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Pathogenesis of Candida albicans infections in the alternative chorio-allantoic membrane chicken embryo model resembles systemic murine infections.

Jacobsen ID, Grosse K, Berndt A, Hube B - PLoS ONE (2011)

Bottom Line: While many aspects of the chicken embryo response resembled murine infections, we also observed significant differences: In contrast to systemic infections in mice, IL-10 had a beneficial effect in chicken embryos.Pathogenicity of the majority of 15 tested C. albicans deletion strains was comparable to the virulence in mouse models and reduced virulence was associated with significantly lower transcription of proinflammatory cytokines.C. albicans strains locked in the yeast stage disseminated significantly more often from the CAM into the embryo, supporting the hypothesis that the yeast morphology is responsible for dissemination in systemic infections.

View Article: PubMed Central - PubMed

Affiliation: Department for Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology, Jena, Germany. ilse.jacobsen@hki-jena.de

ABSTRACT
Alternative models of microbial infections are increasingly used to screen virulence determinants of pathogens. In this study, we investigated the pathogenesis of Candida albicans and C. glabrata infections in chicken embryos infected via the chorio-allantoic membrane (CAM) and analyzed the virulence of deletion mutants. The developing immune system of the host significantly influenced susceptibility: With increasing age, embryos became more resistant and mounted a more balanced immune response, characterized by lower induction of proinflammatory cytokines and increased transcription of regulatory cytokines, suggesting that immunopathology contributes to pathogenesis. While many aspects of the chicken embryo response resembled murine infections, we also observed significant differences: In contrast to systemic infections in mice, IL-10 had a beneficial effect in chicken embryos. IL-22 and IL-17A were only upregulated after the peak mortality in the chicken embryo model occurred; thus, the role of the Th17 response in this model remains unclear. Abscess formation occurs frequently in murine models, whereas the avian response was dominated by granuloma formation. Pathogenicity of the majority of 15 tested C. albicans deletion strains was comparable to the virulence in mouse models and reduced virulence was associated with significantly lower transcription of proinflammatory cytokines. However, fungal burden did not correlate with virulence and for few mutants like bcr1Δ and tec1Δ different outcomes in survival compared to murine infections were observed. C. albicans strains locked in the yeast stage disseminated significantly more often from the CAM into the embryo, supporting the hypothesis that the yeast morphology is responsible for dissemination in systemic infections. These data suggest that the pathogenesis of C. albicans infections in the chicken embryo model resembles systemic murine infections but also differs in some aspects. Despite its limitations, it presents a useful alternative tool to pre-screen C. albicans strains to select strains for subsequent testing in murine models.

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Characterization of the course of infection in chicken embryos infected with C. glabrata ATCC2001.(A) Mortality after infection on the CAM (Kaplan-Meyer curve). N = 20 per group per experiment, two independent experiments. No significant mortality (compared to age-matched PBS control, log rank test) was observed, independent of the developmental day (DD) at infection. (B) Comparison of fungal burden in CAM, n = 10 per group, mean and SD. (C) Frequency of positive isolation in livers of embryos infected at different DD as mean and SD. Dark: positve isolation; white: no fungi isolated. (D) Representative histology of C. glabrata infected CAM. (E) Comparison of cytokine transcription in embryos infected with either C. albicans SC5314 (white) or C. glabrata ATCC2001 (grey) on DD10. N = 5 per time point, data is shown as mean and SD. Asterisks indicate statistically significant differences (P<0.05; 2-way ANOVA and Bonferroni post test).
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pone-0019741-g005: Characterization of the course of infection in chicken embryos infected with C. glabrata ATCC2001.(A) Mortality after infection on the CAM (Kaplan-Meyer curve). N = 20 per group per experiment, two independent experiments. No significant mortality (compared to age-matched PBS control, log rank test) was observed, independent of the developmental day (DD) at infection. (B) Comparison of fungal burden in CAM, n = 10 per group, mean and SD. (C) Frequency of positive isolation in livers of embryos infected at different DD as mean and SD. Dark: positve isolation; white: no fungi isolated. (D) Representative histology of C. glabrata infected CAM. (E) Comparison of cytokine transcription in embryos infected with either C. albicans SC5314 (white) or C. glabrata ATCC2001 (grey) on DD10. N = 5 per time point, data is shown as mean and SD. Asterisks indicate statistically significant differences (P<0.05; 2-way ANOVA and Bonferroni post test).

Mentions: Independent of the developmental stage at infection, C. glabrata infected embryos showed survival almost identical to PBS mock-infected controls (Fig. 5A). However, C. glabrata was able to survive and replicate in association with the CAM (Fig. 5B) without significant differences between the age groups. Dissemination occurred frequently in all age groups (Fig. 5C) and C. glabrata was isolated from 90–100% of livers 48 h p.i. Histologically, C. glabrata was found on and within the CAM (Fig. 5D). Plaque formation occurred earliest 72 h p.i. These plaques were characterized by cellular infiltrations into the mesoderm (Fig. 5D). Thus, although lacking hyphae-dependent penetration mechanisms, C. glabrata was able to enter deeper tissues and, similar to mice, C. glabrata persisted within infected embryos without gross pathological alterations and mortality.


Pathogenesis of Candida albicans infections in the alternative chorio-allantoic membrane chicken embryo model resembles systemic murine infections.

Jacobsen ID, Grosse K, Berndt A, Hube B - PLoS ONE (2011)

Characterization of the course of infection in chicken embryos infected with C. glabrata ATCC2001.(A) Mortality after infection on the CAM (Kaplan-Meyer curve). N = 20 per group per experiment, two independent experiments. No significant mortality (compared to age-matched PBS control, log rank test) was observed, independent of the developmental day (DD) at infection. (B) Comparison of fungal burden in CAM, n = 10 per group, mean and SD. (C) Frequency of positive isolation in livers of embryos infected at different DD as mean and SD. Dark: positve isolation; white: no fungi isolated. (D) Representative histology of C. glabrata infected CAM. (E) Comparison of cytokine transcription in embryos infected with either C. albicans SC5314 (white) or C. glabrata ATCC2001 (grey) on DD10. N = 5 per time point, data is shown as mean and SD. Asterisks indicate statistically significant differences (P<0.05; 2-way ANOVA and Bonferroni post test).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3094387&req=5

pone-0019741-g005: Characterization of the course of infection in chicken embryos infected with C. glabrata ATCC2001.(A) Mortality after infection on the CAM (Kaplan-Meyer curve). N = 20 per group per experiment, two independent experiments. No significant mortality (compared to age-matched PBS control, log rank test) was observed, independent of the developmental day (DD) at infection. (B) Comparison of fungal burden in CAM, n = 10 per group, mean and SD. (C) Frequency of positive isolation in livers of embryos infected at different DD as mean and SD. Dark: positve isolation; white: no fungi isolated. (D) Representative histology of C. glabrata infected CAM. (E) Comparison of cytokine transcription in embryos infected with either C. albicans SC5314 (white) or C. glabrata ATCC2001 (grey) on DD10. N = 5 per time point, data is shown as mean and SD. Asterisks indicate statistically significant differences (P<0.05; 2-way ANOVA and Bonferroni post test).
Mentions: Independent of the developmental stage at infection, C. glabrata infected embryos showed survival almost identical to PBS mock-infected controls (Fig. 5A). However, C. glabrata was able to survive and replicate in association with the CAM (Fig. 5B) without significant differences between the age groups. Dissemination occurred frequently in all age groups (Fig. 5C) and C. glabrata was isolated from 90–100% of livers 48 h p.i. Histologically, C. glabrata was found on and within the CAM (Fig. 5D). Plaque formation occurred earliest 72 h p.i. These plaques were characterized by cellular infiltrations into the mesoderm (Fig. 5D). Thus, although lacking hyphae-dependent penetration mechanisms, C. glabrata was able to enter deeper tissues and, similar to mice, C. glabrata persisted within infected embryos without gross pathological alterations and mortality.

Bottom Line: While many aspects of the chicken embryo response resembled murine infections, we also observed significant differences: In contrast to systemic infections in mice, IL-10 had a beneficial effect in chicken embryos.Pathogenicity of the majority of 15 tested C. albicans deletion strains was comparable to the virulence in mouse models and reduced virulence was associated with significantly lower transcription of proinflammatory cytokines.C. albicans strains locked in the yeast stage disseminated significantly more often from the CAM into the embryo, supporting the hypothesis that the yeast morphology is responsible for dissemination in systemic infections.

View Article: PubMed Central - PubMed

Affiliation: Department for Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology, Jena, Germany. ilse.jacobsen@hki-jena.de

ABSTRACT
Alternative models of microbial infections are increasingly used to screen virulence determinants of pathogens. In this study, we investigated the pathogenesis of Candida albicans and C. glabrata infections in chicken embryos infected via the chorio-allantoic membrane (CAM) and analyzed the virulence of deletion mutants. The developing immune system of the host significantly influenced susceptibility: With increasing age, embryos became more resistant and mounted a more balanced immune response, characterized by lower induction of proinflammatory cytokines and increased transcription of regulatory cytokines, suggesting that immunopathology contributes to pathogenesis. While many aspects of the chicken embryo response resembled murine infections, we also observed significant differences: In contrast to systemic infections in mice, IL-10 had a beneficial effect in chicken embryos. IL-22 and IL-17A were only upregulated after the peak mortality in the chicken embryo model occurred; thus, the role of the Th17 response in this model remains unclear. Abscess formation occurs frequently in murine models, whereas the avian response was dominated by granuloma formation. Pathogenicity of the majority of 15 tested C. albicans deletion strains was comparable to the virulence in mouse models and reduced virulence was associated with significantly lower transcription of proinflammatory cytokines. However, fungal burden did not correlate with virulence and for few mutants like bcr1Δ and tec1Δ different outcomes in survival compared to murine infections were observed. C. albicans strains locked in the yeast stage disseminated significantly more often from the CAM into the embryo, supporting the hypothesis that the yeast morphology is responsible for dissemination in systemic infections. These data suggest that the pathogenesis of C. albicans infections in the chicken embryo model resembles systemic murine infections but also differs in some aspects. Despite its limitations, it presents a useful alternative tool to pre-screen C. albicans strains to select strains for subsequent testing in murine models.

Show MeSH
Related in: MedlinePlus