👤 Ashley M Divens

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

Tuberculosis (TB) is the leading cause of death due to a pathogen. The live-attenuated BCG vaccine is the only approved vaccine to prevent TB, but it fails to confer long-term protection. We hypothesize that the immunosuppressive cytokine IL-27 may contribute to the inefficacies of the BCG vaccine. IL-27 is elevated in neonates, the population most commonly administered BCG, and levels increase further upon vaccination. IL-27 interferes with the phagolysosomal pathway, suggesting it may limit the diversity of antigens processed and presented to T cells. We hypothesized that in the absence of IL-27 signaling, BCG vaccination induces antigen-specific T cells that recognize a greater number of antigens and provide enhanced protection during M. tuberculosis (Mtb) challenge. CD3 Show less

Tuberculosis (TB) is a serious public health concern in many regions of the world and the only approved vaccine to prevent TB is the live-attenuated BCG vaccine. Despite being widely used, the BCG vaccine fails to prevent pulmonary TB in adults. The BCG vaccine is administered during the neonatal period when levels of the immunosuppressive cytokine interleukin (IL)-27 are elevated, and previous studies have demonstrated that the source of IL-27 can impact downstream immune responses. We therefore sought to characterize the specific subpopulations of myeloid cells that produce IL-27 following BCG vaccination. To investigate this, we administered the BCG vaccine to neonatal IL-27p28eGFP mice that report IL-27 production. Our studies demonstrated that BCG vaccination steadily increased IL-27 production throughout the weeks post-vaccination. We also showed that a predominantly CD11b+ F4/80+ population of IL-27 producers increased MHC class II expression following BCG vaccination in both the spleen and the lung. However, producers of IL-27 in these tissues differ, with a population of CD11c+ MHC II+ cells emerging in the spleen and a subset of Ly6G/C+ MHC II+ emerging in the lung. 10x scMultiome analysis further validated the increase in MHC class II expression and demonstrated improved antigen presentation functionality following vaccination. The sequencing analysis also revealed subpopulations of IL-27 producers with immunosuppressive functions such as a population of macrophages with increased Mrc1 expression post-vaccination. Our findings suggest that IL-27 producers are a heterogenous population of myeloid cells that impact the development of protective immune responses induced by the BCG vaccine. Show less

Efforts to control tuberculosis (TB), caused by the pathogen We investigated the impact of IL-27 on regulation of immune responses during neonatal BCG vaccination and protection against Mtb. Here, we used a novel model of neonatal vaccination and adult aerosol challenge that models the human timeline of vaccine delivery and disease transmission. Overall, we observed improved control of Mtb in mice unresponsive to IL-27 (IL-27Rα Our findings suggest the importance of evaluating new vaccines and approaches to combat TB in the neonatal population most likely to receive them as part of global vaccination campaigns. They further indicate that temporal strategies to antagonize IL-27 during early life vaccination may improve protection. 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