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MyD88 is pivotal for immune recognition of Citrobacter koseri and astrocyte activation during CNS infection.

ABSTRACT: Citrobacter koseri (C. koseri) is a Gram-negative bacterium that can cause a highly aggressive form of neonatal meningitis, which often progresses to establish multi-focal brain abscesses. The roles of Toll-like receptor 4 (TLR4) and its signaling adaptor MyD88 during CNS C. koseri infection have not yet been examined, which is important since recent evidence indicates that innate immune responses are tailored towards specific pathogen classes. Here TLR4 WT (C3H/FeJ) and TLR4 mutant (C3H/HeJ) mice as well as MyD88 KO animals were infected intracerebrally with live C. koseri, resulting in meningitis and ventriculitis with accompanying brain abscess formation. MyD88 KO mice were exquisitely sensitive to C. koseri, demonstrating enhanced mortality rates and significantly elevated bacterial burdens compared to WT animals. Interestingly, although early proinflammatory mediator release (i.e. 12 h) was MyD88-dependent, a role for MyD88-independent signaling was evident at 24 h, revealing a compensatory response to CNS C. koseri infection. In contrast, TLR4 did not significantly impact bacterial burdens or proinflammatory mediator production in response to C. koseri. Similar findings were obtained with primary astrocytes, where MyD88-dependent pathways were essential for chemokine release in response to intact C. koseri, whereas TLR4 was dispensable; implicating the involvement of alternative TLRs since highly enriched astrocytes did not produce IL-1 upon bacterial exposure, which also signals via MyD88. Collectively, these findings demonstrate the importance of MyD88-dependent mechanisms in eliciting maximal proinflammatory responses, astrocyte activation, and bacterial containment during CNS C. koseri infection, as well as a late-phase MyD88-independent signaling pathway for cytokine/chemokine production.

SUBMITTER: Liu S

PROVIDER: S-EPMC3101120 | biostudies-literature | 2011 Apr

REPOSITORIES: biostudies-literature

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MyD88 is pivotal for immune recognition of Citrobacter koseri and astrocyte activation during CNS infection.

Liu Shuliang S Kielian Tammy T

Journal of neuroinflammation 20110416

Citrobacter koseri (C. koseri) is a Gram-negative bacterium that can cause a highly aggressive form of neonatal meningitis, which often progresses to establish multi-focal brain abscesses. The roles of Toll-like receptor 4 (TLR4) and its signaling adaptor MyD88 during CNS C. koseri infection have not yet been examined, which is important since recent evidence indicates that innate immune responses are tailored towards specific pathogen classes. Here TLR4 WT (C3H/FeJ) and TLR4 mutant (C3H/HeJ) mi ...[more]

PMID: 21496301

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Project description:MyD88 is an adaptor protein in Toll-like receptor and interleukin 1 receptor mediated signaling pathways that plays an essential role in activation of immune responses following pathogen recognition. We investigate that role in the zebrafish embryo model by using a zebrafish mutant line that contains a premature stop condon in the gene encoding MyD88, leading to a truncated protein that lacks domains important for its normal function. We infected these MyD88 mutants and wildtype individuals with Salmonella typhimurium and Edwardsiella tarda to compare the resulting immune response by transcriptome profiling on total RNA isolated from single embryos. The data derived from these microarray experiments confirms the vital role of MyD88 in pathogen recognition and provides many leads for further research. This microarray study was designed to determine the effect of a truncation of the MyD88 protein on the innate immune response of zebrafish embryos during infection with Salmonella typhimurium and Edwardsiella tarda. Embryos used in this study are derived from an incross between parents heterozygous for the mutation. Both homozygous mutants and their wildtype siblings were selected by genotyping after being injected with the bacteria or PBS as control. RNA was isolated from single embryos and each treatment group consisted of three embryos: (1) Homozygous mutants injected with PBS 8 hours post infection (hpi), (2) wildtype siblings injected with PBS 8hpi, (3) S. typhimurium-infected homozygous mutants 8hpi, (4) S. typhimurium-infected wildtype siblings 8hpi, (5) Homozygous mutants injected with PBS 8 hours post infection (hpi) (E.tarda control), (6) wildtype siblings injected with PBS 8hpi (E. tarda control), (7) E. tarda-infected homozygous mutants 8hpi, (8) E. tarda-infected wildtype siblings 8hpi. Embryos were grown at 28.5M-bM-^@M-^S30M-BM-0C in egg water and manually dechorionated at 24 hours post fertilization (hpf). Subsequently, embryos were infected at 28 hpf by micro-injecting 200 colony forming units (CFU) of S. typhimurium SL1027 or E. Tarda FL-F60, or were mock-injected with buffer as a control. After injections embryos were transferred into fresh egg water and incubated for 8 h or 4 days at 28M-BM-0C. After the incubation period, single embryos were snap-frozen in liquid nitrogen and RNA was isolated for microarray analysis. All treatment groups were analyzed using a common reference approach.

Dataset Information

MyD88 is pivotal for immune recognition of Citrobacter koseri and astrocyte activation during CNS infection.

Publications

MyD88 is pivotal for immune recognition of Citrobacter koseri and astrocyte activation during CNS infection.

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