Cold-blooded vertebrate utilizes behavioral fever to alleviate T-cell apoptosis and optimize antimicrobial immunity
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ABSTRACT: Fever confers significant survival benefits on endotherms by optimizing both innate and adaptive immunity. Ectotherms achieve thermoregulation using behavioral strategies, but existing evidence supports its enhancement effect on innate immunity only. Therefore, it remains unknown whether the coordination between fever and adaptive immunity was independently acquired by endotherms or instead represents a gradually evolved function common to vertebrates. In the present study, we reported that Nile tilapia developed behavioral fever to enhance the immune response against Edwardsiella piscicida infection. Behavioral fever lasted five days, and the immune potential was optimized at 4–6 days post infection, indicating a potential correlation between fever events and T-cell immunity. Further investigation suggested that fever did not affect T-cell activation or proliferation but improved the ability of T cells to produce IFN- and Granzyme B and enhanced cytotoxicity, thereby eliminating the infection more effectively. Notably, we identified a previously unknown advantage conferred by fever during infection: alleviation of T-cell apoptosis to maintain a considerable T-cell pool. Mechanistically, fever induced the expression of HSP70, which in turn entered the nucleus and bound to and promoted the phosphorylation of ERK1/2, thereby inhibiting the cleavage of caspase-8/caspase-3 and preventing T-cell apoptosis. Our findings elucidate the detailed mechanism by which behavioral fever optimizes T-cell immunity in a cold-blooded vertebrate and propose that integrating fever with adaptive immunity to gain survival advantages is an ancient strategy acquired before the emergence of tetrapod.
Project description:The transcriptomic analysis was evaluated using RNA-seq of salmon challenged with the birnavirus IPNv under two different thermal conditions: (a) constant temperature (mean temperature 15 ± 0.9 ºC, “No-Fever”) and (b) temperature gradient (mean temperature 15 ± 7.4 ºC, “Fever”). In parallel, fish in another tank were treated by adding 100 ml virus free cell culture supernatant to the water (mean temperature 15 ± 7.4 ºC, "mock-infected"). We identified a specific transcriptomic signature for each group in the RNA-seq data and identifying a set of key components that control inflammatory modulation during behavioural fever upon viral infection in mobile ectotherms.
Project description:The adaptor protein ASC contributes to innate immunity through the assembly of caspase-1-activating inflammasome complexes. We demonstrate that ASC plays an inflammasome-independent cell-intrinsic role in adaptive immune cells. Asc-/- mice displayed defective antigen presentation by dendritic cells and lymphocyte migration due to impaired Rac-mediated actin polymerization. Genome-wide analysis showed that ASC, but not Nlrp3 or caspase-1, controls mRNA stability and expression of DOCK2, a guanine nucleotide exchange factor that mediates Rac-dependent signaling in immune cells. DOCK2-deficient dendritic cells showed similar defective antigen uptake as Asc-/- cells. Ectopic expression of DOCK2 in ASC-deficient cells restored Rac-mediated actin polymerization, antigen uptake and chemotaxis. Thus, ASC shapes adaptive immunity independently of inflammasomes by modulating DOCK2-dependent Rac activation and F-actin polymerization in dendritic cells and lymphocytes. Three replicates of naïve WT and three replicates of Asc-/- bone marrow derived dendritic cells were analyzed on the Affymetrix HT MG-430 PM plate array.
Project description:The adaptor protein ASC contributes to innate immunity through the assembly of caspase-1-activating inflammasome complexes. We demonstrate that ASC plays an inflammasome-independent cell-intrinsic role in adaptive immune cells. Asc-/- mice displayed defective antigen presentation by dendritic cells and lymphocyte migration due to impaired Rac-mediated actin polymerization. Genome-wide analysis showed that ASC, but not Nlrp3 or caspase-1, controls mRNA stability and expression of DOCK2, a guanine nucleotide exchange factor that mediates Rac-dependent signaling in immune cells. DOCK2-deficient dendritic cells showed similar defective antigen uptake as Asc-/- cells. Ectopic expression of DOCK2 in ASC-deficient cells restored Rac-mediated actin polymerization, antigen uptake and chemotaxis. Thus, ASC shapes adaptive immunity independently of inflammasomes by modulating DOCK2-dependent Rac activation and F-actin polymerization in dendritic cells and lymphocytes.
Project description:Baris Hancioglu, David Swigon & Gilles Clermont. A dynamical model of human immune response to influenza A virus infection. Journal of Theoretical Biology 246, 1 (2007).
We present a simplified dynamical model of immune response to uncomplicated influenza A virus (IAV) infection, which focuses on the control of the infection by the innate and adaptive immunity. Innate immunity is represented by interferon-induced resistance to infection of respiratory epithelial cells and by removal of infected cells by effector cells (cytotoxic T-cells and natural killer cells). Adaptive immunity is represented by virus-specific antibodies. Similar in spirit to the recent model of Bocharov and Romanyukha [1994. Mathematical model of antiviral immune response. III. Influenza A virus infection. J. Theor. Biol. 167, 323-360], the model is constructed as a system of 10 ordinary differential equations with 27 parameters characterizing the rates of various processes contributing to the course of disease. The parameters are derived from published experimental data or estimated so as to reproduce available data about the time course of IAV infection in a naïve host. We explore the effect of initial viral load on the severity and duration of the disease, construct a phase diagram that sheds insight into the dynamics of the disease, and perform sensitivity analysis on the model parameters to explore which ones influence the most the onset, duration and severity of infection. To account for the variability and speed of adaptation of the adaptive response to a particular virus strain, we introduce a variable that quantifies the antigenic compatibility between the virus and the antibodies currently produced by the organism. We find that for small initial viral load the disease progresses through an asymptomatic course, for intermediate value it takes a typical course with constant duration and severity of infection but variable onset, and for large initial viral load the disease becomes severe. This behavior is robust to a wide range of parameter values. The absence of antibody response leads to recurrence of disease and appearance of a chronic state with nontrivial constant viral load.
Project description:Purpose: This goal of this study was to explore the host transcriptomic responses in African swine fever virus experimentally infected pigs using RNA-Sequencing. Methods: RNAs acquired from ten different organ tissue samples were sequenced. Sequencing reads were preprocessed, aligned with the reference genome, assembled and expressions were estimated through bioinformatics approaches. Result: Several uprugulated DEGs were identified. Conclusion: We found important candidate genes and pathways for further testing in African swine fever virus infection in pig.
Project description:Different types of cell death, including apoptosis, play an important role in the immune defense of arthropods, as infected cells are eliminated, preventing the dissemination of the infectious agent throughout the animal body. The apoptosis can be triggered by two main pathways: the intrinsic or mitochondrial pathway and the extrinsic or death receptor pathway. Both culminate in the activation of the effector caspases, such as caspase-3, resulting, for instance in DNA fragmentation and exposition of markers on the surface of the apoptotic cell, allowing its recognition and elimination by phagocytic cells. To ensure survival and proliferation, microorganisms can inhibit apoptosis of the host cell. The differential proteome of a tick cell line (BME26) in response to an experimental infection with Rickettsia rickettsii, causative agent of the severe Rocky Mountain spotted fever, showed that pro-apoptotic proteins are downregulated in the beginning of infection (6 h) and upregulated in a later time-point (48 h). We therefore evaluated the effects of infection on classic features of apoptotic cells: the spontaneous fragmentation of gDNA and the activity of caspase-3 and the exposition of phosphatidylserine in BME26 cells after induction with staurosporine, a classic activator of apoptosis. The spontaneous fragmentation of DNA was observed exclusively in non-infected cells. In addition, the activity of caspase-3 and the exposition of phosphatidylserine is lower in infected than in non-infected cells. Caspase-3 activity is also lower in infected IBU/ASE-16 cells, an embryonic tick cell line of one primary vector of R. rickettsii in Brazil, Amblyomma sculptum. Importantly, while the activation of caspase-3 exerted a detrimental effect on rickettsial proliferation in BME26 cells, the enzyme inhibition increased bacterial growth. Together, our results suggest that R. rickettsii controls the apoptosis in tick cells, which seems to be important to ensure the colonization of the vector cell. To the best of our knowledge, this is the first report on the modulation of the apoptosis in a tick cell line upon the infection with a species of the genus Rickettsia.
Project description:Immunity to malaria can be acquired through natural exposure to Plasmodium falciparum (Pf), but only after years of repeated infections. Typically, this immunity is acquired by adolescence and confers protection against disease, but not Pf infection per se. Efforts to understand the mechanisms of this immunity are integral to the development of a vaccine that would mimic the induction of adult immunity in children. The current study applies transcriptomic analyses to a cohort from the rural village of Kalifabougou, Mali, where Pf transmission is intense and seasonal. Signatures that correlate with protection from malaria may yield new hypotheses regarding the biological mechanisms through which malaria immunity is induced by natural Pf infection. The resulting datasets will be of considerable value in the urgent worldwide effort to develop a malaria vaccine that could prevent more than a million deaths annually. 108 samples; paired pre- and post-challenge for 54 individuals 198 samples; paired pre- and post-challenge for 99 individuals
Project description:CD8 T cells play an importart role in adaptive immunity to intracellular pathogens. Naïve CD8 T cells , that have not encountered antigen previously can be identified by virtue of their distinct phenotype. Upon antigenic encounter, they proliferate rapidly and undergo massive reprograming to differentiate to cytotoxic T lymphocytes. The yellow fever live virus vaccine (YF-17D) provides a model primary acute viral infection that can be used to follow this response.Here we characterize the resting, non-activated naive CD8 T cells in nine healthy adults and YF-specific CD8 T cells elicited in response to YF-17D vaccination from the same donors during the effector (2 weeks after vaccination) and memory (5-8 months later) stages.
Project description:Innate lymphoid cells (ILCs) are considered to be the innate counterparts of adaptive T lymphocytes and play important roles in host defense, tissue repair, metabolic homeostasis, and inflammatory diseases. ILCs are generally thought of as tissue-resident cells, but whether ILCs strictly behave in a tissue-resident manner or can move between sites during infection is unclear. We show here that IL-25- or helminthic infection-induced inflammatory ILC2s are not tissue-resident but circulating cells, which arise from resting ILC2s residing in intestinal lamina propria and then migrate to mesenteric lymph nodes, spleen, lung, and liver. IL-25 induces rapid proliferation of the intestinal ILC2s and a change in their sensitivity to S1P-mediated chemotaxis, leading to lymphatic entry, blood circulation, and accumulation in periphery sites, including the lung where they contribute to anti-helminth defense and tissue repair. Our finding of cytokine-driven expansion and migration of innate lymphocytes, a behavioral parallel to the antigen-driven priming, expansion, and migration of adaptive lymphocytes to effector sites in distant tissues, provides a significant advance in our overall understanding of ILCs and indicates that ILCs complement adaptive immunity by providing both local and distant site effector protection during infection.