthma prevalence as high as 23.4% was found. Sex, age, urban/rural location, or rain precipitation did not show any association with the diagnosis of asthma. The presence of smokers in the home was found to be an important risk factor (odds ratio = 1.6). Another identified risk factor was a high yearly average outside temperature, i.e. above 25 degrees C (odds ratio = 1.8). Furthermore, the proportion of children with more than four upper respiratory infections during the preceding year was found to be significantly increased in children with asthma (odds ratio = 4.3). The non-asthma group seemed to use equal amounts of drugs for the treatment of asthma as the asthma group. For a country like Costa Rica with limited economic resources the current work indicates two important issues for consideration in the future; firstly, to try to define the cause(s) of asthma and secondly, to continuously inform the physicians about the best way of diagnosing and treating asthmatic patients to ensure optimal handling of this large patient group.

Adolescent↗
PubMed1994

Qualitative and quantitative analyses of the antibody response elicited by Haemophilus influenzae type b capsular polysaccharide-tetanus toxoid conjugates in adults with IgG subclass deficiencies and frequent infections.

Twenty-one IgG subclass-deficient adult patients with repeated infections of the respiratory tract, were immunized with Haemophilus influenzae type b capsular polysaccharide (HibCP) covalently bound to tetanus toxoid (TT). Specific immunoglobulin and IgG subclasses to HibCP and TT were quantified; the biological activities of HibCP antibodies were also investigated. Most patients showed an antibody response similar to that observed in healthy adults, and the bactericidal activity related to the post-immunization levels of HibCP antibodies. No relation was found between immunoglobulin isotype deficiency, the clinical symptoms and the IgG subclass responsiveness, and no relation was observed between HibCP and TT antibody responses. Our data indicate that some, but not all, patients with recurrent infections and IgG subclass deficiency have an abnormal serum antibody response to polysaccharide and protein epitopes of Hib-TT conjugate vaccine. Analysis of the antibody response after vaccination with HibCP-TT conjugate vaccine did not seem to predict the clinical course of such patients.

Adult↗
PubMed1994

The importance of G1m and 2 allotypes for the IgG2 antibody levels and avidity against pneumococcal polysaccharide type 1 within mono- and dizygotic twin-pairs.

Eighty-two mono- or dizygotic Caucasian twins vaccinated with a 23-valent pneumococcal vaccine, who had previously had their IgG2 antibody levels to pneumococcus type 1 determined before and after vaccination, were included in this study. Their IgG2 antibody levels were related to their G1m and G2m allotypes/phenotypes and their Gm amounts. Eight different Gm phenotypes were found and characteristically IgG2 antibody levels were related to them. G2m (n) homozygotic twins had significantly higher IgG2 levels than heterozygotic twins who had significantly higher levels than G2m (-n) homozygotic twins (P < 0.05). The G1m allotype, on the other hand was without influence on the IgG2 levels and so were the Gm amounts among G2m (n) heterozygotic twins. The IgG2 antibody avidities were not related to Gm allotypes but significantly correlated to IgG2 levels (P = 0.05). Finally, a highly significant intra-pair correlation was found for avidity in the monozygotic twins supporting a genetic regulation of avidity (P < 0.002). These results may explain our earlier findings that IgG2 antibody levels after pneumococcal vaccination are significantly more closely correlated within mono- compared to dizygotic twins.

Adult↗
PubMed1994

Differences within mono- and dizygotic twin-pairs in spectrotypes and clones of IgG2 antibodies to pneumococcal polysaccharide type 1 and C-polysaccharide after vaccination.

Spectrotypes and clones of antibodies against pneumococcal capsular polysaccharide (Ps) type 1 and C-polysaccharide (C-Ps) were determined before and after immunization with a polyvalent pneumococcal Ps vaccine in 84 mono- or dizygotic twins. The method used was a micromodification of a rapid isoelectric focusing-affinity (IEF-affinity) immunoblot technique in agarose permitting characterization of isotype, light chain and Gm type. After vaccination the anti-type 1 Ps + anti-C-Ps clones were different in 75% of the monozygotic and 79% of the dizygotic twins. The anti-type 1 Ps clones differed among 72% of the monozygotic and 85% of the dizygotic twins (P > 0.05). Each twin had from zero to three clones producing IgG2 antibodies against type 1 Ps. A total of six different clones could be distinguished among all the twins. Vaccination enhanced the already actively secreting B-cell clones in 56 twins and newly recruited clones in 11 of the 84 twins; six among the 48 mono- and five among the 36 dizygotic twins. These new clones differed among the twins. Spectrotypes varied between all twins within the pairs. The fact that all twins differed in spectrotype is due to post-translational microheterogenity of the antibodies, events which are thus not genetically determined. The observation that even monozygotic twins possessed and responded with different clones within the pairs indicates that the V-region genes, which determine the final specificity of B cells, either differ from the original germ-line V region genes, e.g. owing to hypermutations or junctional diversity, or the rearranged germ-line genes occur accidentally although highly restricted.

Adult↗
PubMed1994

Breast feeding: overview and breast milk immunology.

The transfer of host defence capacity to the human offspring provides a remarkable model of passive transfer of immunity. In fact it may also provide an example of active immunization. The transfer of mucosal protection via breast feeding offers many additional advantages for the mother and infant. Through its contraceptive effects it increases the spacing between births, thus diminshing the infant mortality and the burden on the mother. It also enhances bonding between mother and child, it seems to increase the IQ and school result of the infant and might decrease the risk of certain malignancies and perhaps of juvenile diabetes. A fully breast-fed infant receives as much as 0.5-1 g of secretory immunoglobulin A (SIgA) antibodies daily, the predominant antibody of human milk. This can be compared to the production of some 2.5 g of SIgA per day for a 60 kg adult. These SIgA antibodies have been shown to protect against Vibrio cholerae, ETEC, Campylobacter, Shigella and Giardia. Furthermore, milk is rich in receptor analogues for certain epithelial structures which microbes need for attachment to host tissues as an initial step in infections. Thus the adherence of Haemophilus influenzae and pneumococci for example to retropharyngeal cells is efficiently inhibited by human milk. This may be one explanation for the fact that breast-fed babies have less otitis media than the non-breast-fed. Other milk factors like lysozyme and lactoferin may contribute to the host defence, but this has not yet been well defined. However, human milk also supports the well-being of the infant by being anti-inflammatory.(ABSTRACT TRUNCATED AT 250 WORDS)

Breast Feeding↗
PubMed1994

Immune response against ovalbumin in rats colonized with an ovalbumin-producing Escherichia coli and the influence of feeding ovalbumin.

The influence of feeding ovalbumin (OA) on the development of IgE/IgG antibodies and delayed-type hypersensitivity (DTH) against OA was studied in rats colonized from birth with an Escherichia coli genetically manipulated to produce OA. At 21 days of age, colonized pups and pups with a normal intestinal flora were weaned onto either an OA-containing or a conventional diet without OA. At 2 months of age the colonized rats showed an increased DTH reaction to OA, but they did not have any anti-OA antibodies in serum. The rats were then immunized intracutaneously with OA in Freund's complete adjuvant. After immunization the colonized rats fed the conventional diet had a significantly higher DTH reaction to OA and significantly higher serum levels of IgE anti-OA antibodies than the uncolonized rats on the same diet. The colonized rats eating the OA-containing diet showed a 73% decrease in the DTH reaction to OA and also significantly lower levels of IgE and IgG antibodies against OA compared with the colonized rats fed conventional diet. The dams colonized as adults by the OA-producing E. coli developed IgE anti-lipopolysaccharide antibodies in serum while the pups colonized via the dams at birth did not. Neonatal colonization with an E. coli strain producing OA resulted in increased DTH reactivity against OA and priming for secondary IgE anti-OA response. Feeding the animals an OA-containing diet from weaning abrogated this intestinally induced hypersensitivity and rendered the animals orally tolerant to OA.

Animals↗