Griffith, Thomas S.

Abstract Description Sepsis, the life-threatening organ dysfunction stemming from the severe inflammatory response to systemic microbial infection, can affect humans of any age. One consequence of sepsis is the development of prolonged immunoparalysis that contributes to increased susceptibility to infection. With vaccination being an important means for protecting humans from infection throughout their lifetime, it is surprising that there has been no study performed to date assessing vaccine efficacy in sepsis survivors. We found neonatal and adult mice given an intramuscularly delivered inactivated multivalent influenza vaccine 30 days after sepsis induction had reduced total and class switched Ab titers, compared to non-septic controls. The reduced humoral response was due, in part, to impaired CD4 T cell and B cell responses to the vaccine. Reduced Ab titers were similarly seen in post-septic mice given an intranasal live-attenuated influenza vaccine. ELISpot data demonstrating reduced numbers of antibody secreting cells in the spleens of vaccinated septic mice further support the ELISA results. Moreover, mice vaccinated prior to sepsis induction also showed reduced antibody titers. Importantly, vaccinated septic mice had reduced protection to a lethal influenza challenge, demonstrated by increased mortality and viral burden in the lungs. These data collectively show how sepsis can lead to increased susceptibility to pathogens normally neutralized by vaccine-induced immunity. Funding Sources Supported by NIH/NIAID R35 GM140881; 5R01 GM139046; 1T32TR004385 Topic Categories Translational and Interventional Immunology (TI)

Abstract Activation-induced cell death of peripheral T cells results from the interaction between Fas and Fas ligand. Resting peripheral T cells are resistant to Fas-induced apoptosis and become susceptible only after their activation. We have investigated the molecular mechanism mediating the sensitization of resting peripheral T cells to Fas-mediated apoptosis following TCR stimulation. TCR activation decreases the steady state protein levels of FLIP (FLICE-like inhibitory protein), an inhibitor of the Fas signaling pathway. Reconstitution of intracellular FLIP levels by the addition of a soluble HIV transactivator protein-FLIP chimera completely restores resistance to Fas-mediated apoptosis in TCR primary T cells. Inhibition of IL-2 production by cyclosporin A, or inhibition of IL-2 signaling by rapamycin or anti-IL-2 neutralizing Abs prevents the decrease in FLIP levels and confers resistance to Fas-mediated apoptosis following T cell activation. Using cell cycle-blocking agents, we demonstrate that activated T cells arrested in G1 phase contain high levels of FLIP protein, whereas activated T cells arrested in S phase have decreased FLIP protein levels. These findings link regulation of FLIP protein levels with cell cycle progression and provide an explanation for the increase in TCR-induced apoptosis observed during the S phase of the cell cycle.

Abstract The impact of microbes on restraining the immune response to allergens has been extensively studied and is a key element of the hygiene hypothesis. Lung type 2 innate lymphoid cell responses to airway allergens can be inhibited by administration of a number of microbial products; however, it is unclear whether such an effect would be observed with natural infections and how sustained any observed inhibitory effects would be. To answer these questions, we used a murine model of physiological microbial exposures through cohousing SPF laboratory mice with pet store mice and examined the acute type 2 response to intranasally delivered fungal allergen extract Alternaria alternata. We found laboratory mice cohoused with pet store mice for two weeks display a suppressed ILC2 response to A. alternata which resulted in reduced eosinophilia. By comparison, mice cohoused for at least two months had ILC2 and eosinophil responses similar to SPF mice despite dramatic changes to the composition of the immune cell populations in the lungs. Lung ILC2 in two-month cohoused mice were still sensitive to subsequent inflammatory cues, as administration of poly(I:C) was able to suppress ILC2 activation and eosinophilia equally well in SPF and two-month cohoused animals. These findings suggest ILC2 dynamically respond to their environment and are not easily desensitized long-term.

Abstract Sepsis can result from a variety of pathogens, originating from a range of sources. A vast range of presenting symptoms is included in the catch-all term of “bacteremia,” making diagnosis and prognosis particularly troublesome. One underexplored factor contributing to disparate outcomes is the age of the patient. Neonatal sepsis in very-low-birth-weight infants can result in vastly different immunological outcomes unique from sepsis in adults. It is also becoming increasingly clear, both from preclinical experimental models and clinical observations, that the age and history of previous microbial exposures can significantly influence the course of infection from sepsis and cytokine storms to immunopathology. In this study, we will explore key differences between neonatal and adult sepsis, experimental models used to study sepsis, and how responses to the surrounding microbial universe shape development of the immune system and impact, positively or negatively, the course of disease.

Tumor necrosis factor‐related apoptosis‐inducing ligand (TRAIL) and its cognate receptor(s) are up‐regulated in human and murine nonalcoholic steatohepatitis (NASH); however, the consequence of this enhanced expression on NASH pathogenesis remains unclear. TRAIL may either accentuate liver injury by promoting hepatic steatosis and inflammation or it may mitigate the disease process by improving systemic insulin resistance and averting hepatic fibrosis. Herein, we investigated the role of TRAIL in an obesity‐induced murine model of NASH. C57BL/6 wild‐type mice and Trail –/– mice were placed on a 20‐week standard chow or a high‐fat, high‐fructose, and high‐cholesterol (FFC) diet, which induces obesity, insulin resistance, and NASH. Metabolic phenotype, liver injury, inflammation and fibrosis, and adipose tissue homeostasis were examined. FFC diet‐fed Trail –/– mice displayed no difference in weight gain and metabolic profile when compared to wild‐type mice on the same diet. All FFC‐fed mice developed significant hepatic steatosis, which was attenuated in Trail –/– mice. TRAIL deficiency also significantly decreased FFC diet‐induced liver injury as manifested by reduced serum alanine aminotransferase values, hepatic terminal deoxynucleotidyl transferase‐mediated deoxyuridine triphosphate nick‐end labeling‐positive cells, and macrophage‐associated inflammation. FFC diet‐associated hepatic stellate cell activation and hepatic collagen deposition were also abrogated in Trail –/– mice. In contrast to the liver, TRAIL deletion did not improve FFC diet‐induced adipose tissue injury and inflammation and actually aggravated insulin resistance. Conclusion: NASH pathogenesis may be dissociated from other features of the metabolic syndrome, and liver‐targeted inhibition of TRAIL signaling may be salutary. (Hepatology Communications 2017;1:648–662)