Optimal immune responses require both an antigen-specific and a co-stimulatory signal. The shared ligands B7-1 and B7-2 on antigen-presenting cells deliver the co-stimulatory signal through CD28 and CTLA-4 on T cells. Signalling through CD28 augments the T-cell response, whereas CTLA-4 signalling attenuates it. Numerous animal studies and recent clinical trials indicate that manipulating these interactions holds considerable promise for immunotherapy. With the consequences of these signals well established, and details of the downstream signalling events emerging, understanding the molecular nature of these extracellular interactions becomes crucial. Here we report the crystal structure of the human CTLA-4/B7-1 co-stimulatory complex at 3.0 A resolution. In contrast to other interacting cell-surface molecules, the relatively small CTLA-4/B7-1 binding interface exhibits an unusually high degree of shape complementarity. CTLA-4 forms homodimers through a newly defined interface of highly conserved residues. In the crystal lattice, CTLA-4 and B7-1 pack in a strikingly periodic arrangement in which bivalent CTLA-4 homodimers bridge bivalent B7-1 homodimers. This zipper-like oligomerization provides the structural basis for forming unusually stable signalling complexes at the T-cell surface, underscoring the importance of potent inhibitory signalling in human immune responses.

The long circulating half-life of serum albumin, the most abundant protein in mammalian plasma, derives from pH-dependent endosomal salvage from degradation, mediated by the neonatal Fc receptor (FcRn). Using yeast display, we identified human serum albumin (HSA) variants with increased affinity for human FcRn at endosomal pH, enabling us to solve the crystal structure of a variant HSA/FcRn complex. We find an extensive, primarily hydrophobic interface stabilized by hydrogen-bonding networks involving protonated histidines internal to each protein. The interface features two key FcRn tryptophan side chains inserting into deep hydrophobic pockets on HSA that overlap albumin ligand binding sites. We find that fatty acids (FAs) compete with FcRn, revealing a clash between ligand binding and recycling, and that our high-affinity HSA variants have significantly increased circulating half-lives in mice and monkeys. These observations open the way for the creation of biotherapeutics with significantly improved pharmacokinetics.

Primary hyperoxaluria type 1 (PH1), an inherited rare disease of glyoxylate metabolism, arises from mutations in the enzyme alanine-glyoxylate aminotransferase. The resulting deficiency in this enzyme leads to abnormally high oxalate production resulting in calcium oxalate crystal formation and deposition in the kidney and many other tissues, with systemic oxalosis and ESRD being a common outcome. Although a small subset of patients manages the disease with vitamin B6 treatments, the only effective treatment for most is a combined liver-kidney transplant, which requires life-long immune suppression and carries significant mortality risk. In this report, we discuss the development of ALN-GO1, an investigational RNA interference (RNAi) therapeutic targeting glycolate oxidase, to deplete the substrate for oxalate synthesis. Subcutaneous administration of ALN-GO1 resulted in potent, dose-dependent, and durable silencing of the mRNA encoding glycolate oxidase and increased serum glycolate concentrations in wild-type mice, rats, and nonhuman primates. ALN-GO1 also increased urinary glycolate concentrations in normal nonhuman primates and in a genetic mouse model of PH1. Notably, ALN-GO1 reduced urinary oxalate concentration up to 50% after a single dose in the genetic mouse model of PH1, and up to 98% after multiple doses in a rat model of hyperoxaluria. These data demonstrate the ability of ALN-GO1 to reduce oxalate production in preclinical models of PH1 across multiple species and provide a clear rationale for clinical trials with this compound.

Protein tyrosine phosphatase 1B (PTP1B) is a negative regulator of the insulin and leptin receptor pathways and thus an attractive therapeutic target for diabetes and obesity. Starting with a high micromolar lead compound, structure-based optimization of novel PTP1B inhibitors by extension of the molecule from the enzyme active site into the second phosphotyrosine binding site is described. Medicinal chemistry, guided by X-ray complex structure and molecular modeling, has yielded low nanomolar PTP1B inhibitors in an efficient manner. Compounds from this chemical series were found to be actively transported into hepatocytes. This active uptake into target tissues could be one of the possible avenues to overcome the poor membrane permeability of PTP1B inhibitors.

ObjectiveTo identify changes in the proteome associated with onset and progression of ATTRv amyloidosis, we performed an observational, case-controlled study which compared proteomes of patients with ATTRv amyloidosis and healthy controls.MethodsPlasma levels of >1,000 proteins were measured in patients with ATTRv amyloidosis with polyneuropathy who received either placebo or patisiran in the APOLLO study and in healthy controls. The impact of patisiran on the time profile of each protein was determined by linear mixed model at 0, 9, and 18 months. Neurofilament light chain (NfL) was further assessed using an orthogonal quantitative approach.ResultsLevels of 66 proteins were significantly changed with patisiran vs placebo, with NfL change most significant (p < 10−20). Analysis of changes in protein levels demonstrated that the proteome of patisiran-treated patients trended toward healthy controls at 18 months. Healthy controls' NfL levels were 4-fold lower than in patients with ATTRv amyloidosis with polyneuropathy (16.3 vs 69.4 pg/mL, effect: −53.1 pg/mL, 95% CI [–60.5 to −45.9]). NfL levels at 18 months increased with placebo (99.5 vs 63.2 pg/mL, 36.3 pg/mL, [16.5–56.1]) and decreased with patisiran treatment (48.8 vs 72.1 pg/mL, −23.3 pg/mL, [–33.4 to −13.1]) from baseline. At 18 months, improvement in modified Neuropathy Impairment Score +7 following patisiran significantly correlated with reduced NfL (R = 0.43, [0.29–0.55]).ConclusionsFindings suggest NfL may serve as a biomarker of nerve damage and polyneuropathy in ATTRv amyloidosis, may enable earlier diagnosis of patients with ATTRv amyloidosis, and facilitate monitoring of disease progression.Classification of evidenceThis study provides Class III evidence that NfL levels may enable earlier diagnosis of polyneuropathy in patients with ATTRv amyloidosis and facilitate monitoring of disease progression.

No abstract

Abstract. E-selectin elicits cell adhesion by binding to the cell surface carbohydrate, sialyl Lewis X (sLex). We evaluated the effects of mutations in the E-selectin lectin domain on the binding of a panel of anti-E-selectin mAbs and on the recognition of immobilized sLe x glycolipid. Functional residues were then superimposed onto a three-dimensional model of the E-selectin lectin domain. This analysis demonstrated that the epitopes recognized by blocking mAbs map to a patch near the antiparallel beta sheet derived from the NH2 and COOH termini of the lectin domain and two adjacent loops. Mutations that affect sLe ~ binding map to this same region. These results thus define a small region of the E-selectin lectin domain that is critical for carbohydrate recognition.

Abstract. The selectins are a family of three calciumdependent lectins that mediate adhesive interactions between leukocytes and the endothelium during normal and abnormal inflammatory episodes. Previous work has implicated the carbohydrate sialyl Lewis x (sLex; sialic acid alpha 2-3 galactose beta 1-4 [Fucose alpha 1-3] N-acetyl glucosamine) as a component of the ligand recognized by E-and P-selectin. In the case of P-selectin, other components of the cell surface, including 2'6-1inked sialic acid and sulfatide (galactose-4-sulfate ceramide), have also been proposed for adhesion mediated by this selectin. We have recently defined a region of the E-selectin lectin domain that appears to be directly involved with carbohydrate rec- Here we describe a similar analysis of the P-selectin lectin domain which demonstrates that a homologous region of this glycoprotein's lectin motif is involved with carbohydrate recognition and cell binding. In addition, we present evidence that is inconsistent with a biological role for either 2 '6-1inked sialic acid or sulfatide in P-selectin-mediated adhesion. These results suggest that a common region of the E-and P-selectin tectin domains appears to mediate carbohydrate recognition and cell adhesion.