A Novel ELANE Mutation Associated with Inflammatory Arthritis, Defective NETosis, and Recurrent Parvoviral Infection

Abstract

Objective

We describe a 38-year-old woman presenting with a history of inflammatory arthritis, rash and daily fevers. She was noted to have chronic parvoviral infection with persistently detectable viral titers and a novel mutation in the ELANE gene.

ELANE encodes neutrophil elastase, a neutrophil serine protease with important antimicrobial effects and is found as part of neutrophil extracellular trap (NET) complexes. Pathogenic ELANE mutations have been described in forms of hereditary neutropenia. However, our patient was never neutropenic. Because of the striking clinical scenario, we investigated this mutation functionally.

Methods

NET formation by neutrophils was assessed by scanning electron microscopy. Neutrophil activation and neutrophil elastase production were studied by flow cytometry and fluorescent substrate based functional assay, respectively. Multiplex assay was used to quantitate neutrophil inflammatory cytokine production. PYMOL software was used to generate three-dimensional models of mutant elastase.

Results

The patient’s activated neutrophils demonstrated significantly decreased ability to form NETs by scanning electron microscopy, as well as quantitative defects in neutrophil activation and neutrophil elastase activity. The patient’s neutrophils demonstrated altered levels of IL-12 and IL-8 - key cytokines for antiviral immunity and neutrophil chemotaxis. Three-dimensional mapping revealed that the mutation could alter protein folding and surface charge distribution, potentially perturbing protein trafficking. Thus, the mutation could impact neutrophil function by decreasing NETosis, and altering key antiviral activities of neutrophils.

Conclusions

This is the first report of a human pathogenic ELANE mutation associated with a defect in NET-osis and a distinct syndrome of recurrent viral infection and chronic inflammation.