Porphyromonas gingivalis-Host Interactions in aDrosophila melanogasterModel

Abstract

Porphyromonas gingivalis is a Gram-negative obligate anaerobe that has been implicated in the etiology of adult periodontitis. We recently introduced a Drosophila melanogaster killing model for examination of P. gingivalis-host interactions. In the current study, the Drosophila killing model was used to characterize the host response to P. gingivalis infection by identifying host components that play a role during infection. Drosophila immune response gene mutants were screened for altered susceptibility to killing by P. gingivalis. The Imd signaling pathway was shown to be important for the survival of Drosophila infected by nonencapsulated P. gingivalis strains but was dispensable for the survival of Drosophila infected by encapsulated P. gingivalis strains. The P. gingivalis capsule was shown to mediate resistance to killing by Drosophila antimicrobial peptides (Imd pathway-regulated cecropinA and drosocin) and human beta-defensin 3. Drosophila thiol-ester protein II (Tep II) and Tep IV and the tumor necrosis factor (TNF) homolog Eiger were also involved in the immune response against P. gingivalis infection, while the scavenger receptors Eater and Croquemort played no roles in the response to P. gingivalis infection. This study demonstrates that the Drosophila killing model is a useful high-throughput model for characterizing the host response to P. gingivalis infection and uncovering novel interactions between the bacterium and the host.Porphyromonas gingivalis is a Gram-negative, obligate anaerobe that has been strongly implicated as a pathogen in adult (chronic) periodontitis (23, 29), a polymicrobial inflammatory disease that affects the gingiva and other toothsupporting structures. In order to characterize P. gingivalishost interactions a number of animal infection models have been developed, the most common of which are rodent models (6,20,25,28,40,44). Rodent models have been used to identify P. gingivalis components that are involved in pathogenesis (26,32,43,46,48,52,56,57,67,73) and to characterize the host response to P. gingivalis infection (3,6,7,13,22,31,34,35,41,74).The use of the fruit fly Drosophila melanogaster has been well established for examining host-pathogen interactions (5,16,19,21,53,55,65,66). Numerous studies have demonstrated the high degree of conservation between the Drosophila immune system and the mammalian innate immune system (reviewed in reference 49). Like the mammalian innate immune system, the Drosophila immune system detects the presence of invading microbes by using pattern recognition receptors (PRRs), which recognize pathogen-associated molecular patterns (PAMPs) and trigger an immune response that is specific for the class of invading microbe. Other mammalian immune response features that are conserved in Drosophila include signaling pathways (e.g., Toll/interleukin-1 receptor [IL1R], tumor necrosis factor receptor [TNFR]), antimicrobial peptides (AMPs), macrophage-like blood cells, complement C3/ ␣ 2 -macroglobulin (C3/␣ 2 M) superfamily proteins, cytokines, react...

The Capsule of Porphyromonas gingivalis Leads to a Reduction in the Host Inflammatory Response, Evasion of Phagocytosis, and Increase in Virulence

“…Our study, done using a defined isogenic mutant, shows that the nonencapsulated PgC strain is less virulent than the encapsulated W50 strain, thus demonstrating that indeed the capsule plays a role in the virulence of P. gingivalis in the mouse abscess model. These results are consistent not only with previous reports using the rodent abscess model but also with a recent publication demonstrating reduced virulence of the nonencapsulated PgC strain compared to that of encapsulated W50 bacteria in the fruit fly Drosophila melanogaster model of infection (26). A model of infection in which the outcome is bacterium initiated but host driven was used in the study, as is observed in the case of periodontal disease.…”

“…The P. gingivalis capsule may also contribute to increased survival by reducing the bactericidal effect of defensins, small antimicrobial peptides produced by a variety of host cells. Indeed, a recent study demonstrated capsule-dependent increased resistance of P. gingivalis to defensins (26).…”

Porphyromonas gingivalis Virulence in a Drosophila melanogaster Model

“…7). Finally, several immune response-defective Drosophila mutants show increased susceptibility to killing by P. gingivalis (36).…”

“…Thirty-nine Drosophila flies per group were infected (as described above) with the following P. gingivalis strains: W83, ATCC 49417, 381, ATCC 33277, A7A1, and 23A4. Three animals per group were ground in 80 l of PBS with a Teflon pestle at the following time points (in hours) postinfection: 0, 4,8,12,24,36,48,60,72,84,96,108, and 120. Viable P. gingivalis cell counts were determined on BBA plates containing gentamicin (8 g/ml), amphotericin B (3 g/ml), and vancomycin (1 g/ml).…”

Tobacco-gene activity profile in Porphyromonas gingivalis, Filifactor alocis and Treponema denticola.

“…Defensins, a small antimicrobial peptides produced by host cells have a bactericidal effect. P. gingivalis capsule reduces the bactericidal effect of these peptides contributing to increased survival of the organism (122). The non-encapsulated PgC strain is less virulent than the encapsulated W50 strain, demonstrating that capsule plays a role in the virulence of P. gingivalis in the mouse abscess model (111).…”