Demonstration of cross-reactions between pneumococci and alpha-streptococci using gold-labelled mono- and polyclonal antibodies and electron microscopy

Cross-reactions between alpha-streptococci and the pneumococcal C-polysaccharide (PnC) were investigated using electron microscopy and immunogold labelling of bacterial cells. Monoclonal antibodies against two different determinants of the PnC molecule were used, one directed against the chain sugar of the repeating unit 2-acetamido-4-amino-2,4,6-trideoxygalactose (Sug) and the other against the phosphorylcholine residue. Two different immunogold techniques were tested, either by direct labelling of the monoclonal antibody or by using an antimouse immunogold conjugate to demonstrate binding of the monoclonal antibodies. Antibodies against the "Sug" determinant reacted only with pneumococci, whereas antibodies against the phosphorylcholine determinant bound to cross-reacting streptococci as well as to pneumococci. These results indicate that the cross-reacting antigens of the alpha-streptococci contain phosphorylcholine residues, but that they are not identical to the C-polysaccharide molecule.

Absence of autolytic activity (peptidoglycan nicking) in penicillin-induced nonlytic death in a group A streptococcus

The extent of sublytic autolysin activity (peptidoglycan [PG] nicking) after exposure of exponentially growing cultures of a group A streptococcus (GAS) to benzylpenicillin (PenG) was studied by determining changes in the glycan chain length of PG polymers. The average PG chain length in isolated cell walls was estimated by calculating the ratio of the total hexosamine content (Morgan-Elson-reactive material) to reducing-end group content established via quantitation of [3H]borohydride reduction products. Comparison of the average PG chain length obtained from untreated control cultures of GAS with those obtained after exposure to a saturating dose of PenG revealed no decrease over a time interval equivalent to four mass doublings of the control cultures. Exposure to this concentration of PenG for a time equivalent to only two mass doublings resulted in approximately 90% loss of viability. In contrast, exposure of the lytic bacterium, Streptococcus faecium ATCC 9790, to a 50% growth inhibitory dose of PenG produced a 20% reduction in the average PG chain length concomitant with only a 65% loss of viability. Preliminary characterization of the autolytic system of GAS indicated that this streptococcus has a hexosaminidase-type autolysin. The results presented indicate the lack of autolytic activity in PenG-induced nonlytic death.

Proliferative response of human T lymphocytes to a vaccinal preparation of ribosomes from Streptococcus pyogenes

The in vitro lymphocyte-activating properties of a ribosomal preparation of Streptococcus pyogenes were investigated. The preparation was mitogenic for human lymphocytes with a peak of 3H-thymidine incorporation occurring after 3-5 days of culture. The response was abolished by removal of CD3-positive cells and by alteration of accessory cells by exposure to L-leucine methyl ester. Most of the cells synthesizing DNA at the end of the culture expressed CD4 or CD8 but not CD20 antigens. No immunoglobulin synthesis was demonstrable. Although the same preparation was shown to be a T-independent polyclonal B-cell activator of murine cells, it preferentially triggers T cells in humans.

Molecular interactions between human IgG, IgM rheumatoid factor and streptococcal IgG Fc receptors

Group A streptococci type M15 were previously shown to bind both human IgG via the Fc component and a purified monoclonal IgM kappa rheumatoid factor (IgM RF). Using 125I-labelled IgG and 125I-labelled IgM RF, the present study gave association constants of 2.2 x 10(7) and 2.9 x 10(8) M-1, respectively. The binding of 125I-IgG to the streptococci was inhibited by unlabelled IgG, IgG Fc and fragment D of staphylococcal protein A but not by the IgM RF or F(ab')2 of anti-idiotype antibodies to RF (anti-Id RF). Inversely, unlabelled IgM RF and anti-Id RF inhibited the binding of 125I-IgM RF markedly and unlabelled human IgG and IgG Fc only slightly or moderately, respectively. Thus, group A streptococci type M15 showed different binding sites for IgG Fc and the antibody combining sites of a human monoclonal RF. The findings were still more complex on a background of previous reports showing that streptococcal IgG Fc receptors and RFs bind to the same amino acids on the Fc molecule. This complex pattern may play a role in the pathogenesis of rheumatoid arthritis.

Hemagglutination activity and localization of Fc receptor of group A and G streptococci

The IgG-Fc binding activity and binding sites on the cell surface of streptococci, strains AR1 (group A) and G148 (group G), and Staphylococcus aureus strain Cowan I were examined by hemagglutination (HA) and immunoelectron microscopic methods. No distinct difference was observed in the HA activity among these three strains. However, the strains differed in the distribution of Fc receptor. Cowan I cells (having protein A) were heavily covered with two layers of ferritin particles, whereas AR1 cells were heavily covered with a single, rough layer of ferritin particles. G148 cells (having protein G) were labeled with a relatively thin, rough ferritin layer. The trypsin susceptibility of the Fc receptors of the AR1 strain was much higher than that of the G148 strain. These results suggest that both streptococcal strains are distinctly different in the arrangement or in the conformation of the Fc receptor from the Cowan I strain. It is also suggested that the Fc receptor molecules of the streptococcal strains differ from each other not only in conformation but also in trypsin susceptibility.

[Ultrastructure of the L forms of Streptococcus group B]

The submicroscopic organization of the L-forms of beta-hemolytic streptococci of group B has been studied in the course of their cultivation. The L-forms of group B streptococci differ from those of group A streptococci by a higher growth rate. On the submicroscopic level, the activity of ATP-ase has been revealed on the internal side of the cytoplasmic membrane. Regularities in the localization of intramembranous particles sized 6-18 nm in the hydrophobic area of the membrane have been established by means of freezing-etching. With the adequate methods of fixation, the continuous three-layer structure of the cytoplasmic membrane can be determined in all elements of the L-form population.

M proteins of group G streptococci isolated from bacteremic human infections

We studied seven strains of group G streptococci isolated from clinically severe bacteremic infections in six intravenous drug abusers. These group G strains multiplied luxuriantly in fresh human blood. On electron microscopy, they exhibited surface fibrillae similar to those observed in M-protein-rich group A streptococci, but they were not serologically M typable with a battery of 39 M antisera. Rabbit antisera raised against two of the group G strains (1618 and 1750) opsonized the homologous but not the heterologous isolates and exhibited type-specific Ouchterlony immunoprecipitin reactions. Moreover, antisera raised against peptic extracts of strain 1750 also promoted phagocytic killing of that strain. Anti-1750 reacted in high titer in an enzyme-linked immunosorbent assay against peptic extracts of the homologous strain; these antibodies were removed by absorption with 1750 cells but not by absorption with heterologous strains. These studies represent, to our knowledge, the first analysis of virulence factors of group G streptococci isolated from invasive human disease. The seven epidemiologically related blood isolates of group G streptococci possess distinct type-specific, antiphagocytic surface virulence factors analogous to the M proteins of group A streptococci.

[Comparative biological characteristics of the L-form of Streptococcus group A and B]

The comparative study of the biological and serological properties of the L-forms of streptococci, groups A and B, has been made. Their morphological similarity on the level of light microscopy has been demonstrated. The use of ring precipitation, gel diffusion, passive hemagglutination, aggregate hemagglutination, as well as the immunoferritin technique, has made it possible to establish the presence of specific antigens in the L-forms of streptococci, groups A and B. Serological cross reactions are negligible. The future development of a diagnosticum for the specific indication of these antigens is proposed. The fact of the presence of specific antigens in the L-forms of streptococci in comparison with the initial streptococcal strains has been confirmed.

Albumin bound to the surface of M protein-positive streptococci increased their phagocytosis by human polymorphonuclear leukocytes in the absence of complement and bactericidal antibodies

Using a phagocytosis assay (Leijh 1980, Infect. Immun. 30, 421), determination of chemiluminescence, and transmission electron microscopy, the influence of the binding of albumin to M protein-positive group A streptococci on their phagocytosis by human polymorphonuclear leukocytes (PMNL) was investigated. Coating of streptococci with albumin in the absence of other serum components enhanced phagocytosis but not killing of the bacteria. Complement had no additional effect on engulfment. Fibrinogen reduced the enhancing effect of albumin. Albumin had no additional effect on the high phagocytosis rate of an M-protein-negative strain. It could be demonstrated that human PMNL bound human serum albumin-gold conjugate. The results are discussed with regard to the role of plasma proteins in the phagocytosis of streptococci under in vivo-conditions.

Uveitis and arthritis induced by systemic injection of streptococcal cell walls

A single injection of an aqueous suspension of group A streptococcal peptidoglycan-polysaccharide complexes (PG-PS) when injected intraperitoneally into Lewis rats induced a self-limiting bilateral uveitis with associated perpetuating polyarthritis. The uveitis was characterized clinically during the first 72 h by iritis and fibrin deposition. Acutely, there was infiltration of polymorphonuclear cells. The symptoms gradually subsided, and at the close of the experiment eyes were normally clinically and histologically. In contrast, perpetuating inflammation and severe tissue injury developed in the limb. Using an enzyme immunoassay with specificity for the group A streptococcal polysaccharide, the levels of PG-PS in tissues of animals that were killed 1 to 7 days post-injection were measured. The relative amounts of antigen in eye:limb:liver of PG-PS injected animals were 1:9:170. The differences in the amounts of antigen detected in the eye and limb may help explain the development of the acute uveitis in contrast to the perpetuating polyarthritis observed on PG-PS administration. The authors suggest that bacterial debris may act similarly in causing ocular inflammation in man.

[Lymphocyte activation by bacterial biostructures: precursor of infection-induced immune phenomena and sequelae? I. lymphocyte reactions to A-streptococci]

The pathogenesis of the nonsuppurative sequelae of bacterial infections, e.g. rheumatic fever (RF) following A-streptococcal infection and seronegative spondarthritis (SS) following enterobacterial infection, is thought to be related to 1. an unusual persistence of infection, and/or 2. direct toxic effects of bacterial toxins, and/or 3. an abnormal immune response to the inital infection. Additionally, modern working hypothesis center around more recent findings concerning the genetic predisposition (for which there are now markers in both diseases) and the various immunologically active biostructures of the bacteria. These structures consist chiefly of a. crossreactive (CR) antigens, i.e. common or similar epitopes in both bacteriae and mammalian tissues, and b. polyclonal cell activators, e.g. the polyclonal B-cell activator (PBA) which induce immunologically many nonspecific resting B-cell clones to mature into Ig secreting cells. In this paper the lymphocyte response to a wide range of bacterial cell preparations is described. Blood lymphocytes from both RF and SS patients respond to the disease-precipitating microorganism more rigorously than the controls. There are several lines of evidence that the heightened response is genetically determined. However, there are no obvious facts which can confirm the idea that the so-called cross-reactive antigen preparations induce a specific cell response to CR antigens. On the contrary, such crude cell membrane preparations are obviously composed of an antigenic mosaic and of polyclonal cell activators: lymphocytes from healthy blood donors and even from newborns respond with lymphokine production, blastogenesis and Ig secretion under certain circumstances.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding of IgM rheumatoid factor to group A, C and G streptococci with IgG Fc receptors

The possibility that IgM rheumatoid factors bind to streptococci was studied. Using a sequence of Sephadex G200 gel filtration, protein A-Sepharose CL-4B chromatography and preparatory electrophoresis, IgM was isolated from the sera of 2 patients with rheumatoid arthritis and then radiolabelled with 125I. There was significant binding of radiolabelled IgM to group-A streptococci types M1, M15 and M22, and to a group-C and a group-G strain, all expressing IgG Fc receptors, but none to Staphylococcus aureus, Escherichia coli or to 11 other strains of streptococci without IgG Fc receptors. The radiolabelled IgM was separated by affinity chromatography on a column containing human IgG. Types M1 and M15 bound the fraction retained on the column, whereas M22 bound both this fraction and the non-retained fraction. Commercial human IgG, even at high concentrations, did not inhibit binding. The binding reaction, which is perhaps triggered either by the IgM rheumatoid factor or by IgG complexed with rheumatoid factor, could be a useful tool for removal of anti-immunoglobulin from the blood of patients with rheumatoid arthritis.

[Development and experimental study of a dried nutrient medium for the microbiological diagnosis of streptococcal infections]

The comparative study of different protein bases has shown that the combined base containing animal blood hydrolysate (amino peptide) and acidic casein hydrolysate, moderately cleaved, in the proportion 1:1 is a good source of nitrogen and ensures the intensive growth of streptococci. As determined by the study of the physiological parameters and growth of streptococci, the presence of fodder yeast extract, glutamine, glucose and phosphates in media containing blood hydrolysate and casein hydrolysate has been found to render a stimulating effect on the growth and multiplication of these organisms. The data thus obtained have been used as the basis for developing the formula of a dried culture medium, capable of ensuring the growth of streptococci without blood or serum added and not inferior in its quality to Todd-Hewitt Broth manufactured by Oxoid Ltd. (Great Britain) and Difco Laboratories (USA). The physico-chemical and physiological characteristics of the proposed medium have been determined. The use of the new dried culture medium in medical practice will make it possible to improve the microbiological diagnosis of streptococcal infections.

The influence of penicillin on growth and morphology of Streptococcus pyogenes in vivo

The influence of penicillin (pc) on the growth, phagocytosis and killing of Streptococcus pyogenes was studied for an M protein positive (M+) and an M protein negative (M-) strain in vivo as well as in vitro. In vivo studies were based on a tissue cage model and the analyses were performed by CFU determinations and electron microscopic investigations. The M- strain was easily phagocytized with and without pc, but killing only occurred after pc treatment and thus the number of viable bacteria rapidly decreased under the influence of pc. M+ streptococci were not reduced in numbers by pc-treatment in vivo, but morphological changes and at high pc concentrations, phagocytosis could be seen. When this strain (M+) was cultivated in the absence of pc, the phagocytic cells were totally destroyed - a reaction that was prevented by penicillin. Variations in surface morphology of the two strains seem to influence the differences in sensitivity to penicillin, phagocytosis and killing.

Chemical analyses of membranes isolated from Streptococcus mutans BHT

Cell membranes of Streptococcus mutans BHT (serotype b) were prepared following glass-bead disruption or mutanolysin digestion of whole cells. Major constituents of purified BHT membranes included: protein (60-65%), fatty acids (10%), glucose (3%), and phosphorus (0.5%). The principal amino acids measured were glutamate, aspartate, lysine, alanine, and leucine. The principal fatty acids measured were octadecenoic, palmitoleic, palmitic, and eicosenoic acids; smaller amounts of eicosanoic acid were also detected. Chemical analyses of membranes from cells grown to four different growth phases revealed no major shifts in composition during batch growth under our experimental conditions. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of these four membrane preparations confirmed the apparent compositional stability of cell membranes during growth.

Electron microscopic localization of receptors for aggregated beta 2-microglobulin on the surface of beta-hemolytic streptococci

The presence and location of receptors for aggregated human beta 2-microglobulin (beta 2m) on the surface of group A, C, and G streptococci were studied by electron microscopic techniques. Ferritin-conjugated aggregates of human beta 2m were used in direct binding experiments. Ferritin-conjugated antibodies against beta 2m were employed in a two-step indirect binding assay where the streptococci were incubated with unlabeled beta 2m aggregates before the addition of antibodies. Similar results were obtained with these two methods. Among tested group C and G strains, some showed binding of beta 2m, whereas others were negative. In group A streptococci, beta 2m binding was localized to filamentous structures typical of M protein. In two M protein-negative group A strains, the reactivity was heterogeneous, revealing a majority of unlabeled, but also some heavily labeled streptococci. Morphologically, these beta 2m-binding bacteria exhibited M protein-like projections in contrast to the smooth surfaces of unlabeled cells.

[Isolation and study of the properties of Streptococcus pyogenes ribosomes]

Ribosomes from Streptococcus pyogenes, group A, strain 29 were studied. A comparison of different methods of ribosomal isolations has shown that the homogenous ribosomal samples can be obtained by the method of differential ultracentrifugation using tris-HCl buffer. The ribosomes of S. pyogenes had the sedimentation coefficient of 70S and consisted of 65% of protein and 35% of nucleic acids; the ribosomes dissociated into subparticles with the sedimentation coefficients of 50S and 30S under a low magnesium concentration. Thus the S. pyogenes ribosomes do not differ from the ribosomes of procaryotes. It was shown that the ratios of 70S, 50S and 30S ribosomal subparticles in the cells depend on the growth phase of S. pyogenes. The cells of the middle and the late logarithmic phase contained 50S and 30S particles in a stoichiometric ratio. In the cells of the late stationary growth phase there was a deficiency of 30S ribosomal subparticles which does not result from a loss during the isolation procedure, as it was already observed in the initial 30S fraction.

[Electron microscopic study of the interrelation of the L forms of beta-hemolytic Streptococcus group A with mouse peritoneal macrophages]

Interrelations between the L-forms of group A beta-hemolytic streptococci and mouse peritoneal macrophages have been studied by electron microscopy. The macrophages have been shown to actively phagocytize L-form cells in great amounts. Most of the phagocytized L-forms are destroyed and become nonviable, but a few of them survive as elementary bodies within 48 hours.

Fibronectin-mediated binding of group A streptococci to human polymorphonuclear leukocytes

Human plasma was shown to promote the attachment of an avirulent strain of Streptococcus pyogenes to human polymorphonuclear leukocytes. Removal of the fibronectin by absorption of the plasma with agarose-immobilized gelatin abolished the attachment-promoting activity. The activity of the absorbed plasma was restored with purified human serum fibronectin. The fibronectin was found to promote the attachment of three M protein-negative, but not of three M protein-positive, strains of streptococci. Radiolabeled fibronectin was shown to bind in various degrees to all strains of S. pyogenes tested. Thus, in the absence of streptococci surface M protein, fibronectin promotes the association of group A streptococci with human polymorphonuclear leukocytes.

[Modes of the formation of elementary bodies and their isolation from the cell in L-form bacteria]

Elementary bodies are formed on the cell surface and inside the cell body in all cell types characteristic of L-form cultures, i. e. spherical cells, large bodies and filament structures. The following ways of elementary body formation are described: by budding on the cell surface, appearance immediately in the cytoplasm, in the vacuole, as a result of cytoplasmic fragmentation accompanied by the lysis of the cell, as well as in cases of the separation of cytoplasmic areas surrounded by the membrane or the myelin-like structure. The release of elementary bodies from the cell occurs as a result of the lysis or death of the mother cell, the thinning of the vacuole wall, and possibly due to small transient defects in the membrane, not accompanied by the death of the mother cell. The scheme of the formation and release of elementary bodies from the cell is presented.

Ultrastructural study of interaction of group A streptococci with tissue culture cells

Submicroscopic aspects of the adherence of Group A streptococci to HEp-2 cells and the time sequence of their further interaction with these cells were studied. The M+ variant of streptococci, characterized by the presence of filamentous protrusions on the cell wall, displayed a high capacity for adherence, in contrast to the M- variant of the same strain, where adherence was low. The first stage of the interaction between M+ variant of Group A streptococci and HEp-2 cells was adherence of the filamentous protrusions of the bacterial cell wall to host cell cytoplasmic membrane; this was followed by closer contact of the streptococcus cell wall with HEp-2 cell surface. Continuing incubation led to the development of invaginations in the cytoplasmic membranes of HEp-2 cells, into which streptococci gradually penetrated. Ingestion of streptococci into the forming pseudovacuoles of the host cell was accompanied by bacterial cell division, culminating in total disintegration of the host cell and release of the streptococci into the medium. At all stages of the interaction there was a pronounced tendency to form multiple contacts between the surface structures of the streptococcus cell and the membrane structures of the animal cell being attacked.

Streptococcal M protein: alpha-helical coiled-coil structure and arrangement on the cell surface

The conformation and molecular dimensions of purified type 6 streptococcal M proteins establish the close structural relationship of these molecules to tropomyosin. Ultracentrifuge studies reveal that the M molecules exist as stable dimers; circular dichroism spectra indicate that the molecules contain about 70% alpha helix; and fiber x-ray diffraction diagrams show the characteristic reflections of the alpha-helical pattern. Electron microscopic images of M protein shadowed with platinum reveal rod-shaped molecules having the same width as tropomyosin. However, the lengths of the M molecules are about 30% shorter than lengths predicted by assuming a completely alpha-helical molecule. These findings indicate that the structure of the M6 protein is primarily alpha-helical coiled coil. Comparison of the lengths of the fibers on the surface of the streptococcus and the isolated M proteins suggests that each fiber on the cell wall consists of a single M-protein molecule approximately 500 A long. The structure determined for these fimbriae is the first alpha-helical coiled-coil conformation to be demonstrated for bacterial surface projections.

Potentiation of opsonization and phagocytosis of Streptococcus pyogenes following growth in the presence of clindamycin

Streptococcus pyogenes, bearing M-protein on its surface, resists opsonization by normal human serum and subsequent phagocytosis by human polymorphonuclear leukocytes. Previous studies have shown that M-protein positive organisms are poorly opsonized by the alternate pathway of complement. In an attempt to define further the role of the surface components of S. pyogenes in this process, we examined the ability of clindamycin, an antibiotic that inhibits protein biosynthesis, to alter bacterial opsonization. An M-protein positive strain of S. pyogenes was grown in varying concentrations of clindamycin at levels lower than those which inhibited growth, i.e., at levels less than the minimal inhibitory concentration. These bacteria were incubated with purified human polymorphonuclear leukocytes and peripheral blood monocytes. Significant enhancement of bacterial opsonization, phagocytosis, and killing resulted. Measurement of complement consumption and binding of the third component of complement (C3) onto the bacterial surface demonstrated that organisms grown in the presence of clindamycin activated complement more readily and fixed more C3 on their surface. Electron microscopy revealed the probable basis for these findings. Streptococci exposed to clindamycin during growth were largely denuded of surface "fuzz," the hairlike structures bearing M-protein. We conclude that the incorporation of clindamycin at concentrations that fail to inhibit growth of S. pyogenes nevertheless causes significant changes in the capacity of these bacteria to resist opsonization by serum complement. These findings support the hypothesis that M-protein inhibits bacterial opsonization by interfering with effective complement activation on the bacterial surface.