bluuebunny/crossref_metadata_2025 huggingface dataset:
Isolation and characterization of the Streptococcus mutans gtfC gene, coding for synthesis of both soluble and insoluble glucans
Authors: Hanada N , Kuramitsu H K
Published: January 2020

The intact gtfC gene from Streptococcus mutans GS-5 was isolated in Escherichia coli in plasmid vector pUC18. The glucosyltransferase activity expressed by the gene synthesized both low-molecular-weight water-soluble glucan and insoluble glucan in a primer-independent manner. Purification of the enzyme by procedures that minimize proteolytic digestion yielded a purified preparation with a molecular weight of 140,000. Insertional inactivation of the gtfC gene with a streptococcal erythromycin resistance gene fragment followed by transformation of strain GS-5 suggested that the gtfC gene product was required for sucrose-dependent colonization in vitro. In addition, evidence for the presence of a third gtf gene coding for soluble glucan synthesis was obtained following the construction of mutants containing deletions of both the gtfB and gtfC genes.
Influence of genetic background on host resistance to experimental murine tularemia
Authors: Anthony L S , Skamene E , Kongshavn P A
Published: January 2020

The host response to experimental murine tularemia was examined in different inbred mouse strains. The kinetics of growth of Francisella tularensis live vaccine strain (LVS) in the livers and spleens of A and C57BL/6 mice were monitored, and it was observed that mice of the A strain were more susceptible to the proliferation of LVS than were C57BL/6 mice. The difference was most marked 5 days following infection, when the number of bacteria isolated from the spleens of A mice was found to exceed that of C57BL/6 mice by 100-fold. In addition, the C57BL/6 strain exhibited a more pronounced splenomegaly 8 days after infection than did the A strain. When the response of other inbred strains was evaluated by determining the splenic count of LVS on day 5 postinfection, several levels of antiularemic resistance were observed. Mice of the AKR, BALB/cBy, C57BL/10, and SJL strains were found to be most resistant, while SM mice were most susceptible to the proliferation of LVS. The DBA/2, CBA, 129, C3H/HeJ, and A strains expressed a resistance phenotype which was intermediate between the two extremes, with A and C3H/HeJ mice being somewhat more susceptible than DBA/2, CBA, or 129 mice. The trait of resistance or susceptibility was analyzed genetically in (C57BL/6 x A)F1 hybrid mice and in F2 generation and recombinant inbred (RI) mouse strains derived from C57BL/6 (resistant) and A (susceptible) strain progenitors. The F1 progeny exhibited a level of resistance to infection which was similar to that of the resistant parent. In both the F2 generation mice and the RI strains, a continuous spectrum of resistance levels was observed. The results of these experiments indicate that the genetic background of the host influences host resistance to experimental murine tularemia and that multiple genetic loci are involved in this response.
Colony opacity, hemadsorption, hemolysis, and mitogenicity are not associated with virulence of Mycoplasma pulmonis
Authors: Davidson M K , Ross S E , Lindsey J R , Cassell G H
Published: January 2020

Colony opacity, hemadsorption and hemolysis of erythrocytes, and the ability of whole mycoplasmal cells to induce a blastogenic response when incubated with C3H/HeN or C57BL/6 mouse lymphocytes were examined for 18 strains of Mycoplasma pulmonis to determine if any of these characteristics could be associated with virulence in vivo. Although there were differences among strains in each of these characteristics, none of these parameters were associated with virulence.
Differences in uptake of mycobacteria by human monocytes: a role for complement
Authors: Swartz R P , Naai D , Vogel C W , Yeager H
Published: January 2020

We investigated the influence of serum factors on the uptake of various species of mycobacteria by human peripheral blood monocytes (PBM). On the basis of the percentage of PBM involved during in vitro uptake, the mycobacteria were of two distinct groups. The mycobacteria of one group, which consisted of Mycobacterium avium complex and M. chelonae, were taken up by many PBM; the other group, consisting of M. tuberculosis, M. kansasii, M. fortuitum, and M. gordonae, were taken up by fewer PBM. M. scrofulaceum was intermediate to these two groups on the basis of its uptake by PBM. Serum depleted of complement by heating or treatment with cobra venom factor significantly reduced the extent of PBM involvement with M. avium complex, indicating that complement is an important serum component mediating the uptake of M. avium complex organisms. Preincubation of mycobacteria with serum containing 10 mM EGTA [ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid] and 10 mM MgCl2 resulted in uptake by a high percentage of PBM, while preincubation in heated serum or serum containing 10 mM EDTA resulted in a significantly reduced percentage of PBM involved in uptake of M. avium complex organisms, indicating that these organisms are activators of the alternative pathway of complement. Incubation of M. avium complex organisms in human serum consumed 51% of the hemolytic complement activity. Parallel experiments indicated that serum had a lesser effect on the uptake of M. tuberculosis. Thus, serum is important in in vitro M. avium complex uptake by PBM; complement has a major role in the effect of serum, but this role is less important with M. tuberculosis.
Provocation of pulmonary vascular endothelial injury in rabbits by human recombinant interleukin-1 beta
Authors: Goldblum S E , Yoneda K , Cohen D A , McClain C J
Published: January 2020

Interleukin-1 (IL-1) mediates components of the acute-phase response, stimulates granulocyte metabolism, and induces endothelial cell surface changes. We studied the effects of human recombinant IL-1 beta (rIL-1 beta) or rIL-1 alpha on circulating granulocytes, their sequestration within the pulmonary microvasculature, pulmonary edema formation, and changes in pulmonary vascular permeability to 125I-labeled albumin. rIL-1 beta administration induced significant (P less than 0.03) but transient granulocytopenia followed by significant (P less than 0.04) neutrophilia and significant (P less than 0.04) pulmonary leukostasis compared with saline-infused rabbits. Rabbits preinfused with 125I-labeled rabbit serum albumin and administered saline, rIL-1 beta, or rIL-1 alpha were sacrificed, and lung wet/dry weight ratios and bronchoalveolar lavage fluid and plasma 125I activities determined. Both rIL-1 beta and rIL-1 alpha increased lung wet/dry weight ratios (P less than 0.025 and P less than 0.01, respectively) compared with saline controls. rIL-1 beta increased bronchoalveolar lavage fluid/plasma 125I radioactivity ratios (P less than 0.025). Electron microscopic analysis of lung sections obtained from rIL-1 beta-infused animals demonstrated endothelial injury, perivascular edema, and extravasation of an ultrastructural permeability tracer. The observation that human rIL-1 can evoke acute pulmonary vascular endothelial injury and lung edema in rabbits supports the hypothesis that IL-1 may play a role in the pathogenesis of the adult respiratory distress syndrome.
Parameters of Mycoplasma pneumoniae infection in Syrian hamsters
Authors: Barile M F , Chandler D K , Yoshida H , Grabowski M W , Harasawa R , Razin S
Published: January 2020

An animal model for evaluating the potency of Mycoplasma pneumoniae vaccines was developed with hamsters. Factors that influence hamster infection by M. pneumoniae were defined, and parameters for assessment of intensity of pulmonary disease were established. Colonization of hamster lungs was determined by culture, and intensity of lung disease was assessed histopathologically and expressed numerically as a lung pathological score. Intratracheal inoculation of the challenge was superior to the intranasal or aerosol route for inducing a consistent degree of lung disease. A challenge dose of 10(6) CFU inoculated intratracheally produced lung colonization and significant reproducible lung pathological scores in essentially all unvaccinated animals. The peak of infection, as determined by these criteria, was at about 2 weeks after challenge. Animals over 6 weeks of age were preferable for the test, since younger animals exhibited a lower lung pathological score even though they showed the same degree of lung colonization. The hamster assay developed provides a dependable experimental system for testing the protective potency of M. pneumoniae vaccines.
Staphylococcus saprophyticus urease: characterization and contribution to uropathogenicity in unobstructed urinary tract infection of rats
Authors: Gatermann S , John J , Marre R
Published: January 2020

We studied the biochemical properties of the urease of Staphylococcus saprophyticus and the possible role of the urease in experimental urinary tract infections. For this purpose, the nonhemagglutinating and nonadherent strain 9325, which was isolated from a case of symptomatic urinary tract infection, was used. The urease was shown to have a Km of 6.64 mM urea and a Vmax of 4.59 mumol NH3.min-1.mg-1. The enzyme was inhibited by acetohydroxamic acid in a noncompetitive manner. By means of Sephacryl S-300 column chromatography, we determined a mean molecular weight (+/- standard error of the mean) of 420,000 +/- 16,000. To assess the contribution of S. saprophyticus urease to uropathogenicity, a urease-negative mutant was constructed by nitrosoguanidine mutagenesis. In the rat model of ascending unobstructed urinary tract infection, higher numbers of CFU.gram of tissue-1 and more-severe lesions were detected with the parent strain. Moreover, bladder stones were found in animals infected with the urease-positive strain only. Interestingly, the difference in mean bacterial counts of the bladders was found to be significant by the Wilcoxon two-sample test (P less than 0.05), whereas that between the kidney bacterial counts was not. Immunoblot studies revealed a faint antibody response in rats infected with the mutant strain, although bacteria could still be detected in the kidneys after 7 days. Sera of animals challenged with the parent strain reacted strongly with many antigens of S. saprophyticus. Our data indicate that urease is a major factor for invasiveness of S. saprophyticus, especially in the tissue of the bladder, whereas persistence in the urinary tract and nephropathogenicity of this organism are governed by factors other than urease.
Candidacidal activities of proteins partially purified from rat epidermis
Authors: Kashima M , Takahashi H , Shimozuma M , Epstein W L , Fukuyama K
Published: January 2020

Proteins with approximate molecular weights of greater than 300,000 (EP greater than 300K) and 49,000 (EP 49K) were partially purified from terminally differentiated cells of 2-day-old rat epidermis. They were extracted in 0.34 M sucrose containing 0.01 M citric acid and purified by Sephacryl S-300 chromatography followed by reverse-phase column chromatography. The major constituents of EP greater than 300K and EP 49K were focused around pH 10 to 11 by sucrose gradient isoelectric focusing. Both proteins were effective at inhibiting colony formation of Candida albicans and C. tropicalis, but neither inhibited the growth of C. parapsilosis. The effect was maximum below pH 5.0 and reduced considerably above pH 5.0. The activity of EP greater than 300K on C. albicans TIMM 1623 (group A) was much stronger than that of EP 49K, whereas both proteins similarly inhibited C. albicans TIMM 1604 (group B). Their effects against C. albicans TIMM 1623 were dose dependent and were activated after a longer preincubation time, and NaCl concentration influenced their potency. At a low salt concentration and a 60-min preincubation at pH 4.5, the 50% effective dose for EP greater than 300K was calculated to be 1.7 x 10(-9) M, whereas that for EP 49K was 1.8 x 10(-7) M.
Intestinal multiplication of Mycobacterium paratuberculosis in athymic nude gnotobiotic mice
Authors: Hamilton H L , Follett D M , Siegfried L M , Czuprynski C J
Published: January 2020

In this study gnotobiotic mice were inoculated with a human isolate of Mycobacterium paratuberculosis (strain Linda; ATCC 43015) in an attempt to investigate the pathogenesis of intestinal paratuberculosis. Mycobacterium paratuberculosis-monoassociated nu/+ mice developed a persistent low-level intestinal infection but did not support progressive bacillary multiplication. In contrast, monoassociated nu/nu mice eventually harbored approximately 10(7) M. paratuberculosis per g of intestinal tissue. Acid-fast bacilli and granulomas were observed in the intestinal mucosa and livers of nu/nu but not nu/+ mice. Similar results were obtained after intragastric inoculation of M. paratuberculosis into nu/+ and nu/nu flora-defined mice. These observations suggest that the presence of an intact cellular immune system is important for limiting intestinal multiplication of M. paratuberculosis. The results of this study may be relevant to our understanding of the pathogenesis of Johne's disease in ruminants and of human inflammatory bowel diseases that have a mycobacterial etiology (e.g., some cases of Crohn's disease and Mycobacterium avium-Mycobacterium intracellulare enteritis in patients with acquired immunodeficiency syndrome).
Phospholipase A activity associated with the growth of Rickettsia prowazekii in L929 cells
Authors: Winkler H H , Daugherty R M
Published: January 2020

Cultured L929 cells infected with Rickettsia prowazekii had a greatly increased rate of hydrolysis of fatty acid from the oleic acid-radiolabeled phospholipids of the host cell membranes. The incorporation of fatty acid into phospholipid in an infected cell was only moderately inhibited relative to a mock-infected cell. Thus, even if the release of fatty acid from phospholipid represented a steady state between hydrolysis and resynthesis of phospholipids, the increase in release of fatty acid was due principally to increased phospholipase A activity. The increased rate of hydrolysis did not occur only late in the rickettsial infection; this activity began early in infection and continued throughout the course of infection. The addition of tetracycline or chloramphenicol (antibiotics which inhibit rickettsial protein synthesis) to the infected cells caused a rapid and total abatement of this increased rate of phospholipid hydrolysis. In contrast, high concentrations of penicillin affected the morphology of the intracellular rickettsiae, but did not inhibit the phospholipase activity. This phospholipase A activity clearly damages the host cell during the rickettsial infection and may represent the activity by which R. prowazekii escapes from the host cell.
Demonstration of antigen-specific T cells and histopathological alterations in mice experimentally inoculated with Borrelia burgdorferi
Authors: Schaible U E , Kramer M D , Justus C W , Museteanu C , Simon M M
Published: January 2020

Antigen-specific T-cell responses and histopathological changes were studied in mice experimentally inoculated with Borrelia burgdorferi B31. Inbred mice with different H-2 haplotypes and/or different genetic backgrounds were inoculated with B. burgdorferi organisms and tested for antigen-specific T-cell responses in vivo (delayed-type hypersensitivity [DTH]) and in vitro (T-cell proliferation). Comparable DTH responses were found after inoculation with either inactivated (in the presence of adjuvants) or viable microorganisms in all mouse strains, except BALB/c, irrespective of the H-2 haplotype (b, d, k, or s) tested and the sex of the animals. Moreover, in mice presensitized to B. burgdorferi, DTH responses could be induced only with antigen preparations derived from the corresponding strain but not with those obtained from either related spirochetes such as Treponema phagedenis and Leptospira interrogans or unrelated bacteria such as Mycobacterium tuberculosis. T cells isolated from lymph nodes or spleens of mice previously sensitized to B. burgdorferi but not those from naïve mice could be induced for antigen-specific proliferation in vitro, as revealed by [3H]thymidine incorporation. Histopathological examination of mice inoculated with viable B. burgdorferi organisms revealed significant perivascular infiltrates consisting mainly of mononuclear and a few polymorphonuclear leukocytes in different organs (brain, heart, lungs, liver, and kidneys) and the appearance of giant multinucleated cells within the spleen similar to those found in human skin specimens of patients suffering from cutaneous manifestations of Lyme disease. Our findings suggest that mice are a suitable animal model with which to study the immune response to B. burgdorferi and the pathogenesis of Lyme disease.
Identification of an extracellular protein of Listeria monocytogenes possibly involved in intracellular uptake by mammalian cells
Authors: Kuhn M , Goebel W
Published: January 2020

Mutants of Listeria monocytogenes were recently isolated which are impaired in the synthesis of a major extracellular protein (p60). As shown in this investigation, the p60 mutants have lost the capability of invading nonprofessional phagocytic 3T6 mouse fibroblast cells. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of supernatant proteins of these mutants indicated that no other extracellular protein was altered in these mutants. The p60 mutants formed long cell chains which disaggregated to normal-sized single bacteria upon treatment with partially purified p60. These disaggregated bacterial cells were able to invade 3T6 cells. Physical disruption of the cell chains by ultrasonication produced similar single cells which were, however, noninvasive. Treatment of these ultrasonicated mutant cells with wild-type p60 restored their ability to invade 3T6 cells.
Antibody response to Ehrlichia risticii and antibody reactivity to the component antigens in horses with induced Potomac horse fever
Authors: Dutta S K , Mattingly B L , Shankarappa B
Published: January 2020

The antibody response and the antibody reactivity to component antigens of Ehrlichia risticii were studied in horses with induced Potomac horse fever. These horses had no detectable antibodies to E. risticii in their preinoculation (PrI) sera by indirect fluorescent-antibody assay and enzyme-linked immunosorbent assay (ELISA). All the horses exhibited typical disease features following experimental infection and responded with specific antibodies, as measured by ELISA and indirect fluorescent-antibody assay. A primary antibody response was detected in 70% of the horses, while a secondary-type antibody response was detected in 30% of the horses by ELISA. In the primary antibody response, a distinct titer was observed at 2 weeks postinoculation (PI), when the immunoglobulin M (IgM)/IgG ratio was 2 to 5, and the overall antibody titer peaked at 6 to 8 weeks PI. The secondary-type antibody response exhibited a characteristic titer at 1 week PI, the IgM and IgG titers were about equal at 2 weeks PI, and the overall antibody titer peaked at 6 weeks PI. A transient depression in the IgG response at 4 weeks PI was observed in both response types. The antibody was maintained at a high titer for over a year in all horses. Western immunoblot reactivity showed that the antisera collected from these infected horses at 4 to 5 weeks PI recognized some or all of the six major E. risticii component antigens (70, 55, 51, 44, 33, and 28 kilodaltons), all of which were apparent surface components. The 6- to 8-week PI antisera recognized up to 16 component antigens, including 9 major antigens (110, 86, 70, 55, 51, 49, 44, 33, and 28 kilodaltons). However, the PrI sera of these horses showed reactivity at various intensities with one to seven of the component antigens. There was no apparent correlation between this reactivity pattern and the subsequent antibody response types.
Type 1 pili are not necessary for colonization of the streptomycin-treated mouse large intestine by type 1-piliated Escherichia coli F-18 and E. coli K-12
Authors: McCormick B A , Franklin D P , Laux D C , Cohen P S
Published: January 2020

Escherichia coli F-18, an excellent colonizer of the streptomycin-treated mouse large intestine, produces type 1 pili. E. coli F-18 FimA-, type 1 pilus negative, and E. coli F-18 FimH-, type 1 pilus positive but adhesin negative, were constructed by bacteriophage P1 transduction of defective fimA and fimH genes from the E. coli K-12 strains ORN151 and ORN133, respectively, into E. coli F-18. Adhesion of E. coli F-18 to an immobilized mannose-bovine serum albumin glycoconjugate was about sixfold greater than that of either E. coli F-18 FimA- or E. coli F-18 FimH-, and adhesion of E. coli F-18 to immobilized cecal epithelial cell brush border membranes was between two- and threefold greater than that of E. coli F-18 FimA- or E. coli F-18 FimH-. When either E. coli F-18 FimA- or E. coli FimH- was fed to streptomycin-treated mice together with E. coli F-18, the pilus-negative and adhesin-negative strains colonized as well as their type 1-piliated parent. Essentially the same result was observed when the type 1-piliated E. coli K-12 strain ORN152 was fed to streptomycin-treated mice together with a nearly isogenic K-12 FimA- strain, ORN151. Furthermore, when streptomycin-treated mice were fed E. coli F-18 FimA- or E. coli F-18 FimH- together with E. coli F-18 Col-, which also makes type 1 pili but is a poor colonizer relative to E. coli F-18 because it grows poorly in mucus in the presence of E. coli F-18, the F-18 FimA- and F-18 FimH- strains colonized well (10(6) to 10(7) CFU/g of feces), whereas the number of E. coli F-18 Col- in feces decreased rapidly to 10(2) CFU/g of feces. These data show that in streptomycin-treated mice, the inability to produce functional type 1 pili has no effect on the ability of E. coli F-18 and E. coli K-12 to colonize the large intestine.
Inactivation of botulinum and tetanus toxins by chelators
Authors: Bhattacharyya S D , Sugiyama H
Published: January 2020

Purified type A botulinum toxin of about 10(6) mouse 50% lethal doses per ml was greater than 99.9% inactivated when incubated at pH 7.4 for 30 min at 37 degrees C in 20 mM 1,10-phenanthroline (PTL) or 2,2'-dipyridyl (DPD) and was 96% inactivated when incubated in 70 mM 8-hydroxyquinoline-5-sulfonic acid (HQL), but was not affected when incubated in 200 mM EDTA. When used as a representative of the chelating agents, PTL inactivated greater than or equal to 99.9% of toxicity in the culture filtrate of C. botulinum type A, B, and E strains. Highly purified tetanus toxin at 2.5 x 10(5) 50% lethal doses per ml lost all toxicity in 40 mM PTL or 150 mM DPD but was not detectably affected by 100 mM HQL (the highest concentration possible). Toxin inactivation by 20 mM PTL was completely blocked when the PTL was prereacted with an equimolar amount of Zn2+ and significantly reduced when it was preincubated with one-third its molar amount of Fe2+. DPD at 20 mM had little toxin-inactivating potency when preincubated with an equimolar amount of Zn2+ and only some of this potency when preincubated with an equimolar amount of Fe2+. Toxicity was not recovered by adding Zn2+ or Fe2+ to PTL-treated toxin. Neutron activation analysis of type A toxin showed that for each toxin molecule present, there was 1 atom of Fe, 0.4 atom of Zn, and 22 to 55 atoms each of Ca and Mg. The biological activity of botulinum toxin seems to depend on a metal component, which is likely to be Fe.
Generation of monoclonal antibodies to the specific sugar epitopes of Mycobacterium avium complex serovars
Authors: Rivoire B , Ranchoff B J , Chatterjee D , Gaylord H , Tsang A Y , Kolk A H , Aspinall G O , Brennan P J
Published: January 2020

Monoclonal antibodies have been generated to the unique distal sugar epitopes on the oligosaccharide haptens of the glycopeptidolipid antigens of clinically prominent members of the Mycobacterium avium serocomplex. Thus, antibodies are described that recognize the distal O-acetyl-alpha-L-rhamnopyranosyl residue of the specific glycopeptidolipid of M. avium serovar 1, the 4-O-acetyl-2,3-di-O-methyl-alpha-L-fucopyranose of serovar 2, the 4-O-methyl-alpha-L-rhamnopyranosyl-(1----4)-2-O-methyl-alpha-L- fucopyranosyl unit of serovar 4, the 4,6-(1'-carboxyethylidene)-3-O-methyl-beta-D-glucopyranosyl unit of serovar 8 [and the 4,6-(1'-carboxyethylidene)-beta-D-glucopyranosyl residue of serovar 21], and the 4-O-acetyl-2,3-di-O-methyl-alpha-L-fucopyranosyl-(1----4)-beta-D- glucuronopyranosyl unit of serovar 9. Epitope definition was arrived at through use of the pure, chemically defined glycopeptidolipid antigens and neoglycoproteins containing the chemically synthesized distal sugars of some select serovars. These monoclonal antibodies combined with the already published information on the structure of the antigen determinants and the tools used to arrive at these structures provide powerful means for fundamental studies on the role of these antigens in immunopathogenesis and for the precise mapping of the epidemiology of opportunistic infections caused by M. avium.
Modulation of leukotriene generation by pertussis toxin
Authors: Hensler T , Raulf M , Megret F , Alouf J E , König W
Published: January 2020

The purpose of our study was to characterize the properties of the interaction of pertussis toxin with human polymorphonuclear leukocytes for the modulation of leukotriene generation and metabolism. The cells were stimulated with either the Ca ionophore A23187, opsonized zymosan, or the bacterial peptide formyl-methionyl-leucyl phenylalanine. Incubation of the cells with pertussis toxin led to a rapid inhibition of LTB4 generation when formyl-methionyl-leucyl phenylalanine was used as the stimulus, whereas there was no effect with the Ca ionophore and just a low effect with opsonized zymosan. The inhibition of leukotriene generation was dependent on the incubation time, temperature, and pertussis toxin concentration. The effect was not dependent on the presence of calcium. Incubation of the cells with guanosine 5'-O-(3-thiotriphosphate) the stable analog of GTP, led to a time-dependent increase in leukotriene generation induced by formyl-methionyl-leucyl phenylalanine which was abolished by the simultaneous addition of pertussis toxin. Our data suggest that the formyl-methionyl-leucyl phenylalanine-induced generation of leukotrienes is dependent on a GTP-binding protein. The participation of the various G proteins has yet to be elucidated.
Immunoelectron microscopy of lipopolysaccharide in Chlamydia trachomatis
Authors: Birkelund S , Lundemose A G , Christiansen G
Published: January 2020

Monoclonal antibodies (MAb) specific for Chlamydia trachomatis lipopolysaccharide (LPS) and major outer membrane protein (MOMP) were used for immunoelectron microscopy analysis. MAb specific for MOMP showed strong reaction with the chlamydial surface, whereas MAb specific for LPS showed strong association of gold particles with the periphery of the chlamydial body. After fixation of the chlamydia cells, the reactivity was, however, similar to the anti-MOMP reactivity. Enzyme-linked immunosorbent assay showed that MAb specific for LPS could remove LPS from the chlamydial membrane.
Comparison of immunosuppressive effects of cyclosporine A in a murine model of systemic candidiasis and of localized thrushlike lesions
Authors: Krause M W , Schaffner A
Published: January 2020

Candida albicans is an opportunistic human pathogen preferentially causing invasive and disseminated infection in patients with defective phagocytic defenses and serious mucocutaneous infection in patients with deficient T-cell function. Phagocytes appear to protect the host from fungal invasion even in the absence of adaptive immune mechanisms, while as-yet-undefined T-cell-dependent factors seem necessary for control of C. albicans on body surfaces. To study host defense mechanisms on body surfaces, we developed a new model of thrush in artificial pneumatized cysts in mice. Cyclosporine A, a relative selective suppressor of T-cell-mediated immunity and natural killer cell activity, promoted the formation of thrushlike lesions on cyst surfaces and impeded elimination of C. albicans from such lesions. As expected from the absence of an impairment of antimicrobial phagocytic activity, cyclosporine A had no effect on systemic candidiasis induced by intravenous inoculation. Surprisingly, athymic nude mice were not more susceptible to superficial candidiasis than control mice and were comparably affected by cyclosporine A. In contrast, beige mice, which in addition to phagocytic dysfunction have reduced natural killer cell activity, were more susceptible to thrushlike lesions, and cyclosporine A was correspondingly less active in this mouse strain. Immunosuppression with cyclosporine A affects host defense mechanisms which are operative against superficial candidiasis but appear superfluous in resistance to the invasive form of this mycosis, an indication for the divergent nature of host defense against the two forms of candidiasis.
Pentoxifylline modulation of plasma membrane functions in human polymorphonuclear leukocytes
Authors: Hand W L , Butera M L , King-Thompson N L , Hand D L
Published: January 2020

Pentoxifylline is known to have major effects on cell membrane function in mammalian cells, including human leukocytes. The protective effects of this agent in animal models of infection and inflammation may be due to alterations in phagocyte (neutrophil and macrophage) function. However, the exact mechanism of action of pentoxifylline is unknown. In this study, we evaluated the effect of the drug on several membrane-associated activities in human polymorphonuclear neutrophils and investigated possible mechanisms for the observed changes in neutrophil function. Pentoxifylline inhibited ingestion of microbial particles (Staphylococcus aureus and zymosan); decreased superoxide generation activated by zymosan, formyl-methionyl-leucyl-phenylalanine, and concanavalin A (but not phorbol myristate acetate); and decreased uptake (transport) of adenosine stimulated by formyl-methionyl-leucyl-phenylalanine and zymosan. In contrast, pentoxifylline actually increased clindamycin uptake in zymosan-stimulated polymorphonuclear neutrophils. However, pentoxifylline had no effect on uptake of adenosine or clindamycin in unstimulated neutrophils. In comparison with known inhibitors of nucleoside transport (nitrobenzylthioinosine and dipyridamole), the results suggested that pentoxifylline does not bind to membrane nucleoside transport receptors. At concentrations which inhibit neutrophil function, pentoxifylline activity is not mediated through external membrane nucleoside regulatory sites. Thus, pentoxifylline affects the activation signal chain at a point beyond the membrane receptors. Whatever its precise mechanism of action, pentoxifylline has a striking modulatory effect on cell membrane-associated responses in stimulated leukocytes and may prove useful for control of injurious inflammatory states.
Serum antibody does not account for differences in the severity of chronic respiratory disease caused by Mycoplasma pulmonis in LEW and F344 rats
Authors: Simecka J W , Davis J K , Cassell G H
Published: January 2020

Chronic respiratory disease in rats, resulting from Mycoplasma pulmonis infection, is useful in the study of the immunological mechanisms in similar inflammatory diseases and provides a unique opportunity to study the interactions between systemic and mucosal immune systems in a naturally occurring infection. The present study examined the serum antibody responses to M. pulmonis in strains of rats which differ in disease progression and severity; LEW rats developed more severe disease than did F344 rats. Serum antibody responses were evaluated as to their levels, isotypes, and antigens recognized. Infected LEW rats produced greater or equal levels of the major classes of serum antibody to M. pulmonis than did infected F344 rats, suggesting that development of serum antibody responses alone does not resolve lesions and is not responsible for the difference in disease severity found in LEW and F344 rats. Although LEW rats produced higher responses in all subclasses of immunoglobulin G (IgG), the specific IgG response of LEW rats was composed predominately of IgG1 and IgG2a subclasses, while IgG2b was the major component of the IgG response in F344 rats. Finally, LEW rats responded more quickly to M. pulmonis antigens than did F344 rats, and there was no difference in the antigens eventually recognized by each strain, confirming previous work which suggested that LEW rats do not exhibit an unresponsiveness to a specific antigen(s) of M. pulmonis.
Listeriolysin O is essential for virulence of Listeria monocytogenes: direct evidence obtained by gene complementation
Authors: Cossart P , Vicente M F , Mengaud J , Baquero F , Perez-Diaz J C , Berche P
Published: January 2020

The role of listeriolysin O in the intracellular multiplication of Listeria monocytogenes and, therefore, its pathogenicity was questioned through a genetic complementation study. A nonhemolytic mutant was generated by inserting a single copy of transposon Tn917 in the bacterial chromosome. This insertion was localized by DNA sequence analysis in hlyA, the gene coding for listeriolysin O. As was another mutant that we previously characterized, this mutant was avirulent in the mouse. It was transformed with a plasmid carrying only hlyA, able to replicate in L. monocytogenes, and stably maintained in vitro and in vivo. The complemented strain displayed a hemolytic phenotype identical to that of the wild-type strain and was fully virulent, therefore attributing a crucial role to listeriolysin O in virulence and excluding the hypothesis of a polar effect of the transposon insertion on genes adjacent to hlyA and possibly involved in virulence.
Somnogenic activities of synthetic lipid A
Authors: Cady A B , Kotani S , Shiba T , Kusumoto S , Krueger J M
Published: January 2020

Bacterial infections and various immune response modifiers, including endotoxin and its lipid A moiety, alter sleep duration. The purpose of this study is to amplify our understanding of lipid A structure-somnogenic-pyrogenic activity relationships. Four synthetic disaccharide analogs of lipid A (LA-15-PP, LA-15-PH, LA-16-PH, and LA-18-PP) and a biosynthetic monosaccharide analog of lipid A (lipid X) were tested in rabbits for their effects on slow-wave sleep, rapid-eye-movement sleep, electroencephalographic slow-wave (0.5- to 4.0-Hz) amplitudes, and brain-colonic temperatures. Substances were injected intravenously and intracerebroventricularly. Compound LA-15-PP was the most potent; it significantly increased slow-wave sleep, delta electroencephalographic amplitudes, and brain-colonic temperatures while reducing rapid-eye-movement sleep. Compound LA-15-PH (monophosphoryl analog of LA-15-PP) induced effects similar to those of LA-15-PP, although the responses were weaker. Compound LA-18-PP induced increases in slow-wave sleep and delta amplitudes only after high doses, whereas compound LA-16-PH was devoid of these activities at the doses tested. Intracerebroventricular, but not intravenous, injections of lipid X induced small but significant increases in both slow-wave sleep and rapid-eye-movement sleep without affecting delta amplitudes or brain-colonic temperatures. These data suggest that the somnogenic actions of these lipid A analogs depend on the acylation or phosphorylation pattern and backbone structures of the molecules. Their soporific activities parallel their relative behaviors in other biological assays.
Molecular analysis and epidemiology of the Dr hemagglutinin of uropathogenic Escherichia coli
Authors: Nowicki B , Svanborg-Edén C , Hull R , Hull S
Published: January 2020

The genetic organization and epidemiology of Dr hemagglutinin was studied. Plasmids derived from pBJN406 and carrying transposon inserts were analyzed for their abilities to confer the mannose-resistant hemagglutination phenotype and expression of plasmid-encoded proteins. The 6.6-kilobase DNA fragment expressed five polypeptides with molecular masses of 15.5, 5, 18, 90, and 32 kilodaltons encoded by the draA, draB, draC, draD, and draE genes, respectively. Four genes, draA, draC, draD, and draE, were required for full mannose-resistant hemagglutination expression. Mutation in the draA gene, previously identified as encoding fimbrillin, resulted in loss of the adherence phenotype. We screened 658 strains isolated from patients with urinary tract infections (UTI) or from fecal samples for the presence of DNA sequences homologous to the draD gene. A significantly higher frequency of draD-related sequences was found among Escherichia coli strains from patients with cystitis than among strains from patients with other clinical forms of UTI. Association of draD-related sequences with O75 and other serotypes was observed. A possible role of Dr hemagglutinin as a virulence factor in lower UTI is discussed.
Immunochemical identification and preliminary characterization of a nonfimbrial hemagglutinating adhesin of Bacteroides gingivalis
Authors: Mouton C , Bouchard D , Deslauriers M , Lamonde L
Published: January 2020

A cell-bound hemagglutinating adhesin (HA-Ag2) of Bacteroides gingivalis was identified by crossed immunoaffinity electrophoresis as one of the common antigens of the species. A polyclonal antiserum with a restricted specificity for HA-Ag2 was produced by immunizing with the relevant immunoprecipitate excised from crossed-immunoelectrophoresis gels. The immunoglobulin G fraction of this monospecific antiserum inhibited hemagglutination. The antiserum was used against a cell surface extract of B. gingivalis in immunoblotting experiments, and we detected two antigens with apparent molecular masses of 33 and 38 kilodaltons in B. gingivalis ATCC 33277 and W83. Monoclonal antibody, C1.17, produced in another laboratory against B. gingivalis 381 and characterized as showing reactivity with a hemagglutinin of this strain (Y. Naito, K. Okuda, T. Kato, and I. Takazoe, Infect. Immun. 50:231-235, 1985), was also used to produce immunoblots of extracts of strains ATCC 33277 and W83. The apparent molecular masses of the major polypeptides recognized by monoclonal C1.17 in the immunoblots were the same as those detected by the polyclonal monospecific antiserum, i.e., 33 and 38 kilodaltons. Significantly, none of the polypeptides identified in this study corresponded to the polypeptide appearing in the 41- to 43-kilodalton region and identified by Yoshimura and co-workers (F. Yoshimura, K. Takahashi, N. Yoshinobu, and T. Suzuki, J. Bacteriol. 160:949-957, 1984) as the fimbrial protein characteristic of the species. Enzyme-linked immunosorbent assay inhibition experiments with the monospecific antiserum indicated that the cell surface extracts from strains ATCC 33277 and W83 were strong inhibitors, whereas the fimbria-enriched preparations from both strains failed to inhibit binding of antibodies to the cell surface antigens. As a whole, our study indicates that a nonfimbrial surface protein complex demonstrating erythrocyte-binding capacity, HA-Ag2, is common to three strains of B. gingivalis and is composed of at least two associated polypeptides with apparent molecular masses of 33 and 38 kilodaltons which share at least one antigenic determinant.
Neisseria lactamica and Neisseria meningitidis share lipooligosaccharide epitopes but lack common capsular and class 1, 2, and 3 protein epitopes
Authors: Kim J J , Mandrell R E , Griffiss J M
Published: January 2020

Neisseria lactamica, a common human pharyngeal commensal, contributes to acquired immunity to Neisseria meningitidis. To define the surface antigens shared between these two species, we used monoclonal antibodies (MAbs) to study 35 N. lactamica strains isolated in various parts of the world for cross-reactivity with meningococcal capsules, outer membrane proteins, and lipooligosaccharides (LOS). No N. lactamica strain reacted significantly with MAbs specific for capsular group A, B, C, Y, or W, and we were unable to extract capsular polysaccharide from them. Only 2 of 33 strains reacted weakly with MAbs against class 2 serotype proteins P2b and P2c. None reacted with MAbs specific for meningococcal class 1 protein P1.2 or P1.16 or class 2/3 serotype protein P2a or P15. Most N. lactamica strains (30 of 35) bound one or more of seven LOS-specific MAbs. Two LOS epitopes, defined by MAbs O6B4 and 3F11, that are commonly found on pathogenic Neisseria species were found on 25 of 35 N. lactamica. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting showed that the LOS of N. lactamica are composed of multiple components that are physically and antigenically similar to the LOS of pathogenic Neisseria species. Among four other commensal neisserial species, only Neisseria cinerea shared LOS epitopes defined by MAbs O6B4 and 3F11. Previous studies have shown that pharyngeal colonization with N. lactamica induces bactericidal antibodies against the meningococcus. We postulate that shared N. lactamica and meningococcal LOS epitopes may play an important role in the development of natural immunity to the meningococcus.
Protective monoclonal antibodies to Chlamydia trachomatis serovar- and serogroup-specific major outer membrane protein determinants
Authors: Zhang Y X , Stewart S J , Caldwell H D
Published: January 2020

Monoclonal antibodies exhibiting Chlamydia trachomatis serovar specificity (serovar A, B-Ba, or C) and serogroup specificity (B, intermediate, or C serogroup) were produced and characterized. These antibodies reacted with the major outer membrane protein, recognized epitopes located at the chlamydial cell surface, and passively neutralized chlamydial toxicity for mice. The antibodies should be useful reagents for defining the molecular structure of these protective epitopes, a necessary step toward the development of a subunit or recombinant C. trachomatis vaccine.
Rectification of two Escherichia coli heat-stable enterotoxin allele sequences and lack of biological effect of changing the carboxy-terminal tyrosine to histidine
Authors: Guzman-Verduzco L M , Kupersztoch Y M
Published: January 2020

Resequencing estA3, an allele of the methanol-soluble heat-stable enterotoxin of Escherichia coli showed that the proline triplet 19 is in fact an alanine codon; thus, estA alleles 3 and 4 were shown to be identical. Resequencing has also shown that the carboxy terminus of another allele, estA2, is not the previously inferred histidine triplet but the same tyrosine codon reported for all other estA alleles. The improperly inferred histidine codon was used in constructions to fuse estA2 to the B subunit of the heat-labile enterotoxin gene, and the fused gene products as well as three amino acid insertional mutants containing histidine-72 were not efficiently secreted. We show that the defective secretion is not due to histidine as a carboxy-terminal residue, since site-directed mutagenesis of wild-type tyrosine-72 to histidine did not influence the localization of the activity of the methanol-soluble heat-stable enterotoxin.
Evidence for phagosome-lysosome fusion in Mycobacterium leprae-infected murine Schwann cells
Authors: Steinhoff U , Golecki J R , Kazda J , Kaufmann S H
Published: January 2020

Murine Schwann cells were infected with viable armadillo-derived Mycobacterium leprae in vitro, and the lysosomal marker enzyme, acid phosphatase, was stained by the Gomori reaction. Electron microscopic analysis revealed that Schwann cells infected with M. leprae possess acid phosphatase and that lysosomes fuse with infected phagosomes.
Pore formation by the Escherichia coli hemolysin: evidence for an association-dissociation equilibrium of the pore-forming aggregates
Authors: Benz R , Schmid A , Wagner W , Goebel W
Published: January 2020

Lipid bilayer experiments were performed in the presence of hemolysin of Escherichia coli. The toxin had a rather low activity in membranes formed of pure lipids, such as phosphatidylcholine or phosphatidylserine. In membranes from asolectin, a crude lipid mixture from soybean, hemolysin was able to increase the conductance by many orders of magnitude in a steep concentration-dependent fashion, which suggested that several hemolysin molecules could be involved in the conductive unit. Furthermore, the much higher toxin activity in asolectin membranes would be consistent with the assumption that this lipid contains a receptor needed for membrane activity of the toxin. The results of single-channel records showed that the membrane activity of hemolysin is due to the formation of ion-permeable channels with a single-channel conductance of about 500 pS in 0.15 M KCl. The hemolysin channel seemed to be formed by a toxin oligomer which showed an association-dissociation reaction and had a mean lifetime of about 2 s at small transmembrane voltages. The conductance of the hemolysin channels was only moderately dependent on the salt concentration in the aqueous phase. Zero-current membrane potential experiments showed that the hemolysin channel is cation selective. The mobility sequence of the cations in the channel was similar to their mobility sequence in the aqueous phase, which was consistent with the assumption that the hemolysin channel is wide and that the interior field strength is not very high. From the single-channel conductance, a lower limit of about 1.0 nm for the effective channel diameter could be estimated.
Fibronectin increases Trypanosoma cruzi amastigote binding to and uptake by murine macrophages and human monocytes
Authors: Noisin E L , Villalta F
Published: January 2020

Trypanosoma cruzi amastigotes present receptors for human fibronectin as indicated by the saturable binding of [125I]fibronectin to this form of the parasite. Scatchard analysis indicates that the number of fibronectin receptors per amastigote was 1.3 x 10(3) with a Kd of approximately 2.3 nM. Addition of physiological concentrations of fibronectin to amastigote-macrophage cocultures significantly increased the binding of amastigotes to murine macrophages. This increase was evidenced in both the number of amastigotes bound to macrophages and the percentage of macrophages containing bound amastigotes. The uptake of amastigotes by either murine macrophages or human blood monocytes was also increased in the presence of exogenous fibronectin. The increase induced by fibronectin was blocked when amastigotes were pretreated with the RGDS tetrapeptide of the fibronectin cell attachment site. Furthermore, the ability of fibronectin to enhance amastigote binding to and uptake by macrophages was inhibited by the F(ab')2 fragment of anti-fibronectin immunoglobulin G (IgG) but not by an irrelevant anti-human IgG F(ab')2 fragment. Pretreatment of either amastigotes or macrophages with fibronectin also resulted in a significant increase in amastigote binding to and uptake by macrophages. These results suggest that fibronectin may play a role in facilitating the attachment and ingestion of T. cruzi amastigotes by macrophages and monocytes in chagasic tissue lesions.
Campylobacter pylori virulence factors in gnotobiotic piglets
Authors: Eaton K A , Morgan D R , Krakowka S
Published: January 2020

Thirty-three gnotobiotic piglets from four litters were challenged with motile and nonmotile strains of Campylobacter pylori. The most motile strain, 26695, was the most virulent, with a 100% infection rate. The least motile strain, Tx30a, was the least virulent, with an infection rate of only 17%. Strain 60190 was weakly motile and had intermediate virulence, with an infection rate of 40%. Strains recovered from piglets were more motile than the challenge strains. The challenge strains also differed in cytotoxin production. The least virulent strain, Tx30a, was nontoxigenic, while the other two strains produced high levels of cytotoxin. Thus, virulence of C. pylori for gnotobiotic piglets correlated very well with motility and not as well with cytotoxin production.