Fine specificities of the murine T cell responses to (Glu Lys Ala) terpolymers

The T cell proliferative responses to GLA terpolymers among mice of H-2 a, b, d, k, q, r and s haplotypes are heterogeneous. Following immunization with GLA20, GLA40 and GLA60, mouse T cells reacted well with the three terpolymers. The cross-reactions of the above T cells to GLA5 decreased as the alanine content in the terpolymers (immunogens) increased, whereas the trend of the cross-reactions to GA40 did not change. The RIII strain showed no cross-reaction with GLA5. Only mice of H-2 haplotypes q and s failed to show cross-reactions to GA40. Mice of the H-2q haplotype are genetic non-responders to GA40, whereas those of the H-2s haplotype are responders. Immunization of SJL mice with GA40 mixed with GLA40 led to reduction of the specific T cell response to GA40. This reduction of GA40 specific T cell responses in SJL mice by GLA40 occurred during the early stage of the immune response. The kinetic study showed that it was necessary to inject the GLA40 intraperitoneally at least 7 days before GA40 in order for the reduction to take place. The PETLES and lymph node T cells from DBA/1 mice were found to respond to GLA40 differently, and these cells from SJL mice responded differently to GA40.

Ir gene control of T and B cell responses to determinants in (Glu Lys Ala) terpolymers

All mice responding to the terpolymer GLA40 make GL, GA and GLA specific antibodies irrespective of their response to GL or GA alone. The mice displayed positive T cell proliferative responses against the homologous terpolymer, but no T cell responses were obtained with GL, which is non-immunogenic in mice. T cells from GLA immune mice, which are also responders to GA, such as mice of H-2 haplotypes a, b, d, k and r, could be stimulated by GA. T cells from GLA immune mice of H-2 haplotypes p and q which are non-responders to GA could not be stimulated by GA. On the other hand, T cells from H-2s mice immune to GLA and which are also responders to GA alone could not be stimulated by GA. Thus mice of H-2 haplotypes p, q and s recognize the terpolymer via 'GLA' determinants alone, whereas mice of H-2 haplotypes a, b, d, k and r may recognize both GA and GLA determinants in GLA terpolymer.

Release of toxic microvesicles by Actinobacillus actinomycetemcomitans

Oral isolates of Actinobacillus actinomycetemcomitans (strain Y4) release spherical microvesicles in large numbers during normal growth. The biological activities of these products were studied, and it was estimated that approximately 1/10 of their dry weight was made up of heat- and proteolysis-resistant endotoxin. The chicken embryo lethality and bone-resorbing activity of the microvesicles were heat stable but proteolysis sensitive. Other laboratories have reported the presence of a heat- and proteolysis-sensitive leukotoxin in similar preparations. Accordingly, the microvesicles released by strain Y4 may contain, in addition to endotoxin, several potent substances which are highly toxic and active in bone resorption, and these may be significant factors in the pathogenesis of periodontal diseases.

Characterization of an inducible bacteriophage from a leukotoxic strain of Actinobacillus actinomycetemcomitans

A bacteriophage, designated phi Aa17, was isolated by mitomycin C induction from leukotoxic Actinobacillus actinomycetemcomitans strains 651. Electron microscopy of the virus revealed particles with regular, nonelongated, polyhedral heads, and tails consisting of a contractile sheath and core. Spikes emanated from the base of the tail. The head had a diameter of 70 nm. The fully extended tail sheath had a length of 127 nm and a diameter of 22 nm. In its contracted form, the tail sheath measured 47 nm in length and 25 nm in diameter. The phage had a buoyant density of 1.370 in CsCl, and its genome was found to be double-stranded DNA. A single-cycle growth curve revealed that the phage had a latent period of 30 min and a burst size of 435 PFU per cell. The host range of the phage was examined, and A. actinomycetemcomitans strains ATCC 29523 and ATCC 29524 were found to be phage sensitive, whereas strains Y4, ATCC 29522, 2043, 652, 651, 627, 2097, N27, 2112, and 511 were resistant. The host range of this virus does not suggest any association between the phage and leukotoxin production.

Comparative antibody titers to Actinobacillus actinomycetemcomitans in juvenile periodontitis, chronic periodontitis and periodontally healthy subjects

Circulating antibody levels to four strains of Actinobacillus actinomycetemcomitans (Aa) were determined by means of an indirect immunofluorescent technique in three groups of 21 subjects each, including one with juvenile periodontitis (JP), one with chronic periodontitis (CP) and one free of periodontal disease (N). Mean levels of antibody to Aa were significantly elevated in the JP group as compared to the CP and N groups with respect to strains Y4, 29522 and 29524, but not strain 29523. Since strains Y4, 29522 and 29524 contain a leukotoxin that is missing from strain 29523, the results suggest that the leukotoxin could account for the difference in the immune response among the three groups of subjects. Varying the end-point considered to represent positive fluorescence did not significantly affect the results, although discrimination among the three groups appeared to be somewhat better at lower intensities of fluorescence. Because of wide variations in antibody titers recorded in individual subjects, elevated levels of antibody to certain strains of Aa may not be useful as a primary diagnostic test for JP, but may be of value in confirming an otherwise uncertain clinical diagnosis.

Comparative ultrastructure of certain Actinomyces species, Arachnia, Bacterionema and Rothia

A comparative ultrastructural study was carried out on several species of Acinomyces and related Gram-positive rods including Arachnia, Bacterionema, Rothia and Leptotrichia. A total of 52 well characterized strains were examined by transmission electron microscopy. Particular attention was paid to the ultrastructure of the cell periphery, that is the plasma membrane, periplasmic space, the cell wall per se and extramural structures, including surface "fuzz". In addition, the ultrastructure of various features of the cytoplasm were also examined. A good correlation appeared to exist between certain ultrastructural characteristics of the microorganisms and their taxonomic position as determined by other criteria. It should be noted, however, that the ultrastructure of certain strains differed markedly from that of the remaining strains of the species. This observation raises some doubt on the appropriateness of the current classification for these particular strains. The ultrastructural features of the cell periphery were found to be particularly stable for all strains grown under standard conditions. For this reason, ultrastructural features of the cell wall and associated structures are probably a more reliable source of morphological criteria for identification purposes than the ultrastructural characteristics of the cytoplasmic components which tend to be more variable. The results suggest that certain ultrastructural features are useful criteria for the identification and classification of these Gram-positive rods.

Immune labeling of certain strains of Actinomyces naeslundii and Actinomyces viscosus by fluorescence and electron microscopy

A total of 12 well-characterized strains of Actinomyces viscosus and A. naeslundii grown on Trypticase soy agar plates supplemented with sheep erythrocytes were examined by light microscopy and transmission electron microscopy after treatment with appropriately labeled antisera to homologous and heterologous strains. Cells incubated with homologous rabbit antisera followed by fluorescein-isothiocyanate (FITC)-conjugated goat anti-rabbit immunoglobulin G (IgG) exhibited a completely smooth fluorescent outline in the case of A. naeslundii and and interrupted, irregular fluorescent outline in the case of human strains of A. viscosus. The different labeling patterns appeared to be related to the presence at the ultrastructural level of long, unevenly distributed strands of "fuzz" on the surface of human A. viscosus cells, whereas A. naeslundii cells had a narrower layer of fuzz, or more even thickness. The immunocoating reaction revealed homologous antibody binding to the irregular strands of fuzz on the surface of human A. viscosus cells, whereas homologous antisera to A. naeslundii coated A. naeslundii cells with a moderately electron-dense coating of antibody of even thickness. Human strains of A. viscosus incubated with heterologous antiserum to A. naeslundii followed by FITC-labeled goat anti-rabbit IgG exhibited a segmented fluorescent outline, which differed from that produced with homologous antisera. A. naeslundii incubated with heterologous rabbit antisera to human A. viscosus strains and FITC-labeled anti-rabbit IgG exhibited a completely smooth fluorescent outline similar to that produced with homologous antiserum. A. viscosus strains of hamster origin differed from A. viscosus strains of human origin by the absence of a surface fuzz and the comparatively smooth, even fluorescence produced by incubating these cells with homologous rabbit antiserum followed by FITC-labeled goat anti-rabbit IgG. Antiserum to a hamster strain did not cross-react with A. naeslundii or human strains of A. viscosus. Under the growth conditions of this experiment, ultrastructural features and labeling patterns with the indirect fluorescent technique may be useful in differentiating these serotypes from one another.

Group and type antigens of Capnocytophaga

Group-specific and type-specific antigens have been identified and purified from sonic extracts of Capnocytophaga. The group-specific antigen, which was purified by affinity chromatography, was found to be identical to an antigen present in all 26 strains tested. The antigen is sensitive to trypsin, sodium dodecyl sulfate and heat labile, and composed predominantly (55%) of protein. The type-specific antigen, which was obtained by preparative immunoelectrophoresis, was found to be present in only 3 of the 26 strains tested. This antigen was resistant to heat, trypsin, and sodium dodecyl sulfate and was primarily composed of carbohydrate (47% phenol-sulfuric acid-positive material, 8% amino sugar). Agglutination and fluorescent antibody data suggest that both the group- and type-specific antigens reside on the cell surface.

Role of bacterial products in periodontitis: immune response in gnotobiotic rats monoinfected with Eikenella corrodens

The development of humoral and cell-mediated immune responses to Eikenella corrodens (a bacterium that causes periodontal lesions in gnotobiotic rats) was measured and compared with the rate of appearance of macroscopic lesions. A possible inverse relationship was found. A strong cell-mediated immune response, as measured by skin reactivity and lymphocyte mitogenesis, occurred between 4 and 6 weeks after infection and subsided soon thereafter to a low response level. Humoral antibodies to endotoxin from E. corrodens could not be detected at any time. The disease developed only after the cell-mediated immune response diminished, thus suggesting that lack of an efficient immune response may permit the development of the disease. This is seemingly in contradiction to the assumption that tissue destruction in such cases is caused by the immune response and its products. We are inclined to believe, based on our findings reported here, that the lack of immune responsiveness to the bacterium and/or its products is the major causative factor in the development of periodontitis. At the same time, we wish to emphasize that occurrence of both phenomena during the long development of periodontal disease is possible.

Immune responses of inbred guinea pigs and mice to helical sequential polymers of amino acids

The immune responses against the sequential polypeptides; (T-G-A-Gly)n, (T-A-G-Gly)n, (Phe-G-A-Gly)n and (Phe-A-G-Gly)n were studied in inbred guinea pigs and mice. Strain 13 guinea pigs responded to (Phe-G-A-Gly)n and (T-G-A-Gly)n whereas strain 2 guinea pigs responded to (T-A-G-GLY)n and (Phe-A-G-Gly)n. These responses which are linked to MHC, are only against the helical form of the polymers which have conformational determinants. Significant cross reactions at the humoral and T cell levels (PELS) are exhibited with the following reciprocal combinations: (Phe-G-A-Gly)n and (T-G-A-Gly)n; (T-A-G-Gly)n and (Phe-A-G-Gly)n. With mice, the polymers were shown to be T dependent with the following response patterns: mice of H-2b haplotype respond against (T-G-A-Gly)n; those of H-2b, f and r haplotypes respond against (T-A-G-Gly)n. There are no responders against (Phe-G-A-Gly)n and only mice of H-2f respond against (Phe-A-G-Gly)n. "Nonresponders" respond against the MBSA aggregates of all of these polymers. The Ir gene(s) controlling these T cell dependent H-linked responses mapped to the IA subregion. Antibody responses against (T-G-A-Gly) and (T-A-G-Gly) were quite variable, and were most marked in, F1 mice of (responder and nonresponder) and in backcross populations of (F1 x R) and (F1 x NR). However, the T cell proliferative responses performed with nylon wool purified T cells gave clear cut and predictable distinctions between "responders" and nonresponders and linkage with responding haplotype. Hypotheses advanced to explain these findings relate to the poor immunogenicity (antibody) of these polymers, which have a restricted number of repeating determinants, the B cell mitogenic properties of these polymers and the possible involvement of suppressor cells. The specificities of the humoral responses, i.e. cross reactions, were similar to those found in guinea pigs. However, in contrast to the guinea pig studies cross stimulation with structurally related polymers occurred only in those situations where the immunizing and "crossreacting" polymers were both immunogenic in mice of the same haplotype, i.e., (T-A-G-Gly)n and (Phe-A-G-Gly)n in mice of H-2f haplotypes.

Immune responses of inbred guinea pigs to the sequential polymer poly(L-Tyr-L-Ala-Gly): studies with the oligomers of the polymers

Synthetic known sequence polypeptides poly(Tyrosine-Glutamic acid-Alanine-Glycine) T-G-A-Gly), were found to be very immunogenic in responder inbred guinea pigs. Two and one-half micrograms were enough to elicit both humoral and cellular responses. Only the alpha-helical oligomers were immunogenic and were able to inhibit the homologous antigen-antibody reactions. The random polymers of comparable amino acid composition, i.e., poly(glutamic acid60alanine40) (GA), poly(glutamic acid50 tyrosin50) (GT), poly(glutamic acid60alanine30tyrosine10)(GAT10), did not inhibit. The antibodies against (T-G-A-Gly)n did not bind to the closely related known sequence polymer poly tyrosine-alanine-glutamic acid-glycine) (T-A-G-Gly)n or to the above random polymers. It is thus concluded that antibodies against (T-G-A-Gly)n are directed against conformational determinats.

Immune responses of outbred guinea pigs to the sequential polymer poly(L-Tyr-L-Glu-L-Ala-Gly): association of response to strain 13 histocompatibility locus

Outbred Hartley guinea pigs were immunized with the sequential polymer poly(L-Tyr-L-Glu-L-Ala-Gly) (T-G-A-Gly)n, the random copolymer poly(Glu50,Tyr50) (GT), and a low dose of dinitrophenylated guinea pig albumin (DNP-GPA). Only the guinea pigs that carry strain 13 histocompatibility antigen responded to these three antigens as measured by the antigen-binding assay and delayed skin reaction. The immune response (Ir) genes controlling responses to (T-G-A-Gly)n, GT, or DNP-GPA, were found to be distinctive genes. Nonresponder inbred strain 2 guinea pigs were able to produce anti(T-G-A-Gly)n antibodies when immunized with (T-G-A-Gly)n and methylated bovine serum albumin (MBSA) complex, although there was no delayed skin reaction and in vitro cultured lymphocytes did not respond. The in vitro response to (T-G-A-Gly)n of cultured lymphocytes from responder animals was inhibited by strain 2 antistrain 13 alloantisera but not the strain 13 anti-strain 2 alloantisera.

The prevalence and epidemiology of toxoplasmosis in Ontario

The results of testing 7060 human serum specimens obtained in the Province of Ontario, Canada, were analysed for the presence of antibodies to Toxoplasma gondii. Of these samples 38% were serologically positive at a titre of 1/16 or greater. The age-specific rates climbed from 2.7% in infants between 6 months and 1 year of age, to about 50% in individuals aged 25 years or over. Variations in prevalence were noted between different areas within the province and evidence is put forward to show that an inverse relation exists between urban size and toxoplasma prevalence. Seasonal and annual variations were not shown to be significant. On the basis of a very small sample of specimens, cat ownership not appear to cause a significant increase in the risk of acquiring this infection.

Streptococcus sanguis: a model in the application in immunochemical analysis for the in situ localization of bacteria in dental plaque

A review of the development of the serology of S sanguis has been presented. This species contains a group-specific antigen designated a, which appears to be a glycerol teichoic acid. It is suggested that this antigen be designated the Lancefield group H antigen. In addition, two major serotypes based on distribution of other surface antigens have been demonstrated. The grouping antiserums for S sanguis have been used to localize these bacteria in ultrastructural sections of intact dental plaque. The organisms appear antigens and seem to form pyramid-shaped microcolonies with the apex at the tooth surface and the base at the external surface of the plaque. The cells at the apex appear to have lost some surface antigens and seem to be older. The age and arrangement of the cells suggest that most plaque forms by cell division rather than by apposition of new cells from the oral cavity. If this is true, it is necessary to alter some current concepts regarding plaque development and possiby consider some different approaches to plaque control.

Unusual cell wall ultrastructure of Leptotrichia buccalis

Leptotrichia buccalis was examined by transmission electron microscopy. Its cell wall structure in generally compatible with that of gram-negative bacteria. However, the scale-like membranous folds associated with the external surface of the outer cell membrane appear to be sufficiently unusual to serve as a useful morphological criterion in the identification of L. baccalis cells.

An analysis of those components of Toxoplasma gondii responsible for delayed hypersensitivity reactions in mice

Testing of extracts of Toxoplasma gondii (RH strain) indicated that delayed hypersensitivity as manifested by delayed skin reactions and inhibition of macrophage migration was induced only by those fractions containing RNA.

The protective effect of milk diet on Toxoplasma gondii infection in mice

The effect of an all milk diet on resistance to Toxoplasmagondii infection in mice was studied. Mice fed an all milk diet were more resistant than conventionally fed mice to T. gondii. It was shown that this effect was due to a dietary deficiency para-aminobenzoic acid.

Immunoelectron microscopic identification and localization of Streptococcus sanguis with peroxidase-labeled antibody: localization of Streptococcus sanguis in intact dental plaque

Streptococcus sanguis has been localized ultrastructurally within intact dental plaque by means of an indirect technique which utilizes horseradish peroxidase-labeled antibody. The technique allows for complete diffusion of the reagents to all portions of the plaque specimens. Control procedures can be carried out on serial sections of plaque with a bacterial composition similar to that of the experimental specimen. The 30-mum-thick sections can be examined in the light microscope to localize areas specifically labeled with peroxidase prior to cutting ultra-thin sections for electron microscopy. This study demonstrated that specific bacteria can be localized within intact dental plaque. The results also indicated that S. sanguis grows in dental plaque as columnar shaped microcolonies perpendicular to the tooth surfaces. Growth appears to be by cell division rather than deposition of new cells at the surfaces. Despite their relatively good structural preservation, the cells in the deeper (older) layers of plaque appear to have lost some of their antigenic activity in comparison to the cells near the surface.

Immunoelectron microscopic identification and localization of Streptococcus sanguis with peroxidase-labeled antibody: localization of surface antigens in pure cultures

An indirect method of localizing antigens with horseradish peroxidase-labeled antibody was used to identify and localize surface antigens of Streptococcus sanguis at the ultrastructural level. An electron dense layer surrounding the cell wall could be distinguished without any additional electron microscope staining. This labeled layer represents an immune complex consisting of bacterial surface antigens, specific rabbit antisera, and peroxidase-labeled goat anti-rabbit globulins. Although with undiluted antisera slight cross-reactions occurred with S. salivarius and S. miteor (mitis), these could be readily distinguished from the more intense homologous reaction by their patchiness and the difference in distribution of the label. These cross-reactions were eliminated by appropriate dilutions of the antiserum. No cross-reactions occurred with S. mutans, S. faecalis, Actinomyces species, or Bacterionema, microorganisms wents indicated that horseradish peroxidase can become non-specifically adsorbed to the membrane of certain bacterial cells. Appropriate controls must, therefore, be included for localization of membrane associated antigens with horseradish peroxidase.