Porphyromonas gingivalis survives within KB cells and modulates inflammatory response.
OBJECTIVE
The purpose of the study was to investigate the intracellular survival of Porphyromonas gingivalis as a possible mechanism for maintaining periodontitis.


METHODS
P. gingivalis strains, the strain ATCC 33277 and seven clinical isolates, were co-cultured with KB cells. The number of intracellular bacteria was determined up to 3 days after infection. In addition, the numbers of KB cells per well, the concentrations of the cytokines interleukin-1beta (IL-1beta), IL-6, IL-8 and tumour necrosis factor-alpha (TNF-alpha) and the arginine-specific amidolytic activity were measured. The 16S rRNA of P. gingivalis and the mRNA expression of IL-1beta, IL-6, IL-8, TNF-alpha and rgpA were also determined.


RESULTS
All the P. gingivalis strains studied were able to survive within KB cells. In contrast to the reduced values of colony-forming units at day 3, equal and higher levels of 16S rRNA were seen in comparison to day 0. Arginine-specific amidolytic activity declined in all samples during infection. Expression of mRNA for rgpA was not found after infection of KB cells by P. gingivalis strains. IL-8 was detectable in all samples 2 days after infection with P. gingivalis strains. Principal components analysis underlined a correlation between the arginine-specific amidolytic activity 1 h after infection and both the released IL-8 and the mRNA expression of IL-8. Associations were found between the cultivable numbers of intracellular P. gingivalis and the mRNAs of IL-1, IL-6 and TNF-alpha at the day of infection.


CONCLUSIONS
The results indicate survival of P. gingivalis within epithelial cells, possibly in a non-cultivable stage. Invasion into cells modulates the virulence properties of P. gingivalis as well as the inflammatory response of the cells.
Eick
S
S
Department of Medical Microbiology, University Hospital of Jena, Jena, Germany. sigrun.eick@med.uni-jena.de
Reissmann
A
A
Rödel
J
J
Schmidt
K-H
KH
Pfister
W
W
D018829:Adhesins, Bacterial / Q000032:analysis; D002452:Cell Count; D018920:Coculture Techniques; D015169:Colony Count, Microbial; D003546:Cysteine Endopeptidases / Q000032:analysis; D000080867:Gingipain Cysteine Endopeptidases; D006801:Humans; D007375:Interleukin-1 / Q000032:analysis / Q000235:genetics; D015850:Interleukin-6 / Q000032:analysis / Q000235:genetics; D016209:Interleukin-8 / Q000032:analysis / Q000235:genetics; D042541:Intracellular Space / Q000382:microbiology; D007624:KB Cells / Q000276:immunology / Q000382:microbiology*; D016966:Porphyromonas gingivalis / Q000201:enzymology / Q000276:immunology / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D012336:RNA, Ribosomal, 16S / Q000032:analysis; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis / Q000235:genetics; D014774:Virulence
D018829:Adhesins, Bacterial; D000080867:Gingipain Cysteine Endopeptidases; D007375:Interleukin-1; D015850:Interleukin-6; D016209:Interleukin-8; D012333:RNA, Messenger; D012336:RNA, Ribosomal, 16S; D014409:Tumor Necrosis Factor-alpha; D003546:Cysteine Endopeptidases