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Biomedical subjects

M Kilian

Publications and source records attributed to M Kilian.

At least 109 records · Page 6Linked to original sources
PubMed1991

Lack of cleavage of immunoglobulin A (IgA) from rhesus monkeys by bacterial IgA1 proteases.

Bacterial immunoglobulin A1 (IgA1) proteases cleaving IgA1 and secretory IgA1 molecules in the hinge region are believed to be important virulence factors. Previous studies have indicated that IgA of humans, gorillas, and chimpanzees are the exclusive substrates of these enzymes. In a recent study, IgA from the rhesus monkey was found to be susceptible to the IgA1 protease activity of Streptococcus pneumoniae. In an attempt to reproduce this observation, we found that neither five isolates of S. pneumoniae nor other IgA1 protease-producing bacteria representing different cleavage specificities caused cleavage of rhesus monkey IgA. Hence, the rhesus monkey does not appear to be a suitable animal model for studies of IgA1 proteases as virulence factors.

Amino Acid Sequence↗
PubMed1990

Haemophilus influenzae potentiates basophil histamine release possibly by its endotoxins.

Haemophilus influenzae and its extracellular products (EP) did not release histamine in leukocyte suspensions from normal individuals. However, the EP were found to enhance basophil histamine release triggered by anti-IgE and by the calcium ionophore A23187. Experiments with EP indicate that it is the content of endotoxins which is responsible for the potentiating effect. Removal of endotoxin from the EP thus completely abolished the potentiating effect, whereas inactivation of its protease and proteins by heat-treatment or by proteinase K did not change the potentiation. A reinforcement of mediator release by the extracellular products of H. influenzae might play a pathophysiological role in chronic obstructive pulmonary disease.

Basophils↗
PubMed1990

Endotoxin from Haemophilus influenzae enhances IgE-mediated and non-immunological histamine release.

Haemophilus influenza and its extracellular products (EP) did not release histamine from basophil leukocytes in cell suspensions from normal individuals, patients with chronic bronchitis or patients allergic to either house dust mite, grass pollen, cat dander or to their own bacteria. However, the EP was found to enhance their basophil histamine release. IgE-mediated histamine release was examined by stimulation of the cells with anti-IgE or the specific allergens, and non-immunological histamine release by stimulating the cells with the calcium ionophore A23187 or Staphylococcus aureus. In all the experiments EP caused a significant increase in the histamine release. When H. influenzae endotoxins were removed from the EP, the potentiating effect of EP was completely abolished, whereas heating (80 degrees C, 30 min) or treatment of EP with proteinase did not influence the potentiating effect. These results indicate that H. influenzae endotoxin potentiates histamine release caused by IgE-mediated reactions or by non-immunological mechanisms.

Adult↗
PubMed1990

Molecular aspects of immunoglobulin A1 degradation by oral streptococci.

Using a panel of 143 strains classified according to a novel taxonomic system for oral viridans-type streptococci, we reexamined the ability of oral streptococci to attack human immunoglobulin A1 (IgA1) molecules with IgA1 protease or glycosidases. IgA1 protease production was an exclusive property of all strains belonging to Streptococcus sanguis and Streptococcus oralis (previously S. mitior) and of some strains of Streptococcus mitis biovar 1. These are all dominant initiators of dental plaque formation. Degradation of the carbohydrate moiety of IgA1 molecules accompanied IgA1 protease activity in S. oralis and protease-producing strains of S. mitis biovar 1. Neuraminidase and beta-galactosidase were identified as extracellular enzymes in organisms of these taxa. By examination with enzyme-neutralizing antisera, four distinct IgA1 proteases were detected in S. sanguis biovars 1 to 3, S. sanguis biovar 4, S. oralis, and strains of S. mitis, respectively. The cleavage of IgA1 molecules by streptococcal IgA proteases was found to be influenced by their state of glycosylation. Treatment of IgA1 with bacterial (including streptococcal) neuraminidase increased susceptibility to protease, suggesting a cooperative activity of streptococcal IgA1 protease and neuraminidase. In contrast, a decrease in susceptibility was observed after extensive deglycosylation of the hinge region with endo-alpha-N acetylgalactosaminidase. The effector functions of IgA antibodies depend on the carbohydrate-containing Fc portion. Hence, the observation that oral streptococci may cleave not only the alpha 1 chains but also the carbohydrate moiety of IgA1 molecules suggests that the ability to evade secretory immune mechanisms may contribute to the successful establishment of these bacteria in the oral cavity.

Amino Acid Sequence↗
PubMed1990

Microflora associated with experimental root surface caries in humans.

This study describes the microflora from actively progressing root surface caries lesions, in which mineral loss had been determined by quantitative microradiography. The caries lesions were produced experimentally in root surface specimens from human molars inserted in lower partial dentures carried for 3 months by six elderly individuals. A total of 780 bacterial isolates were identified from 13 plaque samples, collected with a punch technique, and six dentin samples. The composition of the microflora showed distinct individual differences. The microflora from plaque samples associated with the highest mineral loss was dominated by either Actinomyces viscosus or a combination of mutans streptococci (serotypes c, d, and f) and Lactobacillus species (L. casei and L. brevis). Plaque from root surfaces with less pronounced mineral loss harbored a more complex microflora comprising gram-positive rods, mutans streptococci, Streptococcus mitis biovar 1, Veillonella spp., gram-negative rods, and low numbers of lactobacilli. In the latter samples, individual variations in the proportions of mutans streptococci (serotypes c, d, and g), Actinomyces species (A. viscosus and A. naeslundii), and Veillonella parvula biotypes were observed. These findings suggest that certain species or combinations of species are more cariogenic than others and that dominance of single acidogenic species in particular is conducive to high caries activity.

Aged↗
PubMed1990

Ability to bind salivary alpha-amylase discriminates certain viridans group streptococcal species.

A collection of 144 viridans group streptococcal strains recently characterized as part of a taxonomic study was examined for the ability to bind salivary alpha-amylase. This property was found in most strains of Streptococcus gordonii and Streptococcus mitis and in occasional strains of Streptococcus anginosus and Streptococcus salivarius. In contrast, all strains of Streptococcus sanguis, Streptococcus oralis, Streptococcus vestibularis, and Streptococcus mutans lacked alpha-amylase-binding capacity. A rapid and easy assay described in this paper may be an important supplementary test for identification of oral streptococci.

Bacteriological Techniques↗
PubMed1990

V factor-dependent members of the family Pasteurellaceae in the porcine upper respiratory tract.

A study was performed to obtain a better understanding of the diversity and ecology of members of the family Pasteurellaceae in the porcine respiratory tract. A collection of 132 V factor-dependent strains of Pasteurellaceae selected from porcine field isolates mainly from the respiratory tract were subjected to detailed characterization. In addition to the three hitherto recognized species Actinobacillus pleuropneumoniae, Haemophilus parasuis, and Haemophilus taxon "minor group," three distinct taxa were observed. Some of these taxa, which are provisionally designated taxa D, E, and F, would by traditional criteria be mistaken for H. parasuis but differed by several biochemical characteristics. To study the ecology of the V factor-dependent species, swabs from the nasal and oral cavities of 29 pigs were cultivated on selective and nonselective media. By studying approximately 30 isolates from each sample, the distribution and relative proportion of the individual taxa were determined. A. pleuropneumoniae was detected in samples from the tonsil areas of only two acutely ill animals. H. parasuis was isolated from the nasal cavities of four out of nine healthy pigs but from the oral cavities of only two animals. In contrast, taxon "minor group" and taxa D, E, and F were present in the oral cavities of the majority of pigs but were not detected in samples from their nasal cavities. The results indicate that all the observed V factor-dependent species of Pasteurellaceae except A. pleuropneumoniae, are members of the resident microflora of various mucosal surfaces of the porcine upper respiratory tract.

Animals↗
PubMed1990

Comparison of the initial streptococcal microflora on dental enamel in caries-active and in caries-inactive individuals.

This study compared the initial (4 h) microflora on enamel in 7 caries-active and in 7 caries-inactive adolescents. In both groups the microflora was dominated by streptococci which comprised 61 and 78% (median values) of the total viable counts in caries-active and caries-inactive individuals, respectively (p less than 0.01). Identification of a total of 700 streptococcal isolates according to a recently revised classification showed that the predominant streptococci belonged to the species Streptococcus oralis, Streptococcus mitis biovar 1, and Streptococcus sanguis. Early plaque from caries-inactive individuals differed from that of caries-active individuals by significantly higher proportions of S. sanguis (p less than 0.05) and IgA1 protease producing streptococci (p less than 0.05). In caries-active individuals, there was a tendency to elevated levels of S. mitis biovar 1 (p less than 0.10). In addition, caries-active individuals were colonized by significantly higher numbers of mutans streptococci on the enamel surfaces (p less than 0.01). However, in both groups Streptococcus mutans (serotype c) comprised less than or equal to 2% of the early streptococcal flora. Streptococcus gordonii, S. mitis biovar 2, and Streptococcus salivarius were present in low proportions and did not show differences in distribution that could be related to caries activity. The observed differences in the composition of the early streptococcal microflora may be a factor that governs the eventual cariogenic potential of dental plaque.

Adolescent↗
PubMed1989

Anti-inflammatory activity of human IgA antibodies and their Fab alpha fragments: inhibition of IgG-mediated complement activation.

The interaction of human IgA antibodies with the classical pathway of complement activation was investigated in a homologous human system, by means of two IgA1 and three IgG1 myeloma proteins having antibody activity against a defined antigen, staphylococcal alpha-toxin. In a solid-phase antigen-dependent C3b-binding ELISA system, the monoclonal IgG antibodies were previously shown to activate the classical complement pathway synergistically, resembling polyclonal IgG antibodies, whereas IgA antibodies were unable to activate complement by either pathway. In the present study, IgA antibodies were found to inhibit significantly the activation of complement initiated by antigen-bound polyclonal or mixed monoclonal IgG antibodies, in relation to the amount of IgA antibodies applied and bound to antigen. IgA1 myeloma proteins devoid of antigen-binding activity were without effect. Inhibition was independent of the ability of the IgA antibodies to compete against the IgG antibodies in binding to antigen, and was demonstrable with physiological concentrations of antibodies. Similar results were obtained with polyclonal serum IgA having antigen-binding activity. However, the binding of C1q to antigen-complexed IgG was inhibited only by a monoclonal IgA antibody that could compete against one of the three monoclonal IgG antibodies that bound C1q synergistically. This observation implied that at least two mechanisms were involved in the inhibition of C3b fixation. Fab alpha fragments of monoclonal IgA antibodies, obtained by cleavage with IgA1 protease from Haemophilus influenzae type b, were found to have a similar inhibitory effect on C3b fixation to the intact IgA1 antibodies. This observation supports the hypothesis that IgA1 proteases contribute to the invasive pathogenicity of certain mucosal bacteria, by cleaving secretory IgA1 antibodies to antigen-binding Fab alpha fragments, which are not only defective in mucosal defense properties, but which also protect the organisms from other immune effector systems, such as complement activation.

Antibodies, Monoclonal↗
PubMed1989

Distribution of immunoglobulin isotypes including IgA subclasses in adult, juvenile, and rapidly progressive periodontitis.

The plasma cell population in gingival biopsies from 3 groups of patients with adult, juvenile, and rapidly progressive periodontitis was characterized with respect to the distribution of individual immunoglobulin isotypes, including IgA subclasses, by paired immunofluorescence staining. The median ratios of IgG:IgA plasma cells in gingival connective tissue from the 3 groups were 2.7 (range 2.0-6.5), 3.0 (1.4-6.2), and 2.0 (1.2-4.0), respectively. Cells staining for intracellular IgM were found in low numbers in all biopsies (range 0.3-6.3% of all plasma cells). No statistically significant differences were observed between the 3 patient groups. In all 3 groups, the IgA plasma cell population was predominantly of the IgA1 isotype. One function of IgA seems to be to dampen inflammatory side-effects of other immune effector systems. The demonstrated predominance of IgA1 plasma cells indicates that the majority of IgA produced locally in gingivae of patients with periodontal diseases is susceptible to the IgA1-specific proteases excreted by important members of the disease-associated subgingival microflora. This may be an important factor in the apparently uncontrolled inflammation and tissue degradation taking place in the marginal periodontium during active periodontal disease.

Adolescent↗
PubMed1989

Cloning and sequencing of the immunoglobulin A1 protease gene (iga) of Haemophilus influenzae serotype b.

Secretion of immunoglobulin A1 (IgA1) proteases is a characteristic of Haemophilus influenzae and several other bacterial pathogens causing infectious diseases, including meningitis. Indirect evidence suggests that the proteases are important virulence factors. In this study, we cloned the iga gene encoding immunoglobulin A1 (IgA1) protease from H. influenzae serotype b into Escherichia coli, in which the recombinant H. influenzae iga gene was expressed and the resulting protease was secreted. Sequencing a part of a 7.5-kilobase DNA fragment containing the iga gene revealed a large open reading frame with a strongly biased codon usage and having the potential of encoding a protein of 1,541 amino acids and a molecular mass of 169 kilodaltons. Putative promoter and terminator elements flanking the open reading frame were identified. Comparison of the deduced amino acid sequence of this H. influenzae IgA1 protease with that of a similar protease from Neisseria gonorrhoeae revealed several domains with a high degree of homology. Analogous to mechanisms known from the N. gonorrhoeae IgA protease secretion, we propose a scheme of posttranslational modifications of the H. influenzae IgA1 protease precursor, leading to a secreted protease with a molecular mass of 108 kilodaltons, which is close to the 100 kilodaltons reported for the mature IgA1 protease.

Amino Acid Sequence↗
PubMed1989

Potentially pathogenic microorganisms in the oral cavity during febrile episodes in immunocompromised patients with haematologic malignancies.

The purpose of the study was to describe the occurrence of potentially pathogenic microorganisms during febrile episodes in haematologic patients, who had been treated with anti-neoplastic drugs within the previous 4 weeks. During a 9-month period 78 consecutive febrile episodes occurred in 46 patients who were examined daily. On day 1, before antibiotic treatment was started, members of the normal flora were found in 83%, Candida spp. in 72%, Enterobacteriaceae in 29%, Pseudomonas aeruginosa in 8%, Staphylococcus aureus in 14%, coagulase-negative staphylococci in 26% and enterococci in 17% of the febrile episodes. During the subsequent antibiotic treatment, the prevalence of members of the normal oral flora was markedly reduced from day 1 (83%) to day 7 (6%), and the normal flora was replaced by potentially pathogenic microorganisms. A rise was found in the prevalences of Candida spp. (from 72 to 92%) and coagulase-negative staphylococci (from 26 to 49%) from day 1 to day 4. The prevalences of Enterobacteriaceae and P. aeruginosa showed no day-to-day changes, and were not different in patients hospitalized for more or less than 24 h prior to inclusion into the study, suggesting that their detection was not due to acquisition during hospitalization or antibiotic treatment. The oral occurrence of species of microorganisms regularly found in septicaemia, suggests that the oral cavity may play a role as a port of entry of septicaemia in patients with haematologic malignancies.

Adult↗
PubMed1988

Activation energy of sulfate ion transport across methylated human erythrocyte membranes.

Activation energy EA of the sulfate ions transport process across human erythrocyte membranes modified by reductive methylation has been measured. It has been found that exhaustive reductive methylation (3 times) with formaldehyde and borohydride inhibits the sulfate-equilibrium exchange, by a maximum of about 40%. However, methylation has no measurable effect on activation energy, since the evaluated EA values for control and methylated cells remain the same within the experimental error range.

Biological Transport, Active↗
PubMed1988

Limited diversity of the immunoglobulin A1 protease gene (iga) among Haemophilus influenzae serotype b strains.

Immunoglobulin A1 (IgA1) proteases are thought to be important virulence factors in certain bacterial infections, including meningitis, and may have potential usage in vaccines. In this study, we compared the locations of EcoRI, BamHI, and PstI restriction endonuclease sites in the IgA1 protease gene (iga) region of whole-cell DNA from 76 Haemophilus influenzae strains. The analysis was performed by using isolated fragments of the cloned iga gene, which encodes the IgA1 protease originating from a H. influenzae serotype d strain, as probes in Southern blot experiments. All strains, including three without detectable IgA1 protease activity, had DNA sequences with a high degree of homology to the iga probes. The numbers and sizes of the DNA fragments hybridizing with the probes indicated that only three strains, none of which was of serotype b, had more than one iga gene. The iga restriction fragment length patterns of 60 clinical isolates of serotype b were of only four distinct types, which correlated with previously observed clusters of multilocus genotypes (electrophoretic types). This correlation supports the concept of the clonal population structure of H. influenzae. Three of the iga gene restriction types, which appear to represent 98% of the H. influenzae serotype b population, encode IgA1 proteases that were inhibited by antisera to any one of these types and therefore could form the basis for the development of a vaccine against H. influenzae meningitis.

Antibodies, Bacterial↗