LUBAC: a new player in polyglucosan body disease

Altered protein ubiquitination is associated with the pathobiology of numerous diseases; however, its involvement in glycogen metabolism and associated polyglucosan body (PB) disease has not been investigated in depth. In PB disease, excessively long and less branched glycogen chains (polyglucosan bodies, PBs) are formed, which precipitate in different tissues causing myopathy, cardiomyopathy and/or neurodegeneration. Linear ubiquitin chain assembly complex (LUBAC) is a multi-protein complex composed of two E3 ubiquitin ligases HOIL-1L and HOIP and an adaptor protein SHARPIN. Together they are responsible for M1-linked ubiquitination of substrates primarily related to immune signaling and cell death pathways. Consequently, severe immunodeficiency is a hallmark of many LUBAC deficient patients. Remarkably, all HOIL-1L deficient patients exhibit accumulation of PBs in different organs especially skeletal and cardiac muscle resulting in myopathy and cardiomyopathy with heart failure. This emphasizes LUBAC's important role in glycogen metabolism. To date, neither a glycogen metabolism-related LUBAC substrate nor the molecular mechanism are known. Hence, current reviews on LUBAC's involvement in glycogen metabolism are lacking. Here, we aim to fill this gap by describing LUBAC's involvement in PB disease. We present a comprehensive review of LUBAC structure, its role in M1-linked and other types of atypical ubiquitination, PB pathology in human patients and findings in new mouse models to study the disease. We conclude the review with recent drug developments and near-future gene-based therapeutic approaches to treat LUBAC related PB disease.

A Case Report of HIV-Related Bilateral Inflammatory Myofibroblastic Tumors of Adrenal Gland

Inflammatory myofibroblastic tumor (IMT) is a rare disease which mostly occurs at younger age and locates in lung in general population. We report a rare case of 44-year-old man diagnosed adrenal IMT with HIV infection, who refused regular highly active antiretroviral therapy (HAART) 13 years ago until in hospital because of findings of adrenal masses. The patient underwent CT-guided needle biopsy successfully, and the pathological analysis documented the diagnosis of IMT by the feature of proliferation of fibroblastic-myofibroblastic with inflammatory infiltration. We failed to perform tumor complete resection due to diffuse invasion of tumor under laparoscope. The patient was complicated with severely multiple pulmonary infection post to surgery because of immunodeficiency, that eventually caused the death of patient 2 months later. This case reminds us that IMTs may be too aggressive and progressed in HIV-positive patients with irregular HAART to perform surgical resections, and severe immunodeficiency can be more fatal. To our knowledge, this case is the second IMT patient with HIV infection worldwide, but the first case occurs at adrenal gland rather than lung in adult.

Structural basis for isoform-specific inhibition of human CTPS1

Cytidine triphosphate synthase 1 (CTPS1) is necessary for an effective immune response, as revealed by severe immunodeficiency in CTPS1-deficient individuals [E. Martin et al.], [Nature] [510], [288–292] ([2014]). CTPS1 expression is up-regulated in activated lymphocytes to expand CTP pools [E. Martin et al.], [Nature] [510], [288–292] ([2014]), satisfying increased demand for nucleic acid and lipid synthesis [L. D. Fairbanks, M. Bofill, K. Ruckemann, H. A. Simmonds], [J. Biol. Chem. ] [270], [29682–29689] ([1995]). Demand for CTP in other tissues is met by the CTPS2 isoform and nucleoside salvage pathways [E. Martin et al.], [Nature] [510], [288–292] ([2014]). Selective inhibition of the proliferative CTPS1 isoform is therefore desirable in the treatment of immune disorders and lymphocyte cancers, but little is known about differences in regulation of the isoforms or mechanisms of known inhibitors. We show that CTP regulates both isoforms by binding in two sites that clash with substrates. CTPS1 is less sensitive to CTP feedback inhibition, consistent with its role in increasing CTP levels in proliferation. We also characterize recently reported small-molecule inhibitors, both CTPS1 selective and nonselective. Cryo-electron microscopy (cryo-EM) structures reveal these inhibitors mimic CTP binding in one inhibitory site, where a single amino acid substitution explains selectivity for CTPS1. The inhibitors bind to CTPS assembled into large-scale filaments, which for CTPS1 normally represents a hyperactive form of the enzyme [E. M. Lynch et al.], [Nat. Struct. Mol. Biol.] [24], [507–514] ([2017]). This highlights the utility of cryo-EM in drug discovery, particularly for cases in which targets form large multimeric assemblies not amenable to structure determination by other techniques. Both inhibitors also inhibit the proliferation of human primary T cells. The mechanisms of selective inhibition of CTPS1 lay the foundation for the design of immunosuppressive therapies.

EROS-mediated control of NOX2 and P2X7 biosynthesis

EROS (Essential for Reactive Oxygen Species) protein is indispensable for expression of the gp91phox-p22phox heterodimer of the phagocyte NADPH oxidase. EROS deficiency in humans causes the severe immunodeficiency, chronic granulomatous disease (CGD), but its mechanism of action remains unknown. We elucidate the role of EROS, showing it acts at the earliest stages of gp91phox maturation. It binds the immature 58kDa gp91phox directly, interacting with the OST glycosylation machinery and prevents gp91phox degradation. EROS also regulates the purine receptors P2X7 and P2X1 through direct interactions and P2X7 is almost absent in EROS deficiency. Accordingly, lack of EROS results in markedly abnormal P2X7 signalling, inflammasome activation and T cell responses. The loss of both ROS and P2X7 signalling leads to resistance to influenza infection. Our work identifies EROS as a highly selective chaperone for key proteins in innate and adaptive immunity and a rheostat for immunity to infection. It has profound implications for our understanding of immune physiology, immunodeficiency and gene therapy.

Disrupted Ca2+ homeostasis and immunodeficiency in patients with functional Inositol 1,4,5-trisphosphate receptor subtype 3 defects

Calcium signaling is essential for lymphocyte activation, with genetic disruptions resulting in severe immunodeficiency. The inositol 1,4,5-trisphosphate receptor (IP3R), formed from homo- or hetero-tetramers of the IP3R isoforms 1-3, amplifies lymphocyte signaling by releasing Ca2+ from ER stores into the cytosol following antigen-stimulation. While knockout of all 3 IP3R isoforms results in immunodeficiency in mice, the seeming redundancy of subunits was thought to explain the absence of IP3R mutation as a cause of human immunodeficiency. Here, we identify compound heterozygous variants in ITPR3 in two unrelated Caucasian patients presenting with combined immunodeficiency, in one case requiring hematopoietic stem cell transplantation. We observed disrupted Calcium homeostasis in patient-derived fibroblasts and immune cells, with abnormal proliferation and activation responses following B and T cell receptor stimulation. Reconstitution of IP3R knockout cell lines identified the variants as functional hypomorphs with reduced discrimination between homeostatic and induced states, validating a link between genotype and phenotype. These results demonstrate a functional linkage between defective ER Ca2+ channels and immunodeficiency, and identify IP3Rs as diagnostic targets for patients with specific inborn errors of immunity.

Modern possibilities of diagnostics of tuberculosis in patients with HIV infection

The problem of the steady growth of HIV-associated tuberculosis has become increasingly urgent in recent years in Russia. Diagnosis of tuberculosis is particularly difficult at the stage of severe immunodeficiency. Objective. to evaluate the effectiveness of the T-SPOT ® method.TB in the diagnosis of tuberculosis infection in patients with HIV infection. Materials and methods. in the period for 2019-2020, the T-SPOT®.TB results were analyzed in 396 patients. The criteria for inclusion in this study were the age of 18 years and older, the diagnosis of HIV infection, follow-up at the AIDS center. Results. in the group with a positive T-SPOT®.TB and changes on the computed tomogram, the verified diagnosis of tuberculosis was 90.7% of the group with both signs and 75.5% of those with a positive result T-SPOT®.TB. The group with a positive result T-SPOT®.TB and no changes on the CT scan is 16.8% of those with a positive result T-SPOT®.TB,such patients were diagnosed with „latent tuberculosis infection”. Conclusion. T-SPOT®.TB can be used in the diagnostic complex of monitoring patients with HIV infections — as a screening method that allows not only to verify the diagnosis, but also to detect latent tuberculosis.

Access to palivizumab among children at high risk of respiratory syncytial virus complications in English hospitals

ObjectivesPalivizumab is a monoclonal antibody which can prevent infection with respiratory syncytial virus (RSV). Due to its high cost, it is recommended for high-risk infants only. We aimed to determine the proportion of infants eligible for palivizumab treatment in England who receive at least one dose.MethodsWe used the Hospital Treatment Insights database containing hospital admission records linked to hospital pharmacy dispensing data for 43/153 hospitals in England. Infants born between 2010 and 2016 were considered eligible for palivizumab if their medical records indicated chronic lung disease (CLD), congenital heart disease (CHD), or severe immunodeficiency (SCID), and they met additional criteria based on gestational age at birth and age at start of the RSV season (beginning of October). We calculated the proportion of infants who received at least one dose of palivizumab in their first RSV season, and modelled the odds of treatment according to multiple child characteristics using logistic regression models.ResultsWe identified 3,712 eligible children, of whom 2,479 (67%) had complete information on all risk factors. Palivizumab was prescribed to 832 of eligible children (34%). Being born at <30 weeks’ gestation, aged <6 months at the start of RSV season, and having two or more of CLD, CHD or SCID were associated with higher odds of treatment.ConclusionIn England, palivizumab is not prescribed to the majority of children who are eligible to receive it. Doctors managing these infants might be unfamiliar with the eligibility criteria or are constrained by other considerations, such as cost.

Neutropenia in Primary Immunodeficiency Diseases

Phagocytes including neutrophil granulocytes and macrophages are important cells of the innate immune system whose primary function is to ingest and destroy microorganisms. Neutrophils help their host fight infections by phagocytosis, degranulation, and neutrophil extracellular traps. Neutrophils are the most common type of circulating white blood cells and the principal cell type in acute inflammatory reactions. A total absence of neutrophils or a significant decrease in their number leads to severe immunodeficiency that renders patients vulnerable to recurrent infections by Staphylococcus aureus and Gram-negative bacteria being the most life-threatening. Neutropenia may be classified as mild, moderate or severe in terms of numbers in the peripheral blood, and intermittent, cyclic, or chronic in terms of duration. Besides well-known classic severe congenital neutropenia, chronic neutropenia appears to be associated with an increasing number of primary immunodeficiency diseases (PIDs), including those of myeloid and lymphoid lineage. A comprehensive overview of the diverse clinical presenting symptoms, classification, aetiological and genetic etiologies of chronic isolated and syndromic neutropenia is aimed to be reviewed.

New insights in phenotype and treatment of lung disease immuno-deficiency and chromosome breakage syndrome (LICS)

We report five patients with lung disease immuno-deficiency and chromosome breakage syndrome (LICS) but without recurrent infections and severe immunodeficiency. One patient had extended survival to 6.5 years. Hematopoietic stem-cell transplantation failed to cure another patient. Our findings suggest that the immunological abnormalities can be limited and do not fully explain the LICS phenotype.