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Query: UMLS:C0348321 (Haemophilus)
 15,372 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Normal serum IgA and secretory IgA (sIgA) of subclass IgA1 were isolated from pooled human serum and milk, respectively. They were tested for their susceptibility to bacterial IgA proteases from Haemophilus influenzae, Streptococcus pneumoniae, Neisseria gonorrhoeae, and Neisseria meningitidis that cleave IgA of only the IgA1 subclass. They were also tested for susceptibility to a novel IgA-protease from Clostridium ramosum that cleaves IgA of the IgA1 as well as the IgA2 subclass of the A2m(1) allotype. Both normal serum IgA1 and sIgA1 exhibited resistance to most IgA proteases. The one exception was the IgA protease from C. ramosum which readily cleaved both the serum IgA1 and sIgA1 into Fab and Fc fragments. Secretory component (SC) had nothing to do with the resistance of these IgAs. The resistance of these IgAs to most of the IgA proteases was found to be due to their enzyme-neutralizing antibody activity, since the Fab but not the Fc fragment of sIgA1 showed enzyme-inhibitory activity against these IgA proteases. Similar enzyme-neutralizing antibody activity was found in the pepsin-digested normal serum IgG-(Fab')2 fragment. These results indicate that the induction of the enzyme-neutralizing antibodies against the bacterial IgA proteases took place not only in mucosal sIgA but also in serum IgA and IgG. No enzyme-neutralizing antibody activity against the novel IgA-protease of C. ramosum was detected in any immunoglobulin preparations used in the present study or in the serum of a patient who carries the IgA protease-producing strain of C. ramosum in his feces.
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PMID:Resistance of normal serum IgA and secretory IgA to bacterial IgA proteases: evidence for the presence of enzyme-neutralizing antibodies in both serum and secretory IgA, and also in serum IgG. 312 62

The structural gene for immunoglobulin A protease (iga) from Haemophilus influenzae serotype d was cloned in pBR322. The gene was used as a probe for Southern hybridization analysis of chromosomal DNA from the five other H. influenzae serotypes (a, b, c, e, and f). In most cases strains from a single serotype exhibited a distinct pattern of restriction fragment(s) homologous to the iga gene probe which was unique for that serotype. Serotype f strains were unique in that they gave two distinct patterns of homologous restriction fragments which correlated well with the production of two different protease types by members of this group. An iga mutant of H. influenzae serotype d was isolated by introducing a 4-base-pair insertion into the cloned iga gene and using the altered DNA for transformation of an H. influenzae recipient. The resulting iga- mutant produced no immunoglobulin A protease but was otherwise indistinguishable from its iga+ parent in growth characteristics. Transformation of mutant cells with chromosomal DNA isolated from either a serotype d or a serotype c strain gave rise to iga+ transformants. Those obtained with serotype d DNA produced a type 1 protease, whereas those obtained with serotype c DNA produced either a type 1 protease (characteristic of serotype d) or a type 2 protease (characteristic of serotype c). Southern analysis of the latter transformants, using the iga gene probe, indicated that the type 1 transformants had a serotype d pattern of restriction fragments whereas the type 2 transformants had either a serotype c or a novel pattern of restriction fragments. These results indicate that there is considerable homology between the iga genes of the various serotypes and that the homologous sequences identified with the serotype d probe are the immunoglobulin A protease-coding sequences in each case.
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PMID:Physical and genetic analysis of DNA regions encoding the immunoglobulin A proteases of different specificities produced by Haemophilus influenzae. 388 44

IgA proteases were estimated in a turbid aqueous two-phase system with 10% polyethylene glycol-Tris buffer, where IgA spontaneously concentrates in microscopic spherical particles (less than 1 micron). After enzymatic cleavage of IgA into Fab alpha and Fc alpha fragments, these fragments are soluble and decreasing turbidity is observed. The reaction may be followed by conventional spectrophotometry. In this manner, IgA proteases may be estimated in 10 min. Examples of the utility of the method are given with results from inhibitor studies, estimation of Km and purification of IgA protease from Haemophilus influenzae.
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PMID:Bacterial immunoglobulin A proteases monitored by continuous spectrophotometry. 389 49

Haemophilus pleuropneumoniae, the etiological agent of porcine contagious pneumonia, was examined for the ability to produce an immunoglobulin A (IgA) protease specific for porcine IgA. No IgA protease activity against either porcine or human IgA was detected. Furthermore, no sequence homology was found between H. pleuropneumoniae chromosomal DNA and the gene which specifies IgA protease in Haemophilus influenzae.
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PMID:Examination of Haemophilus pleuropneumoniae for immunoglobulin A protease activity. 632 57

The production of immunoglobulin A (IgA) protease is a potentially useful marker in differentiating pathogenic from nonpathogenic species of clinical isolates; however, current quantitative assay methods are too tedious for routine application. A simple quantitative method was developed to screen clinical isolates for IgA protease production. This method is based on the specificity of reaction between IgA and alpha chain-specific antiserum in an immunochemistry analyzer (Beckman Instruments, Inc., Brea, Calif.). Colonies of IgA protease producers (Streptococcus sanguis, Streptococcus pneumoniae, Neisseria gonorrhoeae, Neisseria meningitidis, and Haemophilus influenzae) were picked from solid media, transferred to brain heart infusion containing IgA1, and incubated at 37 degrees C for at least 2 h to provide a detectable decrease in IgA concentration. The standard deviation for randomly picked colonies within a species was about +/- 15%. Several IgA protease-negative species caused no detectable reduction in the IgA content of the system. The specificity of the IgA measurement eliminates the requirements for extensive purification and radiolabeling of substrate and provides the basis for a well-defined IgA protease activity unit (micrograms of IgA1 cleaved per minute per milliliter of culture).
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PMID:Quantitative screening of clinical isolates for immunoglobulin A protease production. 635 34

The characteristics and functions of microbial IgA proteases are reviewed. These enzymes represent a structurally heterogeneous group of proteins that are secreted into the extracellular environment by bacteria capable of causing human disease. The IgA proteases, which vary in their requirements for metal ions, are neutral endopeptidases whose role in the infectious process is not known but whose pronounced substrate specificity for human proteins of the IgA1 subclass has repeatedly been demonstrated. As reagents, the IgA proteases are useful in cleaving IgA molecules to yield intact Fc alpha and Fab alpha fragments that will allow the study of the structure and function of the two large regions of IgA immunoglobulin proteins. The role, if any, of these enzymes in promoting infection by pathogenic members of the genera Neisseria, Hemophilus, and Streptococcus is not known, although the secretory immune system is primarily mediated by antibodies of the IgA isotype, among which are IgA1 subclass proteins, and these proteins are susceptible to cleavage by IgA protease. The determination of the role of these enzymes in the pathogenesis of human infection must await clearer understanding of antigenicity and antibody function at secretory sites and of the relative roles of the two subclasses of human IgA in immune defense.
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PMID:Secretory immunity and the bacterial IgA proteases. 679 82

Haemophilus influenzae is one of five bacterial species known to produce IgA proteases, enzymes that specifically cleave the human IgA1 heavy chain. Strains of H. influenzae produce three distinct types of IgA proteases that cleave different peptide bonds within the IgA1 hinge region. Type 1 protease cleaves the prolyl-seryl bond at position 231-232; type 2 protease cleaves the prolyl-threonyl bond at position 235-236, the same bond attacked by Neisseria gonorrhoeae and Neisseria meningitidis type 2 proteases. Type 3 protease yields a unique double Fd cleavage pattern; the exact peptide bonds cleaved have not been determined. The type of protease produced correlates with the serotype, but not with the biotype, of the isolate; serotypes A, B, D, and F produce primarily type 1 protease, whereas serotypes C and E produce only type 2 enzyme. Each nontypable strain yields one of the three protease types. These data further extend our knowledge of the extreme specificity of the IgA proteases and suggest that IgA protease type may be useful in the taxonomy and epidemiology of H. influenzae.
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PMID:Relationship between the specificity of IgA proteases and serotypes in Haemophilus influenzae. 680 43

Streptococcus pneumoniae and Haemophilus influenzae are among the most common bacterial pathogens responsible for respiratory tract infections in otherwise healthy humans. Thirty-six strains of S. pneumoniae, 62 strains of H. influenzae, six hospital-acquired respiratory pathogens, and a strain of Streptococcus pyogenes were examined for production of IgA protease, a bacterial enzyme whose only known substrate is human IgA1. IgA protease was produced by 100% of the isolates of S. pneumoniae and 98% of the isolates of H. influenzae. The enzyme from both species cleaved human serum and secretory IgA1 proteins, but not human IgA2, IgG, or human serum albumin. None of the hospital-acquired pathogens had detectable IgA protease activity, a finding indicating that the production of this enzyme distinguishes S. pneumoniae and H. influenzae from the opporunistic respiratory pathogens.
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PMID:Specific proteolysis of human IgA by Streptococcus pneumoniae and Haemophilus influenzae. 698 25

The human gastric bacterial pathogen Helicobacter pylori has been implicated in type B gastritis, peptic ulceration and gastric adenocarcinoma. Here we report on the cloning and genetic characterization of an H. pylori gene named vacA, which encodes the vacuolating cytotoxin VacA, a novel type of antigenic bacterial toxin that induces the formation of intracellular vacuoles in epithelial cells. The vacuolating cytotoxin activity is expressed by a subset of clinical isolates (Vac+), all of which produce the 87 kDa cytotoxin antigen, but strains which produce neither the activity nor the cytotoxin protein (Vac-) also carry the gene. Isogenic H. pylori mutants in vacA generated by transposon shuttle mutagenesis produce neither the VacA antigen nor a vacuolating activity in a cell culture model. The vacA gene itself encodes a precursor protein of 139.6 kDa consisting of a 33-amino acid signal sequence, the 87 kDa cytotoxin and a 50 kDa C-terminal domain with features typical of a bacterial outer membrane protein. The VacA precursor shows no significant primary sequence homology with any previously reported protein, but its structural organization closely resembles the IgA protease-type of exoprotein produced by pathogenic Neisseriae and Haemophilus species. Our current data support a model for secretion of the cytotoxin through the two bacterial membranes which involves the 50 kDa domain for outer membrane translocation with subsequent proteolytic cleavage and release of the mature 87 kDa cytotoxin into the extracellular environment.
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PMID:Genetic analysis of the Helicobacter pylori vacuolating cytotoxin: structural similarities with the IgA protease type of exported protein. 805 55

The pathogenic, Gram-negative bacteria, Neisseria gonorrhoeae, Neisseria meningitidis and Haemophilus influenzae, secrete immunoglobulin A1 proteases into their extracellular surroundings. An extraordinary feature in the secretory pathway of these putative virulence factors is a self-directed outer membrane transport step allowing the proteins to be secreted autonomously, even from foreign Gram-negative host cells like Escherichia coli. Here we summarize recent achievements in the understanding of IgA protease outer membrane translocation.
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PMID:The secretion pathway of IgA protease-type proteins in gram-negative bacteria. 814 98


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