Bactericidal activity of specific and azurophil granules from human neutrophils: studies with outer-membrane mutants of Salmonella typhimurium LT-2

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.

Pseudomonas aeruginosa variants isolated from patients with cystic fibrosis are killed by a bactericidal protein from human polymorphonuclear leukocytes

The susceptibility of paired mucoid and nonmucoid variants of Pseudomonas aeruginosa isolated from 13 patients with cystic fibrosis (CF) to killing by a 55,000-Da bactericidal protein (BP55) from human polymorphonuclear leukocytes was studied. Mucoid and nonmucoid variants were equally sensitive to killing by BP55 at both pH 5.6 and pH 7.2. Eleven of the isolates were resistant to the bactericidal activity of 10% normal human serum but were as sensitive as the serum-sensitive isolates to BP55. Similarly, the 15 isolates with lipopolysaccharides (LPS) containing O-polysaccharide side chains (smooth LPS) were as sensitive to BP55 as those isolates with rough LPS.P. aeruginosa isolates from patients in poor clinical condition were more likely to have LPS of the smooth type and to be resistant to killing by 10% human serum than the isolates from patients in good clinical condition. We have concluded that the susceptibility of the P. aeruginosa isolates from patients with CF to killing by BP55 does not correlate with mucoid or nonmucoid variations, with the presence or absence of smooth LPS, or with the sensitivity or resistance to killing by normal human serum.

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.

Defensins

Defensins are a family of small, variably cationic proteins which are highly abundant in the granules of mammalian phagocytes. Three defensins, HNP-1, 2, and 3, comprise 30-50% of total protein in azurophil granules of human neutrophils. Some defensins are broadly antimicrobial, antiviral and cytotoxic, while others are chemotactic, opsonic, or may modulate hormonal responses. The defensin molecule typically consists of 29-34 amino acids with a conserved pattern of disulfide linkage among its 6 cysteines. The three-dimensional fold of defensins forms a highly amphiphilic molecule. Microbicidal and cytotoxic properties of defensins are most likely a consequence of their ability to insert into biological membranes and to generate pores. Defensins are synthesized by phagocytes or their precursors as a 94-95 amino acid charge-neutralized preprodefensin, an arrangement which may avoid cytotoxic injury to the phagocyte. Although defensins were recognized only recently, the existence of homologs in certain invertebrates suggests that they are ancestral components of the host defense system.

Bovine uterine defense mechanisms: a review

Bovine uterine defense mechanisms during physiological and pathological conditions have been reviewed in this article. The initial uterine defense against bacterial infection is phagocytosis by uterine leucocytes (mainly neutrophils). The reported literature showed that very little work has been done on immunoglobulins and their role in the bovine uterine defense mechanisms; however, some investigators have found a positive correlation between gamma-globulin and the development of uterine infection after calving. Many explanations exist for the difference in susceptibility of the uterus to infection during the different phases of estrous cycle; however, most of the reports agreed that the uterine defense mechanism is inadequate during diestrus. The abnormal puerperium effects uterine defense mechanisms adversely and prolongs the time to complete uterine involution. Future treatment may utilise natural antimicrobial substances such as proteins or peptides derived from PMN, chemoattractant substances such as E. coli lipopolysaccharide or a bacteria-free filtrate of streptococci. Specific hyperimmunserum could also be used as opsonin for refractory cases of uterine bacterial infections.

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.

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.

Extracellular release of antimicrobial defensins by human polymorphonuclear leukocytes

Human polymorphonuclear leukocytes (PMN) contain three antimicrobial and cytotoxic peptides which belong to a family of mammalian granulocyte peptides named defensins. To determine their potential availability for extracellular microbicidal or cytotoxic events, we quantified the extracellular release of defensins after stimulation of human PMN with phorbol myristate acetate and opsonized zymosan. As determined by enzyme immunoassay and confirmed by polyacrylamide gel electrophoresis and densitometry, 10(6) human PMN contained 4 to 5 micrograms of defensins. After stimulation with a high concentration of phorbol myristate acetate (1 microgram/ml), about 8% of PMN defensins were found in the media. Release of defensins correlated best with the release of azurophil granule marker beta-glucuronidase or elastase and poorly with the release of either the specific granule marker lactoferrin or cytoplasmic lactate dehydrogenase. Phagocytosis of opsonized zymosan resulted in the extracellular release of less than 3% of PMN defensins. The factors responsible for less release of defensins into media relative to the release of other azurophil granule proteins may include heterogeneity of azurophil granules and the affinity of defensins for cellular surfaces and opsonized particles. In vivo, defensins are most likely to reach effective microbicidal or cytotoxic concentrations in PMN-rich exudates (pus), in confined environments of the phagolysosomes, or in intercellular clefts between PMN and their targets.

Subcellular location and properties of bactericidal factors from human neutrophils

We examined the subcellular location of bactericidal factors (BF) in human neutrophils, using an efficient fractionation scheme. Nitrogen bomb cavitates of DIFP-treated PMN were centrifuged through discontinuous Percoll gradients, each fraction extracted with 0.05 M glycine, pH 2.0, and tested for the killing of Escherichia coli. greater than 90% of BF coisolated with the azurophil granules. After lysis of azurophils, 98% of azurophil-derived BF (ADBF) sedimented with the membrane. ADBF activity was solubilized from azurophil membrane with either acid or nonionic detergent (Triton X-100, Triton X-114). Bactericidal activity was linear with respect to protein concentration over the range 0.3-30 micrograms/ml. 0.1-0.3 microgram/ml ADBF killed 10(5) E. coli within 30 min at 37 degrees C. At 1.4 micrograms/ml, 50% of 2 X 10(5) bacteria were killed within 5 min. ADBF was effective between pH 5-8, with peak activity at pH 5.5. Glucose (20 mM), EDTA (1-25 mM), and physiologic concentrations of NaCl or KCl had little or no inhibitory effect on ADBF. ADBF killed both Gram-positive and Gram-negative virulent clinical isolates, including listeria, staphylococci, beta-hemolytic streptococci, and Pseudomonas aeruginosa. Thus, under these conditions of cell disruption, fractionation, extraction, and assay, almost all BF in human PMN appeared to be localized to the membrane of azurophilic granules as a highly potent, broad-spectrum, rapidly acting protein(s) effective in physiologic medium. Some of these properties appear to distinguish ADBF from previously described PMN bactericidal proteins.

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.

Lysozyme-mediated aggregation and lysis of the periodontal microorganism Capnocytophaga gingivalis 2010

The ability of lysozyme to aggregate and lyse the gram-negative capnophilic periodontal microorganism Capnocytophaga gingivalis 2010 was monitored optically at 540 nm. Both hen egg white and chromatographically purified human lysozymes had significant but similar aggregation potentials for both logarithmic- and stationary-phase bacteria. In general, an increase in enzyme concentration resulted in a graded increase in both the initial and maximum changes in turbidity which occurred during the reaction period. The greatest change in turbidity occurred within the initial minutes of interaction of lysozyme and the cells, and the extent of aggregation paralleled a rapid depletion of lysozyme by the suspensions during the first minute of its incubation with the bacteria. Interestingly, the muramidase inhibitors N-acetyl-D-glucosamine and histamine did not block aggregation, whereas maleylation of lysozyme completely inhibited its aggregating ability. Demaleylation, however, restored aggregation activity comparable to the native enzyme, indicating that maleylated lysozyme retained its integrity and that aggregation was primarily dependent on charge. The addition of up to physiological concentrations of NaHCO3 and NaCl to cell aggregates resulted in varying degrees of deaggregation and lysis. Surprisingly, ultrastructural analysis of lysozyme-treated cells revealed morphological changes with or without the addition of salt. Damage appeared to occur at the blunted polar end of the cells where there was a large spherical outpouching bordered by a damaged cell envelope. Damaged cells uniformly contained dense granular cytoplasmic debris. In effect, the cationic enzyme lysed C. gingivalis 2010, which was not apparent in the spectrophotometric assay. The paradoxical finding that during bacterial aggregation there was lysis may be of significance to the further elucidation of lysozyme's antibacterial role in the gingival sulcus.

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.

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.

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.

In vivo degradation of gonococcal outer membrane proteins within human leukocyte phagolysosomes

We previously showed in vitro hydrolysis of outer membrane proteins by lysosomal proteases and purified elastase. In this study we examined the in vivo relevance of the previous studies. Outer membranes were obtained from Neisseria gonorrhoeae type 3 (strain GC7) by LiCl2 extraction. Some preparations were labeled with 125I. Phagocytizable particles were prepared by coating latex beads with outer membranes, and polymorphonuclear leukocytes were allowed to phagocytize serum-opsonized particles. After homogenization of neutrophils, phagolysosomes were recovered by flotation through sucrose. Phagolysosomes were prepared for slab gel electrophoresis immediately or incubated further at 37 degrees C to allow continued degradation of outer membrane proteins. The principal protein (protein I) and minor proteins (proteins II) of outer membranes were hydrolyzed in whole neutrophils and in isolated phagolysosomes. Proteins II were more susceptible to hydrolysis than protein I. Hydrolytic products formed were nearly identical in vivo and in vitro. We also radiolabeled the surface-exposed proteins of live gonococci. Degradation of outer membrane proteins on the intact bacteria within neutrophil and monocyte phagolysosomes was shown. This indicates that our earlier in vitro model is relevant to in vivo hydrolysis of gonococcal outer membrane proteins.

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.

Histopathological study of protective immunity against murine salmonellosis induced by killed vaccine

Swiss-Webster mice were vaccinated with heat-killed salmonellae and then were infected with virulent Salmonella typhimurium. Only 1 of the 18 vaccinated mice died from a challenge of 10(4) X the 50% lethal dose, and about 70% of them survived a challenge of 10(5) X the 50% lethal dose. Histopathological examinations of the lesions developed in these vaccinated mice showed that they followed the characteristic features of a primary lesion in murine salmonellosis. There was an early necrosis with infiltration of polymorphonuclear leukocytes and abscess formation within the first 6 to 7 days after infection. However, these abscesses remained small and discrete. By days 7 to 10, the lesions began to transform into granulomas, first with the appearance of peripheral mononuclear cells and then by the replacement of polymorphs. By the third week of the infection, minute and discrete granulomas were seen scattered in the spleen, liver, and lymph nodes. Beyond this stage, healing and tissue regeneration followed. Thus, the characteristics of infectious lesions developed in mice vaccinated with heat-killed salmonellae are distinctly different from those developed in mice protected by the avirulent vaccine.

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.

Killing of gram-negative bacteria by polymorphonuclear leukocytes: role of an O2-independent bactericidal system

Previous studies have suggested that a cationic bactericidal/permeability-increasing protein (BPI) present in both rabbit and human polymorphonuclear leukocytes is the principal O2-independent bactericidal agent of these cells toward several strains of Escherichia coli and Salmonella typhimurium (1978. J. Biol. Chem. 253: 2664--2672; 1979. J. Biol. Chem. 254: 11000--11009). To further evaluate the possible role of this protein in the killing of gram-negative bacteria by polymorphonuclear leukocytes, we have measured the bactericidal activity of intact rabbit peritoneal exudate leukocytes under aerobic or anaerobic conditions and of intact human leukocytes from a patient with chronic granulomatous disease. Anaerobic conditions were created by flushing the cells under a nitrogen stream. Effective removal of oxygen was demonstrated by the inability of nitrogen-flushed leukocytes to mount a respiratory burst (measured as increased conversion of 1-[14C]glucose leads to 14CO2 or by superoxide production) during bacterial ingestion. At a bacteria/leukocyte ratio of 10:1, killing of gram-positive, BPI-resistant, Staphylococcus epidermidis is markedly impaired in the absence of oxygen (76.4 +/- 3.3% killing in room air, 29.2 +/- 8.2% killing in nitrogen). Essentially all increased bacterial survival is intracellular. In contrast, both a nonopsonized rough strain (MR-10) and an opsonized smooth strain (MS) of S. typhimurium 395 are killed equally well in room air and nitrogen. A maximum of 70--80 MR-10 and 30--40 MS are killed per leukocyte either in the presence or absence of oxygen. There is no intracellular bacterial survival in either condition indicating that intracellular O2-independent bactericidal system(s) of rabbit polymorphonuclear leukocytes can at least match the leukocyte's ingestive capacity. Whole homogenates and crude acid extracts manifest similar bactericidal capacity toward S. typhimurium 395. This activity can be accounted for by the BPI content of these cell fractions and is virtually eliminated by immune (anti-BPI), but not by preimmune goat IgG-rich fractions. Opsonization of smooth MS, required for bacterial killing by intact leukocytes, does not alter bacterial sensitivity to BPI in crude or purified form. Leukocytes of a patient with chronic granulomatous disease killed ingested S. typhimurium 396 MS nearly as well as did normal leukocytes. The bactericidal activity toward E. coli (J5) of crude acid extracts of the CGD and normal human leukocytes was virtually the same and was nearly completely inhibited by anti-BPI IgG-rich fractions, but not by preimmune IgG-rich fractions. These findings suggest that the killing of gram-negative bacteria such as S. typhimurium by intact polymorphonuclear leukocytes may also be attributed to the action of BPI.

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.

Bactericidal activity of fractionated granule contents from human polymorphonuclear leukocytes: role of bacterial membrane lipid

Granule contents from human polymorphonuclear leukocytes were prepared by extraction with 0.2 M acetate, pH 4. A buffer extract fraction (peak D) obtained by Sephadex G-100 column chromatography demonstrated distinct antimicrobial activity toward Acinetobacte sp. independent of added H2O2 or Cl-. The protein of this fraction had an apparent molecular weight of 9,000 and demonstrated time and dose dependence that was more active against stationary-growth cells than mid-log-phase cells. The bactericidal activity of the fraction was most active at 37 degrees C, with only slight activity demonstrated at 22 degrees C and no activity at 4 degrees C. Boiling the granule fraction for 30 min did not affect the antimicrobial activity. However, pronase or trypsin pretreatment of the peak D fraction reduced its antimicrobial activity. When the membrane lipid composition of Acinetobacter sp. was altered by growth on specific n-alkane carbon sources, the susceptibility to the granule fraction was also altered. Resistance to the activity of the granule fraction increased as the carbon chain length of the growth substrate increased. Liposomes formed from Acinetobacter sp. lipid extracts and containing glucose were made leaky with the addition of the granule fraction (boiled and not boiled), suggesting a membrane-disruptive activity of the granule protein against Acinetobacter sp. membranes.

Inhibition or killing of an intracellular pathogen by activated macrophages is abrogated by TLCK or aminophylline

Agents that are known to inhibit certain metabolic pathways or cell functions were evaluated to determine their effects on the capacity of activated macrophages to inhibit or kill obligate intracellular pathogens. Tosyllysine chloromethyl ketone (TLCK) and aminophylline abrogate inhibition or killing of Toxoplasma gondii by activated macrophages.

Killing of Neisseria gonorrhoeae by human polymorphonuclear neutrophil granule extracts

Neisseria gonorrhoeae was grown in vitro (on agar and in broth) and in vivo (in 10-day chicken embryos) and tested for its sensitivity to the bactericidal action of human neutrophil granule extracts. Under all conditions studied, type 1 and type 4 N. gonorrhoeae were killed equally well by dialyzed extracts of neutrophil granules (containing both azurophil and specific granule contents) and by the myeloperoxidase-Cl- - H2O2 bactericidal system. However, sensitivity to the bactericidal activity of granule extracts depended upon growth conditions and growth phase. Log-phase, egg-grown gonococci were the most sensitive; they were killed 100% by 250 to 300 micrograms of granule extract (60 min, 37 degrees C) per ml. N. gonorrhoeae grown on agar for 20 h (to stationary phase) were the least sensitive, being killed only 80 to 90% with 500 micrograms of granule extract per ml. Thus, susceptibility to granule extract of gonococci grown under the four conditions studied in this report decreased in the order: log phase, egg grown; log phase, broth grown; stationary phase, egg grown; and stationary phase, agar grown. Killing was time and temperature dependent; little killing occurred when incubations were done at 10 degrees C. Boiled granule extract had only minimal effects on N. gonorrhoeae viability. Addition of catalase (500 U/ml) to the granule extract bactericidal system did not protect; however, the same concentration of catalase completely inhibited the bactericidal activity of the myeloperoxidase-Cl- - H2O2 system.

Bactericidal activity of fractionated granule contents from human polymorphonuclear leukocytes: antagonism of granule cationic proteins by lipopolysaccharide

Granule extracts from human polymorphonuclear leukocytes (PMN) were prepared with 0.2 M (pH 4.0) acetate. A fraction (valley AB) with distinctive bactericidal activity against cell wall mutants of Salmonella typhimurium LT-2 was obtained after fractionation of the granule extracts by Sephadex G-100 column chromatography. The smooth parent LT-2 strain was less sensitive to the bactericidal action. Susceptibility of the rough mutants to bactericidal action increased as sugar residues decreased in the lipopolysaccharide (LPS) (Re greater than Rd2 greater than Rd1 greater than Rc greater than Ra). Cationic protein(s) responsible for bactericidal activity could be selectively removed from the fraction by absorption with whole LT-2 cells or purified LPS. Loss of cationic protein species was confirmed by cationic polyacrylamide gel electrophoresis. Purified LPS from LT-2 or the deep rough mutant TA2168 inhibited the antimicrobial activity of the killing fraction in in vitro assays. A minor protein species (vAB1) from the valley AB fraction had an apparent molecular weight of 36,000 to 37,000 and represented a major bactericidal activity of the fraction. Small amounts of the isolated vAB1 protein were bactericidal for the smooth parent LT-2 strain.

Bactericidal activity of fractionated granule contents from human polymorphonuclear leukocytes

Proteins from human polymorphonuclear leukocyte granules were extracted with 0.2 M acetate, pH 4.0, and fractionated by Sephadex G-100 column chromatography. The fractions demonstrated selective bactericidal action against a deep rough cell wall mutant of Escherichia coli O111:B4 with rough lipopolysacharide and cell wall mutants of Salmonella typhimurium LT-2 with lipoplysacharide of Ra, Rc, Rd1, Rd2, and Re types. Smooth parent strains were most resistant to the bactericidal action. Fractions with greatest activity for the mutants were from valley regions (regions of low protein concentration) between three high protein peaks comprising myeloperoxidase, protease, and lysozyme, respectively. Susceptibility of the mutants to bactericidal action increased as sugar residues decreased in lipopolysaccharide. Gram-positive bacteria were susceptible to different fractions than were the gram-negative bacteria.

Inhibition of specific amino acid uptake in Candida albicans by lysosomal extracts from rabbit alveolar macrophages

Lysosomal-rich fractions, obtained from normal rabbit alveolar macrophages, were extracted and tested for their effects on Candida albicans. The uptake and incorporation of various compounds (amino acids, uridine, 2-deoxy-D-glucose, and Rb+) by C. albicans were measured in the presence and absence of extract. These studies demonstrated that the extract had a specific effect on the uptake of certain amino acids by C. albicans. Of the amino acids tested, the uptake of methionine valine, lysine, phenylalanine, and leucine was drastically reduced in the presence of extract, whereas proline and glutamic acid uptake was unaffected. Those amino acids whose uptake was inhibited have been shown to be transported in other yeasts by a general amino acid permease. The existence of a general amino acid permease in C. albicans is compatible with our data. Additionally, the extract had no effect on the uptake of uridine, 2-deoxy-D-glucose, and Rb+. Leakage of 86Rb by C. albicans was detected in the presence of the extract. Viability of Candida, as measured by colony-forming ability, decreased after a 16-h incubation of C. albicans with the extract.