Enhanced in vivo efficacy of a type I interferon superagonist with extended plasma half-life in a mouse model of multiple sclerosis.

IFNß is a common therapeutic option to treat multiple sclerosis. It is unique among the family of type I IFNs in that it binds to the interferon receptors with high affinity, conferring exceptional biological properties. We have previously reported the generation of an interferon superagonist (dubbed YNSα8) that is built on the backbone of a low affinity IFNα but modified to exhibit higher receptor affinity than even for IFNß. Here, YNSα8 was fused with a 600-residue hydrophilic, unstructured N-terminal polypeptide chain comprising proline, alanine, and serine (PAS) to prolong its plasma half-life via "PASylation." PAS-YNSα8 exhibited a 10-fold increased half-life in both pharmacodynamic and pharmacokinetic assays in a transgenic mouse model harboring the human receptors, notably without any detectable loss in biological potency or bioavailability. This long-lived superagonist conferred significantly improved protection from MOG35-55-induced experimental autoimmune encephalomyelitis compared with IFNß, despite being injected with a 4-fold less frequency and at an overall 16-fold lower dosage. These data were corroborated by FACS measurements showing a decrease of CD11b(+)/CD45(hi) myeloid lineage cells detectable in the CNS, as well as a decrease in IBA(+) cells in spinal cord sections determined by immunohistochemistry for PAS-YNSα8-treated animals. Importantly, PAS-YNSα8 did not induce antibodies upon repeated administration, and its biological efficacy remained unchanged after 21 days of treatment. A striking correlation between increased levels of CD274 (PD-L1) transcripts from spleen-derived CD4(+) cells and improved clinical response to autoimmune encephalomyelitis was observed, indicating that, at least in this mouse model of multiple sclerosis, CD274 may serve as a biomarker to predict the effectiveness of IFN therapy to treat this complex disease.

Binding and activity of all human alpha interferon subtypes.

Vertebrates have multiple genes encoding Type I interferons (IFN), for reasons that are not fully understood. The Type I IFN appear to bind to the same heterodimeric receptor and the subtypes have been shown to have different potencies in various experimental systems. To put this concept on a quantitative basis, we have determined the binding affinities and rate constants of 12 human Alpha-IFN subtypes to isolated interferon receptor chains 1 and 2. Alpha-IFNs bind IFNAR1 and IFNAR2 at affinities of 0.5-5 µM and 0.4-5 nM respectively (except for IFN-alpha1 - 220 nM). Additionally we have examined the biological activity of these molecules in several antiviral and antiproliferative models. Particularly for antiproliferative potency, the binding affinity and activity correlate. However, the EC50 values differ significantly (1.5 nM versus 0.1 nM for IFN-alpha2 in WISH versus OVCAR cells). For antiviral potency, there are several instances where the relationship appears to be more complicated than simple binding. These results will serve as a point of reference for further understanding of this multiple ligand/receptor system.

A quantitative, real-time assessment of binding of peptides and proteins to gold surfaces.

Interactions of peptides and proteins with inorganic surfaces are important to both natural and artificial systems; however, a detailed understanding of such interactions is lacking. In this study, we applied new approaches to quantitatively measure the binding of amino acids and proteins to gold surfaces. Real-time surface plasmon resonance (SPR) measurements showed that TEM1-ß-lactamase inhibitor protein (BLIP) interacts only weakly with Au nanoparticles (NPs). However, fusion of three histidine residues to BLIP (3H-BLIP) resulted in a significant increase in the binding to the Au NPs, which further increased when the histidine tail was extended to six histidines (6H-BLIP). Further increasing the number of His residues had no effect on the binding. A parallel study using continuous (111)-textured Au surfaces and single-crystalline, (111)-oriented, Au islands by ellipsometry, FTIR, and localized surface plasmon resonance (LSPR) spectroscopy further confirmed the results, validating the broad applicability of Au NPs as model surfaces. Evaluating the binding of all other natural amino acid homotripeptides fused to BLIP (except Cys and Pro) showed that aromatic and positively-charged residues bind preferentially to Au with respect to small aliphatic and negatively charged residues, and that the rate of association is related to the potency of binding. The binding of all fusions was irreversible. These findings were substantiated by SPR measurements of synthesized, free, soluble tripeptides using Au-NP-modified SPR chips. Here, however, the binding was reversible allowing for determination of binding affinities that correlate with the binding potencies of the related BLIP fusions. Competition assays performed between 3H-BLIP and the histidine tripeptide (3 His) suggest that Au binding residues promote the adsorption of proteins on the surface, and by this facilitate the irreversible interaction of the polypeptide chain with Au. The binding of amino acids to Au was simulated by using a continuum solvent model, showing agreement with the experimental values. These results, together with the observed binding potencies and kinetics of the BLIP fusions and free peptides, suggest a binding mechanism that is markedly different from biological protein-protein interactions.

Bridging the species divide: transgenic mice humanized for type-I interferon response.

We have generated transgenic mice that harbor humanized type I interferon receptors (IFNARs) enabling the study of type I human interferons (Hu-IFN-Is) in mice. These "HyBNAR" (Hybrid IFNAR) mice encode transgenic variants of IFNAR1 and IFNAR2 with the human extracellular domains being fused to transmembrane and cytoplasmic segments of mouse sequence. B16F1 mouse melanoma cells harboring the HyBNAR construct specifically bound Hu-IFN-Is and were rendered sensitive to Hu-IFN-I stimulated anti-proliferation, STAT1 activation and activation of a prototypical IFN-I response gene (MX2). HyBNAR mice were crossed with a transgenic strain expressing the luciferase reporter gene under the control of the IFN-responsive MX2 promoter (MX2-Luciferase). Both the HyBNAR and HyBNAR/MX2-Luciferase mice were responsive to all Hu-IFN-Is tested, inclusive of IFNα2A, IFNß, and a human superagonist termed YNSα8. The mice displayed dose-dependent pharmacodynamic responses to Hu-IFN-I injection, as assessed by measuring the expression of IFN-responsive genes. Our studies also demonstrated a weak activation of endogenous mouse interferon response, especially after high dose administration of Hu-IFNs. In sharp contrast to data published for humans, our pharmacodynamic readouts demonstrate a very short-lived IFN-I response in mice, which is not enhanced by sub-cutaneous (SC) injections in comparison to other administration routes. With algometric differences between humans and mice taken into account, the HyBNAR mice provides a convenient non-primate pre-clinical model to advance the study of human IFN-Is.

An interferon alpha2 mutant optimized by phage display for IFNAR1 binding confers specifically enhanced antitumor activities.

All alpha-interferons (IFNalpha) bind the IFNAR1 receptor subunit with low affinity. Increasing the binding affinity was shown to specifically increase the antiproliferative potency of IFNalpha2. Here, we constructed a phage display library by randomizing three positions on IFNalpha2 previously shown to confer weak binding to IFNAR1. The tightest binding variant selected, comprised of mutations H57Y, E58N, and Q61S (YNS), was shown to bind IFNAR1 60-fold tighter compared with wild-type IFNalpha2, and 3-fold tighter compared with IFNbeta. Binding of YNS to IFNAR2 was comparable with wild-type IFNalpha2. The YNS mutant conferred a 150-fold higher antiproliferative potency in WISH cells compared with wild-type IFNalpha2, whereas its antiviral activity was increased by only 3.5-fold. The high antiproliferative activity was related to an induction of apoptosis, as demonstrated by annexin V binding assays, and to specific gene induction, particularly TRAIL. To determine the potency of the YNS mutant in a xenograft cancer model, we injected it twice a week to nude mice carrying transplanted MDA231 human breast cancer cells. After 5 weeks, no tumors remained in mice treated with YNS, whereas most mice treated with wild-type IFNalpha2 showed visible tumors. Histological analysis of these tumors showed a significant anti-angiogenic effect of YNS, compared with wild-type IFNalpha2. This work demonstrates the application of detailed biophysical understanding in the process of protein engineering, yielding an interferon variant with highly increased biological potency.