Sphingolipid signalling and liver diseases.

Sphingolipids (SLs) comprise a class of lipids with important structural functions and increasing relevance in cellular signalling. In particular, ceramide has attracted considerable attention owing to its role as a second messenger modulating several cell functions such as proliferation, gene expression, differentiation, cell cycle arrest and cell death. Increasing evidence documents the role of SLs in stress and death ligand-induced hepatocellular death, which contributes to the progression of several liver diseases including steatohepatitis, ischaemia-reperfusion liver injury or hepatocarcinogenesis. Furthermore, recent data indicate that the accumulation of SLs in specific cell subcompartments, characteristic of many sphingolipidoses, contributes to the hepatic dysfunctions that accompany these inherited diseases. Hence, the regulation of the cell biology and metabolism of SLs may open up a novel therapeutic avenue in the treatment of liver diseases.     

Composition of the HLA‐DR‐associated human thymus peptidome

Major histocompatibility complex class II (MHC‐II) molecules bind to and display antigenic peptides on the surface of antigen‐presenting cells (APCs). In the absence of infection, MHC‐II molecules on APCs present self‐peptides and interact with CD4⁺ T cells to maintain tolerance and homeostasis. In the thymus, self‐peptides bind to MHC‐II molecules expressed by defined populations of APCs specialised for the different steps of T‐cell selection. Cortical epithelial cells present peptides for positive selection, whereas medullary epithelial cells and dendritic cells are responsible for peptide presentation for negative selection. However, few data are available on the peptides presented by MHC molecules in the thymus. Here, we apply mass spectrometry to analyse and identify MHC‐II‐associated peptides from five fresh human thymus samples. The data show a diverse self‐peptide repertoire, mostly consisting of predicted MHC‐II high binders. Despite technical limitations preventing single cell population analyses of peptides, these data constitute the first direct assessment of the HLA‐II‐bound peptidome and provide insight into how this peptidome is generated and how it drives T‐cell repertoire formation.     

FBXO28 causes developmental and epileptic encephalopathy with profound intellectual disability

Chromosome 1q41‐q42 deletion syndrome is a rare cause of intellectual disability, seizures, dysmorphology, and multiple anomalies. Two genes in the 1q41‐q42 microdeletion, WDR26 and FBXO28, have been implicated in monogenic disease. Patients with WDR26 encephalopathy overlap clinically with those with 1q41‐q42 deletion syndrome, whereas only one patient with FBXO28 encephalopathy has been described. Seizures are a prominent feature of 1q41‐q42 deletion syndrome; therefore, we hypothesized that pathogenic FBXO28 variants cause developmental and epileptic encephalopathies (DEEs). We describe nine new patients with FBXO28 pathogenic variants (four missense, including one recurrent, three nonsense, and one frameshift) and analyze all 10 known cases to delineate the phenotypic spectrum. All patients had epilepsy and 9 of 10 had DEE, including infantile spasms (3) and a progressive myoclonic epilepsy (1). Median age at seizure onset was 22.5 months (range 8 months to 5 years). Nine of 10 patients had intellectual disability, which was profound in six of nine and severe in three of nine. Movement disorders occurred in eight of 10 patients, six of 10 had hypotonia, four of 10 had acquired microcephaly, and five of 10 had dysmorphic features, albeit different to those typically seen in 1q41‐q42 deletion syndrome and WDR26 encephalopathy. We distinguish FBXO28 encephalopathy from both of these disorders with more severe intellectual impairment, drug‐resistant epilepsy, and hyperkinetic movement disorders.     

The diagnosis and management of allergic reactions in patients sensitized to non-specific lipid transfer proteins

Sensitization to one or more non-specific lipid transfer proteins (nsLTPs), initially thought to exist mainly in southern Europe, is becoming accepted as a cause of allergic reactions to plant foods across Europe and beyond. The peach nsLTP allergen Pru p 3 is a dominant sensitizing allergen and peaches a common food trigger, although multiple foods can be involved. A frequent feature of reactions is the requirement for a cofactor (exercise, alcohol, non-steroidal anti-inflammatory drugs, Cannabis sativa) to be present for a food to elicit a reaction. The variability in the food and cofactor triggers makes it essential to include an allergy-focused diet and clinical history in the diagnostic workup. Testing on suspected food triggers should also establish whether sensitization to nsLTP is present, using purified or recombinant nsLTP allergens such as Pru p 3. The avoidance of known trigger foods and advice on cofactors is currently the main management for this condition. Studies on immunotherapy are promising, but it is unknown whether such treatments will be useful in populations where Pru p 3 is not the primary sensitizing allergen. Future research should focus on the mechanisms of cofactors, improving diagnostic accuracy and establishing the efficacy of immunotherapy.     

Emerging insights into the role of albumin with plasma exchange in Alzheimer’s disease management

Alzheimer’s disease (AD) is a neurodegenerative process that inexorably leads to progressive deterioration of cognition function and, ultimately, death. Central pathophysiologic features of AD include the accumulation of extracellular plaques comprised of amyloid-β peptide (Aβ) and the presence of intraneuronal neurofibrillary tangles. However, a large body of evidence suggests that oxidative stress and inflammation are major contributors to the pathogenesis and progression of AD. To date, available pharmacologic treatments are only symptomatic. Clinical trials focused on amyloid and non-amyloid-targeted treatments with small molecule pharmacotherapy and immunotherapies have accumulated a long list of failures. Considering that around 90 % of the circulating Aβ is bound to albumin, and that a dynamic equilibrium exists between peripheral and central Aβ, plasma exchange with albumin replacement has emerged as a new approach in a multitargeted AD therapeutic strategy (AMBAR Program). In plasma exchange, a patient’s plasma is removed by plasmapheresis to eliminate toxic endogenous substances, including Aβ and functionally impaired albumin. The fluid replacement used is therapeutic albumin, which acts not only as a plasma volume expander but also has numerous pleiotropic functions (e.g., circulating Aβ- binding capacity, transporter, detoxifier, antioxidant) that are clinically relevant for the treatment of AD. Positive results from the AMBAR Program (phase 1, 2, an 2b/3 trials), i.e., slower decline or stabilization of disease symptoms in the most relevant clinical efficacy and safety endpoints, offer a glimmer of hope to both AD patients and caregivers.     

Allogeneic transplantation of CD34(+) selected cells from peripheral blood from human leukocyte antigen-identical siblings: detrimental effect of a high number of donor CD34(+) cells?

Clinical results after T-cell-depleted allografts might be improved by modifying the graft content of progenitor and accessory cells. Although the association of the number of donor T cells with the clinical outcome has been studied extensively, the optimum number of progenitor cells that should be administered to patients is unknown. The characteristics of 84 consecutive human leukocyte antigen (HLA)-identical sibling transplants of granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood progenitor cells depleted of T cells by CD34(+) positive selection (allo-PBT/CD34(+)) were analyzed for their effect on clinical outcome. After a median follow-up of 24 months (range, 1-70 months), 50 patients remain alive (59.5%) and 34 have died (21 [25%] as a result of the transplant and 13 [15.5%] due to disease relapse). The median number of CD34(+) cells administered to the patients was 3.9 x 10(6)/kg (range, 1.2-14.3 x 10(6)/kg). A number of CD34(+) cells in the inoculum of 1 x 10(6)/kg to 3 x 10(6)/kg was associated with increased survival: 21 of 28 (75%) patients are alive, as compared with 29 of 56 (52%) patients receiving more than 3 x 10(6)/kg (actuarial probability 75% vs. 42%, respectively; P =.01). In the multivariate analysis, the independent prognostic variables for survival were CD34(+) cell dose 1 x 10(6)/kg to 3 x 10(6)/kg (RR = 4.8; P =.0008), sex-pairing match (RR = 3.2; P =.002), and early stage of disease (RR = 2.8; P =.007). From these results it appears that, in allo-PBT/CD34(+) from HLA-identical siblings, a number of CD34(+) cells in the inoculum between 1 x 10(6)/kg to 3 x 10(6)/kg is an important factor for better survival, and that higher CD34(+) cell doses might be associated with a poorer outcome.     

Diffuse large B-cell lymphoma arising from donor lymphoid cells after renal and pancreatic transplantation

A patient with both a renal and pancreatic transplantation developed a diffuse large B-cell lymphoma, Epstein-Barr virus-related, 14 months after the surgical procedure. Tumor was confined to the transplanted organs: head of the pancreas and hilar lymph node of the transplanted kidney. Chimerism analysis demonstrated the tumor origin from donor lymphoid cells. Immunosuppression was discontinued and chemotherapy with cyclophosphamide, hydroxydaunomycin, vincristine, and prednisone (CHOP) was started. However, no response was observed after three courses of this regimen. Finally, a transplantectomy was carried out, followed by rituximab (anti-CD20 antibody), with the patient achieving a complete response (CR). Two years later the patient remains in CR.