Targeting the Splicing of mRNA in Autoimmune Diseases: BAFF Inhibition in Sjögren's Syndrome as a Proof of Concept

BAFF (B-cell–activating factor of the tumor necrosis factor family), a pivotal cytokine for B-cell activation, is overexpressed by salivary gland (SG) epithelial cells in primary Sjogren''s syndrome (pSS). ΔBAFF, a physiological inhibitor of BAFF, is a minor alternative splice variant of BAFF. A U7 RNA was reengineered to deliver antisense sequences targeting BAFF splice regions. A major decrease of BAFF messenger RNA (mRNA) and protein secretion, concomitantly with the increase of ΔBAFF mRNA, was observed in vitro. In vivo, SG retrograd instillation of nonobese diabetic mice by the modified U7 cloned into an adeno-associated virus vector significantly decreased BAFF protein expression and lymphocytic infiltrates and improved salivary flow. This study offers a rationale for localized therapeutic BAFF inhibition in pSS and represents a proof of concept of the interest of exon skipping in autoimmune diseases.     

Absence or low expression of fas-associated protein with death domain in acute myeloid leukemia cells predicts resistance to chemotherapy and poor outcome

In acute myeloid leukemia (AML), coexpression of death receptors and ligands of the tumor necrosis factor (TNF) receptor/TNF-alpha superfamily on leukemic cells after chemotherapy is not always accompanied by apoptosis, suggesting that the apoptotic death receptor signaling pathway is disrupted. Because Fas-associated protein with death domain (FADD) is the main adaptor for transmitting the Fas, TNF-related apoptosis-inducing ligand receptors, and TNF receptor 1 death signal, expression of FADD was analyzed by Western blot and immunocytochemistry in leukemic cells of 70 de novo AML patients treated with the European Organization of Research and Treatment of Cancer AML-10 randomized trial before initiation of induction chemotherapy. Thirty seven percent of patients (17 of 46) with FADD negative/low (FADD(-/low)) leukemic cells had a primary refractory disease compared with 12% of FADD(+) patients (3 of 24; P = 0.05). FADD(-/low) expression was significantly associated with a worse event-free survival [EFS (P = 0.04)] and overall survival (P = 0.04). In multivariate analysis, FADD(-/low) protein expression was independently associated with a poor EFS and overall survival (P = 0.002 and P = 0.026, respectively). Importantly, FADD(-/low) protein expression predicted poor EFS even in patients with standard- or good-risk AML (P = 0.009). Thus, we identified low or absent expression of the FADD protein in leukemic cells at diagnosis as a poor independent prognostic factor that can predict worse clinical outcome even for patients with standard- or good-risk AML.     

Arthritogenicity of minor cartilage collagens (types IX and XI) in mice

Native type II collagen, the major cartilage collagen, is immunogenic and arthritogenic in rodents. To investigate whether minor cartilage collagens are arthritogenic, we immunized DBA/1 mice with the pepsin-soluble fractions of type IX or type XI collagen emulsified in Freund's complete adjuvant. Both collagens were arthritogenic in DBA/1 mice after only 1 injection. However, the incidence of the polyarthritis was lower and the severity was lesser than with that induced by bovine type II collagen, even when a booster injection was administered. All mice developed a humoral response to the immunizing antigen, without any relationship to the arthritic status. Interestingly, competition experiments showed that antibodies raised against type XI collagen also bound with high avidity to type II collagen. In contrast, sera from type IX collagen-immunized mice did not react with either type II or type XI collagen. We conclude that types IX and XI minor cartilage collagens are both arthritogenic and immunogenic in DBA/1 mice. Whether the recognition of epitopes common to different collagens is relevant to the articular pathology remains to be elucidated.