Comparison of the mitochondrial endonucleases from Neurospora crassa and Saccharomyces cerevisiae

The endonucleases from Neurospora crassa and Saccharomyces cerevisiae are not closely related antigenically. They also differ with respect to their activity at pH 8, their degree of hydrophobicity, and their sensitivity to elevated temperatures. However, the two nucleases have similar specific activities, are inhibited by EDTA, and have nearly identical substrate specificities. Since the enzymes also have the same mode of action and intracellular location, these similarities may indicate that they have the same physiological role despite their structural differences.

Ca2+-dependent and Ca2+-independent phagocytosis in human neutrophils

The phagocytic function of neutrophils is a crucial element in host defence against invading microorganisms. Two main specific receptor-mediated mechanisms operate in the phagocyte plasma membrane, one recognizing the C3b/bi fragment of complement and the other the Fc domain of immunoglobulin G (ref. 1). There is evidence that phagocytosis mediated by these receptors differs in the number and nature of the intracellular signals generated. However, the mechanisms by which receptor binding is transduced into a signal that generates the formation of the phagocyte pseudopod is not known, although extensive biochemical evidence has allowed the postulate that calcium ion gradients in the peripheral cytoplasm, by interacting with calcium-sensitive contractile proteins, initiate the process of engulfment. Using the high-affinity fluorescent calcium indicator quin2 both to measure and to buffer intracellular calcium ([Ca2+]i), we show here that in human neutrophils two mechanisms of phagocytosis coexist: a [Ca2+]i-dependent and modulated phagocytosis, triggered by activation of the Fc receptor, and a [Ca2+]i-independent mechanism triggered by the activation of the C3b/bl receptors.

Deposition of C3b and iC3b onto particulate activators of the human complement system. Quantitation with monoclonal antibodies to human C3

Monoclonal antibodies were used to determine the number and molecular form of C3 bound to particulate activators of the complement (C) system by human serum. Sheep erythrocytes (E) coated with IgM (EIgM) and IgG (EIgG) were used to study activation of the classical pathway (CP). Yeast (Y), rabbit erythrocytes (ER), and five species of bacteria (Escherichia coli, Staphylococcus aureus, Streptococcus pneumoniae type 3, Streptococcus pyogenes, and Hemophilus influenzae type b) were used to study activation of the alternative pathway (AP). The deposition of C3b onto EIgM and EIgG incubated in C7-deficient human serum was dependent on the serum concentration. At all serum concentrations tested, there was complete conversion of C3b to iC3b. Kinetic analysis of C3b deposition and conversion to iC3b indicated that these events occurred almost simultaneously; the reaction was completed by 15 min. The deposition of C3 onto the AP activators ER and Y was also dependent on serum concentration, and ER, but not Y, required the presence of Mg-EGTA and thus the activation of only the AP. C3b deposition and conversion to iC3b on Y was complete in 15 min, with 82% of bound C3 converted to iC3b. For ER, maximum C3 deposition required 30 min in both the presence and absence of Mg-EGTA. However, after 1 h of incubation, 74% of bound C2 was iC3b in the absence of Mg-EGTA, compared with only 52% in the presence of Mg-EGTA. Thus, even on AP activators, a large portion of C3b may be converted to iC3b, and this conversion is probably controlled by elements on the particle's surface. Studies with the five species of bacteria yielded similar results. Approximately 3-5 X 10(4) molecules of C3 were bound per microorganism, with opsonization being completed in 30 min. Remarkably, only 16-28% of bound C3 was in the form of iC3b, even after 2 h of incubation. The presence or absence of Mg-EGTA, or the addition of purified CR1 to the reaction mixture, did not significantly effect the ratio of C3b to iC3b. Finally, SDS-PAGE and autoradiography of particle-bound 125I-C3 fragments confirmed that there was no conversion of iC3b to C3d,g or C3d. The data obtained about the opsonization of bacteria suggest that the predominant form of C3 that is encountered by inflammatory phagocytes may be C3b.

Cross-reacting human and rabbit antibodies to antigens of Histoplasma capsulatum, Candida albicans, and Saccharomyces cerevisiae

Using Western blots of electrophoretically separated antigens, we show that human antibodies react most frequently to antigens shared by three fungi (Histoplasma capsulatum, Candida albicans, and Saccharomyces cerevisiae). Reactivity to antigens specific for individual fungi was relatively uncommon. The pattern of reactivity could not distinguish infected patients from uninfected controls. Rabbits immunized with extracts of each fungus also produced antibodies to cross-reactive or shared antigens of the other two fungi. Furthermore, preimmune sera showed similar but lower reactivity with the same fungal antigens. We believe that the preimmunization antibodies, which probably resulted from earlier fungal colonization or inapparent infections, predisposed the immune responses elicited by the vaccinations. A similar mechanism likely explains the results with human sera.

Isolation of yeast ribosomal proteins L3 and L2 for immunological studies

We report on a rapid method for the isolation and purification of the yeast ribosomal proteins L3 and L2 using a simple instrumentation. Preparative dodecyl sulfate polyacrylamide gel electrophoresis was applied to the separation of cytoplasmatic ribosomal proteins of the large subunit from the yeast Saccharomyces cerevisiae. The polypeptides were removed from gel slices by electrophoretic elution. Subsequent analytical electrophoresis showed groups of proteins in all but two fractions. The latter were further analysed by a two-dimensional gel electrophoresis system which disclosed the purity of two polypeptides. They were identified as L3 and L2. Their molecular masses were 51.5 and 44 kDa as estimated from the gels. A possible application to the isolation of other yeast ribosomal proteins is discussed. An antiserum against the polypeptide L3 was raised in a rabbit. Applying an enzyme-linked immunosorbent assay (ELISA) we were able to determine the relative antibody concentration. Its specificity was demonstrated by immunoblotting.

Antigens of Aspergillus fumigatus. III. Comparative immunochemical analyses of clinically relevant aspergilli and related fungal taxa

Cell sap (CS) of the pathogenic fungus Aspergillus fumigatus strain Ag-507 was fractionated by Sephadex G-200 column chromatography. A protein fraction designated CS3 was partially characterized by two dimensional electrophoresis (2-DE) and analytical ultracentrifugation. CS3 consisted mainly of low molecular weight components (14 K-43 K) of the whole CS, and produced one peak in analytical ultracentrifugation with an Sapp of 4.25. CS3 was demonstrated to be different from a previously characterized CS fraction designated as CS2, by 2-DE, and by CS2 and CS3 specific antisera. CS3 gave precipitin reactions with three aspergilloma patient sera and 100% of sera from allergic bronchopulmonary aspergillosis (ABPA) patients. Significantly, three ABPA patient sera reacted with CS3 and not CS2. The CS of A. fumigatus strains Ag-515 and Ag-534, were also examined for the presence of CS3 components as were CS preparations of five additional Aspergillus species; A. flavus, A. fischeri, A. terreus, Neosartorya (Aspergillus) fennelliae, and A. niger, and three fungal taxa; Penicillium notatum, Candida albicans, and Saccharomyces cerevisiae. 2-DE, immunoelectrophoresis and double diffusion (DD) analyses of the CS preparations provided complementary information. The immunochemical similarity of CS2 and CS3 components of different aspergilli appears to reflect the taxonomic relatedness of the aspergilli. Additionally, aspergilli exhibiting CS2 and CS3 components most similar to A. fumigatus strain Ag-507 are more frequently isolated from aspergillosis patients. There may be an association of these components with incidence of involvement of the organisms in aspergillosis. DD analysis of the cross-reactivity of CS of all taxa with ABPA and aspergilloma patient sera supported the 2-DE and absorption data.

Identification of the yeast DNA polymerase I gene with antibody probes

Partially overlapping fragments of the gene encoding yeast DNA polymerase I have been cloned by immunological screening of a yeast genomic library constructed in the phage lambda expression vector lambda gt11. The three gene fragments we analyzed in detail encode part of a yeast protein that has been identified as yeast DNA polymerase I, because it shares with this enzyme a number of antigenic determinants. In fact, the yeast protein fragments expressed by the recombinant phages react with both polyclonal and monoclonal antibodies raised against different, highly purified preparations of DNA polymerase I. Moreover, they can be used to affinity purify antibodies specifically reacting with active DNA polymerase I polypeptides and they compete with the yeast enzyme for binding to antibodies that inhibit catalytic activity. The gene is located on chromosome XIV in the yeast genome, and it is transcribed as a 5.2 kb mRNA.

[Interactions between lectins and microorganisms. 1. Determination of the rate of agglutination by measurement of extinction: agglutination of yeast cells (Saccharomyces cerevisiae H155) by concanavalin A]

A simple photometric method for the determination of the agglutination rate of cells by lectins in a continuously stirred suspension is presented. Besides the agglutination rate the method allows the estimation of an average degree of agglutination, i.e. the number of cells per aggregate. The influence of the Con A-concentration, cell number, temperature, and pH on the agglutination rate of Saccharomyces cerevisiae H155 have been studied. The results are of good reproducibility and, therefore, the methods is suitable to describe interactions between cell-bound receptors and receptor-specific proteins, e.g. lectins and antibodies.

Myeloperoxidase reduces the opsonizing activity of immunoglobulin G and complement component C3b

The effect of myeloperoxidase, hydrogen peroxide (H2O2) and a halide (Cl) on the opsonizing molecules in immunoglobulin G (IgG) and complement factor C3b was assayed. At concentrations of the enzyme (1 microgram/ml) that can be found in the extracellular fluid during inflammation, the myeloperoxidase-H2O2-Cl system inhibited the opsonizing effect of IgG and C3b measured as phagocytic uptake and superoxide generation. The effect was related to the enzymatic peroxidative activity of the protein. The presence of albumin (10 mg/ml) reduced the effect of myeloperoxidase with 10-20%. Taurine, which in the presence of myeloperoxidase-H2O2-Cl forms hydrophilic chloramines, and D-penicillamine, which scavenges HOCl, neutralize the inhibitory effect of myeloperoxidase. This suggests that either hypochlorous acid or lipophilic chloramines may exert its effect by oxidizing free sulphydryl groups exposed on the opsonizing ligands. Since the myeloperoxidase-H2O2-halide system also affects chemotactic factors, leukotrienes, proteinases and membrane receptors, the system may in several ways affect the development of the inflammatory response.

Inhibition of yeast phagocytosis in macrophage cultures treated with slime polysaccharide purified from Pseudomonas aeruginosa

This study was initiated to determine whether purified slime polysaccharide(PSP) from P aeruginosa inhibits the ingestion of heat killed Saccharomyces cerevisiae particles in macrophage cultures. Relative to controls, direct phagocytosis assays revealed that the percentages of phagocytes and the numbers of ingested yeast particles per phagocyte decreased in a dose-dependent manner in PSP-treated cultures. Thus, PSP may act as a virulence factor in vivo by impairing the phagocytic capacity of macrophages.

Clinical evaluation of a recombinant hepatitis B vaccine

Recombinant hepatitis B vaccine prepared from antigen expressed in yeast was given to 30 healthy young volunteers. Seroconversion rates and anti-HBs levels were compared with those in a control group matched for age and sex who had received plasma-derived hepatitis B vaccine. 4 weeks after the third immunisation results were similar in the two groups. In the recombinant vaccine group the immune response developed more slowly during the early phase and seroconversion rates and mean anti-HBs levels were slightly lower in males; this probably reflects use of a lower dose of recombinant vaccine (10 micrograms compared with 20 micrograms of the plasma vaccine). Side-effects were slight and antibody titres against Candida albicans were not increased in recipients of the recombinant vaccine.

Immunological evidence for structural homology between Drosophila melanogaster (S14), rabbit liver (S12), Saccharomyces cerevisiae (S25), Bacillus subtilis (S6), and Escherichia coli (S6) ribosomal proteins

Specific antibodies directed against Drosophila melanogaster acidic ribosomal protein S14 were used in a comparative study of eucaryotic and procaryotic ribosomes by immunoblotting and enzyme-linked immunosorbent assays. Common antigenic determinants and, thus, structural homology were found between D. melanogaster, Saccharomyces cerevisiae (S25), rabbit liver (S12), Bacillus subtilis (S6), and Escherichia coli (S6) ribosomes.

Detection of an antigen to primary biliary cirrhosis in wild type and petite mutant Saccharomyces cerevisiae

Antigens to primary biliary cirrhosis (PBC) appeared to be identical in wild type (rho+) and petite (rho o) mutant S.cerevisiae. As the latter mutants lack functional mitochondria, the PBC antigens, which are associated with mitochondrial ATPase in other cells, may be of nucleocytoplasmic origin.

Adherence and phagocytosis of yeast cells by blood monocytes. Effects in vitro of a therapeutic doxycycline concentration

The effect of a therapeutic doxycyline concentration on yeast-cell phagocytosis by blood monocytes was studied in vitro by means of a fluoresence assay. This method allows discrimination between monocyte-adherent yeast cells and ingested yeast cells. The adhesive and phagocytic capacity of 50 monocytes was measured in 16 healthy donors. Yeast-cell adherence was not influenced by doxycycline. In contrast, a slight depression of phagocytosis by doxycycline was suggested. The median difference between doxycyclin-treated and control monocytes was 30% (p = 0.07). It is reasonable to assume that a possible inhibitory effect of doxycycline on monocyte phagocytosis is negligible in healthy individuals. However, a clinically significant effect cannot be excluded in severely immuno-compromised patients.

Fibronectin as an opsonic regulator of monocyte phagocytosis

Experiments using human monocytes and the yeast Saccharomyces cerevisiae have shown that fibronectin is a major plasma opsonin. Further studies have shown that fibronectin promotes the ingestion as well as the adherence of micro-organisms. These observations are independent of the non-physiological concentrations of heparin used in other assay systems.

The expression of cDNA clones of yeast M1 double-stranded RNA in yeast confers both killer and immunity phenotypes

Two cDNA clones of the segment of Saccharomyces cerevisiae M1 double-stranded RNA, which codes for the yeast killer toxin, have been expressed in yeast using the expression vector pYT760. Toxin expression and secretion depended upon the presence of a yeast promoter. Transformants not only contain an authentic preprotoxin precursor, as determined by precipitation of intracellular proteins with antitoxin antisera, but also display an immunity phenotype. The evidence is that the immunity protein is part of the preprotoxin and may act by masking toxin binding sites. Neither cDNA clone had a complete 5' terminus and the preprotoxin translational start was missing. The promoter and the initiator ATG were supplied by the expression vector. One clone with a full-length preprotoxin but altered N-terminal amino acids gave a normal glycosylated intracellular precursor. A clone with an N-terminal nine amino acid deletion gave a precursor which was not glycosylated but toxin was still secreted.

Clinical evaluation in healthy adults of a hepatitis B vaccine made by recombinant DNA

A vaccine formulated from hepatitis B surface antigen (HBsAg) produced by a recombinant strain of the yeast Saccharomyces cerevisiae was administered to two groups of human volunteers composed of 37 healthy, low-risk adults. Each subject received a 10-micrograms dose of HBsAg at 0, 1, and 6 months. By one month, 27% to 40% of the vaccinees had antibody to HBsAg, and by three months 80% to 100% were antibody positive. Large boosts in titer followed the third dose at six months. The antibody formed is predominantly specific for the a determinant of HBsAg. There have been no serious reactions attributable to the vaccine. The most frequent complaint has been transient soreness at the injection site. As far as we know, this is the first reported use in man of a vaccine prepared by recombinant DNA technology.

[Phagocytosis of neutrophilic granulocytes of intensive care patients: effect of immunoglobulin preparations]

Phagocytic capacity and the amount of PMN-granulocytes which take part in phagocytosis was investigated in patients with septicemia and polytrauma patients in comparison to PMN-granulocytes withdrawn from healthy volunteers by use of a standardized test-system in which autoclavated S.cerevisiae is the phagocytic agent. Influence of polyvalent immunoglobulin preparations together with patients' own serum incubation was compared with serum preincubation only in the test system mentioned above. It became evident that phagocytic capacity and the number of PMN-granulocytes which take part in phagocytosis in patients with septicemia are primary on a significant higher rate than those of other groups. PMN-granulocytes from polytraumated patients showed a significant higher rate on ingestion of S.cerevisiae pretreated with patients' own serum - especially after preopsonisation with immunoglobulins - than granulocytes from patients with septicemia or healthy volunteers.

Antibodies against the alpha-factor pheromone of Saccharomyces cerevisiae

The mating pheromone of baker's yeast, the alpha-factor, is a dodeka-/tridecapeptide, which is not antigenic by itself. It was coupled to succinylated thyroglobulin by the carbodiimide procedure to facilitate selective coupling of the alpha-factor mainly by its N-terminal region. Antibodies against this conjugate were raised in rabbits. After selective precipitation of the rabbit antiserum with succinylated carrier prior to the radial double diffusion test (Ouchterlony) specific antibodies against the coupled alpha-factor could be detected.

Carbohydrate specificity of the surface lectins of Escherichia coli, Klebsiella pneumoniae, and Salmonella typhimurium

A large number of linear and branched oligosaccharides and several glycosides of D-mannose were tested for their inhibitory activity on the agglutination of yeast cells or guinea pig erythrocytes by three D-mannose-specific enteric bacteria possessing type 1 fimbriae. With Escherichia coli 346, the best inhibitors found are the alpha glycosides of the branched oligosaccharides alpha-D-Manp-(1 leads to 3)-[alpha-D-Manp-(1 leads to 6)]-alpha-D-Manp-(1 leads to 6)-alpha-D-Manp-(1 leads to 3)-D-Manp and alpha-D-Manp-(1 leads to 3)-[alpha-D-Manp-(1 leads to 6)]-alpha-D-Manp- (1 leads to 6)-[alpha-D-Manp-(1 leads to 2)-alpha-D-Manp-(1 leads to 3) ]-D-Manp and the trisaccharide alpha-D-Manp-(1 leads to 3)-beta-D-Manp-(1 leads to 4)-D-GlcNAc, all of which are 21-30 times more inhibitory than methyl alpha-D-mannopyranoside. The aromatic glycoside p-nitrophenyl alpha-D-mannopyranoside was also a strong inhibitor (30 times more inhibitory than methyl alpha-D-mannopyranoside), whereas the corresponding beta-D-glycoside was only a weak inhibitor (approximately as methyl alpha-D-mannopyranoside). A nearly identical pattern of inhibitory activity was observed with the fimbriae. This suggests that the combining site of the E. coli fimbrial lectin is in the form of an extended pocket on the surface of the lectin corresponding to the size of a trisaccharide and fitting best the structure alpha-D-Manp-(1 leads to 3)-beta-D-Manp-(1 leads to 4)-D-GlcNAc. Since p-nitrophenyl alpha-D-mannopyranoside is a strong inhibitor, the existence of a hydrophobic region in the combining site or close to it was assumed. The combining site of the Klebsiella pneumoniae fimbrial lectin is probably similar to that of E. coli, but that of the Salmonella typhimurium fimbrial lectin differs considerably. It appears that the combining sites of the three bacterial lectins tested exhibit preference for structures found in N-glycosylic oligomannoside units of mammalian cell surface glycoproteins.

A new method of preparing hapten-carrier immunogens by coupling with Saccharomyces cerevisiae by periodate oxidation

A new method of preparing hapten-carrier immunogens is described. The carrier used was Saccharomyces cerevisiae yeast. Coupling was carried out with bovine serum albumin (BSA). BSA was conjugated with mannose residues of Saccharomyces cerevisiae cell walls, following periodate oxidation to produce aldehyde groups reactive with side chain amino groups of BSA. The coupling was stabilized and non-reactant aldehydes were blocked with sodium borohydride reduction. A hapten, 3,5,3',5'-tetraiodo-L-tyrosyl-L-tyrosine, was also coupled with the yeast. Anti-hapten antibodies were obtained in rabbit with this conjugate.

A simple and rapid flow cytometric method for routine assessment of baker's yeast uptake by human polymorphonuclear leukocytes

A new method for measuring uptake of baker's yeast (BY) by human polymorphonuclear leukocytes (PMN) using flow cytometry is described. The method correlates excellently with the visual method, is reproducible and provides a means for investigating the early phases of the phagocytic process as well as the phagocytic capacity of PMN. This quick and accurate method allows the counting of large numbers of cells, and monitoring of the process of particle uptake and has a considerable potential in the routine assessment of polymorph function in various clinical situations.