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Listeria monocytogenes-Induced Cell Death Inhibits the Generation of Cell-Mediated Immunity.

ABSTRACT: The influence of cell death on adaptive immunity has been studied for decades. Despite these efforts, the intricacies of how various cell death pathways shape immune responses in the context of infection remain unclear, particularly with regard to more recently discovered pathways such as pyroptosis. The emergence of Listeria monocytogenes as a promising immunotherapeutic platform demands a thorough understanding of how cell death induced in the context of infection influences the generation of CD8⁺ T-cell-mediated immune responses. To begin to address this question, we designed strains of L. monocytogenes that robustly activate necrosis, apoptosis, or pyroptosis. We hypothesized that proinflammatory cell death such as necrosis would be proimmunogenic while apoptosis would be detrimental, as has previously been reported in the context of sterile cell death. Surprisingly, we found that the activation of any host cell death in the context of L. monocytogenes infection inhibited the generation of protective immunity and specifically the activation of antigen-specific CD8⁺ T cells. Importantly, the mechanism of attenuation was unique for each type of cell death, ranging from deficits in costimulation in the context of necrosis to a suboptimal inflammatory milieu in the case of pyroptosis. Our results suggest that cell death in the context of infection is different from sterile-environment-induced cell death and that inhibition of cell death or its downstream consequences is necessary for developing effective cell-mediated immune responses using L. monocytogenes-based immunotherapeutic platforms.

SUBMITTER: Theisen E

PROVIDER: S-EPMC5203660 | biostudies-literature | 2017 Jan

REPOSITORIES: biostudies-literature

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Listeria monocytogenes-Induced Cell Death Inhibits the Generation of Cell-Mediated Immunity.

Theisen Erin E Sauer John-Demian JD

Infection and immunity 20161229 1

The influence of cell death on adaptive immunity has been studied for decades. Despite these efforts, the intricacies of how various cell death pathways shape immune responses in the context of infection remain unclear, particularly with regard to more recently discovered pathways such as pyroptosis. The emergence of Listeria monocytogenes as a promising immunotherapeutic platform demands a thorough understanding of how cell death induced in the context of infection influences the generation of ...[more]

PMID: 27821585

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Project description:The physiological basis of the hypothesis that temperature is the primary governing factor of bacterial cell inactivation under otherwise non-growth permissive conditions was investigated. Application of simultaneous low pH (pH 3.5) and low water activity (aw = 0.9; 2.5 M NaCl) conditions, applied to L. monocytogenes strains Scott A and FW03/0035, and increasing incubation temperature from 25°C up to 45°C resulted in increased permeability to ethidium homodimer-1 and corresponded to accelerated declines in esterase activity and ATP basal levels but did not result in autolysis. Triphasic survival curves were readily observable when sufficiently large cell populations were inactivated at 25°C and 35°C; indicative of a mixture of sensitive and resistant sub-populations. Enrichment-based recovery experiments however indicate that the stress conditions eventually lead to complete loss of reproductive capacity, potentially corresponding to an irreversible collapse of pH homeostasis. Transcriptomic analyses were used to further obtain insights into the physiology of the inactivation process occurring at 25°C. RT-PCR, rifampin-enforced decay and microarray experiments revealed transcripts of tufA and other genes become substantially more stable during inactivation during exposure to combined low pH/aw and during non-growth permissive temperature exposure. Gene transcripts were delineated through K-means clustering that appear to be important for initial survival of combined low pH/aw and include an overrepresentation of SigB-activated genes, the response of which fades with increasing time of inactivation exposure. The microarray component of the experiments had the aim of determining: i) Gene expression responses of L. monocytogenes strain Scott A when exposed to a non-growth permissive environment consisting of a broth system acting as a food simulated environment adjusted to low pH (pH 3.5) and low water activity (2.5 M NaCl). ii) To examine the trend in gene expression over time under inactivating (killing) conditions by applying gene set (functional and regulatory) expression trend analysis and K-means cluster analysis. iii) To correlate this data to other physiological and mRNA quantification (real-time-PCR) data.

Project description:The physiological basis of the hypothesis that temperature is the primary governing factor of bacterial cell inactivation under otherwise non-growth permissive conditions was investigated. Application of simultaneous low pH (pH 3.5) and low water activity (aw = 0.9; 2.5 M NaCl) conditions, applied to L. monocytogenes strains Scott A and FW03/0035, and increasing incubation temperature from 25Â°C up to 45Â°C resulted in increased permeability to ethidium homodimer-1 and corresponded to accelerated declines in esterase activity and ATP basal levels but did not result in autolysis. Triphasic survival curves were readily observable when sufficiently large cell populations were inactivated at 25Â°C and 35Â°C; indicative of a mixture of sensitive and resistant sub-populations. Enrichment-based recovery experiments however indicate that the stress conditions eventually lead to complete loss of reproductive capacity, potentially corresponding to an irreversible collapse of pH homeostasis. Transcriptomic analyses were used to further obtain insights into the physiology of the inactivation process occurring at 25Â°C. RT-PCR, rifampin-enforced decay and microarray experiments revealed transcripts of tufA and other genes become substantially more stable during inactivation during exposure to combined low pH/aw and during non-growth permissive temperature exposure. Gene transcripts were delineated through K-means clustering that appear to be important for initial survival of combined low pH/aw and include an overrepresentation of SigB-activated genes, the response of which fades with increasing time of inactivation exposure. The microarray component of the experiments had the aim of determining: i) Gene expression responses of L. monocytogenes strain Scott A when exposed to a non-growth permissive environment consisting of a broth system acting as a food simulated environment adjusted to low pH (pH 3.5) and low water activity (2.5 M NaCl). ii) To examine the trend in gene expression over time under inactivating (killing) conditions by applying gene set (functional and regulatory) expression trend analysis and K-means cluster analysis. iii) To correlate this data to other physiological and mRNA quantification (real-time-PCR) data. Experimental design: Two biologically replicated control cultures (each with two technical replicate sper chip) were labelled with Cy3 for each treatment sample for a total of 4 pairs of biological replicates. The treatments consisted of treated (inactivated in brain-heart infusion broth at pH 3.5 and water activity 0.9) L. monocytogenes cells with two biological replicates (each with two technical replicates per chip) labelled with Cy5. The time course (incubation time under inactivating conditions) of treatments was âinitialâ (20 minutes), 24 h, 48 h, and 72 h.

Dataset Information

Listeria monocytogenes-Induced Cell Death Inhibits the Generation of Cell-Mediated Immunity.

Publications

Listeria monocytogenes-Induced Cell Death Inhibits the Generation of Cell-Mediated Immunity.

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