bluuebunny/crossref_metadata_2025 huggingface dataset:
Bacterial endotoxin both enhances and inhibits the toxicity of Shiga-like toxin II in rabbits and mice
Authors: Barrett T J , Potter M E , Wachsmuth I K
Published: January 2020

The ability of bacterial lipopolysaccharide (LPS) to enhance the toxicity of Shiga-like toxin II (SLT-II) was investigated in rabbits and mice. Rabbits were continuously infused with 0.5 50% lethal dose (LD50) of SLT-II per day. Rabbits that received a 30-micrograms/kg dose of LPS (0.02 LD50) on day 3 of infusion were significantly more likely to die than were rabbits receiving SLT-II only. Rabbits receiving SLT-II and a lower dose of LPS (3 micrograms/kg) did not die but lost an average 3.3% +/- 1.0% of initial body weight during the first 5 days of infusion, compared with weight gains of 4.2% +/- 0.6% and 17.1% +/- 0.9% for rabbits receiving only SLT-II or LPS, respectively. Rabbits that were pretreated with LPS 20 h before challenge with a single dose of SLT-II showed highly significant protection from both the diarrheagenic and lethal effects of SLT-II. Pretreatment of endotoxin-responsive C3H/HeN mice protected the animals from challenge with an LD50 but not an LD100 of SLT-II. LPS enhanced the lethal toxicity of SLT-II for C3H/HeN mice when it was given at 8 or 24 h but not 0 or 72 h after SLT-II challenge. LPS did not affect the lethal toxicity of SLT-II for endotoxin-resistant C3H/HeJ mice. These results suggest that LPS enhances the effects of SLT-II in vivo. Since cecal changes that increase mucosal permeability occur in response to SLT in rabbits, this synergy may be directly relevant to disease processes.
Reversion of the antichlamydial effect of tumor necrosis factor by tryptophan and antibodies to beta interferon
Authors: Shemer-Avni Y , Wallach D , Sarov I
Published: January 2020

Human recombinant tumor necrosis factor-alpha (TNF-alpha) inhibited the growth of Chlamydia trachomatis (L2/434/Bu) in HEp-2 cells. The effect was synergistic with that of gamma interferon (IFN-gamma). TNF-induced resistance to chlamydiae could be blocked with cycloheximide, suggesting that it involves the function of some induced proteins. Tryptophan degradation was enhanced in the TNF-treated cells and was much further increased when the cells were treated with both TNF and IFN-gamma at concentrations at which IFN-gamma by itself had very little effect. Antibodies to IFN-beta blocked the augmentation of tryptophan degradation by TNF and decreased but did not fully eliminate the antichlamydial effect of TNF. Increased concentration of tryptophan in the growth medium (greater than 100 micrograms/ml) resulted in reversion of the antichlamydial effect of TNF. This study suggests that the inhibition of chlamydial growth by TNF is mediated partly through an autocrine function of IFN-beta which, in synergism with TNF, enhances the activity of a tryptophan-degrading enzyme(s) and partly by some other activities of TNF which can be blocked by tryptophan.
Evidence for different pyoverdine-mediated iron uptake systems among Pseudomonas aeruginosa strains
Authors: Cornelis P , Hohnadel D , Meyer J M
Published: January 2020

Fourteen strains of Pseudomonas aeruginosa (P. aeruginosa ATCC 15692, P. aeruginosa ATCC 27853, and 12 clinical isolates) were checked for the production of pyoverdine and for pyoverdine-mediated iron uptake. Under iron restriction, two isolates produced undetectable amounts of pyoverdine, but all the other strains produced a compound with physicochemical properties identical or close to those of the pyoverdine of P. aeruginosa ATCC 15692 (strain PAO1). The pyoverdines were purified and tested for their growth-promoting activity and for their ability to facilitate 59Fe uptake in homologous experiments involving each pyoverdine and its producing strain, as well as in heterologous systems involving all the other strains. The results of both types of experiments suggested the existence of three specificity groups. This was confirmed by analysis of the amino acid composition of the pyoverdines, which differed for each group. A partially purified polyclonal antiserum raised against a major 80-kilodalton (kDa) iron-regulated outer membrane protein (IROMP) of P. aeruginosa PAO1 recognized the 80-kDa IROMPs from P. aeruginosa PAO1 and the clinical isolates belonging to the same group, whereas the IROMPs from the strains belonging to the two other groups were not detected. A second antiserum raised against the P. aeruginosa ATCC 27853 80-kDa IROMP gave similar results by reacting specifically with the 80-kDa IROMP from the strains belonging to this group. Thus, together with the already known pyoverdine from P. aeruginosa PAO1, two new types of pyoverdines produced by strains belonging to this species were characterized.
A 101-kilodalton heme-binding protein associated with congo red binding and virulence of Shigella flexneri and enteroinvasive Escherichia coli strains
Authors: Stugard C E , Daskaleros P A , Payne S M
Published: January 2020

The ability of Shigella flexneri to bind Congo red or hemin is associated with virulence. A 101-kilodalton (kDa) protein responsible for this phenotype (Crb+) in S. flexneri was identified by a tetramethylbenzidine staining procedure which detects heme-protein complexes in polyacrylamide gels. Labeling of cell-surface polypeptides with 125I revealed that the 101-kDa heme-binding protein is expressed on the cell surface. Expression of the protein was regulated by growth temperature and was found to be encoded by the large virulence plasmid of S. flexneri. Deletion mutants and a Tn5 insertion mutant which were negative for Congo red binding (Crb-) did not express the 101-kDa protein. Enteroinvasive Escherichia coli strains that were Crb+, and whose plasmids shared homology with the S. flexneri virulence plasmid, also expressed the 101-kDa protein. Expression of the protein in S. flexneri and enteroinvasive E. coli correlated with the presence of a 9.2-kilobase EcoRI fragment of these plasmids.
Recombinant human gamma interferon enhances in vitro activation of lymphocytes isolated from patients with acquired immunodeficiency syndrome
Authors: Heagy W , Strom T B , Kelley V E , Collela J , Crumpacker C , Williams J M , Shapiro H M , Laubenstein L , Finberg R
Published: January 2020

Decreased responses to antigens and lectins are a characteristic feature of peripheral blood lymphocytes isolated from patients with the acquired immunodeficiency syndrome (AIDS). The in vitro addition of recombinant gamma interferon (IFN-gamma) to cultures of peripheral blood lymphocytes obtained from patients with AIDS resulted in an augmented proliferative response [( 3H]thymidine uptake) to phytohemagglutinin (PHA) and an enrichment in CD4+ and CD8+ T lymphocytes. In AIDS cultures stimulated with PHA, IFN-gamma increased the release of T-cell growth factors and enhanced the expression of interleukin-2 receptors on activated lymphocytes. Responsiveness to PHA was augmented, albeit to a lesser extent, by IFN-gamma in cultures derived from normal donors. Proliferation to microbial antigens including herpes simplex virus, cytomegalo virus, and Candida albicans was increased by IFN-gamma in cultures established from a group of AIDS patients with Kaposi's sarcoma who had no history of opportunistic infection.
A high-molecular-weight fraction of smooth lipopolysaccharide in Klebsiella serotype O1:K20 contains a unique O-antigen epitope and determines resistance to nonspecific serum killing
Authors: McCallum K L , Schoenhals G , Laakso D , Clarke B , Whitfield C
Published: January 2020

The lipopolysaccharide (LPS) O-antigen side chains of Klebsiella serotype O1 have been studied by using mutants selected by resistance to a Klebsiella bacteriophage designated O1-A. Two classes of LPS mutants were identified. The major group (90%) synthesized rough LPS. The remaining 10% of the mutants produced a novel LPS profile that lacked the highest-molecular-weight O-substituted molecules (HMW-LPS) but still produced lower-molecular-weight O-substituted species (LMW-LPS). By using antisera raised against mutant Klebsiella strains and antiserum specific for Pasteurella haemolytica serotype 4, it was demonstrated that HMW-LPS and LMW-LPS contain shared epitopes. HMW-LPS also contained an epitope absent in LMW-LPS. This unique epitope was recognized by a monoclonal antibody (O1-52.6) and appears to be responsible for the serological cross-reaction between the O antigens of Klebsiella O1 and Escherichia coli O19. This HMW-LPS epitope was present in eight other Klebsiella O1 isolates which were examined. Electron microscopy demonstrated that HMW-LPS excluded overlying capsular polysaccharide for a distance of 25 to 40 nm. The distance was reduced to 10 to 18 nm in strains which synthesized only LMW-LPS and to zero in rough LPS strains. The HMW-LPS of Klebsiella O1 was shown to be an important virulence determinant, since this molecule was responsible for the resistance of the bacterium to nonspecific, complement-mediated serum killing.
Pseudomonas aeruginosa pili as ligands for nonopsonic phagocytosis by fibronectin-stimulated macrophages
Authors: Kelly N M , Kluftinger J L , Pasloske B L , Paranchych W , Hancock R E
Published: January 2020

Fibronectin is capable of activating macrophages for enhanced nonopsonic phagocytosis of Pseudomonas aeruginosa grown in vivo in rats or mice or in vitro on nutrient agar plates. In this study it was determined that while fibronectin was able to significantly increase phagocytosis of organisms grown in static broth, uptake of agitated bacteria could not be promoted. Agitated P. aeruginosa cultures were proven to lack surface pili expression, as assessed by electron microscopic studies. A pilus-deficient pilA::Tn501 mutant of P. aeruginosa PAO was constructed by gene replacement techniques. Phagocytosis of this mutant could not be enhanced by fibronectin regardless of growth conditions. Furthermore, 60 micrograms of exogenously added Pseudomonas pili per ml was capable of abrogating the enhanced phagocytosis of the wild-type strain observed with fibronectin-stimulated macrophages. It is concluded that Pseudomonas pili were the bacterial ligands required for attachment to fibronectin-stimulated macrophages in the initial stages of nonopsonic phagocytosis.
Human recombinant tumor necrosis factor alpha protects susceptible A/J mice against lethal Plasmodium chabaudi AS infection
Authors: Stevenson M M , Ghadirian E
Published: January 2020

The effect of intravenous treatment with human recombinant tumor necrosis factor alpha (rTNF-alpha) on infection of susceptible A/J and resistant C57BL/6 mice with Plasmodium chabaudi AS was examined. Treatment of A/J mice with 10(3) or 10(5) U of rTNF-alpha on days 0, 3, 5, 7, and 9 after intraperitoneal infection with 10(6) parasitized erythrocytes resulted in 80% survival and a significant decrease in the peak parasitemia level. Treatment of susceptible A/J hosts with 10(5) but not 10(3) U of rTNF-alpha resulted in increased survival but did not alter the peak parasitemia level following infection with 10(7) parasitized erythrocytes. Moreover, all surviving A/J mice completely eliminated the parasite by approximately 4 weeks and were fully protected against a secondary infection. Except at a dose of 5 x 10(5) U of rTNF-alpha, which resulted in 100% mortality of infected animals, rTNF-alpha did not alter the course or outcome of infection with P. chabaudi AS in resistant C57BL/6 mice.
Impaired antipneumococcal activity of bronchoalveolar lining material of neonatal rats
Authors: Coonrod J D , Jarrells M C
Published: January 2020

Pulmonary clearance of inhaled pneumococci is markedly impaired in neonatal rats compared with that in adult rats. To determine whether this impairment is due to a deficiency of extracellular bactericidal factors, the antipneumococcal activity of free fatty acids (FFA) in lung surfactant and the levels of lysozyme and transferrin in lavage fluids were quantified. Surfactant from adult rats averaged 68 U of antipneumococcal activity per g (dry weight) of lung, compared with less than 0.25 U for rats less than 1 week old (P less than 0.001). The kinds of FFA in surfactant of neonatal and adult rats were essentially identical, and the antipneumococcal activity of highly purified FFA from surfactant of neonatal and adult rats was also the same. However, the quantity of FFA in surfactant varied significantly with age, and rats less than 3 weeks old had much lower levels of surfactant FFA than did adults (P less than 0.001). In addition, lavage fluids from neonatal rats inhibited the antipneumococcal activity of surfactant FFA more than lavage fluids from adults did (P less than 0.02). This inhibitory activity did not appear to be due to protein binding. Lavage fluids from neonates showed an age-related deficiency of lysozyme (P less than 0.001), but lysozyme appeared to play no role in pneumococcal killing by the surfactant fraction of lavage fluids in vitro. Transferrin levels in lavage fluids were similar for neonates and adults. It was concluded that lung surfactant from neonatal rats was deficient in antipneumococcal activity, due mostly to low levels of FFA and to a lesser degree to increased levels of inhibitor(s) in lavage fluids.
Analysis of mannans of two relatively avirulent mutant strains of Candida albicans
Authors: Saxena A , Hammer C F , Cihlar R L
Published: January 2020

We previously reported the isolation of two cerulenin-resistant mutant strains of Candida albicans 4918 that differ in adherence properties and are less virulent than the parental strain. In addition, biochemical characterization demonstrated significant differences in both protein and polysaccharide composition of cell wall material between the mutant and wild-type strains. These observations prompted studies concerning the chemical structure of mannans in these strains. After extraction and subsequent purification by ion-exchange chromatography, mannan fractions were subjected to either mild acid hydrolysis, alkali hydrolysis, or acetylation followed by acetolysis. Acid- and alkali-modified mannans were studied by proton magnetic resonance spectroscopy, and released products were analyzed by high-performance liquid chromatography on an Aminex HPX-42A column. The results demonstrated quantitative and qualitative differences between mannooligosaccharides of the wild-type and mutant strains in the identity of released oligosaccharides as well as in linkage of the oligosaccharides to the protein backbone.
Structural analysis of lipopolysaccharides from Eikenella corrodens by use of murine monoclonal antibodies
Authors: Kato T , Takazoe I , Okuda K
Published: January 2020

The structure of lipopolysaccharides (LPSs) of Eikenella corrodens was analyzed with prepared murine monoclonal antibodies. A common core epitope was found in three of seven LPS preparations from E. corrodens strains and Fusobacterium nucleatum ATCC 25586. Four E. corrodens LPSs were found to possess an O-side-chain epitope which cross-reacted with LPSs from Fusobacterium necrophorum ATCC 25286 and Capnocytophaga ochracea M-12. Lipid A of E. corrodens LPS shared an epitope common among LPSs from various gram-negative rods.
Identification of stage-specific antigens of Toxoplasma gondii
Authors: Kasper L H
Published: January 2020

An immunologic evaluation of the surface antigens of the three major life-cycle stages of Toxoplasma gondii was performed. Mouse antisera were raised against these stages, which included the oocyst-sporozoite (feline-excreted stage), bradyzoite (chronic tissue cyst stage), and tachyzoite (invasive stage). The antisera were used in an enzyme-linked immunosorbent assay and Western blot (immunoblot) analysis to demonstrate the presence of stage-specific antigens. These antigens were of various molecular weights and were specific to each stage investigated. Cross-reaction studies showed that the mouse antisera recognized commonly shared antigens to at least two of the three stages. A panel of monoclonal antibodies identified specific immune epitopes unique to each of the stages investigated. These studies further support the hypothesis that stage-specific antigens are present in T. gondii.
Cariogenicity of a lactate dehydrogenase-deficient mutant of Streptococcus mutans serotype c in gnotobiotic rats
Authors: Fitzgerald R J , Adams B O , Sandham H J , Abhyankar S
Published: January 2020

A lactate dehydrogenase-deficient (Ldh-) mutant of a human isolate of Streptococcus mutans serotype c was tested in a gnotobiotic rat caries model. Compared with the wild-type Ldh-positive (Ldh+) strains, it was significantly (alpha less than or equal to 0.005) less cariogenic in experiments with two different sublines of Sprague-Dawley rats. The Ldh- mutant strain 044 colonized the oral cavity of the test animals to the same extent as its parent strain 041, although its initial implantation was slightly but not significantly (P greater than or equal to 0.2) less. Multiple oral or fecal samples plated on 2,3,5-triphenyltetrazolium indicator medium revealed no evidence of back mutation from Ldh- to Ldh+ in vivo. Both Ldh+ strain 041 and Ldh- strain 044 demonstrated bacteriocinlike activity in vitro against a number of human strains of mutans streptococci representing serotype a (S. cricetus) and serotypes c and e (S. mutans). Serotypes b (S. rattus) and f (S. mutans) and strains of S. mitior, S. sanguis, and S. salivarius were not inhibited. Thus, Ldh mutant strain 044 possesses a number of desirable traits that suggest it should be investigated further as a possible effector strain for replacement therapy of dental caries. These traits include its stability and low cariogenicity in the sensitive gnotobiotic rat caries model, its bacteriocinlike activity against certain other cariogenic S. mutans (but not against more inocuous indigenous oral streptococci), and the fact that it is a member of the most prevalent human serotype of cariogenic streptococci.
Association of Campylobacter pylori with induced expression of class II transplantation antigens on gastric epithelial cells
Authors: Engstrand L , Scheynius A , Påhlson C , Grimelius L , Schwan A , Gustavsson S
Published: January 2020

Campylobacter pylori was identified with immunoperoxidase staining and a mouse monoclonal antibody directed against C. pylori in gastric biopsy specimens from 24 patients with gastritis. C. pylori was not found in gastric biopsy specimens from six subjects with histologically normal mucosa. The monoclonal antibody, which was reactive with a surface protein of approximately 20 kilodaltons, was found to be specific for C. pylori, and the immunoperoxidase staining proved to be more sensitive and rapid than culture in detecting the organism. In the tissue specimens where C. pylori was detected with the monoclonal antibody, there was a strong expression of class II transplantation antigens on the epithelial cells and an increased number of T lymphocytes. These findings indicate that C. pylori may initiate local immune responses.
Inhibition by retinoic acid of multiplication of virulent tubercle bacilli in cultured human macrophages
Authors: Crowle A J , Ross E J
Published: January 2020

The immunologically active vitamin retinoic acid (RA) was tested for the ability to increase the resistance of cultured human macrophages (MP) to experimental infection with virulent Mycobacterium tuberculosis Erdman (tubercle bacilli [TB]). It was added to MP in various concentrations and addition regimens. Protection against TB was measured by counting live TB (CFU) in lysates of samples of MP taken at 0, 4, and 7 days after MP infection. RA was protective when added after infection at the pharmacologic concentration of 10(-5) M and when added before infection at the physiologic concentration of 10(-7) M. The protection lengthened intracellular generation times for TB, occasionally caused bacteriostasis, and regularly kept CFU counts at 7 days (end of the period of infection) 1 to 2 log10 CFU below control values. Significant protection was seen in a series of 16 experiments with MP from seven different donors, but the degree of protection varied considerably. The protection depended partly on and was inversely proportional to concentrations of a serum substitute or autologous serum used as a supplement in the RPMI 1640 MP culture medium. It was strongest at concentrations of serum below 1%. RA at concentrations used in the MP cultures did not inhibit TB in the absence of MP. These results suggest that RA (vitamin A), like vitamin D, may have some immunoprotective role against human tuberculosis, as historically intimated by the regular use of vitamin A- and D-rich cod liver oil for the treatment of tuberculosis before the introduction of modern chemotherapy.
Immunoglobulin M-dependent classical complement pathway activation in killing of Pentatrichomonas hominis
Authors: Shaio M F , Chen J G
Published: January 2020

Complement pathway activity in the killing of Pentatrichomonas hominis was investigated in this study. At 10(5) organisms per ml, P. hominis was completely killed by the presence of 1% normal human serum. In contrast, no killing effect on P. hominis was observed when specific antibodies were absorbed or when the complement was destroyed. Moreover, Mg2+-ethylene glycol-bis-(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid-treated serum had no killing effect on P. hominis, while serum heated at 50 degrees C or treated with zymosan killed P. hominis as well as did normal human serum. Further study using gel filtration (Sephacryl S-300) and affinity chromatography (protein A) revealed that immunoglobulin M (IgM; 20 micrograms/ml) alone was responsible for the complement activation in the killing of P. hominis, but both IgA (24 micrograms/ml) and IgG (180 micrograms/ml) had no effect on complement-mediated lysis. On the other hand, IgG at 1,260 micrograms/ml completely inhibited complement-mediated killing by IgM, suggesting that a blocking factor is present in IgG. The results of this study indicate that a mechanism of IgM-dependent classical complement pathway activation contributes to the killing effect of normal human serum on P. hominis.
Binding of cholera toxin to pig intestinal mucosa glycosphingolipids: relationship with the ABO blood group system
Authors: Bennun F R , Roth G A , Monferran C G , Cumar F A
Published: January 2020

A search for compounds from intestinal mucosa of pigs carrying and not carrying blood group A-active substances (A+ and A- pigs, respectively) capable of binding cholera toxin (CT) was performed. Glycolipid extracts from a pool of pig intestinal mucosa resolved in thin-layer chromatography (TLC) revealed the presence of six to eight compounds capable of binding 125I-CT, two of them running as the ganglioside standards GM1 and GD1b. When intestinal mucosa glycolipids from single pigs were assayed by TLC for CT-binding capacity, two different patterns of labeling were observed. The main difference was at the level of compounds running below GD1b. The A+ pigs but not the A- pigs showed CT binding at this level. The major CT-binding compound detected only in A+ pigs was purified and some properties were determined. After TLC developed with different solvent systems, the purified compound bound CT and also immunoreacted with anti-A and anti-AB antisera but not with anti-B antiserum. The compound was also able to inhibit the hemagglutination of human A erythrocytes caused by anti-A antiserum, but inhibition was not observed with the B-anti-B or O (H)-Ulex europaeus lectin systems. A partial chemical characterization indicated that the active compound is a neutral glycosphingolipid containing glucose, fucose, galactose, and hexosamine. The existence of a blood group-active substance(s) able to interact with CT may help to explain the relationship between ABO blood groups and the diarrheal disease caused by infection with Vibrio cholerae.
Resistance to infection in murine beta-thalassemia
Authors: Ampel N M , Van Wyck D B , Aguirre M L , Willis D G , Popp R A
Published: January 2020

Clinical evidence suggests that individuals with chronic iron overload may be at increased risk of bacterial infection. We studied this question by using a unique model in which mice homozygous for a deletion in the gene encoding for the beta-major globin develop moderate anemia, splenomegaly, and tissue iron overload, a syndrome similar to beta-thalassemia in humans. Mice heterozygous for the gene deletion were phenotypically normal. Homozygous mice were significantly more susceptible to infection with Listeria monocytogenes than were heterozygous mice (P less than 0.01). This increased susceptibility was associated with a greater number of organisms in the liver and spleen than was found in heterozygous mice (P less than 0.05). However, histologic studies demonstrated similar inflammatory responses within these organs in homozygous and heterozygous mice. The increased susceptibility of homozygous mice to infection with L. monocytogenes was not seen when homozygotes were immunized with a low dose of L. monocytogenes. Although the results were not as striking as with L. monocytogenes, homozygous mice were also found to be more susceptible to infection with Salmonella typhimurium than were heterozygous mice (P less than 0.05). Splenic mononuclear cells from homozygous mice demonstrated less responsiveness in vitro to the mitogens concanavalin A and phytohemagglutinin than did those from heterozygotes (P less than 0.05). These data suggest that there is a generalized defect in innate immunity in homozygous mice which makes them more susceptible to infection by L. monocytogenes and S. typhimurium. The site of this immunological defect is not known but is most likely in the mononuclear phagocyte and may be due to tissue iron overload.
Development and characterization of a monoclonal antibody against the tube precipitin antigen of Coccidioides immitis
Authors: Dolan M J , Cox R A , Williams V , Woolley S
Published: January 2020

Primary infection with Coccidioides immitis is commonly accompanied by the production of an immunoglobulin M precipitin antibody which is detected by the tube precipitin (TP) assay or by the immunodiffusion assay for TP antibody (IDTP assay). In the present investigation, spleen cells from spherulin-immunized BALB/c mice were fused with SP2/O Ag14 myeloma cells, and the resulting hybridomas were screened for antibody to the IDTP antigen by using an enzyme-linked immunosorbent assay. Positive hybridomas were cloned by limiting dilution and injected into pristane-primed mice for ascites production. Characterization of antibody reactivity was accomplished with the IDTP assay, two-dimensional immunoelectrophoresis, and immunoblotting. An immunoglobulin G1 monoclonal antibody which reacts with the IDTP antigen of C. immitis is described. The epitope that is recognized by the monoclonal antibody is also present, but to a lesser extent, on a second coccidioidal antigen which has been designated antigen 2. The monoclonal antibody was not reactive in immunoblots of histoplasmin or blastomycin, indicating that the epitope recognized by this antibody may be specific for C. immitis.
Nucleotide and deduced amino acid sequences for the four variable domains of the major outer membrane proteins of the 15 Chlamydia trachomatis serovars
Authors: Yuan Y , Zhang Y X , Watkins N G , Caldwell H D
Published: January 2020

The amino acid sequences of major outer membrane proteins (MOMPs) from Chlamydia trachomatis serovars A, B, C, L1, and L2 are predominantly conserved but have four variable domains (VDs) in which major neutralizing and serotyping antigenic determinants are located. Because these MOMP VDs are primarily responsible for antigenic differences between serovars and are associated with important immunological and biological properties, we undertook studies focused on defining these sequences within the MOMPs of all 15 C. trachomatis serovars. We used oligonucleotide primer extension sequencing of MOMP mRNA to determine the nucleotide and deduced amino acid sequences of the four MOMP VDs of the 15 C. trachomatis serovars. Comparative amino acid sequence homologies of all four domains separated the serovars into three groups: group 1, serovars B, Ba, D, E, L1, and L2; group 2, serovars G and F; and group 3, serovars A, C, H, I, J, K, and L3. Hydrophilicity and charge values for each domain were determined. The MOMP VDs of given serovars with the greatest total hydrophilicity and charge values were found to be the location of antigenic determinants recognized by MOMP-specific monoclonal antibodies. These findings should be useful for predicting MOMP antigenic determinants and testing the antigenic properties of these VDs by using synthetic peptides corresponding to each MOMP VD. The potential usefulness of the VD sequence information is discussed in relation to the development of defined synthetic peptides and oligonucleotides that may be used to develop new serological and diagnostic assays for C. trachomatis infections.
Long-term effects of gamma interferon on chlamydia-infected host cells: microbicidal activity follows microbistasis
Authors: Byrne G I , Carlin J M , Merkert T P , Arter D L
Published: January 2020

When human monocyte-derived macrophages or a human uroepithelial cell line (T24 cells) was incubated in the presence of gamma interferon (IFN-gamma) for 24 to 48 h and then infected with Chlamydia psittaci, host cells became activated to restrict intracellular C. psittaci growth. A reversal of this inhibition was observed when infected cells were supplemented with excess exogenous tryptophan at the time of infection or at 1 to 3 days after infection. When IFN-gamma-treated, infected cells were incubated for more extended periods of time before the addition of exogenous tryptophan, no recovery of viable chlamydiae was observed. Neither replacement of the IFN-gamma-containing medium with complete medium supplemented with excess tryptophan nor the addition of excess concentrations of all 20 amino acids with and without essential vitamins contributed to the reversal of IFN-gamma-mediated inhibition of chlamydial growth beyond the time when reversal occurred after the addition of exogenous tryptophan alone. These data provide evidence which indicates that although IFN-gamma treatment of host cells initially results in a microbistatic inhibition of intracellular chlamydial development, longer incubations result in microbicidal activity that is irreversible by modulation of essential nutrient levels.
Variable expression of a yeast-phase-specific gene in Histoplasma capsulatum strains differing in thermotolerance and virulence
Authors: Keath E J , Painter A A , Kobayashi G S , Medoff G
Published: January 2020

By means of differential hybridization techniques, several yeast-phase-specific DNA sequences were identified in the dimorphic pathogenic fungus Histoplasma capsulatum. A 1.85-kilobase (kb) HindIII fragment from one genomic clone, yps-3, hybridized to at least three distinct yeast poly(A)+ RNAs of 1.3, 1.05, and 0.95 kb from the virulent strain G217B. These mRNAs were not detected in mycelia. When mycelia from G217B were induced to become yeast by transfer from 25 to 37 degrees C, a process requiring approximately 9 days, expression of yps-3 was detected within 24 h, although not in the initial 2 h following the temperature shift. In contrast, a low-virulence strain (Downs) which completes the transition in approximately 2 weeks failed to express the yps-3 gene during phase transitions. A third isolate, G186B, intermediate in its virulence properties and in the time required for the transition (11 days), expressed a single 1.25-kb mRNA but only at low levels in the yeast phase and only after 3 days following the 25-to-37 degrees C temperature shift. Although yps-3 expression does not appear to be essential for the transformation to the yeast phase, it may facilitate the early adaptive processes which permit the mycelium-to-yeast transition and survival of the yeast phase of H. capsulatum at elevated host temperatures. The phase-specific yps-3 nuclear gene is carried on highly polymorphic restriction fragments in all three strains, suggesting that this probe may provide a sensitive diagnostic tool for the classification of H. capsulatum isolates.
Fungus dose-dependent primary pulmonary aspergillosis in immunosuppressed mice
Authors: Dixon D M , Polak A , Walsh T J
Published: January 2020

We report on a model of primary pulmonary aspergillosis occurring after intranasal instillation of concentrated suspensions of conidia of Aspergillus fumigatus in immunocompromised mice. Unconcentrated suspensions of inoculum contained ca. 2 x 10(7) conidia per ml (1x). These suspensions were concentrated by centrifugation, adjusted to give ca. 2 x 10(8) (10x) or 2 x 10(9) (100x) conidia per ml, and delivered in 30-microliters droplets to the nares of anesthetized mice. Mice were untreated or injected with cortisone acetate (CA) or cyclophosphamide (CY) in various dosage regimens. It was not possible to obtain mortality of more than 50% with sublethal immunosuppressive treatment and 1x fungus. In contrast, mortality followed a fungus dose response in mice receiving sublethal immunosuppression with either CA or CY. Mortality rates of up to 100% were obtained with 100x fungus and a single dose of CY (200 mg/kg) or CA (250 mg/kg) or three alternate doses (125 mg/kg per day) of CA prior to infection. This model is applicable to the study of acute, fatal primary pulmonary aspergillosis and chemotherapy trials.
Cytokine activation of murine macrophages for in vitro killing of Entamoeba histolytica trophozoites
Authors: Denis M , Chadee K
Published: January 2020

Macrophage-mediated effector mechanisms against the protozoan parasite Entamoeba histolytica were studied. Unstimulated macrophages were inefficient at killing E. histolytica trophozoites in vitro and were killed by the trophozoites. Conversely, immature cells of the mononuclear phagocyte lineage (promonocytes) were shown to display a strong spontaneous amebicidal activity. The acquisition of macrophage amebicidal activity following cytokine treatment was investigated. Gamma interferon, tumor necrosis factor alpha, and macrophage colony-stimulating factor 1, or combinations thereof, were shown to endow murine bone marrow-derived macrophages with significant amebicidal activity. Low doses of gamma interferon and tumor necrosis factor alpha and of gamma interferon and colony-stimulating factor 1 were shown to act synergistically in this phenomenon. This enhancement of amebicidal activity was shown to operate on bone marrow-derived macrophages, elicited peritoneal macrophages, and, to a much lesser extent, spleen macrophages. Although acquisition of amebicidal activity was associated with a strong respiratory burst, the addition of oxygen-free radical scavengers showed that the killing activity was approximately 45% H2O2 dependent. In addition, amebicidal activity by macrophages was shown to be contact dependent and was inhibited by 61% with the protease inhibitor tosyl lysyl chloromethyl ketone. Our results indicate that immunologic production of gamma interferon, tumor necrosis factor alpha, and colony-stimulating factor 1 could be important in the activation of macrophages for host defense against amebiasis and that promonocytes are strong effector cells against virulent amebae.
Immune response to dimeric subunits of the pertussis toxin B oligomer
Authors: Hausman S Z , Burns D L , Sickler V C , Manclark C R
Published: January 2020

Immunization of mice with the dimeric subunits of pertussis toxin (S2-S4 and S3-S4) induced an antibody response detectable by enzyme-linked immunosorbent assay and immunoblot techniques. These antibodies were able to neutralize the ability of pertussis toxin to alter the morphology of Chinese hamster ovary cells. Mice immunized with the dimers were also protected against the leukocytosis-promoting effects of toxin. Based on these data, the dimers of pertussis toxin may be considered for further study as potential vaccine candidates.
In vivo selection of populations of Plasmodium chabaudi chabaudi AS resistant to a monoclonal antibody that reacts with the precursor to the major merozoite surface antigen
Authors: Wood J C , Sales de Aguiar J C , Jarra W , Ogun S A , Snounou G , Brown K N
Published: January 2020

Mice bearing a hybridoma secreting a monoclonal antibody (MAb), MAb-3, which significantly delays the onset of a Plasmodium chabaudi chabaudi AS, but not P. chabaudi chabaudi CB, challenge parasitemia in a passive transfer assay and which is specific for the precursor to the major merozoite surface antigen (PMMSA) of P. chabaudi chabaudi AS, were challenged intravenously with 10(3) P. chabaudi chabaudi AS-parasitized erythrocytes. The resultant parasitemia was very similar to that in normal mice except that initially the parasitemia was sometimes slightly delayed. Parasites derived from cryopreserved stabilates isolated from MAb-3 hybridoma mice with an unmodified parasitemia, or with a delayed parasitemia, were found to have lost their susceptibility to MAb-3 in the passive transfer assay. A number of anti-PMMSA MAb were used to immunoprecipitate lysates of parasite populations isolated directly from hybridoma-bearing mice. In some instances and with certain of the MAb, immunoprecipitation patterns were modified, but other isolates were not detectably different when compared with unselected P. chabaudi chabaudi AS parasites. Using a panel of MAb reacting with the PMMSA of P. chabaudi chabaudi AS, immunoprecipitation patterns of parasites derived from cryopreserved stabilates isolated from hybridoma-bearing mice were determined at 2-h intervals through the appropriate part of the parasite maturation cycle. In these derived populations, resistance to MAb-3 was not associated with a change in the immunoprecipitation reaction with the MAb used. These results are discussed in the context of current knowledge of genotypic and phenotypic antigenic diversity of malaria parasites and other protozoa.
Selective suppressive effects of Trypanosoma cruzi on activated human lymphocytes
Authors: Beltz L A , Kierszenbaum F , Sztein M B
Published: January 2020

The acute phase of Chagas' disease is accompanied by immunosuppression. To explore the underlying mechanism(s), we used an in vitro culture system in which the capacities of activated human peripheral blood mononuclear cells to express interleukin-2 receptors (IL-2R) and proliferate are markedly inhibited in the presence of Trypanosoma cruzi, the etiologic agent. The present work was designed to define the earliest time at which T. cruzi-induced suppression is manifested in terms of IL-2R expression on the cell surface and establish whether expression of other lymphocyte activation markers is also suppressed by the parasite. We found that expression of IL-2R by human peripheral blood mononuclear cells cocultured with T. cruzi and stimulated with either phytohemagglutinin or anti-CD3 (a monoclonal antibody specific for an epitope of the T cell receptor complex T3-Ti) was significantly suppressed as early as 12 h after culture initiation. Both the percentage of IL-2R+ cells and the surface density of IL-2R, measured by flow cytometry, were affected. However, expression of EA1, a human lymphocyte activation antigen known to be expressed 4 to 6 h after stimulation, was not altered by T. cruzi whether phytohemagglutinin or anti-CD3 was used. On the other hand, expression of transferrin receptors (TfR), which first occurs between 20 and 24 h after lymphocyte activation, was markedly suppressed by T. cruzi. This effect was denoted by significant reductions in both the percentage of TfR+ cells and the cell surface density of TfR whether phytohemagglutinin or anti-CD3 was used as the mitogen and was observed at all test times, i.e., at 24, 48, 72, and 96 h. Because expression of IL-2R and TfR is required for lymphoproliferation but that of the EA1 lymphocyte activation marker is apparently not, these results are consistent with the possibility that T. cruzi, at a relatively early stage during lymphocyte activation, selectively affects certain key events on which clonal expansion is dependent. Inhibition of IL-2R and TfR expression by the parasite might play a role in causing the suppressive effects associated with acute Chagas' disease.
Interaction of drug resistance plasmids and bacteriophages with diarrheagenic strains of Escherichia coli
Authors: Bradley D E
Published: January 2020

Seven transfer-derepressed plasmids from different incompatibility groups in Escherichia coli K-12 were tested for their ability to enter 43 strains of diarrheagenic E. coli (mostly enteropathogenic E. coli clinical isolates) representing 12 serogroups and including rough and semirough mutants (characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis). Strains in some serogroups were more competent as recipients of plasmids than were those in others. Five test plasmids in an E. coli K-12 (rough) donor transferred significantly less efficiently to two smooth strains than to their rough or semirough isogenic derivatives. When the same smooth and rough strains were used as donors, the plasmids transferred to E. coli K-12 equally well. These results suggested that the O-antigenic lipopolysaccharide side chains of diarrheagenic E. coli isolates shielded the outer membrane receptors for conjugative pili, thus preventing plasmid entry. The different receptors for eight bacteriophages were also covered by O side chains. In addition, a limited survey of clinical isolates for drug resistance markers and resident plasmids was carried out.
Roles of the Fc receptor and respiratory burst in killing of Rickettsia prowazekii by macrophagelike cell lines
Authors: Keysary A , McCaul T F , Winkler H H
Published: January 2020

It is known that the virulent strain of Rickettsia prowazekii grows in macrophagelike cell lines, but if the rickettsiae are treated with antirickettsial serum before infection, the intracellular rickettsiae fail to grow and are destroyed. The uptake of rickettsiae by macrophagelike cell lines was increased by treatment of the rickettsiae with immune serum and with purified immunoglobulin G (IgG) from this serum but not by treatment with the F(ab')2 fragment derived from this IgG. This suggested that the normal rickettsial pathway of entry could be augmented by the Fc receptor-mediated pathway. However, rickettsiae treated with these F(ab')2 fragments which contained no Fc region were destroyed as effectively as those treated with immune serum or IgG. Internalization of R. prowazekii (whether virulent, avirulent, treated, or untreated) did not lead to an increased release of CO2 from [1-14C]glucose, an increase that would have been indicative of a respiratory burst. Furthermore, a mutant macrophagelike cell line, incapable of a respiratory burst, was able to destroy rickettsiae treated with immune serum as effectively as did the parental cell line. Electron micrographs of macrophagelike cells which had been incubated with either antirickettsial IgG or with F(ab')2 fragments derived from this IgG both demonstrated marked deterioration of the rickettsiae, which were primarily within vacuoles but occasionally free in the cytoplasm. In contrast, untreated rickettsiae displayed morphologically normal rickettsiae which were mostly in the cytoplasm but occasionally in the intact and damaged vacuoles. These results indicated that (i) a respiratory burst was not a significant part of the mechanism used by macrophagelike cells to destroy R. prowazekii treated with immune serum, (ii) the destruction of the rickettsiae by the macrophage was not dependent on a diversion to the Fc receptor-mediated pathway of entry, and (iii) the locus of damage to the rickettsiae was most likely the phagolysosome of the macrophagelike cell line.
Comparison of the abilities of different protein sources of iron to enhance Neisseria meningitidis infection in mice
Authors: Schryvers A B , Gonzalez G C
Published: January 2020

This study was done primarily to determine whether the previously observed specificity of the meningococcal transferrin and lactoferrin receptors for human proteins was maintained in vivo during meningococcal infection in mice. Preliminary experiments evaluating the choice of host strain, the age and sex of mice, and the growth conditions of the meningococci indicated that 45-day-old female Swiss Webster mice challenged with meningococci grown on low-pH, low-iron Mueller-Hinton agar plates were appropriate for this study. The comparison of transferrins and lactoferrins from different species demonstrated that only the human forms of these proteins were utilized by meningococci; there was significantly greater mortality among mice treated with iron-saturated human transferrin or lactoferrin (93 and 100%, respectively) than among those not treated or treated with iron-saturated bovine transferrin or bovine lactoferrin (0%). Provision of exogenous hemoglobin also resulted in increased mortality, although not as great as that observed with amounts of transferrin with equivalent iron content, which parallels the more effective utilization of transferrin and lactoferrin in in vitro growth experiments. In addition, unlike with transferrin and lactoferrin, there was no difference in utilization of human and bovine hemoglobin in vitro or in vivo.
Identification of additional virulence determinants on the pYV plasmid of Yersinia enterocolitica W227
Authors: Mulder B , Michiels T , Simonet M , Sory M P , Cornelis G
Published: January 2020

This paper describes the mutagenesis of the pYV plasmid from Yersinia enterocolitica W22703 (serotype O:9) with Tn2507, a new element generating operon fusions. Analysis of the mutants allowed the identification of an additional Yop protein called Yop20 and the mapping of yop20, yop44, yop48, and lcrV, the gene encoding the V antigen. The last gene appeared to be part of an operon that also may contain yop37 and yop44. At 37 degrees C, mutants affected in this operon grew poorly, irrespective of the presence of Ca2+, or they even died in the presence of Ca2+. This operon is thus involved in the regulation by Ca2+, and we called it car, for Ca2+ regulation. It is presumably the Y. enterocolitica counterpart of the lcrGVH operon of Yersinia pestis. Transcription of yop20 and of the car operon was strongly regulated by temperature and only slightly by calcium. Hence, these genes behaved like the other genes of the yop regulon. Mutants affected in yop20 or in yop48 were markedly less virulent for the desferrioxamine-treated mouse than was the parental strain. Yop20 and Yop48 thus probably are Yersinia virulence factors.