Susceptibility of lipopolysaccharide mutants to the bactericidal action of human neutrophil lysosomal fractions

The Two Faces of Bacterial Membrane Vesicles: Pathophysiological Roles and Therapeutic Opportunities

Bacterial membrane vesicles (MVs) are nanosized lipid particles secreted by lysis or blebbing mechanisms from Gram-negative and -positive bacteria. It is becoming increasingly evident that MVs can promote antimicrobial resistance but also provide versatile opportunities for therapeutic exploitation. As non-living facsimiles of parent bacteria, MVs can carry multiple bioactive molecules such as proteins, lipids, nucleic acids, and metabolites, which enable them to participate in intra- and interspecific communication. Although energetically costly, the release of MVs seems beneficial for bacterial fitness, especially for pathogens. In this review, we briefly discuss the current understanding of diverse MV biogenesis routes affecting MV cargo. We comprehensively highlight the physiological functions of MVs derived from human pathogens covering in vivo adaptation, colonization fitness, and effector delivery. Emphasis is given to recent findings suggesting a vicious cycle of MV biogenesis, pathophysiological function, and antibiotic therapy. We also summarize potential therapeutical applications, such as immunotherapy, vaccination, targeted delivery, and antimicrobial potency, including their experimental validation. This comparative overview identifies common and unique strategies for MV modification used along diverse applications. Thus, the review summarizes timely aspects of MV biology in a so far unprecedented combination ranging from beneficial function for bacterial pathogen survival to future medical applications.

Ameliorative effect of alpha lipoic acid and royal jelly against the side effects of cyclophosphamide in liver of albino rats

Background

Cyclophosphamide (CP) is a cytotoxic anticancer drug used for the treatment of neoplastic diseases. The present study aimed to examine biochemical, histological, and ultrastructural effects of CP on rat liver and determine the hepatoprotective effects of alpha-lipoic acid (LA) or royal jelly (RJ) against CP.

Results

The present study revealed that CP-induced significant increase in hepatic marker enzymes (ALT and AST), and elevation in malonaldehyde (MDA) was concomitant with a significant decrease of superoxide dismutase (SOD). It caused histopathological changes in the liver of rat including vacuolation, infiltration, degeneration, and necrosis. Ultrastructurally, the hepatocytes appeared degenerated with multiple small- and medium-sized lipid droplets in the cytoplasm. Kupffer cell showed a shrunken nucleus. Administration of LA and RJ resulted in an obvious improvement in the altered level of ALT, AST, MDA, and SOD activities when compared with the CP-treated group in addition to marked amelioration in histopathology and ultrastructure of the liver.

Conclusions

LA is markedly effective than RJ in protecting rats against CP-induced biochemical, histopathological, and ultrastructural changes. This protection may be due to its antioxidant properties and scavenging abilities against active free radicals.

Vacuolar ATPase in phago(lyso)some biology

Many eukaryotic cells ingest extracellular particles in a process termed phagocytosis which entails the generation of a new intracellular compartment, the phagosome. Phagosomes change their composition over time and this maturation process culminates in their fusion with acidic, hydrolase-rich lysosomes. During the maturation process, degradation and, when applicable, killing of the cargo may ensue. Many of the events that are pathologically relevant depend on strong acidification of phagosomes by the 'vacuolar' ATPase (V-ATPase). This protein complex acidifies the lumen of some intracellular compartments at the expense of ATP hydrolysis. We discuss here the roles and importance of V-ATPase in intracellular trafficking, its distribution, inhibition and activities, its role in the defense against microorganisms and the counteractivities of pathogens.

PH-induced collapse of the extracellular loops closes Escherichia coli maltoporin and allows the study of asymmetric sugar binding

LamB (maltoporin) is essential for the uptake of maltose and malto-oligosaccharides across the outer membrane of Escherichia coli. Purified LamB was reconstituted in artificial lipid bilayer membranes forming channels in the permanently open configuration at neutral pH. Almost complete channel closure was observed when the pH on both sides of the membrane was lowered to pH 4. When LamB was added to only one side of the membrane, the cis-side, and the pH was lowered at either side of the membrane, the cis- or the trans-side, the response to pH was asymmetric, suggesting preferential orientation of maltoporin channels and pH- dependent closure of only one side of the channel. In experiments with LamB mutants in which major external loops L4, L6, and/or L9 were deleted, we identified the surface-exposed loops L4 and L6 as the cause of pH-mediated closure. The pH dependence of the LamB channel is consistent with the assumption that it inserts in a preferential orientation into the lipid bilayer. About 70-80% of the reconstituted channels are oriented with the extracellular entrance toward the side to which the protein was added (the cis-side) and with the periplasmic opening on the opposite side (the trans-side). The possibility of closing the channels, which are oriented in the reverse direction by low pH at the trans-side, allowed the deduction of channel asymmetry with respect to carbohydrate binding kinetics. Whereas maltose binding was found to be almost symmetric with respect to the channel orientation, the sucrose and trehalose binding to LamB was asymmetric. The results are discussed in respect to possible physiological function of the pH-dependent closure of maltoporin.

A chelating agent possessing cytotoxicity and antimicrobial activity: 7-morpholinomethyl-8-hydroxyquinoline

7-Morpholinomethyl-8-hydroxyquinoline (MO-8HQ), which like 8-hydroxyquinoline (8HQ) readily forms a chelate, was synthesized and found to possess cytotoxicity and antimicrobial activity. Both 8HQ and MO-8HQ were cytotoxic to human carcinoma cell lines at micromolar concentrations. MO-8HQ also inhibited DNA synthesis of tumor cells at micromolar concentrations, suggesting that MO-8HQ might chelate metals necessary for the enzymatic catalysis of DNA biosynthesis. MO-8HQ was more active against gram positive bacteria than gram negative bacteria and its potency correlated with iron chelation. An "unsaturated" chelate with a MO-8HQ to Fe ratio of 2:1 exhibited greater antibacterial activity than MO-8HQ alone. Among the organisms tested, Micrococcus flavus was most susceptible with a MIC of 3.9 microg/ml. MO-8HQ also exhibited anti-fungal activity at 7-15 microg/ml. MO-8HQ:Fe chelate markedly increased the susceptibility of Escherichia coli to deoxycholate. Addition of Ca2+ or Mg2+ reversed the sensitivity of bacteria to deoxycholate as well as to rifampicin. It is suggested that MO-8HQ exerts its biological activity as a membrane-active agent through metal ion chelation.

Origins and development of peptide antibiotic research. From extracts to abstracts to contracts

That cationic proteins might be factors on the antimicrobial defenses of mammalian hosts and are apparently associated with the cytoplasmic granules of phagocytic leukocytes first became evident on the late nineteenth century. It remained, however, for development of sophisticated microanalytic techniques in microbiology, cell biology and protein biochemistry to place these hypotheses in the realm of established theory. This article is a brief summary of significant steps in the development of this theory. It also attempts to outline the firmly established scope and significance of these developments both for the theory of immunity to infection in the different phyla and for the now global quest for new antibiotics.

The large, free-living amoebae: wonderful cells for biological studies

The large, free-living amoebae have been widely used as model cells for studying a variety of biological phenomena, including cell motility, nucleocytoplasmic interactions, membrane function, and symbiosis. Results of studies by our group on amoebae as moving cells, as material for micrurgical manipulations, and as hosts for intracellular symbionts are summarized here. In particular, our recent studies of the amoeba as a microcosm, in which spontaneously infecting foreign microbes have become integrated as necessary cell components, are described in some detail. These processes have involved an initial microbial infection, mutual adaptation by the host and symbionts, and development of obligatory symbiosis. Evidence is presented to show that symbiont-derived macromolecules are involved in the protection of symbionts from digestion, the symbionts have acquired regulatory elements on their chromosomal genes to enhance production of beneficial gene products, and symbionts apparently utilize host-derived macromolecules to their benefit. These studies involved morphological observations both at light and electron microscopic levels, physiological and genetic studies, production and use of poly- and monoclonal antibodies, and molecular-biological approaches including gene cloning and sequencing. It is shown that amoebae are uniquely suited as model cells with which to study these phenomena.

Bacterial endosymbiont-derived lipopolysaccharides and a protein on symbiosome membranes in newly infected amoebae and their roles in lysosome-symbiosome fusion

Experimental results are presented to support the view that symbiont-derived lipopolysaccharides are involved in the prevention of lysosome-symbiosome fusion in xD amoebae harboring bacterial endosymbionts. Monoclonal antibodies against lipopolysaccharides and a 96-kDa protein present on symbiosome membranes of amoebae were used to monitor the appearance of the membrane-specific components in newly infected amoebae with endosymbionts from xD amoebae. The lipopolysaccharides and protein appeared on the newly forming symbiosome membranes within 3 to 7 days, as detected by indirect immunofluorescence staining with monoclonal antibodies. The lysosome-symbiosome fusion was followed by double staining of two antigens with different monoclonal antibodies applied to the same amoeba. Antilipopolysaccharide monoclonal antibodies were detected by staining with a fluorescein isothiocyanate-conjugated secondary antibody, and a biotinylated anti-lysosomal protein monoclonal antibody was detected by staining with Texas Red-conjugated streptavidin. In xD amoebae injected with an antilipopolysaccharide antibody, lysosomes fused with some of the symbiosomes that did not fuse with lysosomes in noninjected cells.

Cloning and characterization of the Escherichia coli K-12 rfa-2 (rfaC) gene, a gene required for lipopolysaccharide inner core synthesis

A genetically defined mutation, designated rfa-2, results in altered lipopolysaccharide (LPS) biosynthesis. rfa-2 mutants produce a core-defective LPS that contains lipid A and a single sugar moiety, 2-keto-3-deoxyoctulosonic acid, in the LPS core region. Such LPS core-defective or deep-rough (R) mutant structures were previously designated chemotype Re. Phenotypically, rfa-2 mutants exhibit increased permeability to a number of hydrophilic and hydrophobic agents. By restriction analyses and complementation studies, we clearly defined the rfa-2 gene on a 1,056-bp AluI-DraI fragment. The rfa-2 gene and the flanking rfa locus regions were completely sequenced. Additionally, the location of the rfa-2 gene on the physical map of the Escherichia coli chromosome was determined. The rfa-2 gene encodes a 36,000-dalton polypeptide in an in vivo expression system. N-terminal analysis of the purified rfa-2 gene product confirmed the first 24 amino acid residues as deduced from the nucleotide sequence of the rfa-2 gene coding region. By interspecies complementation, a Salmonella typhimurium rfaC mutant (LPS chemotype Re) is transformed with the E. coli rfa-2+ gene, and the transformant is characterized by wild-type sensitivity to novobiocin (i.e., uninhibited growth at 600 micrograms of novobiocin per ml) and restoration of the ability to synthesize wild-type LPS structures. On the basis of the identity and significant similarity of the rfa-2 gene sequence and its product to the recently defined (D. M. Sirisena, K. A. Brozek, P. R. MacLachlan, K. E. Sanderson, and C. R. H. Raetz, J. Biol. Chem. 267:18874-18884, 1992), the S. typhimurium rfaC gene sequence and its product (heptosyltransferase 1), the E. coli K-12 rfa-2 locus will be designated rfaC.

Susceptibility of Porphyromonas gingivalis and P. asaccharolytica to the non-oxidative killing mechanisms of human neutrophils

Neutrophils are essential for host defence against bacterial dental plaque and the pathogenic bacterial species within it, but in anaerobic environments such as the gingival crevice neutrophils can kill bacteria only with non-oxidative microbicidal compounds stored in their granules. Porphyromonas gingivalis W83, a pathogenic plaque species, and the avirulent non-oral type-strain P. asaccharolytica were incubated anaerobically with intact neutrophils and with compounds extracted from normal human neutrophil granules. The killing of bacteria and the inactivation of lysozyme, cathepsin G, elastase, bacterial-permeability increasing factor and defensins by culture supernatants were assayed. P. asaccharolytica but not P. gingivalis was killed under anaerobic conditions by intact neutrophils. P. gingivalis was also resistant to neutrophil granule compounds, its viability being reduced from a mean of 3.3 x 10(6) to 6.1 x 10(4) c.f.u/ml in 60 min by 400 micrograms/ml neutrophil granule extract, as compared to a reduction from 4.4 x 10(6) to 2.3 x 10(3) c.f.u/ml for P. asaccharolytica. P. gingivalis culture supernatant inactivated cathepsin G, elastase, bacterial-permeability increasing factor and defensins. Resistance to neutrophil non-oxidative killing mechanisms may be an important virulence factor for P. gingivalis.

Molecular cloning and expression of the 01 rfb region from a pyelonephritic Escherichia coli 01:H1:K7

The genes responsible for the biosynthesis of the O1 polysaccharide from a human pyelonephritic Escherichia coli were cloned and expressed in a rfb-deleted E. coli K-12 strain. Deletion analysis of the clone demonstrated that a DNA fragment size larger than 6.7 kb and smaller than 10 kb is responsible for O1-antigen biosynthesis.

Survival of smooth, rough and transposon mutant strains of Brucella abortus in bovine mammary macrophages

Transposon mutants offer a unique way to evaluate the role of lipopolysaccharide (LPS) by producing a theoretical single-gene difference between the original strain and the transposon mutant strain. Comparative survival of Brucella abortus smooth strain 2308, rough RB51, smooth strain 19, and two transposon mutant strains (rough strain 2308::Tn5 Lac Z [m106] and rough strain 19::Tn5 Lac Z [m3], was tested in restrictive bovine mammary macrophages that were able to effectively reduce the percentage of intracellular bacterial survival and permissive bovine mammary macrophages that were unable to control the intracellular replication of B. abortus. The theoretical single-gene difference between strain 19 and strain 19::Tn5 lac Z [m3] and between smooth virulent strain 2308 and rough transposon mutant 2308::Tn5 lacZ [m106] is likely related to differences in LPS content or structure. Significant (P less than 0.05) reduction in the survival of rough strain 19::Tn5 Lac Z [m3] with no significant reduction in the rough transposon mutant strain 2308::Tn5 lacZ [m106] indicated that at least one factor other than LPS contributes to the intracellular survival of B. abortus in bovine macrophages.

A 59 kiloDalton outer membrane protein of Salmonella typhimurium protects against oxidative intraleukocytic killing due to human neutrophils

We have isolated a Salmonella typhimurium (ST) mutant, JKS400, deficient in the production of a surface-exposed outer membrane protein (Omp) and phenotypically hypersensitive to the oxidative antimicrobial mechanism of polymorphonuclear leukocytes (PMNs). This Omp migrated at approximately 59 kiloDaltons (kD) in sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). We found with P22 transduction that the capacities to produce the protein and to exert wild-type resistance to oxidative killing were tightly linked. Transduction of JKS400 with a P22(HT)int- bacteriophage grown on a Tn10 insertion library in LT2 yielded tetracycline-resistant isolates that had been returned to wild-type protein production. Further experiments showed that restoration of protein production was accompanied by restoration of the parental resistance phenotype to killing by PMNs and by restoration to wild-type resistance to H2O2. The map position of the Tn10 was determined to be at 96 minutes in the Salmonella chromosome. This protein appears to behave as a virulence factor, promoting the capacity of Salmonella typhimurium LT2 to survive oxygen-dependent killing mechanisms in neutrophils.

O antigen and lipid A phosphoryl groups in resistance of Salmonella typhimurium LT-2 to nonoxidative killing in human polymorphonuclear neutrophils

We have compared the intraleukocytic survival of isogenic strains of Salmonella typhimurium, whose outer membrane lipopolysaccharide differed in O antigen and lipid A composition and whose susceptibility to nonoxidative antimicrobial granule proteins of human polymorphonuclear neutrophilis (PMN) could be established. We found that the order of resistance to the bactericidal activity of intact PMN of the three bacterial strains utilized closely resembled their ordered resistance to the purified human cationic antimicrobial 57,000-dalton protein (CAP57). LT-2, a smooth wild-type strain, was far more resistant than SH9178, its rough (Rb LPS) mutant. It was most significant that SH7426, a polymyxin B-resistant pmrA mutant of SH9178, not only was substantially more resistant to CAP57 and to intraphagocytic killing than SH9178 but also came close to being as resistant as LT-2. These experiments confirm earlier work that showed the importance of the glycosyl groups of O antigens of S. typhimurium for their resistance to O2-independent antimicrobial phagocytosis by PMN. The surprising result was that a rough strain, very susceptible to bactericide, became substantially more resistant when a mutation led to its lipid A phosphoryl groups being 100% substituted with amino pentoses. Yet unresolved is whether the protection is due to the loss of negative charges on the lipid A, the substitution of sugar molecules in vulnerable loci in the outer membrane, or both.

Mechanisms of human neutrophil-mediated cartilage damage in vitro: the role of lysosomal enzymes, hydrogen peroxide and hypochlorous acid

Cartilage is a focal point of attack by cellular and molecular elements of the inflammatory response which occurs in arthritic diseases. Neutrophils damage articular cartilage by degrading matrix components and inhibiting their synthesis. The aim of this study was to elucidate mechanisms of this damage. Human neutrophils were isolated from blood by centrifuging through Ficoll-Hypaque and granule extract prepared from them. Articular cartilage from adult humans and cattle was maintained in organ culture. Cartilage degradation (release of 35S-labelled proteoglycan) or synthesis (incorporation of 35S into proteoglycan) was determined after various treatments. Human neutrophils and neutrophil granule extract degraded proteoglycan and inhibited proteoglycan synthesis. The specific leucocyte elastase inhibitor N-methoxysuccinyl-(ala)2-pro-val-chloromethylketone (MAAPVCMK) partially reversed these effects. H2O2, a product of the neutrophil respiratory burst, when added directly at 10(-6)mol/L, or generated by glucose oxidase (GO)/glucose inhibited proteoglycan synthesis but had no effect on degradation. Hypochlorous acid (OHCl), a product of the myeloperoxidase (MPO)/H2O2/Cl system at 50 mumol/L degraded proteoglycan and inhibited its synthesis. OHCl produced by granule extract (as a source of MPO) + GO-generated H2O2 + Cl- degraded proteoglycan. The results indicate that neutrophil-mediated proteoglycan degradation and inhibition of synthesis is largely attributable to elastase and secondarily to OHCl, whereas H2O2 impairs synthesis without affecting degradation of proteoglycan.

Susceptibility of Salmonella typhimurium and Salmonella typhi to oxygen metabolites

The susceptibility of Salmonella typhimurium LT2 and S. typhi 1079 to oxygen metabolites were compared. S. typhimurium LT2 and S. typhi 1079 were killed to an equal extent (about 40%) by the xanthine-xanthine oxidase (200 mU/ml) system. Among the various scavengers of oxygen metabolites, catalase alone inhibited the killing of S. typhimurium LT2 and S. typhi 1079 by the xanthine-xanthine oxidase system, indicating that hydrogen peroxide contributed to the killing of Salmonellae. The respiratory burst of murine macrophages was efficiently triggered by the ingestion of S. typhimurium LT2, S. typhimurium SL1102, and S. typhi 1079 and all to the same extent. However, in the range of the concentration of hydrogen peroxide produced by murine macrophages, neither S. typhimurium LT2 nor S. typhi 1079 were killed. Only S. typhimurium SL1102, a rough mutant of S. typhimurium LT2, was markedly susceptible under these conditions. The findings suggest that both S. typhimurium LT2 and S. typhi 1079 are resistant to oxygen-dependent killing mechanisms.

Lipopolysaccharide structure determines ionic and hydrophobic binding of a cationic antimicrobial neutrophil granule protein

Bactericidal activity and binding of a 57,000-dalton cationic antimicrobial neutrophil granule protein (CAP57) are determined by the presence on bacteria of O-antigen polysaccharide chains and the availability of negatively charged groups in the lipid A region, the inner core region, or both regions of lipopolysaccharide. Polymyxin B (PMB)-resistant mutants with well-defined alterations in lipid A structure and charge (pmrA) are also more resistant to CAP57. We used biologically active radioiodinated CAP57 to study the characteristics and kinetics of binding to a sensitive Rb lipopolysaccharide chemotype, Salmonella typhimurium SH9178, and the relatively resistant pmrA mutant strain SH7426. Binding occurred rapidly and was specific and saturable. Because CAP57 appears to be bound in a manner similar to that of PMB, competition binding studies were performed. Excess PMB did compete with CAP57 for binding to SH9178. Nonapeptide, a polycationic derivative of PMB that has lost its hydrophobic portions, demonstrated a marked decrease in ability to compete for binding with CAP57 compared with PMB. This demonstrated the importance of hydrophobic binding in the interaction of CAP57 with the microbial surface. Thus, we have shown that binding of CAP57 to SH9178 is specific, saturable, and similar to binding of PMB. Both hydrophobic and ionic properties of CAP57 appear to be necessary for binding.

Killing of Proteus mirabilis by polymorphonuclear leukocyte granule proteins: evidence for species specificity by antimicrobial proteins

Low-molecular-weight (Mr, ca. 3,800) polypeptides containing human defensins HNP-1 and HNP-2 (T. Ganz, M. S. Selsted, D. Szlarek, S. L. Harwig, K. Daher, D. F. Bainton, and R. I. Lehrer, J. Clin. Invest. 76:1427-1434, 1985) prepared in our laboratory from acid extracts of human polymorphonuclear granulocyte granules and purified human defensins were found to exert potent bactericidal action against Proteus mirabilis. The antimicrobial action of the extracts of human polymorphonuclear leukocytes granules against P. mirabilis appears to be due to the presence of the defensins. Because P. mirabilis resists the antimicrobial action of other granule proteins, we interpret the present results to mean that the various antimicrobial proteins display species specificity in their microbicidal action.

Outer membrane permeability of Acinetobacter calcoaceticus mediates susceptibility to rat polymorphonuclear leukocyte granule contents

Growth of Acinetobacter calcoaceticus on specific alkanes altered the outer membrane permeability of the organism, as indicated by a change in sensitivity to the antibiotic actinomycin D. As the carbon length of the alkane energy source decreased, outer membrane permeability and susceptibility to actinomycin D increased. Concomitant with the increase in outer membrane permeability, A. calcoaceticus became more susceptible to the oxygen-independent antimicrobial activity of extracted contents from rat polymorphonuclear leukocyte granules. Individual fractions of granule extract possessed no antimicrobial activity against A. calcoaceticus. The alkane-induced change in outer membrane permeability was not associated with alterations of lipopolysaccharide O antigen. An outer membrane permeability mechanism, independent of changes in lipopolysaccharide content, mediating susceptibility to the oxygen-independent antimicrobial activity of rat polymorphonuclear leukocyte granule contents is suggested.

Isolation of a protein antigen from Coxiella burnetii

Antigens prepared from Coxiella burnetti, strain Frankfurt, phase II, propagated in persistently infected Buffalo Green Monkey (BGM) cell cultures were purified by guanidinium hydrochloride treatment and chloroform/methanol extraction. By ELISA analysis, chloroform/methanol residues (CMR) proved to be free of host cell antigens. The CMR were sensitive to trypsin, pronase E and proteinase K, as determined by absorption-kinetics of CMR suspensions at 600 nm and release of protein. Coomassie blue stained SDS polyacrylamide gels of proteinase hydrolysates from CMR revealed only a single component of apparently 27,000 D. Silver stained gels, however, showed a second component of apparently 12,000 D. In contrast, from untreated native C. burnetii a large variety of proteins, most of them protease-sensitive, were released by detergents at low temperatures, but the 27,000 D component was only solubilized at 60-100 degrees C. The 27,000 D component was obviously the major protein of CMR as well as of whole cells. Antigenicity of this 27,000 D protein could be demonstrated by agargel precipitation test, ELISA and immunoperoxidase techniques applying antisera raised against whole cells and against the extracted component. The component was also recognized in a dot immunobinding assay by sera from guinea pigs infected with cloned C. burnetii stain Nine Mile, phase I, thus indicating an important role of this antigen in C. burnetii specific immune response.

Defensins mediate the microbicidal activity of human neutrophil granule extract against Acinetobacter calcoaceticus

An acid extract of human neutrophil granules was fractionated on a Sephadex G-100 column and tested for microbicidal activity against Acinetobacter calcoaceticus HO-1 as described previously (M.C. Modrzakowski and C. M. Paranavitana, Infect. Immun. 32:668-674, 1981). The low-molecular-weight protein fraction, peak D, accounted for about 30% of the protein and nearly all of the activity of the crude extract against strain HO-1. Peak D protein proved to be a mixture of the three human defensin peptides HNP1, HNP2, and HNP3. Purified defensins reproduced the microbicidal activity of peak D. The data suggest that defensins could play a major role in the killing of A. calcoaceticus by human neutrophils.

Antimicrobial binding of a radiolabeled cationic neutrophil granule protein

A 57,000-dalton protein (CAP57) purified from human polymorphonuclear leukocytes has antimicrobial activity against a number of gram-negative bacteria. We developed a procedure using solid-phase Iodo-gen to radiolabel CAP57 without destroying its antibacterial activity. Iodinated and native CAP57 were electrophoretically identical. Autoradiographs of sodium dodecyl sulfate-polyacrylamide gels revealed greater than 95% of the 125I in a single heavy band in the 57,000-molecular-weight region. The quantity of [125I]CAP57 bound to bacterial test strains was directly proportional to the sensitivity to CAP57.

Plasmid RP1-mediated susceptibility of Acinetobacter calcoaceticus to rat polymorphonuclear leukocyte granule contents

The resistance plasmid RP1 was transferred by conjugation to a plasmidless strain of Acinetobacter calcoaceticus. Acquisition and expression of RP1 by A. calcoaceticus HO1-N was associated with an increase in sensitivity to the antimicrobial activity of extracted contents from rat polymorphonuclear leukocyte granules. Plasmid RP1-associated antibiotic resistance and sensitivity to granule contents were cured by exposure to acridine orange. Assays with granule extract fractions separated by fast protein liquid chromatography showed myeloperoxidase, protease, and lysozyme fractions to possess little or no antimicrobial activity against the A. calcoaceticus strains. A protein fraction designated peak D, containing two low-molecular-weight cationic peptides (M. J. Loeffelholz and M. C. Modrzakowski, Anal. Biochem., in press), did possess antimicrobial activity against both HO1-N and Ho1-N(RP1) strains, with the HO1-N(RP1) strain being significantly more sensitive.

Antigonococcal activity of human neutrophil cathepsin G

We have shown that lysosomal cathepsin G, prepared from acid extracts of granules derived from human polymorphonuclear granulocytes, exhibits potent in vitro antimicrobial activity against Neisseria gonorrhoeae. An isolated isozyme of cathepsin G was found to exhibit antigonococcal activity by a nonenzymatic mechanism in a time-dependent manner. Moreover, we observed that the antigonococcal activity of cathepsin G was relatively independent of pH and evident over a pH range resembling that invoked for maturing phagolysosomes. Using a number of isogenic strains, we determined that certain mutations known to alter cell envelope structure rendered gonococci more susceptible to cathepsin G. This suggests that the susceptibility of gonococci to cathepsin G, and possibly other antimicrobial proteins derived from PMN granules, is genetically determined and possibly related to the structure of the gonococcal cell envelope.

Late intraphagosomal hydrogen ion concentration favors the in vitro antimicrobial capacity of a 37-kilodalton cationic granule protein of human neutrophil granulocytes

We described previously (W.M. Shafer, L.E. Martin, and J.K. Spitznagel, Infect. Immun. 45:29-35, 1984) the presence of a 37-kilodalton cationic antimicrobial protein (37K CAP) in extracts of granules prepared from human polymorphonuclear granulocytes (PMN). In this investigation, we prepared 37K CAP from PMN granule extracts by sequential ion-exchange and molecular-sieve chromatography and examined its antimicrobial activity against a number of gram-negative and gram-positive bacteria. At concentrations of 5 micrograms/ml or lower, 37K CAP exerted selective antimicrobial activity against gram-negative bacteria. These bacteria included Acinetobacter lwoffii, Escherichia coli, Neisseria gonorrhoeae, Pseudomonas aeruginosa, Pseudomonas cepacia, Salmonella typhi, Salmonella typhimurium, and Shigella sonnei. However, at 5 micrograms of 37K CAP per ml, Proteus mirabilis, Proteus vulgaris, and Serratia marcescens resisted this antimicrobial activity. The bactericidal activity of 37K CAP was greatest in acidic (pH 5.5) as opposed to alkaline (pH 7.5) media. The level of S. typhimurium resistance to 37K CAP correlated with the presence of O antigen in the lipopolysaccharide. In the absence of O antigen repeat units, resistance was proportional to the length of the core oligosaccharide. These results suggest that 37K CAP may contribute significantly to the ability of PMN to kill gram-negative bacteria by nonoxidative means, particularly as the maturing phagolysosome becomes acidified.

Defensins. Natural peptide antibiotics of human neutrophils

We extracted a granule-rich sediment from normal human neutrophils and subjected it to chromatographic, electrophoretic, and functional analysis. The extract contained three small (molecular weight less than 3,500) antibiotic peptides that were named human neutrophil peptide (HNP)-1, HNP-2, and HNP-3, and which will be referred to as "defensins." HNP 1-3, a mixture of the three defensins, killed Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli effectively in vitro when tested in 10 mM phosphate buffer containing certain nutrients, but it had little or no bactericidal activity in nutrient-free buffer. In contrast, the nutrient-free buffer supported a high degree of activity by HNP 1-3 against Cryptococcus neoformans. In addition to its antibacterial and antifungal properties, HNP 1-3 directly inactivated herpes simplex virus, Type 1. Two of the individual purified defensins, HNP-1 and HNP-2, were as microbicidal as the mixture HNP 1-3. HNP-3 was less active than the other defensins against most but not all of the microbes tested. Immunoperoxidase stains revealed HNP 1-3 to have a granular localization in the neutrophil's cytoplasm by light microscopy. Frozen thin section immunogold transmission electron microscopy showed HNP 1-3 to be localized in azurophil granules. These studies define a broad-spectrum antimicrobial system in human neutrophils. The defensin system may operate in conjunction with or independently from oxygen-dependent microbicidal processes to enable human neutrophils to inactivate and destroy potential pathogens.

Oxygen-independent intracellular and oxygen-dependent extracellular killing of Escherichia coli S15 by human polymorphonuclear leukocytes

Effective killing of bacteria by polymorphonuclear leukocytes (PMN) is generally assumed to require intracellular sequestration and, depending on the bacterial species, can be both O2-dependent or O2-independent. Killing of several strains of Salmonella typhimurium and Escherichia coli by rabbit PMN does not require O2 and is apparently due to a granule-associated bactericidal/permeability-increasing protein (BPI) present in rabbit and human PMN. In this study we examined the O2 dependence of the killing of E. coli (S15) by human PMN. Ingested and noningested E. coli were separated by centrifugation after incubation with PMN in room air or under N2. In the presence of heat-treated serum approximately 50% of E. coli (10 bacteria/PMN) were taken up by PMN and rapidly (5-15 min) killed both in room air and under N2. The remaining extracellular bacteria (approximately 50%) were killed during 30-60 min of incubation in room air but not under N2. When uptake of E. coli by PMN was increased to approximately 80% by the use of C6-depleted serum (retaining heat-labile opsonins), bacterial survival under N2 was reduced from 54 +/- 7.6% to 13 +/- 5.5%. PMN from a patient with chronic granulomatous disease killed PMN-associated but not extracellular E. coli. BPI was detected, by indirect immunofluorescence, on the surface of PMN-associated E. coli within 5 min of incubation of E. coli with PMN both in room air and under N2. In contrast, at no time was BPI detected on the surface of extracellular E. coli, indicating that the non-PMN-associated E. coli had not been previously ingested. Thus, killing of ingested E. coli S15 by human as well as rabbit PMN does not require O2 and appears to be BPI-mediated. However, when ingestion is limited, extracellular bacteria can also be killed but principally by O2-dependent mechanisms.

Bactericidal activity of human lysozyme, muramidase-inactive lysozyme, and cationic polypeptides against Streptococcus sanguis and Streptococcus faecalis: inhibition by chitin oligosaccharides

The basis of the bactericidal activity of human lysozyme against Streptococcus sanguis was studied. Experiments were designed to evaluate the role of lysozyme muramidase activity in its bactericidal potency. Inactivation of the muramidase activity of lysozyme was achieved by reduction of essential disulfides with dithiothreitol (DTT) or by incubation with the chitin oligosaccharides chitotriose and chitobiose. Muramidase-inactive lysozyme, prepared by reduction with DTT, was equal in bactericidal potency to native lysozyme. Solutions of native chicken egg white lysozyme and human lysozyme exhibited equal bactericidal potency yet differed ca. fourfold with respect to lytic (muramidase) activity. The above results suggested that the bactericidal activity of lysozyme is not dependent upon muramidase activity. Chitotriose and chitobiose were found to inhibit both lytic and bactericidal activities of lysozyme. The bactericidal activity of muramidase-inactive lysozyme (reduction with DTT) was also inhibited by chitotriose and chitobiose. Further investigations demonstrated that chitotriose and chitobiose were also potent inhibitors of the bactericidal activity of the cationic homopolypeptides poly-L-arginine and poly-D-lysine. These latter results suggested that the essential bactericidal property of lysozyme was its extreme cationic nature and that some bacterial endogenous activities, inhibitable by chitotriose and chitobiose, were essential for expression of the bactericidal activity of either native or muramidase-inactive lysozyme or of the cationic homopolypeptides. Experiments with Streptococcus faecalis whole cells, cell walls, and crude autolysin preparations implicated endogenous autolytic muramidases as the bacterial targets of chitotriose and chitobiose. The essentially identical responses of S. sanguis and S. faecalis to chitotriose in bactericidal assays with muramidase-inactive lysozyme and polylysine suggested that muramidase-like enzymes exist in S. sanguis and, furthermore, play an essential role in cationic protein-induced loss of viability of the oral microbe.

Anaerobiosis increases resistance of Neisseria gonorrhoeae to O2-independent antimicrobial proteins from human polymorphonuclear granulocytes

We investigated the in vitro resistance of Neisseria gonorrhoeae FA19 to the O2-independent antimicrobial systems of human polymorphonuclear leukocytes. Acid extracts of polymorphonuclear leukocyte granules (crude granule extracts) and a purified granule protein (57 kilodaltons) were, at low concentrations, bactericidal for gonococci under aerobic conditions that permitted growth. However, they were less effective under anaerobic conditions that imposed bacteriostasis. We found that adding sodium nitrite to reduced growth media permitted the growth of strain FA19 in an anaerobic environment. Under these conditions with nitrite, anaerobic cultures of strain FA19 were no more resistant to the crude granule extract and the 57-kilodalton protein than aerobic cultures. In contrast, Salmonella typhimurium SL-1004, a facultative anaerobe, was readily killed by both the crude granule extract and the 57-kilodalton antimicrobial protein regardless of the presence or absence of free molecular oxygen. This is the first demonstration that an isolated antimicrobial protein from polymorphonuclear leukocyte granules is active against bacteria under anaerobic conditions. Our results also indicated that the efficacy of human polymorphonuclear leukocyte O2-independent killing of N. gonorrhoeae may, in part, be inhibited by bacteriostatic conditions imposed by hypoxia.

Brucellacidal activity of human and bovine polymorphonuclear leukocyte granule extracts against smooth and rough strains of Brucella abortus

The microbicidal activities of freeze-thaw and high-salt extracts of human and bovine polymorphonuclear leukocyte (PMN) granules were tested against a smooth intermediate strain (45/0) and a rough strain (45/20) of Brucella abortus which differ in virulence and survival within PMNs. Freeze-thaw extracts of human PMN granules were more brucellacidal than high-salt extracts when supplemented with hydrogen peroxide (H2O2) and potassium iodide (KI), whereas the opposite was found with freeze-thaw and high-salt extracts of bovine PMN granules. There was no oxygen-independent killing of either the smooth or rough strain of B. abortus by amounts of granule extracts which caused 100% killing of a deep rough mutant (Re) of Salmonella typhimurium. The oxygen-dependent brucellacidal activity of granule extracts was dependent on concentrations of myeloperoxidase (MPO) units, H2O2, and KI. Maximal brucellacidal activity was observed at pH 5.5 to 6.0. The smooth strain, 45/0, was more resistant to oxygen-dependent killing by granule extracts than was the rough strain, 45/20. Granule extracts were more brucellacidal than purified MPO at equivalent levels of MPO enzyme units, suggesting that at least one other reaction enhances killing by the MPO-H2O2-I- system.

Ingestion and intracellular survival of Brucella abortus in human and bovine polymorphonuclear leukocytes

Bovine polymorphonuclear leukocytes (PMNs) were found to be significantly more bactericidal than human PMNs against a smooth-intermediate strain of Brucella abortus (45/0), whereas there was no difference in bactericidal activity of the two kinds of PMNs against a rough strain of B. abortus (45/20). Electron microscopy of thin sections of PMNs revealed that both strains of B. abortus were readily ingested; however, the extent of degranulation was significantly less than in PMNs incubated with an extracellular parasite, Staphylococcus epidermidis. Amounts of myeloperoxidase and lactoferrin released through exocytosis by PMNs incubated with S. epidermidis were 4.7- and 1.2-fold greater, respectively, than those released from PMNs incubated with B. abortus 45/0. When azurophil and specific granules were isolated after incubation of PMNs with either B. abortus 45/0 or S. epidermidis, results showed that the extent of degranulation by both types of granules was greater in PMNs incubated with S. epidermidis than in those incubated with B. abortus 45/0. Amounts of degranulation by azurophil and specific granules were similar in PMNs incubated with either the smooth-intermediate strain 45/0 or the rough strain 45/20. Degranulation was not stimulated when glutaraldehyde-killed strain 45/0 was substituted for viable cells. These data suggest that B. abortus does not stimulate an effective level of degranulation after ingestion, as observed with extracellular parasites, and that the smooth intermediate strain 45/0 is more resistant to intraleukocytic killing system than the rough strain 45/20.

Cationic antimicrobial proteins isolated from human neutrophil granulocytes in the presence of diisopropyl fluorophosphate

Acid (0.2 M sodium acetate, pH 4.0) extracts of granules recovered from disrupted human polymorphonuclear granulocytes (PMNs) exhibited in vitro antimicrobial activity against Salmonella typhimurium. To minimize proteolytic destruction or modification of antimicrobial proteins derived from these granules, we pretreated the PMNs with the serine protease inhibitor diisopropyl fluorophosphate. Fractionation of such extracts by carboxymethyl Sephadex and Sephadex G-75 chromatography resulted in the recovery of at least two antimicrobial, cationic proteins. These proteins differed substantially in antimicrobial activity, amino acid composition, and molecular weight (Mr, 37,000 and 57,000). As we have shown before (Shafer et al., Infect. Immun. 43:834-858), with unfractionated proteins, these two proteins exhibited diminished activity against a polymyxin B-resistant (PBr) mutant of S. typhimurium compared with their activity against the isogenic parental polymyxin B-sensitive (PBs) strain. Expression of the relevant mutation (prmA) in the PBr mutant decreases the electronegativity of lipid A, owing to increased 4-amino-4-deoxy-L-arabinosylation at the 4' phosphate residue (Vaara et al., FEBS Lett. 129:145-149). The data suggest that at least two different cationic proteins account for the antimicrobial capacity of extracts from human PMN granules. Moreover, the availability of anionic charges in the outer membrane of S. typhimurium due to free lipid A phosphates apparently dictates phenotypic levels of resistance to both of the cationic proteins extracted from human PMN granules.

Growth-inhibitory and bactericidal effects of human parotid salivary histidine-rich polypeptides on Streptococcus mutans

Growth inhibition and cell viability assays demonstrate that the histidine-rich polypeptides isolated from human parotid saliva are bacteriostatic and bactericidal for strains of Streptococcus mutans belonging to the serotype b and c classifications. Both inhibition of growth and cell division are enhanced by preincubation of bacteria with these polypeptides in low-ionic-strength buffers of acidic and neutral pH before dilution into enriched growth media. With prior exposure at pH 6.8, inhibition by these polypeptides of the serotype c strains, S. mutans GS5 and SB, as well as the serotype b strain, S. mutans BHT, is reversible over time under the experimental conditions selected. With similar exposure at pH 5.2, however, irreversible damage is manifested by complete inhibition of both growth and cell viability. At concentrations of 250 micrograms of the mixture of histidine-rich polypeptides per 5 X 10(5) bacterial cells per ml in the acidic preincubation buffer, bacterial lethality is maintained for a period of 48 h in the enriched growth media. At a 50-micrograms/ml concentration of these salivary agents, approximately 80% killing of S. mutans SB is noted after a 24-h incubation; however, surviving bacteria multiply and reach turbidities of untreated control cells when examined at the 48-h growth point. Similarly, hen egg white lysozyme is also found to be bactericidal for these microorganisms when preincubation is carried out under acidic conditions. However, in contrast to the histidine-rich polypeptides, lysozyme under these experimental conditions does not inhibit growth of S. mutans SB at neutral pH, although it does inhibit growth of both S. mutans BHT and S. mutans GS5 at this pH. Preexposure of S. mutans SB to the peptides in buffer at ionic strengths of 0.025 to 0.125, followed by either viability assays under nongrowing conditions or growth inhibition studies, suggests that there is very little effect of ionic strength on the antibacterial function of these peptides. In contrast to the inhibition of viability noted under growing conditions, lower concentrations of the histidine-rich polypeptides were required to elicit immediate cell death under nongrowing conditions.

Oxygen-independent killing of Bacteroides fragilis by granule extracts from human polymorphonuclear leukocytes

Granule proteins from human neutrophils were prepared by extraction with acetate, and their antibacterial activity against Bacteroides fragilis was determined. Activity was highly dependent on pH; greatest killing occurred at the most acid pH tested (pH 5.0). Optimum activity was observed at physiological ionic strength and low bacterial numbers. Killing was inhibited by incubation temperatures of less than 37 degrees C. Eight times more extract was required to kill 50% of stationary-phase bacteria, compared with those growing in logarithmic phase. The antibacterial effect of granule extract was destroyed by boiling, but some activity was retained after heating to 56 degrees C and 80 degrees C. Granule extract activity was tested under conditions in which oxygen-dependent antibacterial systems were inhibited. The rate and extent of killing was not affected by anaerobiosis, sodium azide, or cysteine hydrochloride. These results suggest that the activity of granule extract is independent of oxidative antibacterial systems, and therefore, under conditions that occur in anaerobic infections, potent leukocyte granule-associated mechanisms exist for the destruction of B. fragilis.

Lipid A and resistance of Salmonella typhimurium to antimicrobial granule proteins of human neutrophil granulocytes

Granule extracts from human polymorphonuclear leukocytes were prepared and fractionated by chromatography on Sephadex G75-SF. One fraction exhibited potent antimicrobial activity against an Rd1 lipopolysaccharide (LPS) mutant of Salmonella typhimurium. Susceptibility of the mutant to antimicrobial activity appeared to be due to binding of granule proteins to lipid A because isolated native LPS succeeded in blocking the antimicrobial activity of granule extracts whereas base-hydrolyzed LPS failed to do so. Centrifugation of control and base-hydrolyzed LPS-protein mixtures in cesium chloride gradients suggested that only control LPS formed complexes with antimicrobial proteins. Further evidence that bactericidal proteins from polymorphonuclear leukocyte granules interact with lipid A was that sublethal concentrations of polymyxin B (an antibiotic known to bind to lipid A) rendered target bacteria phenotypically resistant to granule proteins. Moreover, a mutant of S. typhimurium which synthesized a lipid A with decreased electronegativity due to increased 4-amino-4-deoxy-L-arabinosylation at the 4'-phosphate exhibited increased resistance to both polymyxin B and granule proteins. These results suggest that polymyxin B and antimicrobial proteins derived from polymorphonuclear leukocyte granules interact with lipid A in an analogous manner.

Nonoxidative antimicrobial reactions of leukocytes

Increasingly abundant evidence supports the hypothesis that PMNs and perhaps alveolar macrophages have antimicrobial mechanisms independent of the presences of molecular oxygen for effective action against an array of bacteria and against some fungi. Eosinophils have mechanisms toxic for schistosomula and Trichinella larvae. In all instances the antimicrobial substances isolated have been cationic proteins and, in PMNs, associated with the azurophil cytoplasmic granules of the PMNs. Several of these substances have thus far demonstrated no enzymic function. Two of these substances are serine proteases but in one, chymotrypsin-like protein, the antimicrobial action depends on the cationic properties of the protein and is independent of the proteolytic action of the substance. In most instances, these proteins are cationic due to relatively large proportions of arginine. In two instances, a large proportion of lysine is present. All have high proportions (about 50%) of hydrophobic amino acid. Such proteins occur in the PMNs of man, rabbit, guinea pig, rat, cow, and chicken. The present view is that they are most active against gram-negative bacteria. At least two of them-37-kd and 57-kd proteins (Shafer and Spitznagel, 1983)-act on S. typhimurium in a manner analogous to that of polymyxin B through binding to lipid A. Currently available results shows that anaerobic PMNs have substantial antimicrobial capacity. Whether this capacity is due to the O2-independent mechanisms discussed in this chapter remains to be established with greater certainty.

Bactericidal activity of a granule extract from human polymorphonuclear leukocytes against Bacteroides species

The microbicidal activity of an acetate extract of human polymorphonuclear leukocyte granules was tested against Bacteroides fragilis, Bacteroides vulgatus, Bacteroides distasonis and Bacteroides thetaiotaomicron. All strains tested were killed by the extract, and there were no significant differences between the different Bacteroides species.

Procedure for isolation of bacterial lipopolysaccharides from both smooth and rough Pseudomonas aeruginosa and Salmonella typhimurium strains

Lipopolysaccharide (LPS) is a major component of the outer membrane of gram-negative bacteria. It is now well established that within a single organism, size heterogeneity of this molecule can exist. We have developed a LPS isolation procedure which is effective in extracting both smooth and rough LPS in high yields (51 to 81% of the LPS present in whole cells as quantitated by using hydroxy fatty acid, heptose, and 2-keto-3-deoxyoctonate yields) and with a high degree of purity. The contamination by protein (0.1% by weight of LPS), nucleic acids (1%), lipids (2 to 5%), and other bacterial products was low. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the LPS demonstrated the presence of a high degree of size heterogeneity in the isolated smooth LPS as well as the presence of significant amounts of rough-type LPS. The Pseudomonas aeruginosa LPS interacted well with a monoclonal antibody in a variety of immunochemical analyses. The usefulness of the procedure was demonstrated by comparing LPS preparations obtained from wild-type and mutant strains of P. aeruginosa and Salmonella typhimurium. For example, it was shown that the LPS of an antibiotic supersusceptible mutant Z61 of P. aeruginosa, which was previously characterized as identical to wild type with respect to the ratio of smooth to rough LPS molecules isolated by the phenol-water procedure, actually contained only a small proportion of O-antigenic side chains.

Potency of bactericidal proteins purified from the large granules of bovine neutrophils

The novel population of large granules of bovine neutrophils, which is the cell store of bactericidal activity independent of O2 derivatives, was extracted with an acid medium. Several fractions were resolved from the extract by ion-exchange chromatography (with carboxymethyl-cellulose) and gel filtration (with Sephadex G-50). Some of these fractions contained only a very limited number of major components, as detected by polyacrylamide gel electrophoresis. The purified bactericidal proteins exhibited their activity at 0.1 to 10 micrograms/0.3 ml of assay mixture containing 1 X 10(6) to 2 X 10(6) CFU of Staphylococcus aureus or Escherichia coli in media with physiological concentrations of Na+, K+, Mg2+, and Ca2+. Two fractions, containing polypeptides with apparent molecular weights ranging from 28,000 to less than 12,000, caused rather selective and rapid (5 to 20 min) killing of S. aureus. Their action was accompanied by significant binding to the gram-positive bacteria of some low (less than 12,000)-molecular-weight components. Other Sephadex G-50 fractions, containing the first emerging proteins with relatively high molecular weights, were more active on E. coli than on S. aureus. With the gram-negative bacteria there was a 10-min delay in the onset of bactericidal activity, which thereafter developed very fast. On the basis of the in vitro potency of the large-granule bactericidal proteins, we suggest that even partial discharge of granule content into the phagosomes may supply the phagocytic vacuoles of bovine neutrophils with a very efficient nonoxidative bactericidal system acting on both gram-positive and gram-negative microorganisms.

Bactericidal activity of granule contents from rat polymorphonuclear leukocytes

Granule contents from rat polymorphonuclear neutrophils were prepared by extraction with 0.2 M acetate (pH 4), dialyzed against phosphate-buffered saline (pH 7), and tested for bactericidal activity. Bactericidal assays consisted of mixing rat granule extract with 1 x 10(3) to 3 x 10(3) bacterial cells per ml at 37 degrees C for 1 h in a medium suited for bacterial growth. The granule extract demonstrated a distinctive dose-dependent bactericidal activity against outer membrane lipopolysaccharide mutants of Salmonella typhimurium LT-2, independent of added hydrogen peroxide or other active oxygen derivatives. The rough bacterial mutants showed an ordered increase in sensitivity to the rat lysosomal extracts inversely related to the length of their lipopolysaccharide carbohydrate side chains. Fractionation of the rat polymorphonuclear neutrophil granule extract with Sephadex G-100 column chromatography revealed an elution profile containing three major areas (peaks) of protein. Polyacrylamide gel electrophoresis and examination of enzymatic activity showed that these peaks contained myeloperoxidase (peak A), neutral protease (peak B), and lysozyme (peak C) activities. Also observed in peak C were cationic protein species whose cathodal electrophoretic migration was faster than that for lysozyme. Only peak C exhibited a bactericidal activity against the rough mutants of S. typhimurium LT-2 similar to that obtained for the unfractionated granule extract, with susceptibility of the bacterial mutants increasing with a progressive loss of carbohydrate residues in the lipopolysaccharide of the cell wall. The bactericidal activity of the peak C protein fraction was dose dependent. Boiling the unfractionated granule extract or peak C for 30 min had little affect on their antimicrobial activity when reacted against a deep-rough lipopolysaccharide mutant. However, trypsin pretreatment of these fractions significantly reduced their antimicrobial activity for the same mutant chemotype.

Outer membrane mutants of Salmonella typhimurium LT2 have lipopolysaccharide-dependent resistance to the bactericidal activity of anaerobic human neutrophils

The capacity of neutrophil polymorphonuclear granulocytes (PMNs) to phagocytize bacteria under anaerobic as well as aerobic conditions afforded the opportunity to compare the bactericidal activities of oxygen-independent and oxygen-dependent antimicrobial mechanisms in human PMNs challenged with Salmonella typhimurium LT2 and its lipopolysaccharide mutants (outer membrane mutants). Anaerobic human PMNs challenged with either opsonized LT2 or serum-treated zymosan failed to produce detectable superoxide anion (O2-) or to reduce nitroblue tetrazolium, although aerobic PMNs readily produced O2- in response to such challenge. Anaerobic PMNs killed these bacteria in an ordered fashion that appeared to be dependent on their lipopolysaccharide chemotype. As the carbohydrate content of the mutant lipopolysaccharide decreased, the bacteria became less resistant to the oxygen-independent bactericidal activity. The results resembled the ordered resistance to oxygen-independent killing observed with LT2 and its mutants in PMN-free systems with PMN granule proteins. Studies on the kinetics of killing showed these to be less rapid in anaerobic as compared with aerobic conditions. Opsonization increased the rate of phagocytosis, but such factors as opsonization and the rate of phagocytosis did not appear to affect intraleukocytic bactericidal capacity in that the resultant proportion of bacteria remaining viable after ingestion was similar regardless of which serum was used (normal serum, C6-deficient serum, C8-deficient serum, or no serum at all). The results are consistent with an active and substantial participation by oxygen-independent systems in the antimicrobial effects of neutrophils.

Pyocin-resistant lipopolysaccharide mutans of Neisseria gonorrhoeae: alterations in sensitivity to normal human serum and polymyxin B

Pyocins from Pseudomonas aeruginosa were used to select several lipopolysaccharide (LPS) mutants of Neisseria gonorrhoeae strain FA19. Three classes of LPS mutans were found in the initial group selected for study. The LPS of one class lacked galactose. That of a second group lacked the typical heptose found in the parental LPS, was reduced in glucose, galactose, and N-acetylglucosamine content, appeared to contain a new unidentified sugar component, and consisted of two species of LPS separable on sodium dodecyl sulfate-polyacrylamide gels. The LPS of a third strain lacked the heptose, glucose, galactose, and N-acetylglucosamine found in the oligosaccharide portion of parental FA19 LPS. The minimal inhibitory concentration for polymyxin B of the mutant strains was 3 to 4 times that of the parental strain. The strains lacking only galactose were as resistant as the parent to the bactericidal action of normal human serum, but cells of the other two classes were quickly killed by serum. Gonococcal LPS thus appears to be important in determining phenotypic properties of the cells.

Bactericidal activity in fractionated granule contents from human polymorphonuclear leukocytes: studies with leukocytes from normal individuals

Sephadex G-100 chromatographic fractions of granule extracts from normal human polymorphonuclear leukocytes, exhibiting differences from fractions previously obtained from leukemic polymorphonuclear leukocytes, possessed cationic proteins with distinct bactericidal activity against cell wall mutants of Salmonella typhimurium LT2.

Effects of human neutrophil granule extracts on macromolecular synthesis in Neisseria gonorrhoeae

Neisseria gonorrhoeae were exponentially killed for 120 min (i.e., they were prevented from forming colonies on agar) by extracts of human neutrophil granules; however, macromolecular synthesis, indicated by incorporation of radiolabeled precursors in trichloroacetic acid-precipitable material, continued at or above zero time control values for 45 min. Protein, deoxyribonucleic acid, and ribonucleic acid synthesis appeared to decrease simultaneously after 45 min. Little or no lysis gonococci occurred during the first 60 min of incubation. The ions K+, Na+, Ca2+, Cl1-, SO4(2-) and PO4(3-) at concentrations of less than or equal to 100 mM did not affect granule extract bactericidal activity. On the other hand, 20 mM Mg2+ completely inhibited killing when initially present along with granule extract or when added within 2 to 5 min after granule extract was added to a suspension of gonococci. Gonococci treated with granule extract, washed, and then incubated in gonococci. Gonococci treated with granule extract, washed, and then incubated in the absence of extract died as if extract were still present. The ability of subinhibitory concentrations of actinomycin D or erythromycin to inhibit growth and protein and nucleic acid synthesis was synergistically increased in the presence of granule extract. The above information suggests that a bactericidal component(s) of human neutrophil granules sticks to gonococci, altering their outer membrane permeability and their ability to divide.

Enhanced susceptibility of Escherichia coli to intracellular killing by human polymorphonuclear leukocytes after in vitro incubation with chloramphenicol

The effect of brief exposure to chloramphenicol of a pathogenic strain of Escherichia coli on susceptibility to normal human leukocytes was examined. Leukocytes killed chloramphenicol-pretreated E. coli more efficiently than they did untreated controls. Phagocytosis of pretreated bacteria, as measured by the uptake of radiolabeled bacteria and by direct visual count of engulfed bacteria, was not significantly increased. The decrease in viability was associated with enhanced intracellular killing of phagocytosed antibiotic-damaged bacteria. Chloramphenicol pretreatment altered the frequency distribution of intracellular bacteria by decreasing the number of leukocytes containing multiple stainable bacteria. Leukocytes failed to kill chloramphenicol-pretreated E. coli in the presence of phenylbutazone, which allowed an accumulation of intracellular bacteria. These results indicate that exposure of E. coli to chloramphenicol renders the bacteria more susceptible to intracellular killing and degradation.