Epithelial responses and Candida albicans pathogenicity are enhanced in the presence of oral streptococci.

Experimental models that consider host-pathogen interactions are relevant for improving knowledge about oral candidiasis. The aim of this study was to assess the epithelial immune responses, Candida penetration of cell monolayers, and virulence during mixed species culture infections. Single species cultures of Candida albicans and mixed cultures (C. albicans, Streptococcus mutans, and Streptococcus sanguinis) were used to infect monolayers of HaCaT and FaDu ATCC HTB-43 cells for 12 h. After infection, IL-18 and IL-34 gene expression was measured to assess epithelial cell immune responses, and lactate dehydrogenase (LDH) activity was measured as an indicator of cell damage. Microscopy determined C. albicans morphology and penetration of fungal cells through the keratinocyte monolayer. Monolayers devoid of infection served as controls. Data were analyzed by an ANOVA one-way test followed by Tukey's post-hoc test (α = 0.05). The results found that IL-18 and IL-34 gene expression and LDH activity were significantly (p < 0.05) upregulated for both cell lines exposed to mixed species cultures compared with C. albicans alone. Candida albicans yeast and hyphae were evident in C. albicans only infections. In contrast, monolayers infected by C. albicans, S. mutans, and S. sanguinis exhibited higher microbial invasion with several hyphal aggregates detected. The presence of streptococci in C. albicans infection enhances the virulence and pathogenicity of the fungus with associated increased immune responses and tissue damage. Extrapolation of these findings to oral infection would indicate the added potential benefit of managing bacterial components of biofilms during treatment.

Epithelial responses and Candida albicans pathogenicity are enhanced in the presence of oral streptococci

Abstract Experimental models that consider host-pathogen interactions are relevant for improving knowledge about oral candidiasis. The aim of this study was to assess the epithelial immune responses, Candida penetration of cell monolayers, and virulence during mixed species culture infections. Single species cultures of Candida albicans and mixed cultures (C. albicans, Streptococcus mutans, and Streptococcus sanguinis) were used to infect monolayers of HaCaT and FaDu ATCC HTB-43 cells for 12 h. After infection, IL-18 and IL-34 gene expression was measured to assess epithelial cell immune responses, and lactate dehydrogenase (LDH) activity was measured as an indicator of cell damage. Microscopy determined C. albicans morphology and penetration of fungal cells through the keratinocyte monolayer. Monolayers devoid of infection served as controls. Data were analyzed by an ANOVA one-way test followed by Tukey's post-hoc test (α = 0.05). The results found that IL-18 and IL-34 gene expression and LDH activity were significantly (p < 0.05) upregulated for both cell lines exposed to mixed species cultures compared with C. albicans alone. Candida albicans yeast and hyphae were evident in C. albicans only infections. In contrast, monolayers infected by C. albicans, S. mutans, and S. sanguinis exhibited higher microbial invasion with several hyphal aggregates detected. The presence of streptococci in C. albicans infection enhances the virulence and pathogenicity of the fungus with associated increased immune responses and tissue damage. Extrapolation of these findings to oral infection would indicate the added potential benefit of managing bacterial components of biofilms during treatment.

Resumo O objetivo deste estudo foi avaliar a resposta epithelial imune, a colonização da Candida albicans em monocamadas celulares e sua virulência em resposta a infecções de culturas de biofilme multiespécie. Culturas de biofilme monoespécie de C. albicans e culturas mistas (C. albicans, Streptococcus mutans e Streptococcus sanguinis) foram utilizadas para infectar monocamadas de células HaCaT e FaDu por 12 h. Após a infecção, a expressão dos genes IL-18 e IL-34 foi medida para avaliar as respostas imunes das células epiteliais. A atividade da lactato desidrogenase (LDH) foi medida como um indicador de dano celular. A microscopia determinou a morfologia de C. albicans e a penetração das células fúngicas através da monocamada de queratinócitos. Monocamadas em que não houve infecção serviram como controles. Os dados foram analisados por um teste ANOVA one-way seguido pelo teste post-hoc de Tukey (α = 0,05). Os resultados demonstraram que a expressão gênica de IL-18 e IL-34 e a atividade de LDH foram (p < 0,05) reguladas positivamente para ambas as linhagens de células expostas a culturas de espécies mistas em comparação com C. albicans isoladamente. Leveduras de C.albicans e hifas foram evidentes em infecções apenas por C. albicans. Entretanto, monocamadas infectadas por C. albicans, S. mutans e S. sanguinis exibiram maior invasão microbiana com vários agregados de hifas detectados. Dessa maneira, a presença de estreptococos na infecção por C. albicans aumentou a virulência e a patogenicidade do fungo com respostas imunes aumentadas associadas a danos nos tecidos. A extrapolação desses achados para a infecção oral indicaria o potencial benéfico do controle dos componentes bacterianos em biofilmes durante a terapia da candidíase

Virulence and pathogenicity of Candida albicans is enhanced in biofilms containing oral bacteria.

This study examined the influence of bacteria on the virulence and pathogenicity of candidal biofilms. Mature biofilms (Candida albicans-only, bacteria-only, C. albicans with bacteria) were generated on acrylic and either analysed directly, or used to infect a reconstituted human oral epithelium (RHOE). Analyses included Candida hyphae enumeration and assessment of Candida virulence gene expression. Lactate dehydrogenase (LDH) activity and Candida tissue invasion following biofilm infection of the RHOE were also measured. Candida hyphae were more prevalent (p < 0.05) in acrylic biofilms also containing bacteria, with genes encoding secreted aspartyl-proteinases (SAP4/SAP6) and hyphal-wall protein (HWP1) up-regulated (p < 0.05). Candida adhesin genes (ALS3/EPA1), SAP6 and HWP1 were up-regulated in mixed-species biofilm infections of RHOE. Multi-species infections exhibited higher hyphal proportions (p < 0.05), up-regulation of IL-18, higher LDH activity and tissue invasion. As the presence of bacteria in acrylic biofilms promoted Candida virulence, consideration should be given to the bacterial component when managing denture biofilm associated candidoses.

Interleukin-18 enhances a Th2 biased response and susceptibility to Leishmania mexicana in BALB/c mice.

Interleukin-18 deficient mice on a BALB/c background display increased resistance to cutaneous infection with Leishmania mexicana, with reduced lesion progression and reduced parasite burdens compared with wild-type mice. Infected IL-18-/- mice had lower antigen specific IgG1 levels and total IgE levels and conversely higher antigen specific IgG2a levels than similarly infected wild-type mice. Splenocytes isolated from infected IL-18-/- mice produced significantly lower levels of antigen induced IL-4 and higher levels of IFN-gamma than wild-type animals. Consequently IL-18 during L. mexicana infection of BALB/c mice promotes a Th2 biased response and thereby has a disease exacerbating role.

IL-15 mediates antigen-induced neutrophil migration by triggering IL-18 production.

We have investigated the mechanisms underlying IL-15-induced neutrophil migration into inflamed tissues. IL-15 induced neutrophil migration to the peritoneal cavity in mice in a time- and dose-dependent manner. The cell migration was not induced in IL-18-/-, MIP-1alpha (CCL3)-/-, TNFR1-/- or 5-LOX-/- mice but was normal in IFN-gamma-/- mice. IL-15-induced neutrophil migration was inhibited by anti-MIP-2 (CXCL2) antibody or MK886 (leukotriene synthesis inhibitor). IL-18-induced neutrophil migration was also dependent on TNFR1, MIP-1alpha, MIP-2 and leukotriene. Consistent with this observation, IL-15 induced IL-18 production, and IL-15 or IL-18 injection induced the production of MIP-2, MIP-1alpha, TNF-alpha and LTB4. In an antigen-specific inflammation model, ovalbumin (OVA)-induced neutrophil migration was completely inhibited by soluble IL-15Ralpha (sIL-15Ralpha) or anti-MIP-2 antibody. Furthermore, cell migration was absent in IL-18-/-, MIP-1alpha-/-, TNFR1-/-, or 5-LOX-/- mice. OVA challenge induced the release of MIP-2, MIP-1alpha, TNF-alpha and LTB4 in the peritoneal cavity in an IL-15- and IL-18-dependent manner. We also found that neutrophils from the peripheral blood and synovial fluid of patients with rheumatoid arthritis produced substantial amounts of IL-18 and LTB4 following activation by IL-15. Together, these results demonstrate that IL-15 plays an important role in antigen-induced neutrophil migration during inflammation, triggering a sequential OVA, IL-15, IL-18, MIP-2, MIP-1alpha, TNF-alpha, LTB4 and neutrophil migration signaling cascade.

IL-15 mediates immune inflammatory hypernociception by triggering a sequential release of IFN-gamma, endothelin, and prostaglandin.

IL-15 is closely associated with inflammatory diseases. IL-15 targeting is effective in treating experimental and clinical rheumatoid arthritis (RA). Because hyperalgesia accompanies RA, we investigated the ability of IL-15 to induced nociceptor sensitization (hypernociception). We report here that IL-15 induced time- and dose-dependent mechanical hypernociception in mice. IL-15-induced hypernociception was inhibited by treatment with a dual endothelin receptor type A (ET(A))/endothelin receptor type B (ET(B)) antagonist (bosentan), ET(A) receptor antagonist (BQ123), or cyclooxygenase inhibitor (indomethacin). Moreover, IL-15 failed to induce hypernociception in IFN-gamma(-/-) mice, suggesting that IL-15 mediated hypernociception via an IFN-gamma-, endothelin (ET)-, and prostaglandin-dependent pathway. Consistent with this finding, IFN-gamma and ET-1 induced dose- and time-dependent mechanical hypernociception that was inhibited by BQ123 or indomethacin but not BQ788 (an ET(B) receptor antagonist). IFN-gamma induced the production of ET-1 and the expression of its mRNA precursor (preproET-1, PPET-1). Moreover, IL-15 also induced ET-1 production and PPET-1 mRNA expression in an IFN-gamma-dependent manner. Prostaglandin E(2) (PGE(2)) production was induced by IL-15, IFN-gamma, or ET-1. We also found that hypernociception induced by ovalbumin (OVA) in OVA-immunized mice was significantly diminished by treatment with sIL-15Ralpha (soluble IL-15 receptor alpha-chain), bosentan, BQ123, or indomethacin. Furthermore, OVA challenge induced the expression of PPET-1 mRNA in WT mice but not in IFN-gamma(-/-) mice. The PPET-1 mRNA expression was also inhibited by sIL-15Ralpha pretreatment. Therefore, our results demonstrate the sequential mechanical hypernociceptive effect of IL-15 --> IFN-gamma --> ET-1 --> PGE(2) and suggest that these molecules may be targets of therapeutic intervention in antigen-induced hypernociception.