Variable serum immunoglobulin G immune response to genetically distinct Eikenella corrodens strains coexisting in the human oral cavity

Serum antibody response to periodontal pathogens and herpes simplex virus in relation to classic risk factors of cardiovascular disease

BACKGROUND

Increasing evidence links chronic infections, especially burden of several infections, with increased risk for cardiovascular diseases (CVD). We studied joint immune response against two major periodontal pathogens and herpes simplex virus (HSV) in relation to established risk factors of CVD.

METHODS

Serum antibody levels to HSV, Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis were determined by ELISA. The study included 1107 subjects, 734 from Finland and 373 from Russia.

RESULTS

Combined antibody response to periodontal pathogens was associated inversely (OR, 95% CI) with high-density lipoprotein (HDL) cholesterol concentration (beta = 0.35; 0.20, 0.60; P < 0.001) and directly with HSV antibody quartiles: compared with the first quartile, ORs (95% CI) for quartiles 2-4 were 1.43 (0.88-2.32), 1.74 (1.07-2.82), and 1.89 (1.18-3.02), respectively (P for trend <0.001), after adjusting for age, gender, area, education, smoking, BMI, alcohol, triglycerides, and number of teeth. In linear regression analysis, the 3-pathogen antibody score (comprising antibody levels against periodontal pathogens and HSV) was inversely associated with HDL cholesterol concentration (beta = -0.067/1 mmol/l; -0.235, -0.018; P < 0.05).

CONCLUSIONS

HSV infection may promote infection by periodontal pathogens. Furthermore, the infectious burden comprising HSV and periodontitis may increase the risk for CVD by clearly decreasing HDL cholesterol concentrations.

Antigenically diverse reference strains and autologous strains of Actinobacillus actinomycetemcomitans are equally efficient antigens in enzyme-linked immunosorbent assay analysis

Actinobacillus actinomycetemcomitans is a major pathogen in periodontitis. Data on the clinical relevance of serum immunoglobulin G (IgG) antibody levels against this species are controversial. The aim of the present study was to elucidate how different strains used as antigens in enzyme-linked immunosorbent assay (ELISA) influence the detection of individuals with elevated serum IgG levels against A. actinomycetemcomitans. We hypothesized that the highest antibody levels are targeted to the autologous strains. A total of 19 strains-six antigenically diverse reference strains (serotypes a through e and a nonserotypeable strain) and 13 serotyped autologous strains-were used as whole-cell antigens in ELISA. Serum samples were from 26 untreated adult patients with periodontitis, whose subgingival bacterial samples were either culture positive (n = 13) or culture negative (n = 13) for A. actinomycetemcomitans, and from 10 culture-negative nonperiodontitis subjects. The highest individual (P < 0.05) IgG levels against the reference strains were most commonly against serotypes a and b in patients and against serotype c in nonperiodontitis subjects. The culture-positive patients had the highest (P < 0.05) IgG antibody levels against their autologous strains and against the reference strains of the same serotype. On the contrary, for these patients the levels of antibody against the reference strains of other serotypes were comparable to those of the nonperiodontitis subjects. The results indicated that the serum IgG antibody levels against A. actinomycetemcomitans strongly depend on the strains used as antigens in the ELISA. Elevated serum IgG levels against A. actinomycetemcomitans can be detected equally well using either the autologous strains or a variety of antigenically diverse reference strains as antigens.

Molecular strategies for fimbrial expression and assembly

Fimbriae or pili are long, filamentous, multimeric macromolecules found on the bacterial cell surface. Bacteria express a diverse array of fimbriae or pili that are involved in bacterial adherence and invasion. Fimbriae can be categorized based on their modes of expression and assembly. Type I fimbriae and P pili are distributed peritrichously and translocated to the cell surface by a chaperone/usher pathway. Type 4 pili are located at the pole of the cell and assembled via the type II secretion system. Curli fimbriae are coiled surface structures assembled by an extracellular nucleation/precipitation pathway. Fimbriae of oral gram-negative and gram-positive bacteria have not been well-studied as compared with the fimbriae of enteric pathogens. Oral pathogens, such as Eikenella corrodens, Actinobacillus actinomycetemcomitans, and Porphyromonas gingivalis, possess fimbriae that have been implicated in bacterial adhesion and invasion. These fimbriae are potential virulence factors in oral infectious processes. A. actinomycetemcomitans and E. corrodens have Type 4-like fimbriae, whereas P. gingivalis displays a unique type of fimbriae. To date, fimbriae of the oral primary colonizers, Actinomyces naeslundii and Streptococcus parasanguis, represent the only fimbriae characterized for any gram-positive bacteria. The putative major fimbrial subunits, FimA and FimP of A. naeslundii and Fap1 of S. parasanguis, contain a signal sequence and cell-wall-sorting signal. The presence of extensive dipeptide repeats in Fap1 makes it unique among fimbrial molecules. Based on experimental data, a nucleation/precipitation pathway is proposed for fimbrial biogenesis of both S. parasanguis and A. naeslundii, although we cannot rule out an alternative covalent linkage model. The model systems described in this review served as a framework for hypotheses for how the known molecular factors of fimbriae on oral bacteria may be expressed and assembled.