Project description:Infants and young children are more susceptible to common respiratory pathogens compared to adults, but can fare better against novel pathogens like SARS-CoV-2. The mechanisms by which infants and young children mount effective responses to respiratory pathogens are unknown. Here, we demonstrate through study of lungs and lung-associated lymph nodes (LLN) from infant and pediatric organ donors, aged 0-13 years, that bronchus-associated lymphoid tissue (BALT), develops in lungs during the first year of life. BALT structures, consisting of B cell follicles and T cell zones, increase in numbers in the early years, and subsequently decrease over childhood coincident with accumulation of memory T cells in the lung. Early life BALT contains germinal centers and supports B cell differentiation, clonal expansion, somatic hypermutation, and immunoglobulin class switching. High dimensional flow cytometry reveals seeding of lungs by newly formed B cells (transitional cells) during infancy coincident with the timing of maximal BALT formation. We further demonstrate increased lung-localized B cell responses during respiratory virus infection in infants. Together, our findings provide novel evidence for BALT as an early life adaptation for mobilizing in situ immune protection to the diverse respiratory challenges during this formative life stage.
Project description:Prenatal exposures such as infections and immunisation may influence infant responses. We had an opportunity to undertake an analysis of responses in infants within the context of a study investigating the effects of maternal mycobacterial exposures and infection on bacille Calmette-Guerin (BCG) vaccine-induced responses in Ugandan infants. Gene expression profiles for pathways associated with maternal LTBI and with maternal BCG scar were examined using samples collected at one (n=42) and six (n=51) weeks after BCG immunisation using microarray. Interferon and inflammation response pathways were up-regulated in infants of mothers with LTBI at six weeks, and in infants of mothers with a BCG scar at one and six weeks after BCG immunisation. Maternal BCG scar had a stronger association with infant responses than maternal LTBI, with an increased proinflammatory immune profile.
Project description:Infants suffer disproportionately from respiratory infections and generate reduced vaccine responses compared to adults, although underlying mechanisms remain unclear. In adult mice, lung-localized, tissue-resident memory T cells (TRM) mediate optimal protection to respiratory pathogens. We hypothesized that reduced protection in infancy was due to impaired T effector localization and/or lung TRM establishment. Using an infant mouse model we demonstrate generation of lung-homing, virus-specific T effectors following influenza infection or live-attenuated vaccination, similar to adults. However, infection during infancy generated markedly fewer lung TRM and heterosubtypic protection was reduced compared to adults. Impaired TRM establishment was infant-T cell-intrinsic and infant effectors displayed distinct transcriptional profiles enriched for T-bet-regulated genes. Notably, mouse and human infant T cells exhibited increased T-bet expression following activation and reducing T-bet levels in infant mice enhanced lung TRM establishment. Our findings reveal that infant T cells are intrinsically programmed for short-term responses and targeting key regulators could promote long-term, tissue-targeted protection at this critical life stage.
Project description:Redundant mechanisms support IgA responses to intestinal antigens. These include multiple priming sites (mesenteric lymph nodes (MLN), Peyer's patches and isolated lymphoid follicles) and various cytokines that promote class switch to IgA, even in the absence of T cells. In spite of these back-up mechanisms, vaccination against enteric pathogens such as Rotavirus has limited success in some populations.Genetic and environmental signals experienced during early life are known to influence mucosal immunity, yet the mechanisms for how these exposures operate remain unclear. Here we used Rotavirus infection to follow antigen-specific IgA responses through time and in different gut compartments. Using genetic and pharmacological approaches, we tested the role of a pathway known to support IgA responses (Lymphotoxin - LT) at different developmental stages. We found that LT-beta receptor (LTβR) signalling in early life programs intestinal IgA responses in adulthood by affecting antibody class switch recombination to IgA and subsequent generation of IgA antibody-secreting cells within an intact MLN. In addition, early life LTβR signalling dictates the phenotype and function of MLN stromal cells in order to support IgA responses in the adult. Collectively, our studies uncover new mechanistic insights into how early life LTβR signalling impacts mucosal immune responses during adulthood.
Project description:Redundant mechanisms support IgA responses to intestinal antigens. These include multiple priming sites (mesenteric lymph nodes (MLN), Peyer's patches and isolated lymphoid follicles) and various cytokines that promote class switch to IgA, even in the absence of T cells. In spite of these back-up mechanisms, vaccination against enteric pathogens such as Rotavirus has limited success in some populations.Genetic and environmental signals experienced during early life are known to influence mucosal immunity, yet the mechanisms for how these exposures operate remain unclear. Here we used Rotavirus infection to follow antigen-specific IgA responses through time and in different gut compartments. Using genetic and pharmacological approaches, we tested the role of a pathway known to support IgA responses (Lymphotoxin - LT) at different developmental stages. We found that LT-beta receptor (LTβR) signalling in early life programs intestinal IgA responses in adulthood by affecting antibody class switch recombination to IgA and subsequent generation of IgA antibody-secreting cells within an intact MLN. In addition, early life LTβR signalling dictates the phenotype and function of MLN stromal cells in order to support IgA responses in the adult. Collectively, our studies uncover new mechanistic insights into how early life LTβR signalling impacts mucosal immune responses during adulthood.
Project description:Infants necessitate vaccinations to prevent life-threatening infections. Our understanding of the infant immune responses to routine vaccines remains limited. We analyzed two cohorts of 2-month-old infants before vaccination, one week, and one-month post-vaccination. We report remarkable heterogeneity but limited antibody responses to the different antigens. Whole-blood transcriptome analysis in an initial cohort showed marked overexpression of interferon-stimulated genes (ISGs) and to a lesser extent of inflammation-genes at day 7, which normalized one month post-vaccination. Single-cell RNA sequencing in peripheral blood mononuclear cells from a second cohort identified at baseline a predominantly naive immune landscape including ISGhi cells. On day 7, increased expression of interferon-, inflammation-, and cytotoxicity-related genes were observed in most immune cells, that reverted one month post-vaccination, when a CD8+ ISGhi and cytotoxic cluster and B cells expanded. Antibody responses were associated with baseline frequencies of plasma cells, B-cells, and monocytes, and induction of ISGs at day 7.
Project description:Colonizing commensal bacteria after birth are required for the proper development of the gastrointestinal tract. It is believed that bacterial colonization pattern in neonatal gut affects gut barrier function and immune system maturation. Studies on the development of faecal flora microbiota in infants on various formula feeds showed that the neonatal gut was first colonized with enterococci followed by other flora microbiota such as Bifidobacterium in breast feeding infants. Intriguingly, Bjorksten group Other studies showed that Bbabies who developed allergy were less often colonized with Enterococcus during the first month of life as compared to healthy infants. A lot of Many studies have been done on conducted to elucidate how bifidobacteria or lactobacilli, some of which are considered probiotic, regulate infant gut immunity. However, much fewer studies have been focused on enterococi. In our study, we demonstrate that E. faecalis, isolated from healthy newborns, suppress inflammatory responses activated in vivo and in vitro. We found E. faecalis attenuates proinflammatory cytokine secretions, especially IL-8, through JNK and p38 signaling pathways. This finding shed light on how the first colonizer, E.faecalis, regulate inflammatory responses in the host. Samples are analysed using web-based GEArray Expression Analysis Suite
Project description:Introduction: Thymic Stromal Lymphopoietin (TSLP) is a primarily epithelial-derived cytokine that drives type 2 allergic immune responses. Early life viral respiratory infections elicit high TSLP production, which leads to the development of type 2 inflammation and airway hyperreactivity. The goal of this study was to examine in vivo and in vitro the human airway epithelial responses leading to high TSLP production during viral respiratory infections in early infancy. Methods: A total of 129 infants (<1m – 24m, median age 10m) with severe viral respiratory infections were enrolled for in vivo (n=113), and in vitro studies (n=16). Infants were classified as “high TSLP” or “low TSLP” for values above or below the 50th percentile. High vs. low TSLP groups were compared in terms of type I-III IFN responses and production of chemokines promoting antiviral (CXCL10), neutrophilic (CXCL1, CXCL5, CXCL8), and type 2 responses (CCL11, CCL17, CCL22). Human infant airway epithelial cell (AEC) cultures were used to define the transcriptomic (RNAseq) profile leading to high vs. low TSLP responses in vitro. Results: Infants in the high TSLP group had greater in vivo type III IFN airway production (median type III IFN in high TSLP 183.2 pg/ml vs. 63.4 pg/ml in low TSLP group, p= 0.007) and increased in vitro type I-III IFN AEC responses after stimulation with a viral mimic (poly I:C). Our RNAseq data showed that infants in the high TSLP group had significant baseline upregulation of IFN signature genes (e.g., IFIT2, IFI6, MX1) and pro-inflammatory chemokine genes prior to viral mimic stimulation. Infants in the high TSLP group also showed a baseline AEC pro-inflammatory state characterized by increased production of all the chemokines assayed (e.g., CXCL10, CXCL8) in the absence of viral stimuli. Conclusion: High TSLP responses in the human infant airways are associated with pre-activated airway epithelial IFN antiviral immunity and increased baseline AEC production of pro-inflammatory chemokines. These findings present a new paradigm underlying the high production of TSLP in the human infant airway epithelium and shed light on the pathogenesis of viral respiratory illnesses during early infancy and beyond childhood.