Nonoxidative antimicrobial reactions of leukocytes

The role of neutrophils and monocytic cells in controlling the initiation of Clostridium perfringens gas gangrene

Clostridium perfringens is a common cause of the fatal disease gas gangrene (myonecrosis). Established gas gangrene is notable for a profound absence of neutrophils and monocytic cells (phagocytes), and it has been suggested that the bactericidal activities of these cells play an insignificant role in controlling the progression of the infection. However, large inocula of bacteria are needed to establish an infection in experimental animals, suggesting phagocytes may play a role in inhibiting the initiation of gangrene. Examination of tissue sections of mice infected with a lethal (1 x 10(9)) or sublethal (1 x 10(6)) inoculum of C. perfringens revealed that phagocyte infiltration in the first 3 h postinfection was inhibited with a lethal dose but not with a sublethal dose, indicating that exclusion of phagocytes begins very early in the infection cycle. Experiments in which mice were depleted of either circulating monocytes or neutrophils before infection with C. perfringens showed that monocytes play a role in inhibiting the onset of gas gangrene at intermediate inocula but, although neutrophils can slow the onset of the infection, they are not protective. These results suggest that treatments designed to increase monocyte infiltration and activate macrophages may lead to increased resistance to the initiation of gas gangrene.

Effects of Clostridium perfringens alpha-toxin (PLC) and perfringolysin O (PFO) on cytotoxicity to macrophages, on escape from the phagosomes of macrophages, and on persistence of C. perfringens in host tissues

Clostridium perfringens is the most common cause of clostridial myonecrosis (gas gangrene). Polymorphonuclear cells (PMNs) appear to play only a minor role in preventing the onset of myonecrosis in a mouse animal model of the disease (unpublished results). However, the importance of macrophages in the host defense against C. perfringens infections is still unknown. Two membrane-active toxins produced by the anaerobic C. perfringens, alpha-toxin (PLC) and perfringolysin O (PFO), are thought to be important in the pathogenesis of gas gangrene and the lack of phagocytic cells at the site of infection. Therefore, C. perfringens mutants lacking PFO and PLC were examined for their relative cytotoxic effects on macrophages, their ability to escape the phagosome of macrophages, and their persistence in mouse tissues. C. perfringens survival in the presence of mouse peritoneal macrophages was dependent on both PFO and PLC. PFO was shown to be the primary mediator of C. perfringens-dependent cytotoxicity to macrophages. Escape of C. perfringens cells from phagosomes of macrophage-like J774-33 cells and mouse peritoneal macrophages was mediated by either PFO or PLC, although PFO seemed to play a more important role in escape from the phagosome in peritoneal macrophages. At lethal doses (10(9)) of bacteria only PLC was necessary for the onset of myonecrosis, while at sublethal doses (10(6)) both PFO and PLC were necessary for survival of C. perfringens in mouse muscle tissue. These results suggest PFO-mediated cytotoxicity toward macrophages and the ability to escape macrophage phagosomes may be important factors in the ability of C. perfringens to survive in host tissues when bacterial numbers are low relative to those of phagocytic cells, e.g., early in an infection.

Association of Salmonella enterica serovar enteritidis yafD with resistance to chicken egg albumen

Salmonella enterica serovar Enteritidis is a major cause of food-borne diseases in industrialized countries. The incidence of S. enterica serovar Enteritidis infections has increased substantially in recent decades, and S. enterica serovar Enteritidis is now one of the leading serovars of Salmonella in the United States. A unique epidemiological characteristic of S. enterica serovar Enteritidis is its association with chicken shell eggs, since approximately 80% of all human gastrointestinal diseases can be traced to contaminated egg products. Eggs are contaminated when bacteria from reproductive tissues of infected hens are packaged into the eggs and persist inside the hostile egg albumen environment. Therefore, resistance to egg albumen is an important aspect in the transmission of S. enterica serovar Enteritidis. We identified a gene, yafD from S. enterica serovar Enteritidis, whose overexpression conferred upon S. enterica serovar Typhimurium enhanced resistance to egg albumen, while disruption of this gene in S. enterica serovar Enteritidis rendered the organism more susceptible to egg albumen. YafD is homologous to members of an exonuclease-endonuclease-phosphatase family, including some enzymes involved in DNA repair. Furthermore, we discovered that egg albumen has nuclease activities and uses both circular and linear DNA as substrates. We propose that YafD provides a survival advantage to S. enterica serovar Enteritidis in eggs by repairing DNA damage caused by egg albumen and that it may be one of the biologic determinants that contribute to the epidemiological association of S. enterica serovar Enteritidis with egg products.

Antimicrobial peptides from human platelets

Platelets share structural and functional similarities with granulocytes known to participate in antimicrobial host defense. To evaluate the potential antimicrobial activities of platelet proteins, normal human platelets were stimulated with human thrombin in vitro. Components of the stimulated-platelet supernatants were purified to homogeneity by reversed-phase high-performance liquid chromatography. Purified peptides with inhibitory activity against Escherichia coli ML35 in an agar diffusion antimicrobial assay were characterized by mass spectrometry, amino acid analysis, and sequence determination. These analyses enabled the identification of seven thrombin-releasable antimicrobial peptides from human platelets: platelet factor 4 (PF-4), RANTES, connective tissue activating peptide 3 (CTAP-3), platelet basic protein, thymosin beta-4 (Tbeta-4), fibrinopeptide B (FP-B), and fibrinopeptide A (FP-A). With the exception of FP-A and FP-B, all peptides were also purified from acid extracts of nonstimulated platelets. The in vitro antimicrobial activities of the seven released peptides were further tested against bacteria (E. coli and Staphylococcus aureus) and fungi (Candida albicans and Cryptococcus neoformans). Each peptide exerted activity against at least two organisms. Generally, the peptides were more potent against bacteria than fungi, activity was greater at acidic pHs, and antimicrobial activities were dose dependent. Exceptions to these observations were observed with PF-4, which displayed a bimodal dose-response relationship in microbicidal assays, and Tbeta-4, which had greater activity at alkaline pHs. At concentrations at which they were individually sublethal, PF-4 and CTAP-3 exerted synergistic microbicidal activity against E. coli. Collectively, these findings suggest a direct antimicrobial role for platelets as they are activated to release peptides in response to trauma or mediators of inflammation.

Role of YadA in resistance to killing of Yersinia enterocolitica by antimicrobial polypeptides of human granulocytes

The virulence plasmid pYVe of Yersinia enterocolitica codes for the production of the outer membrane protein YadA and the secretion of several proteins, called Yops, which may protect this bacterium against killing by human granulocytes. Granulocytes kill ingested microorganisms by oxygen-dependent and oxygen-independent mechanisms, the latter including antimicrobial polypeptides. The aim of this study was to determine whether virulent (pYVe+) Y. enterocolitica and plasmid-cured avirulent (pYVe-) Y. enterocolitica differ in susceptibility to antimicrobial polypeptides extracted from granules of human granulocytes. The acetic acid granule extract contained several polypeptides with antimicrobial activity against Y. enterocolitica as determined by gel overlay and radial diffusion assays. Two of these polypeptides were identified as lysozyme and defensins. pYVe+ Y. enterocolitica was less susceptible than pYVe- Y. enterocolitica to the antimicrobial activity of granule extract, lysozyme, and defensins as determined in a suspension assay, which indicated that the pYVe plasmid mediates a reduced susceptibility to these polypeptides. The role of YadA in the resistance to antimicrobial polypeptides was analyzed by using mutants of Y. enterocolitica that specifically lack or express YadA. The results demonstrated that YadA conferred resistance to the killing of Y. enterocolitica by the granule extract. Together, these results indicate that the plasmid-encoded factor YadA contributes to the resistance of Y. enterocolitica to the killing by antimicrobial polypeptides of human granulocytes.

Spontaneous pmrA mutants of Salmonella typhimurium LT2 define a new two-component regulatory system with a possible role in virulence

We isolated spontaneous mutations (pmrA) in the smooth strain Salmonella typhimurium LT2 that show increased resistance to the cationic antibacterial proteins of human neutrophils and to the drug polymyxin B. The mutation in one strain, JKS5, maps to 93 min on the S. typhimurium chromosome, near the proP gene and the melAB operon. The mutation, designated pmrA505, confers a 1,000-fold increase in resistance to polymyxin B and a 2- to 4-fold increase in resistance to neutrophil proteins. We cloned both the pmrA505 and pmrA+ alleles and found that the pmrA+ gene is partially dominant over pmrA505. DNA sequence analysis of the pmrA505 clone revealed three open reading frames (ORFs). The deduced amino acid sequences indicated that ORF1 encodes a 548-amino-acid (aa) protein with a putative membrane-spanning domain and no significant homology to any known protein. ORF2 and ORF3, which encode 222- and 356-aa proteins, respectively, show strong homology with the OmpR-EnvZ family of two-component regulatory systems. ORF2 showed homology with a number of response regulators, including OmpR and PhoP, while ORF3 showed homology to histidine kinase-sensor proteins EnvZ and PhoR. Genetic analysis of the cloned genes suggested that ORF2 contained the pmrA505 mutation. Comparison of the pmrA505 and pmrA+ ORF2 DNA sequences revealed a single G-A transition, which would result in a His-to-Arg substitution at position 81 in the ORF2 mutant protein. We therefore designate ORF2 PmrA and ORF3 PmrB. The function of ORF1 is unknown.

Killing of endothelial cells and release of arachidonic acid. Synergistic effects among hydrogen peroxide, membrane-damaging agents, cationic substances, and proteinases and their modulation by inhibitors

51Chromium-labeled rat pulmonary artery endothelial cells (EC) cultivated in MEM medium were killed, in a synergistic manner, by mixtures of subtoxic amounts of glucose oxidase-generated H2O2 and subtoxic amounts of the following agents: the cationic substances, nuclear histone, defensins, lysozyme, poly-L-arginine, spermine, pancreatic ribonuclease, polymyxin B, chlorhexidine, cetyltrimethyl ammonium bromide, as well as by the membrane-damaging agents phospholipases A2 (PLA2) and C (PLC), lysolecithin (LL), and by streptolysin S (SLS) of group A streptococci. Cytotoxicity induced by such mixtures was further enhanced by subtoxic amounts either of trypsin or of elastase. Glucose-oxidase cationized by complexing to poly-L-histidine proved an excellent deliverer of membrane-directed H2O2 capable of enhancing EC killing by other agonists. EC treated with rabbit anti-streptococcal IgG were also killed, in a synergistic manner, by H2O2, suggesting the presence in the IgG preparation of cross-reactive antibodies. Killing of EC by the various mixtures of agonists was strongly inhibited by scavengers of hydrogen peroxide (catalase, dimethylthiourea, MnCl2), by soybean trypsin inhibitor, by polyanions, as well as by putative inhibitors of phospholipases. Strong inhibition of cell killing was also observed with tannic acid and by extracts of tea, but less so by serum. On the other hand, neither deferoxamine, HClO, TNF, nor GTP gamma S had any modulating effects on the synergistic cell killing. EC exposed either to 6-deoxyglucose, puromycin, or triflupromazin became highly susceptible to killing by mixtures of hydrogen peroxide with several of the membrane-damaging agents. While maximal synergistic EC killing was achieved by mixtures of H2O2 with either PLA2, PLC, LL, or with SLS, a very substantial release of [3H]arachidonic acid (AA), PGE2, and 6-keto-PGF occurred only if a proteinase was also added to the mixture of agonists. The release of AA from EC was markedly inhibited either by scavengers of H2O2, by proteinase inhibitors, by cationic agents, by HClO, by tannic acid, and by quinacrin. We suggest that cellular injury induced in inflammatory and infectious sites might be the result of synergistic effects among leukocyte-derived oxidants, lysosomal hydrolases, cytotoxic cationic polypeptides, proteinases, and microbial toxins, which might be present in exudates. These "cocktails" not only kill cells, but also solubilize AA and several of its metabolites. However, AA release by the various agonists can be also achieved following attack by leukocyte-derived agonists on dead cells. It is proposed that treatment by "cocktails" of adequate antagonists might be beneficial to protect against cellular injury in vivo.

Human polymorphonuclear leucocytes stimulated by tumour necrosis factor-alpha show increased adherence to extracellular matrix proteins which is mediated via the CD11b/18 complex

The present study demonstrates that tumour necrosis factor (TNF) and FMLP, but not IL-1 or IL-8, enhanced the adherence of polymorphonuclear neutrophil (PMN) to fibronectin, an extracellular matrix protein. The adherence induced by FMLP was very rapid, within 5 min while the induction of adherence by TNF was much slower, reaching maximum at 60 min. TNF also enhanced an adhesion of PMN to other extracellular matrix proteins, such as laminin, collagen IV and gelatin II, but not to human serum albumin. Anti-CD18 MoAb completely inhibited the binding of TNF-stimulated PMN to fibronectin and partially inhibited the binding to laminin. Further investigation showed that adhesion of TNF-stimulated PMN to fibronectin and laminin was inhibited by anti-CD11b MoAb and to a lesser extent by CD11a MoAb. In contrast to TNF-stimulated PMN the binding of unstimulated PMN to fibronectin and laminin was only inhibited by anti-CD11a MoAb. Anti-CD11c had no effect on PMN adherence. These results suggest that unstimulated PMN adhere to extracellular proteins through the CD11a/18, while TNF-stimulated PMN adhere through the CD11b/18. These results suggest that TNF secreted at the site of inflammation may enhance the interaction of PMN with the extravascular environment through the CD11b/18 complex.

Bactericidal activities of lysozyme and aprotinin against gram-negative and gram-positive bacteria related to their basic character

Bactericidal properties of aprotinin, a proteinase inhibitor and possibly a defence molecule in bovine species, and of chicken egg white lysozyme, known as muramidase, were investigated. Incubation of various bacteria in the presence of either aprotinin or lysozyme showed that both proteins killed Gram-positive as well as Gram-negative bacteria without addition of complement or EDTA. Denaturation of the two proteins by dithiothreitol did not lead to loss of their bactericidal potency. Electron microscopic examination of Escherichia coli incubated either with lysozyme or aprotinin revealed that the bacterial cytoplasms gradually disintegrated. Both aprotinin and lysozyme were demonstrated within the affected cytoplasm by immunogold labelling. The results suggest that the bactericidal potency of lysozyme is not only due to muramidase activity but also to its cationic and hydrophobic properties. The bactericidal activity of aprotinin is probably also related to both these properties rather than to its activity as proteinase inhibitor.

Interaction and intracellular killing of Candida albicans blastospores by human polymorphonuclear leucocytes, monocytes and monocyte-derived macrophages in aerobic and anaerobic conditions

Polymorphonuclear leucocytes (PMN), monocytes and monocyte-derived macrophages were capable of interacting with opsonized C. albicans in both aerobic and anaerobic conditions. Superoxide anion release by these cells was inhibited in anaerobic conditions while lysozyme release and phagocytosis were equally efficient in both aerobic and anaerobic conditions. All cell types tested were capable of intracellular killing of C. albicans and this appeared to be maximum at 6 h for monocytes and macrophages and 24 h for PMN. Monocytes killed the lowest number of organisms, 1 x 10(6), and the killing was similar for aerobic and anaerobic conditions. In contrast, PMN and macrophages demonstrated greater killing of C. albicans in aerobic conditions compared with anaerobic conditions; PMN killed 1.9 x 10(6) organisms and macrophages 3 x 10(6) when incubated anaerobically. Inhibitors of oxygen metabolism decreased intracellular killing of C. albicans by macrophages and PMN in aerobic but not anaerobic conditions. The oxygen reaction products involved in the killing of C. albicans appeared to be different however: macrophage killing was decreased by superoxide anion and hydrogen peroxide inhibitors. PMN killing was decreased by superoxide anion, hydrogen peroxide, hypochlorous acid and hydroxyl radical inhibitors. The present study shows that although monocytes, macrophages and PMN function similarly in their interaction with C. albicans, they appear to use different oxygen reactive products for the intracellular killing of C. albicans.

Mouse hepatitis virus strain UAB infection enhances resistance to Salmonella typhimurium in mice by inducing suppression of bacterial growth

We have previously shown that intranasal infection of mice with mouse hepatitis virus (MHV) strain UAB (MHV-UAB) increases their resistance to Salmonella typhimurium injected intravenously 6 days later. To study how salmonella resistance was induced, BALB/cAnNCr mice were infected with salmonella strains carrying specific genetic alterations. One set of studies compared the effect of MHV infection on subsequent salmonella infections with AroA- (avirulent) and Aro+ (virulent) salmonellae. Unlike its effect on Aro+ salmonellae, MHV failed to reduce the number of AroA- salmonellae recovered from mice. Because AroA- S. typhimurium shows almost no growth in vivo, this failure indicated that the effect of MHV on salmonella resistance required growth of the infecting salmonellae. In other studies, the effect of MHV infection on both growth and killing were monitored simultaneously in mice with growing salmonellae carrying a single copy of the temperature-sensitive pHSG422 plasmid, which is unable to replicate in vivo. MHV infection reduced salmonella growth but caused no increase in salmonella killing. MHV infection of mice given wild-type salmonellae also resulted in no increase in salmonella killing 4 h after salmonella challenge. These studies demonstrate that MHV-UAB infection increases host resistance to salmonellae by enhancing suppression of bacterial growth instead of by increasing the amount of salmonella killing.

Effect of lysozyme on glucose fermentation, cytoplasmic pH, and intracellular potassium concentrations in Streptococcus mutans 10449

Several previous findings have suggested that the cationic nature of lysozyme is a major factor in its bactericidal activity. Since a number of cationic proteins or peptides have been reported to cause membrane damage in bacteria, we investigated the effect of lysozyme on glucose fermentation and intracellular pH and K+ in Streptococcus mutans under conditions in which lysis does not occur. Results showed that lysozyme and poly-D-lysine (PDL) cause inhibition of glucose fermentation at pH 5.5 in a dose-dependent manner. Human placental lysozyme and hen egg-white lysozyme exhibited similar inhibitory potency on glucose fermentation. Both lysozyme and PDL caused a marked acidification of the cytoplasm of S. mutans. However, when cytoplasmic pH was examined as a function of fermentation rate, the relationship was similar regardless of the presence or absence of lysozyme or PDL. Therefore, acidification of the cytoplasm appeared to not depend specifically on lysozyme or PDL. In contrast, the same relationship between the profound loss of intracellular K+, when fermenting cells were exposed to either lysozyme or PDL, and the fermentation rate was not exhibited in the controls. These results indicate that lysozyme and PDL specifically affected the ability of the cells to maintain intracellular K+. We concluded that lysozyme and PDL indeed perturb membrane function, perhaps in a selective manner. Furthermore, the similarity in action of lysozyme and the cationic homopolypeptide PDL supports the notion that the cationic property of lysozyme indeed plays a significant role in its antibacterial activity.

Inhibition of bactericidal and bacteriolytic activities of poly-D-lysine and lysozyme by chitotriose and ferric iron

In a previous report from this laboratory (N. J. Laible and G. R. Germaine, Infect. Immun. 48:720-728, 1985), evidence was presented to suggest that the bactericidal actions of both reduced (i.e., muramidase-inactive) human placental lysozyme and the synthetic cationic homopolymer poly-D-lysine involved the activation of a bacterial endogenous activity that was inhibitable by N,N',N"-triacetylchitotriose (chitotriose). In the present investigation however, we found that the bactericidal and bacteriolytic action of poly-D-lysine could be prevented only by some commercially available chitotriose preparations and not by others. Analysis by physical and chemical methods failed to distinguish protective chitotriose (CTa) and nonprotective chitotriose (CTi) preparations. CTi and CTa preparations displayed equal capacities to competitively inhibit binding of [3H]chitotriose by immobilized lysozyme and were indistinguishable in their abilities to block the lytic activity of lysozyme against Micrococcus lysodeikticus cells. Elemental analysis revealed significantly higher levels of phosphorus, calcium, iron, sodium, manganese, and copper in CTa. Removal of metals from CTa by chelate chromatography completely abolished the poly-D-lysine-protective capacity. Of the metals detected, only ferric iron (5 to 10 microM) mimicked the protective action of CTa. A Fe(III) concentration of 50 microM was required to inhibit lysozyme (5 micrograms/ml). Both Fe(III) and CTa (but not CTi) quantitatively blocked the labeling of poly-D-lysine by fluorescamine, suggesting that the primary amino groups of the lysine residues participate in iron binding. Thus, it appears that the poly-D-lysine-protective capacity of certain chitotriose preparations was due not to the chitotriose itself but to contaminating metal ions which interact directly with the polycationic agent. In contrast, Fe(III) cannot account for inhibition of either the bactericidal or bacteriolytic activity of lysozyme by chitotriose.

Antibiotic proteins of human polymorphonuclear leukocytes

Nine polypeptide peaks with antibiotic activity were resolved from human polymorphonuclear leukocyte azurophil granule membranes. All but 1 of the 12 constituent polypeptides were identified by N-terminal sequence analysis. Near quantitative recovery of protein and activity permitted an assessment of the contribution of each species to the overall respiratory-burst-independent antimicrobial capacity of the cell. Three uncharacterized polypeptides were discovered, including two broad-spectrum antibiotics. One of these, a defensin that we have designated human neutrophil antimicrobial peptide 4, was more potent than previously described defensins but represented less than 1% of the total protein. The other, named azurocidin, was abundant and comparable to bactericidal permeability-increasing factor in its contribution to the killing of Escherichia coli.

Isolation and characterization of human defensin cDNA clones

Four clones that encode defensins, a group of microbicidal and cytotoxic peptides made by neutrophils, were isolated from an HL-60 human promyelocytic leukemia cDNA library. Analysis of these clones indicated that the defensins are made as precursor proteins, which must be cleaved to yield the mature peptides. Defensin mRNA was detected in normal bone marrow cells, but not in normal peripheral blood leukocytes. Defensin transcripts were also found in the peripheral leukocytes of some leukemia patients and in some lung and intestine tissues. Defensin mRNA content was augmented by treatment of HL-60 cells with dimethyl sulfoxide. These results define important aspects of the mechanism of synthesis and the tissue-specific expression of a major group of neutrophil granule proteins.

Microbicidal/cytotoxic proteins of neutrophils are deficient in two disorders: Chediak-Higashi syndrome and "specific" granule deficiency

Although several genetic defects are known to impair oxidative microbicidal/cytotoxic mechanisms in human PMN, no deficiencies of PMN granule components that mediate oxygen-independent microbicidal activity have yet been reported. We analyzed PMN from patients with various granulocyte disorders for their content of two azurophil granule constituents, defensins and cathepsin G, that exert microbicidal/cytotoxic activity in vitro, and one component, elastase, that has ancillary microbicidal/cytotoxic activity. PMN from two (of two) patients with specific granule deficiency (SGD) displayed an almost complete deficiency of defensins, which in normal cells constitute greater than 30% of the protein content of azurophil granules. The SGD PMN contained normal or mildly decreased amounts of cathepsin G and elastase. Conversely, the PMN of three (of three) patients with Chediak-Higashi syndrome (CHS) substantially lacked cathepsin G and elastase, but their defensin content was normal or mildly decreased. Both CHS and SGD patients suffer from frequent and severe bacterial infections, and CHS patients frequently develop an atypical lymphoproliferative syndrome. The profound deficiency of PMN components with microbicidal/cytotoxic activity in SGD and CHS may contribute to the clinical manifestations of these disorders.

Modulation of the in vitro candidacidal activity of human neutrophil defensins by target cell metabolism and divalent cations

We tested the in vitro susceptibility of Candida albicans to three defensins from human neutrophilic granulocytes (HNP-1, 2, and 3), a homologous defensin from rabbit leukocytes (NP-1), and four unrelated cationic peptides. Although the primary amino acid sequences of HNP-1, 2, and 3 are identical except for a single amino-terminal amino acid alteration, HNP-1 and HNP-2 killed C. albicans but HNP-3 did not. C. albicans blastoconidia were protected from HNP-1 when incubations were performed in the absence of oxygen or in the presence of inhibitors that blocked both of its mitochondrial respiratory pathways. Neither anaerobiosis nor mitochondrial inhibitors substantially protected C. albicans exposed to NP-1, poly-L-arginine, poly-L-lysine, or mellitin. Human neutrophilic granulocyte defensin-mediated candidacidal activity was inhibited by both Mg2+ and Ca2+, and was unaffected by Fe2+. In contrast, Fe2+ inhibited the candidacidal activity of NP-1 and all of the model cationic peptides, whereas Mg2+ inhibited none of them. These data demonstrate that susceptibility of C. albicans to human defensins depends both on the ionic environment and on the metabolic state of the target cell. The latter finding suggests that leukocyte-mediated microbicidal mechanisms may manifest oxygen dependence for reasons unrelated to the production of reactive oxygen intermediates by the leukocyte.

Trypanosoma cruzi: a specific surface marker for the amastigote form

Among the known life cycle stages of Trypanosoma cruzi only the amastigote form bound lactoferrin (LF), a glycoprotein produced by neutrophils. This capacity was readily demonstrable by indirect immunofluorescence in amastigotes derived from mice, a mammalian cell culture, or grown in an axenic medium. No LF binding was detectable on trypomastigotes from blood or mammalian cells, insect-derived metacyclics or epimastigotes, or on epimastigotes grown in Warren's medium. Serum levels of LF were increased in mice acutely infected with T. cruzi, and amastigotes from the spleens of these animals were found to have the glycoprotein on their surface. The amastigote LF receptor may have biological significance in parasite-host interaction since mononuclear phagocytes also express a LF receptor, and treatment of these cells with LF has been shown to increase their capacities to take up and kill T. cruzi amastigotes in vitro. The LF receptor is the first marker for T. cruzi amastigotes for which a naturally occurring ligand has been described.

Influence of rosmarinic acid on opsonization and intracellular killing of Escherichia coli and Staphylococcus aureus by porcine and human polymorphonuclear leucocytes

The influence of rosmarinic acid on the function of porcine and human polymorphonuclear leucocytes was tested. Rosmarinic acid inhibited the chemiluminescence of PMNL, induced by preopsonized Zymosan or phorbol myristate acetate. The killing of Escherichia coli was inhibited by rosmarinic acid at a concentration of 2 mM, but not that of Staphylococcus aureus. The inhibition of the killing was due to an impaired opsonization, caused by an adverse influence of rosmarinic acid on complement activation. Direct effects of rosmarinic acid on the killing mechanisms of PMNL were not observed.

Nonoxidative antimicrobial effects of human polymorphonuclear leukocyte granule proteins on Chlamydia spp. in vitro

Proteins from isolated granules of human polymorphonuclear leukocytes were assessed for their nonoxidative microbicidal effect on chlamydiae by two different methods: a radioisotope assay for elementary body integrity and a biological assay for inclusion development. Crude granule extract, which consisted of a mixture of all granule proteins, caused a 20 to 30% decrease in infectivity and a 52% decrease in infectivity when incubated with Chlamydia psittaci CAL-10 and Chlamydia trachomatis serovar E, respectively. To define more specifically the components that were damaging to chlamydiae, crude granule extract was subjected to Sephadex G-75 column chromatography and isolated granule fractions were obtained. Only fractions containing lysozyme as the major component consistently caused reductions in infectivity of C. trachomatis elementary bodies. In contrast, fractions collected after the lysozyme fraction, containing proteins with molecular masses of 13,000 daltons or less, had detrimental effects on C. psittaci infectivity. Additional experiments using highly purified human polymorphonuclear leukocyte lysozyme confirmed its infectivity-reducing action upon C. trachomatis but not upon C. psittaci.

Characterization of a protein from normal human polymorphonuclear leukocytes with bactericidal activity against Pseudomonas aeruginosa

Purification of a bactericidal protein (BP) from the cytoplasmic granules of normal human polymorphonuclear leukocytes (PMN) with activity against Pseudomonas aeruginosa is described. Bactericidal activity from acid extracts of a mixed granule population was purified 175-fold by a two-step chromatographic procedure. The first step, dye-ligand affinity chromatography with Matrex-Gel Orange A, was followed by cation-exchange chromatography with Bio-Rex 70 resin, and this combination routinely gave a yield near 80%. Only one peak of bactericidal activity against P. aeruginosa type I was found after each chromatographic step. Characterization of BP showed a single band with an apparent molecular weight of 55,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Purified BP was most active against the six strains of P. aeruginosa tested and against Escherichia coli B (a deep rough mutant). Purified BP killed 5 X 10(6) CFU of P. aeruginosa type I per ml at a concentration of 60 to 80 ng/ml. Proteus mirabilis and Staphylococcus aureus were both resistant to the bactericidal activity of BP. BP was shown to be glycosylated by periodic acid staining after gel electrophoresis and to have an isoelectric point near 7.5 by chromatofocusing. The amino acid composition of BP is presented.

Bactericidal-activities of human polymorphonuclear leukocyte proteins against Escherichia coli O111:B4 coated with C5 or C8

The postnuclear supernatant of disrupted polymorphonuclear leukocytes exhibited bactericidal activity on Escherichia coli O111:B4 coated with immunoglobulin M antibodies and C5 or C8 but not on C3- or C7-coated bacteria. To characterize this antimicrobial activity further, granules obtained from the postnuclear supernatant were extracted with sodium acetate (pH 4) and the soluble extract was subsequently fractionated through carboxymethyl cellulose and Sephacryl S-200. Over 90% of the activity present in the starting material was recovered in the soluble granule extract. Kinetic and dose-response analyses of the bacterial activity of the polymorphonuclear leukocyte extract on BAC1-5 and BAC1-8 revealed different susceptibilities to killing of these two bacterial intermediates; they also differed for their susceptibilities to killing at 37 degrees C and at room temperature. The suggestion raised by these data, that BAC1-5 and BAC1-8 could be killed by different bactericidal factors, was confirmed by the findings that separate fractions of the soluble granule extract obtained by carboxymethyl cellulose and Sephacryl S-200 chromatography exhibited specific activity on either BAC1-5 or BAC1-8, whereas other fractions were active on both intermediates.

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.

Neisseria gonorrhoeae survive intraleukocytic oxygen-independent antimicrobial capacities of anaerobic and aerobic granulocytes in the presence of pyocin lethal for extracellular gonococci

The resistance of a piliated, transparent variant of Neisseria gonorrhoeae FA19 to intraleukocytic killing by human polymorphonuclear neutrophils (PMN) was examined. In both aerobic and anaerobic PMN monolayers, approximately 2% of the intracellular gonococci survived for as long as 165 min. Anaerobic PMN were as effective as aerobic PMN in the intracellular killing of gonococci. Hence, O2-independent antimicrobial systems of PMN performed a significant role in the intraleukocytic killing of gonococci were intracellular was supported by the elimination of extracellular bacteria by the addition of pyocin 103 and confirmed by the fluorescent antibody staining of intact gonococci after the PMN were permeabilized to antibody with a Formalin-acetone treatment of PMN monolayers. Our data indicate that while the majority of ingested gonococci are killed by O2-independent antimicrobial systems, a small number (about 2%), survive even when care is taken to eliminate extracellular bacteria.

Physiological effects of a bactericidal protein from human polymorphonuclear leukocytes on Pseudomonas aeruginosa

The physiological changes seen in Pseudomonas aeruginosa after exposure to a bactericidal protein (BP) from the granules of human polymorphonuclear leukocytes were studied. It was demonstrated, using radiolabeled proline or leucine, that both the rate of cellular uptake and amino acid incorporation into trichloroacetic acid-insoluble material were markedly decreased immediately after exposure to BP. The rate of O2 consumption by P. aeruginosa was decreased immediately after exposure to BP and continued to decline exponentially until it ceased completely 30 min after exposure to BP. In the presence of 30 mM CaCl2 or MgCl2, bacteria were protected from death due to BP and respiration rates were unaffected. The cellular ATP pool of P. aeruginosa remained constant for up to 2 h after exposure to BP. Membrane depolarization was measured by the influx of the lipophilic anion thiocyanate. It was shown that the cytoplasmic membrane of P. aeruginosa was partially depolarized after exposure to BP. Purified BP killed 95% of 5 X 10(6) CFU of P. aeruginosa at a concentration of 60 to 100 ng of protein per ml. Although the concentration of bacteria and BP varied with each type of experiment, the BP/bacteria ratio required to cause a 95 to 99% loss in viability remained constant. We propose that cytoplasmic membrane depolarization is the biochemical lesion responsible for the other physiological changes seen and ultimately for the death of P. aeruginosa induced by BP.

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.