Biomarkers of post-discharge mortality among children with complicated severe acute malnutrition

High mortality after discharge from hospital following acute illness has been observed among children with Severe Acute Malnutrition (SAM). However, mechanisms that may be amenable to intervention to reduce risk are unknown. We performed a nested case-control study among HIV-uninfected children aged 2-59 months treated for complicated SAM according to WHO recommendations at four Kenyan hospitals. Blood was drawn from 1778 children when clinically judged stable before discharge from hospital. Cases were children who died within 60 days. Controls were randomly selected children who survived for one year without readmission to hospital. Untargeted proteomics, total protein, cytokines and chemokines, and leptin were assayed in plasma and corresponding biological processes determined. Among 121 cases and 120 controls, increased levels of calprotectin, von Willebrand factor, angiotensinogen, IL8, IL15, IP10, TNF alpha, and decreased levels of leptin, heparin cofactor 2, and serum paraoxonase were associated with mortality after adjusting for possible confounders. Acute phase responses, cellular responses to lipopolysaccharide, neutrophil responses to bacteria, and endothelial responses were enriched among cases. Among apparently clinically stable children with SAM, a sepsis-like profile is associated with subsequent death. This may be due to ongoing bacterial infection, translocated bacterial products or deranged immune response during nutritional recovery

Cessation of exclusive breastfeeding and seasonality, but not small intestinal bacterial overgrowth, are associated with environmental enteric dysfunction: A birth cohort study amongst infants in rural Kenya.

Background: Environmental Enteric Dysfunction (EED) is a chronic intestinal inflammatory disorder of unclear aetiology prevalent amongst children in low-income settings and associated with stunting. We aimed to characterise development of EED and its putative risk factors amongst rural Kenyan infants. Methods: In a birth cohort study in Junju, rural coastal Kenya, between August 2015 and January 2017, 100 infants were each followed for nine months. Breastfeeding status was recorded weekly and anthropometry monthly. Acute illnesses and antibiotics were captured by active and passive surveillance. Intestinal function and small intestinal bacterial overgrowth (SIBO) were assessed by monthly urinary lactulose mannitol (LM) and breath hydrogen tests. Faecal alpha-1-antitrypsin, myeloperoxidase and neopterin were measured as EED biomarkers, and microbiota composition assessed by 16S sequencing. Findings: Twenty nine of the 88 participants (33%) that underwent length measurement at nine months of age were stunted (length-for-age Z score <-2). During the rainy season, linear growth was slower and LM ratio was higher. In multivariable models, LM ratio, myeloperoxidase and neopterin increased after cessation of continuous-since-birth exclusive breastfeeding. For LM ratio this only occurred during the rainy season. EED markers were not associated with antibiotics, acute illnesses, SIBO, or gut microbiota diversity. Microbiota diversified with age and was not strongly associated with complementary food introduction or linear growth impairment. Interpretation: Our data suggest that intensified promotion of uninterrupted exclusive breastfeeding amongst infants under six months during the rainy season, where rainfall is seasonal, may help prevent EED. Our findings also suggest that therapeutic strategies directed towards SIBO are unlikely to impact on EED in this setting. However, further development of non-invasive diagnostic methods for SIBO is required. Funding: This research was funded in part by the Wellcome Trust (Research Training Fellowship to RJC (103376/Z/13/Z)). EPKP was supported by the MRC/DfID Newton Fund (MR/N006259/1). JAB was supported by the MRC/DFiD/Wellcome Trust Joint Global Health Trials scheme (MR/M007367/1) and the Bill & Melinda Gates Foundation (OPP1131320). HHU was supported by the NIHR Oxford Biomedical Research Centre (IS-BRC-1215-20008)

The Plasma Concentration of the B Cell Activating Factor Is Increased in Children With Acute Malaria

Malaria-specific antibody responses in children often appear to be short-lived but the mechanisms underlying this phenomenon are not well understood. In this study, we investigated the relationship between the B-cell activating factor (BAFF) and its receptors expressed on B cells with antibody responses during and after acute malaria in children. Our results demonstrate that BAFF plasma levels increased during acute malarial disease and reflected disease severity. The expression profiles for BAFF receptors on B cells agreed with rapid activation and differentiation of a proportion of B cells to plasma cells. However, BAFF receptor (BAFF-R) expression was reduced on all peripheral blood B cells during acute infection, but those children with the highest level of BAFF-R expression on B cells maintained schizont-specific immunoglobin G (IgG) over a period of 4 months, indicating that dysregulation of BAFF-R expression on B cells may contribute to short-lived antibody responses to malarial antigens in children. In summary, this study suggests a potential role for BAFF during malaria disease, both as a marker for disease severity and in shaping the differentiation pattern of antigen-specific B cells

Analysis of the immune evasion mechanisms of varicella zoster virus

Varicella zoster virus (VZV) is an alpha herpes virus that causes primary infection with varicella (chicken pox), establishes latency in ganglia and may later reactivate as herpes zoster (shingles). Innate immune effectors are thought to control initial viral replication, but it is the adaptive immune system, involving T cells that mediates eventual control of viraemia and the associated clinical disease. Although both CD4+ and CD8+ T cells mediate viral clearance during acute illness, memory responses are dominated by CD4+ T cells. We tested the hypothesis that the paucity in memory CD8+ T cell effectors is partly attributed to immune evasion mechanisms that are mounted by VZV. We confirmed that VZV readily down regulates cell surface HLA-A and HLA-C but spares HLA-B onVZV infected keratinocytes and VZV infected Mewo cells. Analysis of intracellular HLA protein expression and gene transcription showed global down regulation of all HLA subtypes. Further analysis showed that VZV inhibits IFN-γ mediated up regulation of HLA expression and augments IFN-γ mediated up regulation of HLA-E and CD71 expression. Furthermore, we show that acute VZV infection lowers the frequency of circulating peripheral blood myeloid dendritic cells (mDC), reduces the expression of the DC activation marker HLA-DR and impairs inflammatory cytokine secretion in blood DC populations. Inhibition of DC cytokine secretion was found to be dependent on viral replication as irradiated virus resulted only in mild inhibition of IFN-α and TNF-α secretion. Lastly, we observed that VZV infection results in increased expression of host peptides, including MHC derived leader sequences that potentially bind to HLA-E. Cell surface HLA-E is known to be a ligand for the natural killer (NK) cell inhibitory receptor CD94/ NKG2A identifying a novel mechanism of viral immune escape from NK cell surveillance. In conclusion, our data reiterates the fact that VZV targets different aspects of antigen presentation to evade the immune system with implications for pathogenesis and approaches to improved vaccination and treatment.</p

Analysis of the immune evasion mechanisms of varicella zoster virus

Varicella zoster virus (VZV) is an alpha herpes virus that causes primary infection with varicella (chicken pox), establishes latency in ganglia and may later reactivate as herpes zoster (shingles). Innate immune effectors are thought to control initial viral replication, but it is the adaptive immune system, involving T cells that mediates eventual control of viraemia and the associated clinical disease. Although both CD4+ and CD8+ T cells mediate viral clearance during acute illness, memory responses are dominated by CD4+ T cells. We tested the hypothesis that the paucity in memory CD8+ T cell effectors is partly attributed to immune evasion mechanisms that are mounted by VZV. We confirmed that VZV readily down regulates cell surface HLA-A and HLA-C but spares HLA-B onVZV infected keratinocytes and VZV infected Mewo cells. Analysis of intracellular HLA protein expression and gene transcription showed global down regulation of all HLA subtypes. Further analysis showed that VZV inhibits IFN-γ mediated up regulation of HLA expression and augments IFN-γ mediated up regulation of HLA-E and CD71 expression. Furthermore, we show that acute VZV infection lowers the frequency of circulating peripheral blood myeloid dendritic cells (mDC), reduces the expression of the DC activation marker HLA-DR and impairs inflammatory cytokine secretion in blood DC populations. Inhibition of DC cytokine secretion was found to be dependent on viral replication as irradiated virus resulted only in mild inhibition of IFN-α and TNF-α secretion. Lastly, we observed that VZV infection results in increased expression of host peptides, including MHC derived leader sequences that potentially bind to HLA-E. Cell surface HLA-E is known to be a ligand for the natural killer (NK) cell inhibitory receptor CD94/ NKG2A identifying a novel mechanism of viral immune escape from NK cell surveillance. In conclusion, our data reiterates the fact that VZV targets different aspects of antigen presentation to evade the immune system with implications for pathogenesis and approaches to improved vaccination and treatment.This thesis is not currently available on ORA

A metabolic perspective of the neutrophil life cycle:new avenues in immunometabolism

Neutrophils are the most abundant innate immune cells. Multiple mechanisms allow them to engage a wide range of metabolic pathways for biosynthesis and bioenergetics for mediating biological processes such as development in the bone marrow and antimicrobial activity such as ROS production and NET formation, inflammation and tissue repair. We first discuss recent work on neutrophil development and functions and the metabolic processes to regulate granulopoiesis, neutrophil migration and trafficking as well as effector functions. We then discuss metabolic syndromes with impaired neutrophil functions that are influenced by genetic and environmental factors of nutrient availability and usage. Here, we particularly focus on the role of specific macronutrients, such as glucose, fatty acids, and protein, as well as micronutrients such as vitamin B3, in regulating neutrophil biology and how this regulation impacts host health. A special section of this review primarily discusses that the ways nutrient deficiencies could impact neutrophil biology and increase infection susceptibility. We emphasize biochemical approaches to explore neutrophil metabolism in relation to development and functions. Lastly, we discuss opportunities and challenges to neutrophil-centered therapeutic approaches in immune-driven diseases and highlight unanswered questions to guide future discoveries.</p