Circulating antibodies against leukotoxin A as marker of periodontitis, grades B and C and oral infection with Aggregatibacter actinomycetemcomitans.

BACKGROUND AND AIM The facultative bacterium Aggregatibacter actinomycetemcomitans (A.a.) is strongly associated with periodontitis (PD) and is occasionally found in periodontally healthy subjects. We aimed to determine the prevalence of salivary A.a. among patients with either PD, grade B (PD-B) or grade C (PD-C), periodontally healthy controls (HCs), and to determine if systemic antibodies against A.a. or its virulence factor leukotoxin A (LtxA) may serve as biomarkers that reveal the oral presence of the bacterium and discriminate subjects with PD-C, PD-B or no PD from each other. MATERIALS AND METHODS Serum and unstimulated saliva samples were collected from patients with PD-C (n = 27), patients with PD-B (n = 34) and HCs (n = 28). Serum level of IgG antibodies to fragmented whole A.a. and to LtxA were quantified using a bead-based assay. A.a. was identified in saliva using qPCR. All analyses were adjusted for age, sex and current smoking status. RESULTS A.a. was present in saliva from 11% of HCs, in 32% of patients with PD-B (p = 0.04 vs. HCs), and in 37% of patients with PD-C (p = 0.02 vs. HCs). Serum antibodies to fragments of A.a. associated significantly with PD-C (p = 0.03), while serum anti-LtxA antibodies associated with both PD-B and PD-C (p = 0.002 and p = 9×10-4 , respectively). Moreover, a significant association between serum anti-LtxA antibodies and A.a. count in saliva was observed (p = 0.001). On the basis of serum anti-LtxA antibody levels, PD patients could be discriminated from HCs (AUC = 0.74 in ROC curve-analysis, p = 0.0003), and carriers of A.a. could be discriminated from non-carriers (AUC = 0.78, p<0.0001). CONCLUSION A.a. is highly prevalent in saliva of patients with PD-B or PD-C. Systemic IgG antibodies against LtxA distinguish patients with PD, regardless of grade, from HCs, while their quantity reflects the concurrent bacterial burden in the oral cavity. This article is protected by copyright. All rights reserved.