Salivary LPS Activity as a Biomarker for Chronic Periodontitis

Objective: The causative basis for chronic periodontitis relates to a subverted host innate immune response to a unique bacterial consortium and lipopolysaccharides (LPS) produced by certain pathogenic members of the subgingival plaque community. The specific capacity of a Gram-negative bacterium to alert or evade the host innate immune system through TLR signalling cascade depends on the chemical composition of its Lipid-A (a bioactive centre of LPS) and is currently recognised as a critical aspect defining the relationship between the host and the bacterium. In this study we examined the clinical relevance of structural heterogeneity of salivary lipid-A isoforms as potential, bacterially-derived biomarkers for periodontal disease activity. 

Method: Unstimulated saliva was collected from 10 patients with chronic periodontitis and 10 healthy individuals. LPS was extracted by Tri-reagent protocol and lipid-A was isolated by mild hydrolysis. Chemical composition of lipid-A was analysed by ESI Mass-spectrometry. The inflammatory potential of isolated LPS was examined by the LAL assay.

Result: Mass-spectrometry lipid-A analysis revealed the predominance of under-acylated and under-phosphorylated lipid-A isoforms isolated from the patients with chronic periodontitis. In addition, inflammatory potential of LPS extracted from patients with chronic periodontitis was significantly lower compared to healthy individuals and measured by the LAL assay. Key-stone periodontal pathogens are able to evade the host immune system and periodontal tissues by producing low-potency LPS and can thrive in the subgingival areas as a disguised subpopulation

Conclusion: The elucidation of this pathogenic mechanism is central to the understanding of host-microbial interaction at periodontally healthy and diseased sites.  Identification of salivary lipid-A profile as a bacterially derived biomarker for chronic periodontitis will lead to the development of a rapid and reliable salivary test for destructive periodontal activity, based on the LAL assay.