Live long and active: Polypeptide-mediated assembly of antibody variable fragments.

Antibodies possess multiple biologically relevant features that have been engineered into new therapeutic formats. Two examples include the adaptable specificity of their variable (Fv) region and the extension of plasma circulation times through their crystallizable (Fc) region. Since the invention of the single chain variable fragment (scFv) in 1988, antibody variable regions have been re-engineered into a wide variety of multifunctional nanostructures. Among these strategies, peptide-mediated self-assembly of variable regions through heterologous expression has become a powerful method to produce homogenous, functional biomaterials. This manuscript reviews recent reports of antibody fragments assembled through fusion with peptides and proteins, including elastin-like polypeptides (ELPs), collagen-like polypeptides (CLPs), albumin, transmembrane proteins, leucine zippers, silk protein, and viruses. This review further discusses the current clinical status of engineered antibody fragments and challenges to overcome.

Adaptable antibody Nanoworms designed for non-Hodgkin lymphoma.

Despite advancements in antibody-based therapies for non-Hodgkin lymphoma (NHL), at least two major therapeutic needs remain unmet: i) heterogenous activation of host immunity towards B cell NHL; and ii) lack of antibody-based therapeutics for T cell NHL. This study explores the molecular characteristics of an adaptable modality called antibody Nanoworms and demonstrates their receptor clustering activity as a means to overcome and address abovementioned needs. To test this, four selected therapeutic receptors of B cell (CD19, CD20, HLA-DR10) and T cell (CD3) NHL were targeted by Nanoworms. Regardless of the target or the cell type, Nanoworms inherently clustered bound receptors on the cell-surface through their multivalency and activated intracellular signaling without any secondary crosslinker. As a sole agent, Nanoworms induced apoptosis by clustering CD20 or HLA-DR10, and arrested the cell cycle upon CD19 clustering. Interestingly, CD3 clustering was particularly advantageous in inducing activation-induced cell death (AICD) in an aggressive form of T cell NHL named Sézary syndrome that is fatal, limited in antibody-based therapeutics, and has poor outcomes to traditional chemotherapy. As Nanoworms can be easily designed to target any receptor for which a scFv is available, they may provide solutions and add therapeutic novelty to underserved diseases.

Biosynthesized Multivalent Lacritin Peptides Stimulate Exosome Production in Human Corneal Epithelium.

Lacripep is a therapeutic peptide derived from the human tear protein, Lacritin. Lacripep interacts with syndecan-1 and induces mitogenesis upon the removal of heparan sulfates (HS) that are attached at the extracellular domain of syndecan-1. The presence of HS is a prerequisite for the syndecan-1 clustering that stimulates exosome biogenesis and release. Therefore, syndecan-1-mediated mitogenesis versus HS-mediated exosome biogenesis are assumed to be mutually exclusive. This study introduces a biosynthesized fusion between Lacripep and an elastin-like polypeptide named LP-A96, and evaluates its activity on cell motility enhancement versus exosome biogenesis. LP-A96 activates both downstream pathways in a dose-dependent manner. HCE-T cells at high confluence treated with 1 µM LP-A96 enhanced cell motility equipotent to Lacripep. However, cells at low density treated with 1 µM LP-A96 generated a 210-fold higher number of exosomes compared to those treated at low density with Lacripep. As monovalent Lacripep is capable of enhancing cell motility but not exosome biogenesis, activation of exosome biogenesis by LP-A96 not only suggests its utility as a novel molecular tool to study the Lacritin biology in the corneal epithelium but also implies activity as a potential therapeutic peptide that can further improve ocular surface health through the induction of exosomes.

Inhibition of Cathepsin S Reduces Lacrimal Gland Inflammation and Increases Tear Flow in a Mouse Model of Sjögren's Syndrome.

Cathepsin S (CTSS) is highly increased in Sjögren's syndrome (SS) patients tears and in tears and lacrimal glands (LG) of male non-obese diabetic (NOD) mice, a murine model of SS. To explore CTSS's utility as a therapeutic target for mitigating ocular manifestations of SS in sites where CTSS is increased in disease, the tears and the LG (systemically), the peptide-based inhibitor, Z-FL-COCHO (Z-FL), was administered to 14-15 week male NOD mice. Systemic intraperitoneal (i.p.) injection for 2 weeks significantly reduced CTSS activity in tears, LG and spleen, significantly reduced total lymphocytic infiltration into LG, reduced CD3+ and CD68+ cell abundance within lymphocytic infiltrates, and significantly increased stimulated tear secretion. Topical administration of Z-FL to a different cohort of 14-15 week male NOD mice for 6 weeks significantly reduced only tear CTSS while not affecting LG and spleen CTSS and attenuated the disease-progression related reduction of basal tear secretion, while not significantly impacting lymphocytic infiltration of the LG. These findings suggest that CTSS inhibitors administered either topically or systemically can mitigate aspects of the ocular manifestations of SS.

Thermally-Responsive Loading and Release of Elastin-Like Polypeptides from Contact Lenses.

Contact lenses are widely prescribed for vision correction, and as such they are an attractive platform for drug delivery to the anterior segment of the eye. This manuscript explores a novel strategy to drive the reversible adsorption of peptide-based therapeutics using commercially available contact lenses. To accomplish this, thermo-sensitive elastin-like polypeptides (ELPs) alone or tagged with a candidate ocular therapeutic were characterized. For the first time, this manuscript demonstrates that Proclear CompatiblesTM contact lenses are a suitable platform for ELP adsorption. Two rhodamine-labelled ELPs, V96 (thermo-sensitive) and S96 (thermo-insensitive), were employed to test temperature-dependent association to the contact lenses. During long-term release into solution, ELP coacervation significantly modulated the release profile whereby more than 80% of loaded V96 retained with a terminal half-life of ~4 months, which was only 1-4 days under solubilizing conditions. A selected ocular therapeutic candidate lacritin-V96 fusion (LV96), either free or lens-bound LV96, was successfully transferred to HCE-T cells. These data suggest that ELPs may be useful to control loading or release from certain formulations of contact lenses and present a potential for this platform to deliver a biologically active peptide to the ocular surface via contact lenses.

Berunda Polypeptides: Biheaded Rapamycin Carriers for Subcutaneous Treatment of Autoimmune Dry Eye Disease.

The USFDA-approved immunosuppressive drug rapamycin (Rapa), despite its potency, is limited by poor bioavailability and a narrow therapeutic index. In this study, we sought to improve bioavailability of Rapa with subcutaneous (SC) administration and to test its therapeutic feasibility and practicality in a murine model of Sjögren's syndrome (SS), a systemic autoimmune disease with no approved therapies. To improve its therapeutic index, we formulated Rapa with a carrier termed FAF, a fusion of the human cytosolic FK506-binding protein 12 (FKBP12) and an elastin-like polypeptide (ELP). The resulting 97 kDa FAF (i) has minimal burst release, (ii) is "humanized", (iii) is biodegradable, (iv) solubilizes two Rapa per FAF, and (v) avoids organic solvents or amphiphilic carriers. Demonstrating high stability, FAF remained soluble and monodisperse with a hydrodynamic radius of 8 nm at physiological temperature. A complete pharmacokinetic (PK) analysis of FAF revealed that the bioavailability of SC FAF was 60%, with significantly higher blood concentration during the elimination phase compared to IV FAF. The plasma concentration of Rapa delivered by FAF was 8-fold higher with a significantly increased plasma-to-whole blood ratio relative to free Rapa, 24 h after injection. To evaluate therapeutic effects, FAF-Rapa was administered SC every other day for 2 weeks to male non-obese diabetic (NOD) mice, which develop an SS-like autoimmune-mediated lacrimal gland (LG) inflammation and other characteristic features of SS. Both FAF-Rapa and free Rapa exhibited immunomodulatory effects by significantly suppressing lymphocytic infiltration, gene expression of IFN-γ, MHC II, type I collagen and IL-12a, and cathepsin S (CTSS) activity in LG compared to controls. Serum chemistry and histopathological analyses in major organs revealed no apparent toxicity of FAF-Rapa. Given its improved PK and equipotent therapeutic efficacy compared to free Rapa, FAF-Rapa is of further interest for systemic treatments for autoimmune diseases like SS.

A novel elastin-like polypeptide drug carrier for cyclosporine A improves tear flow in a mouse model of Sjögren's syndrome.

As a potent macrolide immunosuppressant, cyclosporine A (CsA) is used to treat multiple autoimmune diseases, including non-autoimmune and autoimmune-mediated dry eye disease, rheumatoid arthritis and psoriasis. Despite its potency, CsA has poor solubility, poor bioavailability, and can cause serious adverse reactions such as nephrotoxicity and neurotoxicity. To overcome these limitations, we invented a new strategy to carry CsA by fusing its cognate human receptor, cyclophilin A (CypA), to a 73 kDa elastin-like polypeptide (ELP) termed A192 using recombinant protein expression. Derived from human tropoelastin, ELPs are characterized by the ability to phase separate above a temperature that is a function of variables including concentration, molecular weight, and hydrophobicity. The resultant fusion protein, termed CA192, which assembles into a dimeric species in solution, effectively binds and solubilizes CsA with a Kd of 189 nM, comparable to that of endogenous CypA with a Kd of 35.5 nM. The release profile of CsA from CA192 follows a one phase decay model with a half-life of 957.3 h without a burst release stage. Moreover, CA192-CsA inhibited IL-2 expression induced in Jurkat cells through the calcineurin-NFAT signaling pathway with an IC50 of 1.2 nM, comparable to that of free CsA with an IC50 of 0.5 nM. The intravenous pharmacokinetics of CA192 followed a two-compartment model with a mean residence time of 7.3 h. Subcutaneous administration revealed a bioavailability of 30% and a mean residence time of 15.9 h. When given subcutaneously for 2 weeks starting at 14 weeks in male non-obese diabetic (NOD) mice, a model of autoimmune dacryoadenitis used to study Sjögren's syndrome (SS), CA192-CsA (2.5 mg/kg, every other day) significantly (p = 0.014) increased tear production relative to CA192 alone. Moreover, CA192 delivery reduced indications of CsA nephrotoxicity relative to free CsA. CA192 represents a viable new approach to deliver this effective but nephrotoxic agent in a modality that preserves therapeutic efficacy but suppresses drug toxicity.

A PHF8 homolog in C. elegans promotes DNA repair via homologous recombination.

PHF8 is a JmjC domain-containing histone demethylase, defects in which are associated with X-linked mental retardation. In this study, we examined the roles of two PHF8 homologs, JMJD-1.1 and JMJD-1.2, in the model organism C. elegans in response to DNA damage. A deletion mutation in either of the genes led to hypersensitivity to interstrand DNA crosslinks (ICLs), while only mutation of jmjd-1.1 resulted in hypersensitivity to double-strand DNA breaks (DSBs). In response to ICLs, JMJD-1.1 did not affect the focus formation of FCD-2, a homolog of FANCD2, a key protein in the Fanconi anemia pathway. However, the dynamic behavior of RPA-1 and RAD-51 was affected by the mutation: the accumulations of both proteins at ICLs appeared normal, but their subsequent disappearance was retarded, suggesting that later steps of homologous recombination were defective. Similar changes in the dynamic behavior of RPA-1 and RAD-51 were seen in response to DSBs, supporting a role of JMJD-1.1 in homologous recombination. Such a role was also supported by our finding that the hypersensitivity of jmjd-1.1 worms to ICLs was rescued by knockdown of lig-4, a homolog of Ligase 4 active in nonhomologous end-joining. The hypersensitivity of jmjd-1.1 worms to ICLs was increased by rad-54 knockdown, suggesting that JMJD-1.1 acts in parallel with RAD-54 in modulating chromatin structure. Indeed, the level of histone H3 Lys9 tri-methylation, a marker of heterochromatin, was higher in jmjd-1.1 cells than in wild-type cells. We conclude that the histone demethylase JMJD-1.1 influences homologous recombination either by relaxing heterochromatin structure or by indirectly regulating the expression of multiple genes affecting DNA repair.