Amplification and Preparation of Cellular O-Glycomes for Functional Glycomics

Mucin-type O-glycans play key roles in many cellular processes, and they are often altered in human diseases. A major challenge in studying the role of O-glycans through functional O-glycomics is the absence of a complete repertoire of the glycans that comprise the human O-glycome. Here we describe a cellular O-glycome preparation strategy, Preparative Cellular O-Glycome Reporter/Amplification (pCORA), that introduces 4-N₃-Bn-GalNAc(Ac)₃ as a novel precursor in large-scale cell cultures to generate usable amounts of O-glycans as a potential O-glycome factory. Cultured human non-small cell lung cancer (NSCLC) A549 cells take up the precursor, which is extended by cellular glycosyltransferases to produce 4-N₃-Bn-α-O-glycans that are secreted into the culture medium. The O-glycan derivatives can be clicked with a fluorescent bifunctional tag that allows multidimensional HPLC purification and production of a tagged glycan library, representing the O-glycome of the corresponding cells. We obtained ∼5% conversion of precursor to O-glycans and purified a tagged O-glycan library of over 100 O-glycan derivatives, many of which were present in >100 nmol amounts and were sequenced by sequential MS fragmentation (MSⁿ). These O-glycans were successfully printed onto epoxy glass slides as an O-glycome shotgun microarray. We used this novel array to explore binding activity of serum IgM in healthy persons and NSCLC patients at different cancer stages. This novel strategy provides access to complex O-glycans in significant quantities and may offer a new route to discovery of potential diagnostic disease biomarkers.

Synthesis and Characterization of Versatile O-Glycan Precursors for Cellular O-Glycomics

Protein O-glycosylation is a universal post-translational modification and plays essential roles in many biological processes. Recently we reported a technology termed cellular O-glycome reporter/amplification (CORA) to amplify and profile mucin-type O-glycans of living cells growing in the presence of peracetylated Benzyl-α-GalNAc (Ac₃GalNAc-α-Bn). However, the application and development of the CORA method are limited by the properties of the precursor benzyl aglycone, which is relatively inert to further chemical modifications. Here we described a rapid parallel microwave-assisted synthesis of Ac₃GalNAc-α-Bn derivatives to identify versatile precursors for cellular O-glycomics. In total, 26 derivatives, including fluorescent and bioorthogonal reactive ones, were successfully synthesized. The precursors were evaluated for their activity as acceptors for T-synthase and for their ability to function as CORA precursors. Several of the precursors possessing useful functional groups were more efficient than Ac₃GalNAc-α-Bn as T-synthase acceptors and cellular O-glycome reporters. These precursors will advance the CORA technology for studies of functional O-glycomics.

Long-acting recombinant fusion protein linking coagulation factor IX with albumin (rIX-FP) in children. Results of a phase 3 trial

A global phase 3 study evaluated the pharmacokinetics, efficacy and safety of a recombinant fusion protein linking coagulation factor IX with albumin (rIX-FP) in 27 previously treated male children (1–11 years) with severe and moderately severe haemophilia B (factor IX [FIX] activity ≤2 IU/dl). All patients received routine prophylaxis once every seven days for up to 77 weeks, and treated any bleeding episodes on-demand. The mean terminal half-life of rIX-FP was 91.4 hours (h), 4.3-fold longer than previous FIX treatment and clearance was 1.11 ml/h/kg, 6.4-fold slower than previous FIX treatment. The median (Q1, Q3) annualised spontaneous bleeding rate was 0.00 (0.00, 0.91) and was similar between the <6 years and ≥6 years age groups, with a weekly median prophylactic dose of 46 IU/kg. In addition, patients maintained a median trough level of 13.4 IU/dl FIX activity on weekly prophylaxis. Overall, 97.2% of bleeding episodes were successfully treated with one or two injections of rIX-FP (95% CI: 92% to 99%), 88.7% with one injection, and 96% of the treatments were rated effective (excellent or good) by the Investigator. No patient developed FIX inhibitors and no safety concerns were identified. These results indicate that rIX-FP is safe and effective for preventing and treating bleeding episodes in children with haemophilia B with weekly prophylaxis. Routine prophylaxis with rIX-FP at treatment intervals of up to 14 days are currently being investigated in children with severe and moderately severe haemophilia B. Clinicaltrials.gov (NCT01662531)

Efficacy, safety and pharmacokinetic profiles of a plasma-derived VWF/FVIII concentrate (VONCENTO®) in subjects with haemophilia A (SWIFT-HA study)

INTRODUCTION

VONCENTO® (CSL Behring) is a plasma-derived, high-concentration, low-volume, high-purity concentrate,which contains a high level of von Willebrand factor (VWF) high-molecular-weight multimers and aVWF/factor VIII (FVIII) ratio of ~2.4:1, similar to Haemate® P (CSL Behring).

METHODS

The pharmacokinetic, efficacy and safety profiles of VONCENTO® were investigated in this multicentre,double-blind, randomised study. Subjects aged ≥ 12 years with haemophilia A who required treatment of nonsurgical bleeds, treatment during surgical events or who were receiving prophylaxis were included. Pharmacokinetics were investigated with a single dose of 50 IU FVIII/kg body weight of either VONCENTO® or BIOSTATE® reference product (Biostate-RP) (Day 1; Day 8 [n= 16], repeated on Day 180 [VONCENTO® only; n=15]). Efficacy and safety analyses were performed either during on-demand treatment (n=52) or prophylaxis (n=29)for ≥ 6 months and ≥ 50 exposure days, respectively.

RESULTS

Besides the confirmation of bioequivalence between VONCENTO® and Biostate-RP, which displayed comparable PK profiles, haemostatic efficacy was rated by the investigators as either 'excellent' or 'good' in 96.4% of all bleeding events (96.5% spontaneous, 96.6% traumatic, 96.9% joint bleeds) as well as in 80% of major and 100% of minor surgical procedures at discharge. The median number of annualised bleeding events per subject [range] was significantly lower in the prophylaxis group (2.0 [0.0-34.6]) than in the on-demand group (14.0 [0.0-87.8], p = 0.0013).VONCENTO® was well tolerated and no inhibitory antibodies were identified during the study period.

CONCLUSIONS

This study demonstrated the bioequivalence of VONCENTO® to Biostate-RP, and its excellent efficacy and safety profile in haemophilia A subjects.

Doa1 is a Cdc48 adapter that possesses a novel ubiquitin binding domain

Cdc48 (p97/VCP) is an AAA-ATPase molecular chaperone whose cellular functions are facilitated by its interaction with ubiquitin binding cofactors (e.g., Npl4-Ufd1 and Shp1). Several studies have shown that Saccharomyces cerevisiae Doa1 (Ufd3/Zzz4) and its mammalian homologue, PLAA, interact with Cdc48. However, the function of this interaction has not been determined, nor has a physiological link between these proteins been demonstrated. Herein, we demonstrate that Cdc48 interacts directly with the C-terminal PUL domain of Doa1. We find that Doa1 possesses a novel ubiquitin binding domain (we propose the name PFU domain, for PLAA family ubiquitin binding domain), which appears to be necessary for Doa1 function. Our data suggest that the PUL and PFU domains of Doa1 promote the formation of a Doa1-Cdc48-ubiquitin ternary complex, potentially allowing for the recruitment of ubiquitinated proteins to Cdc48. DOA1 and CDC48 mutations are epistatic, suggesting that their interaction is physiologically relevant. Lastly, we provide evidence of functional conservation within the PLAA family by showing that a human-yeast chimera binds to ubiquitin and complements doa1Delta phenotypes in yeast. Combined, our data suggest that Doa1 plays a physiological role as a ubiquitin binding cofactor of Cdc48 and that human PLAA may play an analogous role via its interaction with p97/VCP.

PD-L2 is a second ligand for PD-1 and inhibits T cell activation

Programmed death I (PD-I)-deficient mice develop a variety of autoimmune-like diseases, which suggests that this immunoinhibitory receptor plays an important role in tolerance. We identify here PD-1 ligand 2 (PD-L2) as a second ligand for PD-1 and compare the function and expression of PD-L1 and PD-L2. Engagement of PD-1 by PD-L2 dramatically inhibits T cell receptor (TCR)-mediated proliferation and cytokine production by CD4+ T cells. At low antigen concentrations, PD-L2-PD-1 interactions inhibit strong B7-CD28 signals. In contrast, at high antigen concentrations, PD-L2-PD-1 interactions reduce cytokine production but do not inhibit T cell proliferation. PD-L-PD-1 interactions lead to cell cycle arrest in G0/G1 but do not increase cell death. In addition, ligation of PD-1 + TCR leads to rapid phosphorylation of SHP-2, as compared to TCR ligation alone. PD-L expression was up-regulated on antigen-presenting cells by interferon gamma treatment and was also present on some normal tissues and tumor cell lines. Taken together, these studies show overlapping functions of PD-L1 and PD-L2 and indicate a key role for the PD-L-PD-1 pathway in regulatingT cell responses.

ICOS is critical for CD40-mediated antibody class switching

The inducible co-stimulatory molecule (ICOS) is a CD28 homologue implicated in regulating T-cell differentiation. Because co-stimulatory signals are critical for regulating T-cell activation, an understanding of co-stimulatory signals may enable the design of rational therapies for immune-mediated diseases. According to the two-signal model for T-cell activation, T cells require an antigen-specific signal and a second, co-stimulatory, signal for optimal T-cell activation. The co-stimulatory signal promotes T-cell proliferation, lymphokine secretion and effector function. The B7-CD28 pathway provides essential signals for T-cell activation, but does not account for all co-stimulation. We have generated mice lacking ICOS (ICOS-/- ) to determine the essential functions of ICOS. Here we report that ICOS-/- mice exhibit profound deficits in immunoglobulin isotype class switching, accompanied by impaired germinal centre formation. Class switching was restored in ICOS-/- mice by CD40 stimulation, showing that ICOS promotes T-cell/B-cell collaboration through the CD40/CD40L pathway.

Mouse inducible costimulatory molecule (ICOS) expression is enhanced by CD28 costimulation and regulates differentiation of CD4+ T cells

The inducible costimulatory (ICOS) molecule is expressed by activated T cells and has homology to CD28 and CD152. ICOS binds B7h, a molecule expressed by APC with homology to CD80 and CD86. To investigate regulation of ICOS expression and its role in Th responses we developed anti-mouse ICOS mAbs and ICOS-Ig fusion protein. Little ICOS is expressed by freshly isolated mouse T cells, but ICOS is rapidly up-regulated on most CD4(+) and CD8(+) T cells following stimulation of the TCR. Strikingly, ICOS up-regulation is significantly reduced in the absence of CD80 and CD86 and can be restored by CD28 stimulation, suggesting that CD28-CD80/CD86 interactions may optimize ICOS expression. Interestingly, TCR-transgenic T cells differentiated into Th2 expressed significantly more ICOS than cells differentiated into Th1. We used two methods to investigate the role of ICOS in activation of CD4(+) T cells. First, CD4(+) cells were stimulated with beads coated with anti-CD3 and either B7h-Ig fusion protein or control Ig fusion protein. ICOS stimulation enhanced proliferation of CD4(+) cells and production of IFN-gamma, IL-4, and IL-10, but not IL-2. Second, TCR-transgenic CD4(+) T cells were stimulated with peptide and APC in the presence of ICOS-Ig or control Ig. When the ICOS:B7h interaction was blocked by ICOS-Ig, CD4(+) T cells produced more IFN-gamma and less IL-4 and IL-10 than CD4(+) cells differentiated with control Ig. These results demonstrate that ICOS stimulation is important in T cell activation and that ICOS may have a particularly important role in development of Th2 cells.

Engagement of the PD-1 immunoinhibitory receptor by a novel B7 family member leads to negative regulation of lymphocyte activation

PD-1 is an immunoinhibitory receptor expressed by activated T cells, B cells, and myeloid cells. Mice deficient in PD-1 exhibit a breakdown of peripheral tolerance and demonstrate multiple autoimmune features. We report here that the ligand of PD-1 (PD-L1) is a member of the B7 gene family. Engagement of PD-1 by PD-L1 leads to the inhibition of T cell receptor-mediated lymphocyte proliferation and cytokine secretion. In addition, PD-1 signaling can inhibit at least suboptimal levels of CD28-mediated costimulation. PD-L1 is expressed by antigen-presenting cells, including human peripheral blood monocytes stimulated with interferon gamma, and activated human and murine dendritic cells. In addition, PD-L1 is expressed in nonlymphoid tissues such as heart and lung. The relative levels of inhibitory PD-L1 and costimulatory B7-1/B7-2 signals on antigen-presenting cells may determine the extent of T cell activation and consequently the threshold between tolerance and autoimmunity. PD-L1 expression on nonlymphoid tissues and its potential interaction with PD-1 may subsequently determine the extent of immune responses at sites of inflammation.