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The coat protein I (COPI) complex mediates retrograde trafficking from the Golgi to the endoplasmic reticulum (ER). Five siblings with persistent bacterial and viral infections and defective humoral and cellular immunity had a homozygous p.K652E mutation in the γ1 subunit of COPI (γ1-COP). The mutation disrupts COPI binding to the KDEL receptor and impairs the retrieval of KDEL-bearing chaperones from the Golgi to the ER. Homozygous Copg1(K652E) mice had increased ER stress in activated T and B cells, poor antibody responses, and normal numbers of T cells that proliferated normally, but underwent increased apoptosis upon activation. Exposure of the mutants to pet store mice caused weight loss, lymphopenia, and defective T cell proliferation that recapitulated the findings in the patients. The ER stress-relieving agent tauroursodeoxycholic acid corrected the immune defects of the mutants and reversed the phenotype they acquired following exposure to pet store mice. This study establishes the role of γ1-COP in the ER retrieval of KDEL-bearing chaperones and thereby the importance of ER homeostasis in adaptive immunity.

Mutations in MYD88 cause susceptibility to invasive bacterial infections through impaired signaling downstream of toll-like receptors (TLRs) and IL-1 receptors. We studied a patient presenting with neutropenia, delayed umbilical cord separation, BCG adenitis, and P. aeruginosa pneumonia. Next-generation DNA sequencing identified a novel homozygous truncation mutation in MYD88 that abolishes MyD88 expression. The patient’s dermal fibroblasts had severely impaired IL-6 production after stimulation with ligands for the MyD88-dependent receptors TLR2, TLR4 and IL-1R, while responses to ligands for the MyD88-independent receptors TLR3 and TNF-α were preserved. Notably, secretion of TNF-α, which is essential for BCG control, was also impaired after LPS stimulation. In this first report of BCG infection in MyD88 deficiency, data suggest that MyD88-dependent TNF-α production contributes to control of mycobacterial disease.

BACKGROUND: The tumor necrosis family factor receptor (TNFR) family member 4-1BB (CD137) is encoded by TNFRSF9 and expressed on activated T cells. 4-1BB provides a co-stimulatory signal that enhances CD8(+) T cell survival, cytotoxicity, and mitochondrial activity, thereby promoting immunity against viruses and tumors. The ligand for 4-1BB (4-1BBL) is expressed on antigen-presenting cells and Epstein-Barr virus (EBV) transformed B cells. OBJECTIVE: We investigated the genetic basis of recurrent sino-pulmonary infections, persistent EBV viremia, and EBV-induced lymphoproliferation in two unrelated patients. METHODS: Whole exome sequencing, immunoblotting, immunophenotyping, and in vitro assays of lymphocyte and mitochondrial function were performed. RESULTS: The two patients shared a homozygous G109S missense mutation in 4-1BB that abolished protein expression and ligand binding. The patients’ CD8(+) T cells had reduced proliferation, impaired expression of interferon-γ (IFN-γ) and perforin, and diminished cytotoxicity against allogeneic and HLA matched EBV-B cells. Mitochondrial biogenesis, membrane potential, and function were significantly reduced in the patients’ activated T cells. An inhibitory antibody against 4-1BB recapitulated the patients’ defective CD8(+) T cell activation and cytotoxicity against EBV-infected B cells in vitro. CONCLUSION: This novel immunodeficiency demonstrates the critical role of 4-1BB co-stimulation in host immunity against EBV infection.

WOS: 000470113200044, PubMed: 30822429, …, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland; "Angelo Nocivelli'' Foundation, Supported by the Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, and by the "Angelo Nocivelli'' Foundation.

Activated PI3Kδ syndrome (APDS) Type I results from gain-of-function mutations in PIK3CD, which encodes the p110δ subunit of PI3Kδ. Abnormal actin dynamics have been hypothesized to contribute to the lymphopenia associated with this disease but have not been studied in patients with APDS. We report a patient with APDS who had widespread necrotic skin lesions that were responsive specifically to immunosuppressive therapy. EBV-transformed lymphoblastoid cells (EBV-LCLs) from patients with APDS exhibit increased polymerized actin and increased apoptosis, suggesting a contribution of impaired actin dynamics to this disease.

This study reports a homozygous mutation in REL abrogating c-Rel protein expression in a patient with combined immunodeficiency characterized by susceptibility to Mycobacterium tuberculosis, Salmonella, Cryptosporidium, and cytomegalovirus.