Outer membrane proteins of Actinobacillus actinomycetemcomitans and Haemophilus aphrophilus studied by SDS-PAGE and immunoblotting

Role of OmpA1 and OmpA2 in Aggregatibacter actinomycetemcomitans and Aggregatibacter aphrophilus serum resistance

Aggregatibacter actinomycetemcomitans and Aggregatibacter aphrophilus belong to the HACEK group of fastidious Gram-negative organisms, a recognized cause of infective endocarditis. A. actinomycetemcomitans is also implicated in aggressive forms of periodontitis. We demonstrated that A. aphrophilus strains, as A. actinomycetemcomitans are ubiquitously serum resistant. Both species encode two Outer membrane protein A paralogues, here denoted OmpA1 and OmpA2. As their respective pangenomes contain several OmpA1 and OmpA2 alleles, they represent potential genotypic markers. A naturally competent strain of A. actinomycetemcomitans and A. aphrophilus, respectively were used to elucidate if OmpA1 and OmpA2 contribute to serum resistance. Whereas OmpA1 was critical for survival of A. actinomycetemcomitans D7SS in 50% normal human serum (NHS), serum resistant ompA1 mutants were fortuitously obtained, expressing enhanced levels of OmpA2. Similarly, OmpA1 rather than OmpA2 was a major contributor to serum resistance of A. aphrophilus HK83. Far-Western blot revealed that OmpA1^AA, OmpA2^AA, and OmpA1^AP can bind to C4-binding protein, an inhibitor of classical and mannose-binding lectin (MBL) complement activation. Indeed, ompA1 mutants were susceptible to these pathways, but also to alternative complement activation. This may at least partly reflect a compromised outer membrane integrity but is also consistent with alternative mechanisms involved in OmpA-mediated serum resistance.

Aggregatibacter actinomycetemcomitans Growth in Biofilm versus Planktonic State: Differential Expression of Proteins

Aggregatibacter actinomycetemcomitans (Aa) is a pathogenic bacterium residing in the subgingival plaque biofilm strongly associated with the pathogenesis of periodontitis. The aim of this investigation was to study the protein differential expression of Aa when growing on biofilm compared with planktonic state using proteomic analysis by the 2D-DIGE system. Eighty-seven proteins were differentially expressed during biofilm growth (1.5-fold, p < 0.05), with 13 overexpressed and 37 down-expressed. Those repressed were mainly proteins involved in metabolism, biosynthesis, and transport. The overexpressed proteins were outer membrane proteins (OMPs) and highly immunogenic proteins such as YaeT (OMP), FtsZ, OMP39, OMP18/16, the chaperone GroEL, OMPA, adenylate kinase (Adk), and dihydrolipoamide acetyltransferase. The enrichment fractions of the OMPs from biofilm and planktonic states were obtained, and these proteins were analyzed by Western blotting with human serum from a periodontitis patient and one healthy control. These immunogenic proteins overexpressed in the biofilm may represent candidate virulence factors.

Heterogeneity of Surfaces of Subgingival Bacteria as Detected by Zeta Potential Measurements

Porphyromonasgingivalis, Prevotella intermedia, and Actinobacillus actinomycetemcomitans (A.a.) are Gram-negative bacteria which are implicated in various forms of periodontal disease. The Gram-positive Peptostreptococcus micros may also play an important role. For investigation of the possible adhesion and colonization mechanisms of these organisms, the charge properties of the outermost layers of bacterial cell surfaces were studied through the measurement of zeta potentials at various pH values. Eleven fresh clinical isolates, representing the four species, and one laboratory strain, P. gingivalis W83, were examined. Eleven of the 12 strains displayed heterogeneity with respect to pH-dependent zeta potentials. Within single cultures of each of these strains, two distinct populations of cells were found, one which was more negatively charged than the other. For the Gram-negative strains, the more negatively charged subpopulation was in the majority, while the P. micros strains appeared to be composed mainly of a less-negatively-charged subpopulation. Vesicles prepared from two strains displayed the same pH dependence and heterogeneity of zeta potentials as the parent cells. An A.a. strain which was passaged several times in fluid medium had lost its fimbriae and became homogeneous with respect to charge.

Immunoproteomics of Actinobacillus actinomycetemcomitans outer-membrane proteins reveal a highly immunoreactive peptidoglycan-associated lipoprotein

In a search for novel bioactive cell surface structures of periodontal pathogens, it was found that sera from two patients with Actinobacillus actinomycetemcomitans-associated infections reacted strongly at 17 kDa on immunoblots of A. actinomycetemcomitans outer-membrane protein (OMP) preparations. The 17 kDa antigen was also recognized by anti-CsgA (Escherichia coli curli major subunit) antibody. The 17 kDa A. actinomycetemcomitans protein was identified as peptidoglycan-associated lipoprotein (PAL; AaPAL) by two-dimensional immunoblotting and subsequent sequence analysis by mass spectrometry and bioinformatics tools. AaPAL was an OMP and a lipoprotein, and it had an OmpA-like domain. In a group of middle-aged subjects (n = 26), serum reactivity to AaPAL was associated with the presence of periodontitis but not with the oral detection of A. actinomycetemcomitans. Both human sera and rabbit antisera against three different types of antigens, the gel-purified AaPAL, A. actinomycetemcomitans whole-cell antigens, and CsgA, recognized putative PALs of oral haemophili in addition to AaPAL. The results demonstrated that the novel AaPAL is a conserved bacterial lipoprotein. It is expressed in vivo and is strongly immunoreactive. The antigenic cross-reactivity found between AaPAL and oral haemophili may enhance local and systemic immuno-inflammatory reactions in periodontitis.

Identification of six major outer membrane proteins from Actinobacillus actinomycetemcomitans

We have identified six major sarcosyl-insoluble outer membrane proteins (Omp) of Actinobacillus actinomycetemcomitans Y4, and designated them as Omp100, Omp64, Omp39, Omp29, Omp18 and Omp16 according to the molecular mass. A similar N-terminal sequence was found in the first 15 amino acid residues of Omp16 and Omp18. The N-terminal sequence of Omp29 matched perfectly with the sequence previously identified. We cloned and determined the DNA sequences of three complete genes encoding Omp100, Omp64 and Omp18/16, and one incomplete gene encoding Omp39. Each Omp revealed homologies with some bacterial virulence factors responsible for adhesion, invasion, serum resistance, or protein antigenicity. Serum from patients with periodontitis suspected to be related to A. actinomycetemcomintans infection strongly reacted with Omp100, Omp29 and Omp16 as did serum from mice immunized with A. actinomycetemcomitans Y4 whole bacteria. These findings suggest that Omps of A. actinomycetemcomitans can be associated with periodontal disease.

Immunodominant antigens in periodontal disease: a real or illusive concept?

The humoral arm of the immune system provides protection from many medically significant pathogens. The antigenic epitopes of the pathogens which induce these responses, and the subsequent characteristics of the host response, have been extensively documented in the medical literature, and in many cases have resulted in the development and implementation of effective vaccines or diagnostic tests. There is a substantial body of literature on the humoral immune response in periodontal disease, which is targeted at micro-organisms present within periodontal pockets. However, the significance and specificity of the immune response in periodontal disease have proved difficult to elucidate, due to the large number of potential pathogens in the plaque biofilm and the apparent commensal nature of many of these opportunistic pathogens. This review addresses our current knowledge of the approaches and strategies which have been used to elucidate and examine the concept of immunodominant antigens in medical infections and, more recently, periodontal disease. An identification/understanding of the immunodominant antigens would be informative with respect to: (i) the relative importance of the implicated pathogens, (ii) new approaches to immunological diagnosis, (iii) specific bacterial virulence determinants, (iv) natural protective responses, and (v) the selection of potential vaccine candidate antigens. We conclude that immunodominance of antigens in periodontal disease may be relevant to our understanding of periodontal disease pathogenesis, but due to the complexity and diversity of the 'pathogenic microbial ecology', it is currently an enigmatic topic requiring a multidisciplinary approach linking clinical, microbiological, and immunological investigations. We also conclude, after assessing the literature available on the topic of immunodominance, that it is a term that, if used, must be clearly defined and understood, since it is often used loosely, leading to a general misinterpretation by readers of oral and medical literature.

Antigenic specificity of gingival crevicular fluid antibody to Actinobacillus actinomycetemcomitans

Elevated antibody levels to periodontopathogens in GCF have been identified and used as support for local antibody synthesis in periodontitis. This study examined both cross-sectional and longitudinal GCF samples for the antigenic specificity of antibody in the fluid. GCF samples were collected from each tooth of 27 periodontitis patients infected with A. actinomycetemcomitans. Levels of IgG antibody in the GCF were assessed by means of an ELISA and compared with serum for determination of local elevations. A proportion of those GCF samples that exhibited significantly elevated antibody were examined by Western immunoblotting to outer membrane antigens from A. actinomycetemcomitans. Homologous sera were also examined for comparison of antibody specificities. Of the sites with elevated IgG antibody, 87% were colonized by A. actinomycetemcomitans; however, 46% of sites with A. actinomycetemcomitans infection did not have elevated antibody. Cross-sectional studies identified a 78 to 100% agreement between the antibody specificities in GCF and those in serum. Additionally, patterns of antibody reactivity in both GCF and serum in the subjects were often very distinctive. Longitudinal alterations in GCF antibody were examined in 15 patients through a monitoring interval of up to 2 years and showed a general conservation of specificities. However, 7/15 patients exhibited a definite acquisition of different antibody specificities during the monitoring. These results describe a relationship between elevated local antibody and A. actinomycetemcomitans infection. Furthermore, the antibody specificities in serum appear to reflect generally the local response to this pathogen.

Altered antigenicity is seen in the lipopolysaccharide profile of non-serotypeable Actinobacillus actinomycetemcomitans strains

Non-serotypeable Actinobacillus actinomycetemcomitans strains may be derived from the serotypeable ones. In the present study, we compared the outer membrane proteins (OMPs) and lipopolysaccharides (LPSs) of serotypeable and non-serotypeable A. actinomycetemcomitans strains (n=24) of the same genotype in the same subject (n=6) to find out if alterations on the cell-surface contribute to the non-serotypeability. Serotypeable and non-serotypeable A. actinomycetemcomitans strains showed great similarity in the OMP patterns both within and between subjects. Using serotype-specific antisera, clear immunoblotting LPS profiles in the O-antigenic region were seen in serotype b and c strains but not in non-serotypeable strains from the same subjects. The results suggest that changes in LPS lead to the altered antigenicity of non-serotypeable A. actinomycetemcomitans strains.

Protective effect of serum antibodies against a 110-kilodalton protein of Actinobacillus actinomycetemcomitans following periodontal therapy

Thirty-four adult patients with untreated periodontitis were randomly assigned to receive full mouth scaling alone or scaling with an adjunctive antimicrobial therapy, both followed by supportive periodontal therapy. At 24 months, specific serum immunoglobulin A (IgA), IgG and IgG subclass antibody reactivities against a 110-kDa protein of Actinobacillus actinomycetemcomitans were assessed by Western blot. In patients harboring A. actinomycetemcomitans intraorally, the IgG4 antibody reactivity against the 110-kDa protein of A. actinomycetemcomitans was associated with significantly increased survival rates of teeth and of sites not exhibiting 2 mm or more of probing attachment loss. The same trend was found for IgG3 and IgG2 antibody reactivities, but it was statistically insignificant. No association with clinical treatment outcome was observed for IgA, IgG and IgG1 antibody reactivities. The results indicated that systemic IgG4 antibody reactivity against the 110-kDa protein of A. actinomycetemcomitans may have a protective effect against periodontal disease progression in patients harboring A. actinomycetemcomitans and receiving periodontal therapy.

Cloning of the gene encoding the Actinobacillus actinomycetemcomitans serotype b OmpA-like outer membrane protein

The gene encoding an outer membrane protein A (OmpA)-like, heat-modifiable Omp of Actinobacillus actinomycetemcomitans ATCC 43718 (strain Y4, serotype b) was cloned by a PCR cloning procedure. DNA sequence analysis revealed that the gene encodes a protein of 346 amino acid residues with a molecular mass of 36.9 kDa. The protein expressed by the cloned gene reacted with a monoclonal antibody to the previously described 29-kDa Omp (Omp29) of strain Y4. This monoclonal antibody reacted specifically with Omp29 of A. actinomycetemcomitans (serotype b), but not with any Omp of Escherichia coli, including OmpA. This protein exhibited characteristic heat modifiability on sodium dodecyl sulfate-polyacrylamide gels, showing an apparent molecular mass of 29 kDa when unheated and a mass of 34 kDa when heated. The N-terminal amino acid sequence of the protein expressed in E. coli perfectly matched those deduced from the purified Omp29 of strain Y4. The deduced amino acid sequence of the gene coding for Omp29 from serotype b matched completely (except for valine at position 321) that of a recently reported omp34 gene described for A. actinomycetemcomitans serotype c (NCTC 9710). Because of the conserved nature of the gene within these serotypes, we designated the gene described herein from serotype b as omp34.

Binding of the capsule-like serotype-specific polysaccharide antigen and the lipopolysaccharide from Actinobacillus actinomycetemcomitans to human complement-derived opsonins

We investigated the molecular mechanism of resistance of Actinobacillus actinomycetemcomitans to complement-dependent chemiluminescence response by human polymorphonuclear leukocytes. Whole cells of serotype b-specific polysaccharide antigen-defective mutants ST2 and ST5 were constructed by inserting transposon Tn916 into A. actinomycetemcomitans strain Y4. These strains induced strong chemiluminescence response by human polymorphonuclear leukocytes and markedly bound to human complement-derived opsonins. In contrast, strain Y4 induced weak chemiluminescence response and weakly bound to complement-derived opsonins. The biosensor analysis revealed that lipopolysaccharide from strain Y4 strongly bound to human C3b, but serotype b-specific polysaccharide antigen did not. The serotype b-specific polysaccharide antigen molecule might sterically hinder the interaction between complement-derived opsonins and lipopolysaccharide to reduce complement-dependent chemiluminescence response by human polymorphonuclear leukocytes.

Molecular characterization of an outer membrane protein of Actinobacillus actinomycetemcomitans belonging to the OmpA family

The major outer membrane protein (OMP) of Actinobacillus actinomycetemcomitans is an OmpA homolog that demonstrates electrophoretic heat modifiability. The gene encoding this protein was isolated from a genomic library of A. actinomycetemcomitans NCTC 9710 by immunoscreening with serum from a patient with localized juvenile periodontitis. Expression of the cloned gene in Escherichia coli and subsequent Western blot analysis revealed a protein with an approximate molecular mass of 34 kDa. The amino acid sequence predicted from the cloned gene demonstrated that the mature protein had a molecular mass of 34,911 Da and significant identity to members of the OmpA family of proteins. We have named the major OMP of A. actinomycetemcomitans Omp34, and its corresponding gene has been named omp34.

Extracellular 37-kDa antigenic protein from Actinobacillus actinomycetemcomitans induces TNF-alpha, IL-1 beta, and IL-6 in murine macrophages

The extracellular antigens of Actinobacillus actinomycetemcomitans Y4 (serotype b) contain a 37-kDa protein which is a major target for IgGs from patients suffering from severe alveolar bone loss. Since the 37-kDa protein has not been studied sufficiently, our investigation focused on its characteristics, e.g., its localization, specificity, and whether it directly stimulates macrophages to produce cytokines. The 37-kDa protein was purified from the culture supernatant of the Y4 strain by means of chromatofocusing and gel filtration. The 37-kDa protein is a unique glycoprotein which forms immune complexes with monoclonal antibodies against rhamnose-fucose polysaccharide. Patients with A. actinomycetemcomitans-associated periodontitis had higher antibody titers to the purified 37-kDa protein than healthy subjects (p < 0.001). Anti-37-kDa protein antibodies recognized a 37-kDa band in the cytosolic, ribosomal, and total membrane fractions from Y4 cells. Extracellular substances from other strains of A. actinomycetemcomitans (serotypes a and c) also reacted in the Western blots, but Haemophilus spp. or several periodontopathic bacteria did not. These results suggested that the 37-kDa protein is a cytosolic protein that is passed through the cell membrane, and its protein portion is specific for A. actinomycetemcomitans but common to serotypes. This protein induced Il-1 beta, Il-6, and TNF-alpha release from murine macrophages. The Il-6-inducing activity of the 37-kDa protein was higher than that of LPS. These findings suggested that the 37-kDa protein which is released from live cells plays a role in A. actinomycetemcomitans-associated periodontitis, as antigen inducing the release of inflammatory cytokines which are associated with alveolar bone loss.

Specific antibody reactivity against a 110-kilodalton Actinobacillus actinomycetemcomitans protein in subjects with periodontitis

The purpose of the present study was to determine the serum immunoglobulin A (IgA), IgM, and IgG reactivities against proteins of Actinobacillus actinomycetemcomitans in patients with periodontitis. Serum samples from 20 patients with early-onset periodontitis, 20 patients with adult periodontitis, and 20 age- and sex-matched healthy controls were assessed by immunoblot analysis. IgG antibody reactivity against a sarcosyl-insoluble 110-kDa protein of A. actinomycetemcomitans was detected in 65 and 45% of patients with early-onset periodontitis and adult peritonitis, respectively, and IgA antibodies against this protein were found in 70 and 55% of these patients, respectively. However, control subjects showed no IgG reactivity, and IgA antibodies against the sarcosyl-insoluble 110-kDa protein were detected in only 5% of the patients (P < 0.05). There was no IgM antibody reactivity against this protein in any of the diseased or healthy subjects. The sensitivity and specificity of serum IgA antibody reactivity against the 110-kDa protein in detecting subgingival A. actinomycetemcomitans infection, as determined by PCR, were 77 and 66%, respectively. The results of the study indicated that the sarcosyl-insoluble 110-kDa protein is a potential candidate for use in the serodiagnosis of periodontal disease.

Molecular characterization of a 40-kDa outer membrane protein, FomA, of Fusobacterium periodonticum and comparison with Fusobacterium nucleatum

The 40 kDa-outer membrane protein FomA of Fusobacterium periodonticum ATCC 33693 was found to exhibit heat modifiable properties, typical for a porin, and N-terminal sequencing indicated a close relationship to the porin FomA of Fusobacterium nucleatum. A polymerase chain reaction approach was therefore applied for sequencing the fomA gene of F. periodonticum, and nucleotide and deduced amino acid sequences were aligned and compared with the corresponding sequences of different strains of F. nucleatum. In all strains we found a common protein upstream of the fomA gene. The noncoding area upstream of the putative -35 region of the F. periodonticum fomA gene exhibited little sequence similarity with the F. nucleatum gene. The transcriptional unit of FomA, on the other hand, was very similar, with the similarities concentrated in domains that were interspersed with hypervariable regions. A topology model was made and compared with those made for F. nucleatum. This indicated that the great similarities reside in the membrane-spanning segments of the protein, while most cell surface exposed loops were hypervariable. The results strongly support the proposed model for FomA and also indicate that these taxa are related but on a lower level than the subspecies level. The codon usage of F. periodonticum is comparable to that of F. nucleatum, and the triplet AGA is the only codon used for arginine.

Longitudinal dynamics of infection and serum antibody in A. actinomycetemcomitans periodontitis

OBJECTS

This report describes one of the first prospective studies delineating the relationship between infection, host antibody responses and disease exacerbations and remissions in a distinct subset of periodontitis patients infected with A. actinomycetemcomitans.

DESIGN

The design of this longitudinal study included visits for each patient approximately every 2 months for up to 3 years.

SUBJECTS AND METHODS

Subjects (n=51) included 16 adult periodontitis (AP) and 11 early-onset periodontitis (EOP) patients with elevated serum IgG antibody to A. actinomycetemcomitans and infection with this microorganism, 12 AP patients with normal levels of anti-Aa antibody, and 12 normal subjects. MEASUREMENT OUTCOMES: Clinical parameters included a gingival index, plaque index, bleeding on probing, pocket depth, and attachment level. Disease activity was defined as loss of attachment during the monitoring intervals. Serum IgG, IgM and IgA antibody to A. actinomycetemcomitans Y4 (serotype b) was quantitated using an ELISA. Subgingival plaque samples were examined for A. actinomycetemcomitans using colony immunoblotting. Human serum IgG antibody specificities to outer membrane antigens (OMA) of A. actinomycetemcomitans Y4 were determined using Western immunoblotting.

RESULTS

A. actinomycetemcomitans-infected AP patients had a higher frequency of teeth infected when compared to the EOP patients. However, the EOP patients exhibited a trend for higher levels of A. actinomycetemcomitans in those teeth that were infected. Active disease patients demonstrated a significantly greater frequency of infected sites, as well as significant elevations in the proportions of A. actinomycetemcomitans. Both EOP and AP groups showed significantly elevated IgG, IgM and IgA antibody to A. actinomycetemcomitans when compared to a periodontally normal group. The level of IgG antibody was significantly elevated in A. actinomycetemcomitans-positive patients with active disease, while IgA antibody was decreased in a number of the active group patients. Plaque samples derived from active sites showed a clear and significant increase in A. actinomycetemcomitans that occurred from 2-6 months prior to the identification of disease activity. Approximately 70% of the active disease patients showed an increase in IgG antibody level by 2-4 months prior to disease activity. Studies of the antigen reactivity patterns of serum IgG indicated that antibody to antigens of 65, 58, 48, 29 and 24 kDa were more frequent in patients who showed active disease, while those patients with the greatest frequency of active disease appeared to show a general decrease in the recognition of the A. actinomycetemcomitans OMA.

CONCLUSIONS

It appears that A. actinomycetemcomitans infection relates to a particular type of disease with accompanying antibody responses that reflect periods of active disease. The dynamics of A. actinomycetemcomitans infection and the level and specificity of systemic antibody responses to this pathogen support an important contribution of the immune response to managing this infection.

Extracellular antigens of Actinobacillus actinomycetemcomitans Y4 in severe alveolar bone loss patients studied by two-dimensional electrophoresis and western blots

The human immune response to extracellular substances (ES) from Actinobacillus actinomycetemcomitans Y4 were analyzed. Twenty-nine periodontal patients with generalized severe alveolar bone loss and 13 healthy volunteers were examined for serum IgG antibody titers against ES. Among the patients, 17 had higher antibody titers than healthy individuals (high-titer patients) but the remainder (low-titer patients) did not. Two-dimensional electrophoresis (2DE) and Western blots demonstrated that two proteins (40 and 37 kDa) and three smeared substances reacted with IgGs from high-titer patients, but not with IgGs from healthy volunteers. The low-molecular-mass smear at the acid side reacted with over 90% of all patients. This smear reacted with anti-A. actinomycetemcomitans lipopolysaccharide (LPS) monoclonal antibody which recognized LPS from each A. actinomycetemcomitans serotype. The high molecular mass smear at the acid side might be serotype-specific O-antigens of LPS. Another high molecular mass smear which located from the alkaline to the neutral side reacted with anti-serotype-b-specific capsular polysaccharide monoclonal antibody. Moreover, the 40- and 37-kDa proteins reacted with this anti-capsular polysaccharide antibody. This results suggested that 40- and 37-kDa proteins which reacted with 100% or 88% of high-titer patients might be glycoproteins linked with capsular polysaccharide.

Immunoglobulin G subclass response of juvenile periodontitis subjects to principal outer membrane proteins of Actinobacillus actinomycetemcomitans

The cell envelope of Actinobacillus actinomycetemcomitans includes a number of outer membrane proteins (OMPs) which appear to be important targets for immunoglobulin G (IgG) antibodies in sera from localized juvenile periodontitis (LJP) patients. In this study, we examined the subclass distribution of IgG antibodies reactive to the 16.6- and 29-kDa OMPs of A. actinomycetemcomitans in sera from LJP patients and periodontally healthy individuals. Antibody responses were determined in a quantitative enzyme-linked immunosorbent assay that employed human IgG subclass-restricted monoclonal antibodies. High-titer LJP sera (93% black; geometric mean titer, 32,673) were found to contain significantly elevated levels of IgG1, IgG2, and IgG3 antibodies to the 29-kDa OMP of A. actinomycetemcomitans, compared with those of low-titer LJP sera (mean titer, 1,421) and sera from periodontally healthy, race-matched control subjects. The concentration of IgG2 antibody to this protein was greater than or equal to the corresponding IgG1 concentration in 7 of 14 high-titer sera, although mean IgG1 and IgG2 concentrations were not significantly different. The concentrations of IgG1 and IgG2 antibodies to the 16.6-kDa protein were also significantly elevated in LJP sera, although of considerably lesser magnitude than that observed for the 29-kDa protein. The IgG2 response to the 29-kDa protein could not be attributed to the presence of IgG2 antibodies to lipopolysaccharide contaminants or to Fc-binding activity, nor does this molecule appear to be a glycoprotein. Hence, LJP subjects produce IgG2 antibodies, as well as IgG1 and IgG3 antibodies, directed to at least one of the major OMPs of A. actinomycetemcomitans.

Antigen specificity of serum antibody in A. actinomycetemcomitans-infected periodontitis patients

We hypothesized that serum antibody with selected antigen specificities would relate to infection and disease in the patients and, thus, describe the characteristics of potential protective antibody. This study used serum samples from 24 periodontitis patients with subgingival infection and elevated serum IgG antibody to A. actinomycetemcomitans to define the antigenic specificities of IgG, IgM, IgA, and IgG1-4 antibody to A. actinomycetemcomitans strain Y4 outer membrane antigens (OMA). Uniform IgG antibody (> 70% of the patients) was noted to antigens with M(r) of 65, 38, 29, and 17 kDa. Both IgA and IgM specificities reflected those shown for IgG in each patient. IgG1 and IgG2 antibody reacted with several OMA bands in each patient, while IgG3 antibodies were directed to numerous OMA bands in many patients and represented the most broad-based response. The IgG4 response patterns were limited to a few OMA bands. We noted a prominent occurrence of IgG reactions with OMA bands that were characteristic for individual patients. The frequency of responses to OMA of higher M(r) (i.e., > 80 kDa) and to the 34-, 31-, and 24-kDa antigens was positively related to the total IgG antibody levels. Antibody reactive with OMA bands at 65-, 38-, 29-, 17-, 15-, and 11-kDa antigens was detected in patients with few to many teeth infected with A. actinomycetemcomitans. Furthermore, patients with a high percentage of teeth with > or = 6 mm pockets had a decreased frequency of responses to the high-M(r) antigens (i.e. > 90 kDa) as well as to the 58-kDa antigen.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of an immunoglobulin Fc receptor of Actinobacillus actinomycetemcomitans

Actinobacillus actinomycetemcomitans expresses proteins that bind to the Fc portion of immunoglobulins. The immunoglobulin Fc receptors on the surface of A. actinomycetemcomitans were detected by the binding of biotinylated human or murine Fc molecules to strain SUNY 465 adsorbed to the bottom of microtiter wells. Biotinylated Fc binding was inhibited by unlabeled Fc molecules and human plasma. Fc receptors were identified by the binding of biotinylated Fc molecules to bacterial membrane proteins separated by polyacrylamide gel electrophoresis and transferred to nitrocellulose. Multiple bands were identified, and the major Fc-binding protein was determined to be a heat-modifiable protein. This protein migrated with approximate molecular weights of 25,000 and 32,000 (unheated and heated, respectively). Amino-terminal sequence analysis of this protein revealed a sequence identical to the heat-modifiable protein described for A. actinomycetemcomitans ATCC 43718. This protein sequence exhibits significant homology with the N termini of outer membrane protein A (OmpA) of Escherichia coli and related OmpA-like proteins from other gram-negative bacteria.

Similarities between Fusobacterium nucleatum and bacteroides fragilis studied by two DNA probes derived from Fusobacterium nucleatum

A polymerase chain reaction (PCR)-amplified oligonucleotide DNA probe corresponding to a Fusobacterium nucleatum Fevl DNA region coding for a 40-kDa major outer-membrane protein (OMP) and a randomly cloned 2.1 kb DNA probe were found to recognize DNA from the Gram-negative bacteria Fusobacterium nucleatum and Bacteroides fragilis on Southern blots and slot blots. The results indicate sequence similarity within the DNA fragments studied. Immunoblots tested with polyclonal antibodies against whole cells of F. nucleatum revealed only weak antigen similarity between these species.

Recent approaches to the chemotaxonomy of the Actinobacillus-Haemophilus-Pasteurella group (family Pasteurellaceae)

Many members of the Actinobacillus-Haemophilus-Pasteurella group (family Pasteurellaceae) have been misclassified. This article reviews the chemotaxonomic characters that recently have been provided to improve the taxonomy of Pasteurellaceae. These include fatty acids of whole cells, of lipopolysaccharides and of single colonies, together with sugar contents of whole cells, of whole defatted cells, of lipopolysaccharides and of single colonies. This article also reviews taxonomy aided by distribution of proteins in whole cells and outer membranes, distribution of enzymes in outer membrane vesicles and in whole cells, bacteriolysis induced by ethylenediaminetetraacetic acid and hen eggwhite lysozyme and the distribution of respiratory quinones. Furthermore, an overview of characters obtained through studies on genetic transformation, restriction enzyme analysis, restriction fragment length polymorphism, DNA-DNA hybridization, DNA-rRNA hybridization, and 16S rRNA sequencing is given.

Review of chemosystematics: multivariate approaches to oral bacteria and yeasts

There are several problems related to the classification and identification of bacterial and yeast species assigned to the genera Actinobacillus, Haemophilus, Pasteurella, Bacteroides, Prevotella, Porphyromonas, Campylobacter, Wolinella, Treponema, Candida, Torulopsis, and Saccharomyces, most of which belong to the resident oral microflora. The present review was written to demonstrate how multivariate analyses of data on cellular fatty acids, sugars, enzyme activities, and lysis kinetics during ethylenediaminetetraacetic acid (EDTA) and EDTA plus lysozyme treatment can be used to distinguish closely related species of these bacterial and yeast genera. With the exception of the Actinobacillus-Haemophilus-Pasteurella group, fatty acids were more discriminating than sugars. Enzymes from whole cells and outer membrane vesicles also contributed to taxonomic distinction. Apparently, chemosystematics, involving multivariate analyses, is a useful adjunct in oral microbial taxonomy.

Clustering of an outer membrane adhesin of Haemophilus parainfluenzae

Haemophilus parainfluenzae synthesizes an outer membrane protein adhesin which mediates binding to oral streptococci, salivary pellicle, and neuraminidase-treated erythrocytes. An indirect gold labeling technique and immunoelectron microscopy verified the location of this outer membrane protein. Further, a clustering of gold particles was observed in irregular patches at the cell surface.

The heat-modifiable outer membrane protein of Actinobacillus actinomycetemcomitans: relationship to OmpA proteins

The outer membrane of Actinobacillus actinomycetemcomitans contains a 29-kDa protein which exhibits heat modifiability on sodium dodecyl sulfate-polyacrylamide gels and represents a major target for immunoglobulin G antibody in sera of periodontitis patients colonized by this organism. In the present study, the N-terminal amino acid sequence of the 29-kDa outer membrane protein was determined and compared with reported sequences for other known proteins. The heat-modifiable outer membrane protein of A. actinomycetemcomitans was found to exhibit significant N-terminal homology with the OmpA proteins of other gram-negative bacteria. Moreover, this protein reacted with antiserum raised against the purified OmpA protein of Escherichia coli K-12. Whether the heat-modifiable OMP of A. actinomycetemcomitans also shares functional properties of OmpA proteins, particularly with respect to bacteriophage receptor activity, is presently under investigation.

Evidence that the serotype b antigenic determinant of Actinobacillus actinomycetemcomitans Y4 resides in the polysaccharide moiety of lipopolysaccharide

A high-molecular-weight polysaccharide-containing antigen was isolated from a phenol-water extract of Actinobacillus actinomycetemcomitans ATCC 43718 (formerly Y4) by gel permeation chromatography in lipopolysaccharide (LPS)-disaggregating buffer. The polysaccharide antigen formed a precipitin band with rabbit serotype b-specific antiserum but not with rabbit antisera to serotype a or c. Electroblotted serotype b antigen was probed with serum from a patient with localized juvenile periodontitis (LJP), resulting in a diffuse "smear" in the upper region of the lane. By utilizing an enzyme-linked immunosorbent assay, it was demonstrated that the geometric mean immunoglobulin G antibody titer to the serotype b polysaccharide was significantly higher in sera from LJP patients than in sera from periodontally healthy individuals. Moreover, LJP antibody titers to the serotype b polysaccharide exhibited age-dependent variation. Double immunodiffusion analysis revealed that the serotype b antigen formed a line of identity with low-molecular-weight LPS following reaction with serotype b-specific antiserum. Incubation of LJP serum in the presence of a lipid-free polysaccharide moiety obtained by mild acid hydrolysis of LPS from A. actinomycetemcomitans Y4 markedly reduced immunoglobulin G titer to the serotype b antigen. In contrast, solubilized lipid A was only weakly inhibitory. The results of this study indicate that the serotype b-specific determinant of A. actinomycetemcomitans resides in the polysaccharide moiety of LPS and represents a major target for immunoglobulin G antibody in serum of LJP subjects colonized by this organism.

IgG antibody response of localized juvenile periodontitis patients to the 29 kilodalton outer membrane protein of Actinobacillus actinomycetemcomitans

Levels of serum IgG antibody to the 29 kilodalton outer membrane protein of A. actinomycetemcomitans Y4 in sera of periodontally healthy subjects and localized juvenile periodontitis patients were determined using an enzyme-linked immunosorbent assay (ELISA). The 29 kDa protein was isolated by solubilization of an octylglucoside-NaCl insoluble fraction by incubation at ambient temperature in 20 mM sodium phosphate, pH 7.5, containing 1% sodium dodecyl sulfate. The isolated protein migrated on SDS-polyacrylamide gels with an apparent molecular mass of 29 kDa following incubation in sample buffer at ambient temperature. However, the protein migrated with an apparent molecular mass of 34 kDa following incubation in sample buffer at 100 degrees C for 10 minutes. Geometric mean IgG antibody titers to the 29 kDa protein were significantly higher in sera from LJP subjects than in sera obtained from periodontally healthy subjects. Twenty-two of 35 LJP sera (63%) had antibody titers greater than 2 standard deviations from the mean titer of the periodontally healthy group. Among LJP subjects, elevated antibody titers to the 29 kDa protein were found primarily in subjects greater than or equal to 18 years of age, with the highest titers seen in patients 18 to 21 years of age. The results of this study indicate that the humoral response of LJP subjects to A. actinomycetemcomitans includes the production of IgG antibodies which recognize the major outer membrane proteins of this organism.