Disruption of MyD88 signaling suppresses hemophagocytic lymphohistiocytosis in mice

Abstract

IntroductionHemophagocytic lymphohistiocytosis (HLH) is a rare disorder of the immune system. The familial form (FHL) arises in children and is caused by mutations that impair the cytotoxic activity of NK cells and CD8 ϩ T cells. The second form, sporadic HLH, may arise in individuals with pathogen infections or with autoimmune diseases or malignancies. 1 Both HLH variants are believed to be initiated by viral infections. 2 These pathogenic triggers have remained elusive, although Epstein-Barr virus has been proposed as one cause. [3][4] After symptomatic onset of HLH, survival declines rapidly despite chemotherapy with cytotoxic and immunosuppressive drugs. 5 To date, hematopoietic stem cell transplantation is the best long-term therapy for familial HLH.We previously described an N-ethyl-N-nitrosourea (ENU)-germ line mutant called jinx in which a mutation in Unc13d prevents the release of cytolytic granules by NK cells and CD8 ϩ T cells. 6 We demonstrated that clinical features of the HLH-like syndrome observed in humans are recapitulated in Unc13d jinx/jinx mice infected with lymphochoriomeningitis virus (LCMV). Unc13d jinx/jinx remains the only animal model of human type 3 FHL, which is caused by mutations in MUNC13-4, the human ortholog of Unc13d.On infection of Unc13d jinx/jinx mutants, a positive feedback loop is initiated between CD8 ϩ T cells and antigen-presenting cells (APCs) such as macrophages, leading to their overactivation and HLH-like symptoms. 6 We hypothesized that interrupting this positive feedback loop could ameliorate the onset and/or extent of HLH-like disease and potentially reveal novel therapeutic targets for human HLH. We therefore examined the impact of disrupting cell adhesion molecules, effector cytokines, and innate immune sensors on the progression of HLH-like disease in Unc13d jinx/jinx mutants, and identified myeloid differentiation primary response gene 88 (MyD88) as a key protein required for the development of the syndrome. Methods MiceAll mouse studies were performed in accordance with institutional regulations governing animal care and use. C57BL/6J mice were bred locally at The Scripps Research Institute. The following mutants have been previously reported and are described at http://mutagenetix.scripps.edu: For personal use only. on May 10, 2018. by guest www.bloodjournal.org From Complete blood counts and serum cytokine detectionBlood samples were taken from the retro-orbital plexus of mice and analyzed using a Hemavet 950 veterinary hematology system (Fisher Scientific). Alternatively, IFN␥ or TNF were assayed in the serum by ELISA (eBioscience). Viruses, focus-forming unit assayThe Armstrong strain of LCMV was injected intravenously at a dose of 2 ϫ 10 5 plaque-forming units per mouse. Viral titers were determined after organ homogenization by standard plaque assays on VERO cells. Antibodies and intracellular cytokine stainingThe following antibodies were used for flow cytometry, to stain splenocytes: CD11b (M1/70), CD3⑀ (145-2C11), CD8␣ (53-6.7), CD80 (B7-1), CD86 (GL...

Polygenic mutations in the cytotoxicity pathway increase susceptibility to develop HLH immunopathology in mice

“…It is noteworthy that genetic defects in IL-10 and Myd88 were shown to promote disease development in murine models of HLH. 42,43 Such features have not yet been analyzed in humans. The presence of activating mutations in the nucleotide-binding domain of the inflammasome component NLRC4 was recently found to be associated with recurrent HLH in several patients.…”

Macrophage activation syndrome as part of systemic juvenile idiopathic arthritis: diagnosis, genetics, pathophysiology and treatment

“…Interestingly, some of these ideas may apply to primary HLH as well, as a recent report shows the critical need for the TLR signaling adaptor MyD88 in the development of disease in lymphochoriomeningitic virus-infected MUNC13-4-deficient mice. 60 The immunological mechanisms behind other animal models of HLH/MAS are less well defined. Infection of rabbits with Herpesvirus papio results in a clinical syndrome similar to EBV-HLH.…”

Mutation of the ER retention receptor KDELR1 leads to cell-intrinsic lymphopenia and a failure to control chronic viral infection

“…at 2 × 10 5 PFU per mouse. Mice were killed 12 d later, and splenocytes stimulated for 5 h with 10 −7 M LCMV GP33 (KAVYNFATM) peptide as described previously (34). Stimulated cells were then stained for CD3e and CD8α, fixed, permeabilized, and stained with antibodies against IFN-γ (XMG1.2) or TNF-α (MP6-XT22).…”