Granulomatous lymphadenitis and pneumonia associated with Actinobacillus porcitonsillarum in a slaughter pig.

Multiple coalescing granulomatous foci were detected in the pulmonary hilar and mediastinal lymph nodes and lung of a slaughtered pig aged 6 months. Haemolytic, Gram-negative bacilli were isolated from the lymph nodes. The isolate (strain TO17214) strongly cross-reacted with sera against Actinobacillus pleuropneumoniae serotype 12 in slide agglutination tests. Comparative 16S rDNA gene sequencing analysis identified strain TO17214 as Actinobacillus porcitonsillarum. Histologically, extensive inflammation took the form of large granulomas consisting of epithelioid cells and multinucleated giant cells in the lymph nodes and lung, and Gram-negative bacilli were discernible in the centres of the lesions. Immunohistochemically, the organisms cross-reacted with polyclonal antibodies against A. pleuropneumoniae serotypes 12 and 2. The results indicated that A. porcitonsillarum, previously considered non-pathogenic, can induce multifocal granulomatous lymphadenitis accompanied by pneumonia in the growing-finishing pig.

A gene cluster for the synthesis of serotype d-specific polysaccharide antigen in Actinobacillus actinomycetemcomitans.

The serotype d antigen of Actinobacillus actinomycetemcomitans consists of D-glucose, D-mannose, and L-rhamnose in a molar ratio of 1:2:1. A gene cluster involved in the synthesis of serotype-specific polysaccharide antigen was cloned from the chromosomal DNA of A. actinomycetemcomitans IDH 781 (serotype d). This cluster consisted of 12 open reading frames. Insertional inactivation of six genes in this cluster resulted in loss of ability of A. actinomycetemcomitans IDH 781 cells to produce the polysaccharide. Comparing the structure of the gene cluster with similar clusters from other serotypes of A. actinomycetemcomitans, showed that eight genes are unique to serotype d; the other four genes are involved in the biosynthesis of dTDP-L-rhamnose. These results suggest that the synthesis and structure of serotype d-specific polysaccharide of A. actinomycetemcomitans is quite different from those of other serotype strains.

Neutrophil response, serum opsonic activity, and precipitating antibodies in human infection with Actinobacillus hominis.

Actinobacillus species are usually not considered as being human pathogens apart from A. actinomycetemcomitans. However, single cases of human meningitis, septicemia, and empyema caused by Actinobacillus lignieresii have been reported in the literature. This is the first reported case of Actinobacillus hominis giving rise to pleural-empyema in a patient with carcinoma of the lung. The function of peripheral blood neutrophils, serum opsonic activity and specific precipitating antibodies were investigated. Neutrophils from the patient exhibited an enhanced oxidative burst response measured by chemiluminescence assay. Furthermore, the opsonic activity of the serum from the patient was higher than that of a healthy control person. Several precipitating antibodies to various antigens of Actinobacillus hominis were demonstrated in the serum of the patient by crossed immunoelectrophoresis.

Host response in experimental periodontal disease.

Experiments were performed to determine the role of the immune response in rat periodontal disease. Germ-free rats were fed defined antigen-free liquid diets or a diet containing ovalbumin(OVA) as a prototype antigen. The OVA-fed rats demonstrated increased gingival lymphocytes (mainly T at early times), OVA-sensitized spleen cells, and increased periodontal bone loss. In further studies, rats pre-sensitized with OVA, and receiving OVA in the diet, showed elevated IgG antibody, sensitized spleen cells, and elevated periodontal bone loss scores. The concept that bone loss was due to mixed hypersensitivity reaction is consistent with the periodontal pathology. The effects of pre-immunization with A. actinomycetemcomitans (Aa) on periodontal bone loss in Actinobacillus (Aa) - infected rats was examined. Delayed hypersensitivity (DTH) was present in immunized rats throughout the experimental period. Sham-immunized rats showed DTH after 30 days of infection. In addition, immunized rats showed elevated bone loss scores. These experiments support the contention that a combination of hypersensitivity reactions (i.e., mixed hypersensitivity to Aa) could give rise to the periodontal pathology observed. Congenitally athymic rats (nude) were shown to have more periodontal bone loss than did normal littermates. However, bone loss in thymus-cell reconstituted nude rats was not different from that in control rats. Normal rats receiving Aa-sensitized T lymphocytes prior to infection with Aa demonstrated increased DTH and periodontal bone loss. These studies support the concept that T-cell functions and thymic regulation of immune responses can exert protective and/or destructive effects in periodontal disease. In order to modify disease, it will be necessary to enhance the protective aspects of the immune response and to minimize the detrimental aspects.

Biochemical and serological properties of Actinobacillus pleuropneumoniae biotype 2 strains isolated from swine.

The biochemical and serological properties of 21 strains of Actinobacillus pleuropneumoniae biotype 2 isolated from haemorrhagic necrotic pleuropneumonia of swine were examined. For serologic typing, the indirect haemagglutination (IHA) and the double gel-diffusion tests were used. On the basis of their soluble surface antigens, our A. pleuropneumoniae biotype 2 isolates could be assigned to two proposed serotypes. Serotype 1 comprised 11 strains and serotype 2 comprised 10 strains. All strains contained two surface antigen components. In the strains belonging to serotype 1, one of the antigens was identical with the serotype-specific antigen of Pasteurella haemolytica T4. Both antigens of serotype 2 strains proved to be type-specific. Four strains received from Switzerland, including the holotype strain of A. pleuropneumoniae biotype 2, and three strains isolated from swine in the G.D.R. belonged to serotype 2. Both the double gel diffusion and the IHA tests detected a 2-way cross-reaction between biotype 1, serotype 2 and biotype 2, serotype 2 strains of A. pleuropneumoniae, which could be eliminated using cross-absorbed sera.

Immunological properties of Actinobacillus pleuropneumoniae hemolysin I.

The 105 kDa hemolysin I protein from Actinobacillus pleuropneumoniae serotype I type strain 4074 (HlyI) was shown by immunoblot analysis to be the predominant immunogenic protein if convalescent field sera or sera from pigs experimentally infected with A. pleuropneumoniae serotype 1 were used. SDS gel- and immunoblot-analysis using total culture, washed cells or culture supernatant showed that HlyI is essentially secreted and is not found attached to the bacteria. Proteins in the 105 kDa range that react strongly with anti-HlyI antibody, are produced by all serotypes and are presumed to be their hemolysins. Sera from pigs experimentally infected with each of the 12 serotypes strongly reacted with HlyI. In addition, some sera from pigs that were confirmed to be negative for A. pleuropneumoniae, also reacted with HlyI as well as with related proteins from Actinobacillus rossii and Actinobacillus suis. These two species produce proteins in the 105 kDa range which cross-react strongly with HlyI. They could be the source of the immunological reactions of the A. pleuropneumoniae-negative sera with HlyI. However, no cross-reactions could be found between HlyI and the Pasteurella haemolytica leukotoxin, the Escherichia coli alpha-hemolysin or related proteins from various hemolytic E. coli strains isolated from pigs. The immunological cross-reactions of HlyI with related proteins from A. rossii, A. suis and possibly from other bacterial species may create uncertainty in interpretation if HlyI is used as the antigen in serodiagnosis of A. pleuropneumoniae.

Identification of Actinobacillus pleuropneumoniae strains of serotypes 7 and 4 using monoclonal antibodies: demonstration of common LPS O-chain epitopes with Actinobacillus lignieresii.

Monoclonal antibodies (Mabs) against Actinobacillus pleuropneumoniae serotype 7 were produced and characterized. Three Mabs directed against surface polysaccharides were selected. One of the Mabs was directed against a capsular polysaccharide epitope (CPS) of A. pleuropneumoniae serotype 7 whereas two other Mabs reacted with different epitopes of the LPS O-chain. One of the latter reacted with the reference strain of serotype 7 and the other one with serotypes 7 and 4. These three Mabs were used to test, by Dot-ELISA, 508 field strains of A. pleuropneumoniae. None of the strains belonging to other serotypes different from serotypes 4 and 7 were positive with the Mabs. Used in combination, the CPS and one of the LPS O-chain directed Mabs were shown to be suitable for serotyping since they detected 100% of serotype 7 strains. In this study, we confirm for the first time that A. pleuropneumoniae serotype 4 is present in North America. Finally, both O-chain specific Mabs also reacted with the O-chain of Actinobacillus lignieresii. The cross-reactivity between the two species was confirmed using sera from pigs experimentally infected with A. pleuropneumoniae serotype 7 and A. lignieresii, using immunoblotting and ELISA. This is the first report of a specific cross-reactivity between the LPS of these bacterial species.

Improved protection of swine from pleuropneumonia by vaccination with proteinase K-treated outer membrane of Actinobacillus (Haemophilus) pleuropneumoniae.

The immunogenic and protective potentials of an outer membrane-enriched fraction (OM) from a serotype 5 strain of Actinobacillus (Haemophilus) pleuropneumoniae (APP) and the same OM degraded with proteinase K or periodate were evaluated in swine. Groups of pigs were vaccinated with two doses of OM, proteinase K-treated OM (P-OM), periodate-treated OM (PI-OM), or placebo vaccine and challenged intranasally with the homologous strain of APP. Results from triplicate experiments indicated that proteinase K treatment of OM resulted in an improved efficacy. This improved efficacy of P-OM vaccine over untreated OM vaccine was evidenced not only by less severe lung lesions in P-OM vaccinated pigs but also by significant reduction (P less than 0.05) in the number of P-OM vaccinated pigs which developed lung lesions upon challenge with APP. Assessment of sera from vaccinated animals by immunoblotting, complement fixation test, or ELISA indicated that the immunogenicity of some but not all protein or carbohydrate components were reduced (or eliminated) by proteinase K and periodate treatments respectively.

Studies on the interactions of two different serotypes of Actinobacillus pleuropneumoniae.

In vitro and in vivo interactions of various field strains of Actinobacillus pleuropneumoniae of serotypes 1, 2, 5 and 7 were studied. There was no influence of one serotype over the other when strains belonging to two serotypes were cultivated together in vitro. In vivo interactions showed predominance of serotype 1 over other serotypes when a strain of serotype 1 was inoculated together with a strain of serotype 2 or 5 in mice. Serotype 1 strain remained predominant irrespective of whether it was inoculated before or after the inoculation of serotype 2 strain. The mortality caused by the inoculation of two strains was higher than the mortality caused by a single strain. Early mortality was observed on inoculation of strains of serotype 2, 5 or 7 along with a strain of serotype 1. Both serotypes could be detected in the blood on cultural examination of mice infected with mixed serotypes.

Comparison of protective immunity and inflammatory responses of pigs following immunization with different Actinobacillus pleuropneumoniae preparations with and without adjuvants.

Three experiments were performed to evaluate the inflammatory response, the antibody response and protection from experimental challenge of various Actinobacillus pleuropneumoniae serotype 5 (Ap5) vaccines in swine. In the first experiment, subcutaneous injections of either a water-in-oil (W/O) emulsion or Freund's complete adjuvant (FCA) caused lesions at the site of injection, while intraperitoneal injection of the W/O emulsion caused no lesions. In the second experiment, intraperitoneal (IP) injection of a W/O emulsion containing unwashed Ap5 cells (6-h culture) and/or supernates from a 24-h culture resulted in severe peritoneal lesions, while W/O emulsion containing PBS-washed Ap5 cells resulted in minimal peritoneal lesions. Ap5 alone or W/O alone failed to cause peritoneal lesions. The third experiment compared the antibody response and protection from challenge of pigs immunized with either 6-h PBS-washed Ap5 cells emulsified in oil - IP, 6-hour Ap5 cells adjuvanted with dimethyl diodacyl ammonium bromide - IP, Ap5 antigen alone - IP, a commercial vaccine - subcutaneously or saline - IP. All groups, except the saline-treated group, responded with high antibody titers to Ap5 2 weeks following vaccination; however, titers from the W/O plus antigen group were significantly higher than the three other groups (P less than 0.05). Following intranasal challenge with Ap5, all animals responded with increased antibody titers. All pigs were euthanized 10 days after challenge and evaluated for pneumonia and the lungs cultured for bacteria. The lungs of all pigs, excepting the W/O plus antigen group, contained pneumonic lesions and A. pleuropneumoniae was cultured from these lesions. These results, along with results from other groups, suggest that intraperitoneal immunization using oil-adjuvanted vaccine may be an effective method for protecting pigs from pneumonia due to A. pleuropneumoniae. Its efficacy may be due to stimulation of local respiratory mucosal immunity.

Development of a rapid qualitative assay for determining elevated antibody levels to periodontopathic organisms.

To allow more widespread use of systemic antibody analysis in clinical settings, a rapid test for determining elevated antibody to periodontitis-associated bacteria was developed. The technique utilizes dot-immunoblotting (DIB) on nitrocellulose paper with whole formalinized Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and Prevotella intermedia. An ELISA was used to compare IgG antibody levels to these organisms in venous serum and peripheral capillary blood from 44 subjects. Correlation between serum and capillary levels ranged from r = 0.760 to 0.900 (P less than 0.00001). Capillary blood antibody levels averaged 55% of those detected in serum. The assay was developed using a variety of antigen and reagent concentrations and multiple chromogenic enzyme-substrate systems. Subsequently, 34 periodontally diseased and 10 periodontally healthy subjects were analyzed for serum IgG antibodies using a quantitative ELISA. The qualitative DIB was performed using capillary blood obtained by digi-puncture and results were compared in a blind fashion to the ELISA data. Relative to its ability to detect elevated antibody levels to these 3 organisms, the DIB had an overall sensitivity of 93% and a specificity of 87% (P less than 0.000001). Using peripheral capillary blood and the DIB, detection of elevated systemic antibody levels can be performed in approximately 2 hours. The DIB may be a useful aid in assessing the host response to putative periodontopathic microorganisms.

Relationship between attachment loss and precipitating serum antibody to Actinobacillus actinomycetemcomitans in adolescents and young adults having severe periodontal destruction.

The purpose of this study was to determine if adolescents and young adults with severe periodontal disease had precipitating serum antibody reactive with Actinobacillus actinomycetemcomitans, and, if so, to correlate presence or absence of the precipitin with clinical patterns of periodontal destruction. Double diffusion in gel was used to detect precipitins. Test and known positive standard sera were run in different wells against a common well containing a minute of sonicates from two strains of A. actinomycetemcomitans (Y4 and N27). Periodontal loss of attachment was measured with a probe on four surfaces per tooth; missing and unerupted teeth were noted with the aid of radiographs. Precipitating antibody was seen in 77% of sera from 22 subjects with localized juvenile periodontitis, 40% of 35 young subjects with more generalized severe disease, and 2% of 44 periodontally healthy individuals. About 80% of the positive reactions were with strain Y4. Within the diseased groups, there were significantly fewer involved teeth in subjects with precipitating antibody (Ab+) than among those in whose sera precipitins were not seen (Ab-). Comparisons of the distribution and severity of involved teeth between Ab+ and Ab- subjects were consistent with an hypothesis that high levels of antibody specific for A. actinomycetemcomitans have a protective effect against periodontal destruction.

Reaction of human sera from juvenile periodontitis, rapidly progressive periodontitis, and adult periodontitis patients with selected periodontopathogens.

The levels of serum antibody reactive to selected periodontopathogens were determined in 182 clinically characterized patients: 35 healthy control, 50 juvenile periodontitis, 42 adult periodontitis and 55 rapidly progressive periodontitis. Reactive antibody levels were determined using an enzyme-linked immunosorbent assay with whole cell preparations of Bacteroides gingivalis, Capnocytophaga (Bacteroides) ochraceus, Fusobacterium nucleatum and Actinobacillus actinomycetemcomitans (Y-4) serving as antigens. Increased reactivity to B. gingivalis and F. nucleatum was observed in all three disease groups studied while antibody reactive to A. actinomycetemcomitans was increased in juvenile and rapidly progressive periodontitis. Antibody levels reactive to C. ochraceus in healthy subjects did not differ from those observed in any disease patient groups. Possible implications in the etiology and progression of the diseases coupled with environmental changes which occur in the econiche of the periodontal pocket are described.

Tissue localization of Actinobacillus actinomycetemcomitans in human periodontitis. II. Correlation between immunofluorescence and culture techniques.

Recent immunohistological studies have suggested that Actinobacillus actinomycetemcomitans is present in the gingival tissues in juvenile periodontitis lesions. The present study examined tissue bound A. actinomycetemcomitans by bacterial culture and immunohistological demonstration of antigen in tissue. A total of 14 periodontitis lesions were examined. Eleven biopsies were obtained from gingiva adjacent to A. actinomycetemcomitans infected pockets, while the remaining three control biopsies were obtained from gingiva adjacent to pockets where subgingival A. actinomycetemcomitans infection could not be detected. Each biopsy was hemisected, one half was used for immunofluorescence microscopic examination while the other half was processed for culture of A. actinomycetemcomitans. The latter section was surface-disinfected, repeatedly washed and then minced to release bacteria from within the tissues. Aliquots from the serial washings and the minced tissue suspension were cultured on medium selective for A. actinomycetemcomitans. Surface disinfection and serial washings gradually decreased cultivable A. actinomycetemcomitans in the washings aliquots. Following tissue disruption, an increase in colony-forming units of A. actinomycetemcomitans was seen from eight of the 11 test biopsies. This bacterium could not be detected in washings or minced tissue suspensions from the control biopsies obtained from lesions in which subgingival A. actinomycetemcomitans was previously not detected. A positive correlation was seen between the presence of A. actinomycetemcomitans antigens in the gingival biopsies and; (1) A. actinomycetemcomitans colony-forming units released from the minced tissues (r = 0.90, p = 0.000), as well as; (2) the colony-forming units from the periodontal pocket (r = 0.62, P = 0.017).(ABSTRACT TRUNCATED AT 250 WORDS)

The periodontal microflora of juvenile diabetics. Culture, immunofluorescence, and serum antibody studies.

These studies demonstrate a unique constellation of organisms populating the subgingival area in periodontitis lesions of patients with juvenile or insulin-dependent diabetes mellitus (IDDM). The cultivable microflora was predominated by Capnocytophaga and anaerobic vibrios in the patients studied. In some patients, Actinobacillus actinomycetemcomitans were also found. This distinguishes the subgingival flora of IDDM patients suffering from periodontitis from that of patients with localized juvenile periodontitis (LJP), and that of adult periodontitis patients. In LJP most patients harbor both A actinomycetemcomitans and Capnocytophaga subgingivally; and in periodontitis lesions from nondiabetic adults, black-pigmented Bacteroides such as B gingivalis or B melaninogenicus subspecies intermedius are often found. Antibiotic susceptibility patterns suggest that penicillin or tetracycline or its analogs such as minocycline may be effective against the predominant cultivable microflora in periodontal lesions of IDDM patients; however, individual patients may harbor flora with significant resistance to these antibiotics.

Periodontitis associated with Papillon-Lefèvre syndrome.

The predominant subgingival microflora, host immune response, and genetic history of a 14-year-old girl with Papillon-Lefèvre Syndrome (PLS) are reported. The patient had high counts of Actinobacillus actinomycetemcomitans and surface translocating bacteria. She had significantly raised levels of antibodies to five of the bacterial species studied with the levels to A. actinomycetemcomitans remaining high after antibiotic therapy. The polymorphonuclear leukocytes (PMN) also released significantly increased amounts of O2 compared to controls. The data presented support a role for A. actinomycetemcomitans and PMN dysfunction in the pathogenesis of PLS.

Antibodies to Actinobacillus actinomycetemcomitans in a Korean population.

Previous studies demonstrated that serum antibodies to Actinobacillus actinomycetemcomitans strain Y4 are significantly elevated in sera from localized juvenile periodontitis (LJP) and postlocalized juvenile periodontitis (P-LJP) patients compared to normal controls in United States populations. This study examined the age of subjects in relation to the antibody levels to A. actinomycetemcomitans in a Korean population. Seven groups were investigated including sera from newborns, infants, children, periodontally normal puberty and adult groups and LJP and P-LJP groups. Antibody levels were determined by an enzyme-linked immunosorbent assay (ELISA) to A. actinomycetemcomitans strain SNUDC 10-1 (serotype C) isolated from a Korean LJP patient. In the healthy non-LJP and non-P-LJP subjects, IgG levels decreased from the newborn group to the 5-month-old group and then gradually increased through the adult group. The IgM levels in these groups continuously increased from birth until a plateau was reached in the 2- to 6-year group. Serum IgA levels to strain SNUDC 10-1 were too low to be measured by this assay.

The cellular host response in juvenile periodontitis. A review.

The current knowledge on the cellular, host-response features in juvenile periodontitis (JP) has been reviewed. The chemotaxis of the polymorphonuclear leukocytes (PMNs), known to be defective in JP, is modulated by serum factors and bacteria. The interactions of the putative etiologic pathogen Actinobacillus actinomycetemcomitans (A.a.) and the enzyme lysozyme with PMNs modify the host defense. Data on the phagocytic capacity of the peripheral blood and gingival crevice PMNs in JP are still controversial. The monocytes exhibit similar alterations as PMNs in interaction with A.a., but the reports on defective monocyte chemotaxis are conflicting. Both bacterial challenge and genetic factors may regulate the lymphocyte response in JP.

Serum antibodies to periodontal bacteria.

The purpose of this study was to determine how serum antibodies reactive with periodontitis-associated bacteria with relates to the diagnosis of periodontitis subjects. Study groups included localized juvenile periodontitis (LJP) subjects, severe periodontitis (SP) subjects, chronic adult periodontitis (AP) subjects, and age matched controls. Twenty-two bacterial strains, representing 18 different species most commonly found in early onset periodontitis were evaluated using serum from LJP, SP, and age matched controls. Serum IgG reactive with these organisms was determined using a radioimmunoassay (RIA). Serum antibody reactive with 13 bacterial strains differed significantly (P less than 0.01) between the three clinical groups. Discriminate analysis revealed that antibodies reactive with 5 bacterial strains of the 13 were able to identify the clinical group to which subjects belonged 79% of the time with control subjects being correctly identified 100% of the time, LJP subjects 78% of the time, and SP subjects 60% of the time. These strains included two strains of Actinobacillus actinomycetemcomitans (Y4 and N27), Fusobacterium nucleatum (E1D1), Eubacterium brachy, and Bacteroides gingivalis. The low classification rate of SP subjects suggested heterogeneity. The SP group could be divided into three subgroups using the serological data. One subgroup, with "super" severe attachment loss, generally lacked antibody reactive with these five organisms, another subgroup was serologically similar to LJP subjects, while the third subgroup had antibodies to additional organisms. This suggests that some SP subjects may represent a more advanced form of LJP. Comparison of antibody reactivity of AP subjects with age matched controls to 23 bacterial types revealed that mean serum antibody reactivity to only Bacteroides gingivalis was higher in AP subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum and gingival fluid antibodies as adjuncts in the diagnosis of Actinobacillus actinomycetemcomitans-associated periodontal disease.

Serum antibody titers to Actinobacillus actinomycetemcomitans were measured in 200 subjects by an enzyme-lined immunosorbent assay (ELISA) using whole microorganisms as antigen. Comparisons were made between titers found in periodontally normal subjects and titers in subjects with localized juvenile periodontitis (LJP), postlocalized juvenile periodontitis, generalized juvenile periodontitis or adult periodontitis. It was found that titers to all three serotypes of A. actinomycetemcomitans were elevated in LJP patients' sera, while serum antibody levels in other diseased groups were not significantly elevated to any of the serotypes. Patient sera were also examined for serum antibody to oral Haemophili previously shown to cross-react with A. actinomycetemcomitans. Similar antibody titers were found in both normal subjects and in patients with various forms of periodontal disease to Haemophilus aphrophilus, H. influenzae and H. parainfluenzae. The A. actinomycetemcomitans antibodies which were elevated in LJP patients could not be correlated with antibody titers to cross-reacting Haemophili, suggesting that these antibodies are A. actinomycetemcomitans-specific. Serum antibody responses in six of the LJP patients were assessed to autologous strains of A. actinomycetemcomitans. Each patient was found to be infected with only a single serotype of A. actinomycetemcomitans, and specific antibodies to the infecting serotype were found in the patients' sera. In families, the LJP patients had significantly elevated IgG, IgA and IgM serum antibody titers to A. actinomycetemcomitans, while the IgG and IgA antibody titers in periodontally normal siblings were at levels comparable to those found in normal subjects. However, IgM serum antibodies were elevated in the periodontally normal siblings of LJP patients suggesting that the formation of IgM antibodies to A. actinomycetemcomitans may precede the clinical appearance of localized juvenile periodontitis. Gingival crevicular fluid and serum antibody levels to A. actinomycetemcomitans were compared in LJP patients. Comparable titers of IgG, IgA and IgM antibodies were found in serum and gingival fluid in most subjects; however, gingival fluid samples sometimes showed higher titers than serum, likely resulting from local antibody synthesis. The value of serum antibody determinations to A. actinomycetemcomitans in the diagnosis of Actinobacillus-associated periodontitis was also assessed. The predictive value of a positive test (significantly elevated anti-A. actinomycetemcomitans IgG) was 86%, while the specificity was 89%.(ABSTRACT TRUNCATED AT 400 WORDS)