Concise Communication

Abstract

Risk for childhood asthma is conferred by alleles within the 17q21 locus affecting ORMDL sphingolipid biosynthesis regulator 3 (ORMDL3) expression. ORMDL3 inhibits sphingolipid de novo synthesis. Although the effects of 17q21 genotypes on sphingolipid synthesis in human asthma remain unclear, both decreased sphingolipid synthesis and ORMDL3 overexpression are linked to airway hyperreactivity. To characterize the relationship of genetic asthma susceptibility with sphingolipid synthesis, we analyzed asthma-associated 17q21 genotypes (rs7216389, rs8076131, rs4065275, rs12603332, and rs8067378) in both children with asthma and those without asthma, quantified plasma and whole-blood sphingolipids, and assessed sphingolipid de novo synthesis in peripheral blood cells by measuring the incorporation of stable isotope–labeled serine (substrate) into sphinganine and sphinganine-1-phosphate. Whole-blood dihydroceramides and ceramides were decreased in subjects with the 17q21 asthma–risk alleles rs7216389 and rs8076131. Children with nonallergic asthma had lower dihydroceramides, ceramides, and sphingomyelins than did controls. Children with allergic asthma had higher dihydroceramides, ceramides, and sphingomyelins compared with children with nonallergic asthma. Additionally, de novo sphingolipid synthesis was lower in children with asthma compared with controls. These findings connect genetic 17q21 variations that are associated with asthma risk and higher ORMDL3 expression to lower sphingolipid synthesis in humans. Altered sphingolipid synthesis may therefore be a critical factor in asthma pathogenesis and may guide the development of future therapeutics.

Authors

Jennie G. Ono, Benjamin I. Kim, Yize Zhao, Paul J. Christos, Yohannes Tesfaigzi, Tilla S. Worgall, Stefan Worgall

×

Abstract

CD4+ T cell failure is a hallmark of chronic hepatitis C virus (HCV) infection. However, the mechanisms underlying the impairment and loss of virus-specific CD4+ T cells in persisting HCV infection remain unclear. Here we examined HCV-specific CD4+ T cells longitudinally during acute infection with different infection outcomes. We found that HCV-specific CD4+ T cells are characterized by expression of a narrower range of T cell inhibitory receptors compared with CD8+ T cells, with initially high expression levels of PD-1 and CTLA-4 that were associated with negative regulation of proliferation in all patients, irrespective of outcome. In addition, HCV-specific CD4+ T cells were phenotypically similar during early resolving and persistent infection and secreted similar levels of cytokines. However, upon viral control, CD4+ T cells quickly downregulated inhibitory receptors and differentiated into long-lived memory cells. In contrast, persisting viremia continued to drive T cell activation and PD-1 and CTLA-4 expression, and blocked T cell differentiation, until the cells quickly disappeared from the circulation. Our data support an important and physiological role for inhibitory receptor–mediated regulation of CD4+ T cells in early HCV infection, irrespective of outcome, with persistent HCV viremia leading to sustained upregulation of PD-1 and CTLA-4.

Authors

Diana Y. Chen, David Wolski, Jasneet Aneja, Lyndon Matsubara, Brandon Robilotti, Garrett Hauck, Paulo Sergio Fonseca de Sousa, Sonu Subudhi, Carlos Augusto Fernandes, Ruben C. Hoogeveen, Arthur Y. Kim, Lia Lewis-Ximenez, Georg M. Lauer

×

Abstract

Chronic hepatitis C virus (HCV) infection is characterized by persistent high-level viremia and defective cellular immunity, including a lack of functional HCV-specific CD4+ T cells. We previously described an exceptional period of viral control that occurs in some chronically infected women after childbirth. Here, we investigated whether reduced HCV replication after pregnancy is associated with recovery of CD4+ T cell immunity. Class II tetramer analysis revealed significantly greater frequencies of circulating HCV-specific CD4+ T cells at 3 months postpartum in women with concurrent declines in viremia compared with those with stable viremia. These HCV-specific CD4+ T cells had an effector-memory phenotype. Inhibitory coreceptor expression on these cells corresponded to the degree of viral control. Circulating CD4+ T cells produced IL-2 and IFN-γ after HCV antigen stimulation, demonstrating Th1 functionality. These data provide direct evidence that the profound loss of HCV-specific CD4+ T cell help that results in chronic infection is reversible following pregnancy, and this recovery of CD4+ T cells is associated with at least transient control of persistent viral replication.

Authors

Samantha L. Coss, Almudena Torres-Cornejo, Mona R. Prasad, Melissa Moore-Clingenpeel, Arash Grakoui, Georg M. Lauer, Christopher M. Walker, Jonathan R. Honegger

×

Abstract

Cancer–related anemia is present in over 60% of newly diagnosed cancer patients and is associated with substantial morbidity and high medical costs. Drugs that enhance erythropoiesis are urgently required to decrease transfusion rates and improve quality of life. Clinical studies have observed an unexpected improvement in hemoglobin and red blood cell (RBC) transfusion-independence in AML patients treated with the isocitrate dehydrogenase 2 (IDH2) mutant-specific inhibitor, enasidenib, leading to improved quality of life without a reduction in AML disease burden. Here, we demonstrate that enasidenib enhanced human erythroid differentiation of hematopoietic progenitors. The phenomenon was not observed with other IDH1/2 inhibitors and occurred in IDH2-deficient CRIPSR-engineered progenitors independently of D-2-hydroxyglutarate. The effect of enasidenib on hematopoietic progenitors was mediated by protoporphyrin accumulation, driving heme production and erythroid differentiation in committed CD71+ progenitors rather than hematopoietic stem cells. Our results position enasidenib as a promising therapeutic agent for improvement of anemia and provide the basis for a clinical trial using enasidenib to decrease transfusion dependence in a wide array of clinical contexts.

Authors

Ritika Dutta, Tian Yi Zhang, Thomas Köhnke, Daniel Thomas, Miles Linde, Eric Gars, Melissa Stafford, Satinder Kaur, Yusuke Nakauchi, Raymond Yin, Armon Azizi, Anupama Narla, Ravindra Majeti

×

Abstract

Staphylococcus aureus remains a leading cause of human infection. These infections frequently recur when the skin is a primary site of infection, especially in infants and children. In contrast, invasive staphylococcal disease is less commonly associated with reinfection, suggesting that tissue-specific mechanisms govern the development of immunity. Knowledge of how S. aureus manipulates protective immunity has been hampered by a lack of antigen-specific models to interrogate the T cell response. Utilizing a chicken egg ovalbumin (OVA)-expressing S. aureus strain to analyze OVA-specific T cell responses, we demonstrated that primary skin infection is associated with impaired development of T cell memory. Conversely, invasive infection induced antigen-specific memory and protected against reinfection. This defect in adaptive immunity following skin infection was associated with a loss of dendritic cells, attributable to S. aureus α-toxin (Hla) expression. Genetic and immunization-based approaches to protect against Hla during skin infection restored the T cell response. Within the human population, exposure to α-toxin through skin infection may modulate the establishment of T cell-mediated immunity, adversely impacting long-term protection. These studies prompt consideration that vaccination targeting S. aureus may be most effective if delivered prior to initial contact with the organism.

Authors

Brandon Lee, Reuben Olaniyi, Jakub Kwiecinski, Juliane Bubeck Wardenburg

×

Abstract

Cantu Syndrome (CS) is a complex disorder caused by gain-of-function (GoF) mutations in ABCC9 and KCNJ8, which encode the SUR2 and Kir6.1 subunits, respectively, of vascular smooth muscle (VSM) KATP channels. CS includes dilated vasculature, marked cardiac hypertrophy, and other cardiovascular abnormalities. There is currently no targeted therapy, and it is unknown whether cardiovascular features can be reversed once manifest. Using combined transgenic and pharmacological approaches in a knock-in mouse model of CS, we have shown that reversal of vascular and cardiac phenotypes can be achieved (1) by genetic downregulation of KATP channel activity specifically in VSM, and (2) by chronic administration of the clinically-used KATP channel inhibitor, glibenclamide. These findings demonstrate (i) that VSM KATP channel GoF underlies CS cardiac enlargement, (ii) reversibility of CS-associated abnormalities and (iii) evidence of in vivo efficacy of glibenclamide as a therapeutic agent in CS.

Authors

Conor McClenaghan, Yan Huang, Zihan Yan, Theresa Harter, Carmen M. Halabi, Rod Chalk, Attila Kovacs, Gijs van Haaften, Maria S. Remedi, Colin G. Nichols

×

Abstract

Cancer cachexia is a major cause of patient morbidity and mortality, with no efficacious treatment or management strategy. Despite sharing pathophysiological features with a number of neuromuscular wasting conditions, including age-related sarcopenia, the mechanisms underlying cachexia remain poorly understood. Studies of related conditions suggest that pathological targeting of the neuromuscular junction (NMJ) may play a key role in cachexia, but this has yet to be investigated in human patients. Here, high-resolution morphological analyses were undertaken on NMJs of rectus abdominis obtained from patients undergoing upper GI cancer surgery compared with controls (N=30; n=1,165 NMJs). Cancer patients included those with cachexia and weight-stable disease. Despite the low skeletal muscle index and significant muscle fibre atrophy in patients with cachexia, NMJ morphology was fully conserved. No significant differences were observed in any of the pre- and post-synaptic variables measured. We conclude that NMJs remain structurally intact in rectus abdominis in both cancer and cachexia, suggesting that denervation of skeletal muscle is not a major driver of pathogenesis. The absence of NMJ pathology is in stark contrast to related conditions, such as age-related sarcopenia, and supports the hypothesis that intrinsic changes within skeletal muscle, independent of any changes in motor neurons, represent the primary locus of neuromuscular pathology in cancer cachexia.

Authors

Ines Boehm, Janice Miller, Thomas M. Wishart, Stephen J. Wigmore, Richard J.E. Skipworth, Ross A. Jones, Thomas H. Gillingwater

×

Abstract

Ventriculomegaly and hydrocephalus are associated with loss of function of glycine decarboxylase (Gldc) in mice and in humans suffering from Non-Ketotic Hyperglycinemia (NKH), a neurometabolic disorder characterised by accumulation of excess glycine. Here, we showed that ventriculomegaly in Gldc-deficient mice is preceded by stenosis of the Sylvian aqueduct and malformation or absence of the sub-commissural organ and pineal gland. Gldc functions in the glycine cleavage system, a mitochondrial component of folate metabolism, whose malfunction results in accumulation of glycine and diminished supply of glycine-derived one-carbon units to the folate cycle. We showed that inadequate one-carbon supply, as opposed to excess glycine is the cause of hydrocephalus associated with loss of function of the glycine cleavage system. Maternal supplementation with formate prevented both ventriculomegaly, as assessed at pre-natal stages, and post-natal development of hydrocephalus in Gldc-deficient mice. Furthermore, ventriculomegaly was rescued by genetic ablation of 5,10-methylene tetrahydrofolate reductase (Mthfr), which results in retention of one-carbon groups in the folate cycle at the expense of transfer to the methylation cycle. In conclusion, a defect in folate metabolism can lead to pre-natal aqueduct stenosis and resultant hydrocephalus. These defects are preventable by maternal supplementation with formate, which acts as a one-carbon donor.

Authors

Chloe Santos, Yun Jin Pai, M. Raasib Mahmood, Kit-Yi Leung, Dawn Savery, Simon N. Waddington, Andrew J. Copp, Nicholas D.E. Greene

×

Abstract

Omalizumab is an anti-IgE monoclonal antibody (mAb) approved for the treatment of severe asthma and chronic spontaneous urticaria. Use of Omalizumab is associated with reported side effects, ranging from local skin inflammation at the injection site to systemic anaphylaxis. To date, the mechanisms through which Omalizumab induces adverse reactions are still unknown. Here, we demonstrated that immune complexes formed between Omalizumab and IgE can induce both skin inflammation and anaphylaxis through engagement of IgG receptors (FcγRs) in FcγR-humanized mice. We further developed an Fc-engineered mutant version of Omalizumab, and demonstrated that this mAb is equally potent as Omalizumab at blocking IgE-mediated allergic reactions, but does not induce FcγR-dependent adverse reactions. Overall, our data indicate that Omalizumab can induce skin inflammation and anaphylaxis by engaging FcγRs, and demonstrate that Fc-engineered versions of the mAb could be used to reduce such adverse reactions.

Authors

Bianca Balbino, Pauline Herviou, Ophélie Godon, Julien Stackowicz, Odile Richard-Le Goff, Bruno Iannascoli, Delphine Sterlin, Sébastien Brûlé, Gael A. Millot, Faith M. Harris, Vera A. Voronina, Kari C. Nadeau, Lynn E. Macdonald, Andrew J. Murphy, Pierre Bruhns, Laurent L. Reber

×

Abstract

Cancer immune evasion is achieved through multiple layers of immune tolerance mechanisms including immune editing, recruitment of tolerogenic immune cells, and secretion of immune suppressive cytokines. Recent success with immune checkpoint inhibitors in cancer immunotherapy suggests a dysfunctional immune synapse as a pivotal tolerogenic mechanism. Tumor cells express immune synapse proteins to suppress the immune system, which is often modulated by epigenetic mechanisms. When the methylation status of key immune synapse genes was interrogated, we observed disproportionately hyper-methylated co-stimulatory genes and hypo-methylation of immune checkpoint genes, which were negatively associated with functional T-cell recruitment to the tumor microenvironment. Therefore, the methylation status of immune synapse genes reflects tumor immunogenicity and correlates with survival.

Authors

Anders Berglund, Matthew Mills, Ryan M. Putney, Imène Hamaidi, James Mulé, Sungjune Kim

×

No posts were found with this tag.