Immunomodulatory effect of photodynamic therapy in Galleria mellonella infected with Porphyromonas gingivalis

Abstract

Porphyromonas gingivalis is an important pathogen in the development of periodontal disease. Our study investigated if the treatment with antimicrobial photodynamic therapy (aPDT) that employs a nontoxic dye, followed by irradiation with harmless visible light can attenuate the experimental infection of P. gingivalis in Galleria mellonella. Firstly, different concentrations of P. gingivalis ranging from 10 to 10 cells/larva were injected into the animal to obtain a lethal concentration. Next, the following groups of G. mellonella infected with P. gingivalis were evaluated: inoculation of the photosensitizer and application of laser (P + L+), inoculation of physiologic solution and application of laser (P-L+), inoculation the photosensitizer without laser (P + L-) and inoculation of physiologic solution without Laser (P-L-). The effects of aPDT on infection by P. gingivalis were evaluated by survival curve analysis and hemocytes count. A lethal concentration of 10 cells/larva was adopted for evaluating the effects of aPDT on experimental infection with P. gingivalis. We found that after 120 s of PDT application, the death of G. mellonella was significantly lower compared to the control groups (p = 0.0010). Moreover, the hemocyte density in the P+L+ group was increased by 9.6 × 10 cells/mL (2.62-fold increase) compared to the infected larvae with no treatment (L-P- group) (p = 0.0175). Finally, we verified that the aPDT led to a significant reduction of the number of P. gingivalis cells in G. mellonella hemolymph. In conclusion, PDT application was effective against P. gingivalis infection by increasing the survival of G. mellonella and was able to increase the circulating hemocytes indicating that PDT activates the G. mellonella immune system.

Antimicrobial photodynamic therapy with phenothiazinium photosensitizers in non-vertebrate model Galleria mellonella infected with Fusarium keratoplasticum and Fusarium moniliforme

“…Overall, the total hemocyte count after APDT with MB, NMBN and S137 increased in larvae hemolymph whereas the fungal burden was decreased. Similar results were found in APDT with MB against Porphyromonas gingivalis (Santos et al, 2017) and C. albicans (Chibebe Junior et al, 2013). The increase in the cellular immune response here is correlated to the increase of larval survival and decrease of fungal burden.…”

“…So far, this is the first study of APDT with MB, NMBN and S137 in G. mellonella larvae infected with microconidia of the filamentous fungi Fusarium spp. APDT with MB was studied in G. mellonella infected with the yeast fungus Candida albicans (Chibebe Junior et al, 2013) and the Gram-negative bacterium Porphyromonas gingivalis (Santos et al, 2017), and were able to prolong the survival of the infected larvae. MB and NMBN were effective in APDT of immunosuppressed mouse model of oral candidiasis infection (Freire et al, 2016).…”

Effects of periodontitis on the development of asthma: The role of photodynamic therapy

“…Although the increase in defense cells is a disadvantage of this form of treatment, the cytokine release pattern was favorable, as the anti-inflammatory cytokine IL-10 was released in a greater quantity only for this group. These results suggest that PDT could stimulate the cellular immune response as demonstrated by some authors [ 68 ]. Further studies could investigate if both M2 (macrophages) and Treg (regulatory T cells) are implicated in these processes [ 69 ] producing anti-inflammatory cytokines [ 70 , 71 ].…”

Virulence of the Pathogen Porphyromonas gingivalis Is Controlled by the CRISPR-Cas Protein Cas3

“…To assess the “infection transcriptome” of wild-type P. gingivalis and the Δ cas 3 mutant in the G. mellonella infection model, we performed a time-series dual-transcriptome analysis, selecting infected G. mellonella larvae at 0, 1, 2, and 6 h. We decided to use G. mellonella as a model because a strong correlation has been observed in microbial pathogenicity in G. mellonella and mammalian systems ( 34 , 35 ) and because such an approach has been widely used as an initial screening model to assess virulence in a large number of different pathogens, including oral pathogens ( 36 – 38 ). The number of sequences in the G. mellonella infection experiments ranged between 74,281,712 and 86,843,647.…”