Role of DOCK8 in Hyper-inflammatory Syndromes

BackgroundCytokine storm syndromes (CSS), including hemophagocytic lymphohistiocytosis (HLH), are increasingly recognized as hyper-inflammatory states leading to multi-organ failure and death. Familial HLH (FHL) in infancy results from homozygous genetic defects in perforin-mediated cytolysis by CD8 T-lymphocytes and natural killer (NK) cells. Later onset CSS are frequently associated with heterozygous defects in FHL genes, but genetic etiologies for most are unknown. We identified rare DOCK8 variants in CSS patients. ObjectiveWe explore the role of CSS patient derived DOCK8 mutations on cytolytic activity in NK cells. We further study effects of Dock8-/- in murine models of CSS. MethodsDOCK8 cDNA from 2 unrelated CSS patients with different missense mutations were introduced into human NK-92 NK cells by foamy virus transduction. NK cell degranulation (CD107a), cytolytic activity against K562 target cells, and interferon-gamma (IFN{gamma}) production were explored by flow cytometry (FCM). A third CSS patient DOCK8 mRNA splice acceptor site variant was explored by exon trapping. Dock8-/- mice were assessed for features of CSS (weight loss, splenomegaly, hepatic inflammation, cytopenias, and IFN{gamma} levels) upon challenge with lymphochoriomeningitic virus (LCMV) and excess IL-18. ResultsBoth patient DOCK8 missense mutations decreased cytolytic function in NK cells in a partial dominant-negative fashion in vitro. The patient DOCK8 splice variant disrupted mRNA splicing in vitro. Dock8-/- mice tolerated excess IL-18 but developed features of CSS upon LCMV infection. ConclusionMutations in DOCK8 may contribute to CSS-like hyper-inflammatory states by altering cytolytic function in a threshold model of disease. Key MessagesO_LIHeterozygous missense mutations in DOCK8 may contribute to decreased NK cell function via partial dominant-negative effects on perforin-mediated cytolysis. C_LIO_LIHeterozygous mutations in DOCK8 may contribute to hyper-inflammatory syndromes in a threshold model of disease. C_LIO_LILCMV infection of Dock8-/- mice recapitulates features of murine FHL. C_LI Capsule SummaryHeterozygous missense and splice site mutations in DOCK8 may contribute to hyper-inflammation in patients with CSS. DOCK8 is important for optimal NK cell cytolytic function, and LCMV infection of Dock8-/- mice resembles murine FHL.