Anti-microbial sero-reactivity (AMS) and chronic intestinal inflammation similar to Crohn's Disease (CD) during the first decade of life in children with inherited disorders of phagocyte function suggests that loss-of-function in neutrophil antimicrobial pathways is likely to be a fundamental mechanism of pediatric CD pathogenesis. GWAS in CD have accounted for only a portion of the heritability and have rarely identified few loci of large effect. Rare variants, which GWAS are underpowered to detect, have been hypothesized to explain a substantial fraction of complex disorders like CD, so gene discovery efforts have now shifted to characterization of deleterious / loss of function mutations. Granulocyte-Macrophage Colony Stimulating Factor (GM-CSF) is required for priming of neutrophil antimicrobial function, and bioinformatic analysis of genomic studies has suggested a central role in CD pathogenesis. We discovered that older pediatric (early onset, EO, age 10-17) and adult patients exhibit an acquired basis for neutrophil dysfunction, GM-CSF auto-antibodies (GM-CSF Ab), which increase in titer with increasing age. GM-CSF Ab carriage is associated with reduced neutrophil STAT5 activation, phagocytic capacity, and bacterial killing, and high rates of AMS and stricturing behavior. To test the significance of these exciting developments, we have established a prospective clinical database and biobank for 1130 pediatric CD patients enrolled at diagnosis (the RISK study). We found that neutrophil phagocytosis and bacterial killing is reduced in a subset of patients. VEO patients have exhibited rare coding region mutations in genes predicted to affect GM-CSF priming of bacterial killing (CSF2RB &ITGAM/CD11b) and neutrophil oxidative burst (CYBA/p22phox), while EO patients have exhibited increasing titers of GM-CSF Ab. We hypothesize that genetic variants and GM-CSF Ab cause neutrophil dysfunction and thereby contribute to disease pathogenesis in an age-dependent manner in pediatric CD.
Aim 1 : Identify all coding genetic mutations in 127 genes likely to disrupt GM-CSF signaling and/or neutrophil function in 500 very early onset pediatric CD patients.
Aim 2 : Test the functional consequences of genetic mutations upon neutrophil GM-CSF signaling and bacterial killing. Peripheral blood samples will be collected from RISK patients carrying genetic mutations predicted to affect GM-CSF priming and neutrophil function including neutrophil candidate protein expression/localization, GM- CSF signaling, CD64 activation, adhesion, chemotaxis, oxidative burst, phagocytosis, and bacterial killing. We will use state-of-the-art genomic and immune approaches to define for the first time the causes and consequences of neutrophil dysfunction in the largest pediatric CD inception cohort in North America. Collectively, our studies will have direct implications for novel therapeutic approaches designed to modulate this critical host defense pathway in patients who experience the worst outcomes with current approaches.

Public Health Relevance

We will use state-of-the-art genomic and immune approaches to define for the first time the causes and consequences of neutrophil dysfunction in the largest pediatric CD inception cohort in North America. We will identify novel genetic variants using exome sequencing in VEO patients, and establish the precise role of a novel pathogenic mechanism involving GM-CSF antibodies. Collectively, our studies will have direct implications for novel therapeutic approaches designed to modulate this critical host defense pathway in this group of very early onset understudied patient population who experience the worst outcomes with current approaches.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
1R01DK098231-01A1
Application #
8632332
Study Section
Special Emphasis Panel (ZDK1-GRB-6 (O2))
Program Officer
Hamilton, Frank A
Project Start
2013-09-17
Project End
2018-07-31
Budget Start
2013-09-17
Budget End
2014-07-31
Support Year
1
Fiscal Year
2013
Total Cost
$689,907
Indirect Cost
$208,058
Name
Emory University
Department
Pediatrics
Type
Schools of Medicine
DUNS #
066469933
City
Atlanta
State
GA
Country
United States
Zip Code
30322
Kelly, Daniel; Kotliar, Michael; Woo, Vivienne et al. (2018) Microbiota-sensitive epigenetic signature predicts inflammation in Crohn's disease. JCI Insight 3:
Shaw, Kelly A; Cutler, David J; Okou, David et al. (2018) Genetic variants and pathways implicated in a pediatric inflammatory bowel disease cohort. Genes Immun :
Gathungu, Grace; Zhang, Yuanhao; Tian, Xinyu et al. (2018) Impaired granulocyte-macrophage colony-stimulating factor bioactivity accelerates surgical recurrence in ileal Crohn's disease. World J Gastroenterol 24:623-630
Wright, Sandra S; Trauernicht, Anna; Bonkowski, Erin et al. (2018) Familial Association of Granulocyte-Macrophage Colony-Stimulating Factor Autoantibodies in Inflammatory Bowel Disease. J Pediatr Gastroenterol Nutr 66:767-772
Schwerd, T; Bryant, R V; Pandey, S et al. (2018) NOX1 loss-of-function genetic variants in patients with inflammatory bowel disease. Mucosal Immunol 11:562-574
Denson, Lee A; Jurickova, Ingrid; Karns, Rebekah et al. (2018) Clinical and Genomic Correlates of Neutrophil Reactive Oxygen Species Production in Pediatric Patients With Crohn's Disease. Gastroenterology 154:2097-2110
Shaw, Kelly A; Bertha, Madeline; Hofmekler, Tatyana et al. (2016) Dysbiosis, inflammation, and response to treatment: a longitudinal study of pediatric subjects with newly diagnosed inflammatory bowel disease. Genome Med 8:75
Go, Alan S (2016) Cardiovascular Disease Consequences of CKD. Semin Nephrol 36:293-304
Okou, David T; Kugathasan, Subra (2014) Role of genetics in pediatric inflammatory bowel disease. Inflamm Bowel Dis 20:1878-84