OC 28.2 - Pathway-based Rare Variant Burden Analysis Identifies a Role for the Complement System in Purpura Fulminans

Sunday, July 10, 2022

3:00 PM – 3:15 PM

Location: ExCel Center, ICC Capital Suite Room 17

Presentation Format: In-Person

Presenting Author(s)

PB

Pavan Bendapudi

Assistant Professor of Medicine
Beth Israel Deaconess Medical Center
Boston, Massachusetts, United States

Co-Author(s)

SN

Sumaiya Nazeen

Postdoctoral Fellow
Brigham and Women's Hospital
Boston, Massachusetts, United States
JR

Justine Ryu

Postdoctoral Fellow
Beth Israel Deaconess Medical Center
Boston, Massachusetts, United States
OS

Onuralp Soylemez

Postdoctoral Fellow
Brigham and Women's Hospital
Boston, Massachusetts, United States
BR

Betty Rouaisnel

Technician
Dana Farber Cancer Institute
Boston, Massachusetts, United States
MC

Meaghan Colling

Postdoctoral Fellow
Massachusetts General Hospital
Boston, Massachusetts, United States
BP

Bryce Pasko

Postdoctoral Fellow
Beth Israel Deaconess Medical Center
Boston, Massachusetts, United States
AR

Alissa Robbins

Postdoctoral Fellow
Dana Farber Cancer Institute
Boston, Massachusetts, United States
MB

Michael Bouzinier

Postdoctoral Fellow
Brigham and Women's Hospital
Boston, Massachusetts, United States
LT

Lindsay Tomczak

Technician
Beth Israel Deaconess Medical Center
Boston, Massachusetts, United States
LC

LIndsay Collier

Technician
Beth Israel Deaconess Medical Center
Boston, Massachusetts, United States
SR

Sanjay Ram

Professor of Medicine
University of Massachusetts
Worcester, Massachusetts, United States
AT

Agnes Toth-Petroczy

Postdoctoral Fellow
Brigham and Women's Hospital
Boston, Massachusetts, United States
EF

Elizabeth Fieg

Genetic Counselor
Brigham and Women's Hospital
Boston, Massachusetts, United States
WD

Walter Dzik

Associate Professor of Medicine
Massachusetts General Hospital
Boston, Massachusetts, United States
JH

James Hudspeth

Assistant Professor of Medicine
Boston Medical Center
Boston, Guatemala, United States
OP

Olga Pozdnyakova

Associate Professor of Pathology
Brigham and Women's Hospital
Boston, Guatemala, United States
RM

Richard Maas

Professor of Medicine
Brigham and Women's Hospital
Boston, Massachusetts, United States
SS

Shamil Sunyaev

Professor of Biomedical Informatics
Brigham and Women's Hospital
Boston, Massachusetts, United States
JL

Julie-Aurore Losman

Assistant Professor of Medicine
Dana Farber Cancer Institute
Boston, Massachusetts, United States

Background: Purpura fulminans (PF) is a rare subtype of sepsis-associated coagulopathy that disproportionately affects younger patients and is characterized by uncontrolled systemic thrombosis frequently resulting in end organ damage and death. The complement system is responsible for the initial inflammatory response to infection and has long been considered a key driver of inflammation in severe sepsis and PF.

Aims: We sought to determine whether rare coding variants in the complement system predispose patients to severe sepsis with coagulopathy.

Methods: We performed whole exome sequencing on the Boston PF Cohort (N=40). Using a novel rare variant trend test (RVTT), we pursued a pathway-based approach comparing the burden of putatively deleterious rare coding variants in the complement system in PF patients vs. unselected patients with sepsis (N=87). We subsequently cloned and functionally characterized several novel variants in the integrin complement receptors 3 and 4 (CR3/CR4).

Results: Using RVTT in an ancestry-stratified analysis, we found a significantly increased burden of rare, putatively deleterious coding variants (ΔP variants) in PF patients compared to unselected patients with sepsis (P=0.013) (Table). By contrast, no association was found when the RVTT was repeated with synonymous variants or predicted functionally neutral missense variants. Similarly, gene sets from neither the glycolysis pathway nor the coagulation system showed enrichment for ΔP variants in the PF cohort. We cloned and characterized the 11 unique ΔP variants identified in genes encoding subunits of CR3 and CR4 in the PF cohort. CR3 is typically associated with anti-inflammatory signaling, while CR4 promotes a pro-inflammatory state. We found that 7/7 (100%) of CR3 variants showed decreased activity, while 6/7 (85.7%) CR4 variants showed increased activity in a dual-luciferase reporter assay for NF-κB (Figure).

Conclusion(s): Our results suggest that rare inherited defects in the complement system predispose individuals to the maladaptive hyperinflammatory response of severe sepsis.