👤 Madhavi Annamanedi

Interleukin-27 (IL-27) is a cytokine that belongs to the IL-6/IL-12 cytokine family with diverse influences on the immune response. Elevated levels of IL-27 cytokine during the neonatal period predispose neonatal mice to more severe infection. Neonatal pups deficient in IL-27 signaling exhibit improved survival and bacterial clearance with reduced systemic inflammation. However, the precise molecular mechanisms that regulate bacterial clearance and the overall immune response in IL-27 receptor a-deficient (KO) mice during neonatal sepsis remain incompletely defined. Analysis of the transcriptome of the neonatal spleen during The results uncovered that during infection WT neonatal mice fail to increase expression of CXCR2 but upregulate the cognate ligand CXCL2 significantly. Conversely, IL-27Rα KO neonates increase CXCR2 expression significantly in the spleen during infection but fail to upregulate CXCL2 transcripts. Splenocytes isolated form septic neonatal KO mice migrated with superior efficiency towards the chemokine CXCL2 compared to WT counterparts. Surprisingly, we also found that splenic monocytes but not the neutrophils account for higher CXCR2 gene expression in the IL-27Rα KO neonatal mice. Monocytes isolated from the spleens of both WT and IL-27Rα KO neonatal pups confirmed that the concentration of CXCL2 regulates CXCR2 receptor expression. We further demonstrated that with regulated CXCL2 chemokine expression levels, IL-27Ra-deficient neonatal mice had more CXCR2+ mononuclear cells present at the site of infection. Overall, our findings suggest that during infection in the absence of IL-27 signaling, a differential expression of CXCR2 and CXCL2 promotes increased migration of mononuclear cells consistent with improved bacterial clearance and tissue homeostasis. This study defines mechanisms that improve the host response in the absence of IL-27 signaling during neonatal sepsis and reinforces the potential for antagonizing IL-27 as a host-directed therapy for neonatal sepsis. Show less

Neonates have increased vulnerability to life-threatening infections due to the distinct immune landscape. Interleukin (IL)-27 is a key component of this immune profile that we have previously shown to be elevated in both newborn humans and mice. IL-27 continues to increase in the serum and tissues consistent with poor outcomes during gram-negative neonatal bacterial sepsis. Presently, we dissected the IL-27 producer profile at a single-cell level using IL-27p28eGFP reporter mice in our previously established model of neonatal sepsis with luciferase-expressing K1-encapsulated Escherichia coli. Whole animal imaging regionally highlighted the spleen, liver, and lungs as key infection sites by bacterial luminescence. Flow cytometry showed that IL-27 producers increased significantly in the liver with infection and were predominantly F4/80+ and CD11b+ with subpopulations that emerged expressing additional markers. This information paired with single-cell RNA sequencing further identified the most robust populations as monocytes, monocyte-derived cells, and Kupffer cells followed by smaller populations of dendritic cells and neutrophils. The transcriptome demonstrated a diverse range of functionality amongst populations that included differential expression of genes implicated in bactericidal, metabolic, and inflammatory changes. Collectively, the transcriptome of IL-27 producers from the livers of infected animals suggests an uncoordinated mix of inflammatory and suppressive activity that may contribute to immune dysregulation characteristic of sepsis. Together, this work provides previously undescribed insight into the details of IL-27 producers during early-life infection. This further provides essential information needed to support IL-27 as a therapeutic target for neonatal bacterial sepsis. Show less

Interleukin (IL)-27 is a heterodimeric immunoregulatory cytokine expressed at elevated levels early in life that compromises bacterial clearance and promotes severe outcomes during neonatal sepsis. In turn, IL-27Rα-deficient neonatal mice exhibit better control of bacteria, reduced systemic inflammation, and improved outcomes. IL-27 primarily activates and signals through either Signal transducer and activator of transcription (STAT)-1 or STAT-3 in macrophages. Targeted deletion of STAT-3 in macrophages has been reported to improve responsiveness to Lipopolysaccharide (LPS) and promote Th1 activity. As such, in the present study, we investigated the role of STAT-3 signaling in IL-27-mediated suppression of bacterial clearance and lysosomal activity in neonatal macrophages during The neonatal period is a time in which newborns have increased vulnerability and the highest risk of death from infection. This includes sepsis for which there is a considerable global burden of disease. We have determined that the cytokine interleukin (IL)-27 is expressed at elevated levels in the first days of life and continues to rise during experimental bacterial neonatal sepsis. Neonatal mice that cannot respond to IL-27 exhibit improved outcomes. In this work, we have investigated the influence of STAT-3 on control of bacteria and inflammation during IL-27 signaling in neonates. It is critical that we understand mechanisms that underlie neonatal susceptibility to infection so that we can identify new targets for therapeutic intervention. Here, we define the value of STAT-3 in approaches to targeted therapies for bacterial neonatal sepsis. Show less

Human neonates are predisposed to an increased risk of mortality from infection due to fundamental differences in the framework of innate and adaptive immune responses relative to those in the adult population. As one key difference in neonates, an increase in the immunosuppressive cytokine, IL-27, is responsible for poor outcomes in a murine neonatal model of bacterial sepsis. In our model, the absence of IL-27 signaling during infection is associated with improved maintenance of body mass, increased bacterial clearance with reduced systemic inflammation, and decreased mortality rates that correlate to preservation of glucose homeostasis and insulin production. To further elucidate the mechanisms associated with IL-27 signaling and metabolic fitness, we analyzed global transcriptomes from spleen, liver, pancreas, and hindlimb muscle during Show less

Human newborns exhibit increased vulnerability and risk of mortality from infection that is consistent with key differences in the innate and adaptive immune responses relative to those in adult cells. We have previously shown an increase in the immune suppressive cytokine, IL-27, in neonatal cells and tissues from mice and humans. In a murine model of neonatal sepsis, mice deficient in IL-27 signaling exhibit reduced mortality, increased weight gain, and better control of bacteria with reduced systemic inflammation. To explore a reprogramming of the host response in the absence of IL-27 signaling, we profiled the transcriptome of the neonatal spleen during Show less