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M V Norgard

Publications and source records attributed to M V Norgard.

89 records · Page 5Linked to original sources
PubMed1986

Monoclonal antibody selection and analysis of a recombinant DNA-derived surface immunogen of Treponema pallidum expressed in Escherichia coli.

Monoclonal antibodies directed against a 34-kilodalton (kDa) surface immunogen of Treponema pallidum were used to select 12 unique T. pallidum DNA-containing Escherichia coli recombinant clones expressing the recombinant form of the 34-kDa immunogen. The phenotype of the clones was dependent on the presence of recombinant plasmids in the host cell. Restriction enzyme analyses and Southern hybridization of plasmid DNA demonstrated that all recombinant clones contained common DNA sequences of T. pallidum origin. Further hybridization analyses revealed that the cloned T. pallidum DNA sequences were an accurate representation of the T. pallidum genomic DNA arrangement. Purified immunoglobulin G (IgG) from pooled immune rabbit serum reacted with the clones, while IgG from pooled normal rabbit serum did not. Results of immunological experiments and Southern hybridization indicated that a similar 34-kDa immunogen was present in T. pallidum subsp. pertenue, but it was absent from four species of nonpathogenic treponemes tested, as well as from homogenates of normal rabbit testicular tissue. Metabolic labeling of the E. coli clones with [35S]methionine followed by radioimmunoprecipitation with monoclonal antibodies revealed that the 35S-labeled recombinant and 125I-labeled native (T. pallidum) forms of the antigen had identical electrophoretic mobilities. The production of a complete antigen by E. coli was independent of the orientation of the foreign gene sequence with respect to vector DNA. T. pallidum also produced an apparently identical immunoprecipitable 34-kDa antigen after metabolic labeling with [35S]methionine in the presence of cycloheximide. The apparent specificity of the 34-kDa immunogen for pathogenic treponemes and its native cell surface association on T. pallidum justifies a more intense study of this antigen and its corresponding gene.

Antibodies, Monoclonal↗
PubMed1986

Cloning and expression of the major 47-kilodalton surface immunogen of Treponema pallidum in Escherichia coli.

Monoclonal antibodies directed against the 47-kilodalton (kDa) major outer membrane surface immunogen of virulent Treponema pallidum subsp. pallidum were used to select Escherichia coli recombinant clones expressing the 47-kDa immunogen. The phenotype of the clones was dependent on the presence of recombinant plasmid in the host cell. Southern hybridization revealed that the cloned T. pallidum subsp. pallidum DNA sequence was an accurate representation of the T. pallidum subsp. pallidum genomic DNA arrangement. Purified immunoglobulin G from rabbits experimentally infected with T. pallidum subsp. pallidum and human secondary syphilitic sera specifically reacted with the clones, while normal human serum or immunoglobulin G from normal rabbit serum did not. Results of Southern hybridization indicated that a homologous 47-kDa immunogen gene was absent in at least four species of nonpathogenic treponemes tested, as well as from total rabbit genomic DNA. Rabbit anti-T. phagedenis biotype Reiter (treponemal nonpathogen) antiserum and a monoclonal antibody directed against a common treponemal determinant were unreactive with the clones. Western blotting and radioimmunoprecipitation experiments with specific monoclonal antibodies revealed that the recombinant (E. coli) and native (T. pallidum subsp. pallidum) forms of the antigen had identical electrophoretic mobilities. The availability of recombinant 47-kDa immunogen provides a new opportunity for biochemical analysis of the protein, structure-function studies, examination of its role in microbial pathogenesis, and assessment of its diagnostic and vaccinogenic potentials.

Antigens, Bacterial↗
PubMed1985

Molecular assessment of S1 endonuclease-resistant snapback hairpin loops generated by DNA polymerase I during the in-vitro nick translation reaction.

The in-vitro nick translation reaction used to label DNA to high specific activity also produces aberrant DNA structures known as "snapback" hairpin loops. Hairpin structures are precluded from participating in precise DNA-DNA hybridization interactions. Three nick translation systems were all found to yield significant quantities of snapback hairpins, as determined by their resistance to S1 endonuclease digestion following denaturation. The relative quantities of hairpins produced correlated with both the mass average size of the final DNA probe product synthesized as well as the overall rate of the nick translation reaction. Decreases in the amount of exogenous DNase I used in nick translation reactions produced significant decreases in the amount of hairpin loop structures formed. Hairpins could be effectively removed from nick-translated DNAs by employing hydroxylapatite column chromatography. Strategies to reduce hairpin formation during nick translation and the removal of hairpins from nick-translated DNAs are presented.

DNA↗
PubMed1984

Monoclonal antibody with hemagglutination, immobilization, and neutralization activities defines an immunodominant, 47,000 mol wt, surface-exposed immunogen of Treponema pallidum (Nichols).

Radioimmunoprecipitation (RIP) analyses performed on 125I-surface-labeled Treponema pallidum cells using various immune sera revealed the presence of six major surface antigens (immunogens) with apparent molecular weights of 47 K, 36 K, 34 K, 32 K, 29 K, and 13 K. Among these, the 47 K surface antigen was most abundant. Radioimmunoprecipitation assays using 125I-labeled T. phagedenis biotype Reiter or immunoblot analyses using the same strain, failed to reveal the presence of the 47 K mol wt antigen in the representative nonpathogenic treponeme. Preabsorption of anti-T. pallidum immune rabbit serum (IRS) with the Reiter organism did not remove anti-T. pallidum antibodies from immune serum that reacted with the 47 K mol wt immunogen or other immunogens of T. pallidum present in the characteristic antigenic profile. Monoclonal antibodies (mAb) directed specifically against the 47 K mol wt immunogen of T. pallidum also failed to react with an analogous 47 K mol wt component in Treponema phagedenis biotype Reiter, further suggesting the unique presence of this antigen in pathogenic treponemes. The presence of the 47 K mol wt surface immunogen in pathogenic treponemes other than T. pallidum subspecies pallidum was also observed (43). Anti-47 K immunogen mAb was nonreactive against rabbit IgG or IgM. mAb directed specifically against the 47 K mol wt immunogen of T. pallidum was examined for strategic functional activities. It was found to be reactive in the microhemagglutination assay for T. pallidum antibodies, the T. pallidum immobilization test, and was found to be capable of significant blockage of attachment of virulent T. pallidum to host cells in tissue culture. Additional significant biological activity for the anti-47 K mol wt immunogen mAb was revealed through results of the in vitro-in vivo neutralization test of Bishop and Miller, in which a 99% or 100% neutralizing activity was demonstrated. The combined data of this study suggest that the 47 K mol wt immunogen of T. pallidum represents an abundant, immunodominant, surface-exposed immunogen possessing potential biological importance in the pathogenesis and immunology of T. pallidum infection. These studies serve to establish the first functionally defined immunogen for T. pallidum, which may represent the major immunogen of the organism.

Animals↗
PubMed1984

Monoclonal antibody analysis of specific antigenic similarities among pathogenic Treponema pallidum subspecies.

Murine monoclonal antibodies directed against a 47,000-dalton immunodominant surface-exposed antigen of Treponema pallidum subsp. pallidum (Nichols) were isolated. These monoclonal antibodies cross-reacted with analogous 47,000-dalton antigens of two other virulent treponemes, T. pallidum subsp. pertenue and T. pallidum subsp. endemicum (Bosnia A), as determined by radioimmunoassay and immunoblot analyses. Immunoelectron microscopy confirmed that the 47,000-dalton antigen of T. pallidum subsp. pallidum was a surface-associated cellular component. Surface binding assays and immunoelectron microscopic studies also suggested that the analogous 47,000-dalton antigenic component of T. pallidum subsp. pertenue may not have been oriented toward the bacterial surface in the same way as the T. pallidum subsp. pallidum antigen or that the relevant antigenic determinant(s) may not have been exposed to the outer surface in the same way. The significance of this antigen relative to its apparent conservation among pathogenic treponemes and its possible diagnostic and vaccinogenic potentials are discussed.

Animals↗
PubMed1984

Sensitivity and specificity of monoclonal antibodies directed against antigenic determinants of Treponema pallidum Nichols in the diagnosis of syphilis.

Murine anti-Treponema pallidum monoclonal antibodies were employed in studies on sensitivity and specificity of binding to examine their potential for use in the detection of low numbers of pathogenic treponemes present in various body fluids. Monoclonal antibodies were used as a primary antibody source in a solid-phase immunoblot assay system. All monoclonal antibodies assayed were capable of detecting ca. 1.0 X 10(3) to 2.5 X 10(3) treponemes. Of 13 monoclonal antibodies examined, 3 were able to detect 10(3) virulent treponemes, and 1 of these antibodies was able to reveal the presence of as few as 500 organisms. Western blot analyses showed that all anti-T. pallidum monoclonal antibodies exhibiting high sensitivities for the detection of T. pallidum cells were directed against an abundant, 47,000-dalton surface-exposed antigen of the organism (S. A. Jones, K. S. Marchitto, J. N. Miller, and M. V. Norgard, Abstr. Annu. Meet. Am. Soc. Microbiol. 1984, B173, p. 46; K. S. Marchitto, S. A. Jones, and M. V. Norgard, Abstr. Annu. Meet. Am. Soc. Microbiol. 1984, B182, p. 48). Differences in binding properties of the various monoclonal antibodies were most likely a reflection of differential binding affinities or their specificities for different epitopes on the 47,000-dalton surface antigen. With two possible exceptions, the monoclonal antibodies tested reacted specifically with T. pallidum, either purified or found within a high-contaminating tissue background, and not with Treponema phagedenis biotype Reiter, Haemophilus ducreyi, Neisseria gonorrhoeae, herpes simplex virus type 2, or normal rabbit testicular tissue. The high sensitivity and specificity exhibited by these anti-T. pallidum monoclonal antibodies make them excellent candidates for employment in new syphilis or other treponemal diagnostic tests designed to detect very low numbers of pathogenic treponemes in lesion exudates or other body fluids.

Animals↗
PubMed1983

Cloning and expression of Treponema pallidum (Nichols) antigen genes in Escherichia coli.

Hybrid pBR322 plasmid clone banks comprised of more than 125,000 recombinant DNA clones and representing the entire Treponema pallidum Nichols genome were constructed in Escherichia coli K-12 RR1. The two clone banks individually contain over 53,000 and 72,000 recombinant clones. The number average and mass average sizes of the cloned DNA inserts were found to be approximately 12 and 13 kilobase pairs, respectively, indicating the presence of large treponemal DNA inserts in a majority of recombinant clones. To detect E. coli clones synthesizing T. pallidum antigens as hybrid plasmid gene translation products in the clone bank, a simplified, direct, solid-phase radioimmuno-colony blot (RICB) assay was developed employing immunoglobulin G antibody isolated from anti-T. pallidum immune rabbit serum. Clones with positive reactivities in the RICB assay were isolated at frequencies of 0.1 to 0.2%. One isolated RICB-positive clone, designated RICB2-1, produced a very strong signal in the RICB assay and was subsequently found through E. coli cell-free in vitro transcription/translation analysis to encode the synthesis of two gene translation products with apparent molecular weights of 77,000 and 44,000. The 44,000-dalton protein was effectively immunoprecipitated from [35S]methionine-labeled E. coli clone cells by using either immune rabbit serum (preabsorbed with Treponema phagedenis biotype Reiter antigens) or selected human syphilitic serum, whereas the 77,000-dalton protein was never immunoprecipitable by similar methods. Purified plasmid DNA from clone RICB2-1 contained a treponemal DNA insert of 3.70 kilobase pairs, which was of suitable size to code for the 121-dalton (44 + 77) protein. The insert was also flanked on each end by PstI sites and possessed three internal PstI sites with fragment sizes of 2.15, 1.18, 0.20, and 0.17 kilobase pairs. Purified clone RICB2-1 plasmid DNA was capable of transforming recipient E. coli cells to virtually 100% RICB reactivity, thus substantiating the plasmid-encoded characteristic. Further experiments employing various antisera in radioimmunoprecipitation systems utilizing cell-free in vitro synthesized gene translation products from clone RICB2-1 also provided the first evidence that E. coli may be capable of using endogenous T. pallidum DNA promotors for genetic expression. These studies, amplified by the isolation of a potentially significant immunoprecipitable 44,000-dalton recombinant protein antigen, point to the importance of the "cloned antigen gene" approach for the eventual eludication of specific antigens or immunogens operative in the pathogenesis, immunology, and serodiagnosis of T. pallidum infection.

Antigens, Bacterial↗
PubMed1982

Murine monoclonal antibodies specific for virulent Treponema pallidum (Nichols).

Murine anti-Treponema pallidum (Nichols) lymphocyte hybridoma cell lines secreting monoclonal antibodies against a variety of treponemal antigens have been generated. Hybridomas isolated were of three major types: those that were directed specifically against T. pallidum antigens, those that were directed against treponemal group antigens (as evidenced by their cross-reactivity with T. phagedenis biotype Reiter antigens), and those that cross-reacted with both treponemal as well as rabbit host testicular tissue antigens. The majority (31 of 39 clones) of these anti-T. pallidum hybridomas, which produced monoclonal antibodies of mouse isotypes immunoglobulin G1 (IgG1), IgG2a, IgG2b, IgG3 or IgM, were directed specifically against T. pallidum and not other treponemal or rabbit antigens tested by radioimmunoassay. Four of these T. pallidum-specific hybridomas secreted monoclonal antibodies with greater binding affinity for "aged" rather than freshly isolated intact T. pallidum cells, suggesting a possible specificity for "unmasked" surface antigens of T. pallidum. Six anti-T. pallidum hybridomas produced complement-fixing monoclonal antibodies (IgG2a, IgG2b, or IgM) that were capable of immobilizing virulent treponemes in the T. pallidum immobilization (TPI) test; these may represent biologically active monoclonal antibodies against treponemal surface antigens. Three other hybridomas secreted monoclonal antibodies which bound to both T. pallidum and T. phagedenis biotype Reiter antigens, thus demonstrating a possible specificity for treponemal group antigens. Five hybridoma cell lines were also isolated which produced IgM monoclonal antibodies that cross-reacted with all treponemal and rabbit host testicular tissue antigens employed in the radioimmunoassays. This report describes the construction and characteristics of these hybridoma cell lines. The potential applications of the anti-T. pallidum monoclonal antibodies are discussed.

Aging↗
PubMed1981

Plasmid DNA in Treponema pallidum (Nichols): potential for antibiotic resistance by syphilis bacteria.

A plasmid DNA structure (approximate molecular weight = 7.5 X 10(6)) was identified in the human pathogen Treponema pallidum (Nichols). The inability to isolate this plasmid from rabbit host tissue and the total lack of DNA homology of the plasmid with rabbit DNA has confirmed its Treponema pallidum origin. The observation documents a newly recognized and potentially significant genetic capability for Treponema pallidum.

Animals↗
PubMed1980

On the cloning of eukaryotic total poly(A)-RNA populations in Escherichia coli.

A total clone bank of cDNAs synthesized from mouse liver poly(A)-RNA was constructed in Escherichia coli K-12 RR1 using the plasmid pBR322. Sequences of cDNAs were inserted into the PST-I site of pBR322 by the "G-C-tailing" method. Bulk preparations of these cDNA sequences were obtained by treatment of the resultant total hybrid plasmid population with PST-I. Aliquots of this cDNA material were then labeled with 32P by "nick translation" using E. coli DNA polymerase I for the preparation of hybridization probes. Experiments involving the back-hybridization of these probes to the total hybrid-plasmid clone bank population revealed that virtually all of the liver poly(A)-RNA sequences were represented in the total clone bank. The long term stability of these sequences residing in RR1 host cells was then examined through extensive serial passage of the initial total clone cell population culture. The results showed: 1) that the small percentage of natural pBR322 molecules (containing no cDNA inserts) usually present in such total clone bank preparations do not outgrow the respectively hybrid specie of plasmids in these populations: 2) few, if any, cDNA sequences are completely lost; and 3) some redistribution of the abundant and more unique DNA sequences probably does occur. The use of total clone hybrid-plasmid populations (constructed from poly(A)-RNA isolated from different tissues) described here should allow the identification of tissue-specific RNA sequences through the use of cross-hybridizaton techniques.

Animals↗
PubMed1980

Heterogeneity of deoxyribonucleic acid molecules isolated from Mycobacterium smegmatis.

Bulk chromosomal deoxyribonucleic acids (DNAs) of Mycobacterium smegmatis strains 607+ (wild type) and 607-1 (Strr) and orange-red pigmented variants (OR) were separated into two distinct bands (types 1 and 2) by cesium chloride density gradient centrifugation. Thermal denaturation analyses showed that type 1 and 2 DNA fragments of these strains possessed guanine plus cytosine contents averaging 69.2% and 60.8%, respectively. Type 1 and 2 DNAs from all strains tested were recovered in relatively equal quantities upon isolation and were found to have similar molecular weights (3.0 x 10(7)). Spectrophotometric assay of DNA reassociation showed that homology between any type 1 and 2 DNA fragments was always very low (29 to 33%), even within the same strain. Homologies among type 1 DNAs isolated from any strain were always high (92 to 98%), whereas homologies between type 2 DNA isolated from OR strains and that from their parental strain 607-1 were lower (51 to 55%). Transformation experiments revealed that methionine, leucine, folic acid, and streptomycin markers were found exclusively in type 1 DNA fragments. In addition to the two types of chromosomal DNA, plasmid DNA possessing a molecular weight of about 4 x 10(6) was found in strain 607-1.

Base Sequence↗
PubMed1979

Increased amplification of pBR322 plasmid deoxyribonucleic acid in Escherichia coli K-12 strains RR1 and chi1776 grown in the presence of high concentrations of nucleoside.

When pBR322 plasmid-harboring Escherichia coli strains RR1 or chi1776 were grown in the presence of 1 mg of uridine or cytidine per ml and later treated with chloramphenicol, as much as three times more plasmid deoxyribonucleic acid was recovered than would normally be obtained by routine plasmid amplification procedures.

Culture Media↗
PubMed1978

Factors affecting the transformation of Escherichia coli strain chi1776 by pBR322 plasmid DNA.

The susceptibility of E. coli strain chi1776 to transformation by pBR322 plasmid DNA was examined and optimized. Maximum transformation to tetracycline (Tc) resistance was achieved when cells were harvested from L broth at 5.0--6.0 . 10(7) cfu/ml, followed by washing twice in cold 0.1 M NaCl + 5 mM MgCl2 + 5 mM Tris, pH 7.6. Cells grown in the presence of D-cycloserine (Cyc) rather than nalidixic acid (Nx) transformed markedly better. The presence of 5 mM Mg2+ ions in washing and CaCl2 solutions stimulated transformation about 2-fold. Optimal conditions for transformation included a pH range of 7.25-7.75 and a cell-to-DNA ratio of about 1.6 . 10(8) cfu/ng plasmid DNA. The frequency of transformation was highest when cells were exposed to 100 mM CaCl2 in 250 mM KCl + 5 mM MgCl2 + 5 mM Tris, pH 7.6, before mixing with DNA. A 60 min incubation period for cell + DNA mixtures held on ice produced the maximum number of Tcr transformants. In our hands, heat shocks at 37 degrees C or 42 degrees C for various times all decreased transformation to about one-half of optimal levels. Furthermore, the recovery of transformants was best when cell + DNA mixtures were plated on precooled (4 degrees C) Tc agar plates. The efficiency of plating was optimum when only 5 microliter of cell + DNA mixture was spread per plate, suggesting that non-viable background chi1776 cells on selective medium inhibited the recovery of transformants. It was also found that the presence of linear DNA molecules in cell + DNA mixtures markedly inhibited the transformation of chi1776 by pBR322 plasmid DNA. On the basis of these findings, a new procedure for the plasmid-specific transformation of E. coli chi1776 by pBR322 plasmid DNA is proposed. The use of this technique has allowed us to attain transformation frequencies in excess of 10(7) transformants/microgram pBR322 plasmid DNA.

Calcium Chloride↗
PubMed1978

Physiological factors involved in the transformation of Mycobacterium smegmatis.

Transfer of streptomycin resistance and changes from methionine and leucine auxotrophy to prototrophy were achieved in Mycobacterium smegmatis by transformation. Recipient cells were more resistant to mitomycin C and methyl methlanesulfonate treatments than were wild-type cells. A high level of calcium ions was essential for transformation, especially during DNA adsorption, whereas the presence of magnesium ions and the exposure of recipient cells to mild doses of UV light enhanced recombination frequencies. Transformants were not isolated when recipient cell-DNA mixtures were first treated with deoxyribonuclease. Recipient cells at various stages of growth showed similar transformabilities. Transformation was successful only when recipient cells were incubated on rich agar medium after mixture with DNA. Exposure of recipient cells to Pronase before treatment with donor DNA did not affect transformation, suggesting the absence of a protein competence factor. Throughout the present experiments, cotransformation frequencies were very low and unselected-marker segregation patterns were independent, indicating that the methionine, leucine, and streptomycin markers are not closely linked in M. smegmatis.

Calcium↗
PubMedDate not supplied

Solid-phase synthesis of biologically active lipopeptides as analogs for spirochetal lipoproteins.

Bacterial lipoproteins, which are of particular interest because of their immunomodulatory activities, share a common N-terminal structural motif that consists of an N-acyl-S-diacylglyceryl cysteine residue. Synthetic tripalmitoylated analogs of the N-terminal sequences of several bacterial lipopetides have been found to reproduce the immunological activities of the corresponding intact lipoproteins. Methods for the synthesis of lipopeptide analogs of bacterial lipoproteins have hitherto relied upon the coupling of peptide moieties, lacking the N-terminal cystienyl residue, with a tripalmitoylglyceryl cysteine moiety synthesized separately in solution. A method is described here by which rapid and convenient synthesis of the entire lipopeptide is accomplished by solid-phase methods in which the N-terminal cysteinyl derivative is assembled stepwise while attached to the completed peptide moiety prior to cleavage from the resin. The method has been used to synthesize two lipohexapeptides representing the N-terminal sequences of the 47-kDa membrane lipoprotein of the syphilis spirochete, Treponema pallidum, and the outer surface protein A (OspA) of the Lyme disease spirochete, Borrelia burgdorferi. These lipopeptides, which were synthesized without detectable endotoxin contamination, exhibit macrophage-stimulating activity that is not expressed by the corresponding non-acylated hexapeptides. The data indicate that synthetic lipopeptides based on spirochetal lipoproteins are appropriate substitutes for the intact lipoproteins in immunological studies.

Amino Acid Sequence↗