Biomedical subjects

M Strand

Publications and source records attributed to M Strand.

At least 19 recordsLinked to original sources

PubMed2001

Innate immunity and its evasion and suppression by hymenopteran endoparasitoids.

Recent studies suggest that insects use pattern recognition molecules to distinguish prokaryotic pathogens and fungi from "self" structures. Less understood is how the innate immune system of insects recognizes endoparasitic Hymenoptera and other eukaryotic invaders as foreign. Here we discuss candidate recognition factors and the strategies used by parasitoids to overcome host defense responses. We suggest that host-parasitoid systems are important experimental models for studying how the innate immune system of insects recognizes foreign invaders that are phylogenetically more closely related to their hosts. The strategies used by parasitoids suggest that insects may employ "hidden-self" recognition molecules for attacking foreign objects intruding the open circulatory system. BioEssays 23:344-351, 2001.

Animals↗

PubMed2001

Fucosyltransferases in Schistosoma mansoni development.

Glycoconjugate-bound fucose, abundant in the parasite Schistosoma mansoni, has been found in the form of Fucalpha1,3GlcNAc, Fucalpha1,2Fuc, Fucalpha1,6GlcNAc, and perhaps Fucalpha1,4GlcNAc linkages. Here we quantify fucosyltransferase activities in three developmental stages of S. mansoni. Assays were performed using fluorophore-assisted carbohydrate electrophoresis with detection of radioactive fucose incorporation from GDP-[(14)C]-fucose into structurally defined acceptors. The total fucosyltransferase-specific activity in egg extracts was 50-fold higher than that in the other life stages tested (cercaria and adult worms). A fucosyltransferase was detected that transferred fucose to type-2 oligosaccharides (Galbeta1,4GlcNAc-R), both sialylated (with the sialic acid attached to the terminal Gal by alpha2,3 or 2,6 linkage) and nonsialylated. Another fucosyltransferase was identified that transferred fucose to lactose-based and type-2 fucosylated oligosaccharides, such as LNFIII (Galbeta1,4(Fucalpha1,3)GlcNAcbeta1,3Galbeta1,4Glc). A low level of fucosyltransferase that transfers fucose to no-sialylated type-1 oligosaccharides (Galbeta1,3GlcNAc-R) was also detected. These studies revealed multifucosylated products of the reactions. In addition, the effects of fucose-type iminosugars inhibitors were tested on schistosome fucosyltransferases. A new fucose-type 1-N-iminosugar was four- to sixfold more potent as an inhibitor of schistosome fucosyltransferases in vitro than was deoxyfuconojirimycin. In vivo, this novel 1-iminosugar blocked the expression of a fucosylated epitope (mAb 128C3/3 antigen) that is associated with the pathogenesis of schistosomiasis.

Animals↗

PubMed2000

A generalized nonparametric test for lattice-ordered means.

Treatment means in factorial experiments are lattice ordered when there is an increase in mean response as the level of any factor is increased while holding the other factors fixed. Such means occur naturally in many experiments. A nonparametric test for lattice-ordered means involving a Kendall-type statistic will be summarized for k-factor factorial experiments. Specifically, the form of the test statistic and variance under the null hypothesis will be presented. In addition, a normalized version of the test statistic will be discussed and applied to relevant data.

Anabolic Agents↗

PubMed2000

Human immune responses to Schistosoma mansoni vaccine candidate antigens.

To determine the naturally occurring immunological responses to the Schistosoma mansoni antigens paramyosin, IrV-5, Sm-23 (MAP-3), and triose phosphate isomerase (MAP-4), a total of 119 subjects from an area of endemicity for schistosomiasis, including "resistant" subjects (n = 17) were evaluated. Specific immunoglobulin G1 (IgG1), IgG2, IgG3, IgG4, and IgA levels for each of the antigens and the cytokine profile in culture supernatants from antigen-stimulated peripheral blood mononuclear cells (PBMC) were determined. Although all the subjects had a high degree of contaminated water exposure, their infection levels were variable (0 to 1,128 eggs/g of stool). There were direct correlations between infection levels and levels of SWAP- and paramyosin-specific IgG1 and IgG4 (P < 0.05). However, an inverse correlation between infection levels and specific IgG2 to IrV-5 (P < 0.01) was observed. The evaluation of the cytokine profile (interleukin 5 [IL-5], IL-10, gamma interferon [IFN-gamma], and tumor necrosis factor alpha) in response to these antigens showed inverse correlations between the degree of infection and IFN-gamma levels in PBMC supernatants stimulated with paramyosin (P < 0.05) and IrV-5 (P < 0.01). Additionally, inverse correlations between the degree of infection and IL-5 levels in MAP-3- and MAP-4-stimulated PBMC supernatants (P < 0.01) were found. Logistic regression analysis was performed to adjust the results of cytokine profile by age. IL-5 production in MAP-3-stimulated PBMC supernatants was associated with lower infection levels (odds ratio = 11.2 [95% confidence interval, 2.7 to 45.8]).

Adult↗

PubMed1998

Molecular characterization of a fucosyltransferase encoded by Schistosoma mansoni.

The glycans of schistosomes include many complex carbohydrates that contain fucose. Although the biological functions of these complex carbohydrates are not yet clearly understood, some of these structures are thought to play essential roles in the life cycle of the parasite. Here we present the molecular cloning and characterization of a fucosyltransferase of Schistosoma mansoni with a DNA sequence similarity of 84.6 and 63.7% to mouse and human fucosyltransferase type VII. Southern blot analysis of genomic DNA indicated that this S. mansoni fucosyltransferase is the product of a single gene. The schistosome cDNA sequence that we obtained contains an open reading frame encoding a protein of 351 amino acids with a predicted molecular size of 40.5 kDa. From the amino acid sequence, we predicted two potential N-linked and one O-linked glycosylation site. Western blot studies of extracts from stably transfected CHO cells showed a band corresponding to the schistosome fucosyltransferase at 50 kDa, suggesting that the enzyme is indeed glycosylated. We further demonstrated the expression and enzymatic activity of the fucosyltransferase in the transfected cells by immunofluorescence studies and flow microfluorimetric analysis, which indicated that the enzyme is capable of synthesizing the SLeX blood group determinant but not the LeX determinant in CHO cells. The identification of a fucosyltransferase type VII in schistosomes further underscores the importance of fucose-containing glycans in schistosome glycobiology.

Amino Acid Sequence↗

PubMed1998

Young child injury analysis by the classification entropy method.

The project 'The Register and Preventive Programs for Accidents and Injuries' enabled data collection on all the injured who sought medical aid in Koprivnica County (population 61,052), Croatia, since 1992. Children aged 1-4 years are 5.03% of the whole population of the district. Complex injury attributes were analysed. Binary attributes were classified as input: age, gender, place of injury; and output: severity of injury. A new application of information entropy was introduced and applied to the classification of injury-causes attributes. The information entropy was calculated for the classification of input attributes according to the minimum information content. The decision procedure is given as a sequential procedure separating important from unimportant causes of injury at each decision level. Thus a decision tree with increasing entropy, i.e. decreasing determinism, was obtained showing that age (0.5347 N), place (0.6062 N) and gender (0.6105 N) are measurable attributes in child injury ascertainment in a descending pattern. It was shown that this method is, at the same time, an optimal way of using an attribute decision process of injury causes classification.

Accidents↗

PubMed1998

Studies on schistosomiasis in western Kenya: II. Efficacy of praziquantel for treatment of schistosomiasis in persons coinfected with human immunodeficiency virus-1.

Praziquantel is the drug of choice for schistosomiasis chemotherapy. Although the exact mechanism of how praziquantel kills schistosomes remains poorly understood, the immune response of the host is an important factor in drug efficacy. It is thus possible that disease states of humans that lead to immunodeficiencies, such as infection with human immunodeficiency virus-1 (HIV-1), may render praziquantel less effective in treating schistosomiasis. To test this hypothesis, persons with high levels of Schistosoma mansoni infection who were or were not also infected with HIV-1 were treated with a standard regimen of praziquantel and monitored by quantitative fecal examination and plasma circulating cathodic antigen. Both groups responded to praziquantel therapy equally and individuals with low percentages (< 20%) of CD4+ T cells did not differ from individuals with higher CD4 cell percentages. These data demonstrate that persons with HIV-1 infection can be treated effectively for schistosomiasis with praziquantel.

Animals↗

PubMed1997

Molecular characterization of a 20.8-kDa Schistosoma mansoni antigen. Sequence similarity to tegumental associated antigens and dynein light chains.

Survival of Schistosoma mansoni within the infected host requires the parasite to actively maintain its protective tegument. The components responsible for this maintenance are therefore attractive targets for immunoprophylaxis or chemotherapy. Here we report the molecular characterization of a 20.8-kDa tegumental antigen with sequence similarity to dynein light chains and tegumental associated antigens. A cDNA encoding the 20.8-kDa polypeptide contains an open reading frame of 181 amino acids and predicts an isoelectric point of 7.27. Expression of the 20.8-kDa antigen is developmentally regulated, with the highest concentration found in cercariae. Our data show that the 20.8-kDa polypeptide specifically interacts with a S. mansoni 10.4-kDa dynein light chain that we have previously described (Hoffmann, K. F., and Strand, M. (1996) J. Biol. Chem. 271, 26117-26123). Velocity sedimentation analysis of a parasite extract demonstrated that this 10.4-kDa dynein light chain and the 20.8-kDa polypeptide were present in a complex that sedimented at 4.4 Svedberg units. We have also shown by antibody cross-reactivity that a 20.8-kDa homolog of the S. mansoni antigen is present in Schistosoma japonicum, but not in Schistosoma hematobium or Fasciola hepatica. Because the 20.8-kDa polypeptide displays ideal characteristics of a potential vaccine candidate, including (i) expression in the tegument, (ii) significant divergence from mammalian brain cytoplasmic dynein, and (iii) a conserved homolog in S. japonicum, we are currently evaluating its immunoprophylactic efficacy.

Amino Acid Sequence↗

PubMed1996

IL-12 enhances vaccine-induced immunity to schistosomes by augmenting both humoral and cell-mediated immune responses against the parasite.

The production of Th1-type cytokines is associated with strong cell-mediated immunity, while Th2-type cytokines typically dominate humoral immune responses. In mice vaccinated a single time with attenuated cercariae of Schistosoma mansoni, the protection induced is associated with Th1 cytokine-dependent, cell-mediated immunity. In contrast, mice vaccinated multiple times display a more Th2-type dominant cytokine response and develop Ab-dependent resistance. We have previously shown that IL-12 enhances cell-mediated immunity in singly vaccinated mice. In the present study, we asked what effects administering IL-12 as an adjuvant would have on the development of a protective humoral response in multiply immunized animals. We found that multiply immunized/IL-12-treated mice displayed a marked increase in resistance to challenge infection, with some animals demonstrating complete protection. The IL-12-vaccinated mice developed strongly polarized Th1 responses but, importantly, also showed significant increases in parasite-specific Ab and, in particular, IgG2a, IgG2b, and IgG1 isotypes. Passive transfer demonstrated an enhanced ability of serum from these animals to protect naive recipients. In addition, animals vaccinated in the presence of IL-12 also developed macrophages with increased nitric oxide-dependent killing activity against the parasites. Together, these data demonstrate that IL-12, initially described as an adjuvant for cell-mediated immunity, may be used to simultaneously to promote both humoral and cell-mediated protective responses against infection.

Animals↗

PubMed1996

Molecular identification of a Schistosoma mansoni tegumental protein with similarity to cytoplasmic dynein light chains.

The tegument of Schistosoma mansoni contains a number of proteins that presumably function in its maintenance and/or repair against damage incurred from host-mediated humoral immune responses. Here, we show that the schistosome antigen identified by monoclonal antibody 709A2/2 is a cytoplasmic dynein light chain. Dynein light chains are components of dynein, an enzyme complex involved in various aspects of microtubule-based motility. Monoclonal antibody 709A2/2 recognizes two polypeptides, one of 8.9 kDa and a second of 7.6 kDa, as determined by SDS-polyacrylamide gel electrophoresis. We find that expression of S. mansoni dynein light chain is developmentally regulated and localized to the tegument in the schistosomula, lung stage worms, and adult worms, but is not present in the cercariae or ciliated miracidia. By Northern blot analysis of adult worm RNA, S. mansoni dynein light chain is encoded by a single message of approximately 600 base pairs. A cDNA encoding this polypeptide contains an open reading frame of 89 amino acids with a deduced molecular mass of 10.4 kDa. Coprecipitation of an apparent 18.4-kDa antigen with S. mansoni dynein light chain by monoclonal antibody 709A2/2 illustrates that this molecule has an affinity for other proteins. Such interactions may play a role in S. mansoni dynein light chain participation in organelle trafficking in S. mansoni.

Amino Acid Sequence↗

PubMed1996

Calpain is the target antigen of a Th1 clone that transfers protective immunity against Schistosoma mansoni.

A CD4+ clone (clone B), characterized as Th1 based on its selective production of IFN-gamma and IL-2, was established from C57Bl/6 mice protectively immunized against Schistosoma mansoni by intradermal vaccination with soluble worm Ags, plus bacillus Calmette Guerin. In agreement with previous results demonstrating an IFN-gamma-dependent cell-mediated protective mechanism in this vaccination model, Ag-elicited peritoneal macrophages from syngeneic recipients of this clone were activated to kill schistosome larvae (schistosomula) in vitro. Moreover, recipients of clone B displayed significant resistance against cercarial challenge. By screening a battery of lambda(gt11) clones from an adult worm cDNA library, one recombinant (25B) was identified that stimulated clone B specifically. Analysis of the 25B cDNA insert revealed a nucleotide sequence identical with that of the large subunit of schistosome calpain, a Ca2+-activated neutral proteinase. By expressing the products of PCR subcloning, we identified a 146-amino acid region of the 25B gene containing immunologic activity equivalent to the whole polypeptide. Overlapping peptides spanning this region were synthesized, and a core epitope was identified with the sequence EWKGAWCDGS. Since clone B responds to supernatants from cultured schistosomula, we postulate that the recognition of calpain released by invading larvae and resulting induction of Th1 cytokines accounts for the protection mediated by the adoptively transferred clone. Our findings thus implicate calpain as a target of protective immunity in schistosomes and provide the first example of a candidate vaccine Ag for this parasite identified on the basis of T cell reactivity.

Adoptive Transfer↗

PubMed1996

The use of 212Pb-labeled monoclonal antibody in the treatment of murine erythroleukemia.

PURPOSE: The goals of this study were to learn whether the DOTA chelator was useful for targeting lead radionuclides (203,212 Pb) to cells and tissues invaded by the Rauscher leukemia virus (RVB3) and to investigate the therapeutic efficacy of targeted 212Pb in treating the murine leukemia. METHODS AND MATERIALS: Five to 6-week-old BALB/c mice were inoculated i.v. with RVB3. This virus causes marked splenomegaly and death by day 13 and day 70 postinfection, respectively. Biodistribution, tumor targeting, and toxicity studies were performed using varying doses of 212Pb-DOTA-103A. A heavy metal chelator, DMPS, was administered orally and parenterally in two phases of the toxicity study. RESULTS: Biodistribution studies showed marked tumor targeting (58% ID/g spleen) in mice treated with 203Pb-103A as compared with mice treated with control antibody B3 (4.6% ID/g spleen). Histologic cure was achieved in all leukemic mice treated with 20 muCi212Pb-103A; however, all of the mice died with leukopenia and secondary++ bacterial infections due to severe bone marrow toxicity. Nonleukemic mice and mice treated with 20 muCi212Pb-B3 experienced less marrow toxicity and longer survival. Coadministration of the heavy metal chelator did not diminish the bone marrow toxicity. CONCLUSION: An effective, nonlethal dose could not be established to treat this tumor. The severe bone marrow toxicity associated with this radionuclide may limit its usefulness in systemic radioimmunotherapy.

Animals↗

PubMed1996

Molecular cloning of a Schistosoma mansoni protein expressed in the gynecophoral canal of male worms.

Female members of the species Schistosoma mansoni require continual interaction with males to achieve sexual maturity [1,2]. The nature of the developmental stimuli provided by the adult male parasite are unknown. Aronstein and Strand have reported that the surface expression of an 86-kDa gynecophoral canal protein, SmGCP, is gender-specific in adult S. mansoni [3]. The antigen shows wide distribution on the surface of adult female worms, but in males surface expression is limited to the gynecophoral canal, the site of direct interaction between the mating pair. Expression of the antigen is undetectable or severely diminished in unmated male worms, suggesting a role for this glycoprotein in schistosome mating and/or egg production. We report here the molecular cloning and sequencing of a cDNA clone, SmGCP, which contains a deduced amino acid sequence of 688 residues with a predicted molecular mass of 79 kDa. SmGCP is encoded by a single RNA transcript of 2.4 kb. Enzymatic removal of N-linked glycans from native SmGCP results in a 7-kDa shift in molecular mass as observed by SDS-PAGE. SmGCP contains multiple short, conserved repeat regions with sequence similarity to the developmentally-regulated neural cell adhesion molecule fasciclin I. Although localized to the schistosome surface, SmGCP lacks a convincing transmembrane region. The identification of a gynecophoral canal-specific antigen may have implications for the reproductive development of schistosomes and may provide a novel target for anti-parasite therapeutics.

Amino Acid Sequence↗

PubMed1996

Polyembryonic development: insect pattern formation in a cellularized environment.

THe polyembryonic wasp Copidosoma floridanum produces up to 2000 individuals from a single egg. During the production of individual embryos the original anteroposterior axis of the egg is lost and axial patterning must subsequently be reestablished within each embryo. The mechanism by which this occurs is unknown. In most insects, egg polarity is established during oogenesis and early development takes place in a syncytium. In Drosophila melanogaster, the syncytium is considered essential for establishing the morphogenetic gradients that initiate segmental patterning. However, we found that development of C. floridanum occurs almost exclusively in a cellularized environment. To determine whether the D. melanogaster patterning cascade is conserved in the absence of a syncytium, we analyzed the expression of Even-skipped, Engrailed and Ultrabithorax/Abdominal-A during polyembryonic development. Here we show that in spite of the absence of a syncytium, the elements of the D. melanogaster segmentation hierarchy are conserved. The segment-polarity gene Engrailed and the homeotic genes Ultrabithorax/Abdominal-A are expressed in a conserved pattern relative to D. melanogaster. However, we detect an alteration in the expression of the Even-skipped antigen. Even-skipped is initially expressed in segmentally reiterated stripes and not in the pair-rule pattern as it is in D. melanogaster. We also observe that the expression of these regulatory proteins does not occur during the early proliferative phases of polyembryony. Our results indicate that a syncytium is not required for segmental patterning in this insect.

Animals↗

PubMed1995

Mutations in the MSH3 gene preferentially lead to deletions within tracts of simple repetitive DNA in Saccharomyces cerevisiae.

Eukaryotic genomes contain tracts of DNA in which a single base or a small number of bases are repeated (microsatellites). Mutations in the yeast DNA mismatch repair genes MSH2, PMS1, and MLH1 increase the frequency of mutations for normal DNA sequences and destabilize microsatellites. Mutations of human homologs of MSH2, PMS1, and MLH1 also cause microsatellite instability and result in certain types of cancer. We find that a mutation in the yeast gene MSH3 that does not substantially affect the rate of spontaneous mutations at several loci increases microsatellite instability about 40-fold, preferentially causing deletions. We suggest that MSH3 has different substrate specificities than the other mismatch repair proteins and that the human MSH3 homolog (MRP1) may be mutated in some tumors with microsatellite instability.

Base Sequence↗

PubMed1995

Schistosoma mansoni: molecular cloning and sequencing of the 200-kDa chemotherapeutic target antigen.

Praziquantel is the drug of choice for human schistosomiasis. The efficacy of this drug is impaired in immune-deficient mice. However, transfer to B cell-depleted mice of a monoclonal antibody that recognizes a 200-kDa GPI-anchored glycoprotein of S. mansoni restores the effectiveness of praziquantel. In order to characterize this target antigen, we have isolated and sequenced cDNA clones encoding the 200-kDa protein. Three overlapping cDNA clones contained the complete nucleotide sequence. The sequences of five tryptic peptides from the native 200-kDa protein could be matched with regions in the amino acid sequence deduced from the nucleotide sequence of the isolated clones. This deduced amino acid sequence differed from sequences available in six databases. Praziquantel exposes epitopes on the worm surface that are normally not exposed, and we have shown by immunofluorescent staining that the fusion protein encoded by one of our cDNA clones expresses epitopes that are exposed on the surface of praziquantel-treated worms.

Amino Acid Sequence↗

PubMed1995

Structural analysis of affinity maturation: the three-dimensional structures of complexes of an anti-nitrophenol antibody.

Affinity maturation of the immune response to nitrophenol-containing antigens has been extensively investigated. Significant strides made during the past several years with the advent of PCR technology have provided a wealth of biochemical knowledge. Structural investigations of the phenomena have however been limited. We have determined the three-dimensional structure of the Fab fragment of 88C6/12, an anti-4-hydroxy-3-nitrophenyl acetic acid antibody complexed with the immunizing hapten and with a heteroclitic iodinated hapten. The crystallographic structure of the complexes reveals that the binding is stabilized by a number of hydrogen bonds and extensive van der Waals interactions between the hapten and the antibody. In addition, the Fab binding pocket contains a region of positive electrostatic potential well suited for interaction with the predominant resonance form of the nitrophenyl ring system. The observed heteroclicity towards the iodinated hapten is not a direct result of iodine-protein interactions, but results from the enhanced stability in the iodinated ring of the resonance form that binds the antibody. In addition this investigation provides a rationale for the strong preference for the substitution in the heavy chain from the germ-line gene encoded Trp 33 to Leu 33 in the mature anti-nitrophenol response.

Amino Acid Sequence↗

PubMed1995

Molecular mimicry between HIV-1 gp41 and an astrocyte isoform of alpha-actinin.

A 100-kDa astrocyte antigen previously shown to cross-react with a monoclonal antibody (MAb) generated against amino acids (aa) 598 to 609 of the transmembrane protein gp41 of human immunodeficiency virus type 1 [HIV-1] has now been molecularly characterized and found to be an alpha-actinin (alpha-actinin) related protein. Western blot analyses of human astrocytoma cells fractionated by differential centrifugation and detergent phase separation showed that the antigen was membrane associated. The astrocyte protein was purified to apparent homogeneity by immunoaffinity chromatography. Amino acid analysis of three peptide fragments obtained by cleavage of the purified 100-kDa protein revealed sequence identities of 77, 83 and 100% to a non-muscle isoform of human alpha-actinin. In addition, the aa 598-609 sequence of gp41 recognized by MAb 781.4, and the aa 581-597 sequence recognized by another cross-reactive MAb 781.3, were 73% and 53% similar to regions of alpha-actinin. This molecular mimicry between gp41 and alpha-actinin was supported by antibody cross-reactivity in Western immunoblot and ELISA analyses. Both anti-gp41 and anti-alpha-actinin MAbs bind to the surface of the human astrocytoma cells as detected by a cell surface binding assay and immunofluorescence. Antibodies made against this immunodominant region of gp41 in the serum and CSF of HIV-infected individuals have access to astrocytes within the CNS. The identification of the astrocyte antigen as an alpha-actinin related protein will allow further work to determine how this immunological cross-reactivity could perturb astrocyte function and contribute to HIV neuropathology.

AIDS Dementia Complex↗